diff --git a/modules/openapi-generator/src/main/resources/ruby-client/base_object.mustache b/modules/openapi-generator/src/main/resources/ruby-client/base_object.mustache
index d752c497c42c..68767dfcfb7c 100644
--- a/modules/openapi-generator/src/main/resources/ruby-client/base_object.mustache
+++ b/modules/openapi-generator/src/main/resources/ruby-client/base_object.mustache
@@ -3,22 +3,21 @@
     # @return [Object] Returns the model itself
     def self.build_from_hash(attributes)
       return nil unless attributes.is_a?(Hash)
-      {{#parent}}
-      super(attributes)
-      {{/parent}}
       attributes = attributes.transform_keys(&:to_sym)
+      # include attributes inherited from allOf parents (the nearest declaration wins)
+      map = acceptable_attribute_map
       transformed_hash = {}
-      openapi_types.each_pair do |key, type|
-        if attributes.key?(attribute_map[key]) && attributes[attribute_map[key]].nil?
+      acceptable_openapi_types.each_pair do |key, type|
+        if attributes.key?(map[key]) && attributes[map[key]].nil?
           transformed_hash["#{key}"] = nil
         elsif type =~ /\AArray<(.*)>/i
           # check to ensure the input is an array given that the attribute
           # is documented as an array but the input is not
-          if attributes[attribute_map[key]].is_a?(Array)
-            transformed_hash["#{key}"] = attributes[attribute_map[key]].map { |v| _deserialize($1, v) }
+          if attributes[map[key]].is_a?(Array)
+            transformed_hash["#{key}"] = attributes[map[key]].map { |v| _deserialize($1, v) }
           end
-        elsif !attributes[attribute_map[key]].nil?
-          transformed_hash["#{key}"] = _deserialize(type, attributes[attribute_map[key]])
+        elsif !attributes[map[key]].nil?
+          transformed_hash["#{key}"] = _deserialize(type, attributes[map[key]])
         end
       end
       new(transformed_hash)
@@ -27,11 +26,12 @@
     # Returns the object in the form of hash
     # @return [Hash] Returns the object in the form of hash
     def to_hash
-      hash = {{^parent}}{}{{/parent}}{{#parent}}super{{/parent}}
-      self.class.attribute_map.each_pair do |attr, param|
+      hash = {}
+      # include attributes inherited from allOf parents (the nearest declaration wins)
+      self.class.acceptable_attribute_map.each_pair do |attr, param|
         value = self.send(attr)
         if value.nil?
-          is_nullable = self.class.openapi_nullable.include?(attr)
+          is_nullable = self.class.acceptable_openapi_nullable.include?(attr)
           next if !is_nullable || (is_nullable && !instance_variable_defined?(:"@#{attr}"))
         end
 
diff --git a/modules/openapi-generator/src/main/resources/ruby-client/partial_model_generic.mustache b/modules/openapi-generator/src/main/resources/ruby-client/partial_model_generic.mustache
index d5ef9e8ab420..05e8b0bf0c78 100644
--- a/modules/openapi-generator/src/main/resources/ruby-client/partial_model_generic.mustache
+++ b/modules/openapi-generator/src/main/resources/ruby-client/partial_model_generic.mustache
@@ -42,17 +42,17 @@
       }
     end
 
-    # Returns attribute mapping this model knows about{{#parent}}, including the ones defined in its parent(s){{/parent}}
+    # Returns attribute mapping this model knows about{{#parentModel}}, including the ones defined in its parent(s){{/parentModel}}
     def self.acceptable_attribute_map
-      {{^parent}}
+      {{^parentModel}}
       attribute_map
-      {{/parent}}
-      {{#parent}}
+      {{/parentModel}}
+      {{#parentModel}}
       superclass.acceptable_attribute_map.merge(attribute_map)
-      {{/parent}}
+      {{/parentModel}}
     end
 
-    # Returns all the JSON keys this model knows about{{#parent}}, including the ones defined in its parent(s){{/parent}}
+    # Returns all the JSON keys this model knows about{{#parentModel}}, including the ones defined in its parent(s){{/parentModel}}
     def self.acceptable_attributes
       acceptable_attribute_map.values
     end
@@ -77,6 +77,26 @@
       ])
     end
 
+    # Returns attribute type mapping{{#parentModel}}, including the ones defined in its parent(s){{/parentModel}}
+    def self.acceptable_openapi_types
+      {{^parentModel}}
+      openapi_types
+      {{/parentModel}}
+      {{#parentModel}}
+      superclass.acceptable_openapi_types.merge(openapi_types)
+      {{/parentModel}}
+    end
+
+    # Returns the nullable attributes{{#parentModel}}, including the ones defined in its parent(s) that it does not redeclare{{/parentModel}}
+    def self.acceptable_openapi_nullable
+      {{^parentModel}}
+      openapi_nullable
+      {{/parentModel}}
+      {{#parentModel}}
+      (superclass.acceptable_openapi_nullable - attribute_map.keys) | openapi_nullable
+      {{/parentModel}}
+    end
+
     {{#anyOf}}
     {{#-first}}
     # List of class defined in anyOf (OpenAPI v3)
@@ -127,11 +147,11 @@
         end
         h[k.to_sym] = v
       }
-      {{#parent}}
+      {{#parentModel}}
 
       # call parent's initialize
       super(attributes)
-      {{/parent}}
+      {{/parentModel}}
       {{#vars}}
 
       if attributes.key?(:'{{{name}}}')
diff --git a/modules/openapi-generator/src/test/java/org/openapitools/codegen/ruby/RubyClientCodegenTest.java b/modules/openapi-generator/src/test/java/org/openapitools/codegen/ruby/RubyClientCodegenTest.java
index f67bb6720788..a9914a9b8acf 100644
--- a/modules/openapi-generator/src/test/java/org/openapitools/codegen/ruby/RubyClientCodegenTest.java
+++ b/modules/openapi-generator/src/test/java/org/openapitools/codegen/ruby/RubyClientCodegenTest.java
@@ -26,12 +26,14 @@
 import org.openapitools.codegen.model.ModelMap;
 import org.openapitools.codegen.model.OperationMap;
 import org.openapitools.codegen.model.OperationsMap;
+import org.openapitools.codegen.utils.ModelUtils;
 import org.testng.Assert;
 import org.testng.annotations.Test;
 
 import java.io.File;
 import java.nio.charset.StandardCharsets;
 import java.nio.file.Files;
+import java.nio.file.Path;
 import java.util.*;
 import java.util.stream.Collectors;
 
@@ -799,4 +801,61 @@ public void testQueryParamJsonSerializationSetsQueryIsJsonMimeType() {
         assertTrue(op.queryParams.stream().allMatch(p -> p.queryIsJsonMimeType),
                 "All content:application/json query params should have queryIsJsonMimeType=true");
     }
+
+    @Test(description = "an allOf child's build_from_hash and to_hash include the attributes inherited from its parents")
+    public void testBuildFromHashMapsInheritedAttributes() throws Exception {
+        final File output = Files.createTempDirectory("test").toFile();
+        output.deleteOnExit();
+
+        final OpenAPI openAPI = TestUtils.parseFlattenSpec("src/test/resources/3_0/allOf_composition_discriminator.yaml");
+        CodegenConfig codegenConfig = new RubyClientCodegen();
+        codegenConfig.setOutputDir(output.getAbsolutePath());
+
+        ClientOptInput clientOptInput = new ClientOptInput().openAPI(openAPI).config(codegenConfig);
+        new DefaultGenerator().opts(clientOptInput).generate();
+
+        // Lizard < Reptile < Pet: types and nullability merge along the ancestry, the nearest declaration wins
+        Path lizard = new File(output, "lib/openapi_client/models/lizard.rb").toPath();
+        TestUtils.assertFileContains(lizard,
+                "superclass.acceptable_openapi_types.merge(openapi_types)",
+                "(superclass.acceptable_openapi_nullable - attribute_map.keys) | openapi_nullable");
+        // build_from_hash and to_hash use the merged maps
+        TestUtils.assertFileContains(lizard,
+                "acceptable_openapi_types.each_pair do |key, type|",
+                "self.class.acceptable_attribute_map.each_pair do |attr, param|",
+                "is_nullable = self.class.acceptable_openapi_nullable.include?(attr)");
+        // the super call that built and discarded a second instance is gone
+        TestUtils.assertFileNotContains(lizard, "super(attributes)\n      attributes = attributes.transform_keys(&:to_sym)");
+        // a root model has no parent to merge
+        TestUtils.assertFileNotContains(new File(output, "lib/openapi_client/models/pet.rb").toPath(), "superclass.acceptable_openapi_types");
+        // a generated parent still receives the initializer call
+        TestUtils.assertFileContains(lizard, "# call parent's initialize\n      super(attributes)");
+    }
+
+    @Test(description = "a model whose superclass is not a generated model (an alias to an array) does not delegate to it")
+    public void testAliasModelDoesNotDelegateToItsBuiltInSuperclass() throws Exception {
+        final File output = Files.createTempDirectory("test").toFile();
+        output.deleteOnExit();
+
+        final OpenAPI openAPI = TestUtils.parseFlattenSpec("src/test/resources/3_0/features/generate-alias-as-model.yaml");
+        CodegenConfig codegenConfig = new RubyClientCodegen();
+        codegenConfig.setOutputDir(output.getAbsolutePath());
+
+        ClientOptInput clientOptInput = new ClientOptInput().openAPI(openAPI).config(codegenConfig);
+        ModelUtils.setGenerateAliasAsModel(true);
+        try {
+            new DefaultGenerator().opts(clientOptInput).generate();
+        } finally {
+            ModelUtils.setGenerateAliasAsModel(false);
+        }
+
+        // ArrayAlias < Array: Array has none of the helpers, so each one is its own base case
+        Path arrayAlias = new File(output, "lib/openapi_client/models/array_alias.rb").toPath();
+        TestUtils.assertFileContains(arrayAlias,
+                "class ArrayAlias < Array",
+                "def self.acceptable_attribute_map\n      attribute_map\n    end",
+                "def self.acceptable_openapi_types\n      openapi_types\n    end",
+                "def self.acceptable_openapi_nullable\n      openapi_nullable\n    end");
+        TestUtils.assertFileNotContains(arrayAlias, "superclass.", "super(attributes)");
+    }
 }
diff --git a/samples/client/echo_api/ruby-faraday/lib/openapi_client/models/bird.rb b/samples/client/echo_api/ruby-faraday/lib/openapi_client/models/bird.rb
index 791ff7830e90..9f03a6daeca5 100644
--- a/samples/client/echo_api/ruby-faraday/lib/openapi_client/models/bird.rb
+++ b/samples/client/echo_api/ruby-faraday/lib/openapi_client/models/bird.rb
@@ -51,6 +51,16 @@ def self.openapi_nullable
       ])
     end
 
+    # Returns attribute type mapping
+    def self.acceptable_openapi_types
+      openapi_types
+    end
+
+    # Returns the nullable attributes
+    def self.acceptable_openapi_nullable
+      openapi_nullable
+    end
+
     # Initializes the object
     # @param [Hash] attributes Model attributes in the form of hash
     def initialize(attributes = {})
@@ -118,18 +128,20 @@ def hash
     def self.build_from_hash(attributes)
       return nil unless attributes.is_a?(Hash)
       attributes = attributes.transform_keys(&:to_sym)
+      # include attributes inherited from allOf parents (the nearest declaration wins)
+      map = acceptable_attribute_map
       transformed_hash = {}
-      openapi_types.each_pair do |key, type|
-        if attributes.key?(attribute_map[key]) && attributes[attribute_map[key]].nil?
+      acceptable_openapi_types.each_pair do |key, type|
+        if attributes.key?(map[key]) && attributes[map[key]].nil?
           transformed_hash["#{key}"] = nil
         elsif type =~ /\AArray<(.*)>/i
           # check to ensure the input is an array given that the attribute
           # is documented as an array but the input is not
-          if attributes[attribute_map[key]].is_a?(Array)
-            transformed_hash["#{key}"] = attributes[attribute_map[key]].map { |v| _deserialize($1, v) }
+          if attributes[map[key]].is_a?(Array)
+            transformed_hash["#{key}"] = attributes[map[key]].map { |v| _deserialize($1, v) }
           end
-        elsif !attributes[attribute_map[key]].nil?
-          transformed_hash["#{key}"] = _deserialize(type, attributes[attribute_map[key]])
+        elsif !attributes[map[key]].nil?
+          transformed_hash["#{key}"] = _deserialize(type, attributes[map[key]])
         end
       end
       new(transformed_hash)
@@ -139,10 +151,11 @@ def self.build_from_hash(attributes)
     # @return [Hash] Returns the object in the form of hash
     def to_hash
       hash = {}
-      self.class.attribute_map.each_pair do |attr, param|
+      # include attributes inherited from allOf parents (the nearest declaration wins)
+      self.class.acceptable_attribute_map.each_pair do |attr, param|
         value = self.send(attr)
         if value.nil?
-          is_nullable = self.class.openapi_nullable.include?(attr)
+          is_nullable = self.class.acceptable_openapi_nullable.include?(attr)
           next if !is_nullable || (is_nullable && !instance_variable_defined?(:"@#{attr}"))
         end
 
diff --git a/samples/client/echo_api/ruby-faraday/lib/openapi_client/models/category.rb b/samples/client/echo_api/ruby-faraday/lib/openapi_client/models/category.rb
index 2ae2f25e7bb6..a9e3fae3e988 100644
--- a/samples/client/echo_api/ruby-faraday/lib/openapi_client/models/category.rb
+++ b/samples/client/echo_api/ruby-faraday/lib/openapi_client/models/category.rb
@@ -51,6 +51,16 @@ def self.openapi_nullable
       ])
     end
 
+    # Returns attribute type mapping
+    def self.acceptable_openapi_types
+      openapi_types
+    end
+
+    # Returns the nullable attributes
+    def self.acceptable_openapi_nullable
+      openapi_nullable
+    end
+
     # Initializes the object
     # @param [Hash] attributes Model attributes in the form of hash
     def initialize(attributes = {})
@@ -118,18 +128,20 @@ def hash
     def self.build_from_hash(attributes)
       return nil unless attributes.is_a?(Hash)
       attributes = attributes.transform_keys(&:to_sym)
+      # include attributes inherited from allOf parents (the nearest declaration wins)
+      map = acceptable_attribute_map
       transformed_hash = {}
-      openapi_types.each_pair do |key, type|
-        if attributes.key?(attribute_map[key]) && attributes[attribute_map[key]].nil?
+      acceptable_openapi_types.each_pair do |key, type|
+        if attributes.key?(map[key]) && attributes[map[key]].nil?
           transformed_hash["#{key}"] = nil
         elsif type =~ /\AArray<(.*)>/i
           # check to ensure the input is an array given that the attribute
           # is documented as an array but the input is not
-          if attributes[attribute_map[key]].is_a?(Array)
-            transformed_hash["#{key}"] = attributes[attribute_map[key]].map { |v| _deserialize($1, v) }
+          if attributes[map[key]].is_a?(Array)
+            transformed_hash["#{key}"] = attributes[map[key]].map { |v| _deserialize($1, v) }
           end
-        elsif !attributes[attribute_map[key]].nil?
-          transformed_hash["#{key}"] = _deserialize(type, attributes[attribute_map[key]])
+        elsif !attributes[map[key]].nil?
+          transformed_hash["#{key}"] = _deserialize(type, attributes[map[key]])
         end
       end
       new(transformed_hash)
@@ -139,10 +151,11 @@ def self.build_from_hash(attributes)
     # @return [Hash] Returns the object in the form of hash
     def to_hash
       hash = {}
-      self.class.attribute_map.each_pair do |attr, param|
+      # include attributes inherited from allOf parents (the nearest declaration wins)
+      self.class.acceptable_attribute_map.each_pair do |attr, param|
         value = self.send(attr)
         if value.nil?
-          is_nullable = self.class.openapi_nullable.include?(attr)
+          is_nullable = self.class.acceptable_openapi_nullable.include?(attr)
           next if !is_nullable || (is_nullable && !instance_variable_defined?(:"@#{attr}"))
         end
 
diff --git a/samples/client/echo_api/ruby-faraday/lib/openapi_client/models/data_query.rb b/samples/client/echo_api/ruby-faraday/lib/openapi_client/models/data_query.rb
index 1a31b4d3e83f..0575446c351f 100644
--- a/samples/client/echo_api/ruby-faraday/lib/openapi_client/models/data_query.rb
+++ b/samples/client/echo_api/ruby-faraday/lib/openapi_client/models/data_query.rb
@@ -80,6 +80,16 @@ def self.openapi_nullable
       ])
     end
 
+    # Returns attribute type mapping, including the ones defined in its parent(s)
+    def self.acceptable_openapi_types
+      superclass.acceptable_openapi_types.merge(openapi_types)
+    end
+
+    # Returns the nullable attributes, including the ones defined in its parent(s) that it does not redeclare
+    def self.acceptable_openapi_nullable
+      (superclass.acceptable_openapi_nullable - attribute_map.keys) | openapi_nullable
+    end
+
     # List of class defined in allOf (OpenAPI v3)
     def self.openapi_all_of
       [
@@ -161,20 +171,21 @@ def hash
     # @return [Object] Returns the model itself
     def self.build_from_hash(attributes)
       return nil unless attributes.is_a?(Hash)
-      super(attributes)
       attributes = attributes.transform_keys(&:to_sym)
+      # include attributes inherited from allOf parents (the nearest declaration wins)
+      map = acceptable_attribute_map
       transformed_hash = {}
-      openapi_types.each_pair do |key, type|
-        if attributes.key?(attribute_map[key]) && attributes[attribute_map[key]].nil?
+      acceptable_openapi_types.each_pair do |key, type|
+        if attributes.key?(map[key]) && attributes[map[key]].nil?
           transformed_hash["#{key}"] = nil
         elsif type =~ /\AArray<(.*)>/i
           # check to ensure the input is an array given that the attribute
           # is documented as an array but the input is not
-          if attributes[attribute_map[key]].is_a?(Array)
-            transformed_hash["#{key}"] = attributes[attribute_map[key]].map { |v| _deserialize($1, v) }
+          if attributes[map[key]].is_a?(Array)
+            transformed_hash["#{key}"] = attributes[map[key]].map { |v| _deserialize($1, v) }
           end
-        elsif !attributes[attribute_map[key]].nil?
-          transformed_hash["#{key}"] = _deserialize(type, attributes[attribute_map[key]])
+        elsif !attributes[map[key]].nil?
+          transformed_hash["#{key}"] = _deserialize(type, attributes[map[key]])
         end
       end
       new(transformed_hash)
@@ -183,11 +194,12 @@ def self.build_from_hash(attributes)
     # Returns the object in the form of hash
     # @return [Hash] Returns the object in the form of hash
     def to_hash
-      hash = super
-      self.class.attribute_map.each_pair do |attr, param|
+      hash = {}
+      # include attributes inherited from allOf parents (the nearest declaration wins)
+      self.class.acceptable_attribute_map.each_pair do |attr, param|
         value = self.send(attr)
         if value.nil?
-          is_nullable = self.class.openapi_nullable.include?(attr)
+          is_nullable = self.class.acceptable_openapi_nullable.include?(attr)
           next if !is_nullable || (is_nullable && !instance_variable_defined?(:"@#{attr}"))
         end
 
diff --git a/samples/client/echo_api/ruby-faraday/lib/openapi_client/models/default_value.rb b/samples/client/echo_api/ruby-faraday/lib/openapi_client/models/default_value.rb
index 9dbb442bb860..451707d0eeb9 100644
--- a/samples/client/echo_api/ruby-faraday/lib/openapi_client/models/default_value.rb
+++ b/samples/client/echo_api/ruby-faraday/lib/openapi_client/models/default_value.rb
@@ -101,6 +101,16 @@ def self.openapi_nullable
       ])
     end
 
+    # Returns attribute type mapping
+    def self.acceptable_openapi_types
+      openapi_types
+    end
+
+    # Returns the nullable attributes
+    def self.acceptable_openapi_nullable
+      openapi_nullable
+    end
+
     # Initializes the object
     # @param [Hash] attributes Model attributes in the form of hash
     def initialize(attributes = {})
@@ -212,18 +222,20 @@ def hash
     def self.build_from_hash(attributes)
       return nil unless attributes.is_a?(Hash)
       attributes = attributes.transform_keys(&:to_sym)
+      # include attributes inherited from allOf parents (the nearest declaration wins)
+      map = acceptable_attribute_map
       transformed_hash = {}
-      openapi_types.each_pair do |key, type|
-        if attributes.key?(attribute_map[key]) && attributes[attribute_map[key]].nil?
+      acceptable_openapi_types.each_pair do |key, type|
+        if attributes.key?(map[key]) && attributes[map[key]].nil?
           transformed_hash["#{key}"] = nil
         elsif type =~ /\AArray<(.*)>/i
           # check to ensure the input is an array given that the attribute
           # is documented as an array but the input is not
-          if attributes[attribute_map[key]].is_a?(Array)
-            transformed_hash["#{key}"] = attributes[attribute_map[key]].map { |v| _deserialize($1, v) }
+          if attributes[map[key]].is_a?(Array)
+            transformed_hash["#{key}"] = attributes[map[key]].map { |v| _deserialize($1, v) }
           end
-        elsif !attributes[attribute_map[key]].nil?
-          transformed_hash["#{key}"] = _deserialize(type, attributes[attribute_map[key]])
+        elsif !attributes[map[key]].nil?
+          transformed_hash["#{key}"] = _deserialize(type, attributes[map[key]])
         end
       end
       new(transformed_hash)
@@ -233,10 +245,11 @@ def self.build_from_hash(attributes)
     # @return [Hash] Returns the object in the form of hash
     def to_hash
       hash = {}
-      self.class.attribute_map.each_pair do |attr, param|
+      # include attributes inherited from allOf parents (the nearest declaration wins)
+      self.class.acceptable_attribute_map.each_pair do |attr, param|
         value = self.send(attr)
         if value.nil?
-          is_nullable = self.class.openapi_nullable.include?(attr)
+          is_nullable = self.class.acceptable_openapi_nullable.include?(attr)
           next if !is_nullable || (is_nullable && !instance_variable_defined?(:"@#{attr}"))
         end
 
diff --git a/samples/client/echo_api/ruby-faraday/lib/openapi_client/models/number_properties_only.rb b/samples/client/echo_api/ruby-faraday/lib/openapi_client/models/number_properties_only.rb
index 46b63c582964..20ace6a8baad 100644
--- a/samples/client/echo_api/ruby-faraday/lib/openapi_client/models/number_properties_only.rb
+++ b/samples/client/echo_api/ruby-faraday/lib/openapi_client/models/number_properties_only.rb
@@ -55,6 +55,16 @@ def self.openapi_nullable
       ])
     end
 
+    # Returns attribute type mapping
+    def self.acceptable_openapi_types
+      openapi_types
+    end
+
+    # Returns the nullable attributes
+    def self.acceptable_openapi_nullable
+      openapi_nullable
+    end
+
     # Initializes the object
     # @param [Hash] attributes Model attributes in the form of hash
     def initialize(attributes = {})
@@ -155,18 +165,20 @@ def hash
     def self.build_from_hash(attributes)
       return nil unless attributes.is_a?(Hash)
       attributes = attributes.transform_keys(&:to_sym)
+      # include attributes inherited from allOf parents (the nearest declaration wins)
+      map = acceptable_attribute_map
       transformed_hash = {}
-      openapi_types.each_pair do |key, type|
-        if attributes.key?(attribute_map[key]) && attributes[attribute_map[key]].nil?
+      acceptable_openapi_types.each_pair do |key, type|
+        if attributes.key?(map[key]) && attributes[map[key]].nil?
           transformed_hash["#{key}"] = nil
         elsif type =~ /\AArray<(.*)>/i
           # check to ensure the input is an array given that the attribute
           # is documented as an array but the input is not
-          if attributes[attribute_map[key]].is_a?(Array)
-            transformed_hash["#{key}"] = attributes[attribute_map[key]].map { |v| _deserialize($1, v) }
+          if attributes[map[key]].is_a?(Array)
+            transformed_hash["#{key}"] = attributes[map[key]].map { |v| _deserialize($1, v) }
           end
-        elsif !attributes[attribute_map[key]].nil?
-          transformed_hash["#{key}"] = _deserialize(type, attributes[attribute_map[key]])
+        elsif !attributes[map[key]].nil?
+          transformed_hash["#{key}"] = _deserialize(type, attributes[map[key]])
         end
       end
       new(transformed_hash)
@@ -176,10 +188,11 @@ def self.build_from_hash(attributes)
     # @return [Hash] Returns the object in the form of hash
     def to_hash
       hash = {}
-      self.class.attribute_map.each_pair do |attr, param|
+      # include attributes inherited from allOf parents (the nearest declaration wins)
+      self.class.acceptable_attribute_map.each_pair do |attr, param|
         value = self.send(attr)
         if value.nil?
-          is_nullable = self.class.openapi_nullable.include?(attr)
+          is_nullable = self.class.acceptable_openapi_nullable.include?(attr)
           next if !is_nullable || (is_nullable && !instance_variable_defined?(:"@#{attr}"))
         end
 
diff --git a/samples/client/echo_api/ruby-faraday/lib/openapi_client/models/pet.rb b/samples/client/echo_api/ruby-faraday/lib/openapi_client/models/pet.rb
index d1a334676d56..c756e2ce6b41 100644
--- a/samples/client/echo_api/ruby-faraday/lib/openapi_client/models/pet.rb
+++ b/samples/client/echo_api/ruby-faraday/lib/openapi_client/models/pet.rb
@@ -90,6 +90,16 @@ def self.openapi_nullable
       ])
     end
 
+    # Returns attribute type mapping
+    def self.acceptable_openapi_types
+      openapi_types
+    end
+
+    # Returns the nullable attributes
+    def self.acceptable_openapi_nullable
+      openapi_nullable
+    end
+
     # Initializes the object
     # @param [Hash] attributes Model attributes in the form of hash
     def initialize(attributes = {})
@@ -227,18 +237,20 @@ def hash
     def self.build_from_hash(attributes)
       return nil unless attributes.is_a?(Hash)
       attributes = attributes.transform_keys(&:to_sym)
+      # include attributes inherited from allOf parents (the nearest declaration wins)
+      map = acceptable_attribute_map
       transformed_hash = {}
-      openapi_types.each_pair do |key, type|
-        if attributes.key?(attribute_map[key]) && attributes[attribute_map[key]].nil?
+      acceptable_openapi_types.each_pair do |key, type|
+        if attributes.key?(map[key]) && attributes[map[key]].nil?
           transformed_hash["#{key}"] = nil
         elsif type =~ /\AArray<(.*)>/i
           # check to ensure the input is an array given that the attribute
           # is documented as an array but the input is not
-          if attributes[attribute_map[key]].is_a?(Array)
-            transformed_hash["#{key}"] = attributes[attribute_map[key]].map { |v| _deserialize($1, v) }
+          if attributes[map[key]].is_a?(Array)
+            transformed_hash["#{key}"] = attributes[map[key]].map { |v| _deserialize($1, v) }
           end
-        elsif !attributes[attribute_map[key]].nil?
-          transformed_hash["#{key}"] = _deserialize(type, attributes[attribute_map[key]])
+        elsif !attributes[map[key]].nil?
+          transformed_hash["#{key}"] = _deserialize(type, attributes[map[key]])
         end
       end
       new(transformed_hash)
@@ -248,10 +260,11 @@ def self.build_from_hash(attributes)
     # @return [Hash] Returns the object in the form of hash
     def to_hash
       hash = {}
-      self.class.attribute_map.each_pair do |attr, param|
+      # include attributes inherited from allOf parents (the nearest declaration wins)
+      self.class.acceptable_attribute_map.each_pair do |attr, param|
         value = self.send(attr)
         if value.nil?
-          is_nullable = self.class.openapi_nullable.include?(attr)
+          is_nullable = self.class.acceptable_openapi_nullable.include?(attr)
           next if !is_nullable || (is_nullable && !instance_variable_defined?(:"@#{attr}"))
         end
 
diff --git a/samples/client/echo_api/ruby-faraday/lib/openapi_client/models/query.rb b/samples/client/echo_api/ruby-faraday/lib/openapi_client/models/query.rb
index 7598d312f1dd..1e1b31de201b 100644
--- a/samples/client/echo_api/ruby-faraday/lib/openapi_client/models/query.rb
+++ b/samples/client/echo_api/ruby-faraday/lib/openapi_client/models/query.rb
@@ -74,6 +74,16 @@ def self.openapi_nullable
       ])
     end
 
+    # Returns attribute type mapping
+    def self.acceptable_openapi_types
+      openapi_types
+    end
+
+    # Returns the nullable attributes
+    def self.acceptable_openapi_nullable
+      openapi_nullable
+    end
+
     # Initializes the object
     # @param [Hash] attributes Model attributes in the form of hash
     def initialize(attributes = {})
@@ -143,18 +153,20 @@ def hash
     def self.build_from_hash(attributes)
       return nil unless attributes.is_a?(Hash)
       attributes = attributes.transform_keys(&:to_sym)
+      # include attributes inherited from allOf parents (the nearest declaration wins)
+      map = acceptable_attribute_map
       transformed_hash = {}
-      openapi_types.each_pair do |key, type|
-        if attributes.key?(attribute_map[key]) && attributes[attribute_map[key]].nil?
+      acceptable_openapi_types.each_pair do |key, type|
+        if attributes.key?(map[key]) && attributes[map[key]].nil?
           transformed_hash["#{key}"] = nil
         elsif type =~ /\AArray<(.*)>/i
           # check to ensure the input is an array given that the attribute
           # is documented as an array but the input is not
-          if attributes[attribute_map[key]].is_a?(Array)
-            transformed_hash["#{key}"] = attributes[attribute_map[key]].map { |v| _deserialize($1, v) }
+          if attributes[map[key]].is_a?(Array)
+            transformed_hash["#{key}"] = attributes[map[key]].map { |v| _deserialize($1, v) }
           end
-        elsif !attributes[attribute_map[key]].nil?
-          transformed_hash["#{key}"] = _deserialize(type, attributes[attribute_map[key]])
+        elsif !attributes[map[key]].nil?
+          transformed_hash["#{key}"] = _deserialize(type, attributes[map[key]])
         end
       end
       new(transformed_hash)
@@ -164,10 +176,11 @@ def self.build_from_hash(attributes)
     # @return [Hash] Returns the object in the form of hash
     def to_hash
       hash = {}
-      self.class.attribute_map.each_pair do |attr, param|
+      # include attributes inherited from allOf parents (the nearest declaration wins)
+      self.class.acceptable_attribute_map.each_pair do |attr, param|
         value = self.send(attr)
         if value.nil?
-          is_nullable = self.class.openapi_nullable.include?(attr)
+          is_nullable = self.class.acceptable_openapi_nullable.include?(attr)
           next if !is_nullable || (is_nullable && !instance_variable_defined?(:"@#{attr}"))
         end
 
diff --git a/samples/client/echo_api/ruby-faraday/lib/openapi_client/models/tag.rb b/samples/client/echo_api/ruby-faraday/lib/openapi_client/models/tag.rb
index d087eafa1516..e0d61143d2f0 100644
--- a/samples/client/echo_api/ruby-faraday/lib/openapi_client/models/tag.rb
+++ b/samples/client/echo_api/ruby-faraday/lib/openapi_client/models/tag.rb
@@ -51,6 +51,16 @@ def self.openapi_nullable
       ])
     end
 
+    # Returns attribute type mapping
+    def self.acceptable_openapi_types
+      openapi_types
+    end
+
+    # Returns the nullable attributes
+    def self.acceptable_openapi_nullable
+      openapi_nullable
+    end
+
     # Initializes the object
     # @param [Hash] attributes Model attributes in the form of hash
     def initialize(attributes = {})
@@ -118,18 +128,20 @@ def hash
     def self.build_from_hash(attributes)
       return nil unless attributes.is_a?(Hash)
       attributes = attributes.transform_keys(&:to_sym)
+      # include attributes inherited from allOf parents (the nearest declaration wins)
+      map = acceptable_attribute_map
       transformed_hash = {}
-      openapi_types.each_pair do |key, type|
-        if attributes.key?(attribute_map[key]) && attributes[attribute_map[key]].nil?
+      acceptable_openapi_types.each_pair do |key, type|
+        if attributes.key?(map[key]) && attributes[map[key]].nil?
           transformed_hash["#{key}"] = nil
         elsif type =~ /\AArray<(.*)>/i
           # check to ensure the input is an array given that the attribute
           # is documented as an array but the input is not
-          if attributes[attribute_map[key]].is_a?(Array)
-            transformed_hash["#{key}"] = attributes[attribute_map[key]].map { |v| _deserialize($1, v) }
+          if attributes[map[key]].is_a?(Array)
+            transformed_hash["#{key}"] = attributes[map[key]].map { |v| _deserialize($1, v) }
           end
-        elsif !attributes[attribute_map[key]].nil?
-          transformed_hash["#{key}"] = _deserialize(type, attributes[attribute_map[key]])
+        elsif !attributes[map[key]].nil?
+          transformed_hash["#{key}"] = _deserialize(type, attributes[map[key]])
         end
       end
       new(transformed_hash)
@@ -139,10 +151,11 @@ def self.build_from_hash(attributes)
     # @return [Hash] Returns the object in the form of hash
     def to_hash
       hash = {}
-      self.class.attribute_map.each_pair do |attr, param|
+      # include attributes inherited from allOf parents (the nearest declaration wins)
+      self.class.acceptable_attribute_map.each_pair do |attr, param|
         value = self.send(attr)
         if value.nil?
-          is_nullable = self.class.openapi_nullable.include?(attr)
+          is_nullable = self.class.acceptable_openapi_nullable.include?(attr)
           next if !is_nullable || (is_nullable && !instance_variable_defined?(:"@#{attr}"))
         end
 
diff --git a/samples/client/echo_api/ruby-faraday/lib/openapi_client/models/test_form_object_multipart_request_marker.rb b/samples/client/echo_api/ruby-faraday/lib/openapi_client/models/test_form_object_multipart_request_marker.rb
index 1b00e10e7dc3..6b33437e3258 100644
--- a/samples/client/echo_api/ruby-faraday/lib/openapi_client/models/test_form_object_multipart_request_marker.rb
+++ b/samples/client/echo_api/ruby-faraday/lib/openapi_client/models/test_form_object_multipart_request_marker.rb
@@ -47,6 +47,16 @@ def self.openapi_nullable
       ])
     end
 
+    # Returns attribute type mapping
+    def self.acceptable_openapi_types
+      openapi_types
+    end
+
+    # Returns the nullable attributes
+    def self.acceptable_openapi_nullable
+      openapi_nullable
+    end
+
     # Initializes the object
     # @param [Hash] attributes Model attributes in the form of hash
     def initialize(attributes = {})
@@ -109,18 +119,20 @@ def hash
     def self.build_from_hash(attributes)
       return nil unless attributes.is_a?(Hash)
       attributes = attributes.transform_keys(&:to_sym)
+      # include attributes inherited from allOf parents (the nearest declaration wins)
+      map = acceptable_attribute_map
       transformed_hash = {}
-      openapi_types.each_pair do |key, type|
-        if attributes.key?(attribute_map[key]) && attributes[attribute_map[key]].nil?
+      acceptable_openapi_types.each_pair do |key, type|
+        if attributes.key?(map[key]) && attributes[map[key]].nil?
           transformed_hash["#{key}"] = nil
         elsif type =~ /\AArray<(.*)>/i
           # check to ensure the input is an array given that the attribute
           # is documented as an array but the input is not
-          if attributes[attribute_map[key]].is_a?(Array)
-            transformed_hash["#{key}"] = attributes[attribute_map[key]].map { |v| _deserialize($1, v) }
+          if attributes[map[key]].is_a?(Array)
+            transformed_hash["#{key}"] = attributes[map[key]].map { |v| _deserialize($1, v) }
           end
-        elsif !attributes[attribute_map[key]].nil?
-          transformed_hash["#{key}"] = _deserialize(type, attributes[attribute_map[key]])
+        elsif !attributes[map[key]].nil?
+          transformed_hash["#{key}"] = _deserialize(type, attributes[map[key]])
         end
       end
       new(transformed_hash)
@@ -130,10 +142,11 @@ def self.build_from_hash(attributes)
     # @return [Hash] Returns the object in the form of hash
     def to_hash
       hash = {}
-      self.class.attribute_map.each_pair do |attr, param|
+      # include attributes inherited from allOf parents (the nearest declaration wins)
+      self.class.acceptable_attribute_map.each_pair do |attr, param|
         value = self.send(attr)
         if value.nil?
-          is_nullable = self.class.openapi_nullable.include?(attr)
+          is_nullable = self.class.acceptable_openapi_nullable.include?(attr)
           next if !is_nullable || (is_nullable && !instance_variable_defined?(:"@#{attr}"))
         end
 
diff --git a/samples/client/echo_api/ruby-faraday/lib/openapi_client/models/test_query_style_deep_object_explode_true_object_all_of_query_object_parameter.rb b/samples/client/echo_api/ruby-faraday/lib/openapi_client/models/test_query_style_deep_object_explode_true_object_all_of_query_object_parameter.rb
index 02afae09bce2..04a9bd521165 100644
--- a/samples/client/echo_api/ruby-faraday/lib/openapi_client/models/test_query_style_deep_object_explode_true_object_all_of_query_object_parameter.rb
+++ b/samples/client/echo_api/ruby-faraday/lib/openapi_client/models/test_query_style_deep_object_explode_true_object_all_of_query_object_parameter.rb
@@ -59,6 +59,16 @@ def self.openapi_nullable
       ])
     end
 
+    # Returns attribute type mapping
+    def self.acceptable_openapi_types
+      openapi_types
+    end
+
+    # Returns the nullable attributes
+    def self.acceptable_openapi_nullable
+      openapi_nullable
+    end
+
     # List of class defined in allOf (OpenAPI v3)
     def self.openapi_all_of
       [
@@ -144,18 +154,20 @@ def hash
     def self.build_from_hash(attributes)
       return nil unless attributes.is_a?(Hash)
       attributes = attributes.transform_keys(&:to_sym)
+      # include attributes inherited from allOf parents (the nearest declaration wins)
+      map = acceptable_attribute_map
       transformed_hash = {}
-      openapi_types.each_pair do |key, type|
-        if attributes.key?(attribute_map[key]) && attributes[attribute_map[key]].nil?
+      acceptable_openapi_types.each_pair do |key, type|
+        if attributes.key?(map[key]) && attributes[map[key]].nil?
           transformed_hash["#{key}"] = nil
         elsif type =~ /\AArray<(.*)>/i
           # check to ensure the input is an array given that the attribute
           # is documented as an array but the input is not
-          if attributes[attribute_map[key]].is_a?(Array)
-            transformed_hash["#{key}"] = attributes[attribute_map[key]].map { |v| _deserialize($1, v) }
+          if attributes[map[key]].is_a?(Array)
+            transformed_hash["#{key}"] = attributes[map[key]].map { |v| _deserialize($1, v) }
           end
-        elsif !attributes[attribute_map[key]].nil?
-          transformed_hash["#{key}"] = _deserialize(type, attributes[attribute_map[key]])
+        elsif !attributes[map[key]].nil?
+          transformed_hash["#{key}"] = _deserialize(type, attributes[map[key]])
         end
       end
       new(transformed_hash)
@@ -165,10 +177,11 @@ def self.build_from_hash(attributes)
     # @return [Hash] Returns the object in the form of hash
     def to_hash
       hash = {}
-      self.class.attribute_map.each_pair do |attr, param|
+      # include attributes inherited from allOf parents (the nearest declaration wins)
+      self.class.acceptable_attribute_map.each_pair do |attr, param|
         value = self.send(attr)
         if value.nil?
-          is_nullable = self.class.openapi_nullable.include?(attr)
+          is_nullable = self.class.acceptable_openapi_nullable.include?(attr)
           next if !is_nullable || (is_nullable && !instance_variable_defined?(:"@#{attr}"))
         end
 
diff --git a/samples/client/echo_api/ruby-faraday/lib/openapi_client/models/test_query_style_form_explode_true_array_string_query_object_parameter.rb b/samples/client/echo_api/ruby-faraday/lib/openapi_client/models/test_query_style_form_explode_true_array_string_query_object_parameter.rb
index fa9520a4f16c..3c67a8e0f2a9 100644
--- a/samples/client/echo_api/ruby-faraday/lib/openapi_client/models/test_query_style_form_explode_true_array_string_query_object_parameter.rb
+++ b/samples/client/echo_api/ruby-faraday/lib/openapi_client/models/test_query_style_form_explode_true_array_string_query_object_parameter.rb
@@ -47,6 +47,16 @@ def self.openapi_nullable
       ])
     end
 
+    # Returns attribute type mapping
+    def self.acceptable_openapi_types
+      openapi_types
+    end
+
+    # Returns the nullable attributes
+    def self.acceptable_openapi_nullable
+      openapi_nullable
+    end
+
     # Initializes the object
     # @param [Hash] attributes Model attributes in the form of hash
     def initialize(attributes = {})
@@ -111,18 +121,20 @@ def hash
     def self.build_from_hash(attributes)
       return nil unless attributes.is_a?(Hash)
       attributes = attributes.transform_keys(&:to_sym)
+      # include attributes inherited from allOf parents (the nearest declaration wins)
+      map = acceptable_attribute_map
       transformed_hash = {}
-      openapi_types.each_pair do |key, type|
-        if attributes.key?(attribute_map[key]) && attributes[attribute_map[key]].nil?
+      acceptable_openapi_types.each_pair do |key, type|
+        if attributes.key?(map[key]) && attributes[map[key]].nil?
           transformed_hash["#{key}"] = nil
         elsif type =~ /\AArray<(.*)>/i
           # check to ensure the input is an array given that the attribute
           # is documented as an array but the input is not
-          if attributes[attribute_map[key]].is_a?(Array)
-            transformed_hash["#{key}"] = attributes[attribute_map[key]].map { |v| _deserialize($1, v) }
+          if attributes[map[key]].is_a?(Array)
+            transformed_hash["#{key}"] = attributes[map[key]].map { |v| _deserialize($1, v) }
           end
-        elsif !attributes[attribute_map[key]].nil?
-          transformed_hash["#{key}"] = _deserialize(type, attributes[attribute_map[key]])
+        elsif !attributes[map[key]].nil?
+          transformed_hash["#{key}"] = _deserialize(type, attributes[map[key]])
         end
       end
       new(transformed_hash)
@@ -132,10 +144,11 @@ def self.build_from_hash(attributes)
     # @return [Hash] Returns the object in the form of hash
     def to_hash
       hash = {}
-      self.class.attribute_map.each_pair do |attr, param|
+      # include attributes inherited from allOf parents (the nearest declaration wins)
+      self.class.acceptable_attribute_map.each_pair do |attr, param|
         value = self.send(attr)
         if value.nil?
-          is_nullable = self.class.openapi_nullable.include?(attr)
+          is_nullable = self.class.acceptable_openapi_nullable.include?(attr)
           next if !is_nullable || (is_nullable && !instance_variable_defined?(:"@#{attr}"))
         end
 
diff --git a/samples/client/echo_api/ruby-httpx/lib/openapi_client/models/bird.rb b/samples/client/echo_api/ruby-httpx/lib/openapi_client/models/bird.rb
index 791ff7830e90..9f03a6daeca5 100644
--- a/samples/client/echo_api/ruby-httpx/lib/openapi_client/models/bird.rb
+++ b/samples/client/echo_api/ruby-httpx/lib/openapi_client/models/bird.rb
@@ -51,6 +51,16 @@ def self.openapi_nullable
       ])
     end
 
+    # Returns attribute type mapping
+    def self.acceptable_openapi_types
+      openapi_types
+    end
+
+    # Returns the nullable attributes
+    def self.acceptable_openapi_nullable
+      openapi_nullable
+    end
+
     # Initializes the object
     # @param [Hash] attributes Model attributes in the form of hash
     def initialize(attributes = {})
@@ -118,18 +128,20 @@ def hash
     def self.build_from_hash(attributes)
       return nil unless attributes.is_a?(Hash)
       attributes = attributes.transform_keys(&:to_sym)
+      # include attributes inherited from allOf parents (the nearest declaration wins)
+      map = acceptable_attribute_map
       transformed_hash = {}
-      openapi_types.each_pair do |key, type|
-        if attributes.key?(attribute_map[key]) && attributes[attribute_map[key]].nil?
+      acceptable_openapi_types.each_pair do |key, type|
+        if attributes.key?(map[key]) && attributes[map[key]].nil?
           transformed_hash["#{key}"] = nil
         elsif type =~ /\AArray<(.*)>/i
           # check to ensure the input is an array given that the attribute
           # is documented as an array but the input is not
-          if attributes[attribute_map[key]].is_a?(Array)
-            transformed_hash["#{key}"] = attributes[attribute_map[key]].map { |v| _deserialize($1, v) }
+          if attributes[map[key]].is_a?(Array)
+            transformed_hash["#{key}"] = attributes[map[key]].map { |v| _deserialize($1, v) }
           end
-        elsif !attributes[attribute_map[key]].nil?
-          transformed_hash["#{key}"] = _deserialize(type, attributes[attribute_map[key]])
+        elsif !attributes[map[key]].nil?
+          transformed_hash["#{key}"] = _deserialize(type, attributes[map[key]])
         end
       end
       new(transformed_hash)
@@ -139,10 +151,11 @@ def self.build_from_hash(attributes)
     # @return [Hash] Returns the object in the form of hash
     def to_hash
       hash = {}
-      self.class.attribute_map.each_pair do |attr, param|
+      # include attributes inherited from allOf parents (the nearest declaration wins)
+      self.class.acceptable_attribute_map.each_pair do |attr, param|
         value = self.send(attr)
         if value.nil?
-          is_nullable = self.class.openapi_nullable.include?(attr)
+          is_nullable = self.class.acceptable_openapi_nullable.include?(attr)
           next if !is_nullable || (is_nullable && !instance_variable_defined?(:"@#{attr}"))
         end
 
diff --git a/samples/client/echo_api/ruby-httpx/lib/openapi_client/models/category.rb b/samples/client/echo_api/ruby-httpx/lib/openapi_client/models/category.rb
index 2ae2f25e7bb6..a9e3fae3e988 100644
--- a/samples/client/echo_api/ruby-httpx/lib/openapi_client/models/category.rb
+++ b/samples/client/echo_api/ruby-httpx/lib/openapi_client/models/category.rb
@@ -51,6 +51,16 @@ def self.openapi_nullable
       ])
     end
 
+    # Returns attribute type mapping
+    def self.acceptable_openapi_types
+      openapi_types
+    end
+
+    # Returns the nullable attributes
+    def self.acceptable_openapi_nullable
+      openapi_nullable
+    end
+
     # Initializes the object
     # @param [Hash] attributes Model attributes in the form of hash
     def initialize(attributes = {})
@@ -118,18 +128,20 @@ def hash
     def self.build_from_hash(attributes)
       return nil unless attributes.is_a?(Hash)
       attributes = attributes.transform_keys(&:to_sym)
+      # include attributes inherited from allOf parents (the nearest declaration wins)
+      map = acceptable_attribute_map
       transformed_hash = {}
-      openapi_types.each_pair do |key, type|
-        if attributes.key?(attribute_map[key]) && attributes[attribute_map[key]].nil?
+      acceptable_openapi_types.each_pair do |key, type|
+        if attributes.key?(map[key]) && attributes[map[key]].nil?
           transformed_hash["#{key}"] = nil
         elsif type =~ /\AArray<(.*)>/i
           # check to ensure the input is an array given that the attribute
           # is documented as an array but the input is not
-          if attributes[attribute_map[key]].is_a?(Array)
-            transformed_hash["#{key}"] = attributes[attribute_map[key]].map { |v| _deserialize($1, v) }
+          if attributes[map[key]].is_a?(Array)
+            transformed_hash["#{key}"] = attributes[map[key]].map { |v| _deserialize($1, v) }
           end
-        elsif !attributes[attribute_map[key]].nil?
-          transformed_hash["#{key}"] = _deserialize(type, attributes[attribute_map[key]])
+        elsif !attributes[map[key]].nil?
+          transformed_hash["#{key}"] = _deserialize(type, attributes[map[key]])
         end
       end
       new(transformed_hash)
@@ -139,10 +151,11 @@ def self.build_from_hash(attributes)
     # @return [Hash] Returns the object in the form of hash
     def to_hash
       hash = {}
-      self.class.attribute_map.each_pair do |attr, param|
+      # include attributes inherited from allOf parents (the nearest declaration wins)
+      self.class.acceptable_attribute_map.each_pair do |attr, param|
         value = self.send(attr)
         if value.nil?
-          is_nullable = self.class.openapi_nullable.include?(attr)
+          is_nullable = self.class.acceptable_openapi_nullable.include?(attr)
           next if !is_nullable || (is_nullable && !instance_variable_defined?(:"@#{attr}"))
         end
 
diff --git a/samples/client/echo_api/ruby-httpx/lib/openapi_client/models/data_query.rb b/samples/client/echo_api/ruby-httpx/lib/openapi_client/models/data_query.rb
index 1a31b4d3e83f..0575446c351f 100644
--- a/samples/client/echo_api/ruby-httpx/lib/openapi_client/models/data_query.rb
+++ b/samples/client/echo_api/ruby-httpx/lib/openapi_client/models/data_query.rb
@@ -80,6 +80,16 @@ def self.openapi_nullable
       ])
     end
 
+    # Returns attribute type mapping, including the ones defined in its parent(s)
+    def self.acceptable_openapi_types
+      superclass.acceptable_openapi_types.merge(openapi_types)
+    end
+
+    # Returns the nullable attributes, including the ones defined in its parent(s) that it does not redeclare
+    def self.acceptable_openapi_nullable
+      (superclass.acceptable_openapi_nullable - attribute_map.keys) | openapi_nullable
+    end
+
     # List of class defined in allOf (OpenAPI v3)
     def self.openapi_all_of
       [
@@ -161,20 +171,21 @@ def hash
     # @return [Object] Returns the model itself
     def self.build_from_hash(attributes)
       return nil unless attributes.is_a?(Hash)
-      super(attributes)
       attributes = attributes.transform_keys(&:to_sym)
+      # include attributes inherited from allOf parents (the nearest declaration wins)
+      map = acceptable_attribute_map
       transformed_hash = {}
-      openapi_types.each_pair do |key, type|
-        if attributes.key?(attribute_map[key]) && attributes[attribute_map[key]].nil?
+      acceptable_openapi_types.each_pair do |key, type|
+        if attributes.key?(map[key]) && attributes[map[key]].nil?
           transformed_hash["#{key}"] = nil
         elsif type =~ /\AArray<(.*)>/i
           # check to ensure the input is an array given that the attribute
           # is documented as an array but the input is not
-          if attributes[attribute_map[key]].is_a?(Array)
-            transformed_hash["#{key}"] = attributes[attribute_map[key]].map { |v| _deserialize($1, v) }
+          if attributes[map[key]].is_a?(Array)
+            transformed_hash["#{key}"] = attributes[map[key]].map { |v| _deserialize($1, v) }
           end
-        elsif !attributes[attribute_map[key]].nil?
-          transformed_hash["#{key}"] = _deserialize(type, attributes[attribute_map[key]])
+        elsif !attributes[map[key]].nil?
+          transformed_hash["#{key}"] = _deserialize(type, attributes[map[key]])
         end
       end
       new(transformed_hash)
@@ -183,11 +194,12 @@ def self.build_from_hash(attributes)
     # Returns the object in the form of hash
     # @return [Hash] Returns the object in the form of hash
     def to_hash
-      hash = super
-      self.class.attribute_map.each_pair do |attr, param|
+      hash = {}
+      # include attributes inherited from allOf parents (the nearest declaration wins)
+      self.class.acceptable_attribute_map.each_pair do |attr, param|
         value = self.send(attr)
         if value.nil?
-          is_nullable = self.class.openapi_nullable.include?(attr)
+          is_nullable = self.class.acceptable_openapi_nullable.include?(attr)
           next if !is_nullable || (is_nullable && !instance_variable_defined?(:"@#{attr}"))
         end
 
diff --git a/samples/client/echo_api/ruby-httpx/lib/openapi_client/models/default_value.rb b/samples/client/echo_api/ruby-httpx/lib/openapi_client/models/default_value.rb
index 9dbb442bb860..451707d0eeb9 100644
--- a/samples/client/echo_api/ruby-httpx/lib/openapi_client/models/default_value.rb
+++ b/samples/client/echo_api/ruby-httpx/lib/openapi_client/models/default_value.rb
@@ -101,6 +101,16 @@ def self.openapi_nullable
       ])
     end
 
+    # Returns attribute type mapping
+    def self.acceptable_openapi_types
+      openapi_types
+    end
+
+    # Returns the nullable attributes
+    def self.acceptable_openapi_nullable
+      openapi_nullable
+    end
+
     # Initializes the object
     # @param [Hash] attributes Model attributes in the form of hash
     def initialize(attributes = {})
@@ -212,18 +222,20 @@ def hash
     def self.build_from_hash(attributes)
       return nil unless attributes.is_a?(Hash)
       attributes = attributes.transform_keys(&:to_sym)
+      # include attributes inherited from allOf parents (the nearest declaration wins)
+      map = acceptable_attribute_map
       transformed_hash = {}
-      openapi_types.each_pair do |key, type|
-        if attributes.key?(attribute_map[key]) && attributes[attribute_map[key]].nil?
+      acceptable_openapi_types.each_pair do |key, type|
+        if attributes.key?(map[key]) && attributes[map[key]].nil?
           transformed_hash["#{key}"] = nil
         elsif type =~ /\AArray<(.*)>/i
           # check to ensure the input is an array given that the attribute
           # is documented as an array but the input is not
-          if attributes[attribute_map[key]].is_a?(Array)
-            transformed_hash["#{key}"] = attributes[attribute_map[key]].map { |v| _deserialize($1, v) }
+          if attributes[map[key]].is_a?(Array)
+            transformed_hash["#{key}"] = attributes[map[key]].map { |v| _deserialize($1, v) }
           end
-        elsif !attributes[attribute_map[key]].nil?
-          transformed_hash["#{key}"] = _deserialize(type, attributes[attribute_map[key]])
+        elsif !attributes[map[key]].nil?
+          transformed_hash["#{key}"] = _deserialize(type, attributes[map[key]])
         end
       end
       new(transformed_hash)
@@ -233,10 +245,11 @@ def self.build_from_hash(attributes)
     # @return [Hash] Returns the object in the form of hash
     def to_hash
       hash = {}
-      self.class.attribute_map.each_pair do |attr, param|
+      # include attributes inherited from allOf parents (the nearest declaration wins)
+      self.class.acceptable_attribute_map.each_pair do |attr, param|
         value = self.send(attr)
         if value.nil?
-          is_nullable = self.class.openapi_nullable.include?(attr)
+          is_nullable = self.class.acceptable_openapi_nullable.include?(attr)
           next if !is_nullable || (is_nullable && !instance_variable_defined?(:"@#{attr}"))
         end
 
diff --git a/samples/client/echo_api/ruby-httpx/lib/openapi_client/models/number_properties_only.rb b/samples/client/echo_api/ruby-httpx/lib/openapi_client/models/number_properties_only.rb
index 46b63c582964..20ace6a8baad 100644
--- a/samples/client/echo_api/ruby-httpx/lib/openapi_client/models/number_properties_only.rb
+++ b/samples/client/echo_api/ruby-httpx/lib/openapi_client/models/number_properties_only.rb
@@ -55,6 +55,16 @@ def self.openapi_nullable
       ])
     end
 
+    # Returns attribute type mapping
+    def self.acceptable_openapi_types
+      openapi_types
+    end
+
+    # Returns the nullable attributes
+    def self.acceptable_openapi_nullable
+      openapi_nullable
+    end
+
     # Initializes the object
     # @param [Hash] attributes Model attributes in the form of hash
     def initialize(attributes = {})
@@ -155,18 +165,20 @@ def hash
     def self.build_from_hash(attributes)
       return nil unless attributes.is_a?(Hash)
       attributes = attributes.transform_keys(&:to_sym)
+      # include attributes inherited from allOf parents (the nearest declaration wins)
+      map = acceptable_attribute_map
       transformed_hash = {}
-      openapi_types.each_pair do |key, type|
-        if attributes.key?(attribute_map[key]) && attributes[attribute_map[key]].nil?
+      acceptable_openapi_types.each_pair do |key, type|
+        if attributes.key?(map[key]) && attributes[map[key]].nil?
           transformed_hash["#{key}"] = nil
         elsif type =~ /\AArray<(.*)>/i
           # check to ensure the input is an array given that the attribute
           # is documented as an array but the input is not
-          if attributes[attribute_map[key]].is_a?(Array)
-            transformed_hash["#{key}"] = attributes[attribute_map[key]].map { |v| _deserialize($1, v) }
+          if attributes[map[key]].is_a?(Array)
+            transformed_hash["#{key}"] = attributes[map[key]].map { |v| _deserialize($1, v) }
           end
-        elsif !attributes[attribute_map[key]].nil?
-          transformed_hash["#{key}"] = _deserialize(type, attributes[attribute_map[key]])
+        elsif !attributes[map[key]].nil?
+          transformed_hash["#{key}"] = _deserialize(type, attributes[map[key]])
         end
       end
       new(transformed_hash)
@@ -176,10 +188,11 @@ def self.build_from_hash(attributes)
     # @return [Hash] Returns the object in the form of hash
     def to_hash
       hash = {}
-      self.class.attribute_map.each_pair do |attr, param|
+      # include attributes inherited from allOf parents (the nearest declaration wins)
+      self.class.acceptable_attribute_map.each_pair do |attr, param|
         value = self.send(attr)
         if value.nil?
-          is_nullable = self.class.openapi_nullable.include?(attr)
+          is_nullable = self.class.acceptable_openapi_nullable.include?(attr)
           next if !is_nullable || (is_nullable && !instance_variable_defined?(:"@#{attr}"))
         end
 
diff --git a/samples/client/echo_api/ruby-httpx/lib/openapi_client/models/pet.rb b/samples/client/echo_api/ruby-httpx/lib/openapi_client/models/pet.rb
index d1a334676d56..c756e2ce6b41 100644
--- a/samples/client/echo_api/ruby-httpx/lib/openapi_client/models/pet.rb
+++ b/samples/client/echo_api/ruby-httpx/lib/openapi_client/models/pet.rb
@@ -90,6 +90,16 @@ def self.openapi_nullable
       ])
     end
 
+    # Returns attribute type mapping
+    def self.acceptable_openapi_types
+      openapi_types
+    end
+
+    # Returns the nullable attributes
+    def self.acceptable_openapi_nullable
+      openapi_nullable
+    end
+
     # Initializes the object
     # @param [Hash] attributes Model attributes in the form of hash
     def initialize(attributes = {})
@@ -227,18 +237,20 @@ def hash
     def self.build_from_hash(attributes)
       return nil unless attributes.is_a?(Hash)
       attributes = attributes.transform_keys(&:to_sym)
+      # include attributes inherited from allOf parents (the nearest declaration wins)
+      map = acceptable_attribute_map
       transformed_hash = {}
-      openapi_types.each_pair do |key, type|
-        if attributes.key?(attribute_map[key]) && attributes[attribute_map[key]].nil?
+      acceptable_openapi_types.each_pair do |key, type|
+        if attributes.key?(map[key]) && attributes[map[key]].nil?
           transformed_hash["#{key}"] = nil
         elsif type =~ /\AArray<(.*)>/i
           # check to ensure the input is an array given that the attribute
           # is documented as an array but the input is not
-          if attributes[attribute_map[key]].is_a?(Array)
-            transformed_hash["#{key}"] = attributes[attribute_map[key]].map { |v| _deserialize($1, v) }
+          if attributes[map[key]].is_a?(Array)
+            transformed_hash["#{key}"] = attributes[map[key]].map { |v| _deserialize($1, v) }
           end
-        elsif !attributes[attribute_map[key]].nil?
-          transformed_hash["#{key}"] = _deserialize(type, attributes[attribute_map[key]])
+        elsif !attributes[map[key]].nil?
+          transformed_hash["#{key}"] = _deserialize(type, attributes[map[key]])
         end
       end
       new(transformed_hash)
@@ -248,10 +260,11 @@ def self.build_from_hash(attributes)
     # @return [Hash] Returns the object in the form of hash
     def to_hash
       hash = {}
-      self.class.attribute_map.each_pair do |attr, param|
+      # include attributes inherited from allOf parents (the nearest declaration wins)
+      self.class.acceptable_attribute_map.each_pair do |attr, param|
         value = self.send(attr)
         if value.nil?
-          is_nullable = self.class.openapi_nullable.include?(attr)
+          is_nullable = self.class.acceptable_openapi_nullable.include?(attr)
           next if !is_nullable || (is_nullable && !instance_variable_defined?(:"@#{attr}"))
         end
 
diff --git a/samples/client/echo_api/ruby-httpx/lib/openapi_client/models/query.rb b/samples/client/echo_api/ruby-httpx/lib/openapi_client/models/query.rb
index 7598d312f1dd..1e1b31de201b 100644
--- a/samples/client/echo_api/ruby-httpx/lib/openapi_client/models/query.rb
+++ b/samples/client/echo_api/ruby-httpx/lib/openapi_client/models/query.rb
@@ -74,6 +74,16 @@ def self.openapi_nullable
       ])
     end
 
+    # Returns attribute type mapping
+    def self.acceptable_openapi_types
+      openapi_types
+    end
+
+    # Returns the nullable attributes
+    def self.acceptable_openapi_nullable
+      openapi_nullable
+    end
+
     # Initializes the object
     # @param [Hash] attributes Model attributes in the form of hash
     def initialize(attributes = {})
@@ -143,18 +153,20 @@ def hash
     def self.build_from_hash(attributes)
       return nil unless attributes.is_a?(Hash)
       attributes = attributes.transform_keys(&:to_sym)
+      # include attributes inherited from allOf parents (the nearest declaration wins)
+      map = acceptable_attribute_map
       transformed_hash = {}
-      openapi_types.each_pair do |key, type|
-        if attributes.key?(attribute_map[key]) && attributes[attribute_map[key]].nil?
+      acceptable_openapi_types.each_pair do |key, type|
+        if attributes.key?(map[key]) && attributes[map[key]].nil?
           transformed_hash["#{key}"] = nil
         elsif type =~ /\AArray<(.*)>/i
           # check to ensure the input is an array given that the attribute
           # is documented as an array but the input is not
-          if attributes[attribute_map[key]].is_a?(Array)
-            transformed_hash["#{key}"] = attributes[attribute_map[key]].map { |v| _deserialize($1, v) }
+          if attributes[map[key]].is_a?(Array)
+            transformed_hash["#{key}"] = attributes[map[key]].map { |v| _deserialize($1, v) }
           end
-        elsif !attributes[attribute_map[key]].nil?
-          transformed_hash["#{key}"] = _deserialize(type, attributes[attribute_map[key]])
+        elsif !attributes[map[key]].nil?
+          transformed_hash["#{key}"] = _deserialize(type, attributes[map[key]])
         end
       end
       new(transformed_hash)
@@ -164,10 +176,11 @@ def self.build_from_hash(attributes)
     # @return [Hash] Returns the object in the form of hash
     def to_hash
       hash = {}
-      self.class.attribute_map.each_pair do |attr, param|
+      # include attributes inherited from allOf parents (the nearest declaration wins)
+      self.class.acceptable_attribute_map.each_pair do |attr, param|
         value = self.send(attr)
         if value.nil?
-          is_nullable = self.class.openapi_nullable.include?(attr)
+          is_nullable = self.class.acceptable_openapi_nullable.include?(attr)
           next if !is_nullable || (is_nullable && !instance_variable_defined?(:"@#{attr}"))
         end
 
diff --git a/samples/client/echo_api/ruby-httpx/lib/openapi_client/models/tag.rb b/samples/client/echo_api/ruby-httpx/lib/openapi_client/models/tag.rb
index d087eafa1516..e0d61143d2f0 100644
--- a/samples/client/echo_api/ruby-httpx/lib/openapi_client/models/tag.rb
+++ b/samples/client/echo_api/ruby-httpx/lib/openapi_client/models/tag.rb
@@ -51,6 +51,16 @@ def self.openapi_nullable
       ])
     end
 
+    # Returns attribute type mapping
+    def self.acceptable_openapi_types
+      openapi_types
+    end
+
+    # Returns the nullable attributes
+    def self.acceptable_openapi_nullable
+      openapi_nullable
+    end
+
     # Initializes the object
     # @param [Hash] attributes Model attributes in the form of hash
     def initialize(attributes = {})
@@ -118,18 +128,20 @@ def hash
     def self.build_from_hash(attributes)
       return nil unless attributes.is_a?(Hash)
       attributes = attributes.transform_keys(&:to_sym)
+      # include attributes inherited from allOf parents (the nearest declaration wins)
+      map = acceptable_attribute_map
       transformed_hash = {}
-      openapi_types.each_pair do |key, type|
-        if attributes.key?(attribute_map[key]) && attributes[attribute_map[key]].nil?
+      acceptable_openapi_types.each_pair do |key, type|
+        if attributes.key?(map[key]) && attributes[map[key]].nil?
           transformed_hash["#{key}"] = nil
         elsif type =~ /\AArray<(.*)>/i
           # check to ensure the input is an array given that the attribute
           # is documented as an array but the input is not
-          if attributes[attribute_map[key]].is_a?(Array)
-            transformed_hash["#{key}"] = attributes[attribute_map[key]].map { |v| _deserialize($1, v) }
+          if attributes[map[key]].is_a?(Array)
+            transformed_hash["#{key}"] = attributes[map[key]].map { |v| _deserialize($1, v) }
           end
-        elsif !attributes[attribute_map[key]].nil?
-          transformed_hash["#{key}"] = _deserialize(type, attributes[attribute_map[key]])
+        elsif !attributes[map[key]].nil?
+          transformed_hash["#{key}"] = _deserialize(type, attributes[map[key]])
         end
       end
       new(transformed_hash)
@@ -139,10 +151,11 @@ def self.build_from_hash(attributes)
     # @return [Hash] Returns the object in the form of hash
     def to_hash
       hash = {}
-      self.class.attribute_map.each_pair do |attr, param|
+      # include attributes inherited from allOf parents (the nearest declaration wins)
+      self.class.acceptable_attribute_map.each_pair do |attr, param|
         value = self.send(attr)
         if value.nil?
-          is_nullable = self.class.openapi_nullable.include?(attr)
+          is_nullable = self.class.acceptable_openapi_nullable.include?(attr)
           next if !is_nullable || (is_nullable && !instance_variable_defined?(:"@#{attr}"))
         end
 
diff --git a/samples/client/echo_api/ruby-httpx/lib/openapi_client/models/test_form_object_multipart_request_marker.rb b/samples/client/echo_api/ruby-httpx/lib/openapi_client/models/test_form_object_multipart_request_marker.rb
index 1b00e10e7dc3..6b33437e3258 100644
--- a/samples/client/echo_api/ruby-httpx/lib/openapi_client/models/test_form_object_multipart_request_marker.rb
+++ b/samples/client/echo_api/ruby-httpx/lib/openapi_client/models/test_form_object_multipart_request_marker.rb
@@ -47,6 +47,16 @@ def self.openapi_nullable
       ])
     end
 
+    # Returns attribute type mapping
+    def self.acceptable_openapi_types
+      openapi_types
+    end
+
+    # Returns the nullable attributes
+    def self.acceptable_openapi_nullable
+      openapi_nullable
+    end
+
     # Initializes the object
     # @param [Hash] attributes Model attributes in the form of hash
     def initialize(attributes = {})
@@ -109,18 +119,20 @@ def hash
     def self.build_from_hash(attributes)
       return nil unless attributes.is_a?(Hash)
       attributes = attributes.transform_keys(&:to_sym)
+      # include attributes inherited from allOf parents (the nearest declaration wins)
+      map = acceptable_attribute_map
       transformed_hash = {}
-      openapi_types.each_pair do |key, type|
-        if attributes.key?(attribute_map[key]) && attributes[attribute_map[key]].nil?
+      acceptable_openapi_types.each_pair do |key, type|
+        if attributes.key?(map[key]) && attributes[map[key]].nil?
           transformed_hash["#{key}"] = nil
         elsif type =~ /\AArray<(.*)>/i
           # check to ensure the input is an array given that the attribute
           # is documented as an array but the input is not
-          if attributes[attribute_map[key]].is_a?(Array)
-            transformed_hash["#{key}"] = attributes[attribute_map[key]].map { |v| _deserialize($1, v) }
+          if attributes[map[key]].is_a?(Array)
+            transformed_hash["#{key}"] = attributes[map[key]].map { |v| _deserialize($1, v) }
           end
-        elsif !attributes[attribute_map[key]].nil?
-          transformed_hash["#{key}"] = _deserialize(type, attributes[attribute_map[key]])
+        elsif !attributes[map[key]].nil?
+          transformed_hash["#{key}"] = _deserialize(type, attributes[map[key]])
         end
       end
       new(transformed_hash)
@@ -130,10 +142,11 @@ def self.build_from_hash(attributes)
     # @return [Hash] Returns the object in the form of hash
     def to_hash
       hash = {}
-      self.class.attribute_map.each_pair do |attr, param|
+      # include attributes inherited from allOf parents (the nearest declaration wins)
+      self.class.acceptable_attribute_map.each_pair do |attr, param|
         value = self.send(attr)
         if value.nil?
-          is_nullable = self.class.openapi_nullable.include?(attr)
+          is_nullable = self.class.acceptable_openapi_nullable.include?(attr)
           next if !is_nullable || (is_nullable && !instance_variable_defined?(:"@#{attr}"))
         end
 
diff --git a/samples/client/echo_api/ruby-httpx/lib/openapi_client/models/test_query_style_deep_object_explode_true_object_all_of_query_object_parameter.rb b/samples/client/echo_api/ruby-httpx/lib/openapi_client/models/test_query_style_deep_object_explode_true_object_all_of_query_object_parameter.rb
index 02afae09bce2..04a9bd521165 100644
--- a/samples/client/echo_api/ruby-httpx/lib/openapi_client/models/test_query_style_deep_object_explode_true_object_all_of_query_object_parameter.rb
+++ b/samples/client/echo_api/ruby-httpx/lib/openapi_client/models/test_query_style_deep_object_explode_true_object_all_of_query_object_parameter.rb
@@ -59,6 +59,16 @@ def self.openapi_nullable
       ])
     end
 
+    # Returns attribute type mapping
+    def self.acceptable_openapi_types
+      openapi_types
+    end
+
+    # Returns the nullable attributes
+    def self.acceptable_openapi_nullable
+      openapi_nullable
+    end
+
     # List of class defined in allOf (OpenAPI v3)
     def self.openapi_all_of
       [
@@ -144,18 +154,20 @@ def hash
     def self.build_from_hash(attributes)
       return nil unless attributes.is_a?(Hash)
       attributes = attributes.transform_keys(&:to_sym)
+      # include attributes inherited from allOf parents (the nearest declaration wins)
+      map = acceptable_attribute_map
       transformed_hash = {}
-      openapi_types.each_pair do |key, type|
-        if attributes.key?(attribute_map[key]) && attributes[attribute_map[key]].nil?
+      acceptable_openapi_types.each_pair do |key, type|
+        if attributes.key?(map[key]) && attributes[map[key]].nil?
           transformed_hash["#{key}"] = nil
         elsif type =~ /\AArray<(.*)>/i
           # check to ensure the input is an array given that the attribute
           # is documented as an array but the input is not
-          if attributes[attribute_map[key]].is_a?(Array)
-            transformed_hash["#{key}"] = attributes[attribute_map[key]].map { |v| _deserialize($1, v) }
+          if attributes[map[key]].is_a?(Array)
+            transformed_hash["#{key}"] = attributes[map[key]].map { |v| _deserialize($1, v) }
           end
-        elsif !attributes[attribute_map[key]].nil?
-          transformed_hash["#{key}"] = _deserialize(type, attributes[attribute_map[key]])
+        elsif !attributes[map[key]].nil?
+          transformed_hash["#{key}"] = _deserialize(type, attributes[map[key]])
         end
       end
       new(transformed_hash)
@@ -165,10 +177,11 @@ def self.build_from_hash(attributes)
     # @return [Hash] Returns the object in the form of hash
     def to_hash
       hash = {}
-      self.class.attribute_map.each_pair do |attr, param|
+      # include attributes inherited from allOf parents (the nearest declaration wins)
+      self.class.acceptable_attribute_map.each_pair do |attr, param|
         value = self.send(attr)
         if value.nil?
-          is_nullable = self.class.openapi_nullable.include?(attr)
+          is_nullable = self.class.acceptable_openapi_nullable.include?(attr)
           next if !is_nullable || (is_nullable && !instance_variable_defined?(:"@#{attr}"))
         end
 
diff --git a/samples/client/echo_api/ruby-httpx/lib/openapi_client/models/test_query_style_form_explode_true_array_string_query_object_parameter.rb b/samples/client/echo_api/ruby-httpx/lib/openapi_client/models/test_query_style_form_explode_true_array_string_query_object_parameter.rb
index fa9520a4f16c..3c67a8e0f2a9 100644
--- a/samples/client/echo_api/ruby-httpx/lib/openapi_client/models/test_query_style_form_explode_true_array_string_query_object_parameter.rb
+++ b/samples/client/echo_api/ruby-httpx/lib/openapi_client/models/test_query_style_form_explode_true_array_string_query_object_parameter.rb
@@ -47,6 +47,16 @@ def self.openapi_nullable
       ])
     end
 
+    # Returns attribute type mapping
+    def self.acceptable_openapi_types
+      openapi_types
+    end
+
+    # Returns the nullable attributes
+    def self.acceptable_openapi_nullable
+      openapi_nullable
+    end
+
     # Initializes the object
     # @param [Hash] attributes Model attributes in the form of hash
     def initialize(attributes = {})
@@ -111,18 +121,20 @@ def hash
     def self.build_from_hash(attributes)
       return nil unless attributes.is_a?(Hash)
       attributes = attributes.transform_keys(&:to_sym)
+      # include attributes inherited from allOf parents (the nearest declaration wins)
+      map = acceptable_attribute_map
       transformed_hash = {}
-      openapi_types.each_pair do |key, type|
-        if attributes.key?(attribute_map[key]) && attributes[attribute_map[key]].nil?
+      acceptable_openapi_types.each_pair do |key, type|
+        if attributes.key?(map[key]) && attributes[map[key]].nil?
           transformed_hash["#{key}"] = nil
         elsif type =~ /\AArray<(.*)>/i
           # check to ensure the input is an array given that the attribute
           # is documented as an array but the input is not
-          if attributes[attribute_map[key]].is_a?(Array)
-            transformed_hash["#{key}"] = attributes[attribute_map[key]].map { |v| _deserialize($1, v) }
+          if attributes[map[key]].is_a?(Array)
+            transformed_hash["#{key}"] = attributes[map[key]].map { |v| _deserialize($1, v) }
           end
-        elsif !attributes[attribute_map[key]].nil?
-          transformed_hash["#{key}"] = _deserialize(type, attributes[attribute_map[key]])
+        elsif !attributes[map[key]].nil?
+          transformed_hash["#{key}"] = _deserialize(type, attributes[map[key]])
         end
       end
       new(transformed_hash)
@@ -132,10 +144,11 @@ def self.build_from_hash(attributes)
     # @return [Hash] Returns the object in the form of hash
     def to_hash
       hash = {}
-      self.class.attribute_map.each_pair do |attr, param|
+      # include attributes inherited from allOf parents (the nearest declaration wins)
+      self.class.acceptable_attribute_map.each_pair do |attr, param|
         value = self.send(attr)
         if value.nil?
-          is_nullable = self.class.openapi_nullable.include?(attr)
+          is_nullable = self.class.acceptable_openapi_nullable.include?(attr)
           next if !is_nullable || (is_nullable && !instance_variable_defined?(:"@#{attr}"))
         end
 
diff --git a/samples/client/echo_api/ruby-typhoeus/lib/openapi_client/models/bird.rb b/samples/client/echo_api/ruby-typhoeus/lib/openapi_client/models/bird.rb
index 791ff7830e90..9f03a6daeca5 100644
--- a/samples/client/echo_api/ruby-typhoeus/lib/openapi_client/models/bird.rb
+++ b/samples/client/echo_api/ruby-typhoeus/lib/openapi_client/models/bird.rb
@@ -51,6 +51,16 @@ def self.openapi_nullable
       ])
     end
 
+    # Returns attribute type mapping
+    def self.acceptable_openapi_types
+      openapi_types
+    end
+
+    # Returns the nullable attributes
+    def self.acceptable_openapi_nullable
+      openapi_nullable
+    end
+
     # Initializes the object
     # @param [Hash] attributes Model attributes in the form of hash
     def initialize(attributes = {})
@@ -118,18 +128,20 @@ def hash
     def self.build_from_hash(attributes)
       return nil unless attributes.is_a?(Hash)
       attributes = attributes.transform_keys(&:to_sym)
+      # include attributes inherited from allOf parents (the nearest declaration wins)
+      map = acceptable_attribute_map
       transformed_hash = {}
-      openapi_types.each_pair do |key, type|
-        if attributes.key?(attribute_map[key]) && attributes[attribute_map[key]].nil?
+      acceptable_openapi_types.each_pair do |key, type|
+        if attributes.key?(map[key]) && attributes[map[key]].nil?
           transformed_hash["#{key}"] = nil
         elsif type =~ /\AArray<(.*)>/i
           # check to ensure the input is an array given that the attribute
           # is documented as an array but the input is not
-          if attributes[attribute_map[key]].is_a?(Array)
-            transformed_hash["#{key}"] = attributes[attribute_map[key]].map { |v| _deserialize($1, v) }
+          if attributes[map[key]].is_a?(Array)
+            transformed_hash["#{key}"] = attributes[map[key]].map { |v| _deserialize($1, v) }
           end
-        elsif !attributes[attribute_map[key]].nil?
-          transformed_hash["#{key}"] = _deserialize(type, attributes[attribute_map[key]])
+        elsif !attributes[map[key]].nil?
+          transformed_hash["#{key}"] = _deserialize(type, attributes[map[key]])
         end
       end
       new(transformed_hash)
@@ -139,10 +151,11 @@ def self.build_from_hash(attributes)
     # @return [Hash] Returns the object in the form of hash
     def to_hash
       hash = {}
-      self.class.attribute_map.each_pair do |attr, param|
+      # include attributes inherited from allOf parents (the nearest declaration wins)
+      self.class.acceptable_attribute_map.each_pair do |attr, param|
         value = self.send(attr)
         if value.nil?
-          is_nullable = self.class.openapi_nullable.include?(attr)
+          is_nullable = self.class.acceptable_openapi_nullable.include?(attr)
           next if !is_nullable || (is_nullable && !instance_variable_defined?(:"@#{attr}"))
         end
 
diff --git a/samples/client/echo_api/ruby-typhoeus/lib/openapi_client/models/category.rb b/samples/client/echo_api/ruby-typhoeus/lib/openapi_client/models/category.rb
index 2ae2f25e7bb6..a9e3fae3e988 100644
--- a/samples/client/echo_api/ruby-typhoeus/lib/openapi_client/models/category.rb
+++ b/samples/client/echo_api/ruby-typhoeus/lib/openapi_client/models/category.rb
@@ -51,6 +51,16 @@ def self.openapi_nullable
       ])
     end
 
+    # Returns attribute type mapping
+    def self.acceptable_openapi_types
+      openapi_types
+    end
+
+    # Returns the nullable attributes
+    def self.acceptable_openapi_nullable
+      openapi_nullable
+    end
+
     # Initializes the object
     # @param [Hash] attributes Model attributes in the form of hash
     def initialize(attributes = {})
@@ -118,18 +128,20 @@ def hash
     def self.build_from_hash(attributes)
       return nil unless attributes.is_a?(Hash)
       attributes = attributes.transform_keys(&:to_sym)
+      # include attributes inherited from allOf parents (the nearest declaration wins)
+      map = acceptable_attribute_map
       transformed_hash = {}
-      openapi_types.each_pair do |key, type|
-        if attributes.key?(attribute_map[key]) && attributes[attribute_map[key]].nil?
+      acceptable_openapi_types.each_pair do |key, type|
+        if attributes.key?(map[key]) && attributes[map[key]].nil?
           transformed_hash["#{key}"] = nil
         elsif type =~ /\AArray<(.*)>/i
           # check to ensure the input is an array given that the attribute
           # is documented as an array but the input is not
-          if attributes[attribute_map[key]].is_a?(Array)
-            transformed_hash["#{key}"] = attributes[attribute_map[key]].map { |v| _deserialize($1, v) }
+          if attributes[map[key]].is_a?(Array)
+            transformed_hash["#{key}"] = attributes[map[key]].map { |v| _deserialize($1, v) }
           end
-        elsif !attributes[attribute_map[key]].nil?
-          transformed_hash["#{key}"] = _deserialize(type, attributes[attribute_map[key]])
+        elsif !attributes[map[key]].nil?
+          transformed_hash["#{key}"] = _deserialize(type, attributes[map[key]])
         end
       end
       new(transformed_hash)
@@ -139,10 +151,11 @@ def self.build_from_hash(attributes)
     # @return [Hash] Returns the object in the form of hash
     def to_hash
       hash = {}
-      self.class.attribute_map.each_pair do |attr, param|
+      # include attributes inherited from allOf parents (the nearest declaration wins)
+      self.class.acceptable_attribute_map.each_pair do |attr, param|
         value = self.send(attr)
         if value.nil?
-          is_nullable = self.class.openapi_nullable.include?(attr)
+          is_nullable = self.class.acceptable_openapi_nullable.include?(attr)
           next if !is_nullable || (is_nullable && !instance_variable_defined?(:"@#{attr}"))
         end
 
diff --git a/samples/client/echo_api/ruby-typhoeus/lib/openapi_client/models/data_query.rb b/samples/client/echo_api/ruby-typhoeus/lib/openapi_client/models/data_query.rb
index 1a31b4d3e83f..0575446c351f 100644
--- a/samples/client/echo_api/ruby-typhoeus/lib/openapi_client/models/data_query.rb
+++ b/samples/client/echo_api/ruby-typhoeus/lib/openapi_client/models/data_query.rb
@@ -80,6 +80,16 @@ def self.openapi_nullable
       ])
     end
 
+    # Returns attribute type mapping, including the ones defined in its parent(s)
+    def self.acceptable_openapi_types
+      superclass.acceptable_openapi_types.merge(openapi_types)
+    end
+
+    # Returns the nullable attributes, including the ones defined in its parent(s) that it does not redeclare
+    def self.acceptable_openapi_nullable
+      (superclass.acceptable_openapi_nullable - attribute_map.keys) | openapi_nullable
+    end
+
     # List of class defined in allOf (OpenAPI v3)
     def self.openapi_all_of
       [
@@ -161,20 +171,21 @@ def hash
     # @return [Object] Returns the model itself
     def self.build_from_hash(attributes)
       return nil unless attributes.is_a?(Hash)
-      super(attributes)
       attributes = attributes.transform_keys(&:to_sym)
+      # include attributes inherited from allOf parents (the nearest declaration wins)
+      map = acceptable_attribute_map
       transformed_hash = {}
-      openapi_types.each_pair do |key, type|
-        if attributes.key?(attribute_map[key]) && attributes[attribute_map[key]].nil?
+      acceptable_openapi_types.each_pair do |key, type|
+        if attributes.key?(map[key]) && attributes[map[key]].nil?
           transformed_hash["#{key}"] = nil
         elsif type =~ /\AArray<(.*)>/i
           # check to ensure the input is an array given that the attribute
           # is documented as an array but the input is not
-          if attributes[attribute_map[key]].is_a?(Array)
-            transformed_hash["#{key}"] = attributes[attribute_map[key]].map { |v| _deserialize($1, v) }
+          if attributes[map[key]].is_a?(Array)
+            transformed_hash["#{key}"] = attributes[map[key]].map { |v| _deserialize($1, v) }
           end
-        elsif !attributes[attribute_map[key]].nil?
-          transformed_hash["#{key}"] = _deserialize(type, attributes[attribute_map[key]])
+        elsif !attributes[map[key]].nil?
+          transformed_hash["#{key}"] = _deserialize(type, attributes[map[key]])
         end
       end
       new(transformed_hash)
@@ -183,11 +194,12 @@ def self.build_from_hash(attributes)
     # Returns the object in the form of hash
     # @return [Hash] Returns the object in the form of hash
     def to_hash
-      hash = super
-      self.class.attribute_map.each_pair do |attr, param|
+      hash = {}
+      # include attributes inherited from allOf parents (the nearest declaration wins)
+      self.class.acceptable_attribute_map.each_pair do |attr, param|
         value = self.send(attr)
         if value.nil?
-          is_nullable = self.class.openapi_nullable.include?(attr)
+          is_nullable = self.class.acceptable_openapi_nullable.include?(attr)
           next if !is_nullable || (is_nullable && !instance_variable_defined?(:"@#{attr}"))
         end
 
diff --git a/samples/client/echo_api/ruby-typhoeus/lib/openapi_client/models/default_value.rb b/samples/client/echo_api/ruby-typhoeus/lib/openapi_client/models/default_value.rb
index 9dbb442bb860..451707d0eeb9 100644
--- a/samples/client/echo_api/ruby-typhoeus/lib/openapi_client/models/default_value.rb
+++ b/samples/client/echo_api/ruby-typhoeus/lib/openapi_client/models/default_value.rb
@@ -101,6 +101,16 @@ def self.openapi_nullable
       ])
     end
 
+    # Returns attribute type mapping
+    def self.acceptable_openapi_types
+      openapi_types
+    end
+
+    # Returns the nullable attributes
+    def self.acceptable_openapi_nullable
+      openapi_nullable
+    end
+
     # Initializes the object
     # @param [Hash] attributes Model attributes in the form of hash
     def initialize(attributes = {})
@@ -212,18 +222,20 @@ def hash
     def self.build_from_hash(attributes)
       return nil unless attributes.is_a?(Hash)
       attributes = attributes.transform_keys(&:to_sym)
+      # include attributes inherited from allOf parents (the nearest declaration wins)
+      map = acceptable_attribute_map
       transformed_hash = {}
-      openapi_types.each_pair do |key, type|
-        if attributes.key?(attribute_map[key]) && attributes[attribute_map[key]].nil?
+      acceptable_openapi_types.each_pair do |key, type|
+        if attributes.key?(map[key]) && attributes[map[key]].nil?
           transformed_hash["#{key}"] = nil
         elsif type =~ /\AArray<(.*)>/i
           # check to ensure the input is an array given that the attribute
           # is documented as an array but the input is not
-          if attributes[attribute_map[key]].is_a?(Array)
-            transformed_hash["#{key}"] = attributes[attribute_map[key]].map { |v| _deserialize($1, v) }
+          if attributes[map[key]].is_a?(Array)
+            transformed_hash["#{key}"] = attributes[map[key]].map { |v| _deserialize($1, v) }
           end
-        elsif !attributes[attribute_map[key]].nil?
-          transformed_hash["#{key}"] = _deserialize(type, attributes[attribute_map[key]])
+        elsif !attributes[map[key]].nil?
+          transformed_hash["#{key}"] = _deserialize(type, attributes[map[key]])
         end
       end
       new(transformed_hash)
@@ -233,10 +245,11 @@ def self.build_from_hash(attributes)
     # @return [Hash] Returns the object in the form of hash
     def to_hash
       hash = {}
-      self.class.attribute_map.each_pair do |attr, param|
+      # include attributes inherited from allOf parents (the nearest declaration wins)
+      self.class.acceptable_attribute_map.each_pair do |attr, param|
         value = self.send(attr)
         if value.nil?
-          is_nullable = self.class.openapi_nullable.include?(attr)
+          is_nullable = self.class.acceptable_openapi_nullable.include?(attr)
           next if !is_nullable || (is_nullable && !instance_variable_defined?(:"@#{attr}"))
         end
 
diff --git a/samples/client/echo_api/ruby-typhoeus/lib/openapi_client/models/number_properties_only.rb b/samples/client/echo_api/ruby-typhoeus/lib/openapi_client/models/number_properties_only.rb
index 46b63c582964..20ace6a8baad 100644
--- a/samples/client/echo_api/ruby-typhoeus/lib/openapi_client/models/number_properties_only.rb
+++ b/samples/client/echo_api/ruby-typhoeus/lib/openapi_client/models/number_properties_only.rb
@@ -55,6 +55,16 @@ def self.openapi_nullable
       ])
     end
 
+    # Returns attribute type mapping
+    def self.acceptable_openapi_types
+      openapi_types
+    end
+
+    # Returns the nullable attributes
+    def self.acceptable_openapi_nullable
+      openapi_nullable
+    end
+
     # Initializes the object
     # @param [Hash] attributes Model attributes in the form of hash
     def initialize(attributes = {})
@@ -155,18 +165,20 @@ def hash
     def self.build_from_hash(attributes)
       return nil unless attributes.is_a?(Hash)
       attributes = attributes.transform_keys(&:to_sym)
+      # include attributes inherited from allOf parents (the nearest declaration wins)
+      map = acceptable_attribute_map
       transformed_hash = {}
-      openapi_types.each_pair do |key, type|
-        if attributes.key?(attribute_map[key]) && attributes[attribute_map[key]].nil?
+      acceptable_openapi_types.each_pair do |key, type|
+        if attributes.key?(map[key]) && attributes[map[key]].nil?
           transformed_hash["#{key}"] = nil
         elsif type =~ /\AArray<(.*)>/i
           # check to ensure the input is an array given that the attribute
           # is documented as an array but the input is not
-          if attributes[attribute_map[key]].is_a?(Array)
-            transformed_hash["#{key}"] = attributes[attribute_map[key]].map { |v| _deserialize($1, v) }
+          if attributes[map[key]].is_a?(Array)
+            transformed_hash["#{key}"] = attributes[map[key]].map { |v| _deserialize($1, v) }
           end
-        elsif !attributes[attribute_map[key]].nil?
-          transformed_hash["#{key}"] = _deserialize(type, attributes[attribute_map[key]])
+        elsif !attributes[map[key]].nil?
+          transformed_hash["#{key}"] = _deserialize(type, attributes[map[key]])
         end
       end
       new(transformed_hash)
@@ -176,10 +188,11 @@ def self.build_from_hash(attributes)
     # @return [Hash] Returns the object in the form of hash
     def to_hash
       hash = {}
-      self.class.attribute_map.each_pair do |attr, param|
+      # include attributes inherited from allOf parents (the nearest declaration wins)
+      self.class.acceptable_attribute_map.each_pair do |attr, param|
         value = self.send(attr)
         if value.nil?
-          is_nullable = self.class.openapi_nullable.include?(attr)
+          is_nullable = self.class.acceptable_openapi_nullable.include?(attr)
           next if !is_nullable || (is_nullable && !instance_variable_defined?(:"@#{attr}"))
         end
 
diff --git a/samples/client/echo_api/ruby-typhoeus/lib/openapi_client/models/pet.rb b/samples/client/echo_api/ruby-typhoeus/lib/openapi_client/models/pet.rb
index d1a334676d56..c756e2ce6b41 100644
--- a/samples/client/echo_api/ruby-typhoeus/lib/openapi_client/models/pet.rb
+++ b/samples/client/echo_api/ruby-typhoeus/lib/openapi_client/models/pet.rb
@@ -90,6 +90,16 @@ def self.openapi_nullable
       ])
     end
 
+    # Returns attribute type mapping
+    def self.acceptable_openapi_types
+      openapi_types
+    end
+
+    # Returns the nullable attributes
+    def self.acceptable_openapi_nullable
+      openapi_nullable
+    end
+
     # Initializes the object
     # @param [Hash] attributes Model attributes in the form of hash
     def initialize(attributes = {})
@@ -227,18 +237,20 @@ def hash
     def self.build_from_hash(attributes)
       return nil unless attributes.is_a?(Hash)
       attributes = attributes.transform_keys(&:to_sym)
+      # include attributes inherited from allOf parents (the nearest declaration wins)
+      map = acceptable_attribute_map
       transformed_hash = {}
-      openapi_types.each_pair do |key, type|
-        if attributes.key?(attribute_map[key]) && attributes[attribute_map[key]].nil?
+      acceptable_openapi_types.each_pair do |key, type|
+        if attributes.key?(map[key]) && attributes[map[key]].nil?
           transformed_hash["#{key}"] = nil
         elsif type =~ /\AArray<(.*)>/i
           # check to ensure the input is an array given that the attribute
           # is documented as an array but the input is not
-          if attributes[attribute_map[key]].is_a?(Array)
-            transformed_hash["#{key}"] = attributes[attribute_map[key]].map { |v| _deserialize($1, v) }
+          if attributes[map[key]].is_a?(Array)
+            transformed_hash["#{key}"] = attributes[map[key]].map { |v| _deserialize($1, v) }
           end
-        elsif !attributes[attribute_map[key]].nil?
-          transformed_hash["#{key}"] = _deserialize(type, attributes[attribute_map[key]])
+        elsif !attributes[map[key]].nil?
+          transformed_hash["#{key}"] = _deserialize(type, attributes[map[key]])
         end
       end
       new(transformed_hash)
@@ -248,10 +260,11 @@ def self.build_from_hash(attributes)
     # @return [Hash] Returns the object in the form of hash
     def to_hash
       hash = {}
-      self.class.attribute_map.each_pair do |attr, param|
+      # include attributes inherited from allOf parents (the nearest declaration wins)
+      self.class.acceptable_attribute_map.each_pair do |attr, param|
         value = self.send(attr)
         if value.nil?
-          is_nullable = self.class.openapi_nullable.include?(attr)
+          is_nullable = self.class.acceptable_openapi_nullable.include?(attr)
           next if !is_nullable || (is_nullable && !instance_variable_defined?(:"@#{attr}"))
         end
 
diff --git a/samples/client/echo_api/ruby-typhoeus/lib/openapi_client/models/query.rb b/samples/client/echo_api/ruby-typhoeus/lib/openapi_client/models/query.rb
index 7598d312f1dd..1e1b31de201b 100644
--- a/samples/client/echo_api/ruby-typhoeus/lib/openapi_client/models/query.rb
+++ b/samples/client/echo_api/ruby-typhoeus/lib/openapi_client/models/query.rb
@@ -74,6 +74,16 @@ def self.openapi_nullable
       ])
     end
 
+    # Returns attribute type mapping
+    def self.acceptable_openapi_types
+      openapi_types
+    end
+
+    # Returns the nullable attributes
+    def self.acceptable_openapi_nullable
+      openapi_nullable
+    end
+
     # Initializes the object
     # @param [Hash] attributes Model attributes in the form of hash
     def initialize(attributes = {})
@@ -143,18 +153,20 @@ def hash
     def self.build_from_hash(attributes)
       return nil unless attributes.is_a?(Hash)
       attributes = attributes.transform_keys(&:to_sym)
+      # include attributes inherited from allOf parents (the nearest declaration wins)
+      map = acceptable_attribute_map
       transformed_hash = {}
-      openapi_types.each_pair do |key, type|
-        if attributes.key?(attribute_map[key]) && attributes[attribute_map[key]].nil?
+      acceptable_openapi_types.each_pair do |key, type|
+        if attributes.key?(map[key]) && attributes[map[key]].nil?
           transformed_hash["#{key}"] = nil
         elsif type =~ /\AArray<(.*)>/i
           # check to ensure the input is an array given that the attribute
           # is documented as an array but the input is not
-          if attributes[attribute_map[key]].is_a?(Array)
-            transformed_hash["#{key}"] = attributes[attribute_map[key]].map { |v| _deserialize($1, v) }
+          if attributes[map[key]].is_a?(Array)
+            transformed_hash["#{key}"] = attributes[map[key]].map { |v| _deserialize($1, v) }
           end
-        elsif !attributes[attribute_map[key]].nil?
-          transformed_hash["#{key}"] = _deserialize(type, attributes[attribute_map[key]])
+        elsif !attributes[map[key]].nil?
+          transformed_hash["#{key}"] = _deserialize(type, attributes[map[key]])
         end
       end
       new(transformed_hash)
@@ -164,10 +176,11 @@ def self.build_from_hash(attributes)
     # @return [Hash] Returns the object in the form of hash
     def to_hash
       hash = {}
-      self.class.attribute_map.each_pair do |attr, param|
+      # include attributes inherited from allOf parents (the nearest declaration wins)
+      self.class.acceptable_attribute_map.each_pair do |attr, param|
         value = self.send(attr)
         if value.nil?
-          is_nullable = self.class.openapi_nullable.include?(attr)
+          is_nullable = self.class.acceptable_openapi_nullable.include?(attr)
           next if !is_nullable || (is_nullable && !instance_variable_defined?(:"@#{attr}"))
         end
 
diff --git a/samples/client/echo_api/ruby-typhoeus/lib/openapi_client/models/tag.rb b/samples/client/echo_api/ruby-typhoeus/lib/openapi_client/models/tag.rb
index d087eafa1516..e0d61143d2f0 100644
--- a/samples/client/echo_api/ruby-typhoeus/lib/openapi_client/models/tag.rb
+++ b/samples/client/echo_api/ruby-typhoeus/lib/openapi_client/models/tag.rb
@@ -51,6 +51,16 @@ def self.openapi_nullable
       ])
     end
 
+    # Returns attribute type mapping
+    def self.acceptable_openapi_types
+      openapi_types
+    end
+
+    # Returns the nullable attributes
+    def self.acceptable_openapi_nullable
+      openapi_nullable
+    end
+
     # Initializes the object
     # @param [Hash] attributes Model attributes in the form of hash
     def initialize(attributes = {})
@@ -118,18 +128,20 @@ def hash
     def self.build_from_hash(attributes)
       return nil unless attributes.is_a?(Hash)
       attributes = attributes.transform_keys(&:to_sym)
+      # include attributes inherited from allOf parents (the nearest declaration wins)
+      map = acceptable_attribute_map
       transformed_hash = {}
-      openapi_types.each_pair do |key, type|
-        if attributes.key?(attribute_map[key]) && attributes[attribute_map[key]].nil?
+      acceptable_openapi_types.each_pair do |key, type|
+        if attributes.key?(map[key]) && attributes[map[key]].nil?
           transformed_hash["#{key}"] = nil
         elsif type =~ /\AArray<(.*)>/i
           # check to ensure the input is an array given that the attribute
           # is documented as an array but the input is not
-          if attributes[attribute_map[key]].is_a?(Array)
-            transformed_hash["#{key}"] = attributes[attribute_map[key]].map { |v| _deserialize($1, v) }
+          if attributes[map[key]].is_a?(Array)
+            transformed_hash["#{key}"] = attributes[map[key]].map { |v| _deserialize($1, v) }
           end
-        elsif !attributes[attribute_map[key]].nil?
-          transformed_hash["#{key}"] = _deserialize(type, attributes[attribute_map[key]])
+        elsif !attributes[map[key]].nil?
+          transformed_hash["#{key}"] = _deserialize(type, attributes[map[key]])
         end
       end
       new(transformed_hash)
@@ -139,10 +151,11 @@ def self.build_from_hash(attributes)
     # @return [Hash] Returns the object in the form of hash
     def to_hash
       hash = {}
-      self.class.attribute_map.each_pair do |attr, param|
+      # include attributes inherited from allOf parents (the nearest declaration wins)
+      self.class.acceptable_attribute_map.each_pair do |attr, param|
         value = self.send(attr)
         if value.nil?
-          is_nullable = self.class.openapi_nullable.include?(attr)
+          is_nullable = self.class.acceptable_openapi_nullable.include?(attr)
           next if !is_nullable || (is_nullable && !instance_variable_defined?(:"@#{attr}"))
         end
 
diff --git a/samples/client/echo_api/ruby-typhoeus/lib/openapi_client/models/test_form_object_multipart_request_marker.rb b/samples/client/echo_api/ruby-typhoeus/lib/openapi_client/models/test_form_object_multipart_request_marker.rb
index 1b00e10e7dc3..6b33437e3258 100644
--- a/samples/client/echo_api/ruby-typhoeus/lib/openapi_client/models/test_form_object_multipart_request_marker.rb
+++ b/samples/client/echo_api/ruby-typhoeus/lib/openapi_client/models/test_form_object_multipart_request_marker.rb
@@ -47,6 +47,16 @@ def self.openapi_nullable
       ])
     end
 
+    # Returns attribute type mapping
+    def self.acceptable_openapi_types
+      openapi_types
+    end
+
+    # Returns the nullable attributes
+    def self.acceptable_openapi_nullable
+      openapi_nullable
+    end
+
     # Initializes the object
     # @param [Hash] attributes Model attributes in the form of hash
     def initialize(attributes = {})
@@ -109,18 +119,20 @@ def hash
     def self.build_from_hash(attributes)
       return nil unless attributes.is_a?(Hash)
       attributes = attributes.transform_keys(&:to_sym)
+      # include attributes inherited from allOf parents (the nearest declaration wins)
+      map = acceptable_attribute_map
       transformed_hash = {}
-      openapi_types.each_pair do |key, type|
-        if attributes.key?(attribute_map[key]) && attributes[attribute_map[key]].nil?
+      acceptable_openapi_types.each_pair do |key, type|
+        if attributes.key?(map[key]) && attributes[map[key]].nil?
           transformed_hash["#{key}"] = nil
         elsif type =~ /\AArray<(.*)>/i
           # check to ensure the input is an array given that the attribute
           # is documented as an array but the input is not
-          if attributes[attribute_map[key]].is_a?(Array)
-            transformed_hash["#{key}"] = attributes[attribute_map[key]].map { |v| _deserialize($1, v) }
+          if attributes[map[key]].is_a?(Array)
+            transformed_hash["#{key}"] = attributes[map[key]].map { |v| _deserialize($1, v) }
           end
-        elsif !attributes[attribute_map[key]].nil?
-          transformed_hash["#{key}"] = _deserialize(type, attributes[attribute_map[key]])
+        elsif !attributes[map[key]].nil?
+          transformed_hash["#{key}"] = _deserialize(type, attributes[map[key]])
         end
       end
       new(transformed_hash)
@@ -130,10 +142,11 @@ def self.build_from_hash(attributes)
     # @return [Hash] Returns the object in the form of hash
     def to_hash
       hash = {}
-      self.class.attribute_map.each_pair do |attr, param|
+      # include attributes inherited from allOf parents (the nearest declaration wins)
+      self.class.acceptable_attribute_map.each_pair do |attr, param|
         value = self.send(attr)
         if value.nil?
-          is_nullable = self.class.openapi_nullable.include?(attr)
+          is_nullable = self.class.acceptable_openapi_nullable.include?(attr)
           next if !is_nullable || (is_nullable && !instance_variable_defined?(:"@#{attr}"))
         end
 
diff --git a/samples/client/echo_api/ruby-typhoeus/lib/openapi_client/models/test_query_style_deep_object_explode_true_object_all_of_query_object_parameter.rb b/samples/client/echo_api/ruby-typhoeus/lib/openapi_client/models/test_query_style_deep_object_explode_true_object_all_of_query_object_parameter.rb
index 02afae09bce2..04a9bd521165 100644
--- a/samples/client/echo_api/ruby-typhoeus/lib/openapi_client/models/test_query_style_deep_object_explode_true_object_all_of_query_object_parameter.rb
+++ b/samples/client/echo_api/ruby-typhoeus/lib/openapi_client/models/test_query_style_deep_object_explode_true_object_all_of_query_object_parameter.rb
@@ -59,6 +59,16 @@ def self.openapi_nullable
       ])
     end
 
+    # Returns attribute type mapping
+    def self.acceptable_openapi_types
+      openapi_types
+    end
+
+    # Returns the nullable attributes
+    def self.acceptable_openapi_nullable
+      openapi_nullable
+    end
+
     # List of class defined in allOf (OpenAPI v3)
     def self.openapi_all_of
       [
@@ -144,18 +154,20 @@ def hash
     def self.build_from_hash(attributes)
       return nil unless attributes.is_a?(Hash)
       attributes = attributes.transform_keys(&:to_sym)
+      # include attributes inherited from allOf parents (the nearest declaration wins)
+      map = acceptable_attribute_map
       transformed_hash = {}
-      openapi_types.each_pair do |key, type|
-        if attributes.key?(attribute_map[key]) && attributes[attribute_map[key]].nil?
+      acceptable_openapi_types.each_pair do |key, type|
+        if attributes.key?(map[key]) && attributes[map[key]].nil?
           transformed_hash["#{key}"] = nil
         elsif type =~ /\AArray<(.*)>/i
           # check to ensure the input is an array given that the attribute
           # is documented as an array but the input is not
-          if attributes[attribute_map[key]].is_a?(Array)
-            transformed_hash["#{key}"] = attributes[attribute_map[key]].map { |v| _deserialize($1, v) }
+          if attributes[map[key]].is_a?(Array)
+            transformed_hash["#{key}"] = attributes[map[key]].map { |v| _deserialize($1, v) }
           end
-        elsif !attributes[attribute_map[key]].nil?
-          transformed_hash["#{key}"] = _deserialize(type, attributes[attribute_map[key]])
+        elsif !attributes[map[key]].nil?
+          transformed_hash["#{key}"] = _deserialize(type, attributes[map[key]])
         end
       end
       new(transformed_hash)
@@ -165,10 +177,11 @@ def self.build_from_hash(attributes)
     # @return [Hash] Returns the object in the form of hash
     def to_hash
       hash = {}
-      self.class.attribute_map.each_pair do |attr, param|
+      # include attributes inherited from allOf parents (the nearest declaration wins)
+      self.class.acceptable_attribute_map.each_pair do |attr, param|
         value = self.send(attr)
         if value.nil?
-          is_nullable = self.class.openapi_nullable.include?(attr)
+          is_nullable = self.class.acceptable_openapi_nullable.include?(attr)
           next if !is_nullable || (is_nullable && !instance_variable_defined?(:"@#{attr}"))
         end
 
diff --git a/samples/client/echo_api/ruby-typhoeus/lib/openapi_client/models/test_query_style_form_explode_true_array_string_query_object_parameter.rb b/samples/client/echo_api/ruby-typhoeus/lib/openapi_client/models/test_query_style_form_explode_true_array_string_query_object_parameter.rb
index fa9520a4f16c..3c67a8e0f2a9 100644
--- a/samples/client/echo_api/ruby-typhoeus/lib/openapi_client/models/test_query_style_form_explode_true_array_string_query_object_parameter.rb
+++ b/samples/client/echo_api/ruby-typhoeus/lib/openapi_client/models/test_query_style_form_explode_true_array_string_query_object_parameter.rb
@@ -47,6 +47,16 @@ def self.openapi_nullable
       ])
     end
 
+    # Returns attribute type mapping
+    def self.acceptable_openapi_types
+      openapi_types
+    end
+
+    # Returns the nullable attributes
+    def self.acceptable_openapi_nullable
+      openapi_nullable
+    end
+
     # Initializes the object
     # @param [Hash] attributes Model attributes in the form of hash
     def initialize(attributes = {})
@@ -111,18 +121,20 @@ def hash
     def self.build_from_hash(attributes)
       return nil unless attributes.is_a?(Hash)
       attributes = attributes.transform_keys(&:to_sym)
+      # include attributes inherited from allOf parents (the nearest declaration wins)
+      map = acceptable_attribute_map
       transformed_hash = {}
-      openapi_types.each_pair do |key, type|
-        if attributes.key?(attribute_map[key]) && attributes[attribute_map[key]].nil?
+      acceptable_openapi_types.each_pair do |key, type|
+        if attributes.key?(map[key]) && attributes[map[key]].nil?
           transformed_hash["#{key}"] = nil
         elsif type =~ /\AArray<(.*)>/i
           # check to ensure the input is an array given that the attribute
           # is documented as an array but the input is not
-          if attributes[attribute_map[key]].is_a?(Array)
-            transformed_hash["#{key}"] = attributes[attribute_map[key]].map { |v| _deserialize($1, v) }
+          if attributes[map[key]].is_a?(Array)
+            transformed_hash["#{key}"] = attributes[map[key]].map { |v| _deserialize($1, v) }
           end
-        elsif !attributes[attribute_map[key]].nil?
-          transformed_hash["#{key}"] = _deserialize(type, attributes[attribute_map[key]])
+        elsif !attributes[map[key]].nil?
+          transformed_hash["#{key}"] = _deserialize(type, attributes[map[key]])
         end
       end
       new(transformed_hash)
@@ -132,10 +144,11 @@ def self.build_from_hash(attributes)
     # @return [Hash] Returns the object in the form of hash
     def to_hash
       hash = {}
-      self.class.attribute_map.each_pair do |attr, param|
+      # include attributes inherited from allOf parents (the nearest declaration wins)
+      self.class.acceptable_attribute_map.each_pair do |attr, param|
         value = self.send(attr)
         if value.nil?
-          is_nullable = self.class.openapi_nullable.include?(attr)
+          is_nullable = self.class.acceptable_openapi_nullable.include?(attr)
           next if !is_nullable || (is_nullable && !instance_variable_defined?(:"@#{attr}"))
         end
 
diff --git a/samples/client/petstore/ruby-autoload/lib/petstore/models/additional_properties_class.rb b/samples/client/petstore/ruby-autoload/lib/petstore/models/additional_properties_class.rb
index 9b823593d156..a240cadf547e 100644
--- a/samples/client/petstore/ruby-autoload/lib/petstore/models/additional_properties_class.rb
+++ b/samples/client/petstore/ruby-autoload/lib/petstore/models/additional_properties_class.rb
@@ -51,6 +51,16 @@ def self.openapi_nullable
       ])
     end
 
+    # Returns attribute type mapping
+    def self.acceptable_openapi_types
+      openapi_types
+    end
+
+    # Returns the nullable attributes
+    def self.acceptable_openapi_nullable
+      openapi_nullable
+    end
+
     # Initializes the object
     # @param [Hash] attributes Model attributes in the form of hash
     def initialize(attributes = {})
@@ -122,18 +132,20 @@ def hash
     def self.build_from_hash(attributes)
       return nil unless attributes.is_a?(Hash)
       attributes = attributes.transform_keys(&:to_sym)
+      # include attributes inherited from allOf parents (the nearest declaration wins)
+      map = acceptable_attribute_map
       transformed_hash = {}
-      openapi_types.each_pair do |key, type|
-        if attributes.key?(attribute_map[key]) && attributes[attribute_map[key]].nil?
+      acceptable_openapi_types.each_pair do |key, type|
+        if attributes.key?(map[key]) && attributes[map[key]].nil?
           transformed_hash["#{key}"] = nil
         elsif type =~ /\AArray<(.*)>/i
           # check to ensure the input is an array given that the attribute
           # is documented as an array but the input is not
-          if attributes[attribute_map[key]].is_a?(Array)
-            transformed_hash["#{key}"] = attributes[attribute_map[key]].map { |v| _deserialize($1, v) }
+          if attributes[map[key]].is_a?(Array)
+            transformed_hash["#{key}"] = attributes[map[key]].map { |v| _deserialize($1, v) }
           end
-        elsif !attributes[attribute_map[key]].nil?
-          transformed_hash["#{key}"] = _deserialize(type, attributes[attribute_map[key]])
+        elsif !attributes[map[key]].nil?
+          transformed_hash["#{key}"] = _deserialize(type, attributes[map[key]])
         end
       end
       new(transformed_hash)
@@ -143,10 +155,11 @@ def self.build_from_hash(attributes)
     # @return [Hash] Returns the object in the form of hash
     def to_hash
       hash = {}
-      self.class.attribute_map.each_pair do |attr, param|
+      # include attributes inherited from allOf parents (the nearest declaration wins)
+      self.class.acceptable_attribute_map.each_pair do |attr, param|
         value = self.send(attr)
         if value.nil?
-          is_nullable = self.class.openapi_nullable.include?(attr)
+          is_nullable = self.class.acceptable_openapi_nullable.include?(attr)
           next if !is_nullable || (is_nullable && !instance_variable_defined?(:"@#{attr}"))
         end
 
diff --git a/samples/client/petstore/ruby-autoload/lib/petstore/models/all_of_with_single_ref.rb b/samples/client/petstore/ruby-autoload/lib/petstore/models/all_of_with_single_ref.rb
index 600c974fa1e5..9977e0212627 100644
--- a/samples/client/petstore/ruby-autoload/lib/petstore/models/all_of_with_single_ref.rb
+++ b/samples/client/petstore/ruby-autoload/lib/petstore/models/all_of_with_single_ref.rb
@@ -73,6 +73,16 @@ def self.openapi_nullable
       ])
     end
 
+    # Returns attribute type mapping
+    def self.acceptable_openapi_types
+      openapi_types
+    end
+
+    # Returns the nullable attributes
+    def self.acceptable_openapi_nullable
+      openapi_nullable
+    end
+
     # Initializes the object
     # @param [Hash] attributes Model attributes in the form of hash
     def initialize(attributes = {})
@@ -140,18 +150,20 @@ def hash
     def self.build_from_hash(attributes)
       return nil unless attributes.is_a?(Hash)
       attributes = attributes.transform_keys(&:to_sym)
+      # include attributes inherited from allOf parents (the nearest declaration wins)
+      map = acceptable_attribute_map
       transformed_hash = {}
-      openapi_types.each_pair do |key, type|
-        if attributes.key?(attribute_map[key]) && attributes[attribute_map[key]].nil?
+      acceptable_openapi_types.each_pair do |key, type|
+        if attributes.key?(map[key]) && attributes[map[key]].nil?
           transformed_hash["#{key}"] = nil
         elsif type =~ /\AArray<(.*)>/i
           # check to ensure the input is an array given that the attribute
           # is documented as an array but the input is not
-          if attributes[attribute_map[key]].is_a?(Array)
-            transformed_hash["#{key}"] = attributes[attribute_map[key]].map { |v| _deserialize($1, v) }
+          if attributes[map[key]].is_a?(Array)
+            transformed_hash["#{key}"] = attributes[map[key]].map { |v| _deserialize($1, v) }
           end
-        elsif !attributes[attribute_map[key]].nil?
-          transformed_hash["#{key}"] = _deserialize(type, attributes[attribute_map[key]])
+        elsif !attributes[map[key]].nil?
+          transformed_hash["#{key}"] = _deserialize(type, attributes[map[key]])
         end
       end
       new(transformed_hash)
@@ -161,10 +173,11 @@ def self.build_from_hash(attributes)
     # @return [Hash] Returns the object in the form of hash
     def to_hash
       hash = {}
-      self.class.attribute_map.each_pair do |attr, param|
+      # include attributes inherited from allOf parents (the nearest declaration wins)
+      self.class.acceptable_attribute_map.each_pair do |attr, param|
         value = self.send(attr)
         if value.nil?
-          is_nullable = self.class.openapi_nullable.include?(attr)
+          is_nullable = self.class.acceptable_openapi_nullable.include?(attr)
           next if !is_nullable || (is_nullable && !instance_variable_defined?(:"@#{attr}"))
         end
 
diff --git a/samples/client/petstore/ruby-autoload/lib/petstore/models/animal.rb b/samples/client/petstore/ruby-autoload/lib/petstore/models/animal.rb
index 21d89bccb837..b58dbb506d4e 100644
--- a/samples/client/petstore/ruby-autoload/lib/petstore/models/animal.rb
+++ b/samples/client/petstore/ruby-autoload/lib/petstore/models/animal.rb
@@ -51,6 +51,16 @@ def self.openapi_nullable
       ])
     end
 
+    # Returns attribute type mapping
+    def self.acceptable_openapi_types
+      openapi_types
+    end
+
+    # Returns the nullable attributes
+    def self.acceptable_openapi_nullable
+      openapi_nullable
+    end
+
     # discriminator's property name in OpenAPI v3
     def self.openapi_discriminator_name
       :'class_name'
@@ -142,18 +152,20 @@ def hash
     def self.build_from_hash(attributes)
       return nil unless attributes.is_a?(Hash)
       attributes = attributes.transform_keys(&:to_sym)
+      # include attributes inherited from allOf parents (the nearest declaration wins)
+      map = acceptable_attribute_map
       transformed_hash = {}
-      openapi_types.each_pair do |key, type|
-        if attributes.key?(attribute_map[key]) && attributes[attribute_map[key]].nil?
+      acceptable_openapi_types.each_pair do |key, type|
+        if attributes.key?(map[key]) && attributes[map[key]].nil?
           transformed_hash["#{key}"] = nil
         elsif type =~ /\AArray<(.*)>/i
           # check to ensure the input is an array given that the attribute
           # is documented as an array but the input is not
-          if attributes[attribute_map[key]].is_a?(Array)
-            transformed_hash["#{key}"] = attributes[attribute_map[key]].map { |v| _deserialize($1, v) }
+          if attributes[map[key]].is_a?(Array)
+            transformed_hash["#{key}"] = attributes[map[key]].map { |v| _deserialize($1, v) }
           end
-        elsif !attributes[attribute_map[key]].nil?
-          transformed_hash["#{key}"] = _deserialize(type, attributes[attribute_map[key]])
+        elsif !attributes[map[key]].nil?
+          transformed_hash["#{key}"] = _deserialize(type, attributes[map[key]])
         end
       end
       new(transformed_hash)
@@ -163,10 +175,11 @@ def self.build_from_hash(attributes)
     # @return [Hash] Returns the object in the form of hash
     def to_hash
       hash = {}
-      self.class.attribute_map.each_pair do |attr, param|
+      # include attributes inherited from allOf parents (the nearest declaration wins)
+      self.class.acceptable_attribute_map.each_pair do |attr, param|
         value = self.send(attr)
         if value.nil?
-          is_nullable = self.class.openapi_nullable.include?(attr)
+          is_nullable = self.class.acceptable_openapi_nullable.include?(attr)
           next if !is_nullable || (is_nullable && !instance_variable_defined?(:"@#{attr}"))
         end
 
diff --git a/samples/client/petstore/ruby-autoload/lib/petstore/models/api_response.rb b/samples/client/petstore/ruby-autoload/lib/petstore/models/api_response.rb
index bbbaf9358be2..6b8e2bf4005f 100644
--- a/samples/client/petstore/ruby-autoload/lib/petstore/models/api_response.rb
+++ b/samples/client/petstore/ruby-autoload/lib/petstore/models/api_response.rb
@@ -55,6 +55,16 @@ def self.openapi_nullable
       ])
     end
 
+    # Returns attribute type mapping
+    def self.acceptable_openapi_types
+      openapi_types
+    end
+
+    # Returns the nullable attributes
+    def self.acceptable_openapi_nullable
+      openapi_nullable
+    end
+
     # Initializes the object
     # @param [Hash] attributes Model attributes in the form of hash
     def initialize(attributes = {})
@@ -127,18 +137,20 @@ def hash
     def self.build_from_hash(attributes)
       return nil unless attributes.is_a?(Hash)
       attributes = attributes.transform_keys(&:to_sym)
+      # include attributes inherited from allOf parents (the nearest declaration wins)
+      map = acceptable_attribute_map
       transformed_hash = {}
-      openapi_types.each_pair do |key, type|
-        if attributes.key?(attribute_map[key]) && attributes[attribute_map[key]].nil?
+      acceptable_openapi_types.each_pair do |key, type|
+        if attributes.key?(map[key]) && attributes[map[key]].nil?
           transformed_hash["#{key}"] = nil
         elsif type =~ /\AArray<(.*)>/i
           # check to ensure the input is an array given that the attribute
           # is documented as an array but the input is not
-          if attributes[attribute_map[key]].is_a?(Array)
-            transformed_hash["#{key}"] = attributes[attribute_map[key]].map { |v| _deserialize($1, v) }
+          if attributes[map[key]].is_a?(Array)
+            transformed_hash["#{key}"] = attributes[map[key]].map { |v| _deserialize($1, v) }
           end
-        elsif !attributes[attribute_map[key]].nil?
-          transformed_hash["#{key}"] = _deserialize(type, attributes[attribute_map[key]])
+        elsif !attributes[map[key]].nil?
+          transformed_hash["#{key}"] = _deserialize(type, attributes[map[key]])
         end
       end
       new(transformed_hash)
@@ -148,10 +160,11 @@ def self.build_from_hash(attributes)
     # @return [Hash] Returns the object in the form of hash
     def to_hash
       hash = {}
-      self.class.attribute_map.each_pair do |attr, param|
+      # include attributes inherited from allOf parents (the nearest declaration wins)
+      self.class.acceptable_attribute_map.each_pair do |attr, param|
         value = self.send(attr)
         if value.nil?
-          is_nullable = self.class.openapi_nullable.include?(attr)
+          is_nullable = self.class.acceptable_openapi_nullable.include?(attr)
           next if !is_nullable || (is_nullable && !instance_variable_defined?(:"@#{attr}"))
         end
 
diff --git a/samples/client/petstore/ruby-autoload/lib/petstore/models/array_of_array_of_number_only.rb b/samples/client/petstore/ruby-autoload/lib/petstore/models/array_of_array_of_number_only.rb
index e20b1728d130..40b968094257 100644
--- a/samples/client/petstore/ruby-autoload/lib/petstore/models/array_of_array_of_number_only.rb
+++ b/samples/client/petstore/ruby-autoload/lib/petstore/models/array_of_array_of_number_only.rb
@@ -47,6 +47,16 @@ def self.openapi_nullable
       ])
     end
 
+    # Returns attribute type mapping
+    def self.acceptable_openapi_types
+      openapi_types
+    end
+
+    # Returns the nullable attributes
+    def self.acceptable_openapi_nullable
+      openapi_nullable
+    end
+
     # Initializes the object
     # @param [Hash] attributes Model attributes in the form of hash
     def initialize(attributes = {})
@@ -111,18 +121,20 @@ def hash
     def self.build_from_hash(attributes)
       return nil unless attributes.is_a?(Hash)
       attributes = attributes.transform_keys(&:to_sym)
+      # include attributes inherited from allOf parents (the nearest declaration wins)
+      map = acceptable_attribute_map
       transformed_hash = {}
-      openapi_types.each_pair do |key, type|
-        if attributes.key?(attribute_map[key]) && attributes[attribute_map[key]].nil?
+      acceptable_openapi_types.each_pair do |key, type|
+        if attributes.key?(map[key]) && attributes[map[key]].nil?
           transformed_hash["#{key}"] = nil
         elsif type =~ /\AArray<(.*)>/i
           # check to ensure the input is an array given that the attribute
           # is documented as an array but the input is not
-          if attributes[attribute_map[key]].is_a?(Array)
-            transformed_hash["#{key}"] = attributes[attribute_map[key]].map { |v| _deserialize($1, v) }
+          if attributes[map[key]].is_a?(Array)
+            transformed_hash["#{key}"] = attributes[map[key]].map { |v| _deserialize($1, v) }
           end
-        elsif !attributes[attribute_map[key]].nil?
-          transformed_hash["#{key}"] = _deserialize(type, attributes[attribute_map[key]])
+        elsif !attributes[map[key]].nil?
+          transformed_hash["#{key}"] = _deserialize(type, attributes[map[key]])
         end
       end
       new(transformed_hash)
@@ -132,10 +144,11 @@ def self.build_from_hash(attributes)
     # @return [Hash] Returns the object in the form of hash
     def to_hash
       hash = {}
-      self.class.attribute_map.each_pair do |attr, param|
+      # include attributes inherited from allOf parents (the nearest declaration wins)
+      self.class.acceptable_attribute_map.each_pair do |attr, param|
         value = self.send(attr)
         if value.nil?
-          is_nullable = self.class.openapi_nullable.include?(attr)
+          is_nullable = self.class.acceptable_openapi_nullable.include?(attr)
           next if !is_nullable || (is_nullable && !instance_variable_defined?(:"@#{attr}"))
         end
 
diff --git a/samples/client/petstore/ruby-autoload/lib/petstore/models/array_of_number_only.rb b/samples/client/petstore/ruby-autoload/lib/petstore/models/array_of_number_only.rb
index 63890ff64424..6b9bc3627785 100644
--- a/samples/client/petstore/ruby-autoload/lib/petstore/models/array_of_number_only.rb
+++ b/samples/client/petstore/ruby-autoload/lib/petstore/models/array_of_number_only.rb
@@ -47,6 +47,16 @@ def self.openapi_nullable
       ])
     end
 
+    # Returns attribute type mapping
+    def self.acceptable_openapi_types
+      openapi_types
+    end
+
+    # Returns the nullable attributes
+    def self.acceptable_openapi_nullable
+      openapi_nullable
+    end
+
     # Initializes the object
     # @param [Hash] attributes Model attributes in the form of hash
     def initialize(attributes = {})
@@ -111,18 +121,20 @@ def hash
     def self.build_from_hash(attributes)
       return nil unless attributes.is_a?(Hash)
       attributes = attributes.transform_keys(&:to_sym)
+      # include attributes inherited from allOf parents (the nearest declaration wins)
+      map = acceptable_attribute_map
       transformed_hash = {}
-      openapi_types.each_pair do |key, type|
-        if attributes.key?(attribute_map[key]) && attributes[attribute_map[key]].nil?
+      acceptable_openapi_types.each_pair do |key, type|
+        if attributes.key?(map[key]) && attributes[map[key]].nil?
           transformed_hash["#{key}"] = nil
         elsif type =~ /\AArray<(.*)>/i
           # check to ensure the input is an array given that the attribute
           # is documented as an array but the input is not
-          if attributes[attribute_map[key]].is_a?(Array)
-            transformed_hash["#{key}"] = attributes[attribute_map[key]].map { |v| _deserialize($1, v) }
+          if attributes[map[key]].is_a?(Array)
+            transformed_hash["#{key}"] = attributes[map[key]].map { |v| _deserialize($1, v) }
           end
-        elsif !attributes[attribute_map[key]].nil?
-          transformed_hash["#{key}"] = _deserialize(type, attributes[attribute_map[key]])
+        elsif !attributes[map[key]].nil?
+          transformed_hash["#{key}"] = _deserialize(type, attributes[map[key]])
         end
       end
       new(transformed_hash)
@@ -132,10 +144,11 @@ def self.build_from_hash(attributes)
     # @return [Hash] Returns the object in the form of hash
     def to_hash
       hash = {}
-      self.class.attribute_map.each_pair do |attr, param|
+      # include attributes inherited from allOf parents (the nearest declaration wins)
+      self.class.acceptable_attribute_map.each_pair do |attr, param|
         value = self.send(attr)
         if value.nil?
-          is_nullable = self.class.openapi_nullable.include?(attr)
+          is_nullable = self.class.acceptable_openapi_nullable.include?(attr)
           next if !is_nullable || (is_nullable && !instance_variable_defined?(:"@#{attr}"))
         end
 
diff --git a/samples/client/petstore/ruby-autoload/lib/petstore/models/array_test.rb b/samples/client/petstore/ruby-autoload/lib/petstore/models/array_test.rb
index c74060151e07..fc5e9d297766 100644
--- a/samples/client/petstore/ruby-autoload/lib/petstore/models/array_test.rb
+++ b/samples/client/petstore/ruby-autoload/lib/petstore/models/array_test.rb
@@ -55,6 +55,16 @@ def self.openapi_nullable
       ])
     end
 
+    # Returns attribute type mapping
+    def self.acceptable_openapi_types
+      openapi_types
+    end
+
+    # Returns the nullable attributes
+    def self.acceptable_openapi_nullable
+      openapi_nullable
+    end
+
     # Initializes the object
     # @param [Hash] attributes Model attributes in the form of hash
     def initialize(attributes = {})
@@ -161,18 +171,20 @@ def hash
     def self.build_from_hash(attributes)
       return nil unless attributes.is_a?(Hash)
       attributes = attributes.transform_keys(&:to_sym)
+      # include attributes inherited from allOf parents (the nearest declaration wins)
+      map = acceptable_attribute_map
       transformed_hash = {}
-      openapi_types.each_pair do |key, type|
-        if attributes.key?(attribute_map[key]) && attributes[attribute_map[key]].nil?
+      acceptable_openapi_types.each_pair do |key, type|
+        if attributes.key?(map[key]) && attributes[map[key]].nil?
           transformed_hash["#{key}"] = nil
         elsif type =~ /\AArray<(.*)>/i
           # check to ensure the input is an array given that the attribute
           # is documented as an array but the input is not
-          if attributes[attribute_map[key]].is_a?(Array)
-            transformed_hash["#{key}"] = attributes[attribute_map[key]].map { |v| _deserialize($1, v) }
+          if attributes[map[key]].is_a?(Array)
+            transformed_hash["#{key}"] = attributes[map[key]].map { |v| _deserialize($1, v) }
           end
-        elsif !attributes[attribute_map[key]].nil?
-          transformed_hash["#{key}"] = _deserialize(type, attributes[attribute_map[key]])
+        elsif !attributes[map[key]].nil?
+          transformed_hash["#{key}"] = _deserialize(type, attributes[map[key]])
         end
       end
       new(transformed_hash)
@@ -182,10 +194,11 @@ def self.build_from_hash(attributes)
     # @return [Hash] Returns the object in the form of hash
     def to_hash
       hash = {}
-      self.class.attribute_map.each_pair do |attr, param|
+      # include attributes inherited from allOf parents (the nearest declaration wins)
+      self.class.acceptable_attribute_map.each_pair do |attr, param|
         value = self.send(attr)
         if value.nil?
-          is_nullable = self.class.openapi_nullable.include?(attr)
+          is_nullable = self.class.acceptable_openapi_nullable.include?(attr)
           next if !is_nullable || (is_nullable && !instance_variable_defined?(:"@#{attr}"))
         end
 
diff --git a/samples/client/petstore/ruby-autoload/lib/petstore/models/capitalization.rb b/samples/client/petstore/ruby-autoload/lib/petstore/models/capitalization.rb
index e0bbeb211eb3..9031ca3f7d51 100644
--- a/samples/client/petstore/ruby-autoload/lib/petstore/models/capitalization.rb
+++ b/samples/client/petstore/ruby-autoload/lib/petstore/models/capitalization.rb
@@ -68,6 +68,16 @@ def self.openapi_nullable
       ])
     end
 
+    # Returns attribute type mapping
+    def self.acceptable_openapi_types
+      openapi_types
+    end
+
+    # Returns the nullable attributes
+    def self.acceptable_openapi_nullable
+      openapi_nullable
+    end
+
     # Initializes the object
     # @param [Hash] attributes Model attributes in the form of hash
     def initialize(attributes = {})
@@ -155,18 +165,20 @@ def hash
     def self.build_from_hash(attributes)
       return nil unless attributes.is_a?(Hash)
       attributes = attributes.transform_keys(&:to_sym)
+      # include attributes inherited from allOf parents (the nearest declaration wins)
+      map = acceptable_attribute_map
       transformed_hash = {}
-      openapi_types.each_pair do |key, type|
-        if attributes.key?(attribute_map[key]) && attributes[attribute_map[key]].nil?
+      acceptable_openapi_types.each_pair do |key, type|
+        if attributes.key?(map[key]) && attributes[map[key]].nil?
           transformed_hash["#{key}"] = nil
         elsif type =~ /\AArray<(.*)>/i
           # check to ensure the input is an array given that the attribute
           # is documented as an array but the input is not
-          if attributes[attribute_map[key]].is_a?(Array)
-            transformed_hash["#{key}"] = attributes[attribute_map[key]].map { |v| _deserialize($1, v) }
+          if attributes[map[key]].is_a?(Array)
+            transformed_hash["#{key}"] = attributes[map[key]].map { |v| _deserialize($1, v) }
           end
-        elsif !attributes[attribute_map[key]].nil?
-          transformed_hash["#{key}"] = _deserialize(type, attributes[attribute_map[key]])
+        elsif !attributes[map[key]].nil?
+          transformed_hash["#{key}"] = _deserialize(type, attributes[map[key]])
         end
       end
       new(transformed_hash)
@@ -176,10 +188,11 @@ def self.build_from_hash(attributes)
     # @return [Hash] Returns the object in the form of hash
     def to_hash
       hash = {}
-      self.class.attribute_map.each_pair do |attr, param|
+      # include attributes inherited from allOf parents (the nearest declaration wins)
+      self.class.acceptable_attribute_map.each_pair do |attr, param|
         value = self.send(attr)
         if value.nil?
-          is_nullable = self.class.openapi_nullable.include?(attr)
+          is_nullable = self.class.acceptable_openapi_nullable.include?(attr)
           next if !is_nullable || (is_nullable && !instance_variable_defined?(:"@#{attr}"))
         end
 
diff --git a/samples/client/petstore/ruby-autoload/lib/petstore/models/cat.rb b/samples/client/petstore/ruby-autoload/lib/petstore/models/cat.rb
index a84dc5038bef..a1f3de5272b6 100644
--- a/samples/client/petstore/ruby-autoload/lib/petstore/models/cat.rb
+++ b/samples/client/petstore/ruby-autoload/lib/petstore/models/cat.rb
@@ -47,6 +47,16 @@ def self.openapi_nullable
       ])
     end
 
+    # Returns attribute type mapping, including the ones defined in its parent(s)
+    def self.acceptable_openapi_types
+      superclass.acceptable_openapi_types.merge(openapi_types)
+    end
+
+    # Returns the nullable attributes, including the ones defined in its parent(s) that it does not redeclare
+    def self.acceptable_openapi_nullable
+      (superclass.acceptable_openapi_nullable - attribute_map.keys) | openapi_nullable
+    end
+
     # List of class defined in allOf (OpenAPI v3)
     def self.openapi_all_of
       [
@@ -118,20 +128,21 @@ def hash
     # @return [Object] Returns the model itself
     def self.build_from_hash(attributes)
       return nil unless attributes.is_a?(Hash)
-      super(attributes)
       attributes = attributes.transform_keys(&:to_sym)
+      # include attributes inherited from allOf parents (the nearest declaration wins)
+      map = acceptable_attribute_map
       transformed_hash = {}
-      openapi_types.each_pair do |key, type|
-        if attributes.key?(attribute_map[key]) && attributes[attribute_map[key]].nil?
+      acceptable_openapi_types.each_pair do |key, type|
+        if attributes.key?(map[key]) && attributes[map[key]].nil?
           transformed_hash["#{key}"] = nil
         elsif type =~ /\AArray<(.*)>/i
           # check to ensure the input is an array given that the attribute
           # is documented as an array but the input is not
-          if attributes[attribute_map[key]].is_a?(Array)
-            transformed_hash["#{key}"] = attributes[attribute_map[key]].map { |v| _deserialize($1, v) }
+          if attributes[map[key]].is_a?(Array)
+            transformed_hash["#{key}"] = attributes[map[key]].map { |v| _deserialize($1, v) }
           end
-        elsif !attributes[attribute_map[key]].nil?
-          transformed_hash["#{key}"] = _deserialize(type, attributes[attribute_map[key]])
+        elsif !attributes[map[key]].nil?
+          transformed_hash["#{key}"] = _deserialize(type, attributes[map[key]])
         end
       end
       new(transformed_hash)
@@ -140,11 +151,12 @@ def self.build_from_hash(attributes)
     # Returns the object in the form of hash
     # @return [Hash] Returns the object in the form of hash
     def to_hash
-      hash = super
-      self.class.attribute_map.each_pair do |attr, param|
+      hash = {}
+      # include attributes inherited from allOf parents (the nearest declaration wins)
+      self.class.acceptable_attribute_map.each_pair do |attr, param|
         value = self.send(attr)
         if value.nil?
-          is_nullable = self.class.openapi_nullable.include?(attr)
+          is_nullable = self.class.acceptable_openapi_nullable.include?(attr)
           next if !is_nullable || (is_nullable && !instance_variable_defined?(:"@#{attr}"))
         end
 
diff --git a/samples/client/petstore/ruby-autoload/lib/petstore/models/category.rb b/samples/client/petstore/ruby-autoload/lib/petstore/models/category.rb
index 2f2b7f1a5785..a5af1c3f9acc 100644
--- a/samples/client/petstore/ruby-autoload/lib/petstore/models/category.rb
+++ b/samples/client/petstore/ruby-autoload/lib/petstore/models/category.rb
@@ -51,6 +51,16 @@ def self.openapi_nullable
       ])
     end
 
+    # Returns attribute type mapping
+    def self.acceptable_openapi_types
+      openapi_types
+    end
+
+    # Returns the nullable attributes
+    def self.acceptable_openapi_nullable
+      openapi_nullable
+    end
+
     # Initializes the object
     # @param [Hash] attributes Model attributes in the form of hash
     def initialize(attributes = {})
@@ -135,18 +145,20 @@ def hash
     def self.build_from_hash(attributes)
       return nil unless attributes.is_a?(Hash)
       attributes = attributes.transform_keys(&:to_sym)
+      # include attributes inherited from allOf parents (the nearest declaration wins)
+      map = acceptable_attribute_map
       transformed_hash = {}
-      openapi_types.each_pair do |key, type|
-        if attributes.key?(attribute_map[key]) && attributes[attribute_map[key]].nil?
+      acceptable_openapi_types.each_pair do |key, type|
+        if attributes.key?(map[key]) && attributes[map[key]].nil?
           transformed_hash["#{key}"] = nil
         elsif type =~ /\AArray<(.*)>/i
           # check to ensure the input is an array given that the attribute
           # is documented as an array but the input is not
-          if attributes[attribute_map[key]].is_a?(Array)
-            transformed_hash["#{key}"] = attributes[attribute_map[key]].map { |v| _deserialize($1, v) }
+          if attributes[map[key]].is_a?(Array)
+            transformed_hash["#{key}"] = attributes[map[key]].map { |v| _deserialize($1, v) }
           end
-        elsif !attributes[attribute_map[key]].nil?
-          transformed_hash["#{key}"] = _deserialize(type, attributes[attribute_map[key]])
+        elsif !attributes[map[key]].nil?
+          transformed_hash["#{key}"] = _deserialize(type, attributes[map[key]])
         end
       end
       new(transformed_hash)
@@ -156,10 +168,11 @@ def self.build_from_hash(attributes)
     # @return [Hash] Returns the object in the form of hash
     def to_hash
       hash = {}
-      self.class.attribute_map.each_pair do |attr, param|
+      # include attributes inherited from allOf parents (the nearest declaration wins)
+      self.class.acceptable_attribute_map.each_pair do |attr, param|
         value = self.send(attr)
         if value.nil?
-          is_nullable = self.class.openapi_nullable.include?(attr)
+          is_nullable = self.class.acceptable_openapi_nullable.include?(attr)
           next if !is_nullable || (is_nullable && !instance_variable_defined?(:"@#{attr}"))
         end
 
diff --git a/samples/client/petstore/ruby-autoload/lib/petstore/models/child_with_nullable.rb b/samples/client/petstore/ruby-autoload/lib/petstore/models/child_with_nullable.rb
index a7c86c864e6e..1e4671c79c42 100644
--- a/samples/client/petstore/ruby-autoload/lib/petstore/models/child_with_nullable.rb
+++ b/samples/client/petstore/ruby-autoload/lib/petstore/models/child_with_nullable.rb
@@ -69,6 +69,16 @@ def self.openapi_nullable
       ])
     end
 
+    # Returns attribute type mapping, including the ones defined in its parent(s)
+    def self.acceptable_openapi_types
+      superclass.acceptable_openapi_types.merge(openapi_types)
+    end
+
+    # Returns the nullable attributes, including the ones defined in its parent(s) that it does not redeclare
+    def self.acceptable_openapi_nullable
+      (superclass.acceptable_openapi_nullable - attribute_map.keys) | openapi_nullable
+    end
+
     # List of class defined in allOf (OpenAPI v3)
     def self.openapi_all_of
       [
@@ -140,20 +150,21 @@ def hash
     # @return [Object] Returns the model itself
     def self.build_from_hash(attributes)
       return nil unless attributes.is_a?(Hash)
-      super(attributes)
       attributes = attributes.transform_keys(&:to_sym)
+      # include attributes inherited from allOf parents (the nearest declaration wins)
+      map = acceptable_attribute_map
       transformed_hash = {}
-      openapi_types.each_pair do |key, type|
-        if attributes.key?(attribute_map[key]) && attributes[attribute_map[key]].nil?
+      acceptable_openapi_types.each_pair do |key, type|
+        if attributes.key?(map[key]) && attributes[map[key]].nil?
           transformed_hash["#{key}"] = nil
         elsif type =~ /\AArray<(.*)>/i
           # check to ensure the input is an array given that the attribute
           # is documented as an array but the input is not
-          if attributes[attribute_map[key]].is_a?(Array)
-            transformed_hash["#{key}"] = attributes[attribute_map[key]].map { |v| _deserialize($1, v) }
+          if attributes[map[key]].is_a?(Array)
+            transformed_hash["#{key}"] = attributes[map[key]].map { |v| _deserialize($1, v) }
           end
-        elsif !attributes[attribute_map[key]].nil?
-          transformed_hash["#{key}"] = _deserialize(type, attributes[attribute_map[key]])
+        elsif !attributes[map[key]].nil?
+          transformed_hash["#{key}"] = _deserialize(type, attributes[map[key]])
         end
       end
       new(transformed_hash)
@@ -162,11 +173,12 @@ def self.build_from_hash(attributes)
     # Returns the object in the form of hash
     # @return [Hash] Returns the object in the form of hash
     def to_hash
-      hash = super
-      self.class.attribute_map.each_pair do |attr, param|
+      hash = {}
+      # include attributes inherited from allOf parents (the nearest declaration wins)
+      self.class.acceptable_attribute_map.each_pair do |attr, param|
         value = self.send(attr)
         if value.nil?
-          is_nullable = self.class.openapi_nullable.include?(attr)
+          is_nullable = self.class.acceptable_openapi_nullable.include?(attr)
           next if !is_nullable || (is_nullable && !instance_variable_defined?(:"@#{attr}"))
         end
 
diff --git a/samples/client/petstore/ruby-autoload/lib/petstore/models/class_model.rb b/samples/client/petstore/ruby-autoload/lib/petstore/models/class_model.rb
index fafd11df773a..4e611ee27f3e 100644
--- a/samples/client/petstore/ruby-autoload/lib/petstore/models/class_model.rb
+++ b/samples/client/petstore/ruby-autoload/lib/petstore/models/class_model.rb
@@ -48,6 +48,16 @@ def self.openapi_nullable
       ])
     end
 
+    # Returns attribute type mapping
+    def self.acceptable_openapi_types
+      openapi_types
+    end
+
+    # Returns the nullable attributes
+    def self.acceptable_openapi_nullable
+      openapi_nullable
+    end
+
     # Initializes the object
     # @param [Hash] attributes Model attributes in the form of hash
     def initialize(attributes = {})
@@ -110,18 +120,20 @@ def hash
     def self.build_from_hash(attributes)
       return nil unless attributes.is_a?(Hash)
       attributes = attributes.transform_keys(&:to_sym)
+      # include attributes inherited from allOf parents (the nearest declaration wins)
+      map = acceptable_attribute_map
       transformed_hash = {}
-      openapi_types.each_pair do |key, type|
-        if attributes.key?(attribute_map[key]) && attributes[attribute_map[key]].nil?
+      acceptable_openapi_types.each_pair do |key, type|
+        if attributes.key?(map[key]) && attributes[map[key]].nil?
           transformed_hash["#{key}"] = nil
         elsif type =~ /\AArray<(.*)>/i
           # check to ensure the input is an array given that the attribute
           # is documented as an array but the input is not
-          if attributes[attribute_map[key]].is_a?(Array)
-            transformed_hash["#{key}"] = attributes[attribute_map[key]].map { |v| _deserialize($1, v) }
+          if attributes[map[key]].is_a?(Array)
+            transformed_hash["#{key}"] = attributes[map[key]].map { |v| _deserialize($1, v) }
           end
-        elsif !attributes[attribute_map[key]].nil?
-          transformed_hash["#{key}"] = _deserialize(type, attributes[attribute_map[key]])
+        elsif !attributes[map[key]].nil?
+          transformed_hash["#{key}"] = _deserialize(type, attributes[map[key]])
         end
       end
       new(transformed_hash)
@@ -131,10 +143,11 @@ def self.build_from_hash(attributes)
     # @return [Hash] Returns the object in the form of hash
     def to_hash
       hash = {}
-      self.class.attribute_map.each_pair do |attr, param|
+      # include attributes inherited from allOf parents (the nearest declaration wins)
+      self.class.acceptable_attribute_map.each_pair do |attr, param|
         value = self.send(attr)
         if value.nil?
-          is_nullable = self.class.openapi_nullable.include?(attr)
+          is_nullable = self.class.acceptable_openapi_nullable.include?(attr)
           next if !is_nullable || (is_nullable && !instance_variable_defined?(:"@#{attr}"))
         end
 
diff --git a/samples/client/petstore/ruby-autoload/lib/petstore/models/client.rb b/samples/client/petstore/ruby-autoload/lib/petstore/models/client.rb
index a349b7251d7b..f775d0f1d542 100644
--- a/samples/client/petstore/ruby-autoload/lib/petstore/models/client.rb
+++ b/samples/client/petstore/ruby-autoload/lib/petstore/models/client.rb
@@ -47,6 +47,16 @@ def self.openapi_nullable
       ])
     end
 
+    # Returns attribute type mapping
+    def self.acceptable_openapi_types
+      openapi_types
+    end
+
+    # Returns the nullable attributes
+    def self.acceptable_openapi_nullable
+      openapi_nullable
+    end
+
     # Initializes the object
     # @param [Hash] attributes Model attributes in the form of hash
     def initialize(attributes = {})
@@ -109,18 +119,20 @@ def hash
     def self.build_from_hash(attributes)
       return nil unless attributes.is_a?(Hash)
       attributes = attributes.transform_keys(&:to_sym)
+      # include attributes inherited from allOf parents (the nearest declaration wins)
+      map = acceptable_attribute_map
       transformed_hash = {}
-      openapi_types.each_pair do |key, type|
-        if attributes.key?(attribute_map[key]) && attributes[attribute_map[key]].nil?
+      acceptable_openapi_types.each_pair do |key, type|
+        if attributes.key?(map[key]) && attributes[map[key]].nil?
           transformed_hash["#{key}"] = nil
         elsif type =~ /\AArray<(.*)>/i
           # check to ensure the input is an array given that the attribute
           # is documented as an array but the input is not
-          if attributes[attribute_map[key]].is_a?(Array)
-            transformed_hash["#{key}"] = attributes[attribute_map[key]].map { |v| _deserialize($1, v) }
+          if attributes[map[key]].is_a?(Array)
+            transformed_hash["#{key}"] = attributes[map[key]].map { |v| _deserialize($1, v) }
           end
-        elsif !attributes[attribute_map[key]].nil?
-          transformed_hash["#{key}"] = _deserialize(type, attributes[attribute_map[key]])
+        elsif !attributes[map[key]].nil?
+          transformed_hash["#{key}"] = _deserialize(type, attributes[map[key]])
         end
       end
       new(transformed_hash)
@@ -130,10 +142,11 @@ def self.build_from_hash(attributes)
     # @return [Hash] Returns the object in the form of hash
     def to_hash
       hash = {}
-      self.class.attribute_map.each_pair do |attr, param|
+      # include attributes inherited from allOf parents (the nearest declaration wins)
+      self.class.acceptable_attribute_map.each_pair do |attr, param|
         value = self.send(attr)
         if value.nil?
-          is_nullable = self.class.openapi_nullable.include?(attr)
+          is_nullable = self.class.acceptable_openapi_nullable.include?(attr)
           next if !is_nullable || (is_nullable && !instance_variable_defined?(:"@#{attr}"))
         end
 
diff --git a/samples/client/petstore/ruby-autoload/lib/petstore/models/deprecated_object.rb b/samples/client/petstore/ruby-autoload/lib/petstore/models/deprecated_object.rb
index 9f1ee6720cab..bdc86013c848 100644
--- a/samples/client/petstore/ruby-autoload/lib/petstore/models/deprecated_object.rb
+++ b/samples/client/petstore/ruby-autoload/lib/petstore/models/deprecated_object.rb
@@ -47,6 +47,16 @@ def self.openapi_nullable
       ])
     end
 
+    # Returns attribute type mapping
+    def self.acceptable_openapi_types
+      openapi_types
+    end
+
+    # Returns the nullable attributes
+    def self.acceptable_openapi_nullable
+      openapi_nullable
+    end
+
     # Initializes the object
     # @param [Hash] attributes Model attributes in the form of hash
     def initialize(attributes = {})
@@ -109,18 +119,20 @@ def hash
     def self.build_from_hash(attributes)
       return nil unless attributes.is_a?(Hash)
       attributes = attributes.transform_keys(&:to_sym)
+      # include attributes inherited from allOf parents (the nearest declaration wins)
+      map = acceptable_attribute_map
       transformed_hash = {}
-      openapi_types.each_pair do |key, type|
-        if attributes.key?(attribute_map[key]) && attributes[attribute_map[key]].nil?
+      acceptable_openapi_types.each_pair do |key, type|
+        if attributes.key?(map[key]) && attributes[map[key]].nil?
           transformed_hash["#{key}"] = nil
         elsif type =~ /\AArray<(.*)>/i
           # check to ensure the input is an array given that the attribute
           # is documented as an array but the input is not
-          if attributes[attribute_map[key]].is_a?(Array)
-            transformed_hash["#{key}"] = attributes[attribute_map[key]].map { |v| _deserialize($1, v) }
+          if attributes[map[key]].is_a?(Array)
+            transformed_hash["#{key}"] = attributes[map[key]].map { |v| _deserialize($1, v) }
           end
-        elsif !attributes[attribute_map[key]].nil?
-          transformed_hash["#{key}"] = _deserialize(type, attributes[attribute_map[key]])
+        elsif !attributes[map[key]].nil?
+          transformed_hash["#{key}"] = _deserialize(type, attributes[map[key]])
         end
       end
       new(transformed_hash)
@@ -130,10 +142,11 @@ def self.build_from_hash(attributes)
     # @return [Hash] Returns the object in the form of hash
     def to_hash
       hash = {}
-      self.class.attribute_map.each_pair do |attr, param|
+      # include attributes inherited from allOf parents (the nearest declaration wins)
+      self.class.acceptable_attribute_map.each_pair do |attr, param|
         value = self.send(attr)
         if value.nil?
-          is_nullable = self.class.openapi_nullable.include?(attr)
+          is_nullable = self.class.acceptable_openapi_nullable.include?(attr)
           next if !is_nullable || (is_nullable && !instance_variable_defined?(:"@#{attr}"))
         end
 
diff --git a/samples/client/petstore/ruby-autoload/lib/petstore/models/dog.rb b/samples/client/petstore/ruby-autoload/lib/petstore/models/dog.rb
index 522e1a72f47e..2e8f95136f9a 100644
--- a/samples/client/petstore/ruby-autoload/lib/petstore/models/dog.rb
+++ b/samples/client/petstore/ruby-autoload/lib/petstore/models/dog.rb
@@ -47,6 +47,16 @@ def self.openapi_nullable
       ])
     end
 
+    # Returns attribute type mapping, including the ones defined in its parent(s)
+    def self.acceptable_openapi_types
+      superclass.acceptable_openapi_types.merge(openapi_types)
+    end
+
+    # Returns the nullable attributes, including the ones defined in its parent(s) that it does not redeclare
+    def self.acceptable_openapi_nullable
+      (superclass.acceptable_openapi_nullable - attribute_map.keys) | openapi_nullable
+    end
+
     # List of class defined in allOf (OpenAPI v3)
     def self.openapi_all_of
       [
@@ -118,20 +128,21 @@ def hash
     # @return [Object] Returns the model itself
     def self.build_from_hash(attributes)
       return nil unless attributes.is_a?(Hash)
-      super(attributes)
       attributes = attributes.transform_keys(&:to_sym)
+      # include attributes inherited from allOf parents (the nearest declaration wins)
+      map = acceptable_attribute_map
       transformed_hash = {}
-      openapi_types.each_pair do |key, type|
-        if attributes.key?(attribute_map[key]) && attributes[attribute_map[key]].nil?
+      acceptable_openapi_types.each_pair do |key, type|
+        if attributes.key?(map[key]) && attributes[map[key]].nil?
           transformed_hash["#{key}"] = nil
         elsif type =~ /\AArray<(.*)>/i
           # check to ensure the input is an array given that the attribute
           # is documented as an array but the input is not
-          if attributes[attribute_map[key]].is_a?(Array)
-            transformed_hash["#{key}"] = attributes[attribute_map[key]].map { |v| _deserialize($1, v) }
+          if attributes[map[key]].is_a?(Array)
+            transformed_hash["#{key}"] = attributes[map[key]].map { |v| _deserialize($1, v) }
           end
-        elsif !attributes[attribute_map[key]].nil?
-          transformed_hash["#{key}"] = _deserialize(type, attributes[attribute_map[key]])
+        elsif !attributes[map[key]].nil?
+          transformed_hash["#{key}"] = _deserialize(type, attributes[map[key]])
         end
       end
       new(transformed_hash)
@@ -140,11 +151,12 @@ def self.build_from_hash(attributes)
     # Returns the object in the form of hash
     # @return [Hash] Returns the object in the form of hash
     def to_hash
-      hash = super
-      self.class.attribute_map.each_pair do |attr, param|
+      hash = {}
+      # include attributes inherited from allOf parents (the nearest declaration wins)
+      self.class.acceptable_attribute_map.each_pair do |attr, param|
         value = self.send(attr)
         if value.nil?
-          is_nullable = self.class.openapi_nullable.include?(attr)
+          is_nullable = self.class.acceptable_openapi_nullable.include?(attr)
           next if !is_nullable || (is_nullable && !instance_variable_defined?(:"@#{attr}"))
         end
 
diff --git a/samples/client/petstore/ruby-autoload/lib/petstore/models/enum_arrays.rb b/samples/client/petstore/ruby-autoload/lib/petstore/models/enum_arrays.rb
index 1f7c48bf859b..8058a6ac60bb 100644
--- a/samples/client/petstore/ruby-autoload/lib/petstore/models/enum_arrays.rb
+++ b/samples/client/petstore/ruby-autoload/lib/petstore/models/enum_arrays.rb
@@ -73,6 +73,16 @@ def self.openapi_nullable
       ])
     end
 
+    # Returns attribute type mapping
+    def self.acceptable_openapi_types
+      openapi_types
+    end
+
+    # Returns the nullable attributes
+    def self.acceptable_openapi_nullable
+      openapi_nullable
+    end
+
     # Initializes the object
     # @param [Hash] attributes Model attributes in the form of hash
     def initialize(attributes = {})
@@ -154,18 +164,20 @@ def hash
     def self.build_from_hash(attributes)
       return nil unless attributes.is_a?(Hash)
       attributes = attributes.transform_keys(&:to_sym)
+      # include attributes inherited from allOf parents (the nearest declaration wins)
+      map = acceptable_attribute_map
       transformed_hash = {}
-      openapi_types.each_pair do |key, type|
-        if attributes.key?(attribute_map[key]) && attributes[attribute_map[key]].nil?
+      acceptable_openapi_types.each_pair do |key, type|
+        if attributes.key?(map[key]) && attributes[map[key]].nil?
           transformed_hash["#{key}"] = nil
         elsif type =~ /\AArray<(.*)>/i
           # check to ensure the input is an array given that the attribute
           # is documented as an array but the input is not
-          if attributes[attribute_map[key]].is_a?(Array)
-            transformed_hash["#{key}"] = attributes[attribute_map[key]].map { |v| _deserialize($1, v) }
+          if attributes[map[key]].is_a?(Array)
+            transformed_hash["#{key}"] = attributes[map[key]].map { |v| _deserialize($1, v) }
           end
-        elsif !attributes[attribute_map[key]].nil?
-          transformed_hash["#{key}"] = _deserialize(type, attributes[attribute_map[key]])
+        elsif !attributes[map[key]].nil?
+          transformed_hash["#{key}"] = _deserialize(type, attributes[map[key]])
         end
       end
       new(transformed_hash)
@@ -175,10 +187,11 @@ def self.build_from_hash(attributes)
     # @return [Hash] Returns the object in the form of hash
     def to_hash
       hash = {}
-      self.class.attribute_map.each_pair do |attr, param|
+      # include attributes inherited from allOf parents (the nearest declaration wins)
+      self.class.acceptable_attribute_map.each_pair do |attr, param|
         value = self.send(attr)
         if value.nil?
-          is_nullable = self.class.openapi_nullable.include?(attr)
+          is_nullable = self.class.acceptable_openapi_nullable.include?(attr)
           next if !is_nullable || (is_nullable && !instance_variable_defined?(:"@#{attr}"))
         end
 
diff --git a/samples/client/petstore/ruby-autoload/lib/petstore/models/enum_test.rb b/samples/client/petstore/ruby-autoload/lib/petstore/models/enum_test.rb
index 5159875cb89b..3b3905c138a3 100644
--- a/samples/client/petstore/ruby-autoload/lib/petstore/models/enum_test.rb
+++ b/samples/client/petstore/ruby-autoload/lib/petstore/models/enum_test.rb
@@ -98,6 +98,16 @@ def self.openapi_nullable
       ])
     end
 
+    # Returns attribute type mapping
+    def self.acceptable_openapi_types
+      openapi_types
+    end
+
+    # Returns the nullable attributes
+    def self.acceptable_openapi_nullable
+      openapi_nullable
+    end
+
     # Initializes the object
     # @param [Hash] attributes Model attributes in the form of hash
     def initialize(attributes = {})
@@ -254,18 +264,20 @@ def hash
     def self.build_from_hash(attributes)
       return nil unless attributes.is_a?(Hash)
       attributes = attributes.transform_keys(&:to_sym)
+      # include attributes inherited from allOf parents (the nearest declaration wins)
+      map = acceptable_attribute_map
       transformed_hash = {}
-      openapi_types.each_pair do |key, type|
-        if attributes.key?(attribute_map[key]) && attributes[attribute_map[key]].nil?
+      acceptable_openapi_types.each_pair do |key, type|
+        if attributes.key?(map[key]) && attributes[map[key]].nil?
           transformed_hash["#{key}"] = nil
         elsif type =~ /\AArray<(.*)>/i
           # check to ensure the input is an array given that the attribute
           # is documented as an array but the input is not
-          if attributes[attribute_map[key]].is_a?(Array)
-            transformed_hash["#{key}"] = attributes[attribute_map[key]].map { |v| _deserialize($1, v) }
+          if attributes[map[key]].is_a?(Array)
+            transformed_hash["#{key}"] = attributes[map[key]].map { |v| _deserialize($1, v) }
           end
-        elsif !attributes[attribute_map[key]].nil?
-          transformed_hash["#{key}"] = _deserialize(type, attributes[attribute_map[key]])
+        elsif !attributes[map[key]].nil?
+          transformed_hash["#{key}"] = _deserialize(type, attributes[map[key]])
         end
       end
       new(transformed_hash)
@@ -275,10 +287,11 @@ def self.build_from_hash(attributes)
     # @return [Hash] Returns the object in the form of hash
     def to_hash
       hash = {}
-      self.class.attribute_map.each_pair do |attr, param|
+      # include attributes inherited from allOf parents (the nearest declaration wins)
+      self.class.acceptable_attribute_map.each_pair do |attr, param|
         value = self.send(attr)
         if value.nil?
-          is_nullable = self.class.openapi_nullable.include?(attr)
+          is_nullable = self.class.acceptable_openapi_nullable.include?(attr)
           next if !is_nullable || (is_nullable && !instance_variable_defined?(:"@#{attr}"))
         end
 
diff --git a/samples/client/petstore/ruby-autoload/lib/petstore/models/fake_big_decimal_map200_response.rb b/samples/client/petstore/ruby-autoload/lib/petstore/models/fake_big_decimal_map200_response.rb
index 6d5e47b59656..b7be6af6d90e 100644
--- a/samples/client/petstore/ruby-autoload/lib/petstore/models/fake_big_decimal_map200_response.rb
+++ b/samples/client/petstore/ruby-autoload/lib/petstore/models/fake_big_decimal_map200_response.rb
@@ -51,6 +51,16 @@ def self.openapi_nullable
       ])
     end
 
+    # Returns attribute type mapping
+    def self.acceptable_openapi_types
+      openapi_types
+    end
+
+    # Returns the nullable attributes
+    def self.acceptable_openapi_nullable
+      openapi_nullable
+    end
+
     # Initializes the object
     # @param [Hash] attributes Model attributes in the form of hash
     def initialize(attributes = {})
@@ -120,18 +130,20 @@ def hash
     def self.build_from_hash(attributes)
       return nil unless attributes.is_a?(Hash)
       attributes = attributes.transform_keys(&:to_sym)
+      # include attributes inherited from allOf parents (the nearest declaration wins)
+      map = acceptable_attribute_map
       transformed_hash = {}
-      openapi_types.each_pair do |key, type|
-        if attributes.key?(attribute_map[key]) && attributes[attribute_map[key]].nil?
+      acceptable_openapi_types.each_pair do |key, type|
+        if attributes.key?(map[key]) && attributes[map[key]].nil?
           transformed_hash["#{key}"] = nil
         elsif type =~ /\AArray<(.*)>/i
           # check to ensure the input is an array given that the attribute
           # is documented as an array but the input is not
-          if attributes[attribute_map[key]].is_a?(Array)
-            transformed_hash["#{key}"] = attributes[attribute_map[key]].map { |v| _deserialize($1, v) }
+          if attributes[map[key]].is_a?(Array)
+            transformed_hash["#{key}"] = attributes[map[key]].map { |v| _deserialize($1, v) }
           end
-        elsif !attributes[attribute_map[key]].nil?
-          transformed_hash["#{key}"] = _deserialize(type, attributes[attribute_map[key]])
+        elsif !attributes[map[key]].nil?
+          transformed_hash["#{key}"] = _deserialize(type, attributes[map[key]])
         end
       end
       new(transformed_hash)
@@ -141,10 +153,11 @@ def self.build_from_hash(attributes)
     # @return [Hash] Returns the object in the form of hash
     def to_hash
       hash = {}
-      self.class.attribute_map.each_pair do |attr, param|
+      # include attributes inherited from allOf parents (the nearest declaration wins)
+      self.class.acceptable_attribute_map.each_pair do |attr, param|
         value = self.send(attr)
         if value.nil?
-          is_nullable = self.class.openapi_nullable.include?(attr)
+          is_nullable = self.class.acceptable_openapi_nullable.include?(attr)
           next if !is_nullable || (is_nullable && !instance_variable_defined?(:"@#{attr}"))
         end
 
diff --git a/samples/client/petstore/ruby-autoload/lib/petstore/models/file.rb b/samples/client/petstore/ruby-autoload/lib/petstore/models/file.rb
index 219237eb3c07..4fac9978fcaa 100644
--- a/samples/client/petstore/ruby-autoload/lib/petstore/models/file.rb
+++ b/samples/client/petstore/ruby-autoload/lib/petstore/models/file.rb
@@ -49,6 +49,16 @@ def self.openapi_nullable
       ])
     end
 
+    # Returns attribute type mapping
+    def self.acceptable_openapi_types
+      openapi_types
+    end
+
+    # Returns the nullable attributes
+    def self.acceptable_openapi_nullable
+      openapi_nullable
+    end
+
     # Initializes the object
     # @param [Hash] attributes Model attributes in the form of hash
     def initialize(attributes = {})
@@ -111,18 +121,20 @@ def hash
     def self.build_from_hash(attributes)
       return nil unless attributes.is_a?(Hash)
       attributes = attributes.transform_keys(&:to_sym)
+      # include attributes inherited from allOf parents (the nearest declaration wins)
+      map = acceptable_attribute_map
       transformed_hash = {}
-      openapi_types.each_pair do |key, type|
-        if attributes.key?(attribute_map[key]) && attributes[attribute_map[key]].nil?
+      acceptable_openapi_types.each_pair do |key, type|
+        if attributes.key?(map[key]) && attributes[map[key]].nil?
           transformed_hash["#{key}"] = nil
         elsif type =~ /\AArray<(.*)>/i
           # check to ensure the input is an array given that the attribute
           # is documented as an array but the input is not
-          if attributes[attribute_map[key]].is_a?(Array)
-            transformed_hash["#{key}"] = attributes[attribute_map[key]].map { |v| _deserialize($1, v) }
+          if attributes[map[key]].is_a?(Array)
+            transformed_hash["#{key}"] = attributes[map[key]].map { |v| _deserialize($1, v) }
           end
-        elsif !attributes[attribute_map[key]].nil?
-          transformed_hash["#{key}"] = _deserialize(type, attributes[attribute_map[key]])
+        elsif !attributes[map[key]].nil?
+          transformed_hash["#{key}"] = _deserialize(type, attributes[map[key]])
         end
       end
       new(transformed_hash)
@@ -132,10 +144,11 @@ def self.build_from_hash(attributes)
     # @return [Hash] Returns the object in the form of hash
     def to_hash
       hash = {}
-      self.class.attribute_map.each_pair do |attr, param|
+      # include attributes inherited from allOf parents (the nearest declaration wins)
+      self.class.acceptable_attribute_map.each_pair do |attr, param|
         value = self.send(attr)
         if value.nil?
-          is_nullable = self.class.openapi_nullable.include?(attr)
+          is_nullable = self.class.acceptable_openapi_nullable.include?(attr)
           next if !is_nullable || (is_nullable && !instance_variable_defined?(:"@#{attr}"))
         end
 
diff --git a/samples/client/petstore/ruby-autoload/lib/petstore/models/file_schema_test_class.rb b/samples/client/petstore/ruby-autoload/lib/petstore/models/file_schema_test_class.rb
index 8fdab5a25e86..074c235ebe17 100644
--- a/samples/client/petstore/ruby-autoload/lib/petstore/models/file_schema_test_class.rb
+++ b/samples/client/petstore/ruby-autoload/lib/petstore/models/file_schema_test_class.rb
@@ -51,6 +51,16 @@ def self.openapi_nullable
       ])
     end
 
+    # Returns attribute type mapping
+    def self.acceptable_openapi_types
+      openapi_types
+    end
+
+    # Returns the nullable attributes
+    def self.acceptable_openapi_nullable
+      openapi_nullable
+    end
+
     # Initializes the object
     # @param [Hash] attributes Model attributes in the form of hash
     def initialize(attributes = {})
@@ -120,18 +130,20 @@ def hash
     def self.build_from_hash(attributes)
       return nil unless attributes.is_a?(Hash)
       attributes = attributes.transform_keys(&:to_sym)
+      # include attributes inherited from allOf parents (the nearest declaration wins)
+      map = acceptable_attribute_map
       transformed_hash = {}
-      openapi_types.each_pair do |key, type|
-        if attributes.key?(attribute_map[key]) && attributes[attribute_map[key]].nil?
+      acceptable_openapi_types.each_pair do |key, type|
+        if attributes.key?(map[key]) && attributes[map[key]].nil?
           transformed_hash["#{key}"] = nil
         elsif type =~ /\AArray<(.*)>/i
           # check to ensure the input is an array given that the attribute
           # is documented as an array but the input is not
-          if attributes[attribute_map[key]].is_a?(Array)
-            transformed_hash["#{key}"] = attributes[attribute_map[key]].map { |v| _deserialize($1, v) }
+          if attributes[map[key]].is_a?(Array)
+            transformed_hash["#{key}"] = attributes[map[key]].map { |v| _deserialize($1, v) }
           end
-        elsif !attributes[attribute_map[key]].nil?
-          transformed_hash["#{key}"] = _deserialize(type, attributes[attribute_map[key]])
+        elsif !attributes[map[key]].nil?
+          transformed_hash["#{key}"] = _deserialize(type, attributes[map[key]])
         end
       end
       new(transformed_hash)
@@ -141,10 +153,11 @@ def self.build_from_hash(attributes)
     # @return [Hash] Returns the object in the form of hash
     def to_hash
       hash = {}
-      self.class.attribute_map.each_pair do |attr, param|
+      # include attributes inherited from allOf parents (the nearest declaration wins)
+      self.class.acceptable_attribute_map.each_pair do |attr, param|
         value = self.send(attr)
         if value.nil?
-          is_nullable = self.class.openapi_nullable.include?(attr)
+          is_nullable = self.class.acceptable_openapi_nullable.include?(attr)
           next if !is_nullable || (is_nullable && !instance_variable_defined?(:"@#{attr}"))
         end
 
diff --git a/samples/client/petstore/ruby-autoload/lib/petstore/models/foo.rb b/samples/client/petstore/ruby-autoload/lib/petstore/models/foo.rb
index ceb5b7497955..811726434b54 100644
--- a/samples/client/petstore/ruby-autoload/lib/petstore/models/foo.rb
+++ b/samples/client/petstore/ruby-autoload/lib/petstore/models/foo.rb
@@ -47,6 +47,16 @@ def self.openapi_nullable
       ])
     end
 
+    # Returns attribute type mapping
+    def self.acceptable_openapi_types
+      openapi_types
+    end
+
+    # Returns the nullable attributes
+    def self.acceptable_openapi_nullable
+      openapi_nullable
+    end
+
     # Initializes the object
     # @param [Hash] attributes Model attributes in the form of hash
     def initialize(attributes = {})
@@ -111,18 +121,20 @@ def hash
     def self.build_from_hash(attributes)
       return nil unless attributes.is_a?(Hash)
       attributes = attributes.transform_keys(&:to_sym)
+      # include attributes inherited from allOf parents (the nearest declaration wins)
+      map = acceptable_attribute_map
       transformed_hash = {}
-      openapi_types.each_pair do |key, type|
-        if attributes.key?(attribute_map[key]) && attributes[attribute_map[key]].nil?
+      acceptable_openapi_types.each_pair do |key, type|
+        if attributes.key?(map[key]) && attributes[map[key]].nil?
           transformed_hash["#{key}"] = nil
         elsif type =~ /\AArray<(.*)>/i
           # check to ensure the input is an array given that the attribute
           # is documented as an array but the input is not
-          if attributes[attribute_map[key]].is_a?(Array)
-            transformed_hash["#{key}"] = attributes[attribute_map[key]].map { |v| _deserialize($1, v) }
+          if attributes[map[key]].is_a?(Array)
+            transformed_hash["#{key}"] = attributes[map[key]].map { |v| _deserialize($1, v) }
           end
-        elsif !attributes[attribute_map[key]].nil?
-          transformed_hash["#{key}"] = _deserialize(type, attributes[attribute_map[key]])
+        elsif !attributes[map[key]].nil?
+          transformed_hash["#{key}"] = _deserialize(type, attributes[map[key]])
         end
       end
       new(transformed_hash)
@@ -132,10 +144,11 @@ def self.build_from_hash(attributes)
     # @return [Hash] Returns the object in the form of hash
     def to_hash
       hash = {}
-      self.class.attribute_map.each_pair do |attr, param|
+      # include attributes inherited from allOf parents (the nearest declaration wins)
+      self.class.acceptable_attribute_map.each_pair do |attr, param|
         value = self.send(attr)
         if value.nil?
-          is_nullable = self.class.openapi_nullable.include?(attr)
+          is_nullable = self.class.acceptable_openapi_nullable.include?(attr)
           next if !is_nullable || (is_nullable && !instance_variable_defined?(:"@#{attr}"))
         end
 
diff --git a/samples/client/petstore/ruby-autoload/lib/petstore/models/foo_get_default_response.rb b/samples/client/petstore/ruby-autoload/lib/petstore/models/foo_get_default_response.rb
index 42538a14e2cb..61d044ad8f26 100644
--- a/samples/client/petstore/ruby-autoload/lib/petstore/models/foo_get_default_response.rb
+++ b/samples/client/petstore/ruby-autoload/lib/petstore/models/foo_get_default_response.rb
@@ -47,6 +47,16 @@ def self.openapi_nullable
       ])
     end
 
+    # Returns attribute type mapping
+    def self.acceptable_openapi_types
+      openapi_types
+    end
+
+    # Returns the nullable attributes
+    def self.acceptable_openapi_nullable
+      openapi_nullable
+    end
+
     # Initializes the object
     # @param [Hash] attributes Model attributes in the form of hash
     def initialize(attributes = {})
@@ -109,18 +119,20 @@ def hash
     def self.build_from_hash(attributes)
       return nil unless attributes.is_a?(Hash)
       attributes = attributes.transform_keys(&:to_sym)
+      # include attributes inherited from allOf parents (the nearest declaration wins)
+      map = acceptable_attribute_map
       transformed_hash = {}
-      openapi_types.each_pair do |key, type|
-        if attributes.key?(attribute_map[key]) && attributes[attribute_map[key]].nil?
+      acceptable_openapi_types.each_pair do |key, type|
+        if attributes.key?(map[key]) && attributes[map[key]].nil?
           transformed_hash["#{key}"] = nil
         elsif type =~ /\AArray<(.*)>/i
           # check to ensure the input is an array given that the attribute
           # is documented as an array but the input is not
-          if attributes[attribute_map[key]].is_a?(Array)
-            transformed_hash["#{key}"] = attributes[attribute_map[key]].map { |v| _deserialize($1, v) }
+          if attributes[map[key]].is_a?(Array)
+            transformed_hash["#{key}"] = attributes[map[key]].map { |v| _deserialize($1, v) }
           end
-        elsif !attributes[attribute_map[key]].nil?
-          transformed_hash["#{key}"] = _deserialize(type, attributes[attribute_map[key]])
+        elsif !attributes[map[key]].nil?
+          transformed_hash["#{key}"] = _deserialize(type, attributes[map[key]])
         end
       end
       new(transformed_hash)
@@ -130,10 +142,11 @@ def self.build_from_hash(attributes)
     # @return [Hash] Returns the object in the form of hash
     def to_hash
       hash = {}
-      self.class.attribute_map.each_pair do |attr, param|
+      # include attributes inherited from allOf parents (the nearest declaration wins)
+      self.class.acceptable_attribute_map.each_pair do |attr, param|
         value = self.send(attr)
         if value.nil?
-          is_nullable = self.class.openapi_nullable.include?(attr)
+          is_nullable = self.class.acceptable_openapi_nullable.include?(attr)
           next if !is_nullable || (is_nullable && !instance_variable_defined?(:"@#{attr}"))
         end
 
diff --git a/samples/client/petstore/ruby-autoload/lib/petstore/models/format_test.rb b/samples/client/petstore/ruby-autoload/lib/petstore/models/format_test.rb
index 03a4e130a8f9..6760f6807c59 100644
--- a/samples/client/petstore/ruby-autoload/lib/petstore/models/format_test.rb
+++ b/samples/client/petstore/ruby-autoload/lib/petstore/models/format_test.rb
@@ -109,6 +109,16 @@ def self.openapi_nullable
       ])
     end
 
+    # Returns attribute type mapping
+    def self.acceptable_openapi_types
+      openapi_types
+    end
+
+    # Returns the nullable attributes
+    def self.acceptable_openapi_nullable
+      openapi_nullable
+    end
+
     # Initializes the object
     # @param [Hash] attributes Model attributes in the form of hash
     def initialize(attributes = {})
@@ -525,18 +535,20 @@ def hash
     def self.build_from_hash(attributes)
       return nil unless attributes.is_a?(Hash)
       attributes = attributes.transform_keys(&:to_sym)
+      # include attributes inherited from allOf parents (the nearest declaration wins)
+      map = acceptable_attribute_map
       transformed_hash = {}
-      openapi_types.each_pair do |key, type|
-        if attributes.key?(attribute_map[key]) && attributes[attribute_map[key]].nil?
+      acceptable_openapi_types.each_pair do |key, type|
+        if attributes.key?(map[key]) && attributes[map[key]].nil?
           transformed_hash["#{key}"] = nil
         elsif type =~ /\AArray<(.*)>/i
           # check to ensure the input is an array given that the attribute
           # is documented as an array but the input is not
-          if attributes[attribute_map[key]].is_a?(Array)
-            transformed_hash["#{key}"] = attributes[attribute_map[key]].map { |v| _deserialize($1, v) }
+          if attributes[map[key]].is_a?(Array)
+            transformed_hash["#{key}"] = attributes[map[key]].map { |v| _deserialize($1, v) }
           end
-        elsif !attributes[attribute_map[key]].nil?
-          transformed_hash["#{key}"] = _deserialize(type, attributes[attribute_map[key]])
+        elsif !attributes[map[key]].nil?
+          transformed_hash["#{key}"] = _deserialize(type, attributes[map[key]])
         end
       end
       new(transformed_hash)
@@ -546,10 +558,11 @@ def self.build_from_hash(attributes)
     # @return [Hash] Returns the object in the form of hash
     def to_hash
       hash = {}
-      self.class.attribute_map.each_pair do |attr, param|
+      # include attributes inherited from allOf parents (the nearest declaration wins)
+      self.class.acceptable_attribute_map.each_pair do |attr, param|
         value = self.send(attr)
         if value.nil?
-          is_nullable = self.class.openapi_nullable.include?(attr)
+          is_nullable = self.class.acceptable_openapi_nullable.include?(attr)
           next if !is_nullable || (is_nullable && !instance_variable_defined?(:"@#{attr}"))
         end
 
diff --git a/samples/client/petstore/ruby-autoload/lib/petstore/models/has_only_read_only.rb b/samples/client/petstore/ruby-autoload/lib/petstore/models/has_only_read_only.rb
index cc584c09e54f..604a3da147bd 100644
--- a/samples/client/petstore/ruby-autoload/lib/petstore/models/has_only_read_only.rb
+++ b/samples/client/petstore/ruby-autoload/lib/petstore/models/has_only_read_only.rb
@@ -51,6 +51,16 @@ def self.openapi_nullable
       ])
     end
 
+    # Returns attribute type mapping
+    def self.acceptable_openapi_types
+      openapi_types
+    end
+
+    # Returns the nullable attributes
+    def self.acceptable_openapi_nullable
+      openapi_nullable
+    end
+
     # Initializes the object
     # @param [Hash] attributes Model attributes in the form of hash
     def initialize(attributes = {})
@@ -118,18 +128,20 @@ def hash
     def self.build_from_hash(attributes)
       return nil unless attributes.is_a?(Hash)
       attributes = attributes.transform_keys(&:to_sym)
+      # include attributes inherited from allOf parents (the nearest declaration wins)
+      map = acceptable_attribute_map
       transformed_hash = {}
-      openapi_types.each_pair do |key, type|
-        if attributes.key?(attribute_map[key]) && attributes[attribute_map[key]].nil?
+      acceptable_openapi_types.each_pair do |key, type|
+        if attributes.key?(map[key]) && attributes[map[key]].nil?
           transformed_hash["#{key}"] = nil
         elsif type =~ /\AArray<(.*)>/i
           # check to ensure the input is an array given that the attribute
           # is documented as an array but the input is not
-          if attributes[attribute_map[key]].is_a?(Array)
-            transformed_hash["#{key}"] = attributes[attribute_map[key]].map { |v| _deserialize($1, v) }
+          if attributes[map[key]].is_a?(Array)
+            transformed_hash["#{key}"] = attributes[map[key]].map { |v| _deserialize($1, v) }
           end
-        elsif !attributes[attribute_map[key]].nil?
-          transformed_hash["#{key}"] = _deserialize(type, attributes[attribute_map[key]])
+        elsif !attributes[map[key]].nil?
+          transformed_hash["#{key}"] = _deserialize(type, attributes[map[key]])
         end
       end
       new(transformed_hash)
@@ -139,10 +151,11 @@ def self.build_from_hash(attributes)
     # @return [Hash] Returns the object in the form of hash
     def to_hash
       hash = {}
-      self.class.attribute_map.each_pair do |attr, param|
+      # include attributes inherited from allOf parents (the nearest declaration wins)
+      self.class.acceptable_attribute_map.each_pair do |attr, param|
         value = self.send(attr)
         if value.nil?
-          is_nullable = self.class.openapi_nullable.include?(attr)
+          is_nullable = self.class.acceptable_openapi_nullable.include?(attr)
           next if !is_nullable || (is_nullable && !instance_variable_defined?(:"@#{attr}"))
         end
 
diff --git a/samples/client/petstore/ruby-autoload/lib/petstore/models/health_check_result.rb b/samples/client/petstore/ruby-autoload/lib/petstore/models/health_check_result.rb
index a66e1b71331d..0792044db072 100644
--- a/samples/client/petstore/ruby-autoload/lib/petstore/models/health_check_result.rb
+++ b/samples/client/petstore/ruby-autoload/lib/petstore/models/health_check_result.rb
@@ -49,6 +49,16 @@ def self.openapi_nullable
       ])
     end
 
+    # Returns attribute type mapping
+    def self.acceptable_openapi_types
+      openapi_types
+    end
+
+    # Returns the nullable attributes
+    def self.acceptable_openapi_nullable
+      openapi_nullable
+    end
+
     # Initializes the object
     # @param [Hash] attributes Model attributes in the form of hash
     def initialize(attributes = {})
@@ -111,18 +121,20 @@ def hash
     def self.build_from_hash(attributes)
       return nil unless attributes.is_a?(Hash)
       attributes = attributes.transform_keys(&:to_sym)
+      # include attributes inherited from allOf parents (the nearest declaration wins)
+      map = acceptable_attribute_map
       transformed_hash = {}
-      openapi_types.each_pair do |key, type|
-        if attributes.key?(attribute_map[key]) && attributes[attribute_map[key]].nil?
+      acceptable_openapi_types.each_pair do |key, type|
+        if attributes.key?(map[key]) && attributes[map[key]].nil?
           transformed_hash["#{key}"] = nil
         elsif type =~ /\AArray<(.*)>/i
           # check to ensure the input is an array given that the attribute
           # is documented as an array but the input is not
-          if attributes[attribute_map[key]].is_a?(Array)
-            transformed_hash["#{key}"] = attributes[attribute_map[key]].map { |v| _deserialize($1, v) }
+          if attributes[map[key]].is_a?(Array)
+            transformed_hash["#{key}"] = attributes[map[key]].map { |v| _deserialize($1, v) }
           end
-        elsif !attributes[attribute_map[key]].nil?
-          transformed_hash["#{key}"] = _deserialize(type, attributes[attribute_map[key]])
+        elsif !attributes[map[key]].nil?
+          transformed_hash["#{key}"] = _deserialize(type, attributes[map[key]])
         end
       end
       new(transformed_hash)
@@ -132,10 +144,11 @@ def self.build_from_hash(attributes)
     # @return [Hash] Returns the object in the form of hash
     def to_hash
       hash = {}
-      self.class.attribute_map.each_pair do |attr, param|
+      # include attributes inherited from allOf parents (the nearest declaration wins)
+      self.class.acceptable_attribute_map.each_pair do |attr, param|
         value = self.send(attr)
         if value.nil?
-          is_nullable = self.class.openapi_nullable.include?(attr)
+          is_nullable = self.class.acceptable_openapi_nullable.include?(attr)
           next if !is_nullable || (is_nullable && !instance_variable_defined?(:"@#{attr}"))
         end
 
diff --git a/samples/client/petstore/ruby-autoload/lib/petstore/models/list.rb b/samples/client/petstore/ruby-autoload/lib/petstore/models/list.rb
index 2dc658065278..ecc8eb8aafc5 100644
--- a/samples/client/petstore/ruby-autoload/lib/petstore/models/list.rb
+++ b/samples/client/petstore/ruby-autoload/lib/petstore/models/list.rb
@@ -47,6 +47,16 @@ def self.openapi_nullable
       ])
     end
 
+    # Returns attribute type mapping
+    def self.acceptable_openapi_types
+      openapi_types
+    end
+
+    # Returns the nullable attributes
+    def self.acceptable_openapi_nullable
+      openapi_nullable
+    end
+
     # Initializes the object
     # @param [Hash] attributes Model attributes in the form of hash
     def initialize(attributes = {})
@@ -109,18 +119,20 @@ def hash
     def self.build_from_hash(attributes)
       return nil unless attributes.is_a?(Hash)
       attributes = attributes.transform_keys(&:to_sym)
+      # include attributes inherited from allOf parents (the nearest declaration wins)
+      map = acceptable_attribute_map
       transformed_hash = {}
-      openapi_types.each_pair do |key, type|
-        if attributes.key?(attribute_map[key]) && attributes[attribute_map[key]].nil?
+      acceptable_openapi_types.each_pair do |key, type|
+        if attributes.key?(map[key]) && attributes[map[key]].nil?
           transformed_hash["#{key}"] = nil
         elsif type =~ /\AArray<(.*)>/i
           # check to ensure the input is an array given that the attribute
           # is documented as an array but the input is not
-          if attributes[attribute_map[key]].is_a?(Array)
-            transformed_hash["#{key}"] = attributes[attribute_map[key]].map { |v| _deserialize($1, v) }
+          if attributes[map[key]].is_a?(Array)
+            transformed_hash["#{key}"] = attributes[map[key]].map { |v| _deserialize($1, v) }
           end
-        elsif !attributes[attribute_map[key]].nil?
-          transformed_hash["#{key}"] = _deserialize(type, attributes[attribute_map[key]])
+        elsif !attributes[map[key]].nil?
+          transformed_hash["#{key}"] = _deserialize(type, attributes[map[key]])
         end
       end
       new(transformed_hash)
@@ -130,10 +142,11 @@ def self.build_from_hash(attributes)
     # @return [Hash] Returns the object in the form of hash
     def to_hash
       hash = {}
-      self.class.attribute_map.each_pair do |attr, param|
+      # include attributes inherited from allOf parents (the nearest declaration wins)
+      self.class.acceptable_attribute_map.each_pair do |attr, param|
         value = self.send(attr)
         if value.nil?
-          is_nullable = self.class.openapi_nullable.include?(attr)
+          is_nullable = self.class.acceptable_openapi_nullable.include?(attr)
           next if !is_nullable || (is_nullable && !instance_variable_defined?(:"@#{attr}"))
         end
 
diff --git a/samples/client/petstore/ruby-autoload/lib/petstore/models/map_test.rb b/samples/client/petstore/ruby-autoload/lib/petstore/models/map_test.rb
index 78c5472f24ae..eca01649a52a 100644
--- a/samples/client/petstore/ruby-autoload/lib/petstore/models/map_test.rb
+++ b/samples/client/petstore/ruby-autoload/lib/petstore/models/map_test.rb
@@ -81,6 +81,16 @@ def self.openapi_nullable
       ])
     end
 
+    # Returns attribute type mapping
+    def self.acceptable_openapi_types
+      openapi_types
+    end
+
+    # Returns the nullable attributes
+    def self.acceptable_openapi_nullable
+      openapi_nullable
+    end
+
     # Initializes the object
     # @param [Hash] attributes Model attributes in the form of hash
     def initialize(attributes = {})
@@ -166,18 +176,20 @@ def hash
     def self.build_from_hash(attributes)
       return nil unless attributes.is_a?(Hash)
       attributes = attributes.transform_keys(&:to_sym)
+      # include attributes inherited from allOf parents (the nearest declaration wins)
+      map = acceptable_attribute_map
       transformed_hash = {}
-      openapi_types.each_pair do |key, type|
-        if attributes.key?(attribute_map[key]) && attributes[attribute_map[key]].nil?
+      acceptable_openapi_types.each_pair do |key, type|
+        if attributes.key?(map[key]) && attributes[map[key]].nil?
           transformed_hash["#{key}"] = nil
         elsif type =~ /\AArray<(.*)>/i
           # check to ensure the input is an array given that the attribute
           # is documented as an array but the input is not
-          if attributes[attribute_map[key]].is_a?(Array)
-            transformed_hash["#{key}"] = attributes[attribute_map[key]].map { |v| _deserialize($1, v) }
+          if attributes[map[key]].is_a?(Array)
+            transformed_hash["#{key}"] = attributes[map[key]].map { |v| _deserialize($1, v) }
           end
-        elsif !attributes[attribute_map[key]].nil?
-          transformed_hash["#{key}"] = _deserialize(type, attributes[attribute_map[key]])
+        elsif !attributes[map[key]].nil?
+          transformed_hash["#{key}"] = _deserialize(type, attributes[map[key]])
         end
       end
       new(transformed_hash)
@@ -187,10 +199,11 @@ def self.build_from_hash(attributes)
     # @return [Hash] Returns the object in the form of hash
     def to_hash
       hash = {}
-      self.class.attribute_map.each_pair do |attr, param|
+      # include attributes inherited from allOf parents (the nearest declaration wins)
+      self.class.acceptable_attribute_map.each_pair do |attr, param|
         value = self.send(attr)
         if value.nil?
-          is_nullable = self.class.openapi_nullable.include?(attr)
+          is_nullable = self.class.acceptable_openapi_nullable.include?(attr)
           next if !is_nullable || (is_nullable && !instance_variable_defined?(:"@#{attr}"))
         end
 
diff --git a/samples/client/petstore/ruby-autoload/lib/petstore/models/mixed_properties_and_additional_properties_class.rb b/samples/client/petstore/ruby-autoload/lib/petstore/models/mixed_properties_and_additional_properties_class.rb
index bf1d3768951b..060c8488652f 100644
--- a/samples/client/petstore/ruby-autoload/lib/petstore/models/mixed_properties_and_additional_properties_class.rb
+++ b/samples/client/petstore/ruby-autoload/lib/petstore/models/mixed_properties_and_additional_properties_class.rb
@@ -55,6 +55,16 @@ def self.openapi_nullable
       ])
     end
 
+    # Returns attribute type mapping
+    def self.acceptable_openapi_types
+      openapi_types
+    end
+
+    # Returns the nullable attributes
+    def self.acceptable_openapi_nullable
+      openapi_nullable
+    end
+
     # Initializes the object
     # @param [Hash] attributes Model attributes in the form of hash
     def initialize(attributes = {})
@@ -129,18 +139,20 @@ def hash
     def self.build_from_hash(attributes)
       return nil unless attributes.is_a?(Hash)
       attributes = attributes.transform_keys(&:to_sym)
+      # include attributes inherited from allOf parents (the nearest declaration wins)
+      map = acceptable_attribute_map
       transformed_hash = {}
-      openapi_types.each_pair do |key, type|
-        if attributes.key?(attribute_map[key]) && attributes[attribute_map[key]].nil?
+      acceptable_openapi_types.each_pair do |key, type|
+        if attributes.key?(map[key]) && attributes[map[key]].nil?
           transformed_hash["#{key}"] = nil
         elsif type =~ /\AArray<(.*)>/i
           # check to ensure the input is an array given that the attribute
           # is documented as an array but the input is not
-          if attributes[attribute_map[key]].is_a?(Array)
-            transformed_hash["#{key}"] = attributes[attribute_map[key]].map { |v| _deserialize($1, v) }
+          if attributes[map[key]].is_a?(Array)
+            transformed_hash["#{key}"] = attributes[map[key]].map { |v| _deserialize($1, v) }
           end
-        elsif !attributes[attribute_map[key]].nil?
-          transformed_hash["#{key}"] = _deserialize(type, attributes[attribute_map[key]])
+        elsif !attributes[map[key]].nil?
+          transformed_hash["#{key}"] = _deserialize(type, attributes[map[key]])
         end
       end
       new(transformed_hash)
@@ -150,10 +162,11 @@ def self.build_from_hash(attributes)
     # @return [Hash] Returns the object in the form of hash
     def to_hash
       hash = {}
-      self.class.attribute_map.each_pair do |attr, param|
+      # include attributes inherited from allOf parents (the nearest declaration wins)
+      self.class.acceptable_attribute_map.each_pair do |attr, param|
         value = self.send(attr)
         if value.nil?
-          is_nullable = self.class.openapi_nullable.include?(attr)
+          is_nullable = self.class.acceptable_openapi_nullable.include?(attr)
           next if !is_nullable || (is_nullable && !instance_variable_defined?(:"@#{attr}"))
         end
 
diff --git a/samples/client/petstore/ruby-autoload/lib/petstore/models/model200_response.rb b/samples/client/petstore/ruby-autoload/lib/petstore/models/model200_response.rb
index 9cff83ced2c9..2ea5253eb3d4 100644
--- a/samples/client/petstore/ruby-autoload/lib/petstore/models/model200_response.rb
+++ b/samples/client/petstore/ruby-autoload/lib/petstore/models/model200_response.rb
@@ -52,6 +52,16 @@ def self.openapi_nullable
       ])
     end
 
+    # Returns attribute type mapping
+    def self.acceptable_openapi_types
+      openapi_types
+    end
+
+    # Returns the nullable attributes
+    def self.acceptable_openapi_nullable
+      openapi_nullable
+    end
+
     # Initializes the object
     # @param [Hash] attributes Model attributes in the form of hash
     def initialize(attributes = {})
@@ -119,18 +129,20 @@ def hash
     def self.build_from_hash(attributes)
       return nil unless attributes.is_a?(Hash)
       attributes = attributes.transform_keys(&:to_sym)
+      # include attributes inherited from allOf parents (the nearest declaration wins)
+      map = acceptable_attribute_map
       transformed_hash = {}
-      openapi_types.each_pair do |key, type|
-        if attributes.key?(attribute_map[key]) && attributes[attribute_map[key]].nil?
+      acceptable_openapi_types.each_pair do |key, type|
+        if attributes.key?(map[key]) && attributes[map[key]].nil?
           transformed_hash["#{key}"] = nil
         elsif type =~ /\AArray<(.*)>/i
           # check to ensure the input is an array given that the attribute
           # is documented as an array but the input is not
-          if attributes[attribute_map[key]].is_a?(Array)
-            transformed_hash["#{key}"] = attributes[attribute_map[key]].map { |v| _deserialize($1, v) }
+          if attributes[map[key]].is_a?(Array)
+            transformed_hash["#{key}"] = attributes[map[key]].map { |v| _deserialize($1, v) }
           end
-        elsif !attributes[attribute_map[key]].nil?
-          transformed_hash["#{key}"] = _deserialize(type, attributes[attribute_map[key]])
+        elsif !attributes[map[key]].nil?
+          transformed_hash["#{key}"] = _deserialize(type, attributes[map[key]])
         end
       end
       new(transformed_hash)
@@ -140,10 +152,11 @@ def self.build_from_hash(attributes)
     # @return [Hash] Returns the object in the form of hash
     def to_hash
       hash = {}
-      self.class.attribute_map.each_pair do |attr, param|
+      # include attributes inherited from allOf parents (the nearest declaration wins)
+      self.class.acceptable_attribute_map.each_pair do |attr, param|
         value = self.send(attr)
         if value.nil?
-          is_nullable = self.class.openapi_nullable.include?(attr)
+          is_nullable = self.class.acceptable_openapi_nullable.include?(attr)
           next if !is_nullable || (is_nullable && !instance_variable_defined?(:"@#{attr}"))
         end
 
diff --git a/samples/client/petstore/ruby-autoload/lib/petstore/models/model_return.rb b/samples/client/petstore/ruby-autoload/lib/petstore/models/model_return.rb
index d520a45c2040..c2b6ac11c2e9 100644
--- a/samples/client/petstore/ruby-autoload/lib/petstore/models/model_return.rb
+++ b/samples/client/petstore/ruby-autoload/lib/petstore/models/model_return.rb
@@ -48,6 +48,16 @@ def self.openapi_nullable
       ])
     end
 
+    # Returns attribute type mapping
+    def self.acceptable_openapi_types
+      openapi_types
+    end
+
+    # Returns the nullable attributes
+    def self.acceptable_openapi_nullable
+      openapi_nullable
+    end
+
     # Initializes the object
     # @param [Hash] attributes Model attributes in the form of hash
     def initialize(attributes = {})
@@ -110,18 +120,20 @@ def hash
     def self.build_from_hash(attributes)
       return nil unless attributes.is_a?(Hash)
       attributes = attributes.transform_keys(&:to_sym)
+      # include attributes inherited from allOf parents (the nearest declaration wins)
+      map = acceptable_attribute_map
       transformed_hash = {}
-      openapi_types.each_pair do |key, type|
-        if attributes.key?(attribute_map[key]) && attributes[attribute_map[key]].nil?
+      acceptable_openapi_types.each_pair do |key, type|
+        if attributes.key?(map[key]) && attributes[map[key]].nil?
           transformed_hash["#{key}"] = nil
         elsif type =~ /\AArray<(.*)>/i
           # check to ensure the input is an array given that the attribute
           # is documented as an array but the input is not
-          if attributes[attribute_map[key]].is_a?(Array)
-            transformed_hash["#{key}"] = attributes[attribute_map[key]].map { |v| _deserialize($1, v) }
+          if attributes[map[key]].is_a?(Array)
+            transformed_hash["#{key}"] = attributes[map[key]].map { |v| _deserialize($1, v) }
           end
-        elsif !attributes[attribute_map[key]].nil?
-          transformed_hash["#{key}"] = _deserialize(type, attributes[attribute_map[key]])
+        elsif !attributes[map[key]].nil?
+          transformed_hash["#{key}"] = _deserialize(type, attributes[map[key]])
         end
       end
       new(transformed_hash)
@@ -131,10 +143,11 @@ def self.build_from_hash(attributes)
     # @return [Hash] Returns the object in the form of hash
     def to_hash
       hash = {}
-      self.class.attribute_map.each_pair do |attr, param|
+      # include attributes inherited from allOf parents (the nearest declaration wins)
+      self.class.acceptable_attribute_map.each_pair do |attr, param|
         value = self.send(attr)
         if value.nil?
-          is_nullable = self.class.openapi_nullable.include?(attr)
+          is_nullable = self.class.acceptable_openapi_nullable.include?(attr)
           next if !is_nullable || (is_nullable && !instance_variable_defined?(:"@#{attr}"))
         end
 
diff --git a/samples/client/petstore/ruby-autoload/lib/petstore/models/name.rb b/samples/client/petstore/ruby-autoload/lib/petstore/models/name.rb
index 45b01b5746d3..c989368e6597 100644
--- a/samples/client/petstore/ruby-autoload/lib/petstore/models/name.rb
+++ b/samples/client/petstore/ruby-autoload/lib/petstore/models/name.rb
@@ -60,6 +60,16 @@ def self.openapi_nullable
       ])
     end
 
+    # Returns attribute type mapping
+    def self.acceptable_openapi_types
+      openapi_types
+    end
+
+    # Returns the nullable attributes
+    def self.acceptable_openapi_nullable
+      openapi_nullable
+    end
+
     # Initializes the object
     # @param [Hash] attributes Model attributes in the form of hash
     def initialize(attributes = {})
@@ -154,18 +164,20 @@ def hash
     def self.build_from_hash(attributes)
       return nil unless attributes.is_a?(Hash)
       attributes = attributes.transform_keys(&:to_sym)
+      # include attributes inherited from allOf parents (the nearest declaration wins)
+      map = acceptable_attribute_map
       transformed_hash = {}
-      openapi_types.each_pair do |key, type|
-        if attributes.key?(attribute_map[key]) && attributes[attribute_map[key]].nil?
+      acceptable_openapi_types.each_pair do |key, type|
+        if attributes.key?(map[key]) && attributes[map[key]].nil?
           transformed_hash["#{key}"] = nil
         elsif type =~ /\AArray<(.*)>/i
           # check to ensure the input is an array given that the attribute
           # is documented as an array but the input is not
-          if attributes[attribute_map[key]].is_a?(Array)
-            transformed_hash["#{key}"] = attributes[attribute_map[key]].map { |v| _deserialize($1, v) }
+          if attributes[map[key]].is_a?(Array)
+            transformed_hash["#{key}"] = attributes[map[key]].map { |v| _deserialize($1, v) }
           end
-        elsif !attributes[attribute_map[key]].nil?
-          transformed_hash["#{key}"] = _deserialize(type, attributes[attribute_map[key]])
+        elsif !attributes[map[key]].nil?
+          transformed_hash["#{key}"] = _deserialize(type, attributes[map[key]])
         end
       end
       new(transformed_hash)
@@ -175,10 +187,11 @@ def self.build_from_hash(attributes)
     # @return [Hash] Returns the object in the form of hash
     def to_hash
       hash = {}
-      self.class.attribute_map.each_pair do |attr, param|
+      # include attributes inherited from allOf parents (the nearest declaration wins)
+      self.class.acceptable_attribute_map.each_pair do |attr, param|
         value = self.send(attr)
         if value.nil?
-          is_nullable = self.class.openapi_nullable.include?(attr)
+          is_nullable = self.class.acceptable_openapi_nullable.include?(attr)
           next if !is_nullable || (is_nullable && !instance_variable_defined?(:"@#{attr}"))
         end
 
diff --git a/samples/client/petstore/ruby-autoload/lib/petstore/models/nullable_class.rb b/samples/client/petstore/ruby-autoload/lib/petstore/models/nullable_class.rb
index f81fb17f118a..de5510060a65 100644
--- a/samples/client/petstore/ruby-autoload/lib/petstore/models/nullable_class.rb
+++ b/samples/client/petstore/ruby-autoload/lib/petstore/models/nullable_class.rb
@@ -101,6 +101,16 @@ def self.openapi_nullable
       ])
     end
 
+    # Returns attribute type mapping
+    def self.acceptable_openapi_types
+      openapi_types
+    end
+
+    # Returns the nullable attributes
+    def self.acceptable_openapi_nullable
+      openapi_nullable
+    end
+
     # Initializes the object
     # @param [Hash] attributes Model attributes in the form of hash
     def initialize(attributes = {})
@@ -230,18 +240,20 @@ def hash
     def self.build_from_hash(attributes)
       return nil unless attributes.is_a?(Hash)
       attributes = attributes.transform_keys(&:to_sym)
+      # include attributes inherited from allOf parents (the nearest declaration wins)
+      map = acceptable_attribute_map
       transformed_hash = {}
-      openapi_types.each_pair do |key, type|
-        if attributes.key?(attribute_map[key]) && attributes[attribute_map[key]].nil?
+      acceptable_openapi_types.each_pair do |key, type|
+        if attributes.key?(map[key]) && attributes[map[key]].nil?
           transformed_hash["#{key}"] = nil
         elsif type =~ /\AArray<(.*)>/i
           # check to ensure the input is an array given that the attribute
           # is documented as an array but the input is not
-          if attributes[attribute_map[key]].is_a?(Array)
-            transformed_hash["#{key}"] = attributes[attribute_map[key]].map { |v| _deserialize($1, v) }
+          if attributes[map[key]].is_a?(Array)
+            transformed_hash["#{key}"] = attributes[map[key]].map { |v| _deserialize($1, v) }
           end
-        elsif !attributes[attribute_map[key]].nil?
-          transformed_hash["#{key}"] = _deserialize(type, attributes[attribute_map[key]])
+        elsif !attributes[map[key]].nil?
+          transformed_hash["#{key}"] = _deserialize(type, attributes[map[key]])
         end
       end
       new(transformed_hash)
@@ -251,10 +263,11 @@ def self.build_from_hash(attributes)
     # @return [Hash] Returns the object in the form of hash
     def to_hash
       hash = {}
-      self.class.attribute_map.each_pair do |attr, param|
+      # include attributes inherited from allOf parents (the nearest declaration wins)
+      self.class.acceptable_attribute_map.each_pair do |attr, param|
         value = self.send(attr)
         if value.nil?
-          is_nullable = self.class.openapi_nullable.include?(attr)
+          is_nullable = self.class.acceptable_openapi_nullable.include?(attr)
           next if !is_nullable || (is_nullable && !instance_variable_defined?(:"@#{attr}"))
         end
 
diff --git a/samples/client/petstore/ruby-autoload/lib/petstore/models/number_only.rb b/samples/client/petstore/ruby-autoload/lib/petstore/models/number_only.rb
index 9bf457dfd188..b4fb53e2c3d3 100644
--- a/samples/client/petstore/ruby-autoload/lib/petstore/models/number_only.rb
+++ b/samples/client/petstore/ruby-autoload/lib/petstore/models/number_only.rb
@@ -47,6 +47,16 @@ def self.openapi_nullable
       ])
     end
 
+    # Returns attribute type mapping
+    def self.acceptable_openapi_types
+      openapi_types
+    end
+
+    # Returns the nullable attributes
+    def self.acceptable_openapi_nullable
+      openapi_nullable
+    end
+
     # Initializes the object
     # @param [Hash] attributes Model attributes in the form of hash
     def initialize(attributes = {})
@@ -109,18 +119,20 @@ def hash
     def self.build_from_hash(attributes)
       return nil unless attributes.is_a?(Hash)
       attributes = attributes.transform_keys(&:to_sym)
+      # include attributes inherited from allOf parents (the nearest declaration wins)
+      map = acceptable_attribute_map
       transformed_hash = {}
-      openapi_types.each_pair do |key, type|
-        if attributes.key?(attribute_map[key]) && attributes[attribute_map[key]].nil?
+      acceptable_openapi_types.each_pair do |key, type|
+        if attributes.key?(map[key]) && attributes[map[key]].nil?
           transformed_hash["#{key}"] = nil
         elsif type =~ /\AArray<(.*)>/i
           # check to ensure the input is an array given that the attribute
           # is documented as an array but the input is not
-          if attributes[attribute_map[key]].is_a?(Array)
-            transformed_hash["#{key}"] = attributes[attribute_map[key]].map { |v| _deserialize($1, v) }
+          if attributes[map[key]].is_a?(Array)
+            transformed_hash["#{key}"] = attributes[map[key]].map { |v| _deserialize($1, v) }
           end
-        elsif !attributes[attribute_map[key]].nil?
-          transformed_hash["#{key}"] = _deserialize(type, attributes[attribute_map[key]])
+        elsif !attributes[map[key]].nil?
+          transformed_hash["#{key}"] = _deserialize(type, attributes[map[key]])
         end
       end
       new(transformed_hash)
@@ -130,10 +142,11 @@ def self.build_from_hash(attributes)
     # @return [Hash] Returns the object in the form of hash
     def to_hash
       hash = {}
-      self.class.attribute_map.each_pair do |attr, param|
+      # include attributes inherited from allOf parents (the nearest declaration wins)
+      self.class.acceptable_attribute_map.each_pair do |attr, param|
         value = self.send(attr)
         if value.nil?
-          is_nullable = self.class.openapi_nullable.include?(attr)
+          is_nullable = self.class.acceptable_openapi_nullable.include?(attr)
           next if !is_nullable || (is_nullable && !instance_variable_defined?(:"@#{attr}"))
         end
 
diff --git a/samples/client/petstore/ruby-autoload/lib/petstore/models/object_with_deprecated_fields.rb b/samples/client/petstore/ruby-autoload/lib/petstore/models/object_with_deprecated_fields.rb
index dceda346bd70..3819fef7a58b 100644
--- a/samples/client/petstore/ruby-autoload/lib/petstore/models/object_with_deprecated_fields.rb
+++ b/samples/client/petstore/ruby-autoload/lib/petstore/models/object_with_deprecated_fields.rb
@@ -59,6 +59,16 @@ def self.openapi_nullable
       ])
     end
 
+    # Returns attribute type mapping
+    def self.acceptable_openapi_types
+      openapi_types
+    end
+
+    # Returns the nullable attributes
+    def self.acceptable_openapi_nullable
+      openapi_nullable
+    end
+
     # Initializes the object
     # @param [Hash] attributes Model attributes in the form of hash
     def initialize(attributes = {})
@@ -138,18 +148,20 @@ def hash
     def self.build_from_hash(attributes)
       return nil unless attributes.is_a?(Hash)
       attributes = attributes.transform_keys(&:to_sym)
+      # include attributes inherited from allOf parents (the nearest declaration wins)
+      map = acceptable_attribute_map
       transformed_hash = {}
-      openapi_types.each_pair do |key, type|
-        if attributes.key?(attribute_map[key]) && attributes[attribute_map[key]].nil?
+      acceptable_openapi_types.each_pair do |key, type|
+        if attributes.key?(map[key]) && attributes[map[key]].nil?
           transformed_hash["#{key}"] = nil
         elsif type =~ /\AArray<(.*)>/i
           # check to ensure the input is an array given that the attribute
           # is documented as an array but the input is not
-          if attributes[attribute_map[key]].is_a?(Array)
-            transformed_hash["#{key}"] = attributes[attribute_map[key]].map { |v| _deserialize($1, v) }
+          if attributes[map[key]].is_a?(Array)
+            transformed_hash["#{key}"] = attributes[map[key]].map { |v| _deserialize($1, v) }
           end
-        elsif !attributes[attribute_map[key]].nil?
-          transformed_hash["#{key}"] = _deserialize(type, attributes[attribute_map[key]])
+        elsif !attributes[map[key]].nil?
+          transformed_hash["#{key}"] = _deserialize(type, attributes[map[key]])
         end
       end
       new(transformed_hash)
@@ -159,10 +171,11 @@ def self.build_from_hash(attributes)
     # @return [Hash] Returns the object in the form of hash
     def to_hash
       hash = {}
-      self.class.attribute_map.each_pair do |attr, param|
+      # include attributes inherited from allOf parents (the nearest declaration wins)
+      self.class.acceptable_attribute_map.each_pair do |attr, param|
         value = self.send(attr)
         if value.nil?
-          is_nullable = self.class.openapi_nullable.include?(attr)
+          is_nullable = self.class.acceptable_openapi_nullable.include?(attr)
           next if !is_nullable || (is_nullable && !instance_variable_defined?(:"@#{attr}"))
         end
 
diff --git a/samples/client/petstore/ruby-autoload/lib/petstore/models/order.rb b/samples/client/petstore/ruby-autoload/lib/petstore/models/order.rb
index f7e7b4eb9117..8cebfcefa34e 100644
--- a/samples/client/petstore/ruby-autoload/lib/petstore/models/order.rb
+++ b/samples/client/petstore/ruby-autoload/lib/petstore/models/order.rb
@@ -90,6 +90,16 @@ def self.openapi_nullable
       ])
     end
 
+    # Returns attribute type mapping
+    def self.acceptable_openapi_types
+      openapi_types
+    end
+
+    # Returns the nullable attributes
+    def self.acceptable_openapi_nullable
+      openapi_nullable
+    end
+
     # Initializes the object
     # @param [Hash] attributes Model attributes in the form of hash
     def initialize(attributes = {})
@@ -191,18 +201,20 @@ def hash
     def self.build_from_hash(attributes)
       return nil unless attributes.is_a?(Hash)
       attributes = attributes.transform_keys(&:to_sym)
+      # include attributes inherited from allOf parents (the nearest declaration wins)
+      map = acceptable_attribute_map
       transformed_hash = {}
-      openapi_types.each_pair do |key, type|
-        if attributes.key?(attribute_map[key]) && attributes[attribute_map[key]].nil?
+      acceptable_openapi_types.each_pair do |key, type|
+        if attributes.key?(map[key]) && attributes[map[key]].nil?
           transformed_hash["#{key}"] = nil
         elsif type =~ /\AArray<(.*)>/i
           # check to ensure the input is an array given that the attribute
           # is documented as an array but the input is not
-          if attributes[attribute_map[key]].is_a?(Array)
-            transformed_hash["#{key}"] = attributes[attribute_map[key]].map { |v| _deserialize($1, v) }
+          if attributes[map[key]].is_a?(Array)
+            transformed_hash["#{key}"] = attributes[map[key]].map { |v| _deserialize($1, v) }
           end
-        elsif !attributes[attribute_map[key]].nil?
-          transformed_hash["#{key}"] = _deserialize(type, attributes[attribute_map[key]])
+        elsif !attributes[map[key]].nil?
+          transformed_hash["#{key}"] = _deserialize(type, attributes[map[key]])
         end
       end
       new(transformed_hash)
@@ -212,10 +224,11 @@ def self.build_from_hash(attributes)
     # @return [Hash] Returns the object in the form of hash
     def to_hash
       hash = {}
-      self.class.attribute_map.each_pair do |attr, param|
+      # include attributes inherited from allOf parents (the nearest declaration wins)
+      self.class.acceptable_attribute_map.each_pair do |attr, param|
         value = self.send(attr)
         if value.nil?
-          is_nullable = self.class.openapi_nullable.include?(attr)
+          is_nullable = self.class.acceptable_openapi_nullable.include?(attr)
           next if !is_nullable || (is_nullable && !instance_variable_defined?(:"@#{attr}"))
         end
 
diff --git a/samples/client/petstore/ruby-autoload/lib/petstore/models/outer_composite.rb b/samples/client/petstore/ruby-autoload/lib/petstore/models/outer_composite.rb
index 2245e8512600..afa9203ebde9 100644
--- a/samples/client/petstore/ruby-autoload/lib/petstore/models/outer_composite.rb
+++ b/samples/client/petstore/ruby-autoload/lib/petstore/models/outer_composite.rb
@@ -55,6 +55,16 @@ def self.openapi_nullable
       ])
     end
 
+    # Returns attribute type mapping
+    def self.acceptable_openapi_types
+      openapi_types
+    end
+
+    # Returns the nullable attributes
+    def self.acceptable_openapi_nullable
+      openapi_nullable
+    end
+
     # Initializes the object
     # @param [Hash] attributes Model attributes in the form of hash
     def initialize(attributes = {})
@@ -127,18 +137,20 @@ def hash
     def self.build_from_hash(attributes)
       return nil unless attributes.is_a?(Hash)
       attributes = attributes.transform_keys(&:to_sym)
+      # include attributes inherited from allOf parents (the nearest declaration wins)
+      map = acceptable_attribute_map
       transformed_hash = {}
-      openapi_types.each_pair do |key, type|
-        if attributes.key?(attribute_map[key]) && attributes[attribute_map[key]].nil?
+      acceptable_openapi_types.each_pair do |key, type|
+        if attributes.key?(map[key]) && attributes[map[key]].nil?
           transformed_hash["#{key}"] = nil
         elsif type =~ /\AArray<(.*)>/i
           # check to ensure the input is an array given that the attribute
           # is documented as an array but the input is not
-          if attributes[attribute_map[key]].is_a?(Array)
-            transformed_hash["#{key}"] = attributes[attribute_map[key]].map { |v| _deserialize($1, v) }
+          if attributes[map[key]].is_a?(Array)
+            transformed_hash["#{key}"] = attributes[map[key]].map { |v| _deserialize($1, v) }
           end
-        elsif !attributes[attribute_map[key]].nil?
-          transformed_hash["#{key}"] = _deserialize(type, attributes[attribute_map[key]])
+        elsif !attributes[map[key]].nil?
+          transformed_hash["#{key}"] = _deserialize(type, attributes[map[key]])
         end
       end
       new(transformed_hash)
@@ -148,10 +160,11 @@ def self.build_from_hash(attributes)
     # @return [Hash] Returns the object in the form of hash
     def to_hash
       hash = {}
-      self.class.attribute_map.each_pair do |attr, param|
+      # include attributes inherited from allOf parents (the nearest declaration wins)
+      self.class.acceptable_attribute_map.each_pair do |attr, param|
         value = self.send(attr)
         if value.nil?
-          is_nullable = self.class.openapi_nullable.include?(attr)
+          is_nullable = self.class.acceptable_openapi_nullable.include?(attr)
           next if !is_nullable || (is_nullable && !instance_variable_defined?(:"@#{attr}"))
         end
 
diff --git a/samples/client/petstore/ruby-autoload/lib/petstore/models/outer_object_with_enum_property.rb b/samples/client/petstore/ruby-autoload/lib/petstore/models/outer_object_with_enum_property.rb
index 8ffad20f8d89..1fd79229d4f6 100644
--- a/samples/client/petstore/ruby-autoload/lib/petstore/models/outer_object_with_enum_property.rb
+++ b/samples/client/petstore/ruby-autoload/lib/petstore/models/outer_object_with_enum_property.rb
@@ -69,6 +69,16 @@ def self.openapi_nullable
       ])
     end
 
+    # Returns attribute type mapping
+    def self.acceptable_openapi_types
+      openapi_types
+    end
+
+    # Returns the nullable attributes
+    def self.acceptable_openapi_nullable
+      openapi_nullable
+    end
+
     # Initializes the object
     # @param [Hash] attributes Model attributes in the form of hash
     def initialize(attributes = {})
@@ -148,18 +158,20 @@ def hash
     def self.build_from_hash(attributes)
       return nil unless attributes.is_a?(Hash)
       attributes = attributes.transform_keys(&:to_sym)
+      # include attributes inherited from allOf parents (the nearest declaration wins)
+      map = acceptable_attribute_map
       transformed_hash = {}
-      openapi_types.each_pair do |key, type|
-        if attributes.key?(attribute_map[key]) && attributes[attribute_map[key]].nil?
+      acceptable_openapi_types.each_pair do |key, type|
+        if attributes.key?(map[key]) && attributes[map[key]].nil?
           transformed_hash["#{key}"] = nil
         elsif type =~ /\AArray<(.*)>/i
           # check to ensure the input is an array given that the attribute
           # is documented as an array but the input is not
-          if attributes[attribute_map[key]].is_a?(Array)
-            transformed_hash["#{key}"] = attributes[attribute_map[key]].map { |v| _deserialize($1, v) }
+          if attributes[map[key]].is_a?(Array)
+            transformed_hash["#{key}"] = attributes[map[key]].map { |v| _deserialize($1, v) }
           end
-        elsif !attributes[attribute_map[key]].nil?
-          transformed_hash["#{key}"] = _deserialize(type, attributes[attribute_map[key]])
+        elsif !attributes[map[key]].nil?
+          transformed_hash["#{key}"] = _deserialize(type, attributes[map[key]])
         end
       end
       new(transformed_hash)
@@ -169,10 +181,11 @@ def self.build_from_hash(attributes)
     # @return [Hash] Returns the object in the form of hash
     def to_hash
       hash = {}
-      self.class.attribute_map.each_pair do |attr, param|
+      # include attributes inherited from allOf parents (the nearest declaration wins)
+      self.class.acceptable_attribute_map.each_pair do |attr, param|
         value = self.send(attr)
         if value.nil?
-          is_nullable = self.class.openapi_nullable.include?(attr)
+          is_nullable = self.class.acceptable_openapi_nullable.include?(attr)
           next if !is_nullable || (is_nullable && !instance_variable_defined?(:"@#{attr}"))
         end
 
diff --git a/samples/client/petstore/ruby-autoload/lib/petstore/models/parent_with_nullable.rb b/samples/client/petstore/ruby-autoload/lib/petstore/models/parent_with_nullable.rb
index dde93af94488..5af979aaa167 100644
--- a/samples/client/petstore/ruby-autoload/lib/petstore/models/parent_with_nullable.rb
+++ b/samples/client/petstore/ruby-autoload/lib/petstore/models/parent_with_nullable.rb
@@ -74,6 +74,16 @@ def self.openapi_nullable
       ])
     end
 
+    # Returns attribute type mapping
+    def self.acceptable_openapi_types
+      openapi_types
+    end
+
+    # Returns the nullable attributes
+    def self.acceptable_openapi_nullable
+      openapi_nullable
+    end
+
     # discriminator's property name in OpenAPI v3
     def self.openapi_discriminator_name
       :'type'
@@ -158,18 +168,20 @@ def hash
     def self.build_from_hash(attributes)
       return nil unless attributes.is_a?(Hash)
       attributes = attributes.transform_keys(&:to_sym)
+      # include attributes inherited from allOf parents (the nearest declaration wins)
+      map = acceptable_attribute_map
       transformed_hash = {}
-      openapi_types.each_pair do |key, type|
-        if attributes.key?(attribute_map[key]) && attributes[attribute_map[key]].nil?
+      acceptable_openapi_types.each_pair do |key, type|
+        if attributes.key?(map[key]) && attributes[map[key]].nil?
           transformed_hash["#{key}"] = nil
         elsif type =~ /\AArray<(.*)>/i
           # check to ensure the input is an array given that the attribute
           # is documented as an array but the input is not
-          if attributes[attribute_map[key]].is_a?(Array)
-            transformed_hash["#{key}"] = attributes[attribute_map[key]].map { |v| _deserialize($1, v) }
+          if attributes[map[key]].is_a?(Array)
+            transformed_hash["#{key}"] = attributes[map[key]].map { |v| _deserialize($1, v) }
           end
-        elsif !attributes[attribute_map[key]].nil?
-          transformed_hash["#{key}"] = _deserialize(type, attributes[attribute_map[key]])
+        elsif !attributes[map[key]].nil?
+          transformed_hash["#{key}"] = _deserialize(type, attributes[map[key]])
         end
       end
       new(transformed_hash)
@@ -179,10 +191,11 @@ def self.build_from_hash(attributes)
     # @return [Hash] Returns the object in the form of hash
     def to_hash
       hash = {}
-      self.class.attribute_map.each_pair do |attr, param|
+      # include attributes inherited from allOf parents (the nearest declaration wins)
+      self.class.acceptable_attribute_map.each_pair do |attr, param|
         value = self.send(attr)
         if value.nil?
-          is_nullable = self.class.openapi_nullable.include?(attr)
+          is_nullable = self.class.acceptable_openapi_nullable.include?(attr)
           next if !is_nullable || (is_nullable && !instance_variable_defined?(:"@#{attr}"))
         end
 
diff --git a/samples/client/petstore/ruby-autoload/lib/petstore/models/pet.rb b/samples/client/petstore/ruby-autoload/lib/petstore/models/pet.rb
index e3594a1fb052..5a86112a15cf 100644
--- a/samples/client/petstore/ruby-autoload/lib/petstore/models/pet.rb
+++ b/samples/client/petstore/ruby-autoload/lib/petstore/models/pet.rb
@@ -90,6 +90,16 @@ def self.openapi_nullable
       ])
     end
 
+    # Returns attribute type mapping
+    def self.acceptable_openapi_types
+      openapi_types
+    end
+
+    # Returns the nullable attributes
+    def self.acceptable_openapi_nullable
+      openapi_nullable
+    end
+
     # Initializes the object
     # @param [Hash] attributes Model attributes in the form of hash
     def initialize(attributes = {})
@@ -227,18 +237,20 @@ def hash
     def self.build_from_hash(attributes)
       return nil unless attributes.is_a?(Hash)
       attributes = attributes.transform_keys(&:to_sym)
+      # include attributes inherited from allOf parents (the nearest declaration wins)
+      map = acceptable_attribute_map
       transformed_hash = {}
-      openapi_types.each_pair do |key, type|
-        if attributes.key?(attribute_map[key]) && attributes[attribute_map[key]].nil?
+      acceptable_openapi_types.each_pair do |key, type|
+        if attributes.key?(map[key]) && attributes[map[key]].nil?
           transformed_hash["#{key}"] = nil
         elsif type =~ /\AArray<(.*)>/i
           # check to ensure the input is an array given that the attribute
           # is documented as an array but the input is not
-          if attributes[attribute_map[key]].is_a?(Array)
-            transformed_hash["#{key}"] = attributes[attribute_map[key]].map { |v| _deserialize($1, v) }
+          if attributes[map[key]].is_a?(Array)
+            transformed_hash["#{key}"] = attributes[map[key]].map { |v| _deserialize($1, v) }
           end
-        elsif !attributes[attribute_map[key]].nil?
-          transformed_hash["#{key}"] = _deserialize(type, attributes[attribute_map[key]])
+        elsif !attributes[map[key]].nil?
+          transformed_hash["#{key}"] = _deserialize(type, attributes[map[key]])
         end
       end
       new(transformed_hash)
@@ -248,10 +260,11 @@ def self.build_from_hash(attributes)
     # @return [Hash] Returns the object in the form of hash
     def to_hash
       hash = {}
-      self.class.attribute_map.each_pair do |attr, param|
+      # include attributes inherited from allOf parents (the nearest declaration wins)
+      self.class.acceptable_attribute_map.each_pair do |attr, param|
         value = self.send(attr)
         if value.nil?
-          is_nullable = self.class.openapi_nullable.include?(attr)
+          is_nullable = self.class.acceptable_openapi_nullable.include?(attr)
           next if !is_nullable || (is_nullable && !instance_variable_defined?(:"@#{attr}"))
         end
 
diff --git a/samples/client/petstore/ruby-autoload/lib/petstore/models/read_only_first.rb b/samples/client/petstore/ruby-autoload/lib/petstore/models/read_only_first.rb
index c2121474ebb7..d008b4369a91 100644
--- a/samples/client/petstore/ruby-autoload/lib/petstore/models/read_only_first.rb
+++ b/samples/client/petstore/ruby-autoload/lib/petstore/models/read_only_first.rb
@@ -51,6 +51,16 @@ def self.openapi_nullable
       ])
     end
 
+    # Returns attribute type mapping
+    def self.acceptable_openapi_types
+      openapi_types
+    end
+
+    # Returns the nullable attributes
+    def self.acceptable_openapi_nullable
+      openapi_nullable
+    end
+
     # Initializes the object
     # @param [Hash] attributes Model attributes in the form of hash
     def initialize(attributes = {})
@@ -118,18 +128,20 @@ def hash
     def self.build_from_hash(attributes)
       return nil unless attributes.is_a?(Hash)
       attributes = attributes.transform_keys(&:to_sym)
+      # include attributes inherited from allOf parents (the nearest declaration wins)
+      map = acceptable_attribute_map
       transformed_hash = {}
-      openapi_types.each_pair do |key, type|
-        if attributes.key?(attribute_map[key]) && attributes[attribute_map[key]].nil?
+      acceptable_openapi_types.each_pair do |key, type|
+        if attributes.key?(map[key]) && attributes[map[key]].nil?
           transformed_hash["#{key}"] = nil
         elsif type =~ /\AArray<(.*)>/i
           # check to ensure the input is an array given that the attribute
           # is documented as an array but the input is not
-          if attributes[attribute_map[key]].is_a?(Array)
-            transformed_hash["#{key}"] = attributes[attribute_map[key]].map { |v| _deserialize($1, v) }
+          if attributes[map[key]].is_a?(Array)
+            transformed_hash["#{key}"] = attributes[map[key]].map { |v| _deserialize($1, v) }
           end
-        elsif !attributes[attribute_map[key]].nil?
-          transformed_hash["#{key}"] = _deserialize(type, attributes[attribute_map[key]])
+        elsif !attributes[map[key]].nil?
+          transformed_hash["#{key}"] = _deserialize(type, attributes[map[key]])
         end
       end
       new(transformed_hash)
@@ -139,10 +151,11 @@ def self.build_from_hash(attributes)
     # @return [Hash] Returns the object in the form of hash
     def to_hash
       hash = {}
-      self.class.attribute_map.each_pair do |attr, param|
+      # include attributes inherited from allOf parents (the nearest declaration wins)
+      self.class.acceptable_attribute_map.each_pair do |attr, param|
         value = self.send(attr)
         if value.nil?
-          is_nullable = self.class.openapi_nullable.include?(attr)
+          is_nullable = self.class.acceptable_openapi_nullable.include?(attr)
           next if !is_nullable || (is_nullable && !instance_variable_defined?(:"@#{attr}"))
         end
 
diff --git a/samples/client/petstore/ruby-autoload/lib/petstore/models/special_model_name.rb b/samples/client/petstore/ruby-autoload/lib/petstore/models/special_model_name.rb
index 9569fbfd13dd..b6d4135991be 100644
--- a/samples/client/petstore/ruby-autoload/lib/petstore/models/special_model_name.rb
+++ b/samples/client/petstore/ruby-autoload/lib/petstore/models/special_model_name.rb
@@ -47,6 +47,16 @@ def self.openapi_nullable
       ])
     end
 
+    # Returns attribute type mapping
+    def self.acceptable_openapi_types
+      openapi_types
+    end
+
+    # Returns the nullable attributes
+    def self.acceptable_openapi_nullable
+      openapi_nullable
+    end
+
     # Initializes the object
     # @param [Hash] attributes Model attributes in the form of hash
     def initialize(attributes = {})
@@ -109,18 +119,20 @@ def hash
     def self.build_from_hash(attributes)
       return nil unless attributes.is_a?(Hash)
       attributes = attributes.transform_keys(&:to_sym)
+      # include attributes inherited from allOf parents (the nearest declaration wins)
+      map = acceptable_attribute_map
       transformed_hash = {}
-      openapi_types.each_pair do |key, type|
-        if attributes.key?(attribute_map[key]) && attributes[attribute_map[key]].nil?
+      acceptable_openapi_types.each_pair do |key, type|
+        if attributes.key?(map[key]) && attributes[map[key]].nil?
           transformed_hash["#{key}"] = nil
         elsif type =~ /\AArray<(.*)>/i
           # check to ensure the input is an array given that the attribute
           # is documented as an array but the input is not
-          if attributes[attribute_map[key]].is_a?(Array)
-            transformed_hash["#{key}"] = attributes[attribute_map[key]].map { |v| _deserialize($1, v) }
+          if attributes[map[key]].is_a?(Array)
+            transformed_hash["#{key}"] = attributes[map[key]].map { |v| _deserialize($1, v) }
           end
-        elsif !attributes[attribute_map[key]].nil?
-          transformed_hash["#{key}"] = _deserialize(type, attributes[attribute_map[key]])
+        elsif !attributes[map[key]].nil?
+          transformed_hash["#{key}"] = _deserialize(type, attributes[map[key]])
         end
       end
       new(transformed_hash)
@@ -130,10 +142,11 @@ def self.build_from_hash(attributes)
     # @return [Hash] Returns the object in the form of hash
     def to_hash
       hash = {}
-      self.class.attribute_map.each_pair do |attr, param|
+      # include attributes inherited from allOf parents (the nearest declaration wins)
+      self.class.acceptable_attribute_map.each_pair do |attr, param|
         value = self.send(attr)
         if value.nil?
-          is_nullable = self.class.openapi_nullable.include?(attr)
+          is_nullable = self.class.acceptable_openapi_nullable.include?(attr)
           next if !is_nullable || (is_nullable && !instance_variable_defined?(:"@#{attr}"))
         end
 
diff --git a/samples/client/petstore/ruby-autoload/lib/petstore/models/tag.rb b/samples/client/petstore/ruby-autoload/lib/petstore/models/tag.rb
index 6d6f57468181..22589f4e58b3 100644
--- a/samples/client/petstore/ruby-autoload/lib/petstore/models/tag.rb
+++ b/samples/client/petstore/ruby-autoload/lib/petstore/models/tag.rb
@@ -51,6 +51,16 @@ def self.openapi_nullable
       ])
     end
 
+    # Returns attribute type mapping
+    def self.acceptable_openapi_types
+      openapi_types
+    end
+
+    # Returns the nullable attributes
+    def self.acceptable_openapi_nullable
+      openapi_nullable
+    end
+
     # Initializes the object
     # @param [Hash] attributes Model attributes in the form of hash
     def initialize(attributes = {})
@@ -118,18 +128,20 @@ def hash
     def self.build_from_hash(attributes)
       return nil unless attributes.is_a?(Hash)
       attributes = attributes.transform_keys(&:to_sym)
+      # include attributes inherited from allOf parents (the nearest declaration wins)
+      map = acceptable_attribute_map
       transformed_hash = {}
-      openapi_types.each_pair do |key, type|
-        if attributes.key?(attribute_map[key]) && attributes[attribute_map[key]].nil?
+      acceptable_openapi_types.each_pair do |key, type|
+        if attributes.key?(map[key]) && attributes[map[key]].nil?
           transformed_hash["#{key}"] = nil
         elsif type =~ /\AArray<(.*)>/i
           # check to ensure the input is an array given that the attribute
           # is documented as an array but the input is not
-          if attributes[attribute_map[key]].is_a?(Array)
-            transformed_hash["#{key}"] = attributes[attribute_map[key]].map { |v| _deserialize($1, v) }
+          if attributes[map[key]].is_a?(Array)
+            transformed_hash["#{key}"] = attributes[map[key]].map { |v| _deserialize($1, v) }
           end
-        elsif !attributes[attribute_map[key]].nil?
-          transformed_hash["#{key}"] = _deserialize(type, attributes[attribute_map[key]])
+        elsif !attributes[map[key]].nil?
+          transformed_hash["#{key}"] = _deserialize(type, attributes[map[key]])
         end
       end
       new(transformed_hash)
@@ -139,10 +151,11 @@ def self.build_from_hash(attributes)
     # @return [Hash] Returns the object in the form of hash
     def to_hash
       hash = {}
-      self.class.attribute_map.each_pair do |attr, param|
+      # include attributes inherited from allOf parents (the nearest declaration wins)
+      self.class.acceptable_attribute_map.each_pair do |attr, param|
         value = self.send(attr)
         if value.nil?
-          is_nullable = self.class.openapi_nullable.include?(attr)
+          is_nullable = self.class.acceptable_openapi_nullable.include?(attr)
           next if !is_nullable || (is_nullable && !instance_variable_defined?(:"@#{attr}"))
         end
 
diff --git a/samples/client/petstore/ruby-autoload/lib/petstore/models/test_inline_freeform_additional_properties_request.rb b/samples/client/petstore/ruby-autoload/lib/petstore/models/test_inline_freeform_additional_properties_request.rb
index dc481c119d22..9e52e64e286b 100644
--- a/samples/client/petstore/ruby-autoload/lib/petstore/models/test_inline_freeform_additional_properties_request.rb
+++ b/samples/client/petstore/ruby-autoload/lib/petstore/models/test_inline_freeform_additional_properties_request.rb
@@ -47,6 +47,16 @@ def self.openapi_nullable
       ])
     end
 
+    # Returns attribute type mapping
+    def self.acceptable_openapi_types
+      openapi_types
+    end
+
+    # Returns the nullable attributes
+    def self.acceptable_openapi_nullable
+      openapi_nullable
+    end
+
     # Initializes the object
     # @param [Hash] attributes Model attributes in the form of hash
     def initialize(attributes = {})
@@ -109,18 +119,20 @@ def hash
     def self.build_from_hash(attributes)
       return nil unless attributes.is_a?(Hash)
       attributes = attributes.transform_keys(&:to_sym)
+      # include attributes inherited from allOf parents (the nearest declaration wins)
+      map = acceptable_attribute_map
       transformed_hash = {}
-      openapi_types.each_pair do |key, type|
-        if attributes.key?(attribute_map[key]) && attributes[attribute_map[key]].nil?
+      acceptable_openapi_types.each_pair do |key, type|
+        if attributes.key?(map[key]) && attributes[map[key]].nil?
           transformed_hash["#{key}"] = nil
         elsif type =~ /\AArray<(.*)>/i
           # check to ensure the input is an array given that the attribute
           # is documented as an array but the input is not
-          if attributes[attribute_map[key]].is_a?(Array)
-            transformed_hash["#{key}"] = attributes[attribute_map[key]].map { |v| _deserialize($1, v) }
+          if attributes[map[key]].is_a?(Array)
+            transformed_hash["#{key}"] = attributes[map[key]].map { |v| _deserialize($1, v) }
           end
-        elsif !attributes[attribute_map[key]].nil?
-          transformed_hash["#{key}"] = _deserialize(type, attributes[attribute_map[key]])
+        elsif !attributes[map[key]].nil?
+          transformed_hash["#{key}"] = _deserialize(type, attributes[map[key]])
         end
       end
       new(transformed_hash)
@@ -130,10 +142,11 @@ def self.build_from_hash(attributes)
     # @return [Hash] Returns the object in the form of hash
     def to_hash
       hash = {}
-      self.class.attribute_map.each_pair do |attr, param|
+      # include attributes inherited from allOf parents (the nearest declaration wins)
+      self.class.acceptable_attribute_map.each_pair do |attr, param|
         value = self.send(attr)
         if value.nil?
-          is_nullable = self.class.openapi_nullable.include?(attr)
+          is_nullable = self.class.acceptable_openapi_nullable.include?(attr)
           next if !is_nullable || (is_nullable && !instance_variable_defined?(:"@#{attr}"))
         end
 
diff --git a/samples/client/petstore/ruby-autoload/lib/petstore/models/user.rb b/samples/client/petstore/ruby-autoload/lib/petstore/models/user.rb
index 9b06f2ff6d7a..4b67db8214e2 100644
--- a/samples/client/petstore/ruby-autoload/lib/petstore/models/user.rb
+++ b/samples/client/petstore/ruby-autoload/lib/petstore/models/user.rb
@@ -76,6 +76,16 @@ def self.openapi_nullable
       ])
     end
 
+    # Returns attribute type mapping
+    def self.acceptable_openapi_types
+      openapi_types
+    end
+
+    # Returns the nullable attributes
+    def self.acceptable_openapi_nullable
+      openapi_nullable
+    end
+
     # Initializes the object
     # @param [Hash] attributes Model attributes in the form of hash
     def initialize(attributes = {})
@@ -173,18 +183,20 @@ def hash
     def self.build_from_hash(attributes)
       return nil unless attributes.is_a?(Hash)
       attributes = attributes.transform_keys(&:to_sym)
+      # include attributes inherited from allOf parents (the nearest declaration wins)
+      map = acceptable_attribute_map
       transformed_hash = {}
-      openapi_types.each_pair do |key, type|
-        if attributes.key?(attribute_map[key]) && attributes[attribute_map[key]].nil?
+      acceptable_openapi_types.each_pair do |key, type|
+        if attributes.key?(map[key]) && attributes[map[key]].nil?
           transformed_hash["#{key}"] = nil
         elsif type =~ /\AArray<(.*)>/i
           # check to ensure the input is an array given that the attribute
           # is documented as an array but the input is not
-          if attributes[attribute_map[key]].is_a?(Array)
-            transformed_hash["#{key}"] = attributes[attribute_map[key]].map { |v| _deserialize($1, v) }
+          if attributes[map[key]].is_a?(Array)
+            transformed_hash["#{key}"] = attributes[map[key]].map { |v| _deserialize($1, v) }
           end
-        elsif !attributes[attribute_map[key]].nil?
-          transformed_hash["#{key}"] = _deserialize(type, attributes[attribute_map[key]])
+        elsif !attributes[map[key]].nil?
+          transformed_hash["#{key}"] = _deserialize(type, attributes[map[key]])
         end
       end
       new(transformed_hash)
@@ -194,10 +206,11 @@ def self.build_from_hash(attributes)
     # @return [Hash] Returns the object in the form of hash
     def to_hash
       hash = {}
-      self.class.attribute_map.each_pair do |attr, param|
+      # include attributes inherited from allOf parents (the nearest declaration wins)
+      self.class.acceptable_attribute_map.each_pair do |attr, param|
         value = self.send(attr)
         if value.nil?
-          is_nullable = self.class.openapi_nullable.include?(attr)
+          is_nullable = self.class.acceptable_openapi_nullable.include?(attr)
           next if !is_nullable || (is_nullable && !instance_variable_defined?(:"@#{attr}"))
         end
 
diff --git a/samples/client/petstore/ruby-faraday/lib/petstore/models/additional_properties_class.rb b/samples/client/petstore/ruby-faraday/lib/petstore/models/additional_properties_class.rb
index 9b823593d156..a240cadf547e 100644
--- a/samples/client/petstore/ruby-faraday/lib/petstore/models/additional_properties_class.rb
+++ b/samples/client/petstore/ruby-faraday/lib/petstore/models/additional_properties_class.rb
@@ -51,6 +51,16 @@ def self.openapi_nullable
       ])
     end
 
+    # Returns attribute type mapping
+    def self.acceptable_openapi_types
+      openapi_types
+    end
+
+    # Returns the nullable attributes
+    def self.acceptable_openapi_nullable
+      openapi_nullable
+    end
+
     # Initializes the object
     # @param [Hash] attributes Model attributes in the form of hash
     def initialize(attributes = {})
@@ -122,18 +132,20 @@ def hash
     def self.build_from_hash(attributes)
       return nil unless attributes.is_a?(Hash)
       attributes = attributes.transform_keys(&:to_sym)
+      # include attributes inherited from allOf parents (the nearest declaration wins)
+      map = acceptable_attribute_map
       transformed_hash = {}
-      openapi_types.each_pair do |key, type|
-        if attributes.key?(attribute_map[key]) && attributes[attribute_map[key]].nil?
+      acceptable_openapi_types.each_pair do |key, type|
+        if attributes.key?(map[key]) && attributes[map[key]].nil?
           transformed_hash["#{key}"] = nil
         elsif type =~ /\AArray<(.*)>/i
           # check to ensure the input is an array given that the attribute
           # is documented as an array but the input is not
-          if attributes[attribute_map[key]].is_a?(Array)
-            transformed_hash["#{key}"] = attributes[attribute_map[key]].map { |v| _deserialize($1, v) }
+          if attributes[map[key]].is_a?(Array)
+            transformed_hash["#{key}"] = attributes[map[key]].map { |v| _deserialize($1, v) }
           end
-        elsif !attributes[attribute_map[key]].nil?
-          transformed_hash["#{key}"] = _deserialize(type, attributes[attribute_map[key]])
+        elsif !attributes[map[key]].nil?
+          transformed_hash["#{key}"] = _deserialize(type, attributes[map[key]])
         end
       end
       new(transformed_hash)
@@ -143,10 +155,11 @@ def self.build_from_hash(attributes)
     # @return [Hash] Returns the object in the form of hash
     def to_hash
       hash = {}
-      self.class.attribute_map.each_pair do |attr, param|
+      # include attributes inherited from allOf parents (the nearest declaration wins)
+      self.class.acceptable_attribute_map.each_pair do |attr, param|
         value = self.send(attr)
         if value.nil?
-          is_nullable = self.class.openapi_nullable.include?(attr)
+          is_nullable = self.class.acceptable_openapi_nullable.include?(attr)
           next if !is_nullable || (is_nullable && !instance_variable_defined?(:"@#{attr}"))
         end
 
diff --git a/samples/client/petstore/ruby-faraday/lib/petstore/models/all_of_with_single_ref.rb b/samples/client/petstore/ruby-faraday/lib/petstore/models/all_of_with_single_ref.rb
index 600c974fa1e5..9977e0212627 100644
--- a/samples/client/petstore/ruby-faraday/lib/petstore/models/all_of_with_single_ref.rb
+++ b/samples/client/petstore/ruby-faraday/lib/petstore/models/all_of_with_single_ref.rb
@@ -73,6 +73,16 @@ def self.openapi_nullable
       ])
     end
 
+    # Returns attribute type mapping
+    def self.acceptable_openapi_types
+      openapi_types
+    end
+
+    # Returns the nullable attributes
+    def self.acceptable_openapi_nullable
+      openapi_nullable
+    end
+
     # Initializes the object
     # @param [Hash] attributes Model attributes in the form of hash
     def initialize(attributes = {})
@@ -140,18 +150,20 @@ def hash
     def self.build_from_hash(attributes)
       return nil unless attributes.is_a?(Hash)
       attributes = attributes.transform_keys(&:to_sym)
+      # include attributes inherited from allOf parents (the nearest declaration wins)
+      map = acceptable_attribute_map
       transformed_hash = {}
-      openapi_types.each_pair do |key, type|
-        if attributes.key?(attribute_map[key]) && attributes[attribute_map[key]].nil?
+      acceptable_openapi_types.each_pair do |key, type|
+        if attributes.key?(map[key]) && attributes[map[key]].nil?
           transformed_hash["#{key}"] = nil
         elsif type =~ /\AArray<(.*)>/i
           # check to ensure the input is an array given that the attribute
           # is documented as an array but the input is not
-          if attributes[attribute_map[key]].is_a?(Array)
-            transformed_hash["#{key}"] = attributes[attribute_map[key]].map { |v| _deserialize($1, v) }
+          if attributes[map[key]].is_a?(Array)
+            transformed_hash["#{key}"] = attributes[map[key]].map { |v| _deserialize($1, v) }
           end
-        elsif !attributes[attribute_map[key]].nil?
-          transformed_hash["#{key}"] = _deserialize(type, attributes[attribute_map[key]])
+        elsif !attributes[map[key]].nil?
+          transformed_hash["#{key}"] = _deserialize(type, attributes[map[key]])
         end
       end
       new(transformed_hash)
@@ -161,10 +173,11 @@ def self.build_from_hash(attributes)
     # @return [Hash] Returns the object in the form of hash
     def to_hash
       hash = {}
-      self.class.attribute_map.each_pair do |attr, param|
+      # include attributes inherited from allOf parents (the nearest declaration wins)
+      self.class.acceptable_attribute_map.each_pair do |attr, param|
         value = self.send(attr)
         if value.nil?
-          is_nullable = self.class.openapi_nullable.include?(attr)
+          is_nullable = self.class.acceptable_openapi_nullable.include?(attr)
           next if !is_nullable || (is_nullable && !instance_variable_defined?(:"@#{attr}"))
         end
 
diff --git a/samples/client/petstore/ruby-faraday/lib/petstore/models/animal.rb b/samples/client/petstore/ruby-faraday/lib/petstore/models/animal.rb
index 21d89bccb837..b58dbb506d4e 100644
--- a/samples/client/petstore/ruby-faraday/lib/petstore/models/animal.rb
+++ b/samples/client/petstore/ruby-faraday/lib/petstore/models/animal.rb
@@ -51,6 +51,16 @@ def self.openapi_nullable
       ])
     end
 
+    # Returns attribute type mapping
+    def self.acceptable_openapi_types
+      openapi_types
+    end
+
+    # Returns the nullable attributes
+    def self.acceptable_openapi_nullable
+      openapi_nullable
+    end
+
     # discriminator's property name in OpenAPI v3
     def self.openapi_discriminator_name
       :'class_name'
@@ -142,18 +152,20 @@ def hash
     def self.build_from_hash(attributes)
       return nil unless attributes.is_a?(Hash)
       attributes = attributes.transform_keys(&:to_sym)
+      # include attributes inherited from allOf parents (the nearest declaration wins)
+      map = acceptable_attribute_map
       transformed_hash = {}
-      openapi_types.each_pair do |key, type|
-        if attributes.key?(attribute_map[key]) && attributes[attribute_map[key]].nil?
+      acceptable_openapi_types.each_pair do |key, type|
+        if attributes.key?(map[key]) && attributes[map[key]].nil?
           transformed_hash["#{key}"] = nil
         elsif type =~ /\AArray<(.*)>/i
           # check to ensure the input is an array given that the attribute
           # is documented as an array but the input is not
-          if attributes[attribute_map[key]].is_a?(Array)
-            transformed_hash["#{key}"] = attributes[attribute_map[key]].map { |v| _deserialize($1, v) }
+          if attributes[map[key]].is_a?(Array)
+            transformed_hash["#{key}"] = attributes[map[key]].map { |v| _deserialize($1, v) }
           end
-        elsif !attributes[attribute_map[key]].nil?
-          transformed_hash["#{key}"] = _deserialize(type, attributes[attribute_map[key]])
+        elsif !attributes[map[key]].nil?
+          transformed_hash["#{key}"] = _deserialize(type, attributes[map[key]])
         end
       end
       new(transformed_hash)
@@ -163,10 +175,11 @@ def self.build_from_hash(attributes)
     # @return [Hash] Returns the object in the form of hash
     def to_hash
       hash = {}
-      self.class.attribute_map.each_pair do |attr, param|
+      # include attributes inherited from allOf parents (the nearest declaration wins)
+      self.class.acceptable_attribute_map.each_pair do |attr, param|
         value = self.send(attr)
         if value.nil?
-          is_nullable = self.class.openapi_nullable.include?(attr)
+          is_nullable = self.class.acceptable_openapi_nullable.include?(attr)
           next if !is_nullable || (is_nullable && !instance_variable_defined?(:"@#{attr}"))
         end
 
diff --git a/samples/client/petstore/ruby-faraday/lib/petstore/models/api_response.rb b/samples/client/petstore/ruby-faraday/lib/petstore/models/api_response.rb
index bbbaf9358be2..6b8e2bf4005f 100644
--- a/samples/client/petstore/ruby-faraday/lib/petstore/models/api_response.rb
+++ b/samples/client/petstore/ruby-faraday/lib/petstore/models/api_response.rb
@@ -55,6 +55,16 @@ def self.openapi_nullable
       ])
     end
 
+    # Returns attribute type mapping
+    def self.acceptable_openapi_types
+      openapi_types
+    end
+
+    # Returns the nullable attributes
+    def self.acceptable_openapi_nullable
+      openapi_nullable
+    end
+
     # Initializes the object
     # @param [Hash] attributes Model attributes in the form of hash
     def initialize(attributes = {})
@@ -127,18 +137,20 @@ def hash
     def self.build_from_hash(attributes)
       return nil unless attributes.is_a?(Hash)
       attributes = attributes.transform_keys(&:to_sym)
+      # include attributes inherited from allOf parents (the nearest declaration wins)
+      map = acceptable_attribute_map
       transformed_hash = {}
-      openapi_types.each_pair do |key, type|
-        if attributes.key?(attribute_map[key]) && attributes[attribute_map[key]].nil?
+      acceptable_openapi_types.each_pair do |key, type|
+        if attributes.key?(map[key]) && attributes[map[key]].nil?
           transformed_hash["#{key}"] = nil
         elsif type =~ /\AArray<(.*)>/i
           # check to ensure the input is an array given that the attribute
           # is documented as an array but the input is not
-          if attributes[attribute_map[key]].is_a?(Array)
-            transformed_hash["#{key}"] = attributes[attribute_map[key]].map { |v| _deserialize($1, v) }
+          if attributes[map[key]].is_a?(Array)
+            transformed_hash["#{key}"] = attributes[map[key]].map { |v| _deserialize($1, v) }
           end
-        elsif !attributes[attribute_map[key]].nil?
-          transformed_hash["#{key}"] = _deserialize(type, attributes[attribute_map[key]])
+        elsif !attributes[map[key]].nil?
+          transformed_hash["#{key}"] = _deserialize(type, attributes[map[key]])
         end
       end
       new(transformed_hash)
@@ -148,10 +160,11 @@ def self.build_from_hash(attributes)
     # @return [Hash] Returns the object in the form of hash
     def to_hash
       hash = {}
-      self.class.attribute_map.each_pair do |attr, param|
+      # include attributes inherited from allOf parents (the nearest declaration wins)
+      self.class.acceptable_attribute_map.each_pair do |attr, param|
         value = self.send(attr)
         if value.nil?
-          is_nullable = self.class.openapi_nullable.include?(attr)
+          is_nullable = self.class.acceptable_openapi_nullable.include?(attr)
           next if !is_nullable || (is_nullable && !instance_variable_defined?(:"@#{attr}"))
         end
 
diff --git a/samples/client/petstore/ruby-faraday/lib/petstore/models/array_of_array_of_number_only.rb b/samples/client/petstore/ruby-faraday/lib/petstore/models/array_of_array_of_number_only.rb
index e20b1728d130..40b968094257 100644
--- a/samples/client/petstore/ruby-faraday/lib/petstore/models/array_of_array_of_number_only.rb
+++ b/samples/client/petstore/ruby-faraday/lib/petstore/models/array_of_array_of_number_only.rb
@@ -47,6 +47,16 @@ def self.openapi_nullable
       ])
     end
 
+    # Returns attribute type mapping
+    def self.acceptable_openapi_types
+      openapi_types
+    end
+
+    # Returns the nullable attributes
+    def self.acceptable_openapi_nullable
+      openapi_nullable
+    end
+
     # Initializes the object
     # @param [Hash] attributes Model attributes in the form of hash
     def initialize(attributes = {})
@@ -111,18 +121,20 @@ def hash
     def self.build_from_hash(attributes)
       return nil unless attributes.is_a?(Hash)
       attributes = attributes.transform_keys(&:to_sym)
+      # include attributes inherited from allOf parents (the nearest declaration wins)
+      map = acceptable_attribute_map
       transformed_hash = {}
-      openapi_types.each_pair do |key, type|
-        if attributes.key?(attribute_map[key]) && attributes[attribute_map[key]].nil?
+      acceptable_openapi_types.each_pair do |key, type|
+        if attributes.key?(map[key]) && attributes[map[key]].nil?
           transformed_hash["#{key}"] = nil
         elsif type =~ /\AArray<(.*)>/i
           # check to ensure the input is an array given that the attribute
           # is documented as an array but the input is not
-          if attributes[attribute_map[key]].is_a?(Array)
-            transformed_hash["#{key}"] = attributes[attribute_map[key]].map { |v| _deserialize($1, v) }
+          if attributes[map[key]].is_a?(Array)
+            transformed_hash["#{key}"] = attributes[map[key]].map { |v| _deserialize($1, v) }
           end
-        elsif !attributes[attribute_map[key]].nil?
-          transformed_hash["#{key}"] = _deserialize(type, attributes[attribute_map[key]])
+        elsif !attributes[map[key]].nil?
+          transformed_hash["#{key}"] = _deserialize(type, attributes[map[key]])
         end
       end
       new(transformed_hash)
@@ -132,10 +144,11 @@ def self.build_from_hash(attributes)
     # @return [Hash] Returns the object in the form of hash
     def to_hash
       hash = {}
-      self.class.attribute_map.each_pair do |attr, param|
+      # include attributes inherited from allOf parents (the nearest declaration wins)
+      self.class.acceptable_attribute_map.each_pair do |attr, param|
         value = self.send(attr)
         if value.nil?
-          is_nullable = self.class.openapi_nullable.include?(attr)
+          is_nullable = self.class.acceptable_openapi_nullable.include?(attr)
           next if !is_nullable || (is_nullable && !instance_variable_defined?(:"@#{attr}"))
         end
 
diff --git a/samples/client/petstore/ruby-faraday/lib/petstore/models/array_of_number_only.rb b/samples/client/petstore/ruby-faraday/lib/petstore/models/array_of_number_only.rb
index 63890ff64424..6b9bc3627785 100644
--- a/samples/client/petstore/ruby-faraday/lib/petstore/models/array_of_number_only.rb
+++ b/samples/client/petstore/ruby-faraday/lib/petstore/models/array_of_number_only.rb
@@ -47,6 +47,16 @@ def self.openapi_nullable
       ])
     end
 
+    # Returns attribute type mapping
+    def self.acceptable_openapi_types
+      openapi_types
+    end
+
+    # Returns the nullable attributes
+    def self.acceptable_openapi_nullable
+      openapi_nullable
+    end
+
     # Initializes the object
     # @param [Hash] attributes Model attributes in the form of hash
     def initialize(attributes = {})
@@ -111,18 +121,20 @@ def hash
     def self.build_from_hash(attributes)
       return nil unless attributes.is_a?(Hash)
       attributes = attributes.transform_keys(&:to_sym)
+      # include attributes inherited from allOf parents (the nearest declaration wins)
+      map = acceptable_attribute_map
       transformed_hash = {}
-      openapi_types.each_pair do |key, type|
-        if attributes.key?(attribute_map[key]) && attributes[attribute_map[key]].nil?
+      acceptable_openapi_types.each_pair do |key, type|
+        if attributes.key?(map[key]) && attributes[map[key]].nil?
           transformed_hash["#{key}"] = nil
         elsif type =~ /\AArray<(.*)>/i
           # check to ensure the input is an array given that the attribute
           # is documented as an array but the input is not
-          if attributes[attribute_map[key]].is_a?(Array)
-            transformed_hash["#{key}"] = attributes[attribute_map[key]].map { |v| _deserialize($1, v) }
+          if attributes[map[key]].is_a?(Array)
+            transformed_hash["#{key}"] = attributes[map[key]].map { |v| _deserialize($1, v) }
           end
-        elsif !attributes[attribute_map[key]].nil?
-          transformed_hash["#{key}"] = _deserialize(type, attributes[attribute_map[key]])
+        elsif !attributes[map[key]].nil?
+          transformed_hash["#{key}"] = _deserialize(type, attributes[map[key]])
         end
       end
       new(transformed_hash)
@@ -132,10 +144,11 @@ def self.build_from_hash(attributes)
     # @return [Hash] Returns the object in the form of hash
     def to_hash
       hash = {}
-      self.class.attribute_map.each_pair do |attr, param|
+      # include attributes inherited from allOf parents (the nearest declaration wins)
+      self.class.acceptable_attribute_map.each_pair do |attr, param|
         value = self.send(attr)
         if value.nil?
-          is_nullable = self.class.openapi_nullable.include?(attr)
+          is_nullable = self.class.acceptable_openapi_nullable.include?(attr)
           next if !is_nullable || (is_nullable && !instance_variable_defined?(:"@#{attr}"))
         end
 
diff --git a/samples/client/petstore/ruby-faraday/lib/petstore/models/array_test.rb b/samples/client/petstore/ruby-faraday/lib/petstore/models/array_test.rb
index c74060151e07..fc5e9d297766 100644
--- a/samples/client/petstore/ruby-faraday/lib/petstore/models/array_test.rb
+++ b/samples/client/petstore/ruby-faraday/lib/petstore/models/array_test.rb
@@ -55,6 +55,16 @@ def self.openapi_nullable
       ])
     end
 
+    # Returns attribute type mapping
+    def self.acceptable_openapi_types
+      openapi_types
+    end
+
+    # Returns the nullable attributes
+    def self.acceptable_openapi_nullable
+      openapi_nullable
+    end
+
     # Initializes the object
     # @param [Hash] attributes Model attributes in the form of hash
     def initialize(attributes = {})
@@ -161,18 +171,20 @@ def hash
     def self.build_from_hash(attributes)
       return nil unless attributes.is_a?(Hash)
       attributes = attributes.transform_keys(&:to_sym)
+      # include attributes inherited from allOf parents (the nearest declaration wins)
+      map = acceptable_attribute_map
       transformed_hash = {}
-      openapi_types.each_pair do |key, type|
-        if attributes.key?(attribute_map[key]) && attributes[attribute_map[key]].nil?
+      acceptable_openapi_types.each_pair do |key, type|
+        if attributes.key?(map[key]) && attributes[map[key]].nil?
           transformed_hash["#{key}"] = nil
         elsif type =~ /\AArray<(.*)>/i
           # check to ensure the input is an array given that the attribute
           # is documented as an array but the input is not
-          if attributes[attribute_map[key]].is_a?(Array)
-            transformed_hash["#{key}"] = attributes[attribute_map[key]].map { |v| _deserialize($1, v) }
+          if attributes[map[key]].is_a?(Array)
+            transformed_hash["#{key}"] = attributes[map[key]].map { |v| _deserialize($1, v) }
           end
-        elsif !attributes[attribute_map[key]].nil?
-          transformed_hash["#{key}"] = _deserialize(type, attributes[attribute_map[key]])
+        elsif !attributes[map[key]].nil?
+          transformed_hash["#{key}"] = _deserialize(type, attributes[map[key]])
         end
       end
       new(transformed_hash)
@@ -182,10 +194,11 @@ def self.build_from_hash(attributes)
     # @return [Hash] Returns the object in the form of hash
     def to_hash
       hash = {}
-      self.class.attribute_map.each_pair do |attr, param|
+      # include attributes inherited from allOf parents (the nearest declaration wins)
+      self.class.acceptable_attribute_map.each_pair do |attr, param|
         value = self.send(attr)
         if value.nil?
-          is_nullable = self.class.openapi_nullable.include?(attr)
+          is_nullable = self.class.acceptable_openapi_nullable.include?(attr)
           next if !is_nullable || (is_nullable && !instance_variable_defined?(:"@#{attr}"))
         end
 
diff --git a/samples/client/petstore/ruby-faraday/lib/petstore/models/capitalization.rb b/samples/client/petstore/ruby-faraday/lib/petstore/models/capitalization.rb
index e0bbeb211eb3..9031ca3f7d51 100644
--- a/samples/client/petstore/ruby-faraday/lib/petstore/models/capitalization.rb
+++ b/samples/client/petstore/ruby-faraday/lib/petstore/models/capitalization.rb
@@ -68,6 +68,16 @@ def self.openapi_nullable
       ])
     end
 
+    # Returns attribute type mapping
+    def self.acceptable_openapi_types
+      openapi_types
+    end
+
+    # Returns the nullable attributes
+    def self.acceptable_openapi_nullable
+      openapi_nullable
+    end
+
     # Initializes the object
     # @param [Hash] attributes Model attributes in the form of hash
     def initialize(attributes = {})
@@ -155,18 +165,20 @@ def hash
     def self.build_from_hash(attributes)
       return nil unless attributes.is_a?(Hash)
       attributes = attributes.transform_keys(&:to_sym)
+      # include attributes inherited from allOf parents (the nearest declaration wins)
+      map = acceptable_attribute_map
       transformed_hash = {}
-      openapi_types.each_pair do |key, type|
-        if attributes.key?(attribute_map[key]) && attributes[attribute_map[key]].nil?
+      acceptable_openapi_types.each_pair do |key, type|
+        if attributes.key?(map[key]) && attributes[map[key]].nil?
           transformed_hash["#{key}"] = nil
         elsif type =~ /\AArray<(.*)>/i
           # check to ensure the input is an array given that the attribute
           # is documented as an array but the input is not
-          if attributes[attribute_map[key]].is_a?(Array)
-            transformed_hash["#{key}"] = attributes[attribute_map[key]].map { |v| _deserialize($1, v) }
+          if attributes[map[key]].is_a?(Array)
+            transformed_hash["#{key}"] = attributes[map[key]].map { |v| _deserialize($1, v) }
           end
-        elsif !attributes[attribute_map[key]].nil?
-          transformed_hash["#{key}"] = _deserialize(type, attributes[attribute_map[key]])
+        elsif !attributes[map[key]].nil?
+          transformed_hash["#{key}"] = _deserialize(type, attributes[map[key]])
         end
       end
       new(transformed_hash)
@@ -176,10 +188,11 @@ def self.build_from_hash(attributes)
     # @return [Hash] Returns the object in the form of hash
     def to_hash
       hash = {}
-      self.class.attribute_map.each_pair do |attr, param|
+      # include attributes inherited from allOf parents (the nearest declaration wins)
+      self.class.acceptable_attribute_map.each_pair do |attr, param|
         value = self.send(attr)
         if value.nil?
-          is_nullable = self.class.openapi_nullable.include?(attr)
+          is_nullable = self.class.acceptable_openapi_nullable.include?(attr)
           next if !is_nullable || (is_nullable && !instance_variable_defined?(:"@#{attr}"))
         end
 
diff --git a/samples/client/petstore/ruby-faraday/lib/petstore/models/cat.rb b/samples/client/petstore/ruby-faraday/lib/petstore/models/cat.rb
index a84dc5038bef..a1f3de5272b6 100644
--- a/samples/client/petstore/ruby-faraday/lib/petstore/models/cat.rb
+++ b/samples/client/petstore/ruby-faraday/lib/petstore/models/cat.rb
@@ -47,6 +47,16 @@ def self.openapi_nullable
       ])
     end
 
+    # Returns attribute type mapping, including the ones defined in its parent(s)
+    def self.acceptable_openapi_types
+      superclass.acceptable_openapi_types.merge(openapi_types)
+    end
+
+    # Returns the nullable attributes, including the ones defined in its parent(s) that it does not redeclare
+    def self.acceptable_openapi_nullable
+      (superclass.acceptable_openapi_nullable - attribute_map.keys) | openapi_nullable
+    end
+
     # List of class defined in allOf (OpenAPI v3)
     def self.openapi_all_of
       [
@@ -118,20 +128,21 @@ def hash
     # @return [Object] Returns the model itself
     def self.build_from_hash(attributes)
       return nil unless attributes.is_a?(Hash)
-      super(attributes)
       attributes = attributes.transform_keys(&:to_sym)
+      # include attributes inherited from allOf parents (the nearest declaration wins)
+      map = acceptable_attribute_map
       transformed_hash = {}
-      openapi_types.each_pair do |key, type|
-        if attributes.key?(attribute_map[key]) && attributes[attribute_map[key]].nil?
+      acceptable_openapi_types.each_pair do |key, type|
+        if attributes.key?(map[key]) && attributes[map[key]].nil?
           transformed_hash["#{key}"] = nil
         elsif type =~ /\AArray<(.*)>/i
           # check to ensure the input is an array given that the attribute
           # is documented as an array but the input is not
-          if attributes[attribute_map[key]].is_a?(Array)
-            transformed_hash["#{key}"] = attributes[attribute_map[key]].map { |v| _deserialize($1, v) }
+          if attributes[map[key]].is_a?(Array)
+            transformed_hash["#{key}"] = attributes[map[key]].map { |v| _deserialize($1, v) }
           end
-        elsif !attributes[attribute_map[key]].nil?
-          transformed_hash["#{key}"] = _deserialize(type, attributes[attribute_map[key]])
+        elsif !attributes[map[key]].nil?
+          transformed_hash["#{key}"] = _deserialize(type, attributes[map[key]])
         end
       end
       new(transformed_hash)
@@ -140,11 +151,12 @@ def self.build_from_hash(attributes)
     # Returns the object in the form of hash
     # @return [Hash] Returns the object in the form of hash
     def to_hash
-      hash = super
-      self.class.attribute_map.each_pair do |attr, param|
+      hash = {}
+      # include attributes inherited from allOf parents (the nearest declaration wins)
+      self.class.acceptable_attribute_map.each_pair do |attr, param|
         value = self.send(attr)
         if value.nil?
-          is_nullable = self.class.openapi_nullable.include?(attr)
+          is_nullable = self.class.acceptable_openapi_nullable.include?(attr)
           next if !is_nullable || (is_nullable && !instance_variable_defined?(:"@#{attr}"))
         end
 
diff --git a/samples/client/petstore/ruby-faraday/lib/petstore/models/category.rb b/samples/client/petstore/ruby-faraday/lib/petstore/models/category.rb
index 2f2b7f1a5785..a5af1c3f9acc 100644
--- a/samples/client/petstore/ruby-faraday/lib/petstore/models/category.rb
+++ b/samples/client/petstore/ruby-faraday/lib/petstore/models/category.rb
@@ -51,6 +51,16 @@ def self.openapi_nullable
       ])
     end
 
+    # Returns attribute type mapping
+    def self.acceptable_openapi_types
+      openapi_types
+    end
+
+    # Returns the nullable attributes
+    def self.acceptable_openapi_nullable
+      openapi_nullable
+    end
+
     # Initializes the object
     # @param [Hash] attributes Model attributes in the form of hash
     def initialize(attributes = {})
@@ -135,18 +145,20 @@ def hash
     def self.build_from_hash(attributes)
       return nil unless attributes.is_a?(Hash)
       attributes = attributes.transform_keys(&:to_sym)
+      # include attributes inherited from allOf parents (the nearest declaration wins)
+      map = acceptable_attribute_map
       transformed_hash = {}
-      openapi_types.each_pair do |key, type|
-        if attributes.key?(attribute_map[key]) && attributes[attribute_map[key]].nil?
+      acceptable_openapi_types.each_pair do |key, type|
+        if attributes.key?(map[key]) && attributes[map[key]].nil?
           transformed_hash["#{key}"] = nil
         elsif type =~ /\AArray<(.*)>/i
           # check to ensure the input is an array given that the attribute
           # is documented as an array but the input is not
-          if attributes[attribute_map[key]].is_a?(Array)
-            transformed_hash["#{key}"] = attributes[attribute_map[key]].map { |v| _deserialize($1, v) }
+          if attributes[map[key]].is_a?(Array)
+            transformed_hash["#{key}"] = attributes[map[key]].map { |v| _deserialize($1, v) }
           end
-        elsif !attributes[attribute_map[key]].nil?
-          transformed_hash["#{key}"] = _deserialize(type, attributes[attribute_map[key]])
+        elsif !attributes[map[key]].nil?
+          transformed_hash["#{key}"] = _deserialize(type, attributes[map[key]])
         end
       end
       new(transformed_hash)
@@ -156,10 +168,11 @@ def self.build_from_hash(attributes)
     # @return [Hash] Returns the object in the form of hash
     def to_hash
       hash = {}
-      self.class.attribute_map.each_pair do |attr, param|
+      # include attributes inherited from allOf parents (the nearest declaration wins)
+      self.class.acceptable_attribute_map.each_pair do |attr, param|
         value = self.send(attr)
         if value.nil?
-          is_nullable = self.class.openapi_nullable.include?(attr)
+          is_nullable = self.class.acceptable_openapi_nullable.include?(attr)
           next if !is_nullable || (is_nullable && !instance_variable_defined?(:"@#{attr}"))
         end
 
diff --git a/samples/client/petstore/ruby-faraday/lib/petstore/models/class_model.rb b/samples/client/petstore/ruby-faraday/lib/petstore/models/class_model.rb
index fafd11df773a..4e611ee27f3e 100644
--- a/samples/client/petstore/ruby-faraday/lib/petstore/models/class_model.rb
+++ b/samples/client/petstore/ruby-faraday/lib/petstore/models/class_model.rb
@@ -48,6 +48,16 @@ def self.openapi_nullable
       ])
     end
 
+    # Returns attribute type mapping
+    def self.acceptable_openapi_types
+      openapi_types
+    end
+
+    # Returns the nullable attributes
+    def self.acceptable_openapi_nullable
+      openapi_nullable
+    end
+
     # Initializes the object
     # @param [Hash] attributes Model attributes in the form of hash
     def initialize(attributes = {})
@@ -110,18 +120,20 @@ def hash
     def self.build_from_hash(attributes)
       return nil unless attributes.is_a?(Hash)
       attributes = attributes.transform_keys(&:to_sym)
+      # include attributes inherited from allOf parents (the nearest declaration wins)
+      map = acceptable_attribute_map
       transformed_hash = {}
-      openapi_types.each_pair do |key, type|
-        if attributes.key?(attribute_map[key]) && attributes[attribute_map[key]].nil?
+      acceptable_openapi_types.each_pair do |key, type|
+        if attributes.key?(map[key]) && attributes[map[key]].nil?
           transformed_hash["#{key}"] = nil
         elsif type =~ /\AArray<(.*)>/i
           # check to ensure the input is an array given that the attribute
           # is documented as an array but the input is not
-          if attributes[attribute_map[key]].is_a?(Array)
-            transformed_hash["#{key}"] = attributes[attribute_map[key]].map { |v| _deserialize($1, v) }
+          if attributes[map[key]].is_a?(Array)
+            transformed_hash["#{key}"] = attributes[map[key]].map { |v| _deserialize($1, v) }
           end
-        elsif !attributes[attribute_map[key]].nil?
-          transformed_hash["#{key}"] = _deserialize(type, attributes[attribute_map[key]])
+        elsif !attributes[map[key]].nil?
+          transformed_hash["#{key}"] = _deserialize(type, attributes[map[key]])
         end
       end
       new(transformed_hash)
@@ -131,10 +143,11 @@ def self.build_from_hash(attributes)
     # @return [Hash] Returns the object in the form of hash
     def to_hash
       hash = {}
-      self.class.attribute_map.each_pair do |attr, param|
+      # include attributes inherited from allOf parents (the nearest declaration wins)
+      self.class.acceptable_attribute_map.each_pair do |attr, param|
         value = self.send(attr)
         if value.nil?
-          is_nullable = self.class.openapi_nullable.include?(attr)
+          is_nullable = self.class.acceptable_openapi_nullable.include?(attr)
           next if !is_nullable || (is_nullable && !instance_variable_defined?(:"@#{attr}"))
         end
 
diff --git a/samples/client/petstore/ruby-faraday/lib/petstore/models/client.rb b/samples/client/petstore/ruby-faraday/lib/petstore/models/client.rb
index a349b7251d7b..f775d0f1d542 100644
--- a/samples/client/petstore/ruby-faraday/lib/petstore/models/client.rb
+++ b/samples/client/petstore/ruby-faraday/lib/petstore/models/client.rb
@@ -47,6 +47,16 @@ def self.openapi_nullable
       ])
     end
 
+    # Returns attribute type mapping
+    def self.acceptable_openapi_types
+      openapi_types
+    end
+
+    # Returns the nullable attributes
+    def self.acceptable_openapi_nullable
+      openapi_nullable
+    end
+
     # Initializes the object
     # @param [Hash] attributes Model attributes in the form of hash
     def initialize(attributes = {})
@@ -109,18 +119,20 @@ def hash
     def self.build_from_hash(attributes)
       return nil unless attributes.is_a?(Hash)
       attributes = attributes.transform_keys(&:to_sym)
+      # include attributes inherited from allOf parents (the nearest declaration wins)
+      map = acceptable_attribute_map
       transformed_hash = {}
-      openapi_types.each_pair do |key, type|
-        if attributes.key?(attribute_map[key]) && attributes[attribute_map[key]].nil?
+      acceptable_openapi_types.each_pair do |key, type|
+        if attributes.key?(map[key]) && attributes[map[key]].nil?
           transformed_hash["#{key}"] = nil
         elsif type =~ /\AArray<(.*)>/i
           # check to ensure the input is an array given that the attribute
           # is documented as an array but the input is not
-          if attributes[attribute_map[key]].is_a?(Array)
-            transformed_hash["#{key}"] = attributes[attribute_map[key]].map { |v| _deserialize($1, v) }
+          if attributes[map[key]].is_a?(Array)
+            transformed_hash["#{key}"] = attributes[map[key]].map { |v| _deserialize($1, v) }
           end
-        elsif !attributes[attribute_map[key]].nil?
-          transformed_hash["#{key}"] = _deserialize(type, attributes[attribute_map[key]])
+        elsif !attributes[map[key]].nil?
+          transformed_hash["#{key}"] = _deserialize(type, attributes[map[key]])
         end
       end
       new(transformed_hash)
@@ -130,10 +142,11 @@ def self.build_from_hash(attributes)
     # @return [Hash] Returns the object in the form of hash
     def to_hash
       hash = {}
-      self.class.attribute_map.each_pair do |attr, param|
+      # include attributes inherited from allOf parents (the nearest declaration wins)
+      self.class.acceptable_attribute_map.each_pair do |attr, param|
         value = self.send(attr)
         if value.nil?
-          is_nullable = self.class.openapi_nullable.include?(attr)
+          is_nullable = self.class.acceptable_openapi_nullable.include?(attr)
           next if !is_nullable || (is_nullable && !instance_variable_defined?(:"@#{attr}"))
         end
 
diff --git a/samples/client/petstore/ruby-faraday/lib/petstore/models/deprecated_object.rb b/samples/client/petstore/ruby-faraday/lib/petstore/models/deprecated_object.rb
index 9f1ee6720cab..bdc86013c848 100644
--- a/samples/client/petstore/ruby-faraday/lib/petstore/models/deprecated_object.rb
+++ b/samples/client/petstore/ruby-faraday/lib/petstore/models/deprecated_object.rb
@@ -47,6 +47,16 @@ def self.openapi_nullable
       ])
     end
 
+    # Returns attribute type mapping
+    def self.acceptable_openapi_types
+      openapi_types
+    end
+
+    # Returns the nullable attributes
+    def self.acceptable_openapi_nullable
+      openapi_nullable
+    end
+
     # Initializes the object
     # @param [Hash] attributes Model attributes in the form of hash
     def initialize(attributes = {})
@@ -109,18 +119,20 @@ def hash
     def self.build_from_hash(attributes)
       return nil unless attributes.is_a?(Hash)
       attributes = attributes.transform_keys(&:to_sym)
+      # include attributes inherited from allOf parents (the nearest declaration wins)
+      map = acceptable_attribute_map
       transformed_hash = {}
-      openapi_types.each_pair do |key, type|
-        if attributes.key?(attribute_map[key]) && attributes[attribute_map[key]].nil?
+      acceptable_openapi_types.each_pair do |key, type|
+        if attributes.key?(map[key]) && attributes[map[key]].nil?
           transformed_hash["#{key}"] = nil
         elsif type =~ /\AArray<(.*)>/i
           # check to ensure the input is an array given that the attribute
           # is documented as an array but the input is not
-          if attributes[attribute_map[key]].is_a?(Array)
-            transformed_hash["#{key}"] = attributes[attribute_map[key]].map { |v| _deserialize($1, v) }
+          if attributes[map[key]].is_a?(Array)
+            transformed_hash["#{key}"] = attributes[map[key]].map { |v| _deserialize($1, v) }
           end
-        elsif !attributes[attribute_map[key]].nil?
-          transformed_hash["#{key}"] = _deserialize(type, attributes[attribute_map[key]])
+        elsif !attributes[map[key]].nil?
+          transformed_hash["#{key}"] = _deserialize(type, attributes[map[key]])
         end
       end
       new(transformed_hash)
@@ -130,10 +142,11 @@ def self.build_from_hash(attributes)
     # @return [Hash] Returns the object in the form of hash
     def to_hash
       hash = {}
-      self.class.attribute_map.each_pair do |attr, param|
+      # include attributes inherited from allOf parents (the nearest declaration wins)
+      self.class.acceptable_attribute_map.each_pair do |attr, param|
         value = self.send(attr)
         if value.nil?
-          is_nullable = self.class.openapi_nullable.include?(attr)
+          is_nullable = self.class.acceptable_openapi_nullable.include?(attr)
           next if !is_nullable || (is_nullable && !instance_variable_defined?(:"@#{attr}"))
         end
 
diff --git a/samples/client/petstore/ruby-faraday/lib/petstore/models/dog.rb b/samples/client/petstore/ruby-faraday/lib/petstore/models/dog.rb
index 522e1a72f47e..2e8f95136f9a 100644
--- a/samples/client/petstore/ruby-faraday/lib/petstore/models/dog.rb
+++ b/samples/client/petstore/ruby-faraday/lib/petstore/models/dog.rb
@@ -47,6 +47,16 @@ def self.openapi_nullable
       ])
     end
 
+    # Returns attribute type mapping, including the ones defined in its parent(s)
+    def self.acceptable_openapi_types
+      superclass.acceptable_openapi_types.merge(openapi_types)
+    end
+
+    # Returns the nullable attributes, including the ones defined in its parent(s) that it does not redeclare
+    def self.acceptable_openapi_nullable
+      (superclass.acceptable_openapi_nullable - attribute_map.keys) | openapi_nullable
+    end
+
     # List of class defined in allOf (OpenAPI v3)
     def self.openapi_all_of
       [
@@ -118,20 +128,21 @@ def hash
     # @return [Object] Returns the model itself
     def self.build_from_hash(attributes)
       return nil unless attributes.is_a?(Hash)
-      super(attributes)
       attributes = attributes.transform_keys(&:to_sym)
+      # include attributes inherited from allOf parents (the nearest declaration wins)
+      map = acceptable_attribute_map
       transformed_hash = {}
-      openapi_types.each_pair do |key, type|
-        if attributes.key?(attribute_map[key]) && attributes[attribute_map[key]].nil?
+      acceptable_openapi_types.each_pair do |key, type|
+        if attributes.key?(map[key]) && attributes[map[key]].nil?
           transformed_hash["#{key}"] = nil
         elsif type =~ /\AArray<(.*)>/i
           # check to ensure the input is an array given that the attribute
           # is documented as an array but the input is not
-          if attributes[attribute_map[key]].is_a?(Array)
-            transformed_hash["#{key}"] = attributes[attribute_map[key]].map { |v| _deserialize($1, v) }
+          if attributes[map[key]].is_a?(Array)
+            transformed_hash["#{key}"] = attributes[map[key]].map { |v| _deserialize($1, v) }
           end
-        elsif !attributes[attribute_map[key]].nil?
-          transformed_hash["#{key}"] = _deserialize(type, attributes[attribute_map[key]])
+        elsif !attributes[map[key]].nil?
+          transformed_hash["#{key}"] = _deserialize(type, attributes[map[key]])
         end
       end
       new(transformed_hash)
@@ -140,11 +151,12 @@ def self.build_from_hash(attributes)
     # Returns the object in the form of hash
     # @return [Hash] Returns the object in the form of hash
     def to_hash
-      hash = super
-      self.class.attribute_map.each_pair do |attr, param|
+      hash = {}
+      # include attributes inherited from allOf parents (the nearest declaration wins)
+      self.class.acceptable_attribute_map.each_pair do |attr, param|
         value = self.send(attr)
         if value.nil?
-          is_nullable = self.class.openapi_nullable.include?(attr)
+          is_nullable = self.class.acceptable_openapi_nullable.include?(attr)
           next if !is_nullable || (is_nullable && !instance_variable_defined?(:"@#{attr}"))
         end
 
diff --git a/samples/client/petstore/ruby-faraday/lib/petstore/models/enum_arrays.rb b/samples/client/petstore/ruby-faraday/lib/petstore/models/enum_arrays.rb
index 1f7c48bf859b..8058a6ac60bb 100644
--- a/samples/client/petstore/ruby-faraday/lib/petstore/models/enum_arrays.rb
+++ b/samples/client/petstore/ruby-faraday/lib/petstore/models/enum_arrays.rb
@@ -73,6 +73,16 @@ def self.openapi_nullable
       ])
     end
 
+    # Returns attribute type mapping
+    def self.acceptable_openapi_types
+      openapi_types
+    end
+
+    # Returns the nullable attributes
+    def self.acceptable_openapi_nullable
+      openapi_nullable
+    end
+
     # Initializes the object
     # @param [Hash] attributes Model attributes in the form of hash
     def initialize(attributes = {})
@@ -154,18 +164,20 @@ def hash
     def self.build_from_hash(attributes)
       return nil unless attributes.is_a?(Hash)
       attributes = attributes.transform_keys(&:to_sym)
+      # include attributes inherited from allOf parents (the nearest declaration wins)
+      map = acceptable_attribute_map
       transformed_hash = {}
-      openapi_types.each_pair do |key, type|
-        if attributes.key?(attribute_map[key]) && attributes[attribute_map[key]].nil?
+      acceptable_openapi_types.each_pair do |key, type|
+        if attributes.key?(map[key]) && attributes[map[key]].nil?
           transformed_hash["#{key}"] = nil
         elsif type =~ /\AArray<(.*)>/i
           # check to ensure the input is an array given that the attribute
           # is documented as an array but the input is not
-          if attributes[attribute_map[key]].is_a?(Array)
-            transformed_hash["#{key}"] = attributes[attribute_map[key]].map { |v| _deserialize($1, v) }
+          if attributes[map[key]].is_a?(Array)
+            transformed_hash["#{key}"] = attributes[map[key]].map { |v| _deserialize($1, v) }
           end
-        elsif !attributes[attribute_map[key]].nil?
-          transformed_hash["#{key}"] = _deserialize(type, attributes[attribute_map[key]])
+        elsif !attributes[map[key]].nil?
+          transformed_hash["#{key}"] = _deserialize(type, attributes[map[key]])
         end
       end
       new(transformed_hash)
@@ -175,10 +187,11 @@ def self.build_from_hash(attributes)
     # @return [Hash] Returns the object in the form of hash
     def to_hash
       hash = {}
-      self.class.attribute_map.each_pair do |attr, param|
+      # include attributes inherited from allOf parents (the nearest declaration wins)
+      self.class.acceptable_attribute_map.each_pair do |attr, param|
         value = self.send(attr)
         if value.nil?
-          is_nullable = self.class.openapi_nullable.include?(attr)
+          is_nullable = self.class.acceptable_openapi_nullable.include?(attr)
           next if !is_nullable || (is_nullable && !instance_variable_defined?(:"@#{attr}"))
         end
 
diff --git a/samples/client/petstore/ruby-faraday/lib/petstore/models/enum_test.rb b/samples/client/petstore/ruby-faraday/lib/petstore/models/enum_test.rb
index 5159875cb89b..3b3905c138a3 100644
--- a/samples/client/petstore/ruby-faraday/lib/petstore/models/enum_test.rb
+++ b/samples/client/petstore/ruby-faraday/lib/petstore/models/enum_test.rb
@@ -98,6 +98,16 @@ def self.openapi_nullable
       ])
     end
 
+    # Returns attribute type mapping
+    def self.acceptable_openapi_types
+      openapi_types
+    end
+
+    # Returns the nullable attributes
+    def self.acceptable_openapi_nullable
+      openapi_nullable
+    end
+
     # Initializes the object
     # @param [Hash] attributes Model attributes in the form of hash
     def initialize(attributes = {})
@@ -254,18 +264,20 @@ def hash
     def self.build_from_hash(attributes)
       return nil unless attributes.is_a?(Hash)
       attributes = attributes.transform_keys(&:to_sym)
+      # include attributes inherited from allOf parents (the nearest declaration wins)
+      map = acceptable_attribute_map
       transformed_hash = {}
-      openapi_types.each_pair do |key, type|
-        if attributes.key?(attribute_map[key]) && attributes[attribute_map[key]].nil?
+      acceptable_openapi_types.each_pair do |key, type|
+        if attributes.key?(map[key]) && attributes[map[key]].nil?
           transformed_hash["#{key}"] = nil
         elsif type =~ /\AArray<(.*)>/i
           # check to ensure the input is an array given that the attribute
           # is documented as an array but the input is not
-          if attributes[attribute_map[key]].is_a?(Array)
-            transformed_hash["#{key}"] = attributes[attribute_map[key]].map { |v| _deserialize($1, v) }
+          if attributes[map[key]].is_a?(Array)
+            transformed_hash["#{key}"] = attributes[map[key]].map { |v| _deserialize($1, v) }
           end
-        elsif !attributes[attribute_map[key]].nil?
-          transformed_hash["#{key}"] = _deserialize(type, attributes[attribute_map[key]])
+        elsif !attributes[map[key]].nil?
+          transformed_hash["#{key}"] = _deserialize(type, attributes[map[key]])
         end
       end
       new(transformed_hash)
@@ -275,10 +287,11 @@ def self.build_from_hash(attributes)
     # @return [Hash] Returns the object in the form of hash
     def to_hash
       hash = {}
-      self.class.attribute_map.each_pair do |attr, param|
+      # include attributes inherited from allOf parents (the nearest declaration wins)
+      self.class.acceptable_attribute_map.each_pair do |attr, param|
         value = self.send(attr)
         if value.nil?
-          is_nullable = self.class.openapi_nullable.include?(attr)
+          is_nullable = self.class.acceptable_openapi_nullable.include?(attr)
           next if !is_nullable || (is_nullable && !instance_variable_defined?(:"@#{attr}"))
         end
 
diff --git a/samples/client/petstore/ruby-faraday/lib/petstore/models/fake_big_decimal_map200_response.rb b/samples/client/petstore/ruby-faraday/lib/petstore/models/fake_big_decimal_map200_response.rb
index 6d5e47b59656..b7be6af6d90e 100644
--- a/samples/client/petstore/ruby-faraday/lib/petstore/models/fake_big_decimal_map200_response.rb
+++ b/samples/client/petstore/ruby-faraday/lib/petstore/models/fake_big_decimal_map200_response.rb
@@ -51,6 +51,16 @@ def self.openapi_nullable
       ])
     end
 
+    # Returns attribute type mapping
+    def self.acceptable_openapi_types
+      openapi_types
+    end
+
+    # Returns the nullable attributes
+    def self.acceptable_openapi_nullable
+      openapi_nullable
+    end
+
     # Initializes the object
     # @param [Hash] attributes Model attributes in the form of hash
     def initialize(attributes = {})
@@ -120,18 +130,20 @@ def hash
     def self.build_from_hash(attributes)
       return nil unless attributes.is_a?(Hash)
       attributes = attributes.transform_keys(&:to_sym)
+      # include attributes inherited from allOf parents (the nearest declaration wins)
+      map = acceptable_attribute_map
       transformed_hash = {}
-      openapi_types.each_pair do |key, type|
-        if attributes.key?(attribute_map[key]) && attributes[attribute_map[key]].nil?
+      acceptable_openapi_types.each_pair do |key, type|
+        if attributes.key?(map[key]) && attributes[map[key]].nil?
           transformed_hash["#{key}"] = nil
         elsif type =~ /\AArray<(.*)>/i
           # check to ensure the input is an array given that the attribute
           # is documented as an array but the input is not
-          if attributes[attribute_map[key]].is_a?(Array)
-            transformed_hash["#{key}"] = attributes[attribute_map[key]].map { |v| _deserialize($1, v) }
+          if attributes[map[key]].is_a?(Array)
+            transformed_hash["#{key}"] = attributes[map[key]].map { |v| _deserialize($1, v) }
           end
-        elsif !attributes[attribute_map[key]].nil?
-          transformed_hash["#{key}"] = _deserialize(type, attributes[attribute_map[key]])
+        elsif !attributes[map[key]].nil?
+          transformed_hash["#{key}"] = _deserialize(type, attributes[map[key]])
         end
       end
       new(transformed_hash)
@@ -141,10 +153,11 @@ def self.build_from_hash(attributes)
     # @return [Hash] Returns the object in the form of hash
     def to_hash
       hash = {}
-      self.class.attribute_map.each_pair do |attr, param|
+      # include attributes inherited from allOf parents (the nearest declaration wins)
+      self.class.acceptable_attribute_map.each_pair do |attr, param|
         value = self.send(attr)
         if value.nil?
-          is_nullable = self.class.openapi_nullable.include?(attr)
+          is_nullable = self.class.acceptable_openapi_nullable.include?(attr)
           next if !is_nullable || (is_nullable && !instance_variable_defined?(:"@#{attr}"))
         end
 
diff --git a/samples/client/petstore/ruby-faraday/lib/petstore/models/file.rb b/samples/client/petstore/ruby-faraday/lib/petstore/models/file.rb
index 219237eb3c07..4fac9978fcaa 100644
--- a/samples/client/petstore/ruby-faraday/lib/petstore/models/file.rb
+++ b/samples/client/petstore/ruby-faraday/lib/petstore/models/file.rb
@@ -49,6 +49,16 @@ def self.openapi_nullable
       ])
     end
 
+    # Returns attribute type mapping
+    def self.acceptable_openapi_types
+      openapi_types
+    end
+
+    # Returns the nullable attributes
+    def self.acceptable_openapi_nullable
+      openapi_nullable
+    end
+
     # Initializes the object
     # @param [Hash] attributes Model attributes in the form of hash
     def initialize(attributes = {})
@@ -111,18 +121,20 @@ def hash
     def self.build_from_hash(attributes)
       return nil unless attributes.is_a?(Hash)
       attributes = attributes.transform_keys(&:to_sym)
+      # include attributes inherited from allOf parents (the nearest declaration wins)
+      map = acceptable_attribute_map
       transformed_hash = {}
-      openapi_types.each_pair do |key, type|
-        if attributes.key?(attribute_map[key]) && attributes[attribute_map[key]].nil?
+      acceptable_openapi_types.each_pair do |key, type|
+        if attributes.key?(map[key]) && attributes[map[key]].nil?
           transformed_hash["#{key}"] = nil
         elsif type =~ /\AArray<(.*)>/i
           # check to ensure the input is an array given that the attribute
           # is documented as an array but the input is not
-          if attributes[attribute_map[key]].is_a?(Array)
-            transformed_hash["#{key}"] = attributes[attribute_map[key]].map { |v| _deserialize($1, v) }
+          if attributes[map[key]].is_a?(Array)
+            transformed_hash["#{key}"] = attributes[map[key]].map { |v| _deserialize($1, v) }
           end
-        elsif !attributes[attribute_map[key]].nil?
-          transformed_hash["#{key}"] = _deserialize(type, attributes[attribute_map[key]])
+        elsif !attributes[map[key]].nil?
+          transformed_hash["#{key}"] = _deserialize(type, attributes[map[key]])
         end
       end
       new(transformed_hash)
@@ -132,10 +144,11 @@ def self.build_from_hash(attributes)
     # @return [Hash] Returns the object in the form of hash
     def to_hash
       hash = {}
-      self.class.attribute_map.each_pair do |attr, param|
+      # include attributes inherited from allOf parents (the nearest declaration wins)
+      self.class.acceptable_attribute_map.each_pair do |attr, param|
         value = self.send(attr)
         if value.nil?
-          is_nullable = self.class.openapi_nullable.include?(attr)
+          is_nullable = self.class.acceptable_openapi_nullable.include?(attr)
           next if !is_nullable || (is_nullable && !instance_variable_defined?(:"@#{attr}"))
         end
 
diff --git a/samples/client/petstore/ruby-faraday/lib/petstore/models/file_schema_test_class.rb b/samples/client/petstore/ruby-faraday/lib/petstore/models/file_schema_test_class.rb
index 8fdab5a25e86..074c235ebe17 100644
--- a/samples/client/petstore/ruby-faraday/lib/petstore/models/file_schema_test_class.rb
+++ b/samples/client/petstore/ruby-faraday/lib/petstore/models/file_schema_test_class.rb
@@ -51,6 +51,16 @@ def self.openapi_nullable
       ])
     end
 
+    # Returns attribute type mapping
+    def self.acceptable_openapi_types
+      openapi_types
+    end
+
+    # Returns the nullable attributes
+    def self.acceptable_openapi_nullable
+      openapi_nullable
+    end
+
     # Initializes the object
     # @param [Hash] attributes Model attributes in the form of hash
     def initialize(attributes = {})
@@ -120,18 +130,20 @@ def hash
     def self.build_from_hash(attributes)
       return nil unless attributes.is_a?(Hash)
       attributes = attributes.transform_keys(&:to_sym)
+      # include attributes inherited from allOf parents (the nearest declaration wins)
+      map = acceptable_attribute_map
       transformed_hash = {}
-      openapi_types.each_pair do |key, type|
-        if attributes.key?(attribute_map[key]) && attributes[attribute_map[key]].nil?
+      acceptable_openapi_types.each_pair do |key, type|
+        if attributes.key?(map[key]) && attributes[map[key]].nil?
           transformed_hash["#{key}"] = nil
         elsif type =~ /\AArray<(.*)>/i
           # check to ensure the input is an array given that the attribute
           # is documented as an array but the input is not
-          if attributes[attribute_map[key]].is_a?(Array)
-            transformed_hash["#{key}"] = attributes[attribute_map[key]].map { |v| _deserialize($1, v) }
+          if attributes[map[key]].is_a?(Array)
+            transformed_hash["#{key}"] = attributes[map[key]].map { |v| _deserialize($1, v) }
           end
-        elsif !attributes[attribute_map[key]].nil?
-          transformed_hash["#{key}"] = _deserialize(type, attributes[attribute_map[key]])
+        elsif !attributes[map[key]].nil?
+          transformed_hash["#{key}"] = _deserialize(type, attributes[map[key]])
         end
       end
       new(transformed_hash)
@@ -141,10 +153,11 @@ def self.build_from_hash(attributes)
     # @return [Hash] Returns the object in the form of hash
     def to_hash
       hash = {}
-      self.class.attribute_map.each_pair do |attr, param|
+      # include attributes inherited from allOf parents (the nearest declaration wins)
+      self.class.acceptable_attribute_map.each_pair do |attr, param|
         value = self.send(attr)
         if value.nil?
-          is_nullable = self.class.openapi_nullable.include?(attr)
+          is_nullable = self.class.acceptable_openapi_nullable.include?(attr)
           next if !is_nullable || (is_nullable && !instance_variable_defined?(:"@#{attr}"))
         end
 
diff --git a/samples/client/petstore/ruby-faraday/lib/petstore/models/foo.rb b/samples/client/petstore/ruby-faraday/lib/petstore/models/foo.rb
index ceb5b7497955..811726434b54 100644
--- a/samples/client/petstore/ruby-faraday/lib/petstore/models/foo.rb
+++ b/samples/client/petstore/ruby-faraday/lib/petstore/models/foo.rb
@@ -47,6 +47,16 @@ def self.openapi_nullable
       ])
     end
 
+    # Returns attribute type mapping
+    def self.acceptable_openapi_types
+      openapi_types
+    end
+
+    # Returns the nullable attributes
+    def self.acceptable_openapi_nullable
+      openapi_nullable
+    end
+
     # Initializes the object
     # @param [Hash] attributes Model attributes in the form of hash
     def initialize(attributes = {})
@@ -111,18 +121,20 @@ def hash
     def self.build_from_hash(attributes)
       return nil unless attributes.is_a?(Hash)
       attributes = attributes.transform_keys(&:to_sym)
+      # include attributes inherited from allOf parents (the nearest declaration wins)
+      map = acceptable_attribute_map
       transformed_hash = {}
-      openapi_types.each_pair do |key, type|
-        if attributes.key?(attribute_map[key]) && attributes[attribute_map[key]].nil?
+      acceptable_openapi_types.each_pair do |key, type|
+        if attributes.key?(map[key]) && attributes[map[key]].nil?
           transformed_hash["#{key}"] = nil
         elsif type =~ /\AArray<(.*)>/i
           # check to ensure the input is an array given that the attribute
           # is documented as an array but the input is not
-          if attributes[attribute_map[key]].is_a?(Array)
-            transformed_hash["#{key}"] = attributes[attribute_map[key]].map { |v| _deserialize($1, v) }
+          if attributes[map[key]].is_a?(Array)
+            transformed_hash["#{key}"] = attributes[map[key]].map { |v| _deserialize($1, v) }
           end
-        elsif !attributes[attribute_map[key]].nil?
-          transformed_hash["#{key}"] = _deserialize(type, attributes[attribute_map[key]])
+        elsif !attributes[map[key]].nil?
+          transformed_hash["#{key}"] = _deserialize(type, attributes[map[key]])
         end
       end
       new(transformed_hash)
@@ -132,10 +144,11 @@ def self.build_from_hash(attributes)
     # @return [Hash] Returns the object in the form of hash
     def to_hash
       hash = {}
-      self.class.attribute_map.each_pair do |attr, param|
+      # include attributes inherited from allOf parents (the nearest declaration wins)
+      self.class.acceptable_attribute_map.each_pair do |attr, param|
         value = self.send(attr)
         if value.nil?
-          is_nullable = self.class.openapi_nullable.include?(attr)
+          is_nullable = self.class.acceptable_openapi_nullable.include?(attr)
           next if !is_nullable || (is_nullable && !instance_variable_defined?(:"@#{attr}"))
         end
 
diff --git a/samples/client/petstore/ruby-faraday/lib/petstore/models/foo_get_default_response.rb b/samples/client/petstore/ruby-faraday/lib/petstore/models/foo_get_default_response.rb
index 42538a14e2cb..61d044ad8f26 100644
--- a/samples/client/petstore/ruby-faraday/lib/petstore/models/foo_get_default_response.rb
+++ b/samples/client/petstore/ruby-faraday/lib/petstore/models/foo_get_default_response.rb
@@ -47,6 +47,16 @@ def self.openapi_nullable
       ])
     end
 
+    # Returns attribute type mapping
+    def self.acceptable_openapi_types
+      openapi_types
+    end
+
+    # Returns the nullable attributes
+    def self.acceptable_openapi_nullable
+      openapi_nullable
+    end
+
     # Initializes the object
     # @param [Hash] attributes Model attributes in the form of hash
     def initialize(attributes = {})
@@ -109,18 +119,20 @@ def hash
     def self.build_from_hash(attributes)
       return nil unless attributes.is_a?(Hash)
       attributes = attributes.transform_keys(&:to_sym)
+      # include attributes inherited from allOf parents (the nearest declaration wins)
+      map = acceptable_attribute_map
       transformed_hash = {}
-      openapi_types.each_pair do |key, type|
-        if attributes.key?(attribute_map[key]) && attributes[attribute_map[key]].nil?
+      acceptable_openapi_types.each_pair do |key, type|
+        if attributes.key?(map[key]) && attributes[map[key]].nil?
           transformed_hash["#{key}"] = nil
         elsif type =~ /\AArray<(.*)>/i
           # check to ensure the input is an array given that the attribute
           # is documented as an array but the input is not
-          if attributes[attribute_map[key]].is_a?(Array)
-            transformed_hash["#{key}"] = attributes[attribute_map[key]].map { |v| _deserialize($1, v) }
+          if attributes[map[key]].is_a?(Array)
+            transformed_hash["#{key}"] = attributes[map[key]].map { |v| _deserialize($1, v) }
           end
-        elsif !attributes[attribute_map[key]].nil?
-          transformed_hash["#{key}"] = _deserialize(type, attributes[attribute_map[key]])
+        elsif !attributes[map[key]].nil?
+          transformed_hash["#{key}"] = _deserialize(type, attributes[map[key]])
         end
       end
       new(transformed_hash)
@@ -130,10 +142,11 @@ def self.build_from_hash(attributes)
     # @return [Hash] Returns the object in the form of hash
     def to_hash
       hash = {}
-      self.class.attribute_map.each_pair do |attr, param|
+      # include attributes inherited from allOf parents (the nearest declaration wins)
+      self.class.acceptable_attribute_map.each_pair do |attr, param|
         value = self.send(attr)
         if value.nil?
-          is_nullable = self.class.openapi_nullable.include?(attr)
+          is_nullable = self.class.acceptable_openapi_nullable.include?(attr)
           next if !is_nullable || (is_nullable && !instance_variable_defined?(:"@#{attr}"))
         end
 
diff --git a/samples/client/petstore/ruby-faraday/lib/petstore/models/format_test.rb b/samples/client/petstore/ruby-faraday/lib/petstore/models/format_test.rb
index 03a4e130a8f9..6760f6807c59 100644
--- a/samples/client/petstore/ruby-faraday/lib/petstore/models/format_test.rb
+++ b/samples/client/petstore/ruby-faraday/lib/petstore/models/format_test.rb
@@ -109,6 +109,16 @@ def self.openapi_nullable
       ])
     end
 
+    # Returns attribute type mapping
+    def self.acceptable_openapi_types
+      openapi_types
+    end
+
+    # Returns the nullable attributes
+    def self.acceptable_openapi_nullable
+      openapi_nullable
+    end
+
     # Initializes the object
     # @param [Hash] attributes Model attributes in the form of hash
     def initialize(attributes = {})
@@ -525,18 +535,20 @@ def hash
     def self.build_from_hash(attributes)
       return nil unless attributes.is_a?(Hash)
       attributes = attributes.transform_keys(&:to_sym)
+      # include attributes inherited from allOf parents (the nearest declaration wins)
+      map = acceptable_attribute_map
       transformed_hash = {}
-      openapi_types.each_pair do |key, type|
-        if attributes.key?(attribute_map[key]) && attributes[attribute_map[key]].nil?
+      acceptable_openapi_types.each_pair do |key, type|
+        if attributes.key?(map[key]) && attributes[map[key]].nil?
           transformed_hash["#{key}"] = nil
         elsif type =~ /\AArray<(.*)>/i
           # check to ensure the input is an array given that the attribute
           # is documented as an array but the input is not
-          if attributes[attribute_map[key]].is_a?(Array)
-            transformed_hash["#{key}"] = attributes[attribute_map[key]].map { |v| _deserialize($1, v) }
+          if attributes[map[key]].is_a?(Array)
+            transformed_hash["#{key}"] = attributes[map[key]].map { |v| _deserialize($1, v) }
           end
-        elsif !attributes[attribute_map[key]].nil?
-          transformed_hash["#{key}"] = _deserialize(type, attributes[attribute_map[key]])
+        elsif !attributes[map[key]].nil?
+          transformed_hash["#{key}"] = _deserialize(type, attributes[map[key]])
         end
       end
       new(transformed_hash)
@@ -546,10 +558,11 @@ def self.build_from_hash(attributes)
     # @return [Hash] Returns the object in the form of hash
     def to_hash
       hash = {}
-      self.class.attribute_map.each_pair do |attr, param|
+      # include attributes inherited from allOf parents (the nearest declaration wins)
+      self.class.acceptable_attribute_map.each_pair do |attr, param|
         value = self.send(attr)
         if value.nil?
-          is_nullable = self.class.openapi_nullable.include?(attr)
+          is_nullable = self.class.acceptable_openapi_nullable.include?(attr)
           next if !is_nullable || (is_nullable && !instance_variable_defined?(:"@#{attr}"))
         end
 
diff --git a/samples/client/petstore/ruby-faraday/lib/petstore/models/has_only_read_only.rb b/samples/client/petstore/ruby-faraday/lib/petstore/models/has_only_read_only.rb
index cc584c09e54f..604a3da147bd 100644
--- a/samples/client/petstore/ruby-faraday/lib/petstore/models/has_only_read_only.rb
+++ b/samples/client/petstore/ruby-faraday/lib/petstore/models/has_only_read_only.rb
@@ -51,6 +51,16 @@ def self.openapi_nullable
       ])
     end
 
+    # Returns attribute type mapping
+    def self.acceptable_openapi_types
+      openapi_types
+    end
+
+    # Returns the nullable attributes
+    def self.acceptable_openapi_nullable
+      openapi_nullable
+    end
+
     # Initializes the object
     # @param [Hash] attributes Model attributes in the form of hash
     def initialize(attributes = {})
@@ -118,18 +128,20 @@ def hash
     def self.build_from_hash(attributes)
       return nil unless attributes.is_a?(Hash)
       attributes = attributes.transform_keys(&:to_sym)
+      # include attributes inherited from allOf parents (the nearest declaration wins)
+      map = acceptable_attribute_map
       transformed_hash = {}
-      openapi_types.each_pair do |key, type|
-        if attributes.key?(attribute_map[key]) && attributes[attribute_map[key]].nil?
+      acceptable_openapi_types.each_pair do |key, type|
+        if attributes.key?(map[key]) && attributes[map[key]].nil?
           transformed_hash["#{key}"] = nil
         elsif type =~ /\AArray<(.*)>/i
           # check to ensure the input is an array given that the attribute
           # is documented as an array but the input is not
-          if attributes[attribute_map[key]].is_a?(Array)
-            transformed_hash["#{key}"] = attributes[attribute_map[key]].map { |v| _deserialize($1, v) }
+          if attributes[map[key]].is_a?(Array)
+            transformed_hash["#{key}"] = attributes[map[key]].map { |v| _deserialize($1, v) }
           end
-        elsif !attributes[attribute_map[key]].nil?
-          transformed_hash["#{key}"] = _deserialize(type, attributes[attribute_map[key]])
+        elsif !attributes[map[key]].nil?
+          transformed_hash["#{key}"] = _deserialize(type, attributes[map[key]])
         end
       end
       new(transformed_hash)
@@ -139,10 +151,11 @@ def self.build_from_hash(attributes)
     # @return [Hash] Returns the object in the form of hash
     def to_hash
       hash = {}
-      self.class.attribute_map.each_pair do |attr, param|
+      # include attributes inherited from allOf parents (the nearest declaration wins)
+      self.class.acceptable_attribute_map.each_pair do |attr, param|
         value = self.send(attr)
         if value.nil?
-          is_nullable = self.class.openapi_nullable.include?(attr)
+          is_nullable = self.class.acceptable_openapi_nullable.include?(attr)
           next if !is_nullable || (is_nullable && !instance_variable_defined?(:"@#{attr}"))
         end
 
diff --git a/samples/client/petstore/ruby-faraday/lib/petstore/models/health_check_result.rb b/samples/client/petstore/ruby-faraday/lib/petstore/models/health_check_result.rb
index a66e1b71331d..0792044db072 100644
--- a/samples/client/petstore/ruby-faraday/lib/petstore/models/health_check_result.rb
+++ b/samples/client/petstore/ruby-faraday/lib/petstore/models/health_check_result.rb
@@ -49,6 +49,16 @@ def self.openapi_nullable
       ])
     end
 
+    # Returns attribute type mapping
+    def self.acceptable_openapi_types
+      openapi_types
+    end
+
+    # Returns the nullable attributes
+    def self.acceptable_openapi_nullable
+      openapi_nullable
+    end
+
     # Initializes the object
     # @param [Hash] attributes Model attributes in the form of hash
     def initialize(attributes = {})
@@ -111,18 +121,20 @@ def hash
     def self.build_from_hash(attributes)
       return nil unless attributes.is_a?(Hash)
       attributes = attributes.transform_keys(&:to_sym)
+      # include attributes inherited from allOf parents (the nearest declaration wins)
+      map = acceptable_attribute_map
       transformed_hash = {}
-      openapi_types.each_pair do |key, type|
-        if attributes.key?(attribute_map[key]) && attributes[attribute_map[key]].nil?
+      acceptable_openapi_types.each_pair do |key, type|
+        if attributes.key?(map[key]) && attributes[map[key]].nil?
           transformed_hash["#{key}"] = nil
         elsif type =~ /\AArray<(.*)>/i
           # check to ensure the input is an array given that the attribute
           # is documented as an array but the input is not
-          if attributes[attribute_map[key]].is_a?(Array)
-            transformed_hash["#{key}"] = attributes[attribute_map[key]].map { |v| _deserialize($1, v) }
+          if attributes[map[key]].is_a?(Array)
+            transformed_hash["#{key}"] = attributes[map[key]].map { |v| _deserialize($1, v) }
           end
-        elsif !attributes[attribute_map[key]].nil?
-          transformed_hash["#{key}"] = _deserialize(type, attributes[attribute_map[key]])
+        elsif !attributes[map[key]].nil?
+          transformed_hash["#{key}"] = _deserialize(type, attributes[map[key]])
         end
       end
       new(transformed_hash)
@@ -132,10 +144,11 @@ def self.build_from_hash(attributes)
     # @return [Hash] Returns the object in the form of hash
     def to_hash
       hash = {}
-      self.class.attribute_map.each_pair do |attr, param|
+      # include attributes inherited from allOf parents (the nearest declaration wins)
+      self.class.acceptable_attribute_map.each_pair do |attr, param|
         value = self.send(attr)
         if value.nil?
-          is_nullable = self.class.openapi_nullable.include?(attr)
+          is_nullable = self.class.acceptable_openapi_nullable.include?(attr)
           next if !is_nullable || (is_nullable && !instance_variable_defined?(:"@#{attr}"))
         end
 
diff --git a/samples/client/petstore/ruby-faraday/lib/petstore/models/list.rb b/samples/client/petstore/ruby-faraday/lib/petstore/models/list.rb
index 2dc658065278..ecc8eb8aafc5 100644
--- a/samples/client/petstore/ruby-faraday/lib/petstore/models/list.rb
+++ b/samples/client/petstore/ruby-faraday/lib/petstore/models/list.rb
@@ -47,6 +47,16 @@ def self.openapi_nullable
       ])
     end
 
+    # Returns attribute type mapping
+    def self.acceptable_openapi_types
+      openapi_types
+    end
+
+    # Returns the nullable attributes
+    def self.acceptable_openapi_nullable
+      openapi_nullable
+    end
+
     # Initializes the object
     # @param [Hash] attributes Model attributes in the form of hash
     def initialize(attributes = {})
@@ -109,18 +119,20 @@ def hash
     def self.build_from_hash(attributes)
       return nil unless attributes.is_a?(Hash)
       attributes = attributes.transform_keys(&:to_sym)
+      # include attributes inherited from allOf parents (the nearest declaration wins)
+      map = acceptable_attribute_map
       transformed_hash = {}
-      openapi_types.each_pair do |key, type|
-        if attributes.key?(attribute_map[key]) && attributes[attribute_map[key]].nil?
+      acceptable_openapi_types.each_pair do |key, type|
+        if attributes.key?(map[key]) && attributes[map[key]].nil?
           transformed_hash["#{key}"] = nil
         elsif type =~ /\AArray<(.*)>/i
           # check to ensure the input is an array given that the attribute
           # is documented as an array but the input is not
-          if attributes[attribute_map[key]].is_a?(Array)
-            transformed_hash["#{key}"] = attributes[attribute_map[key]].map { |v| _deserialize($1, v) }
+          if attributes[map[key]].is_a?(Array)
+            transformed_hash["#{key}"] = attributes[map[key]].map { |v| _deserialize($1, v) }
           end
-        elsif !attributes[attribute_map[key]].nil?
-          transformed_hash["#{key}"] = _deserialize(type, attributes[attribute_map[key]])
+        elsif !attributes[map[key]].nil?
+          transformed_hash["#{key}"] = _deserialize(type, attributes[map[key]])
         end
       end
       new(transformed_hash)
@@ -130,10 +142,11 @@ def self.build_from_hash(attributes)
     # @return [Hash] Returns the object in the form of hash
     def to_hash
       hash = {}
-      self.class.attribute_map.each_pair do |attr, param|
+      # include attributes inherited from allOf parents (the nearest declaration wins)
+      self.class.acceptable_attribute_map.each_pair do |attr, param|
         value = self.send(attr)
         if value.nil?
-          is_nullable = self.class.openapi_nullable.include?(attr)
+          is_nullable = self.class.acceptable_openapi_nullable.include?(attr)
           next if !is_nullable || (is_nullable && !instance_variable_defined?(:"@#{attr}"))
         end
 
diff --git a/samples/client/petstore/ruby-faraday/lib/petstore/models/map_test.rb b/samples/client/petstore/ruby-faraday/lib/petstore/models/map_test.rb
index 78c5472f24ae..eca01649a52a 100644
--- a/samples/client/petstore/ruby-faraday/lib/petstore/models/map_test.rb
+++ b/samples/client/petstore/ruby-faraday/lib/petstore/models/map_test.rb
@@ -81,6 +81,16 @@ def self.openapi_nullable
       ])
     end
 
+    # Returns attribute type mapping
+    def self.acceptable_openapi_types
+      openapi_types
+    end
+
+    # Returns the nullable attributes
+    def self.acceptable_openapi_nullable
+      openapi_nullable
+    end
+
     # Initializes the object
     # @param [Hash] attributes Model attributes in the form of hash
     def initialize(attributes = {})
@@ -166,18 +176,20 @@ def hash
     def self.build_from_hash(attributes)
       return nil unless attributes.is_a?(Hash)
       attributes = attributes.transform_keys(&:to_sym)
+      # include attributes inherited from allOf parents (the nearest declaration wins)
+      map = acceptable_attribute_map
       transformed_hash = {}
-      openapi_types.each_pair do |key, type|
-        if attributes.key?(attribute_map[key]) && attributes[attribute_map[key]].nil?
+      acceptable_openapi_types.each_pair do |key, type|
+        if attributes.key?(map[key]) && attributes[map[key]].nil?
           transformed_hash["#{key}"] = nil
         elsif type =~ /\AArray<(.*)>/i
           # check to ensure the input is an array given that the attribute
           # is documented as an array but the input is not
-          if attributes[attribute_map[key]].is_a?(Array)
-            transformed_hash["#{key}"] = attributes[attribute_map[key]].map { |v| _deserialize($1, v) }
+          if attributes[map[key]].is_a?(Array)
+            transformed_hash["#{key}"] = attributes[map[key]].map { |v| _deserialize($1, v) }
           end
-        elsif !attributes[attribute_map[key]].nil?
-          transformed_hash["#{key}"] = _deserialize(type, attributes[attribute_map[key]])
+        elsif !attributes[map[key]].nil?
+          transformed_hash["#{key}"] = _deserialize(type, attributes[map[key]])
         end
       end
       new(transformed_hash)
@@ -187,10 +199,11 @@ def self.build_from_hash(attributes)
     # @return [Hash] Returns the object in the form of hash
     def to_hash
       hash = {}
-      self.class.attribute_map.each_pair do |attr, param|
+      # include attributes inherited from allOf parents (the nearest declaration wins)
+      self.class.acceptable_attribute_map.each_pair do |attr, param|
         value = self.send(attr)
         if value.nil?
-          is_nullable = self.class.openapi_nullable.include?(attr)
+          is_nullable = self.class.acceptable_openapi_nullable.include?(attr)
           next if !is_nullable || (is_nullable && !instance_variable_defined?(:"@#{attr}"))
         end
 
diff --git a/samples/client/petstore/ruby-faraday/lib/petstore/models/mixed_properties_and_additional_properties_class.rb b/samples/client/petstore/ruby-faraday/lib/petstore/models/mixed_properties_and_additional_properties_class.rb
index bf1d3768951b..060c8488652f 100644
--- a/samples/client/petstore/ruby-faraday/lib/petstore/models/mixed_properties_and_additional_properties_class.rb
+++ b/samples/client/petstore/ruby-faraday/lib/petstore/models/mixed_properties_and_additional_properties_class.rb
@@ -55,6 +55,16 @@ def self.openapi_nullable
       ])
     end
 
+    # Returns attribute type mapping
+    def self.acceptable_openapi_types
+      openapi_types
+    end
+
+    # Returns the nullable attributes
+    def self.acceptable_openapi_nullable
+      openapi_nullable
+    end
+
     # Initializes the object
     # @param [Hash] attributes Model attributes in the form of hash
     def initialize(attributes = {})
@@ -129,18 +139,20 @@ def hash
     def self.build_from_hash(attributes)
       return nil unless attributes.is_a?(Hash)
       attributes = attributes.transform_keys(&:to_sym)
+      # include attributes inherited from allOf parents (the nearest declaration wins)
+      map = acceptable_attribute_map
       transformed_hash = {}
-      openapi_types.each_pair do |key, type|
-        if attributes.key?(attribute_map[key]) && attributes[attribute_map[key]].nil?
+      acceptable_openapi_types.each_pair do |key, type|
+        if attributes.key?(map[key]) && attributes[map[key]].nil?
           transformed_hash["#{key}"] = nil
         elsif type =~ /\AArray<(.*)>/i
           # check to ensure the input is an array given that the attribute
           # is documented as an array but the input is not
-          if attributes[attribute_map[key]].is_a?(Array)
-            transformed_hash["#{key}"] = attributes[attribute_map[key]].map { |v| _deserialize($1, v) }
+          if attributes[map[key]].is_a?(Array)
+            transformed_hash["#{key}"] = attributes[map[key]].map { |v| _deserialize($1, v) }
           end
-        elsif !attributes[attribute_map[key]].nil?
-          transformed_hash["#{key}"] = _deserialize(type, attributes[attribute_map[key]])
+        elsif !attributes[map[key]].nil?
+          transformed_hash["#{key}"] = _deserialize(type, attributes[map[key]])
         end
       end
       new(transformed_hash)
@@ -150,10 +162,11 @@ def self.build_from_hash(attributes)
     # @return [Hash] Returns the object in the form of hash
     def to_hash
       hash = {}
-      self.class.attribute_map.each_pair do |attr, param|
+      # include attributes inherited from allOf parents (the nearest declaration wins)
+      self.class.acceptable_attribute_map.each_pair do |attr, param|
         value = self.send(attr)
         if value.nil?
-          is_nullable = self.class.openapi_nullable.include?(attr)
+          is_nullable = self.class.acceptable_openapi_nullable.include?(attr)
           next if !is_nullable || (is_nullable && !instance_variable_defined?(:"@#{attr}"))
         end
 
diff --git a/samples/client/petstore/ruby-faraday/lib/petstore/models/model200_response.rb b/samples/client/petstore/ruby-faraday/lib/petstore/models/model200_response.rb
index 9cff83ced2c9..2ea5253eb3d4 100644
--- a/samples/client/petstore/ruby-faraday/lib/petstore/models/model200_response.rb
+++ b/samples/client/petstore/ruby-faraday/lib/petstore/models/model200_response.rb
@@ -52,6 +52,16 @@ def self.openapi_nullable
       ])
     end
 
+    # Returns attribute type mapping
+    def self.acceptable_openapi_types
+      openapi_types
+    end
+
+    # Returns the nullable attributes
+    def self.acceptable_openapi_nullable
+      openapi_nullable
+    end
+
     # Initializes the object
     # @param [Hash] attributes Model attributes in the form of hash
     def initialize(attributes = {})
@@ -119,18 +129,20 @@ def hash
     def self.build_from_hash(attributes)
       return nil unless attributes.is_a?(Hash)
       attributes = attributes.transform_keys(&:to_sym)
+      # include attributes inherited from allOf parents (the nearest declaration wins)
+      map = acceptable_attribute_map
       transformed_hash = {}
-      openapi_types.each_pair do |key, type|
-        if attributes.key?(attribute_map[key]) && attributes[attribute_map[key]].nil?
+      acceptable_openapi_types.each_pair do |key, type|
+        if attributes.key?(map[key]) && attributes[map[key]].nil?
           transformed_hash["#{key}"] = nil
         elsif type =~ /\AArray<(.*)>/i
           # check to ensure the input is an array given that the attribute
           # is documented as an array but the input is not
-          if attributes[attribute_map[key]].is_a?(Array)
-            transformed_hash["#{key}"] = attributes[attribute_map[key]].map { |v| _deserialize($1, v) }
+          if attributes[map[key]].is_a?(Array)
+            transformed_hash["#{key}"] = attributes[map[key]].map { |v| _deserialize($1, v) }
           end
-        elsif !attributes[attribute_map[key]].nil?
-          transformed_hash["#{key}"] = _deserialize(type, attributes[attribute_map[key]])
+        elsif !attributes[map[key]].nil?
+          transformed_hash["#{key}"] = _deserialize(type, attributes[map[key]])
         end
       end
       new(transformed_hash)
@@ -140,10 +152,11 @@ def self.build_from_hash(attributes)
     # @return [Hash] Returns the object in the form of hash
     def to_hash
       hash = {}
-      self.class.attribute_map.each_pair do |attr, param|
+      # include attributes inherited from allOf parents (the nearest declaration wins)
+      self.class.acceptable_attribute_map.each_pair do |attr, param|
         value = self.send(attr)
         if value.nil?
-          is_nullable = self.class.openapi_nullable.include?(attr)
+          is_nullable = self.class.acceptable_openapi_nullable.include?(attr)
           next if !is_nullable || (is_nullable && !instance_variable_defined?(:"@#{attr}"))
         end
 
diff --git a/samples/client/petstore/ruby-faraday/lib/petstore/models/model_return.rb b/samples/client/petstore/ruby-faraday/lib/petstore/models/model_return.rb
index d520a45c2040..c2b6ac11c2e9 100644
--- a/samples/client/petstore/ruby-faraday/lib/petstore/models/model_return.rb
+++ b/samples/client/petstore/ruby-faraday/lib/petstore/models/model_return.rb
@@ -48,6 +48,16 @@ def self.openapi_nullable
       ])
     end
 
+    # Returns attribute type mapping
+    def self.acceptable_openapi_types
+      openapi_types
+    end
+
+    # Returns the nullable attributes
+    def self.acceptable_openapi_nullable
+      openapi_nullable
+    end
+
     # Initializes the object
     # @param [Hash] attributes Model attributes in the form of hash
     def initialize(attributes = {})
@@ -110,18 +120,20 @@ def hash
     def self.build_from_hash(attributes)
       return nil unless attributes.is_a?(Hash)
       attributes = attributes.transform_keys(&:to_sym)
+      # include attributes inherited from allOf parents (the nearest declaration wins)
+      map = acceptable_attribute_map
       transformed_hash = {}
-      openapi_types.each_pair do |key, type|
-        if attributes.key?(attribute_map[key]) && attributes[attribute_map[key]].nil?
+      acceptable_openapi_types.each_pair do |key, type|
+        if attributes.key?(map[key]) && attributes[map[key]].nil?
           transformed_hash["#{key}"] = nil
         elsif type =~ /\AArray<(.*)>/i
           # check to ensure the input is an array given that the attribute
           # is documented as an array but the input is not
-          if attributes[attribute_map[key]].is_a?(Array)
-            transformed_hash["#{key}"] = attributes[attribute_map[key]].map { |v| _deserialize($1, v) }
+          if attributes[map[key]].is_a?(Array)
+            transformed_hash["#{key}"] = attributes[map[key]].map { |v| _deserialize($1, v) }
           end
-        elsif !attributes[attribute_map[key]].nil?
-          transformed_hash["#{key}"] = _deserialize(type, attributes[attribute_map[key]])
+        elsif !attributes[map[key]].nil?
+          transformed_hash["#{key}"] = _deserialize(type, attributes[map[key]])
         end
       end
       new(transformed_hash)
@@ -131,10 +143,11 @@ def self.build_from_hash(attributes)
     # @return [Hash] Returns the object in the form of hash
     def to_hash
       hash = {}
-      self.class.attribute_map.each_pair do |attr, param|
+      # include attributes inherited from allOf parents (the nearest declaration wins)
+      self.class.acceptable_attribute_map.each_pair do |attr, param|
         value = self.send(attr)
         if value.nil?
-          is_nullable = self.class.openapi_nullable.include?(attr)
+          is_nullable = self.class.acceptable_openapi_nullable.include?(attr)
           next if !is_nullable || (is_nullable && !instance_variable_defined?(:"@#{attr}"))
         end
 
diff --git a/samples/client/petstore/ruby-faraday/lib/petstore/models/name.rb b/samples/client/petstore/ruby-faraday/lib/petstore/models/name.rb
index 45b01b5746d3..c989368e6597 100644
--- a/samples/client/petstore/ruby-faraday/lib/petstore/models/name.rb
+++ b/samples/client/petstore/ruby-faraday/lib/petstore/models/name.rb
@@ -60,6 +60,16 @@ def self.openapi_nullable
       ])
     end
 
+    # Returns attribute type mapping
+    def self.acceptable_openapi_types
+      openapi_types
+    end
+
+    # Returns the nullable attributes
+    def self.acceptable_openapi_nullable
+      openapi_nullable
+    end
+
     # Initializes the object
     # @param [Hash] attributes Model attributes in the form of hash
     def initialize(attributes = {})
@@ -154,18 +164,20 @@ def hash
     def self.build_from_hash(attributes)
       return nil unless attributes.is_a?(Hash)
       attributes = attributes.transform_keys(&:to_sym)
+      # include attributes inherited from allOf parents (the nearest declaration wins)
+      map = acceptable_attribute_map
       transformed_hash = {}
-      openapi_types.each_pair do |key, type|
-        if attributes.key?(attribute_map[key]) && attributes[attribute_map[key]].nil?
+      acceptable_openapi_types.each_pair do |key, type|
+        if attributes.key?(map[key]) && attributes[map[key]].nil?
           transformed_hash["#{key}"] = nil
         elsif type =~ /\AArray<(.*)>/i
           # check to ensure the input is an array given that the attribute
           # is documented as an array but the input is not
-          if attributes[attribute_map[key]].is_a?(Array)
-            transformed_hash["#{key}"] = attributes[attribute_map[key]].map { |v| _deserialize($1, v) }
+          if attributes[map[key]].is_a?(Array)
+            transformed_hash["#{key}"] = attributes[map[key]].map { |v| _deserialize($1, v) }
           end
-        elsif !attributes[attribute_map[key]].nil?
-          transformed_hash["#{key}"] = _deserialize(type, attributes[attribute_map[key]])
+        elsif !attributes[map[key]].nil?
+          transformed_hash["#{key}"] = _deserialize(type, attributes[map[key]])
         end
       end
       new(transformed_hash)
@@ -175,10 +187,11 @@ def self.build_from_hash(attributes)
     # @return [Hash] Returns the object in the form of hash
     def to_hash
       hash = {}
-      self.class.attribute_map.each_pair do |attr, param|
+      # include attributes inherited from allOf parents (the nearest declaration wins)
+      self.class.acceptable_attribute_map.each_pair do |attr, param|
         value = self.send(attr)
         if value.nil?
-          is_nullable = self.class.openapi_nullable.include?(attr)
+          is_nullable = self.class.acceptable_openapi_nullable.include?(attr)
           next if !is_nullable || (is_nullable && !instance_variable_defined?(:"@#{attr}"))
         end
 
diff --git a/samples/client/petstore/ruby-faraday/lib/petstore/models/nullable_class.rb b/samples/client/petstore/ruby-faraday/lib/petstore/models/nullable_class.rb
index f81fb17f118a..de5510060a65 100644
--- a/samples/client/petstore/ruby-faraday/lib/petstore/models/nullable_class.rb
+++ b/samples/client/petstore/ruby-faraday/lib/petstore/models/nullable_class.rb
@@ -101,6 +101,16 @@ def self.openapi_nullable
       ])
     end
 
+    # Returns attribute type mapping
+    def self.acceptable_openapi_types
+      openapi_types
+    end
+
+    # Returns the nullable attributes
+    def self.acceptable_openapi_nullable
+      openapi_nullable
+    end
+
     # Initializes the object
     # @param [Hash] attributes Model attributes in the form of hash
     def initialize(attributes = {})
@@ -230,18 +240,20 @@ def hash
     def self.build_from_hash(attributes)
       return nil unless attributes.is_a?(Hash)
       attributes = attributes.transform_keys(&:to_sym)
+      # include attributes inherited from allOf parents (the nearest declaration wins)
+      map = acceptable_attribute_map
       transformed_hash = {}
-      openapi_types.each_pair do |key, type|
-        if attributes.key?(attribute_map[key]) && attributes[attribute_map[key]].nil?
+      acceptable_openapi_types.each_pair do |key, type|
+        if attributes.key?(map[key]) && attributes[map[key]].nil?
           transformed_hash["#{key}"] = nil
         elsif type =~ /\AArray<(.*)>/i
           # check to ensure the input is an array given that the attribute
           # is documented as an array but the input is not
-          if attributes[attribute_map[key]].is_a?(Array)
-            transformed_hash["#{key}"] = attributes[attribute_map[key]].map { |v| _deserialize($1, v) }
+          if attributes[map[key]].is_a?(Array)
+            transformed_hash["#{key}"] = attributes[map[key]].map { |v| _deserialize($1, v) }
           end
-        elsif !attributes[attribute_map[key]].nil?
-          transformed_hash["#{key}"] = _deserialize(type, attributes[attribute_map[key]])
+        elsif !attributes[map[key]].nil?
+          transformed_hash["#{key}"] = _deserialize(type, attributes[map[key]])
         end
       end
       new(transformed_hash)
@@ -251,10 +263,11 @@ def self.build_from_hash(attributes)
     # @return [Hash] Returns the object in the form of hash
     def to_hash
       hash = {}
-      self.class.attribute_map.each_pair do |attr, param|
+      # include attributes inherited from allOf parents (the nearest declaration wins)
+      self.class.acceptable_attribute_map.each_pair do |attr, param|
         value = self.send(attr)
         if value.nil?
-          is_nullable = self.class.openapi_nullable.include?(attr)
+          is_nullable = self.class.acceptable_openapi_nullable.include?(attr)
           next if !is_nullable || (is_nullable && !instance_variable_defined?(:"@#{attr}"))
         end
 
diff --git a/samples/client/petstore/ruby-faraday/lib/petstore/models/number_only.rb b/samples/client/petstore/ruby-faraday/lib/petstore/models/number_only.rb
index 9bf457dfd188..b4fb53e2c3d3 100644
--- a/samples/client/petstore/ruby-faraday/lib/petstore/models/number_only.rb
+++ b/samples/client/petstore/ruby-faraday/lib/petstore/models/number_only.rb
@@ -47,6 +47,16 @@ def self.openapi_nullable
       ])
     end
 
+    # Returns attribute type mapping
+    def self.acceptable_openapi_types
+      openapi_types
+    end
+
+    # Returns the nullable attributes
+    def self.acceptable_openapi_nullable
+      openapi_nullable
+    end
+
     # Initializes the object
     # @param [Hash] attributes Model attributes in the form of hash
     def initialize(attributes = {})
@@ -109,18 +119,20 @@ def hash
     def self.build_from_hash(attributes)
       return nil unless attributes.is_a?(Hash)
       attributes = attributes.transform_keys(&:to_sym)
+      # include attributes inherited from allOf parents (the nearest declaration wins)
+      map = acceptable_attribute_map
       transformed_hash = {}
-      openapi_types.each_pair do |key, type|
-        if attributes.key?(attribute_map[key]) && attributes[attribute_map[key]].nil?
+      acceptable_openapi_types.each_pair do |key, type|
+        if attributes.key?(map[key]) && attributes[map[key]].nil?
           transformed_hash["#{key}"] = nil
         elsif type =~ /\AArray<(.*)>/i
           # check to ensure the input is an array given that the attribute
           # is documented as an array but the input is not
-          if attributes[attribute_map[key]].is_a?(Array)
-            transformed_hash["#{key}"] = attributes[attribute_map[key]].map { |v| _deserialize($1, v) }
+          if attributes[map[key]].is_a?(Array)
+            transformed_hash["#{key}"] = attributes[map[key]].map { |v| _deserialize($1, v) }
           end
-        elsif !attributes[attribute_map[key]].nil?
-          transformed_hash["#{key}"] = _deserialize(type, attributes[attribute_map[key]])
+        elsif !attributes[map[key]].nil?
+          transformed_hash["#{key}"] = _deserialize(type, attributes[map[key]])
         end
       end
       new(transformed_hash)
@@ -130,10 +142,11 @@ def self.build_from_hash(attributes)
     # @return [Hash] Returns the object in the form of hash
     def to_hash
       hash = {}
-      self.class.attribute_map.each_pair do |attr, param|
+      # include attributes inherited from allOf parents (the nearest declaration wins)
+      self.class.acceptable_attribute_map.each_pair do |attr, param|
         value = self.send(attr)
         if value.nil?
-          is_nullable = self.class.openapi_nullable.include?(attr)
+          is_nullable = self.class.acceptable_openapi_nullable.include?(attr)
           next if !is_nullable || (is_nullable && !instance_variable_defined?(:"@#{attr}"))
         end
 
diff --git a/samples/client/petstore/ruby-faraday/lib/petstore/models/object_with_deprecated_fields.rb b/samples/client/petstore/ruby-faraday/lib/petstore/models/object_with_deprecated_fields.rb
index dceda346bd70..3819fef7a58b 100644
--- a/samples/client/petstore/ruby-faraday/lib/petstore/models/object_with_deprecated_fields.rb
+++ b/samples/client/petstore/ruby-faraday/lib/petstore/models/object_with_deprecated_fields.rb
@@ -59,6 +59,16 @@ def self.openapi_nullable
       ])
     end
 
+    # Returns attribute type mapping
+    def self.acceptable_openapi_types
+      openapi_types
+    end
+
+    # Returns the nullable attributes
+    def self.acceptable_openapi_nullable
+      openapi_nullable
+    end
+
     # Initializes the object
     # @param [Hash] attributes Model attributes in the form of hash
     def initialize(attributes = {})
@@ -138,18 +148,20 @@ def hash
     def self.build_from_hash(attributes)
       return nil unless attributes.is_a?(Hash)
       attributes = attributes.transform_keys(&:to_sym)
+      # include attributes inherited from allOf parents (the nearest declaration wins)
+      map = acceptable_attribute_map
       transformed_hash = {}
-      openapi_types.each_pair do |key, type|
-        if attributes.key?(attribute_map[key]) && attributes[attribute_map[key]].nil?
+      acceptable_openapi_types.each_pair do |key, type|
+        if attributes.key?(map[key]) && attributes[map[key]].nil?
           transformed_hash["#{key}"] = nil
         elsif type =~ /\AArray<(.*)>/i
           # check to ensure the input is an array given that the attribute
           # is documented as an array but the input is not
-          if attributes[attribute_map[key]].is_a?(Array)
-            transformed_hash["#{key}"] = attributes[attribute_map[key]].map { |v| _deserialize($1, v) }
+          if attributes[map[key]].is_a?(Array)
+            transformed_hash["#{key}"] = attributes[map[key]].map { |v| _deserialize($1, v) }
           end
-        elsif !attributes[attribute_map[key]].nil?
-          transformed_hash["#{key}"] = _deserialize(type, attributes[attribute_map[key]])
+        elsif !attributes[map[key]].nil?
+          transformed_hash["#{key}"] = _deserialize(type, attributes[map[key]])
         end
       end
       new(transformed_hash)
@@ -159,10 +171,11 @@ def self.build_from_hash(attributes)
     # @return [Hash] Returns the object in the form of hash
     def to_hash
       hash = {}
-      self.class.attribute_map.each_pair do |attr, param|
+      # include attributes inherited from allOf parents (the nearest declaration wins)
+      self.class.acceptable_attribute_map.each_pair do |attr, param|
         value = self.send(attr)
         if value.nil?
-          is_nullable = self.class.openapi_nullable.include?(attr)
+          is_nullable = self.class.acceptable_openapi_nullable.include?(attr)
           next if !is_nullable || (is_nullable && !instance_variable_defined?(:"@#{attr}"))
         end
 
diff --git a/samples/client/petstore/ruby-faraday/lib/petstore/models/order.rb b/samples/client/petstore/ruby-faraday/lib/petstore/models/order.rb
index f7e7b4eb9117..8cebfcefa34e 100644
--- a/samples/client/petstore/ruby-faraday/lib/petstore/models/order.rb
+++ b/samples/client/petstore/ruby-faraday/lib/petstore/models/order.rb
@@ -90,6 +90,16 @@ def self.openapi_nullable
       ])
     end
 
+    # Returns attribute type mapping
+    def self.acceptable_openapi_types
+      openapi_types
+    end
+
+    # Returns the nullable attributes
+    def self.acceptable_openapi_nullable
+      openapi_nullable
+    end
+
     # Initializes the object
     # @param [Hash] attributes Model attributes in the form of hash
     def initialize(attributes = {})
@@ -191,18 +201,20 @@ def hash
     def self.build_from_hash(attributes)
       return nil unless attributes.is_a?(Hash)
       attributes = attributes.transform_keys(&:to_sym)
+      # include attributes inherited from allOf parents (the nearest declaration wins)
+      map = acceptable_attribute_map
       transformed_hash = {}
-      openapi_types.each_pair do |key, type|
-        if attributes.key?(attribute_map[key]) && attributes[attribute_map[key]].nil?
+      acceptable_openapi_types.each_pair do |key, type|
+        if attributes.key?(map[key]) && attributes[map[key]].nil?
           transformed_hash["#{key}"] = nil
         elsif type =~ /\AArray<(.*)>/i
           # check to ensure the input is an array given that the attribute
           # is documented as an array but the input is not
-          if attributes[attribute_map[key]].is_a?(Array)
-            transformed_hash["#{key}"] = attributes[attribute_map[key]].map { |v| _deserialize($1, v) }
+          if attributes[map[key]].is_a?(Array)
+            transformed_hash["#{key}"] = attributes[map[key]].map { |v| _deserialize($1, v) }
           end
-        elsif !attributes[attribute_map[key]].nil?
-          transformed_hash["#{key}"] = _deserialize(type, attributes[attribute_map[key]])
+        elsif !attributes[map[key]].nil?
+          transformed_hash["#{key}"] = _deserialize(type, attributes[map[key]])
         end
       end
       new(transformed_hash)
@@ -212,10 +224,11 @@ def self.build_from_hash(attributes)
     # @return [Hash] Returns the object in the form of hash
     def to_hash
       hash = {}
-      self.class.attribute_map.each_pair do |attr, param|
+      # include attributes inherited from allOf parents (the nearest declaration wins)
+      self.class.acceptable_attribute_map.each_pair do |attr, param|
         value = self.send(attr)
         if value.nil?
-          is_nullable = self.class.openapi_nullable.include?(attr)
+          is_nullable = self.class.acceptable_openapi_nullable.include?(attr)
           next if !is_nullable || (is_nullable && !instance_variable_defined?(:"@#{attr}"))
         end
 
diff --git a/samples/client/petstore/ruby-faraday/lib/petstore/models/outer_composite.rb b/samples/client/petstore/ruby-faraday/lib/petstore/models/outer_composite.rb
index 2245e8512600..afa9203ebde9 100644
--- a/samples/client/petstore/ruby-faraday/lib/petstore/models/outer_composite.rb
+++ b/samples/client/petstore/ruby-faraday/lib/petstore/models/outer_composite.rb
@@ -55,6 +55,16 @@ def self.openapi_nullable
       ])
     end
 
+    # Returns attribute type mapping
+    def self.acceptable_openapi_types
+      openapi_types
+    end
+
+    # Returns the nullable attributes
+    def self.acceptable_openapi_nullable
+      openapi_nullable
+    end
+
     # Initializes the object
     # @param [Hash] attributes Model attributes in the form of hash
     def initialize(attributes = {})
@@ -127,18 +137,20 @@ def hash
     def self.build_from_hash(attributes)
       return nil unless attributes.is_a?(Hash)
       attributes = attributes.transform_keys(&:to_sym)
+      # include attributes inherited from allOf parents (the nearest declaration wins)
+      map = acceptable_attribute_map
       transformed_hash = {}
-      openapi_types.each_pair do |key, type|
-        if attributes.key?(attribute_map[key]) && attributes[attribute_map[key]].nil?
+      acceptable_openapi_types.each_pair do |key, type|
+        if attributes.key?(map[key]) && attributes[map[key]].nil?
           transformed_hash["#{key}"] = nil
         elsif type =~ /\AArray<(.*)>/i
           # check to ensure the input is an array given that the attribute
           # is documented as an array but the input is not
-          if attributes[attribute_map[key]].is_a?(Array)
-            transformed_hash["#{key}"] = attributes[attribute_map[key]].map { |v| _deserialize($1, v) }
+          if attributes[map[key]].is_a?(Array)
+            transformed_hash["#{key}"] = attributes[map[key]].map { |v| _deserialize($1, v) }
           end
-        elsif !attributes[attribute_map[key]].nil?
-          transformed_hash["#{key}"] = _deserialize(type, attributes[attribute_map[key]])
+        elsif !attributes[map[key]].nil?
+          transformed_hash["#{key}"] = _deserialize(type, attributes[map[key]])
         end
       end
       new(transformed_hash)
@@ -148,10 +160,11 @@ def self.build_from_hash(attributes)
     # @return [Hash] Returns the object in the form of hash
     def to_hash
       hash = {}
-      self.class.attribute_map.each_pair do |attr, param|
+      # include attributes inherited from allOf parents (the nearest declaration wins)
+      self.class.acceptable_attribute_map.each_pair do |attr, param|
         value = self.send(attr)
         if value.nil?
-          is_nullable = self.class.openapi_nullable.include?(attr)
+          is_nullable = self.class.acceptable_openapi_nullable.include?(attr)
           next if !is_nullable || (is_nullable && !instance_variable_defined?(:"@#{attr}"))
         end
 
diff --git a/samples/client/petstore/ruby-faraday/lib/petstore/models/outer_object_with_enum_property.rb b/samples/client/petstore/ruby-faraday/lib/petstore/models/outer_object_with_enum_property.rb
index 8ffad20f8d89..1fd79229d4f6 100644
--- a/samples/client/petstore/ruby-faraday/lib/petstore/models/outer_object_with_enum_property.rb
+++ b/samples/client/petstore/ruby-faraday/lib/petstore/models/outer_object_with_enum_property.rb
@@ -69,6 +69,16 @@ def self.openapi_nullable
       ])
     end
 
+    # Returns attribute type mapping
+    def self.acceptable_openapi_types
+      openapi_types
+    end
+
+    # Returns the nullable attributes
+    def self.acceptable_openapi_nullable
+      openapi_nullable
+    end
+
     # Initializes the object
     # @param [Hash] attributes Model attributes in the form of hash
     def initialize(attributes = {})
@@ -148,18 +158,20 @@ def hash
     def self.build_from_hash(attributes)
       return nil unless attributes.is_a?(Hash)
       attributes = attributes.transform_keys(&:to_sym)
+      # include attributes inherited from allOf parents (the nearest declaration wins)
+      map = acceptable_attribute_map
       transformed_hash = {}
-      openapi_types.each_pair do |key, type|
-        if attributes.key?(attribute_map[key]) && attributes[attribute_map[key]].nil?
+      acceptable_openapi_types.each_pair do |key, type|
+        if attributes.key?(map[key]) && attributes[map[key]].nil?
           transformed_hash["#{key}"] = nil
         elsif type =~ /\AArray<(.*)>/i
           # check to ensure the input is an array given that the attribute
           # is documented as an array but the input is not
-          if attributes[attribute_map[key]].is_a?(Array)
-            transformed_hash["#{key}"] = attributes[attribute_map[key]].map { |v| _deserialize($1, v) }
+          if attributes[map[key]].is_a?(Array)
+            transformed_hash["#{key}"] = attributes[map[key]].map { |v| _deserialize($1, v) }
           end
-        elsif !attributes[attribute_map[key]].nil?
-          transformed_hash["#{key}"] = _deserialize(type, attributes[attribute_map[key]])
+        elsif !attributes[map[key]].nil?
+          transformed_hash["#{key}"] = _deserialize(type, attributes[map[key]])
         end
       end
       new(transformed_hash)
@@ -169,10 +181,11 @@ def self.build_from_hash(attributes)
     # @return [Hash] Returns the object in the form of hash
     def to_hash
       hash = {}
-      self.class.attribute_map.each_pair do |attr, param|
+      # include attributes inherited from allOf parents (the nearest declaration wins)
+      self.class.acceptable_attribute_map.each_pair do |attr, param|
         value = self.send(attr)
         if value.nil?
-          is_nullable = self.class.openapi_nullable.include?(attr)
+          is_nullable = self.class.acceptable_openapi_nullable.include?(attr)
           next if !is_nullable || (is_nullable && !instance_variable_defined?(:"@#{attr}"))
         end
 
diff --git a/samples/client/petstore/ruby-faraday/lib/petstore/models/pet.rb b/samples/client/petstore/ruby-faraday/lib/petstore/models/pet.rb
index e3594a1fb052..5a86112a15cf 100644
--- a/samples/client/petstore/ruby-faraday/lib/petstore/models/pet.rb
+++ b/samples/client/petstore/ruby-faraday/lib/petstore/models/pet.rb
@@ -90,6 +90,16 @@ def self.openapi_nullable
       ])
     end
 
+    # Returns attribute type mapping
+    def self.acceptable_openapi_types
+      openapi_types
+    end
+
+    # Returns the nullable attributes
+    def self.acceptable_openapi_nullable
+      openapi_nullable
+    end
+
     # Initializes the object
     # @param [Hash] attributes Model attributes in the form of hash
     def initialize(attributes = {})
@@ -227,18 +237,20 @@ def hash
     def self.build_from_hash(attributes)
       return nil unless attributes.is_a?(Hash)
       attributes = attributes.transform_keys(&:to_sym)
+      # include attributes inherited from allOf parents (the nearest declaration wins)
+      map = acceptable_attribute_map
       transformed_hash = {}
-      openapi_types.each_pair do |key, type|
-        if attributes.key?(attribute_map[key]) && attributes[attribute_map[key]].nil?
+      acceptable_openapi_types.each_pair do |key, type|
+        if attributes.key?(map[key]) && attributes[map[key]].nil?
           transformed_hash["#{key}"] = nil
         elsif type =~ /\AArray<(.*)>/i
           # check to ensure the input is an array given that the attribute
           # is documented as an array but the input is not
-          if attributes[attribute_map[key]].is_a?(Array)
-            transformed_hash["#{key}"] = attributes[attribute_map[key]].map { |v| _deserialize($1, v) }
+          if attributes[map[key]].is_a?(Array)
+            transformed_hash["#{key}"] = attributes[map[key]].map { |v| _deserialize($1, v) }
           end
-        elsif !attributes[attribute_map[key]].nil?
-          transformed_hash["#{key}"] = _deserialize(type, attributes[attribute_map[key]])
+        elsif !attributes[map[key]].nil?
+          transformed_hash["#{key}"] = _deserialize(type, attributes[map[key]])
         end
       end
       new(transformed_hash)
@@ -248,10 +260,11 @@ def self.build_from_hash(attributes)
     # @return [Hash] Returns the object in the form of hash
     def to_hash
       hash = {}
-      self.class.attribute_map.each_pair do |attr, param|
+      # include attributes inherited from allOf parents (the nearest declaration wins)
+      self.class.acceptable_attribute_map.each_pair do |attr, param|
         value = self.send(attr)
         if value.nil?
-          is_nullable = self.class.openapi_nullable.include?(attr)
+          is_nullable = self.class.acceptable_openapi_nullable.include?(attr)
           next if !is_nullable || (is_nullable && !instance_variable_defined?(:"@#{attr}"))
         end
 
diff --git a/samples/client/petstore/ruby-faraday/lib/petstore/models/property_name_mapping.rb b/samples/client/petstore/ruby-faraday/lib/petstore/models/property_name_mapping.rb
index 8328edb9227a..82c1d3be0d08 100644
--- a/samples/client/petstore/ruby-faraday/lib/petstore/models/property_name_mapping.rb
+++ b/samples/client/petstore/ruby-faraday/lib/petstore/models/property_name_mapping.rb
@@ -59,6 +59,16 @@ def self.openapi_nullable
       ])
     end
 
+    # Returns attribute type mapping
+    def self.acceptable_openapi_types
+      openapi_types
+    end
+
+    # Returns the nullable attributes
+    def self.acceptable_openapi_nullable
+      openapi_nullable
+    end
+
     # Initializes the object
     # @param [Hash] attributes Model attributes in the form of hash
     def initialize(attributes = {})
@@ -136,18 +146,20 @@ def hash
     def self.build_from_hash(attributes)
       return nil unless attributes.is_a?(Hash)
       attributes = attributes.transform_keys(&:to_sym)
+      # include attributes inherited from allOf parents (the nearest declaration wins)
+      map = acceptable_attribute_map
       transformed_hash = {}
-      openapi_types.each_pair do |key, type|
-        if attributes.key?(attribute_map[key]) && attributes[attribute_map[key]].nil?
+      acceptable_openapi_types.each_pair do |key, type|
+        if attributes.key?(map[key]) && attributes[map[key]].nil?
           transformed_hash["#{key}"] = nil
         elsif type =~ /\AArray<(.*)>/i
           # check to ensure the input is an array given that the attribute
           # is documented as an array but the input is not
-          if attributes[attribute_map[key]].is_a?(Array)
-            transformed_hash["#{key}"] = attributes[attribute_map[key]].map { |v| _deserialize($1, v) }
+          if attributes[map[key]].is_a?(Array)
+            transformed_hash["#{key}"] = attributes[map[key]].map { |v| _deserialize($1, v) }
           end
-        elsif !attributes[attribute_map[key]].nil?
-          transformed_hash["#{key}"] = _deserialize(type, attributes[attribute_map[key]])
+        elsif !attributes[map[key]].nil?
+          transformed_hash["#{key}"] = _deserialize(type, attributes[map[key]])
         end
       end
       new(transformed_hash)
@@ -157,10 +169,11 @@ def self.build_from_hash(attributes)
     # @return [Hash] Returns the object in the form of hash
     def to_hash
       hash = {}
-      self.class.attribute_map.each_pair do |attr, param|
+      # include attributes inherited from allOf parents (the nearest declaration wins)
+      self.class.acceptable_attribute_map.each_pair do |attr, param|
         value = self.send(attr)
         if value.nil?
-          is_nullable = self.class.openapi_nullable.include?(attr)
+          is_nullable = self.class.acceptable_openapi_nullable.include?(attr)
           next if !is_nullable || (is_nullable && !instance_variable_defined?(:"@#{attr}"))
         end
 
diff --git a/samples/client/petstore/ruby-faraday/lib/petstore/models/read_only_first.rb b/samples/client/petstore/ruby-faraday/lib/petstore/models/read_only_first.rb
index c2121474ebb7..d008b4369a91 100644
--- a/samples/client/petstore/ruby-faraday/lib/petstore/models/read_only_first.rb
+++ b/samples/client/petstore/ruby-faraday/lib/petstore/models/read_only_first.rb
@@ -51,6 +51,16 @@ def self.openapi_nullable
       ])
     end
 
+    # Returns attribute type mapping
+    def self.acceptable_openapi_types
+      openapi_types
+    end
+
+    # Returns the nullable attributes
+    def self.acceptable_openapi_nullable
+      openapi_nullable
+    end
+
     # Initializes the object
     # @param [Hash] attributes Model attributes in the form of hash
     def initialize(attributes = {})
@@ -118,18 +128,20 @@ def hash
     def self.build_from_hash(attributes)
       return nil unless attributes.is_a?(Hash)
       attributes = attributes.transform_keys(&:to_sym)
+      # include attributes inherited from allOf parents (the nearest declaration wins)
+      map = acceptable_attribute_map
       transformed_hash = {}
-      openapi_types.each_pair do |key, type|
-        if attributes.key?(attribute_map[key]) && attributes[attribute_map[key]].nil?
+      acceptable_openapi_types.each_pair do |key, type|
+        if attributes.key?(map[key]) && attributes[map[key]].nil?
           transformed_hash["#{key}"] = nil
         elsif type =~ /\AArray<(.*)>/i
           # check to ensure the input is an array given that the attribute
           # is documented as an array but the input is not
-          if attributes[attribute_map[key]].is_a?(Array)
-            transformed_hash["#{key}"] = attributes[attribute_map[key]].map { |v| _deserialize($1, v) }
+          if attributes[map[key]].is_a?(Array)
+            transformed_hash["#{key}"] = attributes[map[key]].map { |v| _deserialize($1, v) }
           end
-        elsif !attributes[attribute_map[key]].nil?
-          transformed_hash["#{key}"] = _deserialize(type, attributes[attribute_map[key]])
+        elsif !attributes[map[key]].nil?
+          transformed_hash["#{key}"] = _deserialize(type, attributes[map[key]])
         end
       end
       new(transformed_hash)
@@ -139,10 +151,11 @@ def self.build_from_hash(attributes)
     # @return [Hash] Returns the object in the form of hash
     def to_hash
       hash = {}
-      self.class.attribute_map.each_pair do |attr, param|
+      # include attributes inherited from allOf parents (the nearest declaration wins)
+      self.class.acceptable_attribute_map.each_pair do |attr, param|
         value = self.send(attr)
         if value.nil?
-          is_nullable = self.class.openapi_nullable.include?(attr)
+          is_nullable = self.class.acceptable_openapi_nullable.include?(attr)
           next if !is_nullable || (is_nullable && !instance_variable_defined?(:"@#{attr}"))
         end
 
diff --git a/samples/client/petstore/ruby-faraday/lib/petstore/models/special_model_name.rb b/samples/client/petstore/ruby-faraday/lib/petstore/models/special_model_name.rb
index 9569fbfd13dd..b6d4135991be 100644
--- a/samples/client/petstore/ruby-faraday/lib/petstore/models/special_model_name.rb
+++ b/samples/client/petstore/ruby-faraday/lib/petstore/models/special_model_name.rb
@@ -47,6 +47,16 @@ def self.openapi_nullable
       ])
     end
 
+    # Returns attribute type mapping
+    def self.acceptable_openapi_types
+      openapi_types
+    end
+
+    # Returns the nullable attributes
+    def self.acceptable_openapi_nullable
+      openapi_nullable
+    end
+
     # Initializes the object
     # @param [Hash] attributes Model attributes in the form of hash
     def initialize(attributes = {})
@@ -109,18 +119,20 @@ def hash
     def self.build_from_hash(attributes)
       return nil unless attributes.is_a?(Hash)
       attributes = attributes.transform_keys(&:to_sym)
+      # include attributes inherited from allOf parents (the nearest declaration wins)
+      map = acceptable_attribute_map
       transformed_hash = {}
-      openapi_types.each_pair do |key, type|
-        if attributes.key?(attribute_map[key]) && attributes[attribute_map[key]].nil?
+      acceptable_openapi_types.each_pair do |key, type|
+        if attributes.key?(map[key]) && attributes[map[key]].nil?
           transformed_hash["#{key}"] = nil
         elsif type =~ /\AArray<(.*)>/i
           # check to ensure the input is an array given that the attribute
           # is documented as an array but the input is not
-          if attributes[attribute_map[key]].is_a?(Array)
-            transformed_hash["#{key}"] = attributes[attribute_map[key]].map { |v| _deserialize($1, v) }
+          if attributes[map[key]].is_a?(Array)
+            transformed_hash["#{key}"] = attributes[map[key]].map { |v| _deserialize($1, v) }
           end
-        elsif !attributes[attribute_map[key]].nil?
-          transformed_hash["#{key}"] = _deserialize(type, attributes[attribute_map[key]])
+        elsif !attributes[map[key]].nil?
+          transformed_hash["#{key}"] = _deserialize(type, attributes[map[key]])
         end
       end
       new(transformed_hash)
@@ -130,10 +142,11 @@ def self.build_from_hash(attributes)
     # @return [Hash] Returns the object in the form of hash
     def to_hash
       hash = {}
-      self.class.attribute_map.each_pair do |attr, param|
+      # include attributes inherited from allOf parents (the nearest declaration wins)
+      self.class.acceptable_attribute_map.each_pair do |attr, param|
         value = self.send(attr)
         if value.nil?
-          is_nullable = self.class.openapi_nullable.include?(attr)
+          is_nullable = self.class.acceptable_openapi_nullable.include?(attr)
           next if !is_nullable || (is_nullable && !instance_variable_defined?(:"@#{attr}"))
         end
 
diff --git a/samples/client/petstore/ruby-faraday/lib/petstore/models/tag.rb b/samples/client/petstore/ruby-faraday/lib/petstore/models/tag.rb
index 6d6f57468181..22589f4e58b3 100644
--- a/samples/client/petstore/ruby-faraday/lib/petstore/models/tag.rb
+++ b/samples/client/petstore/ruby-faraday/lib/petstore/models/tag.rb
@@ -51,6 +51,16 @@ def self.openapi_nullable
       ])
     end
 
+    # Returns attribute type mapping
+    def self.acceptable_openapi_types
+      openapi_types
+    end
+
+    # Returns the nullable attributes
+    def self.acceptable_openapi_nullable
+      openapi_nullable
+    end
+
     # Initializes the object
     # @param [Hash] attributes Model attributes in the form of hash
     def initialize(attributes = {})
@@ -118,18 +128,20 @@ def hash
     def self.build_from_hash(attributes)
       return nil unless attributes.is_a?(Hash)
       attributes = attributes.transform_keys(&:to_sym)
+      # include attributes inherited from allOf parents (the nearest declaration wins)
+      map = acceptable_attribute_map
       transformed_hash = {}
-      openapi_types.each_pair do |key, type|
-        if attributes.key?(attribute_map[key]) && attributes[attribute_map[key]].nil?
+      acceptable_openapi_types.each_pair do |key, type|
+        if attributes.key?(map[key]) && attributes[map[key]].nil?
           transformed_hash["#{key}"] = nil
         elsif type =~ /\AArray<(.*)>/i
           # check to ensure the input is an array given that the attribute
           # is documented as an array but the input is not
-          if attributes[attribute_map[key]].is_a?(Array)
-            transformed_hash["#{key}"] = attributes[attribute_map[key]].map { |v| _deserialize($1, v) }
+          if attributes[map[key]].is_a?(Array)
+            transformed_hash["#{key}"] = attributes[map[key]].map { |v| _deserialize($1, v) }
           end
-        elsif !attributes[attribute_map[key]].nil?
-          transformed_hash["#{key}"] = _deserialize(type, attributes[attribute_map[key]])
+        elsif !attributes[map[key]].nil?
+          transformed_hash["#{key}"] = _deserialize(type, attributes[map[key]])
         end
       end
       new(transformed_hash)
@@ -139,10 +151,11 @@ def self.build_from_hash(attributes)
     # @return [Hash] Returns the object in the form of hash
     def to_hash
       hash = {}
-      self.class.attribute_map.each_pair do |attr, param|
+      # include attributes inherited from allOf parents (the nearest declaration wins)
+      self.class.acceptable_attribute_map.each_pair do |attr, param|
         value = self.send(attr)
         if value.nil?
-          is_nullable = self.class.openapi_nullable.include?(attr)
+          is_nullable = self.class.acceptable_openapi_nullable.include?(attr)
           next if !is_nullable || (is_nullable && !instance_variable_defined?(:"@#{attr}"))
         end
 
diff --git a/samples/client/petstore/ruby-faraday/lib/petstore/models/test_inline_freeform_additional_properties_request.rb b/samples/client/petstore/ruby-faraday/lib/petstore/models/test_inline_freeform_additional_properties_request.rb
index dc481c119d22..9e52e64e286b 100644
--- a/samples/client/petstore/ruby-faraday/lib/petstore/models/test_inline_freeform_additional_properties_request.rb
+++ b/samples/client/petstore/ruby-faraday/lib/petstore/models/test_inline_freeform_additional_properties_request.rb
@@ -47,6 +47,16 @@ def self.openapi_nullable
       ])
     end
 
+    # Returns attribute type mapping
+    def self.acceptable_openapi_types
+      openapi_types
+    end
+
+    # Returns the nullable attributes
+    def self.acceptable_openapi_nullable
+      openapi_nullable
+    end
+
     # Initializes the object
     # @param [Hash] attributes Model attributes in the form of hash
     def initialize(attributes = {})
@@ -109,18 +119,20 @@ def hash
     def self.build_from_hash(attributes)
       return nil unless attributes.is_a?(Hash)
       attributes = attributes.transform_keys(&:to_sym)
+      # include attributes inherited from allOf parents (the nearest declaration wins)
+      map = acceptable_attribute_map
       transformed_hash = {}
-      openapi_types.each_pair do |key, type|
-        if attributes.key?(attribute_map[key]) && attributes[attribute_map[key]].nil?
+      acceptable_openapi_types.each_pair do |key, type|
+        if attributes.key?(map[key]) && attributes[map[key]].nil?
           transformed_hash["#{key}"] = nil
         elsif type =~ /\AArray<(.*)>/i
           # check to ensure the input is an array given that the attribute
           # is documented as an array but the input is not
-          if attributes[attribute_map[key]].is_a?(Array)
-            transformed_hash["#{key}"] = attributes[attribute_map[key]].map { |v| _deserialize($1, v) }
+          if attributes[map[key]].is_a?(Array)
+            transformed_hash["#{key}"] = attributes[map[key]].map { |v| _deserialize($1, v) }
           end
-        elsif !attributes[attribute_map[key]].nil?
-          transformed_hash["#{key}"] = _deserialize(type, attributes[attribute_map[key]])
+        elsif !attributes[map[key]].nil?
+          transformed_hash["#{key}"] = _deserialize(type, attributes[map[key]])
         end
       end
       new(transformed_hash)
@@ -130,10 +142,11 @@ def self.build_from_hash(attributes)
     # @return [Hash] Returns the object in the form of hash
     def to_hash
       hash = {}
-      self.class.attribute_map.each_pair do |attr, param|
+      # include attributes inherited from allOf parents (the nearest declaration wins)
+      self.class.acceptable_attribute_map.each_pair do |attr, param|
         value = self.send(attr)
         if value.nil?
-          is_nullable = self.class.openapi_nullable.include?(attr)
+          is_nullable = self.class.acceptable_openapi_nullable.include?(attr)
           next if !is_nullable || (is_nullable && !instance_variable_defined?(:"@#{attr}"))
         end
 
diff --git a/samples/client/petstore/ruby-faraday/lib/petstore/models/user.rb b/samples/client/petstore/ruby-faraday/lib/petstore/models/user.rb
index 9b06f2ff6d7a..4b67db8214e2 100644
--- a/samples/client/petstore/ruby-faraday/lib/petstore/models/user.rb
+++ b/samples/client/petstore/ruby-faraday/lib/petstore/models/user.rb
@@ -76,6 +76,16 @@ def self.openapi_nullable
       ])
     end
 
+    # Returns attribute type mapping
+    def self.acceptable_openapi_types
+      openapi_types
+    end
+
+    # Returns the nullable attributes
+    def self.acceptable_openapi_nullable
+      openapi_nullable
+    end
+
     # Initializes the object
     # @param [Hash] attributes Model attributes in the form of hash
     def initialize(attributes = {})
@@ -173,18 +183,20 @@ def hash
     def self.build_from_hash(attributes)
       return nil unless attributes.is_a?(Hash)
       attributes = attributes.transform_keys(&:to_sym)
+      # include attributes inherited from allOf parents (the nearest declaration wins)
+      map = acceptable_attribute_map
       transformed_hash = {}
-      openapi_types.each_pair do |key, type|
-        if attributes.key?(attribute_map[key]) && attributes[attribute_map[key]].nil?
+      acceptable_openapi_types.each_pair do |key, type|
+        if attributes.key?(map[key]) && attributes[map[key]].nil?
           transformed_hash["#{key}"] = nil
         elsif type =~ /\AArray<(.*)>/i
           # check to ensure the input is an array given that the attribute
           # is documented as an array but the input is not
-          if attributes[attribute_map[key]].is_a?(Array)
-            transformed_hash["#{key}"] = attributes[attribute_map[key]].map { |v| _deserialize($1, v) }
+          if attributes[map[key]].is_a?(Array)
+            transformed_hash["#{key}"] = attributes[map[key]].map { |v| _deserialize($1, v) }
           end
-        elsif !attributes[attribute_map[key]].nil?
-          transformed_hash["#{key}"] = _deserialize(type, attributes[attribute_map[key]])
+        elsif !attributes[map[key]].nil?
+          transformed_hash["#{key}"] = _deserialize(type, attributes[map[key]])
         end
       end
       new(transformed_hash)
@@ -194,10 +206,11 @@ def self.build_from_hash(attributes)
     # @return [Hash] Returns the object in the form of hash
     def to_hash
       hash = {}
-      self.class.attribute_map.each_pair do |attr, param|
+      # include attributes inherited from allOf parents (the nearest declaration wins)
+      self.class.acceptable_attribute_map.each_pair do |attr, param|
         value = self.send(attr)
         if value.nil?
-          is_nullable = self.class.openapi_nullable.include?(attr)
+          is_nullable = self.class.acceptable_openapi_nullable.include?(attr)
           next if !is_nullable || (is_nullable && !instance_variable_defined?(:"@#{attr}"))
         end
 
diff --git a/samples/client/petstore/ruby-faraday/lib/petstore/models/whale.rb b/samples/client/petstore/ruby-faraday/lib/petstore/models/whale.rb
index 23249be434e4..f29de72ecb1a 100644
--- a/samples/client/petstore/ruby-faraday/lib/petstore/models/whale.rb
+++ b/samples/client/petstore/ruby-faraday/lib/petstore/models/whale.rb
@@ -55,6 +55,16 @@ def self.openapi_nullable
       ])
     end
 
+    # Returns attribute type mapping
+    def self.acceptable_openapi_types
+      openapi_types
+    end
+
+    # Returns the nullable attributes
+    def self.acceptable_openapi_nullable
+      openapi_nullable
+    end
+
     # Initializes the object
     # @param [Hash] attributes Model attributes in the form of hash
     def initialize(attributes = {})
@@ -144,18 +154,20 @@ def hash
     def self.build_from_hash(attributes)
       return nil unless attributes.is_a?(Hash)
       attributes = attributes.transform_keys(&:to_sym)
+      # include attributes inherited from allOf parents (the nearest declaration wins)
+      map = acceptable_attribute_map
       transformed_hash = {}
-      openapi_types.each_pair do |key, type|
-        if attributes.key?(attribute_map[key]) && attributes[attribute_map[key]].nil?
+      acceptable_openapi_types.each_pair do |key, type|
+        if attributes.key?(map[key]) && attributes[map[key]].nil?
           transformed_hash["#{key}"] = nil
         elsif type =~ /\AArray<(.*)>/i
           # check to ensure the input is an array given that the attribute
           # is documented as an array but the input is not
-          if attributes[attribute_map[key]].is_a?(Array)
-            transformed_hash["#{key}"] = attributes[attribute_map[key]].map { |v| _deserialize($1, v) }
+          if attributes[map[key]].is_a?(Array)
+            transformed_hash["#{key}"] = attributes[map[key]].map { |v| _deserialize($1, v) }
           end
-        elsif !attributes[attribute_map[key]].nil?
-          transformed_hash["#{key}"] = _deserialize(type, attributes[attribute_map[key]])
+        elsif !attributes[map[key]].nil?
+          transformed_hash["#{key}"] = _deserialize(type, attributes[map[key]])
         end
       end
       new(transformed_hash)
@@ -165,10 +177,11 @@ def self.build_from_hash(attributes)
     # @return [Hash] Returns the object in the form of hash
     def to_hash
       hash = {}
-      self.class.attribute_map.each_pair do |attr, param|
+      # include attributes inherited from allOf parents (the nearest declaration wins)
+      self.class.acceptable_attribute_map.each_pair do |attr, param|
         value = self.send(attr)
         if value.nil?
-          is_nullable = self.class.openapi_nullable.include?(attr)
+          is_nullable = self.class.acceptable_openapi_nullable.include?(attr)
           next if !is_nullable || (is_nullable && !instance_variable_defined?(:"@#{attr}"))
         end
 
diff --git a/samples/client/petstore/ruby-faraday/lib/petstore/models/zebra.rb b/samples/client/petstore/ruby-faraday/lib/petstore/models/zebra.rb
index 10e910f409f7..79771e498151 100644
--- a/samples/client/petstore/ruby-faraday/lib/petstore/models/zebra.rb
+++ b/samples/client/petstore/ruby-faraday/lib/petstore/models/zebra.rb
@@ -73,6 +73,16 @@ def self.openapi_nullable
       ])
     end
 
+    # Returns attribute type mapping
+    def self.acceptable_openapi_types
+      openapi_types
+    end
+
+    # Returns the nullable attributes
+    def self.acceptable_openapi_nullable
+      openapi_nullable
+    end
+
     # Initializes the object
     # @param [Hash] attributes Model attributes in the form of hash
     def initialize(attributes = {})
@@ -169,18 +179,20 @@ def hash
     def self.build_from_hash(attributes)
       return nil unless attributes.is_a?(Hash)
       attributes = attributes.transform_keys(&:to_sym)
+      # include attributes inherited from allOf parents (the nearest declaration wins)
+      map = acceptable_attribute_map
       transformed_hash = {}
-      openapi_types.each_pair do |key, type|
-        if attributes.key?(attribute_map[key]) && attributes[attribute_map[key]].nil?
+      acceptable_openapi_types.each_pair do |key, type|
+        if attributes.key?(map[key]) && attributes[map[key]].nil?
           transformed_hash["#{key}"] = nil
         elsif type =~ /\AArray<(.*)>/i
           # check to ensure the input is an array given that the attribute
           # is documented as an array but the input is not
-          if attributes[attribute_map[key]].is_a?(Array)
-            transformed_hash["#{key}"] = attributes[attribute_map[key]].map { |v| _deserialize($1, v) }
+          if attributes[map[key]].is_a?(Array)
+            transformed_hash["#{key}"] = attributes[map[key]].map { |v| _deserialize($1, v) }
           end
-        elsif !attributes[attribute_map[key]].nil?
-          transformed_hash["#{key}"] = _deserialize(type, attributes[attribute_map[key]])
+        elsif !attributes[map[key]].nil?
+          transformed_hash["#{key}"] = _deserialize(type, attributes[map[key]])
         end
       end
       new(transformed_hash)
@@ -190,10 +202,11 @@ def self.build_from_hash(attributes)
     # @return [Hash] Returns the object in the form of hash
     def to_hash
       hash = {}
-      self.class.attribute_map.each_pair do |attr, param|
+      # include attributes inherited from allOf parents (the nearest declaration wins)
+      self.class.acceptable_attribute_map.each_pair do |attr, param|
         value = self.send(attr)
         if value.nil?
-          is_nullable = self.class.openapi_nullable.include?(attr)
+          is_nullable = self.class.acceptable_openapi_nullable.include?(attr)
           next if !is_nullable || (is_nullable && !instance_variable_defined?(:"@#{attr}"))
         end
 
diff --git a/samples/client/petstore/ruby-faraday/spec/custom/base_object_spec.rb b/samples/client/petstore/ruby-faraday/spec/custom/base_object_spec.rb
index a046c5bd4e11..bc0ed63000b4 100644
--- a/samples/client/petstore/ruby-faraday/spec/custom/base_object_spec.rb
+++ b/samples/client/petstore/ruby-faraday/spec/custom/base_object_spec.rb
@@ -166,4 +166,34 @@ def initialize(attributes = {})
       expect(obj.to_hash).to eq(expect_data)
     end
   end
+
+  describe 'attributes inherited from an allOf parent' do
+    it 'build_from_hash and to_hash include the parent attributes' do
+      cat = Petstore::Cat.build_from_hash({ 'className' => 'Cat', 'color' => 'black', 'declawed' => true })
+
+      expect(cat).to be_instance_of(Petstore::Cat)
+      expect(cat.class_name).to eq('Cat')
+      expect(cat.color).to eq('black')
+      expect(cat.declawed).to eq(true)
+      expect(cat.to_hash).to eq({ className: 'Cat', color: 'black', declawed: true })
+    end
+
+    # passes on master too: guards that a subclass narrowing attribute_map is not handed its parent's attributes
+    it 'a subclass that narrows attribute_map is only handed the attributes it accepts' do
+      narrowed = Class.new(Petstore::Animal) do
+        def self.attribute_map
+          { :class_name => :className }
+        end
+
+        def self.openapi_types
+          { :class_name => :'String' }
+        end
+      end
+
+      obj = narrowed.build_from_hash({ 'className' => 'Cat', 'color' => 'black' })
+
+      expect(obj.class_name).to eq('Cat')
+      expect(obj.to_hash).to eq({ className: 'Cat' })
+    end
+  end
 end
diff --git a/samples/client/petstore/ruby-httpx/lib/petstore/models/additional_properties_class.rb b/samples/client/petstore/ruby-httpx/lib/petstore/models/additional_properties_class.rb
index 9b823593d156..a240cadf547e 100644
--- a/samples/client/petstore/ruby-httpx/lib/petstore/models/additional_properties_class.rb
+++ b/samples/client/petstore/ruby-httpx/lib/petstore/models/additional_properties_class.rb
@@ -51,6 +51,16 @@ def self.openapi_nullable
       ])
     end
 
+    # Returns attribute type mapping
+    def self.acceptable_openapi_types
+      openapi_types
+    end
+
+    # Returns the nullable attributes
+    def self.acceptable_openapi_nullable
+      openapi_nullable
+    end
+
     # Initializes the object
     # @param [Hash] attributes Model attributes in the form of hash
     def initialize(attributes = {})
@@ -122,18 +132,20 @@ def hash
     def self.build_from_hash(attributes)
       return nil unless attributes.is_a?(Hash)
       attributes = attributes.transform_keys(&:to_sym)
+      # include attributes inherited from allOf parents (the nearest declaration wins)
+      map = acceptable_attribute_map
       transformed_hash = {}
-      openapi_types.each_pair do |key, type|
-        if attributes.key?(attribute_map[key]) && attributes[attribute_map[key]].nil?
+      acceptable_openapi_types.each_pair do |key, type|
+        if attributes.key?(map[key]) && attributes[map[key]].nil?
           transformed_hash["#{key}"] = nil
         elsif type =~ /\AArray<(.*)>/i
           # check to ensure the input is an array given that the attribute
           # is documented as an array but the input is not
-          if attributes[attribute_map[key]].is_a?(Array)
-            transformed_hash["#{key}"] = attributes[attribute_map[key]].map { |v| _deserialize($1, v) }
+          if attributes[map[key]].is_a?(Array)
+            transformed_hash["#{key}"] = attributes[map[key]].map { |v| _deserialize($1, v) }
           end
-        elsif !attributes[attribute_map[key]].nil?
-          transformed_hash["#{key}"] = _deserialize(type, attributes[attribute_map[key]])
+        elsif !attributes[map[key]].nil?
+          transformed_hash["#{key}"] = _deserialize(type, attributes[map[key]])
         end
       end
       new(transformed_hash)
@@ -143,10 +155,11 @@ def self.build_from_hash(attributes)
     # @return [Hash] Returns the object in the form of hash
     def to_hash
       hash = {}
-      self.class.attribute_map.each_pair do |attr, param|
+      # include attributes inherited from allOf parents (the nearest declaration wins)
+      self.class.acceptable_attribute_map.each_pair do |attr, param|
         value = self.send(attr)
         if value.nil?
-          is_nullable = self.class.openapi_nullable.include?(attr)
+          is_nullable = self.class.acceptable_openapi_nullable.include?(attr)
           next if !is_nullable || (is_nullable && !instance_variable_defined?(:"@#{attr}"))
         end
 
diff --git a/samples/client/petstore/ruby-httpx/lib/petstore/models/all_of_with_single_ref.rb b/samples/client/petstore/ruby-httpx/lib/petstore/models/all_of_with_single_ref.rb
index 600c974fa1e5..9977e0212627 100644
--- a/samples/client/petstore/ruby-httpx/lib/petstore/models/all_of_with_single_ref.rb
+++ b/samples/client/petstore/ruby-httpx/lib/petstore/models/all_of_with_single_ref.rb
@@ -73,6 +73,16 @@ def self.openapi_nullable
       ])
     end
 
+    # Returns attribute type mapping
+    def self.acceptable_openapi_types
+      openapi_types
+    end
+
+    # Returns the nullable attributes
+    def self.acceptable_openapi_nullable
+      openapi_nullable
+    end
+
     # Initializes the object
     # @param [Hash] attributes Model attributes in the form of hash
     def initialize(attributes = {})
@@ -140,18 +150,20 @@ def hash
     def self.build_from_hash(attributes)
       return nil unless attributes.is_a?(Hash)
       attributes = attributes.transform_keys(&:to_sym)
+      # include attributes inherited from allOf parents (the nearest declaration wins)
+      map = acceptable_attribute_map
       transformed_hash = {}
-      openapi_types.each_pair do |key, type|
-        if attributes.key?(attribute_map[key]) && attributes[attribute_map[key]].nil?
+      acceptable_openapi_types.each_pair do |key, type|
+        if attributes.key?(map[key]) && attributes[map[key]].nil?
           transformed_hash["#{key}"] = nil
         elsif type =~ /\AArray<(.*)>/i
           # check to ensure the input is an array given that the attribute
           # is documented as an array but the input is not
-          if attributes[attribute_map[key]].is_a?(Array)
-            transformed_hash["#{key}"] = attributes[attribute_map[key]].map { |v| _deserialize($1, v) }
+          if attributes[map[key]].is_a?(Array)
+            transformed_hash["#{key}"] = attributes[map[key]].map { |v| _deserialize($1, v) }
           end
-        elsif !attributes[attribute_map[key]].nil?
-          transformed_hash["#{key}"] = _deserialize(type, attributes[attribute_map[key]])
+        elsif !attributes[map[key]].nil?
+          transformed_hash["#{key}"] = _deserialize(type, attributes[map[key]])
         end
       end
       new(transformed_hash)
@@ -161,10 +173,11 @@ def self.build_from_hash(attributes)
     # @return [Hash] Returns the object in the form of hash
     def to_hash
       hash = {}
-      self.class.attribute_map.each_pair do |attr, param|
+      # include attributes inherited from allOf parents (the nearest declaration wins)
+      self.class.acceptable_attribute_map.each_pair do |attr, param|
         value = self.send(attr)
         if value.nil?
-          is_nullable = self.class.openapi_nullable.include?(attr)
+          is_nullable = self.class.acceptable_openapi_nullable.include?(attr)
           next if !is_nullable || (is_nullable && !instance_variable_defined?(:"@#{attr}"))
         end
 
diff --git a/samples/client/petstore/ruby-httpx/lib/petstore/models/animal.rb b/samples/client/petstore/ruby-httpx/lib/petstore/models/animal.rb
index 21d89bccb837..b58dbb506d4e 100644
--- a/samples/client/petstore/ruby-httpx/lib/petstore/models/animal.rb
+++ b/samples/client/petstore/ruby-httpx/lib/petstore/models/animal.rb
@@ -51,6 +51,16 @@ def self.openapi_nullable
       ])
     end
 
+    # Returns attribute type mapping
+    def self.acceptable_openapi_types
+      openapi_types
+    end
+
+    # Returns the nullable attributes
+    def self.acceptable_openapi_nullable
+      openapi_nullable
+    end
+
     # discriminator's property name in OpenAPI v3
     def self.openapi_discriminator_name
       :'class_name'
@@ -142,18 +152,20 @@ def hash
     def self.build_from_hash(attributes)
       return nil unless attributes.is_a?(Hash)
       attributes = attributes.transform_keys(&:to_sym)
+      # include attributes inherited from allOf parents (the nearest declaration wins)
+      map = acceptable_attribute_map
       transformed_hash = {}
-      openapi_types.each_pair do |key, type|
-        if attributes.key?(attribute_map[key]) && attributes[attribute_map[key]].nil?
+      acceptable_openapi_types.each_pair do |key, type|
+        if attributes.key?(map[key]) && attributes[map[key]].nil?
           transformed_hash["#{key}"] = nil
         elsif type =~ /\AArray<(.*)>/i
           # check to ensure the input is an array given that the attribute
           # is documented as an array but the input is not
-          if attributes[attribute_map[key]].is_a?(Array)
-            transformed_hash["#{key}"] = attributes[attribute_map[key]].map { |v| _deserialize($1, v) }
+          if attributes[map[key]].is_a?(Array)
+            transformed_hash["#{key}"] = attributes[map[key]].map { |v| _deserialize($1, v) }
           end
-        elsif !attributes[attribute_map[key]].nil?
-          transformed_hash["#{key}"] = _deserialize(type, attributes[attribute_map[key]])
+        elsif !attributes[map[key]].nil?
+          transformed_hash["#{key}"] = _deserialize(type, attributes[map[key]])
         end
       end
       new(transformed_hash)
@@ -163,10 +175,11 @@ def self.build_from_hash(attributes)
     # @return [Hash] Returns the object in the form of hash
     def to_hash
       hash = {}
-      self.class.attribute_map.each_pair do |attr, param|
+      # include attributes inherited from allOf parents (the nearest declaration wins)
+      self.class.acceptable_attribute_map.each_pair do |attr, param|
         value = self.send(attr)
         if value.nil?
-          is_nullable = self.class.openapi_nullable.include?(attr)
+          is_nullable = self.class.acceptable_openapi_nullable.include?(attr)
           next if !is_nullable || (is_nullable && !instance_variable_defined?(:"@#{attr}"))
         end
 
diff --git a/samples/client/petstore/ruby-httpx/lib/petstore/models/api_response.rb b/samples/client/petstore/ruby-httpx/lib/petstore/models/api_response.rb
index bbbaf9358be2..6b8e2bf4005f 100644
--- a/samples/client/petstore/ruby-httpx/lib/petstore/models/api_response.rb
+++ b/samples/client/petstore/ruby-httpx/lib/petstore/models/api_response.rb
@@ -55,6 +55,16 @@ def self.openapi_nullable
       ])
     end
 
+    # Returns attribute type mapping
+    def self.acceptable_openapi_types
+      openapi_types
+    end
+
+    # Returns the nullable attributes
+    def self.acceptable_openapi_nullable
+      openapi_nullable
+    end
+
     # Initializes the object
     # @param [Hash] attributes Model attributes in the form of hash
     def initialize(attributes = {})
@@ -127,18 +137,20 @@ def hash
     def self.build_from_hash(attributes)
       return nil unless attributes.is_a?(Hash)
       attributes = attributes.transform_keys(&:to_sym)
+      # include attributes inherited from allOf parents (the nearest declaration wins)
+      map = acceptable_attribute_map
       transformed_hash = {}
-      openapi_types.each_pair do |key, type|
-        if attributes.key?(attribute_map[key]) && attributes[attribute_map[key]].nil?
+      acceptable_openapi_types.each_pair do |key, type|
+        if attributes.key?(map[key]) && attributes[map[key]].nil?
           transformed_hash["#{key}"] = nil
         elsif type =~ /\AArray<(.*)>/i
           # check to ensure the input is an array given that the attribute
           # is documented as an array but the input is not
-          if attributes[attribute_map[key]].is_a?(Array)
-            transformed_hash["#{key}"] = attributes[attribute_map[key]].map { |v| _deserialize($1, v) }
+          if attributes[map[key]].is_a?(Array)
+            transformed_hash["#{key}"] = attributes[map[key]].map { |v| _deserialize($1, v) }
           end
-        elsif !attributes[attribute_map[key]].nil?
-          transformed_hash["#{key}"] = _deserialize(type, attributes[attribute_map[key]])
+        elsif !attributes[map[key]].nil?
+          transformed_hash["#{key}"] = _deserialize(type, attributes[map[key]])
         end
       end
       new(transformed_hash)
@@ -148,10 +160,11 @@ def self.build_from_hash(attributes)
     # @return [Hash] Returns the object in the form of hash
     def to_hash
       hash = {}
-      self.class.attribute_map.each_pair do |attr, param|
+      # include attributes inherited from allOf parents (the nearest declaration wins)
+      self.class.acceptable_attribute_map.each_pair do |attr, param|
         value = self.send(attr)
         if value.nil?
-          is_nullable = self.class.openapi_nullable.include?(attr)
+          is_nullable = self.class.acceptable_openapi_nullable.include?(attr)
           next if !is_nullable || (is_nullable && !instance_variable_defined?(:"@#{attr}"))
         end
 
diff --git a/samples/client/petstore/ruby-httpx/lib/petstore/models/array_of_array_of_number_only.rb b/samples/client/petstore/ruby-httpx/lib/petstore/models/array_of_array_of_number_only.rb
index e20b1728d130..40b968094257 100644
--- a/samples/client/petstore/ruby-httpx/lib/petstore/models/array_of_array_of_number_only.rb
+++ b/samples/client/petstore/ruby-httpx/lib/petstore/models/array_of_array_of_number_only.rb
@@ -47,6 +47,16 @@ def self.openapi_nullable
       ])
     end
 
+    # Returns attribute type mapping
+    def self.acceptable_openapi_types
+      openapi_types
+    end
+
+    # Returns the nullable attributes
+    def self.acceptable_openapi_nullable
+      openapi_nullable
+    end
+
     # Initializes the object
     # @param [Hash] attributes Model attributes in the form of hash
     def initialize(attributes = {})
@@ -111,18 +121,20 @@ def hash
     def self.build_from_hash(attributes)
       return nil unless attributes.is_a?(Hash)
       attributes = attributes.transform_keys(&:to_sym)
+      # include attributes inherited from allOf parents (the nearest declaration wins)
+      map = acceptable_attribute_map
       transformed_hash = {}
-      openapi_types.each_pair do |key, type|
-        if attributes.key?(attribute_map[key]) && attributes[attribute_map[key]].nil?
+      acceptable_openapi_types.each_pair do |key, type|
+        if attributes.key?(map[key]) && attributes[map[key]].nil?
           transformed_hash["#{key}"] = nil
         elsif type =~ /\AArray<(.*)>/i
           # check to ensure the input is an array given that the attribute
           # is documented as an array but the input is not
-          if attributes[attribute_map[key]].is_a?(Array)
-            transformed_hash["#{key}"] = attributes[attribute_map[key]].map { |v| _deserialize($1, v) }
+          if attributes[map[key]].is_a?(Array)
+            transformed_hash["#{key}"] = attributes[map[key]].map { |v| _deserialize($1, v) }
           end
-        elsif !attributes[attribute_map[key]].nil?
-          transformed_hash["#{key}"] = _deserialize(type, attributes[attribute_map[key]])
+        elsif !attributes[map[key]].nil?
+          transformed_hash["#{key}"] = _deserialize(type, attributes[map[key]])
         end
       end
       new(transformed_hash)
@@ -132,10 +144,11 @@ def self.build_from_hash(attributes)
     # @return [Hash] Returns the object in the form of hash
     def to_hash
       hash = {}
-      self.class.attribute_map.each_pair do |attr, param|
+      # include attributes inherited from allOf parents (the nearest declaration wins)
+      self.class.acceptable_attribute_map.each_pair do |attr, param|
         value = self.send(attr)
         if value.nil?
-          is_nullable = self.class.openapi_nullable.include?(attr)
+          is_nullable = self.class.acceptable_openapi_nullable.include?(attr)
           next if !is_nullable || (is_nullable && !instance_variable_defined?(:"@#{attr}"))
         end
 
diff --git a/samples/client/petstore/ruby-httpx/lib/petstore/models/array_of_number_only.rb b/samples/client/petstore/ruby-httpx/lib/petstore/models/array_of_number_only.rb
index 63890ff64424..6b9bc3627785 100644
--- a/samples/client/petstore/ruby-httpx/lib/petstore/models/array_of_number_only.rb
+++ b/samples/client/petstore/ruby-httpx/lib/petstore/models/array_of_number_only.rb
@@ -47,6 +47,16 @@ def self.openapi_nullable
       ])
     end
 
+    # Returns attribute type mapping
+    def self.acceptable_openapi_types
+      openapi_types
+    end
+
+    # Returns the nullable attributes
+    def self.acceptable_openapi_nullable
+      openapi_nullable
+    end
+
     # Initializes the object
     # @param [Hash] attributes Model attributes in the form of hash
     def initialize(attributes = {})
@@ -111,18 +121,20 @@ def hash
     def self.build_from_hash(attributes)
       return nil unless attributes.is_a?(Hash)
       attributes = attributes.transform_keys(&:to_sym)
+      # include attributes inherited from allOf parents (the nearest declaration wins)
+      map = acceptable_attribute_map
       transformed_hash = {}
-      openapi_types.each_pair do |key, type|
-        if attributes.key?(attribute_map[key]) && attributes[attribute_map[key]].nil?
+      acceptable_openapi_types.each_pair do |key, type|
+        if attributes.key?(map[key]) && attributes[map[key]].nil?
           transformed_hash["#{key}"] = nil
         elsif type =~ /\AArray<(.*)>/i
           # check to ensure the input is an array given that the attribute
           # is documented as an array but the input is not
-          if attributes[attribute_map[key]].is_a?(Array)
-            transformed_hash["#{key}"] = attributes[attribute_map[key]].map { |v| _deserialize($1, v) }
+          if attributes[map[key]].is_a?(Array)
+            transformed_hash["#{key}"] = attributes[map[key]].map { |v| _deserialize($1, v) }
           end
-        elsif !attributes[attribute_map[key]].nil?
-          transformed_hash["#{key}"] = _deserialize(type, attributes[attribute_map[key]])
+        elsif !attributes[map[key]].nil?
+          transformed_hash["#{key}"] = _deserialize(type, attributes[map[key]])
         end
       end
       new(transformed_hash)
@@ -132,10 +144,11 @@ def self.build_from_hash(attributes)
     # @return [Hash] Returns the object in the form of hash
     def to_hash
       hash = {}
-      self.class.attribute_map.each_pair do |attr, param|
+      # include attributes inherited from allOf parents (the nearest declaration wins)
+      self.class.acceptable_attribute_map.each_pair do |attr, param|
         value = self.send(attr)
         if value.nil?
-          is_nullable = self.class.openapi_nullable.include?(attr)
+          is_nullable = self.class.acceptable_openapi_nullable.include?(attr)
           next if !is_nullable || (is_nullable && !instance_variable_defined?(:"@#{attr}"))
         end
 
diff --git a/samples/client/petstore/ruby-httpx/lib/petstore/models/array_test.rb b/samples/client/petstore/ruby-httpx/lib/petstore/models/array_test.rb
index c74060151e07..fc5e9d297766 100644
--- a/samples/client/petstore/ruby-httpx/lib/petstore/models/array_test.rb
+++ b/samples/client/petstore/ruby-httpx/lib/petstore/models/array_test.rb
@@ -55,6 +55,16 @@ def self.openapi_nullable
       ])
     end
 
+    # Returns attribute type mapping
+    def self.acceptable_openapi_types
+      openapi_types
+    end
+
+    # Returns the nullable attributes
+    def self.acceptable_openapi_nullable
+      openapi_nullable
+    end
+
     # Initializes the object
     # @param [Hash] attributes Model attributes in the form of hash
     def initialize(attributes = {})
@@ -161,18 +171,20 @@ def hash
     def self.build_from_hash(attributes)
       return nil unless attributes.is_a?(Hash)
       attributes = attributes.transform_keys(&:to_sym)
+      # include attributes inherited from allOf parents (the nearest declaration wins)
+      map = acceptable_attribute_map
       transformed_hash = {}
-      openapi_types.each_pair do |key, type|
-        if attributes.key?(attribute_map[key]) && attributes[attribute_map[key]].nil?
+      acceptable_openapi_types.each_pair do |key, type|
+        if attributes.key?(map[key]) && attributes[map[key]].nil?
           transformed_hash["#{key}"] = nil
         elsif type =~ /\AArray<(.*)>/i
           # check to ensure the input is an array given that the attribute
           # is documented as an array but the input is not
-          if attributes[attribute_map[key]].is_a?(Array)
-            transformed_hash["#{key}"] = attributes[attribute_map[key]].map { |v| _deserialize($1, v) }
+          if attributes[map[key]].is_a?(Array)
+            transformed_hash["#{key}"] = attributes[map[key]].map { |v| _deserialize($1, v) }
           end
-        elsif !attributes[attribute_map[key]].nil?
-          transformed_hash["#{key}"] = _deserialize(type, attributes[attribute_map[key]])
+        elsif !attributes[map[key]].nil?
+          transformed_hash["#{key}"] = _deserialize(type, attributes[map[key]])
         end
       end
       new(transformed_hash)
@@ -182,10 +194,11 @@ def self.build_from_hash(attributes)
     # @return [Hash] Returns the object in the form of hash
     def to_hash
       hash = {}
-      self.class.attribute_map.each_pair do |attr, param|
+      # include attributes inherited from allOf parents (the nearest declaration wins)
+      self.class.acceptable_attribute_map.each_pair do |attr, param|
         value = self.send(attr)
         if value.nil?
-          is_nullable = self.class.openapi_nullable.include?(attr)
+          is_nullable = self.class.acceptable_openapi_nullable.include?(attr)
           next if !is_nullable || (is_nullable && !instance_variable_defined?(:"@#{attr}"))
         end
 
diff --git a/samples/client/petstore/ruby-httpx/lib/petstore/models/capitalization.rb b/samples/client/petstore/ruby-httpx/lib/petstore/models/capitalization.rb
index e0bbeb211eb3..9031ca3f7d51 100644
--- a/samples/client/petstore/ruby-httpx/lib/petstore/models/capitalization.rb
+++ b/samples/client/petstore/ruby-httpx/lib/petstore/models/capitalization.rb
@@ -68,6 +68,16 @@ def self.openapi_nullable
       ])
     end
 
+    # Returns attribute type mapping
+    def self.acceptable_openapi_types
+      openapi_types
+    end
+
+    # Returns the nullable attributes
+    def self.acceptable_openapi_nullable
+      openapi_nullable
+    end
+
     # Initializes the object
     # @param [Hash] attributes Model attributes in the form of hash
     def initialize(attributes = {})
@@ -155,18 +165,20 @@ def hash
     def self.build_from_hash(attributes)
       return nil unless attributes.is_a?(Hash)
       attributes = attributes.transform_keys(&:to_sym)
+      # include attributes inherited from allOf parents (the nearest declaration wins)
+      map = acceptable_attribute_map
       transformed_hash = {}
-      openapi_types.each_pair do |key, type|
-        if attributes.key?(attribute_map[key]) && attributes[attribute_map[key]].nil?
+      acceptable_openapi_types.each_pair do |key, type|
+        if attributes.key?(map[key]) && attributes[map[key]].nil?
           transformed_hash["#{key}"] = nil
         elsif type =~ /\AArray<(.*)>/i
           # check to ensure the input is an array given that the attribute
           # is documented as an array but the input is not
-          if attributes[attribute_map[key]].is_a?(Array)
-            transformed_hash["#{key}"] = attributes[attribute_map[key]].map { |v| _deserialize($1, v) }
+          if attributes[map[key]].is_a?(Array)
+            transformed_hash["#{key}"] = attributes[map[key]].map { |v| _deserialize($1, v) }
           end
-        elsif !attributes[attribute_map[key]].nil?
-          transformed_hash["#{key}"] = _deserialize(type, attributes[attribute_map[key]])
+        elsif !attributes[map[key]].nil?
+          transformed_hash["#{key}"] = _deserialize(type, attributes[map[key]])
         end
       end
       new(transformed_hash)
@@ -176,10 +188,11 @@ def self.build_from_hash(attributes)
     # @return [Hash] Returns the object in the form of hash
     def to_hash
       hash = {}
-      self.class.attribute_map.each_pair do |attr, param|
+      # include attributes inherited from allOf parents (the nearest declaration wins)
+      self.class.acceptable_attribute_map.each_pair do |attr, param|
         value = self.send(attr)
         if value.nil?
-          is_nullable = self.class.openapi_nullable.include?(attr)
+          is_nullable = self.class.acceptable_openapi_nullable.include?(attr)
           next if !is_nullable || (is_nullable && !instance_variable_defined?(:"@#{attr}"))
         end
 
diff --git a/samples/client/petstore/ruby-httpx/lib/petstore/models/cat.rb b/samples/client/petstore/ruby-httpx/lib/petstore/models/cat.rb
index a84dc5038bef..a1f3de5272b6 100644
--- a/samples/client/petstore/ruby-httpx/lib/petstore/models/cat.rb
+++ b/samples/client/petstore/ruby-httpx/lib/petstore/models/cat.rb
@@ -47,6 +47,16 @@ def self.openapi_nullable
       ])
     end
 
+    # Returns attribute type mapping, including the ones defined in its parent(s)
+    def self.acceptable_openapi_types
+      superclass.acceptable_openapi_types.merge(openapi_types)
+    end
+
+    # Returns the nullable attributes, including the ones defined in its parent(s) that it does not redeclare
+    def self.acceptable_openapi_nullable
+      (superclass.acceptable_openapi_nullable - attribute_map.keys) | openapi_nullable
+    end
+
     # List of class defined in allOf (OpenAPI v3)
     def self.openapi_all_of
       [
@@ -118,20 +128,21 @@ def hash
     # @return [Object] Returns the model itself
     def self.build_from_hash(attributes)
       return nil unless attributes.is_a?(Hash)
-      super(attributes)
       attributes = attributes.transform_keys(&:to_sym)
+      # include attributes inherited from allOf parents (the nearest declaration wins)
+      map = acceptable_attribute_map
       transformed_hash = {}
-      openapi_types.each_pair do |key, type|
-        if attributes.key?(attribute_map[key]) && attributes[attribute_map[key]].nil?
+      acceptable_openapi_types.each_pair do |key, type|
+        if attributes.key?(map[key]) && attributes[map[key]].nil?
           transformed_hash["#{key}"] = nil
         elsif type =~ /\AArray<(.*)>/i
           # check to ensure the input is an array given that the attribute
           # is documented as an array but the input is not
-          if attributes[attribute_map[key]].is_a?(Array)
-            transformed_hash["#{key}"] = attributes[attribute_map[key]].map { |v| _deserialize($1, v) }
+          if attributes[map[key]].is_a?(Array)
+            transformed_hash["#{key}"] = attributes[map[key]].map { |v| _deserialize($1, v) }
           end
-        elsif !attributes[attribute_map[key]].nil?
-          transformed_hash["#{key}"] = _deserialize(type, attributes[attribute_map[key]])
+        elsif !attributes[map[key]].nil?
+          transformed_hash["#{key}"] = _deserialize(type, attributes[map[key]])
         end
       end
       new(transformed_hash)
@@ -140,11 +151,12 @@ def self.build_from_hash(attributes)
     # Returns the object in the form of hash
     # @return [Hash] Returns the object in the form of hash
     def to_hash
-      hash = super
-      self.class.attribute_map.each_pair do |attr, param|
+      hash = {}
+      # include attributes inherited from allOf parents (the nearest declaration wins)
+      self.class.acceptable_attribute_map.each_pair do |attr, param|
         value = self.send(attr)
         if value.nil?
-          is_nullable = self.class.openapi_nullable.include?(attr)
+          is_nullable = self.class.acceptable_openapi_nullable.include?(attr)
           next if !is_nullable || (is_nullable && !instance_variable_defined?(:"@#{attr}"))
         end
 
diff --git a/samples/client/petstore/ruby-httpx/lib/petstore/models/category.rb b/samples/client/petstore/ruby-httpx/lib/petstore/models/category.rb
index 2f2b7f1a5785..a5af1c3f9acc 100644
--- a/samples/client/petstore/ruby-httpx/lib/petstore/models/category.rb
+++ b/samples/client/petstore/ruby-httpx/lib/petstore/models/category.rb
@@ -51,6 +51,16 @@ def self.openapi_nullable
       ])
     end
 
+    # Returns attribute type mapping
+    def self.acceptable_openapi_types
+      openapi_types
+    end
+
+    # Returns the nullable attributes
+    def self.acceptable_openapi_nullable
+      openapi_nullable
+    end
+
     # Initializes the object
     # @param [Hash] attributes Model attributes in the form of hash
     def initialize(attributes = {})
@@ -135,18 +145,20 @@ def hash
     def self.build_from_hash(attributes)
       return nil unless attributes.is_a?(Hash)
       attributes = attributes.transform_keys(&:to_sym)
+      # include attributes inherited from allOf parents (the nearest declaration wins)
+      map = acceptable_attribute_map
       transformed_hash = {}
-      openapi_types.each_pair do |key, type|
-        if attributes.key?(attribute_map[key]) && attributes[attribute_map[key]].nil?
+      acceptable_openapi_types.each_pair do |key, type|
+        if attributes.key?(map[key]) && attributes[map[key]].nil?
           transformed_hash["#{key}"] = nil
         elsif type =~ /\AArray<(.*)>/i
           # check to ensure the input is an array given that the attribute
           # is documented as an array but the input is not
-          if attributes[attribute_map[key]].is_a?(Array)
-            transformed_hash["#{key}"] = attributes[attribute_map[key]].map { |v| _deserialize($1, v) }
+          if attributes[map[key]].is_a?(Array)
+            transformed_hash["#{key}"] = attributes[map[key]].map { |v| _deserialize($1, v) }
           end
-        elsif !attributes[attribute_map[key]].nil?
-          transformed_hash["#{key}"] = _deserialize(type, attributes[attribute_map[key]])
+        elsif !attributes[map[key]].nil?
+          transformed_hash["#{key}"] = _deserialize(type, attributes[map[key]])
         end
       end
       new(transformed_hash)
@@ -156,10 +168,11 @@ def self.build_from_hash(attributes)
     # @return [Hash] Returns the object in the form of hash
     def to_hash
       hash = {}
-      self.class.attribute_map.each_pair do |attr, param|
+      # include attributes inherited from allOf parents (the nearest declaration wins)
+      self.class.acceptable_attribute_map.each_pair do |attr, param|
         value = self.send(attr)
         if value.nil?
-          is_nullable = self.class.openapi_nullable.include?(attr)
+          is_nullable = self.class.acceptable_openapi_nullable.include?(attr)
           next if !is_nullable || (is_nullable && !instance_variable_defined?(:"@#{attr}"))
         end
 
diff --git a/samples/client/petstore/ruby-httpx/lib/petstore/models/class_model.rb b/samples/client/petstore/ruby-httpx/lib/petstore/models/class_model.rb
index fafd11df773a..4e611ee27f3e 100644
--- a/samples/client/petstore/ruby-httpx/lib/petstore/models/class_model.rb
+++ b/samples/client/petstore/ruby-httpx/lib/petstore/models/class_model.rb
@@ -48,6 +48,16 @@ def self.openapi_nullable
       ])
     end
 
+    # Returns attribute type mapping
+    def self.acceptable_openapi_types
+      openapi_types
+    end
+
+    # Returns the nullable attributes
+    def self.acceptable_openapi_nullable
+      openapi_nullable
+    end
+
     # Initializes the object
     # @param [Hash] attributes Model attributes in the form of hash
     def initialize(attributes = {})
@@ -110,18 +120,20 @@ def hash
     def self.build_from_hash(attributes)
       return nil unless attributes.is_a?(Hash)
       attributes = attributes.transform_keys(&:to_sym)
+      # include attributes inherited from allOf parents (the nearest declaration wins)
+      map = acceptable_attribute_map
       transformed_hash = {}
-      openapi_types.each_pair do |key, type|
-        if attributes.key?(attribute_map[key]) && attributes[attribute_map[key]].nil?
+      acceptable_openapi_types.each_pair do |key, type|
+        if attributes.key?(map[key]) && attributes[map[key]].nil?
           transformed_hash["#{key}"] = nil
         elsif type =~ /\AArray<(.*)>/i
           # check to ensure the input is an array given that the attribute
           # is documented as an array but the input is not
-          if attributes[attribute_map[key]].is_a?(Array)
-            transformed_hash["#{key}"] = attributes[attribute_map[key]].map { |v| _deserialize($1, v) }
+          if attributes[map[key]].is_a?(Array)
+            transformed_hash["#{key}"] = attributes[map[key]].map { |v| _deserialize($1, v) }
           end
-        elsif !attributes[attribute_map[key]].nil?
-          transformed_hash["#{key}"] = _deserialize(type, attributes[attribute_map[key]])
+        elsif !attributes[map[key]].nil?
+          transformed_hash["#{key}"] = _deserialize(type, attributes[map[key]])
         end
       end
       new(transformed_hash)
@@ -131,10 +143,11 @@ def self.build_from_hash(attributes)
     # @return [Hash] Returns the object in the form of hash
     def to_hash
       hash = {}
-      self.class.attribute_map.each_pair do |attr, param|
+      # include attributes inherited from allOf parents (the nearest declaration wins)
+      self.class.acceptable_attribute_map.each_pair do |attr, param|
         value = self.send(attr)
         if value.nil?
-          is_nullable = self.class.openapi_nullable.include?(attr)
+          is_nullable = self.class.acceptable_openapi_nullable.include?(attr)
           next if !is_nullable || (is_nullable && !instance_variable_defined?(:"@#{attr}"))
         end
 
diff --git a/samples/client/petstore/ruby-httpx/lib/petstore/models/client.rb b/samples/client/petstore/ruby-httpx/lib/petstore/models/client.rb
index a349b7251d7b..f775d0f1d542 100644
--- a/samples/client/petstore/ruby-httpx/lib/petstore/models/client.rb
+++ b/samples/client/petstore/ruby-httpx/lib/petstore/models/client.rb
@@ -47,6 +47,16 @@ def self.openapi_nullable
       ])
     end
 
+    # Returns attribute type mapping
+    def self.acceptable_openapi_types
+      openapi_types
+    end
+
+    # Returns the nullable attributes
+    def self.acceptable_openapi_nullable
+      openapi_nullable
+    end
+
     # Initializes the object
     # @param [Hash] attributes Model attributes in the form of hash
     def initialize(attributes = {})
@@ -109,18 +119,20 @@ def hash
     def self.build_from_hash(attributes)
       return nil unless attributes.is_a?(Hash)
       attributes = attributes.transform_keys(&:to_sym)
+      # include attributes inherited from allOf parents (the nearest declaration wins)
+      map = acceptable_attribute_map
       transformed_hash = {}
-      openapi_types.each_pair do |key, type|
-        if attributes.key?(attribute_map[key]) && attributes[attribute_map[key]].nil?
+      acceptable_openapi_types.each_pair do |key, type|
+        if attributes.key?(map[key]) && attributes[map[key]].nil?
           transformed_hash["#{key}"] = nil
         elsif type =~ /\AArray<(.*)>/i
           # check to ensure the input is an array given that the attribute
           # is documented as an array but the input is not
-          if attributes[attribute_map[key]].is_a?(Array)
-            transformed_hash["#{key}"] = attributes[attribute_map[key]].map { |v| _deserialize($1, v) }
+          if attributes[map[key]].is_a?(Array)
+            transformed_hash["#{key}"] = attributes[map[key]].map { |v| _deserialize($1, v) }
           end
-        elsif !attributes[attribute_map[key]].nil?
-          transformed_hash["#{key}"] = _deserialize(type, attributes[attribute_map[key]])
+        elsif !attributes[map[key]].nil?
+          transformed_hash["#{key}"] = _deserialize(type, attributes[map[key]])
         end
       end
       new(transformed_hash)
@@ -130,10 +142,11 @@ def self.build_from_hash(attributes)
     # @return [Hash] Returns the object in the form of hash
     def to_hash
       hash = {}
-      self.class.attribute_map.each_pair do |attr, param|
+      # include attributes inherited from allOf parents (the nearest declaration wins)
+      self.class.acceptable_attribute_map.each_pair do |attr, param|
         value = self.send(attr)
         if value.nil?
-          is_nullable = self.class.openapi_nullable.include?(attr)
+          is_nullable = self.class.acceptable_openapi_nullable.include?(attr)
           next if !is_nullable || (is_nullable && !instance_variable_defined?(:"@#{attr}"))
         end
 
diff --git a/samples/client/petstore/ruby-httpx/lib/petstore/models/deprecated_object.rb b/samples/client/petstore/ruby-httpx/lib/petstore/models/deprecated_object.rb
index 9f1ee6720cab..bdc86013c848 100644
--- a/samples/client/petstore/ruby-httpx/lib/petstore/models/deprecated_object.rb
+++ b/samples/client/petstore/ruby-httpx/lib/petstore/models/deprecated_object.rb
@@ -47,6 +47,16 @@ def self.openapi_nullable
       ])
     end
 
+    # Returns attribute type mapping
+    def self.acceptable_openapi_types
+      openapi_types
+    end
+
+    # Returns the nullable attributes
+    def self.acceptable_openapi_nullable
+      openapi_nullable
+    end
+
     # Initializes the object
     # @param [Hash] attributes Model attributes in the form of hash
     def initialize(attributes = {})
@@ -109,18 +119,20 @@ def hash
     def self.build_from_hash(attributes)
       return nil unless attributes.is_a?(Hash)
       attributes = attributes.transform_keys(&:to_sym)
+      # include attributes inherited from allOf parents (the nearest declaration wins)
+      map = acceptable_attribute_map
       transformed_hash = {}
-      openapi_types.each_pair do |key, type|
-        if attributes.key?(attribute_map[key]) && attributes[attribute_map[key]].nil?
+      acceptable_openapi_types.each_pair do |key, type|
+        if attributes.key?(map[key]) && attributes[map[key]].nil?
           transformed_hash["#{key}"] = nil
         elsif type =~ /\AArray<(.*)>/i
           # check to ensure the input is an array given that the attribute
           # is documented as an array but the input is not
-          if attributes[attribute_map[key]].is_a?(Array)
-            transformed_hash["#{key}"] = attributes[attribute_map[key]].map { |v| _deserialize($1, v) }
+          if attributes[map[key]].is_a?(Array)
+            transformed_hash["#{key}"] = attributes[map[key]].map { |v| _deserialize($1, v) }
           end
-        elsif !attributes[attribute_map[key]].nil?
-          transformed_hash["#{key}"] = _deserialize(type, attributes[attribute_map[key]])
+        elsif !attributes[map[key]].nil?
+          transformed_hash["#{key}"] = _deserialize(type, attributes[map[key]])
         end
       end
       new(transformed_hash)
@@ -130,10 +142,11 @@ def self.build_from_hash(attributes)
     # @return [Hash] Returns the object in the form of hash
     def to_hash
       hash = {}
-      self.class.attribute_map.each_pair do |attr, param|
+      # include attributes inherited from allOf parents (the nearest declaration wins)
+      self.class.acceptable_attribute_map.each_pair do |attr, param|
         value = self.send(attr)
         if value.nil?
-          is_nullable = self.class.openapi_nullable.include?(attr)
+          is_nullable = self.class.acceptable_openapi_nullable.include?(attr)
           next if !is_nullable || (is_nullable && !instance_variable_defined?(:"@#{attr}"))
         end
 
diff --git a/samples/client/petstore/ruby-httpx/lib/petstore/models/dog.rb b/samples/client/petstore/ruby-httpx/lib/petstore/models/dog.rb
index 522e1a72f47e..2e8f95136f9a 100644
--- a/samples/client/petstore/ruby-httpx/lib/petstore/models/dog.rb
+++ b/samples/client/petstore/ruby-httpx/lib/petstore/models/dog.rb
@@ -47,6 +47,16 @@ def self.openapi_nullable
       ])
     end
 
+    # Returns attribute type mapping, including the ones defined in its parent(s)
+    def self.acceptable_openapi_types
+      superclass.acceptable_openapi_types.merge(openapi_types)
+    end
+
+    # Returns the nullable attributes, including the ones defined in its parent(s) that it does not redeclare
+    def self.acceptable_openapi_nullable
+      (superclass.acceptable_openapi_nullable - attribute_map.keys) | openapi_nullable
+    end
+
     # List of class defined in allOf (OpenAPI v3)
     def self.openapi_all_of
       [
@@ -118,20 +128,21 @@ def hash
     # @return [Object] Returns the model itself
     def self.build_from_hash(attributes)
       return nil unless attributes.is_a?(Hash)
-      super(attributes)
       attributes = attributes.transform_keys(&:to_sym)
+      # include attributes inherited from allOf parents (the nearest declaration wins)
+      map = acceptable_attribute_map
       transformed_hash = {}
-      openapi_types.each_pair do |key, type|
-        if attributes.key?(attribute_map[key]) && attributes[attribute_map[key]].nil?
+      acceptable_openapi_types.each_pair do |key, type|
+        if attributes.key?(map[key]) && attributes[map[key]].nil?
           transformed_hash["#{key}"] = nil
         elsif type =~ /\AArray<(.*)>/i
           # check to ensure the input is an array given that the attribute
           # is documented as an array but the input is not
-          if attributes[attribute_map[key]].is_a?(Array)
-            transformed_hash["#{key}"] = attributes[attribute_map[key]].map { |v| _deserialize($1, v) }
+          if attributes[map[key]].is_a?(Array)
+            transformed_hash["#{key}"] = attributes[map[key]].map { |v| _deserialize($1, v) }
           end
-        elsif !attributes[attribute_map[key]].nil?
-          transformed_hash["#{key}"] = _deserialize(type, attributes[attribute_map[key]])
+        elsif !attributes[map[key]].nil?
+          transformed_hash["#{key}"] = _deserialize(type, attributes[map[key]])
         end
       end
       new(transformed_hash)
@@ -140,11 +151,12 @@ def self.build_from_hash(attributes)
     # Returns the object in the form of hash
     # @return [Hash] Returns the object in the form of hash
     def to_hash
-      hash = super
-      self.class.attribute_map.each_pair do |attr, param|
+      hash = {}
+      # include attributes inherited from allOf parents (the nearest declaration wins)
+      self.class.acceptable_attribute_map.each_pair do |attr, param|
         value = self.send(attr)
         if value.nil?
-          is_nullable = self.class.openapi_nullable.include?(attr)
+          is_nullable = self.class.acceptable_openapi_nullable.include?(attr)
           next if !is_nullable || (is_nullable && !instance_variable_defined?(:"@#{attr}"))
         end
 
diff --git a/samples/client/petstore/ruby-httpx/lib/petstore/models/enum_arrays.rb b/samples/client/petstore/ruby-httpx/lib/petstore/models/enum_arrays.rb
index 1f7c48bf859b..8058a6ac60bb 100644
--- a/samples/client/petstore/ruby-httpx/lib/petstore/models/enum_arrays.rb
+++ b/samples/client/petstore/ruby-httpx/lib/petstore/models/enum_arrays.rb
@@ -73,6 +73,16 @@ def self.openapi_nullable
       ])
     end
 
+    # Returns attribute type mapping
+    def self.acceptable_openapi_types
+      openapi_types
+    end
+
+    # Returns the nullable attributes
+    def self.acceptable_openapi_nullable
+      openapi_nullable
+    end
+
     # Initializes the object
     # @param [Hash] attributes Model attributes in the form of hash
     def initialize(attributes = {})
@@ -154,18 +164,20 @@ def hash
     def self.build_from_hash(attributes)
       return nil unless attributes.is_a?(Hash)
       attributes = attributes.transform_keys(&:to_sym)
+      # include attributes inherited from allOf parents (the nearest declaration wins)
+      map = acceptable_attribute_map
       transformed_hash = {}
-      openapi_types.each_pair do |key, type|
-        if attributes.key?(attribute_map[key]) && attributes[attribute_map[key]].nil?
+      acceptable_openapi_types.each_pair do |key, type|
+        if attributes.key?(map[key]) && attributes[map[key]].nil?
           transformed_hash["#{key}"] = nil
         elsif type =~ /\AArray<(.*)>/i
           # check to ensure the input is an array given that the attribute
           # is documented as an array but the input is not
-          if attributes[attribute_map[key]].is_a?(Array)
-            transformed_hash["#{key}"] = attributes[attribute_map[key]].map { |v| _deserialize($1, v) }
+          if attributes[map[key]].is_a?(Array)
+            transformed_hash["#{key}"] = attributes[map[key]].map { |v| _deserialize($1, v) }
           end
-        elsif !attributes[attribute_map[key]].nil?
-          transformed_hash["#{key}"] = _deserialize(type, attributes[attribute_map[key]])
+        elsif !attributes[map[key]].nil?
+          transformed_hash["#{key}"] = _deserialize(type, attributes[map[key]])
         end
       end
       new(transformed_hash)
@@ -175,10 +187,11 @@ def self.build_from_hash(attributes)
     # @return [Hash] Returns the object in the form of hash
     def to_hash
       hash = {}
-      self.class.attribute_map.each_pair do |attr, param|
+      # include attributes inherited from allOf parents (the nearest declaration wins)
+      self.class.acceptable_attribute_map.each_pair do |attr, param|
         value = self.send(attr)
         if value.nil?
-          is_nullable = self.class.openapi_nullable.include?(attr)
+          is_nullable = self.class.acceptable_openapi_nullable.include?(attr)
           next if !is_nullable || (is_nullable && !instance_variable_defined?(:"@#{attr}"))
         end
 
diff --git a/samples/client/petstore/ruby-httpx/lib/petstore/models/enum_test.rb b/samples/client/petstore/ruby-httpx/lib/petstore/models/enum_test.rb
index 5159875cb89b..3b3905c138a3 100644
--- a/samples/client/petstore/ruby-httpx/lib/petstore/models/enum_test.rb
+++ b/samples/client/petstore/ruby-httpx/lib/petstore/models/enum_test.rb
@@ -98,6 +98,16 @@ def self.openapi_nullable
       ])
     end
 
+    # Returns attribute type mapping
+    def self.acceptable_openapi_types
+      openapi_types
+    end
+
+    # Returns the nullable attributes
+    def self.acceptable_openapi_nullable
+      openapi_nullable
+    end
+
     # Initializes the object
     # @param [Hash] attributes Model attributes in the form of hash
     def initialize(attributes = {})
@@ -254,18 +264,20 @@ def hash
     def self.build_from_hash(attributes)
       return nil unless attributes.is_a?(Hash)
       attributes = attributes.transform_keys(&:to_sym)
+      # include attributes inherited from allOf parents (the nearest declaration wins)
+      map = acceptable_attribute_map
       transformed_hash = {}
-      openapi_types.each_pair do |key, type|
-        if attributes.key?(attribute_map[key]) && attributes[attribute_map[key]].nil?
+      acceptable_openapi_types.each_pair do |key, type|
+        if attributes.key?(map[key]) && attributes[map[key]].nil?
           transformed_hash["#{key}"] = nil
         elsif type =~ /\AArray<(.*)>/i
           # check to ensure the input is an array given that the attribute
           # is documented as an array but the input is not
-          if attributes[attribute_map[key]].is_a?(Array)
-            transformed_hash["#{key}"] = attributes[attribute_map[key]].map { |v| _deserialize($1, v) }
+          if attributes[map[key]].is_a?(Array)
+            transformed_hash["#{key}"] = attributes[map[key]].map { |v| _deserialize($1, v) }
           end
-        elsif !attributes[attribute_map[key]].nil?
-          transformed_hash["#{key}"] = _deserialize(type, attributes[attribute_map[key]])
+        elsif !attributes[map[key]].nil?
+          transformed_hash["#{key}"] = _deserialize(type, attributes[map[key]])
         end
       end
       new(transformed_hash)
@@ -275,10 +287,11 @@ def self.build_from_hash(attributes)
     # @return [Hash] Returns the object in the form of hash
     def to_hash
       hash = {}
-      self.class.attribute_map.each_pair do |attr, param|
+      # include attributes inherited from allOf parents (the nearest declaration wins)
+      self.class.acceptable_attribute_map.each_pair do |attr, param|
         value = self.send(attr)
         if value.nil?
-          is_nullable = self.class.openapi_nullable.include?(attr)
+          is_nullable = self.class.acceptable_openapi_nullable.include?(attr)
           next if !is_nullable || (is_nullable && !instance_variable_defined?(:"@#{attr}"))
         end
 
diff --git a/samples/client/petstore/ruby-httpx/lib/petstore/models/fake_big_decimal_map200_response.rb b/samples/client/petstore/ruby-httpx/lib/petstore/models/fake_big_decimal_map200_response.rb
index 6d5e47b59656..b7be6af6d90e 100644
--- a/samples/client/petstore/ruby-httpx/lib/petstore/models/fake_big_decimal_map200_response.rb
+++ b/samples/client/petstore/ruby-httpx/lib/petstore/models/fake_big_decimal_map200_response.rb
@@ -51,6 +51,16 @@ def self.openapi_nullable
       ])
     end
 
+    # Returns attribute type mapping
+    def self.acceptable_openapi_types
+      openapi_types
+    end
+
+    # Returns the nullable attributes
+    def self.acceptable_openapi_nullable
+      openapi_nullable
+    end
+
     # Initializes the object
     # @param [Hash] attributes Model attributes in the form of hash
     def initialize(attributes = {})
@@ -120,18 +130,20 @@ def hash
     def self.build_from_hash(attributes)
       return nil unless attributes.is_a?(Hash)
       attributes = attributes.transform_keys(&:to_sym)
+      # include attributes inherited from allOf parents (the nearest declaration wins)
+      map = acceptable_attribute_map
       transformed_hash = {}
-      openapi_types.each_pair do |key, type|
-        if attributes.key?(attribute_map[key]) && attributes[attribute_map[key]].nil?
+      acceptable_openapi_types.each_pair do |key, type|
+        if attributes.key?(map[key]) && attributes[map[key]].nil?
           transformed_hash["#{key}"] = nil
         elsif type =~ /\AArray<(.*)>/i
           # check to ensure the input is an array given that the attribute
           # is documented as an array but the input is not
-          if attributes[attribute_map[key]].is_a?(Array)
-            transformed_hash["#{key}"] = attributes[attribute_map[key]].map { |v| _deserialize($1, v) }
+          if attributes[map[key]].is_a?(Array)
+            transformed_hash["#{key}"] = attributes[map[key]].map { |v| _deserialize($1, v) }
           end
-        elsif !attributes[attribute_map[key]].nil?
-          transformed_hash["#{key}"] = _deserialize(type, attributes[attribute_map[key]])
+        elsif !attributes[map[key]].nil?
+          transformed_hash["#{key}"] = _deserialize(type, attributes[map[key]])
         end
       end
       new(transformed_hash)
@@ -141,10 +153,11 @@ def self.build_from_hash(attributes)
     # @return [Hash] Returns the object in the form of hash
     def to_hash
       hash = {}
-      self.class.attribute_map.each_pair do |attr, param|
+      # include attributes inherited from allOf parents (the nearest declaration wins)
+      self.class.acceptable_attribute_map.each_pair do |attr, param|
         value = self.send(attr)
         if value.nil?
-          is_nullable = self.class.openapi_nullable.include?(attr)
+          is_nullable = self.class.acceptable_openapi_nullable.include?(attr)
           next if !is_nullable || (is_nullable && !instance_variable_defined?(:"@#{attr}"))
         end
 
diff --git a/samples/client/petstore/ruby-httpx/lib/petstore/models/file.rb b/samples/client/petstore/ruby-httpx/lib/petstore/models/file.rb
index 219237eb3c07..4fac9978fcaa 100644
--- a/samples/client/petstore/ruby-httpx/lib/petstore/models/file.rb
+++ b/samples/client/petstore/ruby-httpx/lib/petstore/models/file.rb
@@ -49,6 +49,16 @@ def self.openapi_nullable
       ])
     end
 
+    # Returns attribute type mapping
+    def self.acceptable_openapi_types
+      openapi_types
+    end
+
+    # Returns the nullable attributes
+    def self.acceptable_openapi_nullable
+      openapi_nullable
+    end
+
     # Initializes the object
     # @param [Hash] attributes Model attributes in the form of hash
     def initialize(attributes = {})
@@ -111,18 +121,20 @@ def hash
     def self.build_from_hash(attributes)
       return nil unless attributes.is_a?(Hash)
       attributes = attributes.transform_keys(&:to_sym)
+      # include attributes inherited from allOf parents (the nearest declaration wins)
+      map = acceptable_attribute_map
       transformed_hash = {}
-      openapi_types.each_pair do |key, type|
-        if attributes.key?(attribute_map[key]) && attributes[attribute_map[key]].nil?
+      acceptable_openapi_types.each_pair do |key, type|
+        if attributes.key?(map[key]) && attributes[map[key]].nil?
           transformed_hash["#{key}"] = nil
         elsif type =~ /\AArray<(.*)>/i
           # check to ensure the input is an array given that the attribute
           # is documented as an array but the input is not
-          if attributes[attribute_map[key]].is_a?(Array)
-            transformed_hash["#{key}"] = attributes[attribute_map[key]].map { |v| _deserialize($1, v) }
+          if attributes[map[key]].is_a?(Array)
+            transformed_hash["#{key}"] = attributes[map[key]].map { |v| _deserialize($1, v) }
           end
-        elsif !attributes[attribute_map[key]].nil?
-          transformed_hash["#{key}"] = _deserialize(type, attributes[attribute_map[key]])
+        elsif !attributes[map[key]].nil?
+          transformed_hash["#{key}"] = _deserialize(type, attributes[map[key]])
         end
       end
       new(transformed_hash)
@@ -132,10 +144,11 @@ def self.build_from_hash(attributes)
     # @return [Hash] Returns the object in the form of hash
     def to_hash
       hash = {}
-      self.class.attribute_map.each_pair do |attr, param|
+      # include attributes inherited from allOf parents (the nearest declaration wins)
+      self.class.acceptable_attribute_map.each_pair do |attr, param|
         value = self.send(attr)
         if value.nil?
-          is_nullable = self.class.openapi_nullable.include?(attr)
+          is_nullable = self.class.acceptable_openapi_nullable.include?(attr)
           next if !is_nullable || (is_nullable && !instance_variable_defined?(:"@#{attr}"))
         end
 
diff --git a/samples/client/petstore/ruby-httpx/lib/petstore/models/file_schema_test_class.rb b/samples/client/petstore/ruby-httpx/lib/petstore/models/file_schema_test_class.rb
index 8fdab5a25e86..074c235ebe17 100644
--- a/samples/client/petstore/ruby-httpx/lib/petstore/models/file_schema_test_class.rb
+++ b/samples/client/petstore/ruby-httpx/lib/petstore/models/file_schema_test_class.rb
@@ -51,6 +51,16 @@ def self.openapi_nullable
       ])
     end
 
+    # Returns attribute type mapping
+    def self.acceptable_openapi_types
+      openapi_types
+    end
+
+    # Returns the nullable attributes
+    def self.acceptable_openapi_nullable
+      openapi_nullable
+    end
+
     # Initializes the object
     # @param [Hash] attributes Model attributes in the form of hash
     def initialize(attributes = {})
@@ -120,18 +130,20 @@ def hash
     def self.build_from_hash(attributes)
       return nil unless attributes.is_a?(Hash)
       attributes = attributes.transform_keys(&:to_sym)
+      # include attributes inherited from allOf parents (the nearest declaration wins)
+      map = acceptable_attribute_map
       transformed_hash = {}
-      openapi_types.each_pair do |key, type|
-        if attributes.key?(attribute_map[key]) && attributes[attribute_map[key]].nil?
+      acceptable_openapi_types.each_pair do |key, type|
+        if attributes.key?(map[key]) && attributes[map[key]].nil?
           transformed_hash["#{key}"] = nil
         elsif type =~ /\AArray<(.*)>/i
           # check to ensure the input is an array given that the attribute
           # is documented as an array but the input is not
-          if attributes[attribute_map[key]].is_a?(Array)
-            transformed_hash["#{key}"] = attributes[attribute_map[key]].map { |v| _deserialize($1, v) }
+          if attributes[map[key]].is_a?(Array)
+            transformed_hash["#{key}"] = attributes[map[key]].map { |v| _deserialize($1, v) }
           end
-        elsif !attributes[attribute_map[key]].nil?
-          transformed_hash["#{key}"] = _deserialize(type, attributes[attribute_map[key]])
+        elsif !attributes[map[key]].nil?
+          transformed_hash["#{key}"] = _deserialize(type, attributes[map[key]])
         end
       end
       new(transformed_hash)
@@ -141,10 +153,11 @@ def self.build_from_hash(attributes)
     # @return [Hash] Returns the object in the form of hash
     def to_hash
       hash = {}
-      self.class.attribute_map.each_pair do |attr, param|
+      # include attributes inherited from allOf parents (the nearest declaration wins)
+      self.class.acceptable_attribute_map.each_pair do |attr, param|
         value = self.send(attr)
         if value.nil?
-          is_nullable = self.class.openapi_nullable.include?(attr)
+          is_nullable = self.class.acceptable_openapi_nullable.include?(attr)
           next if !is_nullable || (is_nullable && !instance_variable_defined?(:"@#{attr}"))
         end
 
diff --git a/samples/client/petstore/ruby-httpx/lib/petstore/models/foo.rb b/samples/client/petstore/ruby-httpx/lib/petstore/models/foo.rb
index ceb5b7497955..811726434b54 100644
--- a/samples/client/petstore/ruby-httpx/lib/petstore/models/foo.rb
+++ b/samples/client/petstore/ruby-httpx/lib/petstore/models/foo.rb
@@ -47,6 +47,16 @@ def self.openapi_nullable
       ])
     end
 
+    # Returns attribute type mapping
+    def self.acceptable_openapi_types
+      openapi_types
+    end
+
+    # Returns the nullable attributes
+    def self.acceptable_openapi_nullable
+      openapi_nullable
+    end
+
     # Initializes the object
     # @param [Hash] attributes Model attributes in the form of hash
     def initialize(attributes = {})
@@ -111,18 +121,20 @@ def hash
     def self.build_from_hash(attributes)
       return nil unless attributes.is_a?(Hash)
       attributes = attributes.transform_keys(&:to_sym)
+      # include attributes inherited from allOf parents (the nearest declaration wins)
+      map = acceptable_attribute_map
       transformed_hash = {}
-      openapi_types.each_pair do |key, type|
-        if attributes.key?(attribute_map[key]) && attributes[attribute_map[key]].nil?
+      acceptable_openapi_types.each_pair do |key, type|
+        if attributes.key?(map[key]) && attributes[map[key]].nil?
           transformed_hash["#{key}"] = nil
         elsif type =~ /\AArray<(.*)>/i
           # check to ensure the input is an array given that the attribute
           # is documented as an array but the input is not
-          if attributes[attribute_map[key]].is_a?(Array)
-            transformed_hash["#{key}"] = attributes[attribute_map[key]].map { |v| _deserialize($1, v) }
+          if attributes[map[key]].is_a?(Array)
+            transformed_hash["#{key}"] = attributes[map[key]].map { |v| _deserialize($1, v) }
           end
-        elsif !attributes[attribute_map[key]].nil?
-          transformed_hash["#{key}"] = _deserialize(type, attributes[attribute_map[key]])
+        elsif !attributes[map[key]].nil?
+          transformed_hash["#{key}"] = _deserialize(type, attributes[map[key]])
         end
       end
       new(transformed_hash)
@@ -132,10 +144,11 @@ def self.build_from_hash(attributes)
     # @return [Hash] Returns the object in the form of hash
     def to_hash
       hash = {}
-      self.class.attribute_map.each_pair do |attr, param|
+      # include attributes inherited from allOf parents (the nearest declaration wins)
+      self.class.acceptable_attribute_map.each_pair do |attr, param|
         value = self.send(attr)
         if value.nil?
-          is_nullable = self.class.openapi_nullable.include?(attr)
+          is_nullable = self.class.acceptable_openapi_nullable.include?(attr)
           next if !is_nullable || (is_nullable && !instance_variable_defined?(:"@#{attr}"))
         end
 
diff --git a/samples/client/petstore/ruby-httpx/lib/petstore/models/foo_get_default_response.rb b/samples/client/petstore/ruby-httpx/lib/petstore/models/foo_get_default_response.rb
index 42538a14e2cb..61d044ad8f26 100644
--- a/samples/client/petstore/ruby-httpx/lib/petstore/models/foo_get_default_response.rb
+++ b/samples/client/petstore/ruby-httpx/lib/petstore/models/foo_get_default_response.rb
@@ -47,6 +47,16 @@ def self.openapi_nullable
       ])
     end
 
+    # Returns attribute type mapping
+    def self.acceptable_openapi_types
+      openapi_types
+    end
+
+    # Returns the nullable attributes
+    def self.acceptable_openapi_nullable
+      openapi_nullable
+    end
+
     # Initializes the object
     # @param [Hash] attributes Model attributes in the form of hash
     def initialize(attributes = {})
@@ -109,18 +119,20 @@ def hash
     def self.build_from_hash(attributes)
       return nil unless attributes.is_a?(Hash)
       attributes = attributes.transform_keys(&:to_sym)
+      # include attributes inherited from allOf parents (the nearest declaration wins)
+      map = acceptable_attribute_map
       transformed_hash = {}
-      openapi_types.each_pair do |key, type|
-        if attributes.key?(attribute_map[key]) && attributes[attribute_map[key]].nil?
+      acceptable_openapi_types.each_pair do |key, type|
+        if attributes.key?(map[key]) && attributes[map[key]].nil?
           transformed_hash["#{key}"] = nil
         elsif type =~ /\AArray<(.*)>/i
           # check to ensure the input is an array given that the attribute
           # is documented as an array but the input is not
-          if attributes[attribute_map[key]].is_a?(Array)
-            transformed_hash["#{key}"] = attributes[attribute_map[key]].map { |v| _deserialize($1, v) }
+          if attributes[map[key]].is_a?(Array)
+            transformed_hash["#{key}"] = attributes[map[key]].map { |v| _deserialize($1, v) }
           end
-        elsif !attributes[attribute_map[key]].nil?
-          transformed_hash["#{key}"] = _deserialize(type, attributes[attribute_map[key]])
+        elsif !attributes[map[key]].nil?
+          transformed_hash["#{key}"] = _deserialize(type, attributes[map[key]])
         end
       end
       new(transformed_hash)
@@ -130,10 +142,11 @@ def self.build_from_hash(attributes)
     # @return [Hash] Returns the object in the form of hash
     def to_hash
       hash = {}
-      self.class.attribute_map.each_pair do |attr, param|
+      # include attributes inherited from allOf parents (the nearest declaration wins)
+      self.class.acceptable_attribute_map.each_pair do |attr, param|
         value = self.send(attr)
         if value.nil?
-          is_nullable = self.class.openapi_nullable.include?(attr)
+          is_nullable = self.class.acceptable_openapi_nullable.include?(attr)
           next if !is_nullable || (is_nullable && !instance_variable_defined?(:"@#{attr}"))
         end
 
diff --git a/samples/client/petstore/ruby-httpx/lib/petstore/models/format_test.rb b/samples/client/petstore/ruby-httpx/lib/petstore/models/format_test.rb
index 03a4e130a8f9..6760f6807c59 100644
--- a/samples/client/petstore/ruby-httpx/lib/petstore/models/format_test.rb
+++ b/samples/client/petstore/ruby-httpx/lib/petstore/models/format_test.rb
@@ -109,6 +109,16 @@ def self.openapi_nullable
       ])
     end
 
+    # Returns attribute type mapping
+    def self.acceptable_openapi_types
+      openapi_types
+    end
+
+    # Returns the nullable attributes
+    def self.acceptable_openapi_nullable
+      openapi_nullable
+    end
+
     # Initializes the object
     # @param [Hash] attributes Model attributes in the form of hash
     def initialize(attributes = {})
@@ -525,18 +535,20 @@ def hash
     def self.build_from_hash(attributes)
       return nil unless attributes.is_a?(Hash)
       attributes = attributes.transform_keys(&:to_sym)
+      # include attributes inherited from allOf parents (the nearest declaration wins)
+      map = acceptable_attribute_map
       transformed_hash = {}
-      openapi_types.each_pair do |key, type|
-        if attributes.key?(attribute_map[key]) && attributes[attribute_map[key]].nil?
+      acceptable_openapi_types.each_pair do |key, type|
+        if attributes.key?(map[key]) && attributes[map[key]].nil?
           transformed_hash["#{key}"] = nil
         elsif type =~ /\AArray<(.*)>/i
           # check to ensure the input is an array given that the attribute
           # is documented as an array but the input is not
-          if attributes[attribute_map[key]].is_a?(Array)
-            transformed_hash["#{key}"] = attributes[attribute_map[key]].map { |v| _deserialize($1, v) }
+          if attributes[map[key]].is_a?(Array)
+            transformed_hash["#{key}"] = attributes[map[key]].map { |v| _deserialize($1, v) }
           end
-        elsif !attributes[attribute_map[key]].nil?
-          transformed_hash["#{key}"] = _deserialize(type, attributes[attribute_map[key]])
+        elsif !attributes[map[key]].nil?
+          transformed_hash["#{key}"] = _deserialize(type, attributes[map[key]])
         end
       end
       new(transformed_hash)
@@ -546,10 +558,11 @@ def self.build_from_hash(attributes)
     # @return [Hash] Returns the object in the form of hash
     def to_hash
       hash = {}
-      self.class.attribute_map.each_pair do |attr, param|
+      # include attributes inherited from allOf parents (the nearest declaration wins)
+      self.class.acceptable_attribute_map.each_pair do |attr, param|
         value = self.send(attr)
         if value.nil?
-          is_nullable = self.class.openapi_nullable.include?(attr)
+          is_nullable = self.class.acceptable_openapi_nullable.include?(attr)
           next if !is_nullable || (is_nullable && !instance_variable_defined?(:"@#{attr}"))
         end
 
diff --git a/samples/client/petstore/ruby-httpx/lib/petstore/models/has_only_read_only.rb b/samples/client/petstore/ruby-httpx/lib/petstore/models/has_only_read_only.rb
index cc584c09e54f..604a3da147bd 100644
--- a/samples/client/petstore/ruby-httpx/lib/petstore/models/has_only_read_only.rb
+++ b/samples/client/petstore/ruby-httpx/lib/petstore/models/has_only_read_only.rb
@@ -51,6 +51,16 @@ def self.openapi_nullable
       ])
     end
 
+    # Returns attribute type mapping
+    def self.acceptable_openapi_types
+      openapi_types
+    end
+
+    # Returns the nullable attributes
+    def self.acceptable_openapi_nullable
+      openapi_nullable
+    end
+
     # Initializes the object
     # @param [Hash] attributes Model attributes in the form of hash
     def initialize(attributes = {})
@@ -118,18 +128,20 @@ def hash
     def self.build_from_hash(attributes)
       return nil unless attributes.is_a?(Hash)
       attributes = attributes.transform_keys(&:to_sym)
+      # include attributes inherited from allOf parents (the nearest declaration wins)
+      map = acceptable_attribute_map
       transformed_hash = {}
-      openapi_types.each_pair do |key, type|
-        if attributes.key?(attribute_map[key]) && attributes[attribute_map[key]].nil?
+      acceptable_openapi_types.each_pair do |key, type|
+        if attributes.key?(map[key]) && attributes[map[key]].nil?
           transformed_hash["#{key}"] = nil
         elsif type =~ /\AArray<(.*)>/i
           # check to ensure the input is an array given that the attribute
           # is documented as an array but the input is not
-          if attributes[attribute_map[key]].is_a?(Array)
-            transformed_hash["#{key}"] = attributes[attribute_map[key]].map { |v| _deserialize($1, v) }
+          if attributes[map[key]].is_a?(Array)
+            transformed_hash["#{key}"] = attributes[map[key]].map { |v| _deserialize($1, v) }
           end
-        elsif !attributes[attribute_map[key]].nil?
-          transformed_hash["#{key}"] = _deserialize(type, attributes[attribute_map[key]])
+        elsif !attributes[map[key]].nil?
+          transformed_hash["#{key}"] = _deserialize(type, attributes[map[key]])
         end
       end
       new(transformed_hash)
@@ -139,10 +151,11 @@ def self.build_from_hash(attributes)
     # @return [Hash] Returns the object in the form of hash
     def to_hash
       hash = {}
-      self.class.attribute_map.each_pair do |attr, param|
+      # include attributes inherited from allOf parents (the nearest declaration wins)
+      self.class.acceptable_attribute_map.each_pair do |attr, param|
         value = self.send(attr)
         if value.nil?
-          is_nullable = self.class.openapi_nullable.include?(attr)
+          is_nullable = self.class.acceptable_openapi_nullable.include?(attr)
           next if !is_nullable || (is_nullable && !instance_variable_defined?(:"@#{attr}"))
         end
 
diff --git a/samples/client/petstore/ruby-httpx/lib/petstore/models/health_check_result.rb b/samples/client/petstore/ruby-httpx/lib/petstore/models/health_check_result.rb
index a66e1b71331d..0792044db072 100644
--- a/samples/client/petstore/ruby-httpx/lib/petstore/models/health_check_result.rb
+++ b/samples/client/petstore/ruby-httpx/lib/petstore/models/health_check_result.rb
@@ -49,6 +49,16 @@ def self.openapi_nullable
       ])
     end
 
+    # Returns attribute type mapping
+    def self.acceptable_openapi_types
+      openapi_types
+    end
+
+    # Returns the nullable attributes
+    def self.acceptable_openapi_nullable
+      openapi_nullable
+    end
+
     # Initializes the object
     # @param [Hash] attributes Model attributes in the form of hash
     def initialize(attributes = {})
@@ -111,18 +121,20 @@ def hash
     def self.build_from_hash(attributes)
       return nil unless attributes.is_a?(Hash)
       attributes = attributes.transform_keys(&:to_sym)
+      # include attributes inherited from allOf parents (the nearest declaration wins)
+      map = acceptable_attribute_map
       transformed_hash = {}
-      openapi_types.each_pair do |key, type|
-        if attributes.key?(attribute_map[key]) && attributes[attribute_map[key]].nil?
+      acceptable_openapi_types.each_pair do |key, type|
+        if attributes.key?(map[key]) && attributes[map[key]].nil?
           transformed_hash["#{key}"] = nil
         elsif type =~ /\AArray<(.*)>/i
           # check to ensure the input is an array given that the attribute
           # is documented as an array but the input is not
-          if attributes[attribute_map[key]].is_a?(Array)
-            transformed_hash["#{key}"] = attributes[attribute_map[key]].map { |v| _deserialize($1, v) }
+          if attributes[map[key]].is_a?(Array)
+            transformed_hash["#{key}"] = attributes[map[key]].map { |v| _deserialize($1, v) }
           end
-        elsif !attributes[attribute_map[key]].nil?
-          transformed_hash["#{key}"] = _deserialize(type, attributes[attribute_map[key]])
+        elsif !attributes[map[key]].nil?
+          transformed_hash["#{key}"] = _deserialize(type, attributes[map[key]])
         end
       end
       new(transformed_hash)
@@ -132,10 +144,11 @@ def self.build_from_hash(attributes)
     # @return [Hash] Returns the object in the form of hash
     def to_hash
       hash = {}
-      self.class.attribute_map.each_pair do |attr, param|
+      # include attributes inherited from allOf parents (the nearest declaration wins)
+      self.class.acceptable_attribute_map.each_pair do |attr, param|
         value = self.send(attr)
         if value.nil?
-          is_nullable = self.class.openapi_nullable.include?(attr)
+          is_nullable = self.class.acceptable_openapi_nullable.include?(attr)
           next if !is_nullable || (is_nullable && !instance_variable_defined?(:"@#{attr}"))
         end
 
diff --git a/samples/client/petstore/ruby-httpx/lib/petstore/models/list.rb b/samples/client/petstore/ruby-httpx/lib/petstore/models/list.rb
index 2dc658065278..ecc8eb8aafc5 100644
--- a/samples/client/petstore/ruby-httpx/lib/petstore/models/list.rb
+++ b/samples/client/petstore/ruby-httpx/lib/petstore/models/list.rb
@@ -47,6 +47,16 @@ def self.openapi_nullable
       ])
     end
 
+    # Returns attribute type mapping
+    def self.acceptable_openapi_types
+      openapi_types
+    end
+
+    # Returns the nullable attributes
+    def self.acceptable_openapi_nullable
+      openapi_nullable
+    end
+
     # Initializes the object
     # @param [Hash] attributes Model attributes in the form of hash
     def initialize(attributes = {})
@@ -109,18 +119,20 @@ def hash
     def self.build_from_hash(attributes)
       return nil unless attributes.is_a?(Hash)
       attributes = attributes.transform_keys(&:to_sym)
+      # include attributes inherited from allOf parents (the nearest declaration wins)
+      map = acceptable_attribute_map
       transformed_hash = {}
-      openapi_types.each_pair do |key, type|
-        if attributes.key?(attribute_map[key]) && attributes[attribute_map[key]].nil?
+      acceptable_openapi_types.each_pair do |key, type|
+        if attributes.key?(map[key]) && attributes[map[key]].nil?
           transformed_hash["#{key}"] = nil
         elsif type =~ /\AArray<(.*)>/i
           # check to ensure the input is an array given that the attribute
           # is documented as an array but the input is not
-          if attributes[attribute_map[key]].is_a?(Array)
-            transformed_hash["#{key}"] = attributes[attribute_map[key]].map { |v| _deserialize($1, v) }
+          if attributes[map[key]].is_a?(Array)
+            transformed_hash["#{key}"] = attributes[map[key]].map { |v| _deserialize($1, v) }
           end
-        elsif !attributes[attribute_map[key]].nil?
-          transformed_hash["#{key}"] = _deserialize(type, attributes[attribute_map[key]])
+        elsif !attributes[map[key]].nil?
+          transformed_hash["#{key}"] = _deserialize(type, attributes[map[key]])
         end
       end
       new(transformed_hash)
@@ -130,10 +142,11 @@ def self.build_from_hash(attributes)
     # @return [Hash] Returns the object in the form of hash
     def to_hash
       hash = {}
-      self.class.attribute_map.each_pair do |attr, param|
+      # include attributes inherited from allOf parents (the nearest declaration wins)
+      self.class.acceptable_attribute_map.each_pair do |attr, param|
         value = self.send(attr)
         if value.nil?
-          is_nullable = self.class.openapi_nullable.include?(attr)
+          is_nullable = self.class.acceptable_openapi_nullable.include?(attr)
           next if !is_nullable || (is_nullable && !instance_variable_defined?(:"@#{attr}"))
         end
 
diff --git a/samples/client/petstore/ruby-httpx/lib/petstore/models/map_test.rb b/samples/client/petstore/ruby-httpx/lib/petstore/models/map_test.rb
index 78c5472f24ae..eca01649a52a 100644
--- a/samples/client/petstore/ruby-httpx/lib/petstore/models/map_test.rb
+++ b/samples/client/petstore/ruby-httpx/lib/petstore/models/map_test.rb
@@ -81,6 +81,16 @@ def self.openapi_nullable
       ])
     end
 
+    # Returns attribute type mapping
+    def self.acceptable_openapi_types
+      openapi_types
+    end
+
+    # Returns the nullable attributes
+    def self.acceptable_openapi_nullable
+      openapi_nullable
+    end
+
     # Initializes the object
     # @param [Hash] attributes Model attributes in the form of hash
     def initialize(attributes = {})
@@ -166,18 +176,20 @@ def hash
     def self.build_from_hash(attributes)
       return nil unless attributes.is_a?(Hash)
       attributes = attributes.transform_keys(&:to_sym)
+      # include attributes inherited from allOf parents (the nearest declaration wins)
+      map = acceptable_attribute_map
       transformed_hash = {}
-      openapi_types.each_pair do |key, type|
-        if attributes.key?(attribute_map[key]) && attributes[attribute_map[key]].nil?
+      acceptable_openapi_types.each_pair do |key, type|
+        if attributes.key?(map[key]) && attributes[map[key]].nil?
           transformed_hash["#{key}"] = nil
         elsif type =~ /\AArray<(.*)>/i
           # check to ensure the input is an array given that the attribute
           # is documented as an array but the input is not
-          if attributes[attribute_map[key]].is_a?(Array)
-            transformed_hash["#{key}"] = attributes[attribute_map[key]].map { |v| _deserialize($1, v) }
+          if attributes[map[key]].is_a?(Array)
+            transformed_hash["#{key}"] = attributes[map[key]].map { |v| _deserialize($1, v) }
           end
-        elsif !attributes[attribute_map[key]].nil?
-          transformed_hash["#{key}"] = _deserialize(type, attributes[attribute_map[key]])
+        elsif !attributes[map[key]].nil?
+          transformed_hash["#{key}"] = _deserialize(type, attributes[map[key]])
         end
       end
       new(transformed_hash)
@@ -187,10 +199,11 @@ def self.build_from_hash(attributes)
     # @return [Hash] Returns the object in the form of hash
     def to_hash
       hash = {}
-      self.class.attribute_map.each_pair do |attr, param|
+      # include attributes inherited from allOf parents (the nearest declaration wins)
+      self.class.acceptable_attribute_map.each_pair do |attr, param|
         value = self.send(attr)
         if value.nil?
-          is_nullable = self.class.openapi_nullable.include?(attr)
+          is_nullable = self.class.acceptable_openapi_nullable.include?(attr)
           next if !is_nullable || (is_nullable && !instance_variable_defined?(:"@#{attr}"))
         end
 
diff --git a/samples/client/petstore/ruby-httpx/lib/petstore/models/mixed_properties_and_additional_properties_class.rb b/samples/client/petstore/ruby-httpx/lib/petstore/models/mixed_properties_and_additional_properties_class.rb
index bf1d3768951b..060c8488652f 100644
--- a/samples/client/petstore/ruby-httpx/lib/petstore/models/mixed_properties_and_additional_properties_class.rb
+++ b/samples/client/petstore/ruby-httpx/lib/petstore/models/mixed_properties_and_additional_properties_class.rb
@@ -55,6 +55,16 @@ def self.openapi_nullable
       ])
     end
 
+    # Returns attribute type mapping
+    def self.acceptable_openapi_types
+      openapi_types
+    end
+
+    # Returns the nullable attributes
+    def self.acceptable_openapi_nullable
+      openapi_nullable
+    end
+
     # Initializes the object
     # @param [Hash] attributes Model attributes in the form of hash
     def initialize(attributes = {})
@@ -129,18 +139,20 @@ def hash
     def self.build_from_hash(attributes)
       return nil unless attributes.is_a?(Hash)
       attributes = attributes.transform_keys(&:to_sym)
+      # include attributes inherited from allOf parents (the nearest declaration wins)
+      map = acceptable_attribute_map
       transformed_hash = {}
-      openapi_types.each_pair do |key, type|
-        if attributes.key?(attribute_map[key]) && attributes[attribute_map[key]].nil?
+      acceptable_openapi_types.each_pair do |key, type|
+        if attributes.key?(map[key]) && attributes[map[key]].nil?
           transformed_hash["#{key}"] = nil
         elsif type =~ /\AArray<(.*)>/i
           # check to ensure the input is an array given that the attribute
           # is documented as an array but the input is not
-          if attributes[attribute_map[key]].is_a?(Array)
-            transformed_hash["#{key}"] = attributes[attribute_map[key]].map { |v| _deserialize($1, v) }
+          if attributes[map[key]].is_a?(Array)
+            transformed_hash["#{key}"] = attributes[map[key]].map { |v| _deserialize($1, v) }
           end
-        elsif !attributes[attribute_map[key]].nil?
-          transformed_hash["#{key}"] = _deserialize(type, attributes[attribute_map[key]])
+        elsif !attributes[map[key]].nil?
+          transformed_hash["#{key}"] = _deserialize(type, attributes[map[key]])
         end
       end
       new(transformed_hash)
@@ -150,10 +162,11 @@ def self.build_from_hash(attributes)
     # @return [Hash] Returns the object in the form of hash
     def to_hash
       hash = {}
-      self.class.attribute_map.each_pair do |attr, param|
+      # include attributes inherited from allOf parents (the nearest declaration wins)
+      self.class.acceptable_attribute_map.each_pair do |attr, param|
         value = self.send(attr)
         if value.nil?
-          is_nullable = self.class.openapi_nullable.include?(attr)
+          is_nullable = self.class.acceptable_openapi_nullable.include?(attr)
           next if !is_nullable || (is_nullable && !instance_variable_defined?(:"@#{attr}"))
         end
 
diff --git a/samples/client/petstore/ruby-httpx/lib/petstore/models/model200_response.rb b/samples/client/petstore/ruby-httpx/lib/petstore/models/model200_response.rb
index 9cff83ced2c9..2ea5253eb3d4 100644
--- a/samples/client/petstore/ruby-httpx/lib/petstore/models/model200_response.rb
+++ b/samples/client/petstore/ruby-httpx/lib/petstore/models/model200_response.rb
@@ -52,6 +52,16 @@ def self.openapi_nullable
       ])
     end
 
+    # Returns attribute type mapping
+    def self.acceptable_openapi_types
+      openapi_types
+    end
+
+    # Returns the nullable attributes
+    def self.acceptable_openapi_nullable
+      openapi_nullable
+    end
+
     # Initializes the object
     # @param [Hash] attributes Model attributes in the form of hash
     def initialize(attributes = {})
@@ -119,18 +129,20 @@ def hash
     def self.build_from_hash(attributes)
       return nil unless attributes.is_a?(Hash)
       attributes = attributes.transform_keys(&:to_sym)
+      # include attributes inherited from allOf parents (the nearest declaration wins)
+      map = acceptable_attribute_map
       transformed_hash = {}
-      openapi_types.each_pair do |key, type|
-        if attributes.key?(attribute_map[key]) && attributes[attribute_map[key]].nil?
+      acceptable_openapi_types.each_pair do |key, type|
+        if attributes.key?(map[key]) && attributes[map[key]].nil?
           transformed_hash["#{key}"] = nil
         elsif type =~ /\AArray<(.*)>/i
           # check to ensure the input is an array given that the attribute
           # is documented as an array but the input is not
-          if attributes[attribute_map[key]].is_a?(Array)
-            transformed_hash["#{key}"] = attributes[attribute_map[key]].map { |v| _deserialize($1, v) }
+          if attributes[map[key]].is_a?(Array)
+            transformed_hash["#{key}"] = attributes[map[key]].map { |v| _deserialize($1, v) }
           end
-        elsif !attributes[attribute_map[key]].nil?
-          transformed_hash["#{key}"] = _deserialize(type, attributes[attribute_map[key]])
+        elsif !attributes[map[key]].nil?
+          transformed_hash["#{key}"] = _deserialize(type, attributes[map[key]])
         end
       end
       new(transformed_hash)
@@ -140,10 +152,11 @@ def self.build_from_hash(attributes)
     # @return [Hash] Returns the object in the form of hash
     def to_hash
       hash = {}
-      self.class.attribute_map.each_pair do |attr, param|
+      # include attributes inherited from allOf parents (the nearest declaration wins)
+      self.class.acceptable_attribute_map.each_pair do |attr, param|
         value = self.send(attr)
         if value.nil?
-          is_nullable = self.class.openapi_nullable.include?(attr)
+          is_nullable = self.class.acceptable_openapi_nullable.include?(attr)
           next if !is_nullable || (is_nullable && !instance_variable_defined?(:"@#{attr}"))
         end
 
diff --git a/samples/client/petstore/ruby-httpx/lib/petstore/models/model_return.rb b/samples/client/petstore/ruby-httpx/lib/petstore/models/model_return.rb
index d520a45c2040..c2b6ac11c2e9 100644
--- a/samples/client/petstore/ruby-httpx/lib/petstore/models/model_return.rb
+++ b/samples/client/petstore/ruby-httpx/lib/petstore/models/model_return.rb
@@ -48,6 +48,16 @@ def self.openapi_nullable
       ])
     end
 
+    # Returns attribute type mapping
+    def self.acceptable_openapi_types
+      openapi_types
+    end
+
+    # Returns the nullable attributes
+    def self.acceptable_openapi_nullable
+      openapi_nullable
+    end
+
     # Initializes the object
     # @param [Hash] attributes Model attributes in the form of hash
     def initialize(attributes = {})
@@ -110,18 +120,20 @@ def hash
     def self.build_from_hash(attributes)
       return nil unless attributes.is_a?(Hash)
       attributes = attributes.transform_keys(&:to_sym)
+      # include attributes inherited from allOf parents (the nearest declaration wins)
+      map = acceptable_attribute_map
       transformed_hash = {}
-      openapi_types.each_pair do |key, type|
-        if attributes.key?(attribute_map[key]) && attributes[attribute_map[key]].nil?
+      acceptable_openapi_types.each_pair do |key, type|
+        if attributes.key?(map[key]) && attributes[map[key]].nil?
           transformed_hash["#{key}"] = nil
         elsif type =~ /\AArray<(.*)>/i
           # check to ensure the input is an array given that the attribute
           # is documented as an array but the input is not
-          if attributes[attribute_map[key]].is_a?(Array)
-            transformed_hash["#{key}"] = attributes[attribute_map[key]].map { |v| _deserialize($1, v) }
+          if attributes[map[key]].is_a?(Array)
+            transformed_hash["#{key}"] = attributes[map[key]].map { |v| _deserialize($1, v) }
           end
-        elsif !attributes[attribute_map[key]].nil?
-          transformed_hash["#{key}"] = _deserialize(type, attributes[attribute_map[key]])
+        elsif !attributes[map[key]].nil?
+          transformed_hash["#{key}"] = _deserialize(type, attributes[map[key]])
         end
       end
       new(transformed_hash)
@@ -131,10 +143,11 @@ def self.build_from_hash(attributes)
     # @return [Hash] Returns the object in the form of hash
     def to_hash
       hash = {}
-      self.class.attribute_map.each_pair do |attr, param|
+      # include attributes inherited from allOf parents (the nearest declaration wins)
+      self.class.acceptable_attribute_map.each_pair do |attr, param|
         value = self.send(attr)
         if value.nil?
-          is_nullable = self.class.openapi_nullable.include?(attr)
+          is_nullable = self.class.acceptable_openapi_nullable.include?(attr)
           next if !is_nullable || (is_nullable && !instance_variable_defined?(:"@#{attr}"))
         end
 
diff --git a/samples/client/petstore/ruby-httpx/lib/petstore/models/name.rb b/samples/client/petstore/ruby-httpx/lib/petstore/models/name.rb
index 45b01b5746d3..c989368e6597 100644
--- a/samples/client/petstore/ruby-httpx/lib/petstore/models/name.rb
+++ b/samples/client/petstore/ruby-httpx/lib/petstore/models/name.rb
@@ -60,6 +60,16 @@ def self.openapi_nullable
       ])
     end
 
+    # Returns attribute type mapping
+    def self.acceptable_openapi_types
+      openapi_types
+    end
+
+    # Returns the nullable attributes
+    def self.acceptable_openapi_nullable
+      openapi_nullable
+    end
+
     # Initializes the object
     # @param [Hash] attributes Model attributes in the form of hash
     def initialize(attributes = {})
@@ -154,18 +164,20 @@ def hash
     def self.build_from_hash(attributes)
       return nil unless attributes.is_a?(Hash)
       attributes = attributes.transform_keys(&:to_sym)
+      # include attributes inherited from allOf parents (the nearest declaration wins)
+      map = acceptable_attribute_map
       transformed_hash = {}
-      openapi_types.each_pair do |key, type|
-        if attributes.key?(attribute_map[key]) && attributes[attribute_map[key]].nil?
+      acceptable_openapi_types.each_pair do |key, type|
+        if attributes.key?(map[key]) && attributes[map[key]].nil?
           transformed_hash["#{key}"] = nil
         elsif type =~ /\AArray<(.*)>/i
           # check to ensure the input is an array given that the attribute
           # is documented as an array but the input is not
-          if attributes[attribute_map[key]].is_a?(Array)
-            transformed_hash["#{key}"] = attributes[attribute_map[key]].map { |v| _deserialize($1, v) }
+          if attributes[map[key]].is_a?(Array)
+            transformed_hash["#{key}"] = attributes[map[key]].map { |v| _deserialize($1, v) }
           end
-        elsif !attributes[attribute_map[key]].nil?
-          transformed_hash["#{key}"] = _deserialize(type, attributes[attribute_map[key]])
+        elsif !attributes[map[key]].nil?
+          transformed_hash["#{key}"] = _deserialize(type, attributes[map[key]])
         end
       end
       new(transformed_hash)
@@ -175,10 +187,11 @@ def self.build_from_hash(attributes)
     # @return [Hash] Returns the object in the form of hash
     def to_hash
       hash = {}
-      self.class.attribute_map.each_pair do |attr, param|
+      # include attributes inherited from allOf parents (the nearest declaration wins)
+      self.class.acceptable_attribute_map.each_pair do |attr, param|
         value = self.send(attr)
         if value.nil?
-          is_nullable = self.class.openapi_nullable.include?(attr)
+          is_nullable = self.class.acceptable_openapi_nullable.include?(attr)
           next if !is_nullable || (is_nullable && !instance_variable_defined?(:"@#{attr}"))
         end
 
diff --git a/samples/client/petstore/ruby-httpx/lib/petstore/models/nullable_class.rb b/samples/client/petstore/ruby-httpx/lib/petstore/models/nullable_class.rb
index f81fb17f118a..de5510060a65 100644
--- a/samples/client/petstore/ruby-httpx/lib/petstore/models/nullable_class.rb
+++ b/samples/client/petstore/ruby-httpx/lib/petstore/models/nullable_class.rb
@@ -101,6 +101,16 @@ def self.openapi_nullable
       ])
     end
 
+    # Returns attribute type mapping
+    def self.acceptable_openapi_types
+      openapi_types
+    end
+
+    # Returns the nullable attributes
+    def self.acceptable_openapi_nullable
+      openapi_nullable
+    end
+
     # Initializes the object
     # @param [Hash] attributes Model attributes in the form of hash
     def initialize(attributes = {})
@@ -230,18 +240,20 @@ def hash
     def self.build_from_hash(attributes)
       return nil unless attributes.is_a?(Hash)
       attributes = attributes.transform_keys(&:to_sym)
+      # include attributes inherited from allOf parents (the nearest declaration wins)
+      map = acceptable_attribute_map
       transformed_hash = {}
-      openapi_types.each_pair do |key, type|
-        if attributes.key?(attribute_map[key]) && attributes[attribute_map[key]].nil?
+      acceptable_openapi_types.each_pair do |key, type|
+        if attributes.key?(map[key]) && attributes[map[key]].nil?
           transformed_hash["#{key}"] = nil
         elsif type =~ /\AArray<(.*)>/i
           # check to ensure the input is an array given that the attribute
           # is documented as an array but the input is not
-          if attributes[attribute_map[key]].is_a?(Array)
-            transformed_hash["#{key}"] = attributes[attribute_map[key]].map { |v| _deserialize($1, v) }
+          if attributes[map[key]].is_a?(Array)
+            transformed_hash["#{key}"] = attributes[map[key]].map { |v| _deserialize($1, v) }
           end
-        elsif !attributes[attribute_map[key]].nil?
-          transformed_hash["#{key}"] = _deserialize(type, attributes[attribute_map[key]])
+        elsif !attributes[map[key]].nil?
+          transformed_hash["#{key}"] = _deserialize(type, attributes[map[key]])
         end
       end
       new(transformed_hash)
@@ -251,10 +263,11 @@ def self.build_from_hash(attributes)
     # @return [Hash] Returns the object in the form of hash
     def to_hash
       hash = {}
-      self.class.attribute_map.each_pair do |attr, param|
+      # include attributes inherited from allOf parents (the nearest declaration wins)
+      self.class.acceptable_attribute_map.each_pair do |attr, param|
         value = self.send(attr)
         if value.nil?
-          is_nullable = self.class.openapi_nullable.include?(attr)
+          is_nullable = self.class.acceptable_openapi_nullable.include?(attr)
           next if !is_nullable || (is_nullable && !instance_variable_defined?(:"@#{attr}"))
         end
 
diff --git a/samples/client/petstore/ruby-httpx/lib/petstore/models/number_only.rb b/samples/client/petstore/ruby-httpx/lib/petstore/models/number_only.rb
index 9bf457dfd188..b4fb53e2c3d3 100644
--- a/samples/client/petstore/ruby-httpx/lib/petstore/models/number_only.rb
+++ b/samples/client/petstore/ruby-httpx/lib/petstore/models/number_only.rb
@@ -47,6 +47,16 @@ def self.openapi_nullable
       ])
     end
 
+    # Returns attribute type mapping
+    def self.acceptable_openapi_types
+      openapi_types
+    end
+
+    # Returns the nullable attributes
+    def self.acceptable_openapi_nullable
+      openapi_nullable
+    end
+
     # Initializes the object
     # @param [Hash] attributes Model attributes in the form of hash
     def initialize(attributes = {})
@@ -109,18 +119,20 @@ def hash
     def self.build_from_hash(attributes)
       return nil unless attributes.is_a?(Hash)
       attributes = attributes.transform_keys(&:to_sym)
+      # include attributes inherited from allOf parents (the nearest declaration wins)
+      map = acceptable_attribute_map
       transformed_hash = {}
-      openapi_types.each_pair do |key, type|
-        if attributes.key?(attribute_map[key]) && attributes[attribute_map[key]].nil?
+      acceptable_openapi_types.each_pair do |key, type|
+        if attributes.key?(map[key]) && attributes[map[key]].nil?
           transformed_hash["#{key}"] = nil
         elsif type =~ /\AArray<(.*)>/i
           # check to ensure the input is an array given that the attribute
           # is documented as an array but the input is not
-          if attributes[attribute_map[key]].is_a?(Array)
-            transformed_hash["#{key}"] = attributes[attribute_map[key]].map { |v| _deserialize($1, v) }
+          if attributes[map[key]].is_a?(Array)
+            transformed_hash["#{key}"] = attributes[map[key]].map { |v| _deserialize($1, v) }
           end
-        elsif !attributes[attribute_map[key]].nil?
-          transformed_hash["#{key}"] = _deserialize(type, attributes[attribute_map[key]])
+        elsif !attributes[map[key]].nil?
+          transformed_hash["#{key}"] = _deserialize(type, attributes[map[key]])
         end
       end
       new(transformed_hash)
@@ -130,10 +142,11 @@ def self.build_from_hash(attributes)
     # @return [Hash] Returns the object in the form of hash
     def to_hash
       hash = {}
-      self.class.attribute_map.each_pair do |attr, param|
+      # include attributes inherited from allOf parents (the nearest declaration wins)
+      self.class.acceptable_attribute_map.each_pair do |attr, param|
         value = self.send(attr)
         if value.nil?
-          is_nullable = self.class.openapi_nullable.include?(attr)
+          is_nullable = self.class.acceptable_openapi_nullable.include?(attr)
           next if !is_nullable || (is_nullable && !instance_variable_defined?(:"@#{attr}"))
         end
 
diff --git a/samples/client/petstore/ruby-httpx/lib/petstore/models/object_with_deprecated_fields.rb b/samples/client/petstore/ruby-httpx/lib/petstore/models/object_with_deprecated_fields.rb
index dceda346bd70..3819fef7a58b 100644
--- a/samples/client/petstore/ruby-httpx/lib/petstore/models/object_with_deprecated_fields.rb
+++ b/samples/client/petstore/ruby-httpx/lib/petstore/models/object_with_deprecated_fields.rb
@@ -59,6 +59,16 @@ def self.openapi_nullable
       ])
     end
 
+    # Returns attribute type mapping
+    def self.acceptable_openapi_types
+      openapi_types
+    end
+
+    # Returns the nullable attributes
+    def self.acceptable_openapi_nullable
+      openapi_nullable
+    end
+
     # Initializes the object
     # @param [Hash] attributes Model attributes in the form of hash
     def initialize(attributes = {})
@@ -138,18 +148,20 @@ def hash
     def self.build_from_hash(attributes)
       return nil unless attributes.is_a?(Hash)
       attributes = attributes.transform_keys(&:to_sym)
+      # include attributes inherited from allOf parents (the nearest declaration wins)
+      map = acceptable_attribute_map
       transformed_hash = {}
-      openapi_types.each_pair do |key, type|
-        if attributes.key?(attribute_map[key]) && attributes[attribute_map[key]].nil?
+      acceptable_openapi_types.each_pair do |key, type|
+        if attributes.key?(map[key]) && attributes[map[key]].nil?
           transformed_hash["#{key}"] = nil
         elsif type =~ /\AArray<(.*)>/i
           # check to ensure the input is an array given that the attribute
           # is documented as an array but the input is not
-          if attributes[attribute_map[key]].is_a?(Array)
-            transformed_hash["#{key}"] = attributes[attribute_map[key]].map { |v| _deserialize($1, v) }
+          if attributes[map[key]].is_a?(Array)
+            transformed_hash["#{key}"] = attributes[map[key]].map { |v| _deserialize($1, v) }
           end
-        elsif !attributes[attribute_map[key]].nil?
-          transformed_hash["#{key}"] = _deserialize(type, attributes[attribute_map[key]])
+        elsif !attributes[map[key]].nil?
+          transformed_hash["#{key}"] = _deserialize(type, attributes[map[key]])
         end
       end
       new(transformed_hash)
@@ -159,10 +171,11 @@ def self.build_from_hash(attributes)
     # @return [Hash] Returns the object in the form of hash
     def to_hash
       hash = {}
-      self.class.attribute_map.each_pair do |attr, param|
+      # include attributes inherited from allOf parents (the nearest declaration wins)
+      self.class.acceptable_attribute_map.each_pair do |attr, param|
         value = self.send(attr)
         if value.nil?
-          is_nullable = self.class.openapi_nullable.include?(attr)
+          is_nullable = self.class.acceptable_openapi_nullable.include?(attr)
           next if !is_nullable || (is_nullable && !instance_variable_defined?(:"@#{attr}"))
         end
 
diff --git a/samples/client/petstore/ruby-httpx/lib/petstore/models/order.rb b/samples/client/petstore/ruby-httpx/lib/petstore/models/order.rb
index f7e7b4eb9117..8cebfcefa34e 100644
--- a/samples/client/petstore/ruby-httpx/lib/petstore/models/order.rb
+++ b/samples/client/petstore/ruby-httpx/lib/petstore/models/order.rb
@@ -90,6 +90,16 @@ def self.openapi_nullable
       ])
     end
 
+    # Returns attribute type mapping
+    def self.acceptable_openapi_types
+      openapi_types
+    end
+
+    # Returns the nullable attributes
+    def self.acceptable_openapi_nullable
+      openapi_nullable
+    end
+
     # Initializes the object
     # @param [Hash] attributes Model attributes in the form of hash
     def initialize(attributes = {})
@@ -191,18 +201,20 @@ def hash
     def self.build_from_hash(attributes)
       return nil unless attributes.is_a?(Hash)
       attributes = attributes.transform_keys(&:to_sym)
+      # include attributes inherited from allOf parents (the nearest declaration wins)
+      map = acceptable_attribute_map
       transformed_hash = {}
-      openapi_types.each_pair do |key, type|
-        if attributes.key?(attribute_map[key]) && attributes[attribute_map[key]].nil?
+      acceptable_openapi_types.each_pair do |key, type|
+        if attributes.key?(map[key]) && attributes[map[key]].nil?
           transformed_hash["#{key}"] = nil
         elsif type =~ /\AArray<(.*)>/i
           # check to ensure the input is an array given that the attribute
           # is documented as an array but the input is not
-          if attributes[attribute_map[key]].is_a?(Array)
-            transformed_hash["#{key}"] = attributes[attribute_map[key]].map { |v| _deserialize($1, v) }
+          if attributes[map[key]].is_a?(Array)
+            transformed_hash["#{key}"] = attributes[map[key]].map { |v| _deserialize($1, v) }
           end
-        elsif !attributes[attribute_map[key]].nil?
-          transformed_hash["#{key}"] = _deserialize(type, attributes[attribute_map[key]])
+        elsif !attributes[map[key]].nil?
+          transformed_hash["#{key}"] = _deserialize(type, attributes[map[key]])
         end
       end
       new(transformed_hash)
@@ -212,10 +224,11 @@ def self.build_from_hash(attributes)
     # @return [Hash] Returns the object in the form of hash
     def to_hash
       hash = {}
-      self.class.attribute_map.each_pair do |attr, param|
+      # include attributes inherited from allOf parents (the nearest declaration wins)
+      self.class.acceptable_attribute_map.each_pair do |attr, param|
         value = self.send(attr)
         if value.nil?
-          is_nullable = self.class.openapi_nullable.include?(attr)
+          is_nullable = self.class.acceptable_openapi_nullable.include?(attr)
           next if !is_nullable || (is_nullable && !instance_variable_defined?(:"@#{attr}"))
         end
 
diff --git a/samples/client/petstore/ruby-httpx/lib/petstore/models/outer_composite.rb b/samples/client/petstore/ruby-httpx/lib/petstore/models/outer_composite.rb
index 2245e8512600..afa9203ebde9 100644
--- a/samples/client/petstore/ruby-httpx/lib/petstore/models/outer_composite.rb
+++ b/samples/client/petstore/ruby-httpx/lib/petstore/models/outer_composite.rb
@@ -55,6 +55,16 @@ def self.openapi_nullable
       ])
     end
 
+    # Returns attribute type mapping
+    def self.acceptable_openapi_types
+      openapi_types
+    end
+
+    # Returns the nullable attributes
+    def self.acceptable_openapi_nullable
+      openapi_nullable
+    end
+
     # Initializes the object
     # @param [Hash] attributes Model attributes in the form of hash
     def initialize(attributes = {})
@@ -127,18 +137,20 @@ def hash
     def self.build_from_hash(attributes)
       return nil unless attributes.is_a?(Hash)
       attributes = attributes.transform_keys(&:to_sym)
+      # include attributes inherited from allOf parents (the nearest declaration wins)
+      map = acceptable_attribute_map
       transformed_hash = {}
-      openapi_types.each_pair do |key, type|
-        if attributes.key?(attribute_map[key]) && attributes[attribute_map[key]].nil?
+      acceptable_openapi_types.each_pair do |key, type|
+        if attributes.key?(map[key]) && attributes[map[key]].nil?
           transformed_hash["#{key}"] = nil
         elsif type =~ /\AArray<(.*)>/i
           # check to ensure the input is an array given that the attribute
           # is documented as an array but the input is not
-          if attributes[attribute_map[key]].is_a?(Array)
-            transformed_hash["#{key}"] = attributes[attribute_map[key]].map { |v| _deserialize($1, v) }
+          if attributes[map[key]].is_a?(Array)
+            transformed_hash["#{key}"] = attributes[map[key]].map { |v| _deserialize($1, v) }
           end
-        elsif !attributes[attribute_map[key]].nil?
-          transformed_hash["#{key}"] = _deserialize(type, attributes[attribute_map[key]])
+        elsif !attributes[map[key]].nil?
+          transformed_hash["#{key}"] = _deserialize(type, attributes[map[key]])
         end
       end
       new(transformed_hash)
@@ -148,10 +160,11 @@ def self.build_from_hash(attributes)
     # @return [Hash] Returns the object in the form of hash
     def to_hash
       hash = {}
-      self.class.attribute_map.each_pair do |attr, param|
+      # include attributes inherited from allOf parents (the nearest declaration wins)
+      self.class.acceptable_attribute_map.each_pair do |attr, param|
         value = self.send(attr)
         if value.nil?
-          is_nullable = self.class.openapi_nullable.include?(attr)
+          is_nullable = self.class.acceptable_openapi_nullable.include?(attr)
           next if !is_nullable || (is_nullable && !instance_variable_defined?(:"@#{attr}"))
         end
 
diff --git a/samples/client/petstore/ruby-httpx/lib/petstore/models/outer_object_with_enum_property.rb b/samples/client/petstore/ruby-httpx/lib/petstore/models/outer_object_with_enum_property.rb
index 8ffad20f8d89..1fd79229d4f6 100644
--- a/samples/client/petstore/ruby-httpx/lib/petstore/models/outer_object_with_enum_property.rb
+++ b/samples/client/petstore/ruby-httpx/lib/petstore/models/outer_object_with_enum_property.rb
@@ -69,6 +69,16 @@ def self.openapi_nullable
       ])
     end
 
+    # Returns attribute type mapping
+    def self.acceptable_openapi_types
+      openapi_types
+    end
+
+    # Returns the nullable attributes
+    def self.acceptable_openapi_nullable
+      openapi_nullable
+    end
+
     # Initializes the object
     # @param [Hash] attributes Model attributes in the form of hash
     def initialize(attributes = {})
@@ -148,18 +158,20 @@ def hash
     def self.build_from_hash(attributes)
       return nil unless attributes.is_a?(Hash)
       attributes = attributes.transform_keys(&:to_sym)
+      # include attributes inherited from allOf parents (the nearest declaration wins)
+      map = acceptable_attribute_map
       transformed_hash = {}
-      openapi_types.each_pair do |key, type|
-        if attributes.key?(attribute_map[key]) && attributes[attribute_map[key]].nil?
+      acceptable_openapi_types.each_pair do |key, type|
+        if attributes.key?(map[key]) && attributes[map[key]].nil?
           transformed_hash["#{key}"] = nil
         elsif type =~ /\AArray<(.*)>/i
           # check to ensure the input is an array given that the attribute
           # is documented as an array but the input is not
-          if attributes[attribute_map[key]].is_a?(Array)
-            transformed_hash["#{key}"] = attributes[attribute_map[key]].map { |v| _deserialize($1, v) }
+          if attributes[map[key]].is_a?(Array)
+            transformed_hash["#{key}"] = attributes[map[key]].map { |v| _deserialize($1, v) }
           end
-        elsif !attributes[attribute_map[key]].nil?
-          transformed_hash["#{key}"] = _deserialize(type, attributes[attribute_map[key]])
+        elsif !attributes[map[key]].nil?
+          transformed_hash["#{key}"] = _deserialize(type, attributes[map[key]])
         end
       end
       new(transformed_hash)
@@ -169,10 +181,11 @@ def self.build_from_hash(attributes)
     # @return [Hash] Returns the object in the form of hash
     def to_hash
       hash = {}
-      self.class.attribute_map.each_pair do |attr, param|
+      # include attributes inherited from allOf parents (the nearest declaration wins)
+      self.class.acceptable_attribute_map.each_pair do |attr, param|
         value = self.send(attr)
         if value.nil?
-          is_nullable = self.class.openapi_nullable.include?(attr)
+          is_nullable = self.class.acceptable_openapi_nullable.include?(attr)
           next if !is_nullable || (is_nullable && !instance_variable_defined?(:"@#{attr}"))
         end
 
diff --git a/samples/client/petstore/ruby-httpx/lib/petstore/models/pet.rb b/samples/client/petstore/ruby-httpx/lib/petstore/models/pet.rb
index e3594a1fb052..5a86112a15cf 100644
--- a/samples/client/petstore/ruby-httpx/lib/petstore/models/pet.rb
+++ b/samples/client/petstore/ruby-httpx/lib/petstore/models/pet.rb
@@ -90,6 +90,16 @@ def self.openapi_nullable
       ])
     end
 
+    # Returns attribute type mapping
+    def self.acceptable_openapi_types
+      openapi_types
+    end
+
+    # Returns the nullable attributes
+    def self.acceptable_openapi_nullable
+      openapi_nullable
+    end
+
     # Initializes the object
     # @param [Hash] attributes Model attributes in the form of hash
     def initialize(attributes = {})
@@ -227,18 +237,20 @@ def hash
     def self.build_from_hash(attributes)
       return nil unless attributes.is_a?(Hash)
       attributes = attributes.transform_keys(&:to_sym)
+      # include attributes inherited from allOf parents (the nearest declaration wins)
+      map = acceptable_attribute_map
       transformed_hash = {}
-      openapi_types.each_pair do |key, type|
-        if attributes.key?(attribute_map[key]) && attributes[attribute_map[key]].nil?
+      acceptable_openapi_types.each_pair do |key, type|
+        if attributes.key?(map[key]) && attributes[map[key]].nil?
           transformed_hash["#{key}"] = nil
         elsif type =~ /\AArray<(.*)>/i
           # check to ensure the input is an array given that the attribute
           # is documented as an array but the input is not
-          if attributes[attribute_map[key]].is_a?(Array)
-            transformed_hash["#{key}"] = attributes[attribute_map[key]].map { |v| _deserialize($1, v) }
+          if attributes[map[key]].is_a?(Array)
+            transformed_hash["#{key}"] = attributes[map[key]].map { |v| _deserialize($1, v) }
           end
-        elsif !attributes[attribute_map[key]].nil?
-          transformed_hash["#{key}"] = _deserialize(type, attributes[attribute_map[key]])
+        elsif !attributes[map[key]].nil?
+          transformed_hash["#{key}"] = _deserialize(type, attributes[map[key]])
         end
       end
       new(transformed_hash)
@@ -248,10 +260,11 @@ def self.build_from_hash(attributes)
     # @return [Hash] Returns the object in the form of hash
     def to_hash
       hash = {}
-      self.class.attribute_map.each_pair do |attr, param|
+      # include attributes inherited from allOf parents (the nearest declaration wins)
+      self.class.acceptable_attribute_map.each_pair do |attr, param|
         value = self.send(attr)
         if value.nil?
-          is_nullable = self.class.openapi_nullable.include?(attr)
+          is_nullable = self.class.acceptable_openapi_nullable.include?(attr)
           next if !is_nullable || (is_nullable && !instance_variable_defined?(:"@#{attr}"))
         end
 
diff --git a/samples/client/petstore/ruby-httpx/lib/petstore/models/property_name_mapping.rb b/samples/client/petstore/ruby-httpx/lib/petstore/models/property_name_mapping.rb
index 8328edb9227a..82c1d3be0d08 100644
--- a/samples/client/petstore/ruby-httpx/lib/petstore/models/property_name_mapping.rb
+++ b/samples/client/petstore/ruby-httpx/lib/petstore/models/property_name_mapping.rb
@@ -59,6 +59,16 @@ def self.openapi_nullable
       ])
     end
 
+    # Returns attribute type mapping
+    def self.acceptable_openapi_types
+      openapi_types
+    end
+
+    # Returns the nullable attributes
+    def self.acceptable_openapi_nullable
+      openapi_nullable
+    end
+
     # Initializes the object
     # @param [Hash] attributes Model attributes in the form of hash
     def initialize(attributes = {})
@@ -136,18 +146,20 @@ def hash
     def self.build_from_hash(attributes)
       return nil unless attributes.is_a?(Hash)
       attributes = attributes.transform_keys(&:to_sym)
+      # include attributes inherited from allOf parents (the nearest declaration wins)
+      map = acceptable_attribute_map
       transformed_hash = {}
-      openapi_types.each_pair do |key, type|
-        if attributes.key?(attribute_map[key]) && attributes[attribute_map[key]].nil?
+      acceptable_openapi_types.each_pair do |key, type|
+        if attributes.key?(map[key]) && attributes[map[key]].nil?
           transformed_hash["#{key}"] = nil
         elsif type =~ /\AArray<(.*)>/i
           # check to ensure the input is an array given that the attribute
           # is documented as an array but the input is not
-          if attributes[attribute_map[key]].is_a?(Array)
-            transformed_hash["#{key}"] = attributes[attribute_map[key]].map { |v| _deserialize($1, v) }
+          if attributes[map[key]].is_a?(Array)
+            transformed_hash["#{key}"] = attributes[map[key]].map { |v| _deserialize($1, v) }
           end
-        elsif !attributes[attribute_map[key]].nil?
-          transformed_hash["#{key}"] = _deserialize(type, attributes[attribute_map[key]])
+        elsif !attributes[map[key]].nil?
+          transformed_hash["#{key}"] = _deserialize(type, attributes[map[key]])
         end
       end
       new(transformed_hash)
@@ -157,10 +169,11 @@ def self.build_from_hash(attributes)
     # @return [Hash] Returns the object in the form of hash
     def to_hash
       hash = {}
-      self.class.attribute_map.each_pair do |attr, param|
+      # include attributes inherited from allOf parents (the nearest declaration wins)
+      self.class.acceptable_attribute_map.each_pair do |attr, param|
         value = self.send(attr)
         if value.nil?
-          is_nullable = self.class.openapi_nullable.include?(attr)
+          is_nullable = self.class.acceptable_openapi_nullable.include?(attr)
           next if !is_nullable || (is_nullable && !instance_variable_defined?(:"@#{attr}"))
         end
 
diff --git a/samples/client/petstore/ruby-httpx/lib/petstore/models/read_only_first.rb b/samples/client/petstore/ruby-httpx/lib/petstore/models/read_only_first.rb
index c2121474ebb7..d008b4369a91 100644
--- a/samples/client/petstore/ruby-httpx/lib/petstore/models/read_only_first.rb
+++ b/samples/client/petstore/ruby-httpx/lib/petstore/models/read_only_first.rb
@@ -51,6 +51,16 @@ def self.openapi_nullable
       ])
     end
 
+    # Returns attribute type mapping
+    def self.acceptable_openapi_types
+      openapi_types
+    end
+
+    # Returns the nullable attributes
+    def self.acceptable_openapi_nullable
+      openapi_nullable
+    end
+
     # Initializes the object
     # @param [Hash] attributes Model attributes in the form of hash
     def initialize(attributes = {})
@@ -118,18 +128,20 @@ def hash
     def self.build_from_hash(attributes)
       return nil unless attributes.is_a?(Hash)
       attributes = attributes.transform_keys(&:to_sym)
+      # include attributes inherited from allOf parents (the nearest declaration wins)
+      map = acceptable_attribute_map
       transformed_hash = {}
-      openapi_types.each_pair do |key, type|
-        if attributes.key?(attribute_map[key]) && attributes[attribute_map[key]].nil?
+      acceptable_openapi_types.each_pair do |key, type|
+        if attributes.key?(map[key]) && attributes[map[key]].nil?
           transformed_hash["#{key}"] = nil
         elsif type =~ /\AArray<(.*)>/i
           # check to ensure the input is an array given that the attribute
           # is documented as an array but the input is not
-          if attributes[attribute_map[key]].is_a?(Array)
-            transformed_hash["#{key}"] = attributes[attribute_map[key]].map { |v| _deserialize($1, v) }
+          if attributes[map[key]].is_a?(Array)
+            transformed_hash["#{key}"] = attributes[map[key]].map { |v| _deserialize($1, v) }
           end
-        elsif !attributes[attribute_map[key]].nil?
-          transformed_hash["#{key}"] = _deserialize(type, attributes[attribute_map[key]])
+        elsif !attributes[map[key]].nil?
+          transformed_hash["#{key}"] = _deserialize(type, attributes[map[key]])
         end
       end
       new(transformed_hash)
@@ -139,10 +151,11 @@ def self.build_from_hash(attributes)
     # @return [Hash] Returns the object in the form of hash
     def to_hash
       hash = {}
-      self.class.attribute_map.each_pair do |attr, param|
+      # include attributes inherited from allOf parents (the nearest declaration wins)
+      self.class.acceptable_attribute_map.each_pair do |attr, param|
         value = self.send(attr)
         if value.nil?
-          is_nullable = self.class.openapi_nullable.include?(attr)
+          is_nullable = self.class.acceptable_openapi_nullable.include?(attr)
           next if !is_nullable || (is_nullable && !instance_variable_defined?(:"@#{attr}"))
         end
 
diff --git a/samples/client/petstore/ruby-httpx/lib/petstore/models/special_model_name.rb b/samples/client/petstore/ruby-httpx/lib/petstore/models/special_model_name.rb
index 9569fbfd13dd..b6d4135991be 100644
--- a/samples/client/petstore/ruby-httpx/lib/petstore/models/special_model_name.rb
+++ b/samples/client/petstore/ruby-httpx/lib/petstore/models/special_model_name.rb
@@ -47,6 +47,16 @@ def self.openapi_nullable
       ])
     end
 
+    # Returns attribute type mapping
+    def self.acceptable_openapi_types
+      openapi_types
+    end
+
+    # Returns the nullable attributes
+    def self.acceptable_openapi_nullable
+      openapi_nullable
+    end
+
     # Initializes the object
     # @param [Hash] attributes Model attributes in the form of hash
     def initialize(attributes = {})
@@ -109,18 +119,20 @@ def hash
     def self.build_from_hash(attributes)
       return nil unless attributes.is_a?(Hash)
       attributes = attributes.transform_keys(&:to_sym)
+      # include attributes inherited from allOf parents (the nearest declaration wins)
+      map = acceptable_attribute_map
       transformed_hash = {}
-      openapi_types.each_pair do |key, type|
-        if attributes.key?(attribute_map[key]) && attributes[attribute_map[key]].nil?
+      acceptable_openapi_types.each_pair do |key, type|
+        if attributes.key?(map[key]) && attributes[map[key]].nil?
           transformed_hash["#{key}"] = nil
         elsif type =~ /\AArray<(.*)>/i
           # check to ensure the input is an array given that the attribute
           # is documented as an array but the input is not
-          if attributes[attribute_map[key]].is_a?(Array)
-            transformed_hash["#{key}"] = attributes[attribute_map[key]].map { |v| _deserialize($1, v) }
+          if attributes[map[key]].is_a?(Array)
+            transformed_hash["#{key}"] = attributes[map[key]].map { |v| _deserialize($1, v) }
           end
-        elsif !attributes[attribute_map[key]].nil?
-          transformed_hash["#{key}"] = _deserialize(type, attributes[attribute_map[key]])
+        elsif !attributes[map[key]].nil?
+          transformed_hash["#{key}"] = _deserialize(type, attributes[map[key]])
         end
       end
       new(transformed_hash)
@@ -130,10 +142,11 @@ def self.build_from_hash(attributes)
     # @return [Hash] Returns the object in the form of hash
     def to_hash
       hash = {}
-      self.class.attribute_map.each_pair do |attr, param|
+      # include attributes inherited from allOf parents (the nearest declaration wins)
+      self.class.acceptable_attribute_map.each_pair do |attr, param|
         value = self.send(attr)
         if value.nil?
-          is_nullable = self.class.openapi_nullable.include?(attr)
+          is_nullable = self.class.acceptable_openapi_nullable.include?(attr)
           next if !is_nullable || (is_nullable && !instance_variable_defined?(:"@#{attr}"))
         end
 
diff --git a/samples/client/petstore/ruby-httpx/lib/petstore/models/tag.rb b/samples/client/petstore/ruby-httpx/lib/petstore/models/tag.rb
index 6d6f57468181..22589f4e58b3 100644
--- a/samples/client/petstore/ruby-httpx/lib/petstore/models/tag.rb
+++ b/samples/client/petstore/ruby-httpx/lib/petstore/models/tag.rb
@@ -51,6 +51,16 @@ def self.openapi_nullable
       ])
     end
 
+    # Returns attribute type mapping
+    def self.acceptable_openapi_types
+      openapi_types
+    end
+
+    # Returns the nullable attributes
+    def self.acceptable_openapi_nullable
+      openapi_nullable
+    end
+
     # Initializes the object
     # @param [Hash] attributes Model attributes in the form of hash
     def initialize(attributes = {})
@@ -118,18 +128,20 @@ def hash
     def self.build_from_hash(attributes)
       return nil unless attributes.is_a?(Hash)
       attributes = attributes.transform_keys(&:to_sym)
+      # include attributes inherited from allOf parents (the nearest declaration wins)
+      map = acceptable_attribute_map
       transformed_hash = {}
-      openapi_types.each_pair do |key, type|
-        if attributes.key?(attribute_map[key]) && attributes[attribute_map[key]].nil?
+      acceptable_openapi_types.each_pair do |key, type|
+        if attributes.key?(map[key]) && attributes[map[key]].nil?
           transformed_hash["#{key}"] = nil
         elsif type =~ /\AArray<(.*)>/i
           # check to ensure the input is an array given that the attribute
           # is documented as an array but the input is not
-          if attributes[attribute_map[key]].is_a?(Array)
-            transformed_hash["#{key}"] = attributes[attribute_map[key]].map { |v| _deserialize($1, v) }
+          if attributes[map[key]].is_a?(Array)
+            transformed_hash["#{key}"] = attributes[map[key]].map { |v| _deserialize($1, v) }
           end
-        elsif !attributes[attribute_map[key]].nil?
-          transformed_hash["#{key}"] = _deserialize(type, attributes[attribute_map[key]])
+        elsif !attributes[map[key]].nil?
+          transformed_hash["#{key}"] = _deserialize(type, attributes[map[key]])
         end
       end
       new(transformed_hash)
@@ -139,10 +151,11 @@ def self.build_from_hash(attributes)
     # @return [Hash] Returns the object in the form of hash
     def to_hash
       hash = {}
-      self.class.attribute_map.each_pair do |attr, param|
+      # include attributes inherited from allOf parents (the nearest declaration wins)
+      self.class.acceptable_attribute_map.each_pair do |attr, param|
         value = self.send(attr)
         if value.nil?
-          is_nullable = self.class.openapi_nullable.include?(attr)
+          is_nullable = self.class.acceptable_openapi_nullable.include?(attr)
           next if !is_nullable || (is_nullable && !instance_variable_defined?(:"@#{attr}"))
         end
 
diff --git a/samples/client/petstore/ruby-httpx/lib/petstore/models/test_inline_freeform_additional_properties_request.rb b/samples/client/petstore/ruby-httpx/lib/petstore/models/test_inline_freeform_additional_properties_request.rb
index dc481c119d22..9e52e64e286b 100644
--- a/samples/client/petstore/ruby-httpx/lib/petstore/models/test_inline_freeform_additional_properties_request.rb
+++ b/samples/client/petstore/ruby-httpx/lib/petstore/models/test_inline_freeform_additional_properties_request.rb
@@ -47,6 +47,16 @@ def self.openapi_nullable
       ])
     end
 
+    # Returns attribute type mapping
+    def self.acceptable_openapi_types
+      openapi_types
+    end
+
+    # Returns the nullable attributes
+    def self.acceptable_openapi_nullable
+      openapi_nullable
+    end
+
     # Initializes the object
     # @param [Hash] attributes Model attributes in the form of hash
     def initialize(attributes = {})
@@ -109,18 +119,20 @@ def hash
     def self.build_from_hash(attributes)
       return nil unless attributes.is_a?(Hash)
       attributes = attributes.transform_keys(&:to_sym)
+      # include attributes inherited from allOf parents (the nearest declaration wins)
+      map = acceptable_attribute_map
       transformed_hash = {}
-      openapi_types.each_pair do |key, type|
-        if attributes.key?(attribute_map[key]) && attributes[attribute_map[key]].nil?
+      acceptable_openapi_types.each_pair do |key, type|
+        if attributes.key?(map[key]) && attributes[map[key]].nil?
           transformed_hash["#{key}"] = nil
         elsif type =~ /\AArray<(.*)>/i
           # check to ensure the input is an array given that the attribute
           # is documented as an array but the input is not
-          if attributes[attribute_map[key]].is_a?(Array)
-            transformed_hash["#{key}"] = attributes[attribute_map[key]].map { |v| _deserialize($1, v) }
+          if attributes[map[key]].is_a?(Array)
+            transformed_hash["#{key}"] = attributes[map[key]].map { |v| _deserialize($1, v) }
           end
-        elsif !attributes[attribute_map[key]].nil?
-          transformed_hash["#{key}"] = _deserialize(type, attributes[attribute_map[key]])
+        elsif !attributes[map[key]].nil?
+          transformed_hash["#{key}"] = _deserialize(type, attributes[map[key]])
         end
       end
       new(transformed_hash)
@@ -130,10 +142,11 @@ def self.build_from_hash(attributes)
     # @return [Hash] Returns the object in the form of hash
     def to_hash
       hash = {}
-      self.class.attribute_map.each_pair do |attr, param|
+      # include attributes inherited from allOf parents (the nearest declaration wins)
+      self.class.acceptable_attribute_map.each_pair do |attr, param|
         value = self.send(attr)
         if value.nil?
-          is_nullable = self.class.openapi_nullable.include?(attr)
+          is_nullable = self.class.acceptable_openapi_nullable.include?(attr)
           next if !is_nullable || (is_nullable && !instance_variable_defined?(:"@#{attr}"))
         end
 
diff --git a/samples/client/petstore/ruby-httpx/lib/petstore/models/user.rb b/samples/client/petstore/ruby-httpx/lib/petstore/models/user.rb
index 9b06f2ff6d7a..4b67db8214e2 100644
--- a/samples/client/petstore/ruby-httpx/lib/petstore/models/user.rb
+++ b/samples/client/petstore/ruby-httpx/lib/petstore/models/user.rb
@@ -76,6 +76,16 @@ def self.openapi_nullable
       ])
     end
 
+    # Returns attribute type mapping
+    def self.acceptable_openapi_types
+      openapi_types
+    end
+
+    # Returns the nullable attributes
+    def self.acceptable_openapi_nullable
+      openapi_nullable
+    end
+
     # Initializes the object
     # @param [Hash] attributes Model attributes in the form of hash
     def initialize(attributes = {})
@@ -173,18 +183,20 @@ def hash
     def self.build_from_hash(attributes)
       return nil unless attributes.is_a?(Hash)
       attributes = attributes.transform_keys(&:to_sym)
+      # include attributes inherited from allOf parents (the nearest declaration wins)
+      map = acceptable_attribute_map
       transformed_hash = {}
-      openapi_types.each_pair do |key, type|
-        if attributes.key?(attribute_map[key]) && attributes[attribute_map[key]].nil?
+      acceptable_openapi_types.each_pair do |key, type|
+        if attributes.key?(map[key]) && attributes[map[key]].nil?
           transformed_hash["#{key}"] = nil
         elsif type =~ /\AArray<(.*)>/i
           # check to ensure the input is an array given that the attribute
           # is documented as an array but the input is not
-          if attributes[attribute_map[key]].is_a?(Array)
-            transformed_hash["#{key}"] = attributes[attribute_map[key]].map { |v| _deserialize($1, v) }
+          if attributes[map[key]].is_a?(Array)
+            transformed_hash["#{key}"] = attributes[map[key]].map { |v| _deserialize($1, v) }
           end
-        elsif !attributes[attribute_map[key]].nil?
-          transformed_hash["#{key}"] = _deserialize(type, attributes[attribute_map[key]])
+        elsif !attributes[map[key]].nil?
+          transformed_hash["#{key}"] = _deserialize(type, attributes[map[key]])
         end
       end
       new(transformed_hash)
@@ -194,10 +206,11 @@ def self.build_from_hash(attributes)
     # @return [Hash] Returns the object in the form of hash
     def to_hash
       hash = {}
-      self.class.attribute_map.each_pair do |attr, param|
+      # include attributes inherited from allOf parents (the nearest declaration wins)
+      self.class.acceptable_attribute_map.each_pair do |attr, param|
         value = self.send(attr)
         if value.nil?
-          is_nullable = self.class.openapi_nullable.include?(attr)
+          is_nullable = self.class.acceptable_openapi_nullable.include?(attr)
           next if !is_nullable || (is_nullable && !instance_variable_defined?(:"@#{attr}"))
         end
 
diff --git a/samples/client/petstore/ruby-httpx/lib/petstore/models/whale.rb b/samples/client/petstore/ruby-httpx/lib/petstore/models/whale.rb
index 23249be434e4..f29de72ecb1a 100644
--- a/samples/client/petstore/ruby-httpx/lib/petstore/models/whale.rb
+++ b/samples/client/petstore/ruby-httpx/lib/petstore/models/whale.rb
@@ -55,6 +55,16 @@ def self.openapi_nullable
       ])
     end
 
+    # Returns attribute type mapping
+    def self.acceptable_openapi_types
+      openapi_types
+    end
+
+    # Returns the nullable attributes
+    def self.acceptable_openapi_nullable
+      openapi_nullable
+    end
+
     # Initializes the object
     # @param [Hash] attributes Model attributes in the form of hash
     def initialize(attributes = {})
@@ -144,18 +154,20 @@ def hash
     def self.build_from_hash(attributes)
       return nil unless attributes.is_a?(Hash)
       attributes = attributes.transform_keys(&:to_sym)
+      # include attributes inherited from allOf parents (the nearest declaration wins)
+      map = acceptable_attribute_map
       transformed_hash = {}
-      openapi_types.each_pair do |key, type|
-        if attributes.key?(attribute_map[key]) && attributes[attribute_map[key]].nil?
+      acceptable_openapi_types.each_pair do |key, type|
+        if attributes.key?(map[key]) && attributes[map[key]].nil?
           transformed_hash["#{key}"] = nil
         elsif type =~ /\AArray<(.*)>/i
           # check to ensure the input is an array given that the attribute
           # is documented as an array but the input is not
-          if attributes[attribute_map[key]].is_a?(Array)
-            transformed_hash["#{key}"] = attributes[attribute_map[key]].map { |v| _deserialize($1, v) }
+          if attributes[map[key]].is_a?(Array)
+            transformed_hash["#{key}"] = attributes[map[key]].map { |v| _deserialize($1, v) }
           end
-        elsif !attributes[attribute_map[key]].nil?
-          transformed_hash["#{key}"] = _deserialize(type, attributes[attribute_map[key]])
+        elsif !attributes[map[key]].nil?
+          transformed_hash["#{key}"] = _deserialize(type, attributes[map[key]])
         end
       end
       new(transformed_hash)
@@ -165,10 +177,11 @@ def self.build_from_hash(attributes)
     # @return [Hash] Returns the object in the form of hash
     def to_hash
       hash = {}
-      self.class.attribute_map.each_pair do |attr, param|
+      # include attributes inherited from allOf parents (the nearest declaration wins)
+      self.class.acceptable_attribute_map.each_pair do |attr, param|
         value = self.send(attr)
         if value.nil?
-          is_nullable = self.class.openapi_nullable.include?(attr)
+          is_nullable = self.class.acceptable_openapi_nullable.include?(attr)
           next if !is_nullable || (is_nullable && !instance_variable_defined?(:"@#{attr}"))
         end
 
diff --git a/samples/client/petstore/ruby-httpx/lib/petstore/models/zebra.rb b/samples/client/petstore/ruby-httpx/lib/petstore/models/zebra.rb
index 10e910f409f7..79771e498151 100644
--- a/samples/client/petstore/ruby-httpx/lib/petstore/models/zebra.rb
+++ b/samples/client/petstore/ruby-httpx/lib/petstore/models/zebra.rb
@@ -73,6 +73,16 @@ def self.openapi_nullable
       ])
     end
 
+    # Returns attribute type mapping
+    def self.acceptable_openapi_types
+      openapi_types
+    end
+
+    # Returns the nullable attributes
+    def self.acceptable_openapi_nullable
+      openapi_nullable
+    end
+
     # Initializes the object
     # @param [Hash] attributes Model attributes in the form of hash
     def initialize(attributes = {})
@@ -169,18 +179,20 @@ def hash
     def self.build_from_hash(attributes)
       return nil unless attributes.is_a?(Hash)
       attributes = attributes.transform_keys(&:to_sym)
+      # include attributes inherited from allOf parents (the nearest declaration wins)
+      map = acceptable_attribute_map
       transformed_hash = {}
-      openapi_types.each_pair do |key, type|
-        if attributes.key?(attribute_map[key]) && attributes[attribute_map[key]].nil?
+      acceptable_openapi_types.each_pair do |key, type|
+        if attributes.key?(map[key]) && attributes[map[key]].nil?
           transformed_hash["#{key}"] = nil
         elsif type =~ /\AArray<(.*)>/i
           # check to ensure the input is an array given that the attribute
           # is documented as an array but the input is not
-          if attributes[attribute_map[key]].is_a?(Array)
-            transformed_hash["#{key}"] = attributes[attribute_map[key]].map { |v| _deserialize($1, v) }
+          if attributes[map[key]].is_a?(Array)
+            transformed_hash["#{key}"] = attributes[map[key]].map { |v| _deserialize($1, v) }
           end
-        elsif !attributes[attribute_map[key]].nil?
-          transformed_hash["#{key}"] = _deserialize(type, attributes[attribute_map[key]])
+        elsif !attributes[map[key]].nil?
+          transformed_hash["#{key}"] = _deserialize(type, attributes[map[key]])
         end
       end
       new(transformed_hash)
@@ -190,10 +202,11 @@ def self.build_from_hash(attributes)
     # @return [Hash] Returns the object in the form of hash
     def to_hash
       hash = {}
-      self.class.attribute_map.each_pair do |attr, param|
+      # include attributes inherited from allOf parents (the nearest declaration wins)
+      self.class.acceptable_attribute_map.each_pair do |attr, param|
         value = self.send(attr)
         if value.nil?
-          is_nullable = self.class.openapi_nullable.include?(attr)
+          is_nullable = self.class.acceptable_openapi_nullable.include?(attr)
           next if !is_nullable || (is_nullable && !instance_variable_defined?(:"@#{attr}"))
         end
 
diff --git a/samples/client/petstore/ruby-httpx/spec/custom/base_object_spec.rb b/samples/client/petstore/ruby-httpx/spec/custom/base_object_spec.rb
index a046c5bd4e11..bc0ed63000b4 100644
--- a/samples/client/petstore/ruby-httpx/spec/custom/base_object_spec.rb
+++ b/samples/client/petstore/ruby-httpx/spec/custom/base_object_spec.rb
@@ -166,4 +166,34 @@ def initialize(attributes = {})
       expect(obj.to_hash).to eq(expect_data)
     end
   end
+
+  describe 'attributes inherited from an allOf parent' do
+    it 'build_from_hash and to_hash include the parent attributes' do
+      cat = Petstore::Cat.build_from_hash({ 'className' => 'Cat', 'color' => 'black', 'declawed' => true })
+
+      expect(cat).to be_instance_of(Petstore::Cat)
+      expect(cat.class_name).to eq('Cat')
+      expect(cat.color).to eq('black')
+      expect(cat.declawed).to eq(true)
+      expect(cat.to_hash).to eq({ className: 'Cat', color: 'black', declawed: true })
+    end
+
+    # passes on master too: guards that a subclass narrowing attribute_map is not handed its parent's attributes
+    it 'a subclass that narrows attribute_map is only handed the attributes it accepts' do
+      narrowed = Class.new(Petstore::Animal) do
+        def self.attribute_map
+          { :class_name => :className }
+        end
+
+        def self.openapi_types
+          { :class_name => :'String' }
+        end
+      end
+
+      obj = narrowed.build_from_hash({ 'className' => 'Cat', 'color' => 'black' })
+
+      expect(obj.class_name).to eq('Cat')
+      expect(obj.to_hash).to eq({ className: 'Cat' })
+    end
+  end
 end
diff --git a/samples/client/petstore/ruby/lib/petstore/models/additional_properties_class.rb b/samples/client/petstore/ruby/lib/petstore/models/additional_properties_class.rb
index 9b823593d156..a240cadf547e 100644
--- a/samples/client/petstore/ruby/lib/petstore/models/additional_properties_class.rb
+++ b/samples/client/petstore/ruby/lib/petstore/models/additional_properties_class.rb
@@ -51,6 +51,16 @@ def self.openapi_nullable
       ])
     end
 
+    # Returns attribute type mapping
+    def self.acceptable_openapi_types
+      openapi_types
+    end
+
+    # Returns the nullable attributes
+    def self.acceptable_openapi_nullable
+      openapi_nullable
+    end
+
     # Initializes the object
     # @param [Hash] attributes Model attributes in the form of hash
     def initialize(attributes = {})
@@ -122,18 +132,20 @@ def hash
     def self.build_from_hash(attributes)
       return nil unless attributes.is_a?(Hash)
       attributes = attributes.transform_keys(&:to_sym)
+      # include attributes inherited from allOf parents (the nearest declaration wins)
+      map = acceptable_attribute_map
       transformed_hash = {}
-      openapi_types.each_pair do |key, type|
-        if attributes.key?(attribute_map[key]) && attributes[attribute_map[key]].nil?
+      acceptable_openapi_types.each_pair do |key, type|
+        if attributes.key?(map[key]) && attributes[map[key]].nil?
           transformed_hash["#{key}"] = nil
         elsif type =~ /\AArray<(.*)>/i
           # check to ensure the input is an array given that the attribute
           # is documented as an array but the input is not
-          if attributes[attribute_map[key]].is_a?(Array)
-            transformed_hash["#{key}"] = attributes[attribute_map[key]].map { |v| _deserialize($1, v) }
+          if attributes[map[key]].is_a?(Array)
+            transformed_hash["#{key}"] = attributes[map[key]].map { |v| _deserialize($1, v) }
           end
-        elsif !attributes[attribute_map[key]].nil?
-          transformed_hash["#{key}"] = _deserialize(type, attributes[attribute_map[key]])
+        elsif !attributes[map[key]].nil?
+          transformed_hash["#{key}"] = _deserialize(type, attributes[map[key]])
         end
       end
       new(transformed_hash)
@@ -143,10 +155,11 @@ def self.build_from_hash(attributes)
     # @return [Hash] Returns the object in the form of hash
     def to_hash
       hash = {}
-      self.class.attribute_map.each_pair do |attr, param|
+      # include attributes inherited from allOf parents (the nearest declaration wins)
+      self.class.acceptable_attribute_map.each_pair do |attr, param|
         value = self.send(attr)
         if value.nil?
-          is_nullable = self.class.openapi_nullable.include?(attr)
+          is_nullable = self.class.acceptable_openapi_nullable.include?(attr)
           next if !is_nullable || (is_nullable && !instance_variable_defined?(:"@#{attr}"))
         end
 
diff --git a/samples/client/petstore/ruby/lib/petstore/models/all_of_with_single_ref.rb b/samples/client/petstore/ruby/lib/petstore/models/all_of_with_single_ref.rb
index 600c974fa1e5..9977e0212627 100644
--- a/samples/client/petstore/ruby/lib/petstore/models/all_of_with_single_ref.rb
+++ b/samples/client/petstore/ruby/lib/petstore/models/all_of_with_single_ref.rb
@@ -73,6 +73,16 @@ def self.openapi_nullable
       ])
     end
 
+    # Returns attribute type mapping
+    def self.acceptable_openapi_types
+      openapi_types
+    end
+
+    # Returns the nullable attributes
+    def self.acceptable_openapi_nullable
+      openapi_nullable
+    end
+
     # Initializes the object
     # @param [Hash] attributes Model attributes in the form of hash
     def initialize(attributes = {})
@@ -140,18 +150,20 @@ def hash
     def self.build_from_hash(attributes)
       return nil unless attributes.is_a?(Hash)
       attributes = attributes.transform_keys(&:to_sym)
+      # include attributes inherited from allOf parents (the nearest declaration wins)
+      map = acceptable_attribute_map
       transformed_hash = {}
-      openapi_types.each_pair do |key, type|
-        if attributes.key?(attribute_map[key]) && attributes[attribute_map[key]].nil?
+      acceptable_openapi_types.each_pair do |key, type|
+        if attributes.key?(map[key]) && attributes[map[key]].nil?
           transformed_hash["#{key}"] = nil
         elsif type =~ /\AArray<(.*)>/i
           # check to ensure the input is an array given that the attribute
           # is documented as an array but the input is not
-          if attributes[attribute_map[key]].is_a?(Array)
-            transformed_hash["#{key}"] = attributes[attribute_map[key]].map { |v| _deserialize($1, v) }
+          if attributes[map[key]].is_a?(Array)
+            transformed_hash["#{key}"] = attributes[map[key]].map { |v| _deserialize($1, v) }
           end
-        elsif !attributes[attribute_map[key]].nil?
-          transformed_hash["#{key}"] = _deserialize(type, attributes[attribute_map[key]])
+        elsif !attributes[map[key]].nil?
+          transformed_hash["#{key}"] = _deserialize(type, attributes[map[key]])
         end
       end
       new(transformed_hash)
@@ -161,10 +173,11 @@ def self.build_from_hash(attributes)
     # @return [Hash] Returns the object in the form of hash
     def to_hash
       hash = {}
-      self.class.attribute_map.each_pair do |attr, param|
+      # include attributes inherited from allOf parents (the nearest declaration wins)
+      self.class.acceptable_attribute_map.each_pair do |attr, param|
         value = self.send(attr)
         if value.nil?
-          is_nullable = self.class.openapi_nullable.include?(attr)
+          is_nullable = self.class.acceptable_openapi_nullable.include?(attr)
           next if !is_nullable || (is_nullable && !instance_variable_defined?(:"@#{attr}"))
         end
 
diff --git a/samples/client/petstore/ruby/lib/petstore/models/animal.rb b/samples/client/petstore/ruby/lib/petstore/models/animal.rb
index 21d89bccb837..b58dbb506d4e 100644
--- a/samples/client/petstore/ruby/lib/petstore/models/animal.rb
+++ b/samples/client/petstore/ruby/lib/petstore/models/animal.rb
@@ -51,6 +51,16 @@ def self.openapi_nullable
       ])
     end
 
+    # Returns attribute type mapping
+    def self.acceptable_openapi_types
+      openapi_types
+    end
+
+    # Returns the nullable attributes
+    def self.acceptable_openapi_nullable
+      openapi_nullable
+    end
+
     # discriminator's property name in OpenAPI v3
     def self.openapi_discriminator_name
       :'class_name'
@@ -142,18 +152,20 @@ def hash
     def self.build_from_hash(attributes)
       return nil unless attributes.is_a?(Hash)
       attributes = attributes.transform_keys(&:to_sym)
+      # include attributes inherited from allOf parents (the nearest declaration wins)
+      map = acceptable_attribute_map
       transformed_hash = {}
-      openapi_types.each_pair do |key, type|
-        if attributes.key?(attribute_map[key]) && attributes[attribute_map[key]].nil?
+      acceptable_openapi_types.each_pair do |key, type|
+        if attributes.key?(map[key]) && attributes[map[key]].nil?
           transformed_hash["#{key}"] = nil
         elsif type =~ /\AArray<(.*)>/i
           # check to ensure the input is an array given that the attribute
           # is documented as an array but the input is not
-          if attributes[attribute_map[key]].is_a?(Array)
-            transformed_hash["#{key}"] = attributes[attribute_map[key]].map { |v| _deserialize($1, v) }
+          if attributes[map[key]].is_a?(Array)
+            transformed_hash["#{key}"] = attributes[map[key]].map { |v| _deserialize($1, v) }
           end
-        elsif !attributes[attribute_map[key]].nil?
-          transformed_hash["#{key}"] = _deserialize(type, attributes[attribute_map[key]])
+        elsif !attributes[map[key]].nil?
+          transformed_hash["#{key}"] = _deserialize(type, attributes[map[key]])
         end
       end
       new(transformed_hash)
@@ -163,10 +175,11 @@ def self.build_from_hash(attributes)
     # @return [Hash] Returns the object in the form of hash
     def to_hash
       hash = {}
-      self.class.attribute_map.each_pair do |attr, param|
+      # include attributes inherited from allOf parents (the nearest declaration wins)
+      self.class.acceptable_attribute_map.each_pair do |attr, param|
         value = self.send(attr)
         if value.nil?
-          is_nullable = self.class.openapi_nullable.include?(attr)
+          is_nullable = self.class.acceptable_openapi_nullable.include?(attr)
           next if !is_nullable || (is_nullable && !instance_variable_defined?(:"@#{attr}"))
         end
 
diff --git a/samples/client/petstore/ruby/lib/petstore/models/api_response.rb b/samples/client/petstore/ruby/lib/petstore/models/api_response.rb
index bbbaf9358be2..6b8e2bf4005f 100644
--- a/samples/client/petstore/ruby/lib/petstore/models/api_response.rb
+++ b/samples/client/petstore/ruby/lib/petstore/models/api_response.rb
@@ -55,6 +55,16 @@ def self.openapi_nullable
       ])
     end
 
+    # Returns attribute type mapping
+    def self.acceptable_openapi_types
+      openapi_types
+    end
+
+    # Returns the nullable attributes
+    def self.acceptable_openapi_nullable
+      openapi_nullable
+    end
+
     # Initializes the object
     # @param [Hash] attributes Model attributes in the form of hash
     def initialize(attributes = {})
@@ -127,18 +137,20 @@ def hash
     def self.build_from_hash(attributes)
       return nil unless attributes.is_a?(Hash)
       attributes = attributes.transform_keys(&:to_sym)
+      # include attributes inherited from allOf parents (the nearest declaration wins)
+      map = acceptable_attribute_map
       transformed_hash = {}
-      openapi_types.each_pair do |key, type|
-        if attributes.key?(attribute_map[key]) && attributes[attribute_map[key]].nil?
+      acceptable_openapi_types.each_pair do |key, type|
+        if attributes.key?(map[key]) && attributes[map[key]].nil?
           transformed_hash["#{key}"] = nil
         elsif type =~ /\AArray<(.*)>/i
           # check to ensure the input is an array given that the attribute
           # is documented as an array but the input is not
-          if attributes[attribute_map[key]].is_a?(Array)
-            transformed_hash["#{key}"] = attributes[attribute_map[key]].map { |v| _deserialize($1, v) }
+          if attributes[map[key]].is_a?(Array)
+            transformed_hash["#{key}"] = attributes[map[key]].map { |v| _deserialize($1, v) }
           end
-        elsif !attributes[attribute_map[key]].nil?
-          transformed_hash["#{key}"] = _deserialize(type, attributes[attribute_map[key]])
+        elsif !attributes[map[key]].nil?
+          transformed_hash["#{key}"] = _deserialize(type, attributes[map[key]])
         end
       end
       new(transformed_hash)
@@ -148,10 +160,11 @@ def self.build_from_hash(attributes)
     # @return [Hash] Returns the object in the form of hash
     def to_hash
       hash = {}
-      self.class.attribute_map.each_pair do |attr, param|
+      # include attributes inherited from allOf parents (the nearest declaration wins)
+      self.class.acceptable_attribute_map.each_pair do |attr, param|
         value = self.send(attr)
         if value.nil?
-          is_nullable = self.class.openapi_nullable.include?(attr)
+          is_nullable = self.class.acceptable_openapi_nullable.include?(attr)
           next if !is_nullable || (is_nullable && !instance_variable_defined?(:"@#{attr}"))
         end
 
diff --git a/samples/client/petstore/ruby/lib/petstore/models/array_of_array_of_number_only.rb b/samples/client/petstore/ruby/lib/petstore/models/array_of_array_of_number_only.rb
index e20b1728d130..40b968094257 100644
--- a/samples/client/petstore/ruby/lib/petstore/models/array_of_array_of_number_only.rb
+++ b/samples/client/petstore/ruby/lib/petstore/models/array_of_array_of_number_only.rb
@@ -47,6 +47,16 @@ def self.openapi_nullable
       ])
     end
 
+    # Returns attribute type mapping
+    def self.acceptable_openapi_types
+      openapi_types
+    end
+
+    # Returns the nullable attributes
+    def self.acceptable_openapi_nullable
+      openapi_nullable
+    end
+
     # Initializes the object
     # @param [Hash] attributes Model attributes in the form of hash
     def initialize(attributes = {})
@@ -111,18 +121,20 @@ def hash
     def self.build_from_hash(attributes)
       return nil unless attributes.is_a?(Hash)
       attributes = attributes.transform_keys(&:to_sym)
+      # include attributes inherited from allOf parents (the nearest declaration wins)
+      map = acceptable_attribute_map
       transformed_hash = {}
-      openapi_types.each_pair do |key, type|
-        if attributes.key?(attribute_map[key]) && attributes[attribute_map[key]].nil?
+      acceptable_openapi_types.each_pair do |key, type|
+        if attributes.key?(map[key]) && attributes[map[key]].nil?
           transformed_hash["#{key}"] = nil
         elsif type =~ /\AArray<(.*)>/i
           # check to ensure the input is an array given that the attribute
           # is documented as an array but the input is not
-          if attributes[attribute_map[key]].is_a?(Array)
-            transformed_hash["#{key}"] = attributes[attribute_map[key]].map { |v| _deserialize($1, v) }
+          if attributes[map[key]].is_a?(Array)
+            transformed_hash["#{key}"] = attributes[map[key]].map { |v| _deserialize($1, v) }
           end
-        elsif !attributes[attribute_map[key]].nil?
-          transformed_hash["#{key}"] = _deserialize(type, attributes[attribute_map[key]])
+        elsif !attributes[map[key]].nil?
+          transformed_hash["#{key}"] = _deserialize(type, attributes[map[key]])
         end
       end
       new(transformed_hash)
@@ -132,10 +144,11 @@ def self.build_from_hash(attributes)
     # @return [Hash] Returns the object in the form of hash
     def to_hash
       hash = {}
-      self.class.attribute_map.each_pair do |attr, param|
+      # include attributes inherited from allOf parents (the nearest declaration wins)
+      self.class.acceptable_attribute_map.each_pair do |attr, param|
         value = self.send(attr)
         if value.nil?
-          is_nullable = self.class.openapi_nullable.include?(attr)
+          is_nullable = self.class.acceptable_openapi_nullable.include?(attr)
           next if !is_nullable || (is_nullable && !instance_variable_defined?(:"@#{attr}"))
         end
 
diff --git a/samples/client/petstore/ruby/lib/petstore/models/array_of_number_only.rb b/samples/client/petstore/ruby/lib/petstore/models/array_of_number_only.rb
index 63890ff64424..6b9bc3627785 100644
--- a/samples/client/petstore/ruby/lib/petstore/models/array_of_number_only.rb
+++ b/samples/client/petstore/ruby/lib/petstore/models/array_of_number_only.rb
@@ -47,6 +47,16 @@ def self.openapi_nullable
       ])
     end
 
+    # Returns attribute type mapping
+    def self.acceptable_openapi_types
+      openapi_types
+    end
+
+    # Returns the nullable attributes
+    def self.acceptable_openapi_nullable
+      openapi_nullable
+    end
+
     # Initializes the object
     # @param [Hash] attributes Model attributes in the form of hash
     def initialize(attributes = {})
@@ -111,18 +121,20 @@ def hash
     def self.build_from_hash(attributes)
       return nil unless attributes.is_a?(Hash)
       attributes = attributes.transform_keys(&:to_sym)
+      # include attributes inherited from allOf parents (the nearest declaration wins)
+      map = acceptable_attribute_map
       transformed_hash = {}
-      openapi_types.each_pair do |key, type|
-        if attributes.key?(attribute_map[key]) && attributes[attribute_map[key]].nil?
+      acceptable_openapi_types.each_pair do |key, type|
+        if attributes.key?(map[key]) && attributes[map[key]].nil?
           transformed_hash["#{key}"] = nil
         elsif type =~ /\AArray<(.*)>/i
           # check to ensure the input is an array given that the attribute
           # is documented as an array but the input is not
-          if attributes[attribute_map[key]].is_a?(Array)
-            transformed_hash["#{key}"] = attributes[attribute_map[key]].map { |v| _deserialize($1, v) }
+          if attributes[map[key]].is_a?(Array)
+            transformed_hash["#{key}"] = attributes[map[key]].map { |v| _deserialize($1, v) }
           end
-        elsif !attributes[attribute_map[key]].nil?
-          transformed_hash["#{key}"] = _deserialize(type, attributes[attribute_map[key]])
+        elsif !attributes[map[key]].nil?
+          transformed_hash["#{key}"] = _deserialize(type, attributes[map[key]])
         end
       end
       new(transformed_hash)
@@ -132,10 +144,11 @@ def self.build_from_hash(attributes)
     # @return [Hash] Returns the object in the form of hash
     def to_hash
       hash = {}
-      self.class.attribute_map.each_pair do |attr, param|
+      # include attributes inherited from allOf parents (the nearest declaration wins)
+      self.class.acceptable_attribute_map.each_pair do |attr, param|
         value = self.send(attr)
         if value.nil?
-          is_nullable = self.class.openapi_nullable.include?(attr)
+          is_nullable = self.class.acceptable_openapi_nullable.include?(attr)
           next if !is_nullable || (is_nullable && !instance_variable_defined?(:"@#{attr}"))
         end
 
diff --git a/samples/client/petstore/ruby/lib/petstore/models/array_test.rb b/samples/client/petstore/ruby/lib/petstore/models/array_test.rb
index c74060151e07..fc5e9d297766 100644
--- a/samples/client/petstore/ruby/lib/petstore/models/array_test.rb
+++ b/samples/client/petstore/ruby/lib/petstore/models/array_test.rb
@@ -55,6 +55,16 @@ def self.openapi_nullable
       ])
     end
 
+    # Returns attribute type mapping
+    def self.acceptable_openapi_types
+      openapi_types
+    end
+
+    # Returns the nullable attributes
+    def self.acceptable_openapi_nullable
+      openapi_nullable
+    end
+
     # Initializes the object
     # @param [Hash] attributes Model attributes in the form of hash
     def initialize(attributes = {})
@@ -161,18 +171,20 @@ def hash
     def self.build_from_hash(attributes)
       return nil unless attributes.is_a?(Hash)
       attributes = attributes.transform_keys(&:to_sym)
+      # include attributes inherited from allOf parents (the nearest declaration wins)
+      map = acceptable_attribute_map
       transformed_hash = {}
-      openapi_types.each_pair do |key, type|
-        if attributes.key?(attribute_map[key]) && attributes[attribute_map[key]].nil?
+      acceptable_openapi_types.each_pair do |key, type|
+        if attributes.key?(map[key]) && attributes[map[key]].nil?
           transformed_hash["#{key}"] = nil
         elsif type =~ /\AArray<(.*)>/i
           # check to ensure the input is an array given that the attribute
           # is documented as an array but the input is not
-          if attributes[attribute_map[key]].is_a?(Array)
-            transformed_hash["#{key}"] = attributes[attribute_map[key]].map { |v| _deserialize($1, v) }
+          if attributes[map[key]].is_a?(Array)
+            transformed_hash["#{key}"] = attributes[map[key]].map { |v| _deserialize($1, v) }
           end
-        elsif !attributes[attribute_map[key]].nil?
-          transformed_hash["#{key}"] = _deserialize(type, attributes[attribute_map[key]])
+        elsif !attributes[map[key]].nil?
+          transformed_hash["#{key}"] = _deserialize(type, attributes[map[key]])
         end
       end
       new(transformed_hash)
@@ -182,10 +194,11 @@ def self.build_from_hash(attributes)
     # @return [Hash] Returns the object in the form of hash
     def to_hash
       hash = {}
-      self.class.attribute_map.each_pair do |attr, param|
+      # include attributes inherited from allOf parents (the nearest declaration wins)
+      self.class.acceptable_attribute_map.each_pair do |attr, param|
         value = self.send(attr)
         if value.nil?
-          is_nullable = self.class.openapi_nullable.include?(attr)
+          is_nullable = self.class.acceptable_openapi_nullable.include?(attr)
           next if !is_nullable || (is_nullable && !instance_variable_defined?(:"@#{attr}"))
         end
 
diff --git a/samples/client/petstore/ruby/lib/petstore/models/capitalization.rb b/samples/client/petstore/ruby/lib/petstore/models/capitalization.rb
index e0bbeb211eb3..9031ca3f7d51 100644
--- a/samples/client/petstore/ruby/lib/petstore/models/capitalization.rb
+++ b/samples/client/petstore/ruby/lib/petstore/models/capitalization.rb
@@ -68,6 +68,16 @@ def self.openapi_nullable
       ])
     end
 
+    # Returns attribute type mapping
+    def self.acceptable_openapi_types
+      openapi_types
+    end
+
+    # Returns the nullable attributes
+    def self.acceptable_openapi_nullable
+      openapi_nullable
+    end
+
     # Initializes the object
     # @param [Hash] attributes Model attributes in the form of hash
     def initialize(attributes = {})
@@ -155,18 +165,20 @@ def hash
     def self.build_from_hash(attributes)
       return nil unless attributes.is_a?(Hash)
       attributes = attributes.transform_keys(&:to_sym)
+      # include attributes inherited from allOf parents (the nearest declaration wins)
+      map = acceptable_attribute_map
       transformed_hash = {}
-      openapi_types.each_pair do |key, type|
-        if attributes.key?(attribute_map[key]) && attributes[attribute_map[key]].nil?
+      acceptable_openapi_types.each_pair do |key, type|
+        if attributes.key?(map[key]) && attributes[map[key]].nil?
           transformed_hash["#{key}"] = nil
         elsif type =~ /\AArray<(.*)>/i
           # check to ensure the input is an array given that the attribute
           # is documented as an array but the input is not
-          if attributes[attribute_map[key]].is_a?(Array)
-            transformed_hash["#{key}"] = attributes[attribute_map[key]].map { |v| _deserialize($1, v) }
+          if attributes[map[key]].is_a?(Array)
+            transformed_hash["#{key}"] = attributes[map[key]].map { |v| _deserialize($1, v) }
           end
-        elsif !attributes[attribute_map[key]].nil?
-          transformed_hash["#{key}"] = _deserialize(type, attributes[attribute_map[key]])
+        elsif !attributes[map[key]].nil?
+          transformed_hash["#{key}"] = _deserialize(type, attributes[map[key]])
         end
       end
       new(transformed_hash)
@@ -176,10 +188,11 @@ def self.build_from_hash(attributes)
     # @return [Hash] Returns the object in the form of hash
     def to_hash
       hash = {}
-      self.class.attribute_map.each_pair do |attr, param|
+      # include attributes inherited from allOf parents (the nearest declaration wins)
+      self.class.acceptable_attribute_map.each_pair do |attr, param|
         value = self.send(attr)
         if value.nil?
-          is_nullable = self.class.openapi_nullable.include?(attr)
+          is_nullable = self.class.acceptable_openapi_nullable.include?(attr)
           next if !is_nullable || (is_nullable && !instance_variable_defined?(:"@#{attr}"))
         end
 
diff --git a/samples/client/petstore/ruby/lib/petstore/models/cat.rb b/samples/client/petstore/ruby/lib/petstore/models/cat.rb
index a84dc5038bef..a1f3de5272b6 100644
--- a/samples/client/petstore/ruby/lib/petstore/models/cat.rb
+++ b/samples/client/petstore/ruby/lib/petstore/models/cat.rb
@@ -47,6 +47,16 @@ def self.openapi_nullable
       ])
     end
 
+    # Returns attribute type mapping, including the ones defined in its parent(s)
+    def self.acceptable_openapi_types
+      superclass.acceptable_openapi_types.merge(openapi_types)
+    end
+
+    # Returns the nullable attributes, including the ones defined in its parent(s) that it does not redeclare
+    def self.acceptable_openapi_nullable
+      (superclass.acceptable_openapi_nullable - attribute_map.keys) | openapi_nullable
+    end
+
     # List of class defined in allOf (OpenAPI v3)
     def self.openapi_all_of
       [
@@ -118,20 +128,21 @@ def hash
     # @return [Object] Returns the model itself
     def self.build_from_hash(attributes)
       return nil unless attributes.is_a?(Hash)
-      super(attributes)
       attributes = attributes.transform_keys(&:to_sym)
+      # include attributes inherited from allOf parents (the nearest declaration wins)
+      map = acceptable_attribute_map
       transformed_hash = {}
-      openapi_types.each_pair do |key, type|
-        if attributes.key?(attribute_map[key]) && attributes[attribute_map[key]].nil?
+      acceptable_openapi_types.each_pair do |key, type|
+        if attributes.key?(map[key]) && attributes[map[key]].nil?
           transformed_hash["#{key}"] = nil
         elsif type =~ /\AArray<(.*)>/i
           # check to ensure the input is an array given that the attribute
           # is documented as an array but the input is not
-          if attributes[attribute_map[key]].is_a?(Array)
-            transformed_hash["#{key}"] = attributes[attribute_map[key]].map { |v| _deserialize($1, v) }
+          if attributes[map[key]].is_a?(Array)
+            transformed_hash["#{key}"] = attributes[map[key]].map { |v| _deserialize($1, v) }
           end
-        elsif !attributes[attribute_map[key]].nil?
-          transformed_hash["#{key}"] = _deserialize(type, attributes[attribute_map[key]])
+        elsif !attributes[map[key]].nil?
+          transformed_hash["#{key}"] = _deserialize(type, attributes[map[key]])
         end
       end
       new(transformed_hash)
@@ -140,11 +151,12 @@ def self.build_from_hash(attributes)
     # Returns the object in the form of hash
     # @return [Hash] Returns the object in the form of hash
     def to_hash
-      hash = super
-      self.class.attribute_map.each_pair do |attr, param|
+      hash = {}
+      # include attributes inherited from allOf parents (the nearest declaration wins)
+      self.class.acceptable_attribute_map.each_pair do |attr, param|
         value = self.send(attr)
         if value.nil?
-          is_nullable = self.class.openapi_nullable.include?(attr)
+          is_nullable = self.class.acceptable_openapi_nullable.include?(attr)
           next if !is_nullable || (is_nullable && !instance_variable_defined?(:"@#{attr}"))
         end
 
diff --git a/samples/client/petstore/ruby/lib/petstore/models/category.rb b/samples/client/petstore/ruby/lib/petstore/models/category.rb
index 2f2b7f1a5785..a5af1c3f9acc 100644
--- a/samples/client/petstore/ruby/lib/petstore/models/category.rb
+++ b/samples/client/petstore/ruby/lib/petstore/models/category.rb
@@ -51,6 +51,16 @@ def self.openapi_nullable
       ])
     end
 
+    # Returns attribute type mapping
+    def self.acceptable_openapi_types
+      openapi_types
+    end
+
+    # Returns the nullable attributes
+    def self.acceptable_openapi_nullable
+      openapi_nullable
+    end
+
     # Initializes the object
     # @param [Hash] attributes Model attributes in the form of hash
     def initialize(attributes = {})
@@ -135,18 +145,20 @@ def hash
     def self.build_from_hash(attributes)
       return nil unless attributes.is_a?(Hash)
       attributes = attributes.transform_keys(&:to_sym)
+      # include attributes inherited from allOf parents (the nearest declaration wins)
+      map = acceptable_attribute_map
       transformed_hash = {}
-      openapi_types.each_pair do |key, type|
-        if attributes.key?(attribute_map[key]) && attributes[attribute_map[key]].nil?
+      acceptable_openapi_types.each_pair do |key, type|
+        if attributes.key?(map[key]) && attributes[map[key]].nil?
           transformed_hash["#{key}"] = nil
         elsif type =~ /\AArray<(.*)>/i
           # check to ensure the input is an array given that the attribute
           # is documented as an array but the input is not
-          if attributes[attribute_map[key]].is_a?(Array)
-            transformed_hash["#{key}"] = attributes[attribute_map[key]].map { |v| _deserialize($1, v) }
+          if attributes[map[key]].is_a?(Array)
+            transformed_hash["#{key}"] = attributes[map[key]].map { |v| _deserialize($1, v) }
           end
-        elsif !attributes[attribute_map[key]].nil?
-          transformed_hash["#{key}"] = _deserialize(type, attributes[attribute_map[key]])
+        elsif !attributes[map[key]].nil?
+          transformed_hash["#{key}"] = _deserialize(type, attributes[map[key]])
         end
       end
       new(transformed_hash)
@@ -156,10 +168,11 @@ def self.build_from_hash(attributes)
     # @return [Hash] Returns the object in the form of hash
     def to_hash
       hash = {}
-      self.class.attribute_map.each_pair do |attr, param|
+      # include attributes inherited from allOf parents (the nearest declaration wins)
+      self.class.acceptable_attribute_map.each_pair do |attr, param|
         value = self.send(attr)
         if value.nil?
-          is_nullable = self.class.openapi_nullable.include?(attr)
+          is_nullable = self.class.acceptable_openapi_nullable.include?(attr)
           next if !is_nullable || (is_nullable && !instance_variable_defined?(:"@#{attr}"))
         end
 
diff --git a/samples/client/petstore/ruby/lib/petstore/models/class_model.rb b/samples/client/petstore/ruby/lib/petstore/models/class_model.rb
index fafd11df773a..4e611ee27f3e 100644
--- a/samples/client/petstore/ruby/lib/petstore/models/class_model.rb
+++ b/samples/client/petstore/ruby/lib/petstore/models/class_model.rb
@@ -48,6 +48,16 @@ def self.openapi_nullable
       ])
     end
 
+    # Returns attribute type mapping
+    def self.acceptable_openapi_types
+      openapi_types
+    end
+
+    # Returns the nullable attributes
+    def self.acceptable_openapi_nullable
+      openapi_nullable
+    end
+
     # Initializes the object
     # @param [Hash] attributes Model attributes in the form of hash
     def initialize(attributes = {})
@@ -110,18 +120,20 @@ def hash
     def self.build_from_hash(attributes)
       return nil unless attributes.is_a?(Hash)
       attributes = attributes.transform_keys(&:to_sym)
+      # include attributes inherited from allOf parents (the nearest declaration wins)
+      map = acceptable_attribute_map
       transformed_hash = {}
-      openapi_types.each_pair do |key, type|
-        if attributes.key?(attribute_map[key]) && attributes[attribute_map[key]].nil?
+      acceptable_openapi_types.each_pair do |key, type|
+        if attributes.key?(map[key]) && attributes[map[key]].nil?
           transformed_hash["#{key}"] = nil
         elsif type =~ /\AArray<(.*)>/i
           # check to ensure the input is an array given that the attribute
           # is documented as an array but the input is not
-          if attributes[attribute_map[key]].is_a?(Array)
-            transformed_hash["#{key}"] = attributes[attribute_map[key]].map { |v| _deserialize($1, v) }
+          if attributes[map[key]].is_a?(Array)
+            transformed_hash["#{key}"] = attributes[map[key]].map { |v| _deserialize($1, v) }
           end
-        elsif !attributes[attribute_map[key]].nil?
-          transformed_hash["#{key}"] = _deserialize(type, attributes[attribute_map[key]])
+        elsif !attributes[map[key]].nil?
+          transformed_hash["#{key}"] = _deserialize(type, attributes[map[key]])
         end
       end
       new(transformed_hash)
@@ -131,10 +143,11 @@ def self.build_from_hash(attributes)
     # @return [Hash] Returns the object in the form of hash
     def to_hash
       hash = {}
-      self.class.attribute_map.each_pair do |attr, param|
+      # include attributes inherited from allOf parents (the nearest declaration wins)
+      self.class.acceptable_attribute_map.each_pair do |attr, param|
         value = self.send(attr)
         if value.nil?
-          is_nullable = self.class.openapi_nullable.include?(attr)
+          is_nullable = self.class.acceptable_openapi_nullable.include?(attr)
           next if !is_nullable || (is_nullable && !instance_variable_defined?(:"@#{attr}"))
         end
 
diff --git a/samples/client/petstore/ruby/lib/petstore/models/client.rb b/samples/client/petstore/ruby/lib/petstore/models/client.rb
index a349b7251d7b..f775d0f1d542 100644
--- a/samples/client/petstore/ruby/lib/petstore/models/client.rb
+++ b/samples/client/petstore/ruby/lib/petstore/models/client.rb
@@ -47,6 +47,16 @@ def self.openapi_nullable
       ])
     end
 
+    # Returns attribute type mapping
+    def self.acceptable_openapi_types
+      openapi_types
+    end
+
+    # Returns the nullable attributes
+    def self.acceptable_openapi_nullable
+      openapi_nullable
+    end
+
     # Initializes the object
     # @param [Hash] attributes Model attributes in the form of hash
     def initialize(attributes = {})
@@ -109,18 +119,20 @@ def hash
     def self.build_from_hash(attributes)
       return nil unless attributes.is_a?(Hash)
       attributes = attributes.transform_keys(&:to_sym)
+      # include attributes inherited from allOf parents (the nearest declaration wins)
+      map = acceptable_attribute_map
       transformed_hash = {}
-      openapi_types.each_pair do |key, type|
-        if attributes.key?(attribute_map[key]) && attributes[attribute_map[key]].nil?
+      acceptable_openapi_types.each_pair do |key, type|
+        if attributes.key?(map[key]) && attributes[map[key]].nil?
           transformed_hash["#{key}"] = nil
         elsif type =~ /\AArray<(.*)>/i
           # check to ensure the input is an array given that the attribute
           # is documented as an array but the input is not
-          if attributes[attribute_map[key]].is_a?(Array)
-            transformed_hash["#{key}"] = attributes[attribute_map[key]].map { |v| _deserialize($1, v) }
+          if attributes[map[key]].is_a?(Array)
+            transformed_hash["#{key}"] = attributes[map[key]].map { |v| _deserialize($1, v) }
           end
-        elsif !attributes[attribute_map[key]].nil?
-          transformed_hash["#{key}"] = _deserialize(type, attributes[attribute_map[key]])
+        elsif !attributes[map[key]].nil?
+          transformed_hash["#{key}"] = _deserialize(type, attributes[map[key]])
         end
       end
       new(transformed_hash)
@@ -130,10 +142,11 @@ def self.build_from_hash(attributes)
     # @return [Hash] Returns the object in the form of hash
     def to_hash
       hash = {}
-      self.class.attribute_map.each_pair do |attr, param|
+      # include attributes inherited from allOf parents (the nearest declaration wins)
+      self.class.acceptable_attribute_map.each_pair do |attr, param|
         value = self.send(attr)
         if value.nil?
-          is_nullable = self.class.openapi_nullable.include?(attr)
+          is_nullable = self.class.acceptable_openapi_nullable.include?(attr)
           next if !is_nullable || (is_nullable && !instance_variable_defined?(:"@#{attr}"))
         end
 
diff --git a/samples/client/petstore/ruby/lib/petstore/models/deprecated_object.rb b/samples/client/petstore/ruby/lib/petstore/models/deprecated_object.rb
index 9f1ee6720cab..bdc86013c848 100644
--- a/samples/client/petstore/ruby/lib/petstore/models/deprecated_object.rb
+++ b/samples/client/petstore/ruby/lib/petstore/models/deprecated_object.rb
@@ -47,6 +47,16 @@ def self.openapi_nullable
       ])
     end
 
+    # Returns attribute type mapping
+    def self.acceptable_openapi_types
+      openapi_types
+    end
+
+    # Returns the nullable attributes
+    def self.acceptable_openapi_nullable
+      openapi_nullable
+    end
+
     # Initializes the object
     # @param [Hash] attributes Model attributes in the form of hash
     def initialize(attributes = {})
@@ -109,18 +119,20 @@ def hash
     def self.build_from_hash(attributes)
       return nil unless attributes.is_a?(Hash)
       attributes = attributes.transform_keys(&:to_sym)
+      # include attributes inherited from allOf parents (the nearest declaration wins)
+      map = acceptable_attribute_map
       transformed_hash = {}
-      openapi_types.each_pair do |key, type|
-        if attributes.key?(attribute_map[key]) && attributes[attribute_map[key]].nil?
+      acceptable_openapi_types.each_pair do |key, type|
+        if attributes.key?(map[key]) && attributes[map[key]].nil?
           transformed_hash["#{key}"] = nil
         elsif type =~ /\AArray<(.*)>/i
           # check to ensure the input is an array given that the attribute
           # is documented as an array but the input is not
-          if attributes[attribute_map[key]].is_a?(Array)
-            transformed_hash["#{key}"] = attributes[attribute_map[key]].map { |v| _deserialize($1, v) }
+          if attributes[map[key]].is_a?(Array)
+            transformed_hash["#{key}"] = attributes[map[key]].map { |v| _deserialize($1, v) }
           end
-        elsif !attributes[attribute_map[key]].nil?
-          transformed_hash["#{key}"] = _deserialize(type, attributes[attribute_map[key]])
+        elsif !attributes[map[key]].nil?
+          transformed_hash["#{key}"] = _deserialize(type, attributes[map[key]])
         end
       end
       new(transformed_hash)
@@ -130,10 +142,11 @@ def self.build_from_hash(attributes)
     # @return [Hash] Returns the object in the form of hash
     def to_hash
       hash = {}
-      self.class.attribute_map.each_pair do |attr, param|
+      # include attributes inherited from allOf parents (the nearest declaration wins)
+      self.class.acceptable_attribute_map.each_pair do |attr, param|
         value = self.send(attr)
         if value.nil?
-          is_nullable = self.class.openapi_nullable.include?(attr)
+          is_nullable = self.class.acceptable_openapi_nullable.include?(attr)
           next if !is_nullable || (is_nullable && !instance_variable_defined?(:"@#{attr}"))
         end
 
diff --git a/samples/client/petstore/ruby/lib/petstore/models/dog.rb b/samples/client/petstore/ruby/lib/petstore/models/dog.rb
index 522e1a72f47e..2e8f95136f9a 100644
--- a/samples/client/petstore/ruby/lib/petstore/models/dog.rb
+++ b/samples/client/petstore/ruby/lib/petstore/models/dog.rb
@@ -47,6 +47,16 @@ def self.openapi_nullable
       ])
     end
 
+    # Returns attribute type mapping, including the ones defined in its parent(s)
+    def self.acceptable_openapi_types
+      superclass.acceptable_openapi_types.merge(openapi_types)
+    end
+
+    # Returns the nullable attributes, including the ones defined in its parent(s) that it does not redeclare
+    def self.acceptable_openapi_nullable
+      (superclass.acceptable_openapi_nullable - attribute_map.keys) | openapi_nullable
+    end
+
     # List of class defined in allOf (OpenAPI v3)
     def self.openapi_all_of
       [
@@ -118,20 +128,21 @@ def hash
     # @return [Object] Returns the model itself
     def self.build_from_hash(attributes)
       return nil unless attributes.is_a?(Hash)
-      super(attributes)
       attributes = attributes.transform_keys(&:to_sym)
+      # include attributes inherited from allOf parents (the nearest declaration wins)
+      map = acceptable_attribute_map
       transformed_hash = {}
-      openapi_types.each_pair do |key, type|
-        if attributes.key?(attribute_map[key]) && attributes[attribute_map[key]].nil?
+      acceptable_openapi_types.each_pair do |key, type|
+        if attributes.key?(map[key]) && attributes[map[key]].nil?
           transformed_hash["#{key}"] = nil
         elsif type =~ /\AArray<(.*)>/i
           # check to ensure the input is an array given that the attribute
           # is documented as an array but the input is not
-          if attributes[attribute_map[key]].is_a?(Array)
-            transformed_hash["#{key}"] = attributes[attribute_map[key]].map { |v| _deserialize($1, v) }
+          if attributes[map[key]].is_a?(Array)
+            transformed_hash["#{key}"] = attributes[map[key]].map { |v| _deserialize($1, v) }
           end
-        elsif !attributes[attribute_map[key]].nil?
-          transformed_hash["#{key}"] = _deserialize(type, attributes[attribute_map[key]])
+        elsif !attributes[map[key]].nil?
+          transformed_hash["#{key}"] = _deserialize(type, attributes[map[key]])
         end
       end
       new(transformed_hash)
@@ -140,11 +151,12 @@ def self.build_from_hash(attributes)
     # Returns the object in the form of hash
     # @return [Hash] Returns the object in the form of hash
     def to_hash
-      hash = super
-      self.class.attribute_map.each_pair do |attr, param|
+      hash = {}
+      # include attributes inherited from allOf parents (the nearest declaration wins)
+      self.class.acceptable_attribute_map.each_pair do |attr, param|
         value = self.send(attr)
         if value.nil?
-          is_nullable = self.class.openapi_nullable.include?(attr)
+          is_nullable = self.class.acceptable_openapi_nullable.include?(attr)
           next if !is_nullable || (is_nullable && !instance_variable_defined?(:"@#{attr}"))
         end
 
diff --git a/samples/client/petstore/ruby/lib/petstore/models/enum_arrays.rb b/samples/client/petstore/ruby/lib/petstore/models/enum_arrays.rb
index 1f7c48bf859b..8058a6ac60bb 100644
--- a/samples/client/petstore/ruby/lib/petstore/models/enum_arrays.rb
+++ b/samples/client/petstore/ruby/lib/petstore/models/enum_arrays.rb
@@ -73,6 +73,16 @@ def self.openapi_nullable
       ])
     end
 
+    # Returns attribute type mapping
+    def self.acceptable_openapi_types
+      openapi_types
+    end
+
+    # Returns the nullable attributes
+    def self.acceptable_openapi_nullable
+      openapi_nullable
+    end
+
     # Initializes the object
     # @param [Hash] attributes Model attributes in the form of hash
     def initialize(attributes = {})
@@ -154,18 +164,20 @@ def hash
     def self.build_from_hash(attributes)
       return nil unless attributes.is_a?(Hash)
       attributes = attributes.transform_keys(&:to_sym)
+      # include attributes inherited from allOf parents (the nearest declaration wins)
+      map = acceptable_attribute_map
       transformed_hash = {}
-      openapi_types.each_pair do |key, type|
-        if attributes.key?(attribute_map[key]) && attributes[attribute_map[key]].nil?
+      acceptable_openapi_types.each_pair do |key, type|
+        if attributes.key?(map[key]) && attributes[map[key]].nil?
           transformed_hash["#{key}"] = nil
         elsif type =~ /\AArray<(.*)>/i
           # check to ensure the input is an array given that the attribute
           # is documented as an array but the input is not
-          if attributes[attribute_map[key]].is_a?(Array)
-            transformed_hash["#{key}"] = attributes[attribute_map[key]].map { |v| _deserialize($1, v) }
+          if attributes[map[key]].is_a?(Array)
+            transformed_hash["#{key}"] = attributes[map[key]].map { |v| _deserialize($1, v) }
           end
-        elsif !attributes[attribute_map[key]].nil?
-          transformed_hash["#{key}"] = _deserialize(type, attributes[attribute_map[key]])
+        elsif !attributes[map[key]].nil?
+          transformed_hash["#{key}"] = _deserialize(type, attributes[map[key]])
         end
       end
       new(transformed_hash)
@@ -175,10 +187,11 @@ def self.build_from_hash(attributes)
     # @return [Hash] Returns the object in the form of hash
     def to_hash
       hash = {}
-      self.class.attribute_map.each_pair do |attr, param|
+      # include attributes inherited from allOf parents (the nearest declaration wins)
+      self.class.acceptable_attribute_map.each_pair do |attr, param|
         value = self.send(attr)
         if value.nil?
-          is_nullable = self.class.openapi_nullable.include?(attr)
+          is_nullable = self.class.acceptable_openapi_nullable.include?(attr)
           next if !is_nullable || (is_nullable && !instance_variable_defined?(:"@#{attr}"))
         end
 
diff --git a/samples/client/petstore/ruby/lib/petstore/models/enum_test.rb b/samples/client/petstore/ruby/lib/petstore/models/enum_test.rb
index 5159875cb89b..3b3905c138a3 100644
--- a/samples/client/petstore/ruby/lib/petstore/models/enum_test.rb
+++ b/samples/client/petstore/ruby/lib/petstore/models/enum_test.rb
@@ -98,6 +98,16 @@ def self.openapi_nullable
       ])
     end
 
+    # Returns attribute type mapping
+    def self.acceptable_openapi_types
+      openapi_types
+    end
+
+    # Returns the nullable attributes
+    def self.acceptable_openapi_nullable
+      openapi_nullable
+    end
+
     # Initializes the object
     # @param [Hash] attributes Model attributes in the form of hash
     def initialize(attributes = {})
@@ -254,18 +264,20 @@ def hash
     def self.build_from_hash(attributes)
       return nil unless attributes.is_a?(Hash)
       attributes = attributes.transform_keys(&:to_sym)
+      # include attributes inherited from allOf parents (the nearest declaration wins)
+      map = acceptable_attribute_map
       transformed_hash = {}
-      openapi_types.each_pair do |key, type|
-        if attributes.key?(attribute_map[key]) && attributes[attribute_map[key]].nil?
+      acceptable_openapi_types.each_pair do |key, type|
+        if attributes.key?(map[key]) && attributes[map[key]].nil?
           transformed_hash["#{key}"] = nil
         elsif type =~ /\AArray<(.*)>/i
           # check to ensure the input is an array given that the attribute
           # is documented as an array but the input is not
-          if attributes[attribute_map[key]].is_a?(Array)
-            transformed_hash["#{key}"] = attributes[attribute_map[key]].map { |v| _deserialize($1, v) }
+          if attributes[map[key]].is_a?(Array)
+            transformed_hash["#{key}"] = attributes[map[key]].map { |v| _deserialize($1, v) }
           end
-        elsif !attributes[attribute_map[key]].nil?
-          transformed_hash["#{key}"] = _deserialize(type, attributes[attribute_map[key]])
+        elsif !attributes[map[key]].nil?
+          transformed_hash["#{key}"] = _deserialize(type, attributes[map[key]])
         end
       end
       new(transformed_hash)
@@ -275,10 +287,11 @@ def self.build_from_hash(attributes)
     # @return [Hash] Returns the object in the form of hash
     def to_hash
       hash = {}
-      self.class.attribute_map.each_pair do |attr, param|
+      # include attributes inherited from allOf parents (the nearest declaration wins)
+      self.class.acceptable_attribute_map.each_pair do |attr, param|
         value = self.send(attr)
         if value.nil?
-          is_nullable = self.class.openapi_nullable.include?(attr)
+          is_nullable = self.class.acceptable_openapi_nullable.include?(attr)
           next if !is_nullable || (is_nullable && !instance_variable_defined?(:"@#{attr}"))
         end
 
diff --git a/samples/client/petstore/ruby/lib/petstore/models/fake_big_decimal_map200_response.rb b/samples/client/petstore/ruby/lib/petstore/models/fake_big_decimal_map200_response.rb
index 6d5e47b59656..b7be6af6d90e 100644
--- a/samples/client/petstore/ruby/lib/petstore/models/fake_big_decimal_map200_response.rb
+++ b/samples/client/petstore/ruby/lib/petstore/models/fake_big_decimal_map200_response.rb
@@ -51,6 +51,16 @@ def self.openapi_nullable
       ])
     end
 
+    # Returns attribute type mapping
+    def self.acceptable_openapi_types
+      openapi_types
+    end
+
+    # Returns the nullable attributes
+    def self.acceptable_openapi_nullable
+      openapi_nullable
+    end
+
     # Initializes the object
     # @param [Hash] attributes Model attributes in the form of hash
     def initialize(attributes = {})
@@ -120,18 +130,20 @@ def hash
     def self.build_from_hash(attributes)
       return nil unless attributes.is_a?(Hash)
       attributes = attributes.transform_keys(&:to_sym)
+      # include attributes inherited from allOf parents (the nearest declaration wins)
+      map = acceptable_attribute_map
       transformed_hash = {}
-      openapi_types.each_pair do |key, type|
-        if attributes.key?(attribute_map[key]) && attributes[attribute_map[key]].nil?
+      acceptable_openapi_types.each_pair do |key, type|
+        if attributes.key?(map[key]) && attributes[map[key]].nil?
           transformed_hash["#{key}"] = nil
         elsif type =~ /\AArray<(.*)>/i
           # check to ensure the input is an array given that the attribute
           # is documented as an array but the input is not
-          if attributes[attribute_map[key]].is_a?(Array)
-            transformed_hash["#{key}"] = attributes[attribute_map[key]].map { |v| _deserialize($1, v) }
+          if attributes[map[key]].is_a?(Array)
+            transformed_hash["#{key}"] = attributes[map[key]].map { |v| _deserialize($1, v) }
           end
-        elsif !attributes[attribute_map[key]].nil?
-          transformed_hash["#{key}"] = _deserialize(type, attributes[attribute_map[key]])
+        elsif !attributes[map[key]].nil?
+          transformed_hash["#{key}"] = _deserialize(type, attributes[map[key]])
         end
       end
       new(transformed_hash)
@@ -141,10 +153,11 @@ def self.build_from_hash(attributes)
     # @return [Hash] Returns the object in the form of hash
     def to_hash
       hash = {}
-      self.class.attribute_map.each_pair do |attr, param|
+      # include attributes inherited from allOf parents (the nearest declaration wins)
+      self.class.acceptable_attribute_map.each_pair do |attr, param|
         value = self.send(attr)
         if value.nil?
-          is_nullable = self.class.openapi_nullable.include?(attr)
+          is_nullable = self.class.acceptable_openapi_nullable.include?(attr)
           next if !is_nullable || (is_nullable && !instance_variable_defined?(:"@#{attr}"))
         end
 
diff --git a/samples/client/petstore/ruby/lib/petstore/models/file.rb b/samples/client/petstore/ruby/lib/petstore/models/file.rb
index 219237eb3c07..4fac9978fcaa 100644
--- a/samples/client/petstore/ruby/lib/petstore/models/file.rb
+++ b/samples/client/petstore/ruby/lib/petstore/models/file.rb
@@ -49,6 +49,16 @@ def self.openapi_nullable
       ])
     end
 
+    # Returns attribute type mapping
+    def self.acceptable_openapi_types
+      openapi_types
+    end
+
+    # Returns the nullable attributes
+    def self.acceptable_openapi_nullable
+      openapi_nullable
+    end
+
     # Initializes the object
     # @param [Hash] attributes Model attributes in the form of hash
     def initialize(attributes = {})
@@ -111,18 +121,20 @@ def hash
     def self.build_from_hash(attributes)
       return nil unless attributes.is_a?(Hash)
       attributes = attributes.transform_keys(&:to_sym)
+      # include attributes inherited from allOf parents (the nearest declaration wins)
+      map = acceptable_attribute_map
       transformed_hash = {}
-      openapi_types.each_pair do |key, type|
-        if attributes.key?(attribute_map[key]) && attributes[attribute_map[key]].nil?
+      acceptable_openapi_types.each_pair do |key, type|
+        if attributes.key?(map[key]) && attributes[map[key]].nil?
           transformed_hash["#{key}"] = nil
         elsif type =~ /\AArray<(.*)>/i
           # check to ensure the input is an array given that the attribute
           # is documented as an array but the input is not
-          if attributes[attribute_map[key]].is_a?(Array)
-            transformed_hash["#{key}"] = attributes[attribute_map[key]].map { |v| _deserialize($1, v) }
+          if attributes[map[key]].is_a?(Array)
+            transformed_hash["#{key}"] = attributes[map[key]].map { |v| _deserialize($1, v) }
           end
-        elsif !attributes[attribute_map[key]].nil?
-          transformed_hash["#{key}"] = _deserialize(type, attributes[attribute_map[key]])
+        elsif !attributes[map[key]].nil?
+          transformed_hash["#{key}"] = _deserialize(type, attributes[map[key]])
         end
       end
       new(transformed_hash)
@@ -132,10 +144,11 @@ def self.build_from_hash(attributes)
     # @return [Hash] Returns the object in the form of hash
     def to_hash
       hash = {}
-      self.class.attribute_map.each_pair do |attr, param|
+      # include attributes inherited from allOf parents (the nearest declaration wins)
+      self.class.acceptable_attribute_map.each_pair do |attr, param|
         value = self.send(attr)
         if value.nil?
-          is_nullable = self.class.openapi_nullable.include?(attr)
+          is_nullable = self.class.acceptable_openapi_nullable.include?(attr)
           next if !is_nullable || (is_nullable && !instance_variable_defined?(:"@#{attr}"))
         end
 
diff --git a/samples/client/petstore/ruby/lib/petstore/models/file_schema_test_class.rb b/samples/client/petstore/ruby/lib/petstore/models/file_schema_test_class.rb
index 8fdab5a25e86..074c235ebe17 100644
--- a/samples/client/petstore/ruby/lib/petstore/models/file_schema_test_class.rb
+++ b/samples/client/petstore/ruby/lib/petstore/models/file_schema_test_class.rb
@@ -51,6 +51,16 @@ def self.openapi_nullable
       ])
     end
 
+    # Returns attribute type mapping
+    def self.acceptable_openapi_types
+      openapi_types
+    end
+
+    # Returns the nullable attributes
+    def self.acceptable_openapi_nullable
+      openapi_nullable
+    end
+
     # Initializes the object
     # @param [Hash] attributes Model attributes in the form of hash
     def initialize(attributes = {})
@@ -120,18 +130,20 @@ def hash
     def self.build_from_hash(attributes)
       return nil unless attributes.is_a?(Hash)
       attributes = attributes.transform_keys(&:to_sym)
+      # include attributes inherited from allOf parents (the nearest declaration wins)
+      map = acceptable_attribute_map
       transformed_hash = {}
-      openapi_types.each_pair do |key, type|
-        if attributes.key?(attribute_map[key]) && attributes[attribute_map[key]].nil?
+      acceptable_openapi_types.each_pair do |key, type|
+        if attributes.key?(map[key]) && attributes[map[key]].nil?
           transformed_hash["#{key}"] = nil
         elsif type =~ /\AArray<(.*)>/i
           # check to ensure the input is an array given that the attribute
           # is documented as an array but the input is not
-          if attributes[attribute_map[key]].is_a?(Array)
-            transformed_hash["#{key}"] = attributes[attribute_map[key]].map { |v| _deserialize($1, v) }
+          if attributes[map[key]].is_a?(Array)
+            transformed_hash["#{key}"] = attributes[map[key]].map { |v| _deserialize($1, v) }
           end
-        elsif !attributes[attribute_map[key]].nil?
-          transformed_hash["#{key}"] = _deserialize(type, attributes[attribute_map[key]])
+        elsif !attributes[map[key]].nil?
+          transformed_hash["#{key}"] = _deserialize(type, attributes[map[key]])
         end
       end
       new(transformed_hash)
@@ -141,10 +153,11 @@ def self.build_from_hash(attributes)
     # @return [Hash] Returns the object in the form of hash
     def to_hash
       hash = {}
-      self.class.attribute_map.each_pair do |attr, param|
+      # include attributes inherited from allOf parents (the nearest declaration wins)
+      self.class.acceptable_attribute_map.each_pair do |attr, param|
         value = self.send(attr)
         if value.nil?
-          is_nullable = self.class.openapi_nullable.include?(attr)
+          is_nullable = self.class.acceptable_openapi_nullable.include?(attr)
           next if !is_nullable || (is_nullable && !instance_variable_defined?(:"@#{attr}"))
         end
 
diff --git a/samples/client/petstore/ruby/lib/petstore/models/foo.rb b/samples/client/petstore/ruby/lib/petstore/models/foo.rb
index ceb5b7497955..811726434b54 100644
--- a/samples/client/petstore/ruby/lib/petstore/models/foo.rb
+++ b/samples/client/petstore/ruby/lib/petstore/models/foo.rb
@@ -47,6 +47,16 @@ def self.openapi_nullable
       ])
     end
 
+    # Returns attribute type mapping
+    def self.acceptable_openapi_types
+      openapi_types
+    end
+
+    # Returns the nullable attributes
+    def self.acceptable_openapi_nullable
+      openapi_nullable
+    end
+
     # Initializes the object
     # @param [Hash] attributes Model attributes in the form of hash
     def initialize(attributes = {})
@@ -111,18 +121,20 @@ def hash
     def self.build_from_hash(attributes)
       return nil unless attributes.is_a?(Hash)
       attributes = attributes.transform_keys(&:to_sym)
+      # include attributes inherited from allOf parents (the nearest declaration wins)
+      map = acceptable_attribute_map
       transformed_hash = {}
-      openapi_types.each_pair do |key, type|
-        if attributes.key?(attribute_map[key]) && attributes[attribute_map[key]].nil?
+      acceptable_openapi_types.each_pair do |key, type|
+        if attributes.key?(map[key]) && attributes[map[key]].nil?
           transformed_hash["#{key}"] = nil
         elsif type =~ /\AArray<(.*)>/i
           # check to ensure the input is an array given that the attribute
           # is documented as an array but the input is not
-          if attributes[attribute_map[key]].is_a?(Array)
-            transformed_hash["#{key}"] = attributes[attribute_map[key]].map { |v| _deserialize($1, v) }
+          if attributes[map[key]].is_a?(Array)
+            transformed_hash["#{key}"] = attributes[map[key]].map { |v| _deserialize($1, v) }
           end
-        elsif !attributes[attribute_map[key]].nil?
-          transformed_hash["#{key}"] = _deserialize(type, attributes[attribute_map[key]])
+        elsif !attributes[map[key]].nil?
+          transformed_hash["#{key}"] = _deserialize(type, attributes[map[key]])
         end
       end
       new(transformed_hash)
@@ -132,10 +144,11 @@ def self.build_from_hash(attributes)
     # @return [Hash] Returns the object in the form of hash
     def to_hash
       hash = {}
-      self.class.attribute_map.each_pair do |attr, param|
+      # include attributes inherited from allOf parents (the nearest declaration wins)
+      self.class.acceptable_attribute_map.each_pair do |attr, param|
         value = self.send(attr)
         if value.nil?
-          is_nullable = self.class.openapi_nullable.include?(attr)
+          is_nullable = self.class.acceptable_openapi_nullable.include?(attr)
           next if !is_nullable || (is_nullable && !instance_variable_defined?(:"@#{attr}"))
         end
 
diff --git a/samples/client/petstore/ruby/lib/petstore/models/foo_get_default_response.rb b/samples/client/petstore/ruby/lib/petstore/models/foo_get_default_response.rb
index 42538a14e2cb..61d044ad8f26 100644
--- a/samples/client/petstore/ruby/lib/petstore/models/foo_get_default_response.rb
+++ b/samples/client/petstore/ruby/lib/petstore/models/foo_get_default_response.rb
@@ -47,6 +47,16 @@ def self.openapi_nullable
       ])
     end
 
+    # Returns attribute type mapping
+    def self.acceptable_openapi_types
+      openapi_types
+    end
+
+    # Returns the nullable attributes
+    def self.acceptable_openapi_nullable
+      openapi_nullable
+    end
+
     # Initializes the object
     # @param [Hash] attributes Model attributes in the form of hash
     def initialize(attributes = {})
@@ -109,18 +119,20 @@ def hash
     def self.build_from_hash(attributes)
       return nil unless attributes.is_a?(Hash)
       attributes = attributes.transform_keys(&:to_sym)
+      # include attributes inherited from allOf parents (the nearest declaration wins)
+      map = acceptable_attribute_map
       transformed_hash = {}
-      openapi_types.each_pair do |key, type|
-        if attributes.key?(attribute_map[key]) && attributes[attribute_map[key]].nil?
+      acceptable_openapi_types.each_pair do |key, type|
+        if attributes.key?(map[key]) && attributes[map[key]].nil?
           transformed_hash["#{key}"] = nil
         elsif type =~ /\AArray<(.*)>/i
           # check to ensure the input is an array given that the attribute
           # is documented as an array but the input is not
-          if attributes[attribute_map[key]].is_a?(Array)
-            transformed_hash["#{key}"] = attributes[attribute_map[key]].map { |v| _deserialize($1, v) }
+          if attributes[map[key]].is_a?(Array)
+            transformed_hash["#{key}"] = attributes[map[key]].map { |v| _deserialize($1, v) }
           end
-        elsif !attributes[attribute_map[key]].nil?
-          transformed_hash["#{key}"] = _deserialize(type, attributes[attribute_map[key]])
+        elsif !attributes[map[key]].nil?
+          transformed_hash["#{key}"] = _deserialize(type, attributes[map[key]])
         end
       end
       new(transformed_hash)
@@ -130,10 +142,11 @@ def self.build_from_hash(attributes)
     # @return [Hash] Returns the object in the form of hash
     def to_hash
       hash = {}
-      self.class.attribute_map.each_pair do |attr, param|
+      # include attributes inherited from allOf parents (the nearest declaration wins)
+      self.class.acceptable_attribute_map.each_pair do |attr, param|
         value = self.send(attr)
         if value.nil?
-          is_nullable = self.class.openapi_nullable.include?(attr)
+          is_nullable = self.class.acceptable_openapi_nullable.include?(attr)
           next if !is_nullable || (is_nullable && !instance_variable_defined?(:"@#{attr}"))
         end
 
diff --git a/samples/client/petstore/ruby/lib/petstore/models/format_test.rb b/samples/client/petstore/ruby/lib/petstore/models/format_test.rb
index 03a4e130a8f9..6760f6807c59 100644
--- a/samples/client/petstore/ruby/lib/petstore/models/format_test.rb
+++ b/samples/client/petstore/ruby/lib/petstore/models/format_test.rb
@@ -109,6 +109,16 @@ def self.openapi_nullable
       ])
     end
 
+    # Returns attribute type mapping
+    def self.acceptable_openapi_types
+      openapi_types
+    end
+
+    # Returns the nullable attributes
+    def self.acceptable_openapi_nullable
+      openapi_nullable
+    end
+
     # Initializes the object
     # @param [Hash] attributes Model attributes in the form of hash
     def initialize(attributes = {})
@@ -525,18 +535,20 @@ def hash
     def self.build_from_hash(attributes)
       return nil unless attributes.is_a?(Hash)
       attributes = attributes.transform_keys(&:to_sym)
+      # include attributes inherited from allOf parents (the nearest declaration wins)
+      map = acceptable_attribute_map
       transformed_hash = {}
-      openapi_types.each_pair do |key, type|
-        if attributes.key?(attribute_map[key]) && attributes[attribute_map[key]].nil?
+      acceptable_openapi_types.each_pair do |key, type|
+        if attributes.key?(map[key]) && attributes[map[key]].nil?
           transformed_hash["#{key}"] = nil
         elsif type =~ /\AArray<(.*)>/i
           # check to ensure the input is an array given that the attribute
           # is documented as an array but the input is not
-          if attributes[attribute_map[key]].is_a?(Array)
-            transformed_hash["#{key}"] = attributes[attribute_map[key]].map { |v| _deserialize($1, v) }
+          if attributes[map[key]].is_a?(Array)
+            transformed_hash["#{key}"] = attributes[map[key]].map { |v| _deserialize($1, v) }
           end
-        elsif !attributes[attribute_map[key]].nil?
-          transformed_hash["#{key}"] = _deserialize(type, attributes[attribute_map[key]])
+        elsif !attributes[map[key]].nil?
+          transformed_hash["#{key}"] = _deserialize(type, attributes[map[key]])
         end
       end
       new(transformed_hash)
@@ -546,10 +558,11 @@ def self.build_from_hash(attributes)
     # @return [Hash] Returns the object in the form of hash
     def to_hash
       hash = {}
-      self.class.attribute_map.each_pair do |attr, param|
+      # include attributes inherited from allOf parents (the nearest declaration wins)
+      self.class.acceptable_attribute_map.each_pair do |attr, param|
         value = self.send(attr)
         if value.nil?
-          is_nullable = self.class.openapi_nullable.include?(attr)
+          is_nullable = self.class.acceptable_openapi_nullable.include?(attr)
           next if !is_nullable || (is_nullable && !instance_variable_defined?(:"@#{attr}"))
         end
 
diff --git a/samples/client/petstore/ruby/lib/petstore/models/has_only_read_only.rb b/samples/client/petstore/ruby/lib/petstore/models/has_only_read_only.rb
index cc584c09e54f..604a3da147bd 100644
--- a/samples/client/petstore/ruby/lib/petstore/models/has_only_read_only.rb
+++ b/samples/client/petstore/ruby/lib/petstore/models/has_only_read_only.rb
@@ -51,6 +51,16 @@ def self.openapi_nullable
       ])
     end
 
+    # Returns attribute type mapping
+    def self.acceptable_openapi_types
+      openapi_types
+    end
+
+    # Returns the nullable attributes
+    def self.acceptable_openapi_nullable
+      openapi_nullable
+    end
+
     # Initializes the object
     # @param [Hash] attributes Model attributes in the form of hash
     def initialize(attributes = {})
@@ -118,18 +128,20 @@ def hash
     def self.build_from_hash(attributes)
       return nil unless attributes.is_a?(Hash)
       attributes = attributes.transform_keys(&:to_sym)
+      # include attributes inherited from allOf parents (the nearest declaration wins)
+      map = acceptable_attribute_map
       transformed_hash = {}
-      openapi_types.each_pair do |key, type|
-        if attributes.key?(attribute_map[key]) && attributes[attribute_map[key]].nil?
+      acceptable_openapi_types.each_pair do |key, type|
+        if attributes.key?(map[key]) && attributes[map[key]].nil?
           transformed_hash["#{key}"] = nil
         elsif type =~ /\AArray<(.*)>/i
           # check to ensure the input is an array given that the attribute
           # is documented as an array but the input is not
-          if attributes[attribute_map[key]].is_a?(Array)
-            transformed_hash["#{key}"] = attributes[attribute_map[key]].map { |v| _deserialize($1, v) }
+          if attributes[map[key]].is_a?(Array)
+            transformed_hash["#{key}"] = attributes[map[key]].map { |v| _deserialize($1, v) }
           end
-        elsif !attributes[attribute_map[key]].nil?
-          transformed_hash["#{key}"] = _deserialize(type, attributes[attribute_map[key]])
+        elsif !attributes[map[key]].nil?
+          transformed_hash["#{key}"] = _deserialize(type, attributes[map[key]])
         end
       end
       new(transformed_hash)
@@ -139,10 +151,11 @@ def self.build_from_hash(attributes)
     # @return [Hash] Returns the object in the form of hash
     def to_hash
       hash = {}
-      self.class.attribute_map.each_pair do |attr, param|
+      # include attributes inherited from allOf parents (the nearest declaration wins)
+      self.class.acceptable_attribute_map.each_pair do |attr, param|
         value = self.send(attr)
         if value.nil?
-          is_nullable = self.class.openapi_nullable.include?(attr)
+          is_nullable = self.class.acceptable_openapi_nullable.include?(attr)
           next if !is_nullable || (is_nullable && !instance_variable_defined?(:"@#{attr}"))
         end
 
diff --git a/samples/client/petstore/ruby/lib/petstore/models/health_check_result.rb b/samples/client/petstore/ruby/lib/petstore/models/health_check_result.rb
index a66e1b71331d..0792044db072 100644
--- a/samples/client/petstore/ruby/lib/petstore/models/health_check_result.rb
+++ b/samples/client/petstore/ruby/lib/petstore/models/health_check_result.rb
@@ -49,6 +49,16 @@ def self.openapi_nullable
       ])
     end
 
+    # Returns attribute type mapping
+    def self.acceptable_openapi_types
+      openapi_types
+    end
+
+    # Returns the nullable attributes
+    def self.acceptable_openapi_nullable
+      openapi_nullable
+    end
+
     # Initializes the object
     # @param [Hash] attributes Model attributes in the form of hash
     def initialize(attributes = {})
@@ -111,18 +121,20 @@ def hash
     def self.build_from_hash(attributes)
       return nil unless attributes.is_a?(Hash)
       attributes = attributes.transform_keys(&:to_sym)
+      # include attributes inherited from allOf parents (the nearest declaration wins)
+      map = acceptable_attribute_map
       transformed_hash = {}
-      openapi_types.each_pair do |key, type|
-        if attributes.key?(attribute_map[key]) && attributes[attribute_map[key]].nil?
+      acceptable_openapi_types.each_pair do |key, type|
+        if attributes.key?(map[key]) && attributes[map[key]].nil?
           transformed_hash["#{key}"] = nil
         elsif type =~ /\AArray<(.*)>/i
           # check to ensure the input is an array given that the attribute
           # is documented as an array but the input is not
-          if attributes[attribute_map[key]].is_a?(Array)
-            transformed_hash["#{key}"] = attributes[attribute_map[key]].map { |v| _deserialize($1, v) }
+          if attributes[map[key]].is_a?(Array)
+            transformed_hash["#{key}"] = attributes[map[key]].map { |v| _deserialize($1, v) }
           end
-        elsif !attributes[attribute_map[key]].nil?
-          transformed_hash["#{key}"] = _deserialize(type, attributes[attribute_map[key]])
+        elsif !attributes[map[key]].nil?
+          transformed_hash["#{key}"] = _deserialize(type, attributes[map[key]])
         end
       end
       new(transformed_hash)
@@ -132,10 +144,11 @@ def self.build_from_hash(attributes)
     # @return [Hash] Returns the object in the form of hash
     def to_hash
       hash = {}
-      self.class.attribute_map.each_pair do |attr, param|
+      # include attributes inherited from allOf parents (the nearest declaration wins)
+      self.class.acceptable_attribute_map.each_pair do |attr, param|
         value = self.send(attr)
         if value.nil?
-          is_nullable = self.class.openapi_nullable.include?(attr)
+          is_nullable = self.class.acceptable_openapi_nullable.include?(attr)
           next if !is_nullable || (is_nullable && !instance_variable_defined?(:"@#{attr}"))
         end
 
diff --git a/samples/client/petstore/ruby/lib/petstore/models/list.rb b/samples/client/petstore/ruby/lib/petstore/models/list.rb
index 2dc658065278..ecc8eb8aafc5 100644
--- a/samples/client/petstore/ruby/lib/petstore/models/list.rb
+++ b/samples/client/petstore/ruby/lib/petstore/models/list.rb
@@ -47,6 +47,16 @@ def self.openapi_nullable
       ])
     end
 
+    # Returns attribute type mapping
+    def self.acceptable_openapi_types
+      openapi_types
+    end
+
+    # Returns the nullable attributes
+    def self.acceptable_openapi_nullable
+      openapi_nullable
+    end
+
     # Initializes the object
     # @param [Hash] attributes Model attributes in the form of hash
     def initialize(attributes = {})
@@ -109,18 +119,20 @@ def hash
     def self.build_from_hash(attributes)
       return nil unless attributes.is_a?(Hash)
       attributes = attributes.transform_keys(&:to_sym)
+      # include attributes inherited from allOf parents (the nearest declaration wins)
+      map = acceptable_attribute_map
       transformed_hash = {}
-      openapi_types.each_pair do |key, type|
-        if attributes.key?(attribute_map[key]) && attributes[attribute_map[key]].nil?
+      acceptable_openapi_types.each_pair do |key, type|
+        if attributes.key?(map[key]) && attributes[map[key]].nil?
           transformed_hash["#{key}"] = nil
         elsif type =~ /\AArray<(.*)>/i
           # check to ensure the input is an array given that the attribute
           # is documented as an array but the input is not
-          if attributes[attribute_map[key]].is_a?(Array)
-            transformed_hash["#{key}"] = attributes[attribute_map[key]].map { |v| _deserialize($1, v) }
+          if attributes[map[key]].is_a?(Array)
+            transformed_hash["#{key}"] = attributes[map[key]].map { |v| _deserialize($1, v) }
           end
-        elsif !attributes[attribute_map[key]].nil?
-          transformed_hash["#{key}"] = _deserialize(type, attributes[attribute_map[key]])
+        elsif !attributes[map[key]].nil?
+          transformed_hash["#{key}"] = _deserialize(type, attributes[map[key]])
         end
       end
       new(transformed_hash)
@@ -130,10 +142,11 @@ def self.build_from_hash(attributes)
     # @return [Hash] Returns the object in the form of hash
     def to_hash
       hash = {}
-      self.class.attribute_map.each_pair do |attr, param|
+      # include attributes inherited from allOf parents (the nearest declaration wins)
+      self.class.acceptable_attribute_map.each_pair do |attr, param|
         value = self.send(attr)
         if value.nil?
-          is_nullable = self.class.openapi_nullable.include?(attr)
+          is_nullable = self.class.acceptable_openapi_nullable.include?(attr)
           next if !is_nullable || (is_nullable && !instance_variable_defined?(:"@#{attr}"))
         end
 
diff --git a/samples/client/petstore/ruby/lib/petstore/models/map_test.rb b/samples/client/petstore/ruby/lib/petstore/models/map_test.rb
index 78c5472f24ae..eca01649a52a 100644
--- a/samples/client/petstore/ruby/lib/petstore/models/map_test.rb
+++ b/samples/client/petstore/ruby/lib/petstore/models/map_test.rb
@@ -81,6 +81,16 @@ def self.openapi_nullable
       ])
     end
 
+    # Returns attribute type mapping
+    def self.acceptable_openapi_types
+      openapi_types
+    end
+
+    # Returns the nullable attributes
+    def self.acceptable_openapi_nullable
+      openapi_nullable
+    end
+
     # Initializes the object
     # @param [Hash] attributes Model attributes in the form of hash
     def initialize(attributes = {})
@@ -166,18 +176,20 @@ def hash
     def self.build_from_hash(attributes)
       return nil unless attributes.is_a?(Hash)
       attributes = attributes.transform_keys(&:to_sym)
+      # include attributes inherited from allOf parents (the nearest declaration wins)
+      map = acceptable_attribute_map
       transformed_hash = {}
-      openapi_types.each_pair do |key, type|
-        if attributes.key?(attribute_map[key]) && attributes[attribute_map[key]].nil?
+      acceptable_openapi_types.each_pair do |key, type|
+        if attributes.key?(map[key]) && attributes[map[key]].nil?
           transformed_hash["#{key}"] = nil
         elsif type =~ /\AArray<(.*)>/i
           # check to ensure the input is an array given that the attribute
           # is documented as an array but the input is not
-          if attributes[attribute_map[key]].is_a?(Array)
-            transformed_hash["#{key}"] = attributes[attribute_map[key]].map { |v| _deserialize($1, v) }
+          if attributes[map[key]].is_a?(Array)
+            transformed_hash["#{key}"] = attributes[map[key]].map { |v| _deserialize($1, v) }
           end
-        elsif !attributes[attribute_map[key]].nil?
-          transformed_hash["#{key}"] = _deserialize(type, attributes[attribute_map[key]])
+        elsif !attributes[map[key]].nil?
+          transformed_hash["#{key}"] = _deserialize(type, attributes[map[key]])
         end
       end
       new(transformed_hash)
@@ -187,10 +199,11 @@ def self.build_from_hash(attributes)
     # @return [Hash] Returns the object in the form of hash
     def to_hash
       hash = {}
-      self.class.attribute_map.each_pair do |attr, param|
+      # include attributes inherited from allOf parents (the nearest declaration wins)
+      self.class.acceptable_attribute_map.each_pair do |attr, param|
         value = self.send(attr)
         if value.nil?
-          is_nullable = self.class.openapi_nullable.include?(attr)
+          is_nullable = self.class.acceptable_openapi_nullable.include?(attr)
           next if !is_nullable || (is_nullable && !instance_variable_defined?(:"@#{attr}"))
         end
 
diff --git a/samples/client/petstore/ruby/lib/petstore/models/mixed_properties_and_additional_properties_class.rb b/samples/client/petstore/ruby/lib/petstore/models/mixed_properties_and_additional_properties_class.rb
index bf1d3768951b..060c8488652f 100644
--- a/samples/client/petstore/ruby/lib/petstore/models/mixed_properties_and_additional_properties_class.rb
+++ b/samples/client/petstore/ruby/lib/petstore/models/mixed_properties_and_additional_properties_class.rb
@@ -55,6 +55,16 @@ def self.openapi_nullable
       ])
     end
 
+    # Returns attribute type mapping
+    def self.acceptable_openapi_types
+      openapi_types
+    end
+
+    # Returns the nullable attributes
+    def self.acceptable_openapi_nullable
+      openapi_nullable
+    end
+
     # Initializes the object
     # @param [Hash] attributes Model attributes in the form of hash
     def initialize(attributes = {})
@@ -129,18 +139,20 @@ def hash
     def self.build_from_hash(attributes)
       return nil unless attributes.is_a?(Hash)
       attributes = attributes.transform_keys(&:to_sym)
+      # include attributes inherited from allOf parents (the nearest declaration wins)
+      map = acceptable_attribute_map
       transformed_hash = {}
-      openapi_types.each_pair do |key, type|
-        if attributes.key?(attribute_map[key]) && attributes[attribute_map[key]].nil?
+      acceptable_openapi_types.each_pair do |key, type|
+        if attributes.key?(map[key]) && attributes[map[key]].nil?
           transformed_hash["#{key}"] = nil
         elsif type =~ /\AArray<(.*)>/i
           # check to ensure the input is an array given that the attribute
           # is documented as an array but the input is not
-          if attributes[attribute_map[key]].is_a?(Array)
-            transformed_hash["#{key}"] = attributes[attribute_map[key]].map { |v| _deserialize($1, v) }
+          if attributes[map[key]].is_a?(Array)
+            transformed_hash["#{key}"] = attributes[map[key]].map { |v| _deserialize($1, v) }
           end
-        elsif !attributes[attribute_map[key]].nil?
-          transformed_hash["#{key}"] = _deserialize(type, attributes[attribute_map[key]])
+        elsif !attributes[map[key]].nil?
+          transformed_hash["#{key}"] = _deserialize(type, attributes[map[key]])
         end
       end
       new(transformed_hash)
@@ -150,10 +162,11 @@ def self.build_from_hash(attributes)
     # @return [Hash] Returns the object in the form of hash
     def to_hash
       hash = {}
-      self.class.attribute_map.each_pair do |attr, param|
+      # include attributes inherited from allOf parents (the nearest declaration wins)
+      self.class.acceptable_attribute_map.each_pair do |attr, param|
         value = self.send(attr)
         if value.nil?
-          is_nullable = self.class.openapi_nullable.include?(attr)
+          is_nullable = self.class.acceptable_openapi_nullable.include?(attr)
           next if !is_nullable || (is_nullable && !instance_variable_defined?(:"@#{attr}"))
         end
 
diff --git a/samples/client/petstore/ruby/lib/petstore/models/model200_response.rb b/samples/client/petstore/ruby/lib/petstore/models/model200_response.rb
index 9cff83ced2c9..2ea5253eb3d4 100644
--- a/samples/client/petstore/ruby/lib/petstore/models/model200_response.rb
+++ b/samples/client/petstore/ruby/lib/petstore/models/model200_response.rb
@@ -52,6 +52,16 @@ def self.openapi_nullable
       ])
     end
 
+    # Returns attribute type mapping
+    def self.acceptable_openapi_types
+      openapi_types
+    end
+
+    # Returns the nullable attributes
+    def self.acceptable_openapi_nullable
+      openapi_nullable
+    end
+
     # Initializes the object
     # @param [Hash] attributes Model attributes in the form of hash
     def initialize(attributes = {})
@@ -119,18 +129,20 @@ def hash
     def self.build_from_hash(attributes)
       return nil unless attributes.is_a?(Hash)
       attributes = attributes.transform_keys(&:to_sym)
+      # include attributes inherited from allOf parents (the nearest declaration wins)
+      map = acceptable_attribute_map
       transformed_hash = {}
-      openapi_types.each_pair do |key, type|
-        if attributes.key?(attribute_map[key]) && attributes[attribute_map[key]].nil?
+      acceptable_openapi_types.each_pair do |key, type|
+        if attributes.key?(map[key]) && attributes[map[key]].nil?
           transformed_hash["#{key}"] = nil
         elsif type =~ /\AArray<(.*)>/i
           # check to ensure the input is an array given that the attribute
           # is documented as an array but the input is not
-          if attributes[attribute_map[key]].is_a?(Array)
-            transformed_hash["#{key}"] = attributes[attribute_map[key]].map { |v| _deserialize($1, v) }
+          if attributes[map[key]].is_a?(Array)
+            transformed_hash["#{key}"] = attributes[map[key]].map { |v| _deserialize($1, v) }
           end
-        elsif !attributes[attribute_map[key]].nil?
-          transformed_hash["#{key}"] = _deserialize(type, attributes[attribute_map[key]])
+        elsif !attributes[map[key]].nil?
+          transformed_hash["#{key}"] = _deserialize(type, attributes[map[key]])
         end
       end
       new(transformed_hash)
@@ -140,10 +152,11 @@ def self.build_from_hash(attributes)
     # @return [Hash] Returns the object in the form of hash
     def to_hash
       hash = {}
-      self.class.attribute_map.each_pair do |attr, param|
+      # include attributes inherited from allOf parents (the nearest declaration wins)
+      self.class.acceptable_attribute_map.each_pair do |attr, param|
         value = self.send(attr)
         if value.nil?
-          is_nullable = self.class.openapi_nullable.include?(attr)
+          is_nullable = self.class.acceptable_openapi_nullable.include?(attr)
           next if !is_nullable || (is_nullable && !instance_variable_defined?(:"@#{attr}"))
         end
 
diff --git a/samples/client/petstore/ruby/lib/petstore/models/model_return.rb b/samples/client/petstore/ruby/lib/petstore/models/model_return.rb
index d520a45c2040..c2b6ac11c2e9 100644
--- a/samples/client/petstore/ruby/lib/petstore/models/model_return.rb
+++ b/samples/client/petstore/ruby/lib/petstore/models/model_return.rb
@@ -48,6 +48,16 @@ def self.openapi_nullable
       ])
     end
 
+    # Returns attribute type mapping
+    def self.acceptable_openapi_types
+      openapi_types
+    end
+
+    # Returns the nullable attributes
+    def self.acceptable_openapi_nullable
+      openapi_nullable
+    end
+
     # Initializes the object
     # @param [Hash] attributes Model attributes in the form of hash
     def initialize(attributes = {})
@@ -110,18 +120,20 @@ def hash
     def self.build_from_hash(attributes)
       return nil unless attributes.is_a?(Hash)
       attributes = attributes.transform_keys(&:to_sym)
+      # include attributes inherited from allOf parents (the nearest declaration wins)
+      map = acceptable_attribute_map
       transformed_hash = {}
-      openapi_types.each_pair do |key, type|
-        if attributes.key?(attribute_map[key]) && attributes[attribute_map[key]].nil?
+      acceptable_openapi_types.each_pair do |key, type|
+        if attributes.key?(map[key]) && attributes[map[key]].nil?
           transformed_hash["#{key}"] = nil
         elsif type =~ /\AArray<(.*)>/i
           # check to ensure the input is an array given that the attribute
           # is documented as an array but the input is not
-          if attributes[attribute_map[key]].is_a?(Array)
-            transformed_hash["#{key}"] = attributes[attribute_map[key]].map { |v| _deserialize($1, v) }
+          if attributes[map[key]].is_a?(Array)
+            transformed_hash["#{key}"] = attributes[map[key]].map { |v| _deserialize($1, v) }
           end
-        elsif !attributes[attribute_map[key]].nil?
-          transformed_hash["#{key}"] = _deserialize(type, attributes[attribute_map[key]])
+        elsif !attributes[map[key]].nil?
+          transformed_hash["#{key}"] = _deserialize(type, attributes[map[key]])
         end
       end
       new(transformed_hash)
@@ -131,10 +143,11 @@ def self.build_from_hash(attributes)
     # @return [Hash] Returns the object in the form of hash
     def to_hash
       hash = {}
-      self.class.attribute_map.each_pair do |attr, param|
+      # include attributes inherited from allOf parents (the nearest declaration wins)
+      self.class.acceptable_attribute_map.each_pair do |attr, param|
         value = self.send(attr)
         if value.nil?
-          is_nullable = self.class.openapi_nullable.include?(attr)
+          is_nullable = self.class.acceptable_openapi_nullable.include?(attr)
           next if !is_nullable || (is_nullable && !instance_variable_defined?(:"@#{attr}"))
         end
 
diff --git a/samples/client/petstore/ruby/lib/petstore/models/name.rb b/samples/client/petstore/ruby/lib/petstore/models/name.rb
index 45b01b5746d3..c989368e6597 100644
--- a/samples/client/petstore/ruby/lib/petstore/models/name.rb
+++ b/samples/client/petstore/ruby/lib/petstore/models/name.rb
@@ -60,6 +60,16 @@ def self.openapi_nullable
       ])
     end
 
+    # Returns attribute type mapping
+    def self.acceptable_openapi_types
+      openapi_types
+    end
+
+    # Returns the nullable attributes
+    def self.acceptable_openapi_nullable
+      openapi_nullable
+    end
+
     # Initializes the object
     # @param [Hash] attributes Model attributes in the form of hash
     def initialize(attributes = {})
@@ -154,18 +164,20 @@ def hash
     def self.build_from_hash(attributes)
       return nil unless attributes.is_a?(Hash)
       attributes = attributes.transform_keys(&:to_sym)
+      # include attributes inherited from allOf parents (the nearest declaration wins)
+      map = acceptable_attribute_map
       transformed_hash = {}
-      openapi_types.each_pair do |key, type|
-        if attributes.key?(attribute_map[key]) && attributes[attribute_map[key]].nil?
+      acceptable_openapi_types.each_pair do |key, type|
+        if attributes.key?(map[key]) && attributes[map[key]].nil?
           transformed_hash["#{key}"] = nil
         elsif type =~ /\AArray<(.*)>/i
           # check to ensure the input is an array given that the attribute
           # is documented as an array but the input is not
-          if attributes[attribute_map[key]].is_a?(Array)
-            transformed_hash["#{key}"] = attributes[attribute_map[key]].map { |v| _deserialize($1, v) }
+          if attributes[map[key]].is_a?(Array)
+            transformed_hash["#{key}"] = attributes[map[key]].map { |v| _deserialize($1, v) }
           end
-        elsif !attributes[attribute_map[key]].nil?
-          transformed_hash["#{key}"] = _deserialize(type, attributes[attribute_map[key]])
+        elsif !attributes[map[key]].nil?
+          transformed_hash["#{key}"] = _deserialize(type, attributes[map[key]])
         end
       end
       new(transformed_hash)
@@ -175,10 +187,11 @@ def self.build_from_hash(attributes)
     # @return [Hash] Returns the object in the form of hash
     def to_hash
       hash = {}
-      self.class.attribute_map.each_pair do |attr, param|
+      # include attributes inherited from allOf parents (the nearest declaration wins)
+      self.class.acceptable_attribute_map.each_pair do |attr, param|
         value = self.send(attr)
         if value.nil?
-          is_nullable = self.class.openapi_nullable.include?(attr)
+          is_nullable = self.class.acceptable_openapi_nullable.include?(attr)
           next if !is_nullable || (is_nullable && !instance_variable_defined?(:"@#{attr}"))
         end
 
diff --git a/samples/client/petstore/ruby/lib/petstore/models/nullable_class.rb b/samples/client/petstore/ruby/lib/petstore/models/nullable_class.rb
index f81fb17f118a..de5510060a65 100644
--- a/samples/client/petstore/ruby/lib/petstore/models/nullable_class.rb
+++ b/samples/client/petstore/ruby/lib/petstore/models/nullable_class.rb
@@ -101,6 +101,16 @@ def self.openapi_nullable
       ])
     end
 
+    # Returns attribute type mapping
+    def self.acceptable_openapi_types
+      openapi_types
+    end
+
+    # Returns the nullable attributes
+    def self.acceptable_openapi_nullable
+      openapi_nullable
+    end
+
     # Initializes the object
     # @param [Hash] attributes Model attributes in the form of hash
     def initialize(attributes = {})
@@ -230,18 +240,20 @@ def hash
     def self.build_from_hash(attributes)
       return nil unless attributes.is_a?(Hash)
       attributes = attributes.transform_keys(&:to_sym)
+      # include attributes inherited from allOf parents (the nearest declaration wins)
+      map = acceptable_attribute_map
       transformed_hash = {}
-      openapi_types.each_pair do |key, type|
-        if attributes.key?(attribute_map[key]) && attributes[attribute_map[key]].nil?
+      acceptable_openapi_types.each_pair do |key, type|
+        if attributes.key?(map[key]) && attributes[map[key]].nil?
           transformed_hash["#{key}"] = nil
         elsif type =~ /\AArray<(.*)>/i
           # check to ensure the input is an array given that the attribute
           # is documented as an array but the input is not
-          if attributes[attribute_map[key]].is_a?(Array)
-            transformed_hash["#{key}"] = attributes[attribute_map[key]].map { |v| _deserialize($1, v) }
+          if attributes[map[key]].is_a?(Array)
+            transformed_hash["#{key}"] = attributes[map[key]].map { |v| _deserialize($1, v) }
           end
-        elsif !attributes[attribute_map[key]].nil?
-          transformed_hash["#{key}"] = _deserialize(type, attributes[attribute_map[key]])
+        elsif !attributes[map[key]].nil?
+          transformed_hash["#{key}"] = _deserialize(type, attributes[map[key]])
         end
       end
       new(transformed_hash)
@@ -251,10 +263,11 @@ def self.build_from_hash(attributes)
     # @return [Hash] Returns the object in the form of hash
     def to_hash
       hash = {}
-      self.class.attribute_map.each_pair do |attr, param|
+      # include attributes inherited from allOf parents (the nearest declaration wins)
+      self.class.acceptable_attribute_map.each_pair do |attr, param|
         value = self.send(attr)
         if value.nil?
-          is_nullable = self.class.openapi_nullable.include?(attr)
+          is_nullable = self.class.acceptable_openapi_nullable.include?(attr)
           next if !is_nullable || (is_nullable && !instance_variable_defined?(:"@#{attr}"))
         end
 
diff --git a/samples/client/petstore/ruby/lib/petstore/models/number_only.rb b/samples/client/petstore/ruby/lib/petstore/models/number_only.rb
index 9bf457dfd188..b4fb53e2c3d3 100644
--- a/samples/client/petstore/ruby/lib/petstore/models/number_only.rb
+++ b/samples/client/petstore/ruby/lib/petstore/models/number_only.rb
@@ -47,6 +47,16 @@ def self.openapi_nullable
       ])
     end
 
+    # Returns attribute type mapping
+    def self.acceptable_openapi_types
+      openapi_types
+    end
+
+    # Returns the nullable attributes
+    def self.acceptable_openapi_nullable
+      openapi_nullable
+    end
+
     # Initializes the object
     # @param [Hash] attributes Model attributes in the form of hash
     def initialize(attributes = {})
@@ -109,18 +119,20 @@ def hash
     def self.build_from_hash(attributes)
       return nil unless attributes.is_a?(Hash)
       attributes = attributes.transform_keys(&:to_sym)
+      # include attributes inherited from allOf parents (the nearest declaration wins)
+      map = acceptable_attribute_map
       transformed_hash = {}
-      openapi_types.each_pair do |key, type|
-        if attributes.key?(attribute_map[key]) && attributes[attribute_map[key]].nil?
+      acceptable_openapi_types.each_pair do |key, type|
+        if attributes.key?(map[key]) && attributes[map[key]].nil?
           transformed_hash["#{key}"] = nil
         elsif type =~ /\AArray<(.*)>/i
           # check to ensure the input is an array given that the attribute
           # is documented as an array but the input is not
-          if attributes[attribute_map[key]].is_a?(Array)
-            transformed_hash["#{key}"] = attributes[attribute_map[key]].map { |v| _deserialize($1, v) }
+          if attributes[map[key]].is_a?(Array)
+            transformed_hash["#{key}"] = attributes[map[key]].map { |v| _deserialize($1, v) }
           end
-        elsif !attributes[attribute_map[key]].nil?
-          transformed_hash["#{key}"] = _deserialize(type, attributes[attribute_map[key]])
+        elsif !attributes[map[key]].nil?
+          transformed_hash["#{key}"] = _deserialize(type, attributes[map[key]])
         end
       end
       new(transformed_hash)
@@ -130,10 +142,11 @@ def self.build_from_hash(attributes)
     # @return [Hash] Returns the object in the form of hash
     def to_hash
       hash = {}
-      self.class.attribute_map.each_pair do |attr, param|
+      # include attributes inherited from allOf parents (the nearest declaration wins)
+      self.class.acceptable_attribute_map.each_pair do |attr, param|
         value = self.send(attr)
         if value.nil?
-          is_nullable = self.class.openapi_nullable.include?(attr)
+          is_nullable = self.class.acceptable_openapi_nullable.include?(attr)
           next if !is_nullable || (is_nullable && !instance_variable_defined?(:"@#{attr}"))
         end
 
diff --git a/samples/client/petstore/ruby/lib/petstore/models/object_with_deprecated_fields.rb b/samples/client/petstore/ruby/lib/petstore/models/object_with_deprecated_fields.rb
index dceda346bd70..3819fef7a58b 100644
--- a/samples/client/petstore/ruby/lib/petstore/models/object_with_deprecated_fields.rb
+++ b/samples/client/petstore/ruby/lib/petstore/models/object_with_deprecated_fields.rb
@@ -59,6 +59,16 @@ def self.openapi_nullable
       ])
     end
 
+    # Returns attribute type mapping
+    def self.acceptable_openapi_types
+      openapi_types
+    end
+
+    # Returns the nullable attributes
+    def self.acceptable_openapi_nullable
+      openapi_nullable
+    end
+
     # Initializes the object
     # @param [Hash] attributes Model attributes in the form of hash
     def initialize(attributes = {})
@@ -138,18 +148,20 @@ def hash
     def self.build_from_hash(attributes)
       return nil unless attributes.is_a?(Hash)
       attributes = attributes.transform_keys(&:to_sym)
+      # include attributes inherited from allOf parents (the nearest declaration wins)
+      map = acceptable_attribute_map
       transformed_hash = {}
-      openapi_types.each_pair do |key, type|
-        if attributes.key?(attribute_map[key]) && attributes[attribute_map[key]].nil?
+      acceptable_openapi_types.each_pair do |key, type|
+        if attributes.key?(map[key]) && attributes[map[key]].nil?
           transformed_hash["#{key}"] = nil
         elsif type =~ /\AArray<(.*)>/i
           # check to ensure the input is an array given that the attribute
           # is documented as an array but the input is not
-          if attributes[attribute_map[key]].is_a?(Array)
-            transformed_hash["#{key}"] = attributes[attribute_map[key]].map { |v| _deserialize($1, v) }
+          if attributes[map[key]].is_a?(Array)
+            transformed_hash["#{key}"] = attributes[map[key]].map { |v| _deserialize($1, v) }
           end
-        elsif !attributes[attribute_map[key]].nil?
-          transformed_hash["#{key}"] = _deserialize(type, attributes[attribute_map[key]])
+        elsif !attributes[map[key]].nil?
+          transformed_hash["#{key}"] = _deserialize(type, attributes[map[key]])
         end
       end
       new(transformed_hash)
@@ -159,10 +171,11 @@ def self.build_from_hash(attributes)
     # @return [Hash] Returns the object in the form of hash
     def to_hash
       hash = {}
-      self.class.attribute_map.each_pair do |attr, param|
+      # include attributes inherited from allOf parents (the nearest declaration wins)
+      self.class.acceptable_attribute_map.each_pair do |attr, param|
         value = self.send(attr)
         if value.nil?
-          is_nullable = self.class.openapi_nullable.include?(attr)
+          is_nullable = self.class.acceptable_openapi_nullable.include?(attr)
           next if !is_nullable || (is_nullable && !instance_variable_defined?(:"@#{attr}"))
         end
 
diff --git a/samples/client/petstore/ruby/lib/petstore/models/order.rb b/samples/client/petstore/ruby/lib/petstore/models/order.rb
index f7e7b4eb9117..8cebfcefa34e 100644
--- a/samples/client/petstore/ruby/lib/petstore/models/order.rb
+++ b/samples/client/petstore/ruby/lib/petstore/models/order.rb
@@ -90,6 +90,16 @@ def self.openapi_nullable
       ])
     end
 
+    # Returns attribute type mapping
+    def self.acceptable_openapi_types
+      openapi_types
+    end
+
+    # Returns the nullable attributes
+    def self.acceptable_openapi_nullable
+      openapi_nullable
+    end
+
     # Initializes the object
     # @param [Hash] attributes Model attributes in the form of hash
     def initialize(attributes = {})
@@ -191,18 +201,20 @@ def hash
     def self.build_from_hash(attributes)
       return nil unless attributes.is_a?(Hash)
       attributes = attributes.transform_keys(&:to_sym)
+      # include attributes inherited from allOf parents (the nearest declaration wins)
+      map = acceptable_attribute_map
       transformed_hash = {}
-      openapi_types.each_pair do |key, type|
-        if attributes.key?(attribute_map[key]) && attributes[attribute_map[key]].nil?
+      acceptable_openapi_types.each_pair do |key, type|
+        if attributes.key?(map[key]) && attributes[map[key]].nil?
           transformed_hash["#{key}"] = nil
         elsif type =~ /\AArray<(.*)>/i
           # check to ensure the input is an array given that the attribute
           # is documented as an array but the input is not
-          if attributes[attribute_map[key]].is_a?(Array)
-            transformed_hash["#{key}"] = attributes[attribute_map[key]].map { |v| _deserialize($1, v) }
+          if attributes[map[key]].is_a?(Array)
+            transformed_hash["#{key}"] = attributes[map[key]].map { |v| _deserialize($1, v) }
           end
-        elsif !attributes[attribute_map[key]].nil?
-          transformed_hash["#{key}"] = _deserialize(type, attributes[attribute_map[key]])
+        elsif !attributes[map[key]].nil?
+          transformed_hash["#{key}"] = _deserialize(type, attributes[map[key]])
         end
       end
       new(transformed_hash)
@@ -212,10 +224,11 @@ def self.build_from_hash(attributes)
     # @return [Hash] Returns the object in the form of hash
     def to_hash
       hash = {}
-      self.class.attribute_map.each_pair do |attr, param|
+      # include attributes inherited from allOf parents (the nearest declaration wins)
+      self.class.acceptable_attribute_map.each_pair do |attr, param|
         value = self.send(attr)
         if value.nil?
-          is_nullable = self.class.openapi_nullable.include?(attr)
+          is_nullable = self.class.acceptable_openapi_nullable.include?(attr)
           next if !is_nullable || (is_nullable && !instance_variable_defined?(:"@#{attr}"))
         end
 
diff --git a/samples/client/petstore/ruby/lib/petstore/models/outer_composite.rb b/samples/client/petstore/ruby/lib/petstore/models/outer_composite.rb
index 2245e8512600..afa9203ebde9 100644
--- a/samples/client/petstore/ruby/lib/petstore/models/outer_composite.rb
+++ b/samples/client/petstore/ruby/lib/petstore/models/outer_composite.rb
@@ -55,6 +55,16 @@ def self.openapi_nullable
       ])
     end
 
+    # Returns attribute type mapping
+    def self.acceptable_openapi_types
+      openapi_types
+    end
+
+    # Returns the nullable attributes
+    def self.acceptable_openapi_nullable
+      openapi_nullable
+    end
+
     # Initializes the object
     # @param [Hash] attributes Model attributes in the form of hash
     def initialize(attributes = {})
@@ -127,18 +137,20 @@ def hash
     def self.build_from_hash(attributes)
       return nil unless attributes.is_a?(Hash)
       attributes = attributes.transform_keys(&:to_sym)
+      # include attributes inherited from allOf parents (the nearest declaration wins)
+      map = acceptable_attribute_map
       transformed_hash = {}
-      openapi_types.each_pair do |key, type|
-        if attributes.key?(attribute_map[key]) && attributes[attribute_map[key]].nil?
+      acceptable_openapi_types.each_pair do |key, type|
+        if attributes.key?(map[key]) && attributes[map[key]].nil?
           transformed_hash["#{key}"] = nil
         elsif type =~ /\AArray<(.*)>/i
           # check to ensure the input is an array given that the attribute
           # is documented as an array but the input is not
-          if attributes[attribute_map[key]].is_a?(Array)
-            transformed_hash["#{key}"] = attributes[attribute_map[key]].map { |v| _deserialize($1, v) }
+          if attributes[map[key]].is_a?(Array)
+            transformed_hash["#{key}"] = attributes[map[key]].map { |v| _deserialize($1, v) }
           end
-        elsif !attributes[attribute_map[key]].nil?
-          transformed_hash["#{key}"] = _deserialize(type, attributes[attribute_map[key]])
+        elsif !attributes[map[key]].nil?
+          transformed_hash["#{key}"] = _deserialize(type, attributes[map[key]])
         end
       end
       new(transformed_hash)
@@ -148,10 +160,11 @@ def self.build_from_hash(attributes)
     # @return [Hash] Returns the object in the form of hash
     def to_hash
       hash = {}
-      self.class.attribute_map.each_pair do |attr, param|
+      # include attributes inherited from allOf parents (the nearest declaration wins)
+      self.class.acceptable_attribute_map.each_pair do |attr, param|
         value = self.send(attr)
         if value.nil?
-          is_nullable = self.class.openapi_nullable.include?(attr)
+          is_nullable = self.class.acceptable_openapi_nullable.include?(attr)
           next if !is_nullable || (is_nullable && !instance_variable_defined?(:"@#{attr}"))
         end
 
diff --git a/samples/client/petstore/ruby/lib/petstore/models/outer_object_with_enum_property.rb b/samples/client/petstore/ruby/lib/petstore/models/outer_object_with_enum_property.rb
index 8ffad20f8d89..1fd79229d4f6 100644
--- a/samples/client/petstore/ruby/lib/petstore/models/outer_object_with_enum_property.rb
+++ b/samples/client/petstore/ruby/lib/petstore/models/outer_object_with_enum_property.rb
@@ -69,6 +69,16 @@ def self.openapi_nullable
       ])
     end
 
+    # Returns attribute type mapping
+    def self.acceptable_openapi_types
+      openapi_types
+    end
+
+    # Returns the nullable attributes
+    def self.acceptable_openapi_nullable
+      openapi_nullable
+    end
+
     # Initializes the object
     # @param [Hash] attributes Model attributes in the form of hash
     def initialize(attributes = {})
@@ -148,18 +158,20 @@ def hash
     def self.build_from_hash(attributes)
       return nil unless attributes.is_a?(Hash)
       attributes = attributes.transform_keys(&:to_sym)
+      # include attributes inherited from allOf parents (the nearest declaration wins)
+      map = acceptable_attribute_map
       transformed_hash = {}
-      openapi_types.each_pair do |key, type|
-        if attributes.key?(attribute_map[key]) && attributes[attribute_map[key]].nil?
+      acceptable_openapi_types.each_pair do |key, type|
+        if attributes.key?(map[key]) && attributes[map[key]].nil?
           transformed_hash["#{key}"] = nil
         elsif type =~ /\AArray<(.*)>/i
           # check to ensure the input is an array given that the attribute
           # is documented as an array but the input is not
-          if attributes[attribute_map[key]].is_a?(Array)
-            transformed_hash["#{key}"] = attributes[attribute_map[key]].map { |v| _deserialize($1, v) }
+          if attributes[map[key]].is_a?(Array)
+            transformed_hash["#{key}"] = attributes[map[key]].map { |v| _deserialize($1, v) }
           end
-        elsif !attributes[attribute_map[key]].nil?
-          transformed_hash["#{key}"] = _deserialize(type, attributes[attribute_map[key]])
+        elsif !attributes[map[key]].nil?
+          transformed_hash["#{key}"] = _deserialize(type, attributes[map[key]])
         end
       end
       new(transformed_hash)
@@ -169,10 +181,11 @@ def self.build_from_hash(attributes)
     # @return [Hash] Returns the object in the form of hash
     def to_hash
       hash = {}
-      self.class.attribute_map.each_pair do |attr, param|
+      # include attributes inherited from allOf parents (the nearest declaration wins)
+      self.class.acceptable_attribute_map.each_pair do |attr, param|
         value = self.send(attr)
         if value.nil?
-          is_nullable = self.class.openapi_nullable.include?(attr)
+          is_nullable = self.class.acceptable_openapi_nullable.include?(attr)
           next if !is_nullable || (is_nullable && !instance_variable_defined?(:"@#{attr}"))
         end
 
diff --git a/samples/client/petstore/ruby/lib/petstore/models/pet.rb b/samples/client/petstore/ruby/lib/petstore/models/pet.rb
index e3594a1fb052..5a86112a15cf 100644
--- a/samples/client/petstore/ruby/lib/petstore/models/pet.rb
+++ b/samples/client/petstore/ruby/lib/petstore/models/pet.rb
@@ -90,6 +90,16 @@ def self.openapi_nullable
       ])
     end
 
+    # Returns attribute type mapping
+    def self.acceptable_openapi_types
+      openapi_types
+    end
+
+    # Returns the nullable attributes
+    def self.acceptable_openapi_nullable
+      openapi_nullable
+    end
+
     # Initializes the object
     # @param [Hash] attributes Model attributes in the form of hash
     def initialize(attributes = {})
@@ -227,18 +237,20 @@ def hash
     def self.build_from_hash(attributes)
       return nil unless attributes.is_a?(Hash)
       attributes = attributes.transform_keys(&:to_sym)
+      # include attributes inherited from allOf parents (the nearest declaration wins)
+      map = acceptable_attribute_map
       transformed_hash = {}
-      openapi_types.each_pair do |key, type|
-        if attributes.key?(attribute_map[key]) && attributes[attribute_map[key]].nil?
+      acceptable_openapi_types.each_pair do |key, type|
+        if attributes.key?(map[key]) && attributes[map[key]].nil?
           transformed_hash["#{key}"] = nil
         elsif type =~ /\AArray<(.*)>/i
           # check to ensure the input is an array given that the attribute
           # is documented as an array but the input is not
-          if attributes[attribute_map[key]].is_a?(Array)
-            transformed_hash["#{key}"] = attributes[attribute_map[key]].map { |v| _deserialize($1, v) }
+          if attributes[map[key]].is_a?(Array)
+            transformed_hash["#{key}"] = attributes[map[key]].map { |v| _deserialize($1, v) }
           end
-        elsif !attributes[attribute_map[key]].nil?
-          transformed_hash["#{key}"] = _deserialize(type, attributes[attribute_map[key]])
+        elsif !attributes[map[key]].nil?
+          transformed_hash["#{key}"] = _deserialize(type, attributes[map[key]])
         end
       end
       new(transformed_hash)
@@ -248,10 +260,11 @@ def self.build_from_hash(attributes)
     # @return [Hash] Returns the object in the form of hash
     def to_hash
       hash = {}
-      self.class.attribute_map.each_pair do |attr, param|
+      # include attributes inherited from allOf parents (the nearest declaration wins)
+      self.class.acceptable_attribute_map.each_pair do |attr, param|
         value = self.send(attr)
         if value.nil?
-          is_nullable = self.class.openapi_nullable.include?(attr)
+          is_nullable = self.class.acceptable_openapi_nullable.include?(attr)
           next if !is_nullable || (is_nullable && !instance_variable_defined?(:"@#{attr}"))
         end
 
diff --git a/samples/client/petstore/ruby/lib/petstore/models/property_name_mapping.rb b/samples/client/petstore/ruby/lib/petstore/models/property_name_mapping.rb
index 09e50b68dc06..ed1c46eeef88 100644
--- a/samples/client/petstore/ruby/lib/petstore/models/property_name_mapping.rb
+++ b/samples/client/petstore/ruby/lib/petstore/models/property_name_mapping.rb
@@ -59,6 +59,16 @@ def self.openapi_nullable
       ])
     end
 
+    # Returns attribute type mapping
+    def self.acceptable_openapi_types
+      openapi_types
+    end
+
+    # Returns the nullable attributes
+    def self.acceptable_openapi_nullable
+      openapi_nullable
+    end
+
     # Initializes the object
     # @param [Hash] attributes Model attributes in the form of hash
     def initialize(attributes = {})
@@ -136,18 +146,20 @@ def hash
     def self.build_from_hash(attributes)
       return nil unless attributes.is_a?(Hash)
       attributes = attributes.transform_keys(&:to_sym)
+      # include attributes inherited from allOf parents (the nearest declaration wins)
+      map = acceptable_attribute_map
       transformed_hash = {}
-      openapi_types.each_pair do |key, type|
-        if attributes.key?(attribute_map[key]) && attributes[attribute_map[key]].nil?
+      acceptable_openapi_types.each_pair do |key, type|
+        if attributes.key?(map[key]) && attributes[map[key]].nil?
           transformed_hash["#{key}"] = nil
         elsif type =~ /\AArray<(.*)>/i
           # check to ensure the input is an array given that the attribute
           # is documented as an array but the input is not
-          if attributes[attribute_map[key]].is_a?(Array)
-            transformed_hash["#{key}"] = attributes[attribute_map[key]].map { |v| _deserialize($1, v) }
+          if attributes[map[key]].is_a?(Array)
+            transformed_hash["#{key}"] = attributes[map[key]].map { |v| _deserialize($1, v) }
           end
-        elsif !attributes[attribute_map[key]].nil?
-          transformed_hash["#{key}"] = _deserialize(type, attributes[attribute_map[key]])
+        elsif !attributes[map[key]].nil?
+          transformed_hash["#{key}"] = _deserialize(type, attributes[map[key]])
         end
       end
       new(transformed_hash)
@@ -157,10 +169,11 @@ def self.build_from_hash(attributes)
     # @return [Hash] Returns the object in the form of hash
     def to_hash
       hash = {}
-      self.class.attribute_map.each_pair do |attr, param|
+      # include attributes inherited from allOf parents (the nearest declaration wins)
+      self.class.acceptable_attribute_map.each_pair do |attr, param|
         value = self.send(attr)
         if value.nil?
-          is_nullable = self.class.openapi_nullable.include?(attr)
+          is_nullable = self.class.acceptable_openapi_nullable.include?(attr)
           next if !is_nullable || (is_nullable && !instance_variable_defined?(:"@#{attr}"))
         end
 
diff --git a/samples/client/petstore/ruby/lib/petstore/models/read_only_first.rb b/samples/client/petstore/ruby/lib/petstore/models/read_only_first.rb
index c2121474ebb7..d008b4369a91 100644
--- a/samples/client/petstore/ruby/lib/petstore/models/read_only_first.rb
+++ b/samples/client/petstore/ruby/lib/petstore/models/read_only_first.rb
@@ -51,6 +51,16 @@ def self.openapi_nullable
       ])
     end
 
+    # Returns attribute type mapping
+    def self.acceptable_openapi_types
+      openapi_types
+    end
+
+    # Returns the nullable attributes
+    def self.acceptable_openapi_nullable
+      openapi_nullable
+    end
+
     # Initializes the object
     # @param [Hash] attributes Model attributes in the form of hash
     def initialize(attributes = {})
@@ -118,18 +128,20 @@ def hash
     def self.build_from_hash(attributes)
       return nil unless attributes.is_a?(Hash)
       attributes = attributes.transform_keys(&:to_sym)
+      # include attributes inherited from allOf parents (the nearest declaration wins)
+      map = acceptable_attribute_map
       transformed_hash = {}
-      openapi_types.each_pair do |key, type|
-        if attributes.key?(attribute_map[key]) && attributes[attribute_map[key]].nil?
+      acceptable_openapi_types.each_pair do |key, type|
+        if attributes.key?(map[key]) && attributes[map[key]].nil?
           transformed_hash["#{key}"] = nil
         elsif type =~ /\AArray<(.*)>/i
           # check to ensure the input is an array given that the attribute
           # is documented as an array but the input is not
-          if attributes[attribute_map[key]].is_a?(Array)
-            transformed_hash["#{key}"] = attributes[attribute_map[key]].map { |v| _deserialize($1, v) }
+          if attributes[map[key]].is_a?(Array)
+            transformed_hash["#{key}"] = attributes[map[key]].map { |v| _deserialize($1, v) }
           end
-        elsif !attributes[attribute_map[key]].nil?
-          transformed_hash["#{key}"] = _deserialize(type, attributes[attribute_map[key]])
+        elsif !attributes[map[key]].nil?
+          transformed_hash["#{key}"] = _deserialize(type, attributes[map[key]])
         end
       end
       new(transformed_hash)
@@ -139,10 +151,11 @@ def self.build_from_hash(attributes)
     # @return [Hash] Returns the object in the form of hash
     def to_hash
       hash = {}
-      self.class.attribute_map.each_pair do |attr, param|
+      # include attributes inherited from allOf parents (the nearest declaration wins)
+      self.class.acceptable_attribute_map.each_pair do |attr, param|
         value = self.send(attr)
         if value.nil?
-          is_nullable = self.class.openapi_nullable.include?(attr)
+          is_nullable = self.class.acceptable_openapi_nullable.include?(attr)
           next if !is_nullable || (is_nullable && !instance_variable_defined?(:"@#{attr}"))
         end
 
diff --git a/samples/client/petstore/ruby/lib/petstore/models/special_model_name.rb b/samples/client/petstore/ruby/lib/petstore/models/special_model_name.rb
index 9569fbfd13dd..b6d4135991be 100644
--- a/samples/client/petstore/ruby/lib/petstore/models/special_model_name.rb
+++ b/samples/client/petstore/ruby/lib/petstore/models/special_model_name.rb
@@ -47,6 +47,16 @@ def self.openapi_nullable
       ])
     end
 
+    # Returns attribute type mapping
+    def self.acceptable_openapi_types
+      openapi_types
+    end
+
+    # Returns the nullable attributes
+    def self.acceptable_openapi_nullable
+      openapi_nullable
+    end
+
     # Initializes the object
     # @param [Hash] attributes Model attributes in the form of hash
     def initialize(attributes = {})
@@ -109,18 +119,20 @@ def hash
     def self.build_from_hash(attributes)
       return nil unless attributes.is_a?(Hash)
       attributes = attributes.transform_keys(&:to_sym)
+      # include attributes inherited from allOf parents (the nearest declaration wins)
+      map = acceptable_attribute_map
       transformed_hash = {}
-      openapi_types.each_pair do |key, type|
-        if attributes.key?(attribute_map[key]) && attributes[attribute_map[key]].nil?
+      acceptable_openapi_types.each_pair do |key, type|
+        if attributes.key?(map[key]) && attributes[map[key]].nil?
           transformed_hash["#{key}"] = nil
         elsif type =~ /\AArray<(.*)>/i
           # check to ensure the input is an array given that the attribute
           # is documented as an array but the input is not
-          if attributes[attribute_map[key]].is_a?(Array)
-            transformed_hash["#{key}"] = attributes[attribute_map[key]].map { |v| _deserialize($1, v) }
+          if attributes[map[key]].is_a?(Array)
+            transformed_hash["#{key}"] = attributes[map[key]].map { |v| _deserialize($1, v) }
           end
-        elsif !attributes[attribute_map[key]].nil?
-          transformed_hash["#{key}"] = _deserialize(type, attributes[attribute_map[key]])
+        elsif !attributes[map[key]].nil?
+          transformed_hash["#{key}"] = _deserialize(type, attributes[map[key]])
         end
       end
       new(transformed_hash)
@@ -130,10 +142,11 @@ def self.build_from_hash(attributes)
     # @return [Hash] Returns the object in the form of hash
     def to_hash
       hash = {}
-      self.class.attribute_map.each_pair do |attr, param|
+      # include attributes inherited from allOf parents (the nearest declaration wins)
+      self.class.acceptable_attribute_map.each_pair do |attr, param|
         value = self.send(attr)
         if value.nil?
-          is_nullable = self.class.openapi_nullable.include?(attr)
+          is_nullable = self.class.acceptable_openapi_nullable.include?(attr)
           next if !is_nullable || (is_nullable && !instance_variable_defined?(:"@#{attr}"))
         end
 
diff --git a/samples/client/petstore/ruby/lib/petstore/models/tag.rb b/samples/client/petstore/ruby/lib/petstore/models/tag.rb
index 6d6f57468181..22589f4e58b3 100644
--- a/samples/client/petstore/ruby/lib/petstore/models/tag.rb
+++ b/samples/client/petstore/ruby/lib/petstore/models/tag.rb
@@ -51,6 +51,16 @@ def self.openapi_nullable
       ])
     end
 
+    # Returns attribute type mapping
+    def self.acceptable_openapi_types
+      openapi_types
+    end
+
+    # Returns the nullable attributes
+    def self.acceptable_openapi_nullable
+      openapi_nullable
+    end
+
     # Initializes the object
     # @param [Hash] attributes Model attributes in the form of hash
     def initialize(attributes = {})
@@ -118,18 +128,20 @@ def hash
     def self.build_from_hash(attributes)
       return nil unless attributes.is_a?(Hash)
       attributes = attributes.transform_keys(&:to_sym)
+      # include attributes inherited from allOf parents (the nearest declaration wins)
+      map = acceptable_attribute_map
       transformed_hash = {}
-      openapi_types.each_pair do |key, type|
-        if attributes.key?(attribute_map[key]) && attributes[attribute_map[key]].nil?
+      acceptable_openapi_types.each_pair do |key, type|
+        if attributes.key?(map[key]) && attributes[map[key]].nil?
           transformed_hash["#{key}"] = nil
         elsif type =~ /\AArray<(.*)>/i
           # check to ensure the input is an array given that the attribute
           # is documented as an array but the input is not
-          if attributes[attribute_map[key]].is_a?(Array)
-            transformed_hash["#{key}"] = attributes[attribute_map[key]].map { |v| _deserialize($1, v) }
+          if attributes[map[key]].is_a?(Array)
+            transformed_hash["#{key}"] = attributes[map[key]].map { |v| _deserialize($1, v) }
           end
-        elsif !attributes[attribute_map[key]].nil?
-          transformed_hash["#{key}"] = _deserialize(type, attributes[attribute_map[key]])
+        elsif !attributes[map[key]].nil?
+          transformed_hash["#{key}"] = _deserialize(type, attributes[map[key]])
         end
       end
       new(transformed_hash)
@@ -139,10 +151,11 @@ def self.build_from_hash(attributes)
     # @return [Hash] Returns the object in the form of hash
     def to_hash
       hash = {}
-      self.class.attribute_map.each_pair do |attr, param|
+      # include attributes inherited from allOf parents (the nearest declaration wins)
+      self.class.acceptable_attribute_map.each_pair do |attr, param|
         value = self.send(attr)
         if value.nil?
-          is_nullable = self.class.openapi_nullable.include?(attr)
+          is_nullable = self.class.acceptable_openapi_nullable.include?(attr)
           next if !is_nullable || (is_nullable && !instance_variable_defined?(:"@#{attr}"))
         end
 
diff --git a/samples/client/petstore/ruby/lib/petstore/models/test_inline_freeform_additional_properties_request.rb b/samples/client/petstore/ruby/lib/petstore/models/test_inline_freeform_additional_properties_request.rb
index dc481c119d22..9e52e64e286b 100644
--- a/samples/client/petstore/ruby/lib/petstore/models/test_inline_freeform_additional_properties_request.rb
+++ b/samples/client/petstore/ruby/lib/petstore/models/test_inline_freeform_additional_properties_request.rb
@@ -47,6 +47,16 @@ def self.openapi_nullable
       ])
     end
 
+    # Returns attribute type mapping
+    def self.acceptable_openapi_types
+      openapi_types
+    end
+
+    # Returns the nullable attributes
+    def self.acceptable_openapi_nullable
+      openapi_nullable
+    end
+
     # Initializes the object
     # @param [Hash] attributes Model attributes in the form of hash
     def initialize(attributes = {})
@@ -109,18 +119,20 @@ def hash
     def self.build_from_hash(attributes)
       return nil unless attributes.is_a?(Hash)
       attributes = attributes.transform_keys(&:to_sym)
+      # include attributes inherited from allOf parents (the nearest declaration wins)
+      map = acceptable_attribute_map
       transformed_hash = {}
-      openapi_types.each_pair do |key, type|
-        if attributes.key?(attribute_map[key]) && attributes[attribute_map[key]].nil?
+      acceptable_openapi_types.each_pair do |key, type|
+        if attributes.key?(map[key]) && attributes[map[key]].nil?
           transformed_hash["#{key}"] = nil
         elsif type =~ /\AArray<(.*)>/i
           # check to ensure the input is an array given that the attribute
           # is documented as an array but the input is not
-          if attributes[attribute_map[key]].is_a?(Array)
-            transformed_hash["#{key}"] = attributes[attribute_map[key]].map { |v| _deserialize($1, v) }
+          if attributes[map[key]].is_a?(Array)
+            transformed_hash["#{key}"] = attributes[map[key]].map { |v| _deserialize($1, v) }
           end
-        elsif !attributes[attribute_map[key]].nil?
-          transformed_hash["#{key}"] = _deserialize(type, attributes[attribute_map[key]])
+        elsif !attributes[map[key]].nil?
+          transformed_hash["#{key}"] = _deserialize(type, attributes[map[key]])
         end
       end
       new(transformed_hash)
@@ -130,10 +142,11 @@ def self.build_from_hash(attributes)
     # @return [Hash] Returns the object in the form of hash
     def to_hash
       hash = {}
-      self.class.attribute_map.each_pair do |attr, param|
+      # include attributes inherited from allOf parents (the nearest declaration wins)
+      self.class.acceptable_attribute_map.each_pair do |attr, param|
         value = self.send(attr)
         if value.nil?
-          is_nullable = self.class.openapi_nullable.include?(attr)
+          is_nullable = self.class.acceptable_openapi_nullable.include?(attr)
           next if !is_nullable || (is_nullable && !instance_variable_defined?(:"@#{attr}"))
         end
 
diff --git a/samples/client/petstore/ruby/lib/petstore/models/user.rb b/samples/client/petstore/ruby/lib/petstore/models/user.rb
index 9b06f2ff6d7a..4b67db8214e2 100644
--- a/samples/client/petstore/ruby/lib/petstore/models/user.rb
+++ b/samples/client/petstore/ruby/lib/petstore/models/user.rb
@@ -76,6 +76,16 @@ def self.openapi_nullable
       ])
     end
 
+    # Returns attribute type mapping
+    def self.acceptable_openapi_types
+      openapi_types
+    end
+
+    # Returns the nullable attributes
+    def self.acceptable_openapi_nullable
+      openapi_nullable
+    end
+
     # Initializes the object
     # @param [Hash] attributes Model attributes in the form of hash
     def initialize(attributes = {})
@@ -173,18 +183,20 @@ def hash
     def self.build_from_hash(attributes)
       return nil unless attributes.is_a?(Hash)
       attributes = attributes.transform_keys(&:to_sym)
+      # include attributes inherited from allOf parents (the nearest declaration wins)
+      map = acceptable_attribute_map
       transformed_hash = {}
-      openapi_types.each_pair do |key, type|
-        if attributes.key?(attribute_map[key]) && attributes[attribute_map[key]].nil?
+      acceptable_openapi_types.each_pair do |key, type|
+        if attributes.key?(map[key]) && attributes[map[key]].nil?
           transformed_hash["#{key}"] = nil
         elsif type =~ /\AArray<(.*)>/i
           # check to ensure the input is an array given that the attribute
           # is documented as an array but the input is not
-          if attributes[attribute_map[key]].is_a?(Array)
-            transformed_hash["#{key}"] = attributes[attribute_map[key]].map { |v| _deserialize($1, v) }
+          if attributes[map[key]].is_a?(Array)
+            transformed_hash["#{key}"] = attributes[map[key]].map { |v| _deserialize($1, v) }
           end
-        elsif !attributes[attribute_map[key]].nil?
-          transformed_hash["#{key}"] = _deserialize(type, attributes[attribute_map[key]])
+        elsif !attributes[map[key]].nil?
+          transformed_hash["#{key}"] = _deserialize(type, attributes[map[key]])
         end
       end
       new(transformed_hash)
@@ -194,10 +206,11 @@ def self.build_from_hash(attributes)
     # @return [Hash] Returns the object in the form of hash
     def to_hash
       hash = {}
-      self.class.attribute_map.each_pair do |attr, param|
+      # include attributes inherited from allOf parents (the nearest declaration wins)
+      self.class.acceptable_attribute_map.each_pair do |attr, param|
         value = self.send(attr)
         if value.nil?
-          is_nullable = self.class.openapi_nullable.include?(attr)
+          is_nullable = self.class.acceptable_openapi_nullable.include?(attr)
           next if !is_nullable || (is_nullable && !instance_variable_defined?(:"@#{attr}"))
         end
 
diff --git a/samples/client/petstore/ruby/lib/petstore/models/whale.rb b/samples/client/petstore/ruby/lib/petstore/models/whale.rb
index 23249be434e4..f29de72ecb1a 100644
--- a/samples/client/petstore/ruby/lib/petstore/models/whale.rb
+++ b/samples/client/petstore/ruby/lib/petstore/models/whale.rb
@@ -55,6 +55,16 @@ def self.openapi_nullable
       ])
     end
 
+    # Returns attribute type mapping
+    def self.acceptable_openapi_types
+      openapi_types
+    end
+
+    # Returns the nullable attributes
+    def self.acceptable_openapi_nullable
+      openapi_nullable
+    end
+
     # Initializes the object
     # @param [Hash] attributes Model attributes in the form of hash
     def initialize(attributes = {})
@@ -144,18 +154,20 @@ def hash
     def self.build_from_hash(attributes)
       return nil unless attributes.is_a?(Hash)
       attributes = attributes.transform_keys(&:to_sym)
+      # include attributes inherited from allOf parents (the nearest declaration wins)
+      map = acceptable_attribute_map
       transformed_hash = {}
-      openapi_types.each_pair do |key, type|
-        if attributes.key?(attribute_map[key]) && attributes[attribute_map[key]].nil?
+      acceptable_openapi_types.each_pair do |key, type|
+        if attributes.key?(map[key]) && attributes[map[key]].nil?
           transformed_hash["#{key}"] = nil
         elsif type =~ /\AArray<(.*)>/i
           # check to ensure the input is an array given that the attribute
           # is documented as an array but the input is not
-          if attributes[attribute_map[key]].is_a?(Array)
-            transformed_hash["#{key}"] = attributes[attribute_map[key]].map { |v| _deserialize($1, v) }
+          if attributes[map[key]].is_a?(Array)
+            transformed_hash["#{key}"] = attributes[map[key]].map { |v| _deserialize($1, v) }
           end
-        elsif !attributes[attribute_map[key]].nil?
-          transformed_hash["#{key}"] = _deserialize(type, attributes[attribute_map[key]])
+        elsif !attributes[map[key]].nil?
+          transformed_hash["#{key}"] = _deserialize(type, attributes[map[key]])
         end
       end
       new(transformed_hash)
@@ -165,10 +177,11 @@ def self.build_from_hash(attributes)
     # @return [Hash] Returns the object in the form of hash
     def to_hash
       hash = {}
-      self.class.attribute_map.each_pair do |attr, param|
+      # include attributes inherited from allOf parents (the nearest declaration wins)
+      self.class.acceptable_attribute_map.each_pair do |attr, param|
         value = self.send(attr)
         if value.nil?
-          is_nullable = self.class.openapi_nullable.include?(attr)
+          is_nullable = self.class.acceptable_openapi_nullable.include?(attr)
           next if !is_nullable || (is_nullable && !instance_variable_defined?(:"@#{attr}"))
         end
 
diff --git a/samples/client/petstore/ruby/lib/petstore/models/zebra.rb b/samples/client/petstore/ruby/lib/petstore/models/zebra.rb
index 10e910f409f7..79771e498151 100644
--- a/samples/client/petstore/ruby/lib/petstore/models/zebra.rb
+++ b/samples/client/petstore/ruby/lib/petstore/models/zebra.rb
@@ -73,6 +73,16 @@ def self.openapi_nullable
       ])
     end
 
+    # Returns attribute type mapping
+    def self.acceptable_openapi_types
+      openapi_types
+    end
+
+    # Returns the nullable attributes
+    def self.acceptable_openapi_nullable
+      openapi_nullable
+    end
+
     # Initializes the object
     # @param [Hash] attributes Model attributes in the form of hash
     def initialize(attributes = {})
@@ -169,18 +179,20 @@ def hash
     def self.build_from_hash(attributes)
       return nil unless attributes.is_a?(Hash)
       attributes = attributes.transform_keys(&:to_sym)
+      # include attributes inherited from allOf parents (the nearest declaration wins)
+      map = acceptable_attribute_map
       transformed_hash = {}
-      openapi_types.each_pair do |key, type|
-        if attributes.key?(attribute_map[key]) && attributes[attribute_map[key]].nil?
+      acceptable_openapi_types.each_pair do |key, type|
+        if attributes.key?(map[key]) && attributes[map[key]].nil?
           transformed_hash["#{key}"] = nil
         elsif type =~ /\AArray<(.*)>/i
           # check to ensure the input is an array given that the attribute
           # is documented as an array but the input is not
-          if attributes[attribute_map[key]].is_a?(Array)
-            transformed_hash["#{key}"] = attributes[attribute_map[key]].map { |v| _deserialize($1, v) }
+          if attributes[map[key]].is_a?(Array)
+            transformed_hash["#{key}"] = attributes[map[key]].map { |v| _deserialize($1, v) }
           end
-        elsif !attributes[attribute_map[key]].nil?
-          transformed_hash["#{key}"] = _deserialize(type, attributes[attribute_map[key]])
+        elsif !attributes[map[key]].nil?
+          transformed_hash["#{key}"] = _deserialize(type, attributes[map[key]])
         end
       end
       new(transformed_hash)
@@ -190,10 +202,11 @@ def self.build_from_hash(attributes)
     # @return [Hash] Returns the object in the form of hash
     def to_hash
       hash = {}
-      self.class.attribute_map.each_pair do |attr, param|
+      # include attributes inherited from allOf parents (the nearest declaration wins)
+      self.class.acceptable_attribute_map.each_pair do |attr, param|
         value = self.send(attr)
         if value.nil?
-          is_nullable = self.class.openapi_nullable.include?(attr)
+          is_nullable = self.class.acceptable_openapi_nullable.include?(attr)
           next if !is_nullable || (is_nullable && !instance_variable_defined?(:"@#{attr}"))
         end
 
diff --git a/samples/client/petstore/ruby/spec/custom/base_object_spec.rb b/samples/client/petstore/ruby/spec/custom/base_object_spec.rb
index a046c5bd4e11..bc0ed63000b4 100644
--- a/samples/client/petstore/ruby/spec/custom/base_object_spec.rb
+++ b/samples/client/petstore/ruby/spec/custom/base_object_spec.rb
@@ -166,4 +166,34 @@ def initialize(attributes = {})
       expect(obj.to_hash).to eq(expect_data)
     end
   end
+
+  describe 'attributes inherited from an allOf parent' do
+    it 'build_from_hash and to_hash include the parent attributes' do
+      cat = Petstore::Cat.build_from_hash({ 'className' => 'Cat', 'color' => 'black', 'declawed' => true })
+
+      expect(cat).to be_instance_of(Petstore::Cat)
+      expect(cat.class_name).to eq('Cat')
+      expect(cat.color).to eq('black')
+      expect(cat.declawed).to eq(true)
+      expect(cat.to_hash).to eq({ className: 'Cat', color: 'black', declawed: true })
+    end
+
+    # passes on master too: guards that a subclass narrowing attribute_map is not handed its parent's attributes
+    it 'a subclass that narrows attribute_map is only handed the attributes it accepts' do
+      narrowed = Class.new(Petstore::Animal) do
+        def self.attribute_map
+          { :class_name => :className }
+        end
+
+        def self.openapi_types
+          { :class_name => :'String' }
+        end
+      end
+
+      obj = narrowed.build_from_hash({ 'className' => 'Cat', 'color' => 'black' })
+
+      expect(obj.class_name).to eq('Cat')
+      expect(obj.to_hash).to eq({ className: 'Cat' })
+    end
+  end
 end
diff --git a/samples/openapi3/client/features/generate-alias-as-model/ruby-client/lib/petstore/models/array_alias.rb b/samples/openapi3/client/features/generate-alias-as-model/ruby-client/lib/petstore/models/array_alias.rb
index 9ffe5b9100b1..857c8a4b76da 100644
--- a/samples/openapi3/client/features/generate-alias-as-model/ruby-client/lib/petstore/models/array_alias.rb
+++ b/samples/openapi3/client/features/generate-alias-as-model/ruby-client/lib/petstore/models/array_alias.rb
@@ -21,12 +21,12 @@ def self.attribute_map
       }
     end
 
-    # Returns attribute mapping this model knows about, including the ones defined in its parent(s)
+    # Returns attribute mapping this model knows about
     def self.acceptable_attribute_map
-      superclass.acceptable_attribute_map.merge(attribute_map)
+      attribute_map
     end
 
-    # Returns all the JSON keys this model knows about, including the ones defined in its parent(s)
+    # Returns all the JSON keys this model knows about
     def self.acceptable_attributes
       acceptable_attribute_map.values
     end
@@ -43,6 +43,16 @@ def self.openapi_nullable
       ])
     end
 
+    # Returns attribute type mapping
+    def self.acceptable_openapi_types
+      openapi_types
+    end
+
+    # Returns the nullable attributes
+    def self.acceptable_openapi_nullable
+      openapi_nullable
+    end
+
     # Initializes the object
     # @param [Hash] attributes Model attributes in the form of hash
     def initialize(attributes = {})
@@ -58,9 +68,6 @@ def initialize(attributes = {})
         end
         h[k.to_sym] = v
       }
-
-      # call parent's initialize
-      super(attributes)
     end
 
     # Show invalid properties with the reasons. Usually used together with valid?
@@ -102,20 +109,21 @@ def hash
     # @return [Object] Returns the model itself
     def self.build_from_hash(attributes)
       return nil unless attributes.is_a?(Hash)
-      super(attributes)
       attributes = attributes.transform_keys(&:to_sym)
+      # include attributes inherited from allOf parents (the nearest declaration wins)
+      map = acceptable_attribute_map
       transformed_hash = {}
-      openapi_types.each_pair do |key, type|
-        if attributes.key?(attribute_map[key]) && attributes[attribute_map[key]].nil?
+      acceptable_openapi_types.each_pair do |key, type|
+        if attributes.key?(map[key]) && attributes[map[key]].nil?
           transformed_hash["#{key}"] = nil
         elsif type =~ /\AArray<(.*)>/i
           # check to ensure the input is an array given that the attribute
           # is documented as an array but the input is not
-          if attributes[attribute_map[key]].is_a?(Array)
-            transformed_hash["#{key}"] = attributes[attribute_map[key]].map { |v| _deserialize($1, v) }
+          if attributes[map[key]].is_a?(Array)
+            transformed_hash["#{key}"] = attributes[map[key]].map { |v| _deserialize($1, v) }
           end
-        elsif !attributes[attribute_map[key]].nil?
-          transformed_hash["#{key}"] = _deserialize(type, attributes[attribute_map[key]])
+        elsif !attributes[map[key]].nil?
+          transformed_hash["#{key}"] = _deserialize(type, attributes[map[key]])
         end
       end
       new(transformed_hash)
@@ -124,11 +132,12 @@ def self.build_from_hash(attributes)
     # Returns the object in the form of hash
     # @return [Hash] Returns the object in the form of hash
     def to_hash
-      hash = super
-      self.class.attribute_map.each_pair do |attr, param|
+      hash = {}
+      # include attributes inherited from allOf parents (the nearest declaration wins)
+      self.class.acceptable_attribute_map.each_pair do |attr, param|
         value = self.send(attr)
         if value.nil?
-          is_nullable = self.class.openapi_nullable.include?(attr)
+          is_nullable = self.class.acceptable_openapi_nullable.include?(attr)
           next if !is_nullable || (is_nullable && !instance_variable_defined?(:"@#{attr}"))
         end
 
diff --git a/samples/openapi3/client/features/generate-alias-as-model/ruby-client/lib/petstore/models/map_alias.rb b/samples/openapi3/client/features/generate-alias-as-model/ruby-client/lib/petstore/models/map_alias.rb
index 431c5fbcab6c..78aa109d56b0 100644
--- a/samples/openapi3/client/features/generate-alias-as-model/ruby-client/lib/petstore/models/map_alias.rb
+++ b/samples/openapi3/client/features/generate-alias-as-model/ruby-client/lib/petstore/models/map_alias.rb
@@ -43,6 +43,16 @@ def self.openapi_nullable
       ])
     end
 
+    # Returns attribute type mapping
+    def self.acceptable_openapi_types
+      openapi_types
+    end
+
+    # Returns the nullable attributes
+    def self.acceptable_openapi_nullable
+      openapi_nullable
+    end
+
     # Initializes the object
     # @param [Hash] attributes Model attributes in the form of hash
     def initialize(attributes = {})
@@ -100,18 +110,20 @@ def hash
     def self.build_from_hash(attributes)
       return nil unless attributes.is_a?(Hash)
       attributes = attributes.transform_keys(&:to_sym)
+      # include attributes inherited from allOf parents (the nearest declaration wins)
+      map = acceptable_attribute_map
       transformed_hash = {}
-      openapi_types.each_pair do |key, type|
-        if attributes.key?(attribute_map[key]) && attributes[attribute_map[key]].nil?
+      acceptable_openapi_types.each_pair do |key, type|
+        if attributes.key?(map[key]) && attributes[map[key]].nil?
           transformed_hash["#{key}"] = nil
         elsif type =~ /\AArray<(.*)>/i
           # check to ensure the input is an array given that the attribute
           # is documented as an array but the input is not
-          if attributes[attribute_map[key]].is_a?(Array)
-            transformed_hash["#{key}"] = attributes[attribute_map[key]].map { |v| _deserialize($1, v) }
+          if attributes[map[key]].is_a?(Array)
+            transformed_hash["#{key}"] = attributes[map[key]].map { |v| _deserialize($1, v) }
           end
-        elsif !attributes[attribute_map[key]].nil?
-          transformed_hash["#{key}"] = _deserialize(type, attributes[attribute_map[key]])
+        elsif !attributes[map[key]].nil?
+          transformed_hash["#{key}"] = _deserialize(type, attributes[map[key]])
         end
       end
       new(transformed_hash)
@@ -121,10 +133,11 @@ def self.build_from_hash(attributes)
     # @return [Hash] Returns the object in the form of hash
     def to_hash
       hash = {}
-      self.class.attribute_map.each_pair do |attr, param|
+      # include attributes inherited from allOf parents (the nearest declaration wins)
+      self.class.acceptable_attribute_map.each_pair do |attr, param|
         value = self.send(attr)
         if value.nil?
-          is_nullable = self.class.openapi_nullable.include?(attr)
+          is_nullable = self.class.acceptable_openapi_nullable.include?(attr)
           next if !is_nullable || (is_nullable && !instance_variable_defined?(:"@#{attr}"))
         end