diff --git a/CHANGELOG.md b/CHANGELOG.md
index 940e9885..f39b091e 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -1,3 +1,8 @@
+### v4.25.1 (2026-08-11)
+* * *
+### Bug Fixes: 
+- Filter operators `in`, `not_in` and `between` are now sent as a single form field by `URLFormEncoder`, at any nesting depth. Filters on export operations, such as `ramp[effective_from][between]`, were index-encoded and therefore ignored by the API.
+
 ### v4.25.0 (2026-07-30)
 * * *
 ### New Resources:
diff --git a/VERSION b/VERSION
index 4d9fbcf2..72e19f2f 100644
--- a/VERSION
+++ b/VERSION
@@ -1 +1 @@
-4.25.0
+4.25.1
diff --git a/src/ValueObjects/Encoders/URLFormEncoder.php b/src/ValueObjects/Encoders/URLFormEncoder.php
index 733c5510..ff4a2b4e 100644
--- a/src/ValueObjects/Encoders/URLFormEncoder.php
+++ b/src/ValueObjects/Encoders/URLFormEncoder.php
@@ -6,6 +6,12 @@
 
 class URLFormEncoder implements ParamEncoderInterface
 {
+    /**
+     * Filter operators whose value is the whole array, sent as a single field
+     * (e.g. updated_at[between]=[1704067200,1717199999]).
+     */
+    private const ARRAY_OPERATORS = ['in', 'not_in', 'between'];
+
     /**
      * @param array $params.
      * @param array $jsonKeys.
@@ -33,6 +39,12 @@ private static function serialize($value, $prefix = null, $idx = null, $jsonKeys
                     (!is_null($prefix) ? '[' . $usK . ']' : $usK) .
                     (!is_null($idx) ? '[' . $idx . ']' : '');
                 $serialized[$key] = is_string($v) ? $v : json_encode((is_array($v) && $v === []) ? (object)[] : $v);
+            } else if (is_array($v) && $v !== [] && !is_int($k) && in_array(Util::toUnderscoreFromCamelCase($k), self::ARRAY_OPERATORS, true)) {
+                // An empty filter is not a filter, so it falls through to the
+                // recursion below and leaves nothing in the request.
+                $usK = Util::toUnderscoreFromCamelCase($k);
+                $key = (!is_null($prefix) ? $prefix . '[' . $usK . ']' : $usK) . (!is_null($idx) ? '[' . $idx . ']' : '');
+                $serialized[$key] = json_encode($v);
             } else if (is_array($v) && !is_int($k)) {
                 $tempPrefix = (!is_null($prefix)) ? $prefix . '[' . Util::toUnderscoreFromCamelCase($k) . ']' : Util::toUnderscoreFromCamelCase($k);
                 $serialized = array_merge($serialized, self::serialize($v, $tempPrefix, null, $jsonKeys, $level + 1));
diff --git a/src/Version.php b/src/Version.php
index d50c6817..aa6a6013 100644
--- a/src/Version.php
+++ b/src/Version.php
@@ -4,7 +4,7 @@
 
 final class Version
 {
-	const VERSION = '4.25.0';
+	const VERSION = '4.25.1';
 }
 
 ?>
\ No newline at end of file
diff --git a/tests/ValueObjects/Encoder/URLFormEncoderTest.php b/tests/ValueObjects/Encoder/URLFormEncoderTest.php
index 5f4b3178..880876f0 100644
--- a/tests/ValueObjects/Encoder/URLFormEncoderTest.php
+++ b/tests/ValueObjects/Encoder/URLFormEncoderTest.php
@@ -217,4 +217,56 @@ public function testEncodeParamsShouldNotUseArrayBasedIndexingForJsonArray(): vo
         $this->assertIsString($encoded);
         $this->assertSame("id=foo&name=foo&discount_percentage=10&apply_on=each_specified_item&item_constraints%5Bconstraint%5D%5B0%5D=specific&item_constraints%5Bitem_type%5D%5B0%5D=plan&item_constraints%5Bitem_price_ids%5D%5B0%5D=%5B%22some_price_id%22%5D", $encoded);
     }
+
+    /** Filter operators carry the whole array in one field, at any nesting depth. */
+    /** ramp[effective_from][between]=[1704067200,1717199999]&ramp[status][in]=["scheduled","draft"] */
+    public function testEncodeParamsWithFilterArrayOperators(): void
+    {
+        $params = [
+            'export_type' => 'import_friendly_data',
+            'ramp' => [
+                'effective_from' => [
+                    'between' => [1704067200, 1717199999],
+                ],
+                'status' => [
+                    'in' => ['scheduled', 'draft'],
+                ],
+            ],
+        ];
+        $encoded = URLFormEncoder::encode($params);
+        $this->assertIsString($encoded);
+        $this->assertSame(
+            "export_type=import_friendly_data&ramp%5Beffective_from%5D%5Bbetween%5D=%5B1704067200%2C1717199999%5D&ramp%5Bstatus%5D%5Bin%5D=%5B%22scheduled%22%2C%22draft%22%5D",
+            $encoded
+        );
+    }
+
+    /** Top-level filters on non-list requests get the same treatment. */
+    /** updated_at[between]=[1704067200,1717199999] */
+    public function testEncodeParamsWithTopLevelFilterArrayOperator(): void
+    {
+        $params = [
+            'updated_at' => [
+                'between' => [1704067200, 1717199999],
+            ],
+        ];
+        $encoded = URLFormEncoder::encode($params);
+        $this->assertIsString($encoded);
+        $this->assertSame("updated_at%5Bbetween%5D=%5B1704067200%2C1717199999%5D", $encoded);
+    }
+
+    /** An empty filter operator is left out of the request entirely. */
+    /** limit=5 */
+    public function testEncodeParamsWithEmptyFilterArrayOperator(): void
+    {
+        $params = [
+            'limit' => 5,
+            'updated_at' => [
+                'between' => [],
+            ],
+        ];
+        $encoded = URLFormEncoder::encode($params);
+        $this->assertIsString($encoded);
+        $this->assertSame("limit=5", $encoded);
+    }
 }