diff --git a/.claude/backend_development.md b/.claude/backend_development.md
index aa45235..9eb5e35 100644
--- a/.claude/backend_development.md
+++ b/.claude/backend_development.md
@@ -32,7 +32,7 @@ rhosocial-activerecord-{backend}/
 │               └── impl/
 │                   └── {backend}/
 │                       ├── __init__.py
-│                       ├── backend.py       # Main backend implementation
+│                       ├── backend/         # sync + async backend classes
 │                       ├── adapters.py      # Backend-specific type adapters
 │                       ├── config.py        # Connection configuration
 │                       ├── dialect.py       # SQL dialect handling
@@ -114,7 +114,7 @@ Expression.to_sql() -> Dialect.format_*() -> SQL string and parameters
 - `operators.py`: SQL operations (binary, unary, arithmetic expressions)
 - `predicates.py`: SQL predicate expressions (WHERE clause conditions)
 - `query_parts.py`: SQL query clauses (WHERE, GROUP BY, HAVING, ORDER BY, etc.)
-- `statements.py`: DML/DQL/DDL statements (SELECT, INSERT, UPDATE, DELETE, etc.)
+- `statements/`: DML/DQL/DDL statements (a package, not a module) (SELECT, INSERT, UPDATE, DELETE, etc.)
 - `functions.py`: Standalone factory functions for creating SQL expressions
 - `aggregates.py`: SQL aggregation expressions and functions
 - `advanced_functions.py`: Advanced SQL functions (CASE, CAST, EXISTS, window functions)
@@ -149,8 +149,9 @@ Every backend must implement the `StorageBackend` abstract base class. This is t
 ```python
 # backend.py
 from typing import Any, Dict, List, Optional, Tuple, Type
-from ...base import StorageBackend, ConnectionConfig
-from ...type_adapter import SQLTypeAdapter
+from rhosocial.activerecord.backend.base import StorageBackend
+from rhosocial.activerecord.backend.config import ConnectionConfig
+from rhosocial.activerecord.backend.type_adapter import SQLTypeAdapter
 
 class MyBackend(StorageBackend):
     """Implementation of MyDatabase backend using native driver."""
@@ -175,7 +176,8 @@ class MyBackend(StorageBackend):
         """Check if connection is valid."""
         pass
 
-    def execute(self, sql: str, params: Optional[Tuple] = None, returning: Optional[Union[bool, List[str], ReturningOptions]] = None, column_adapters: Optional[Dict[str, Tuple[SQLTypeAdapter, Type]]] = None) -> QueryResult:
+    def execute(self, sql: str, params: Optional[Tuple] = None, *,
+                options: Optional[ExecutionOptions] = None) -> QueryResult:
         """Executes a SQL query."""
         pass
     
@@ -197,10 +199,6 @@ class MyBackend(StorageBackend):
         """
         pass
 
-    def _initialize_capabilities(self) -> DatabaseCapabilities:
-        """Declare all features supported by this backend."""
-        pass
-
     def _handle_error(self, error: Exception) -> None:
         """Catch driver-specific exceptions and raise standard errors."""
         pass
@@ -241,10 +239,10 @@ Define an immutable configuration class for your backend.
 # config.py
 from dataclasses import dataclass, field
 from typing import Optional, Dict, Any
-from rhosocial.activerecord.backend.config import BaseConfig
+from rhosocial.activerecord.backend.config import ConnectionConfig
 
-@dataclass(frozen=True)
-class MyDatabaseConfig(BaseConfig):
+@dataclass
+class MyDatabaseConfig(ConnectionConfig):
     host: str = "localhost"
     port: int = 5432
     database: str
@@ -366,34 +364,20 @@ Every dialect inherits from:
 
 ```python
 # dialect.py
-from rhosocial.activerecord.backend.dialect import (
-    SQLDialect, ReturningClauseHandler, TypeMapping
-)
-from typing import Dict, List, Optional
+from rhosocial.activerecord.backend.dialect.base import SQLDialectBase
+from typing import Optional, Tuple
 
-class MyDatabaseDialect(SQLDialect):
+class MyDatabaseDialect(SQLDialectBase):
     def __init__(self):
         super().__init__()
         self.returning_handler = MyDatabaseReturningHandler()
     
-    def quote_identifier(self, identifier: str) -> str: return f'"{identifier}"'
-    def get_placeholder(self, name: str = None) -> str: return "?"
-    
-    def format_limit_offset(self, sql: str, limit: Optional[int], offset: Optional[int]) -> str:
-        if limit is not None: sql += f" LIMIT {limit}"
-        if offset is not None: sql += f" OFFSET {offset}"
-        return sql
-    
-    def get_type_mappings(self) -> Dict[str, TypeMapping]:
-        return {"INTEGER": TypeMapping("INTEGER"), "TEXT": TypeMapping("TEXT"), ...}
+    def get_parameter_placeholder(self, position: int = 0) -> str:
+        return "?"
 
-class MyDatabaseReturningHandler(ReturningClauseHandler):
-    @property
-    def is_supported(self) -> bool: return True
-    
-    def format_clause(self, columns: Optional[List[str]] = None) -> str:
-        cols = "*" if not columns else ', '.join(self.dialect.quote_identifier(c) for c in columns)
-        return f"RETURNING {cols}"
+# Identifier quoting is inherited from SQLDialectBase.format_identifier;
+# LIMIT/OFFSET come from the DQL mixins; type mapping is not a dialect
+# method but a set of SQLTypeAdapter registrations on the backend.
 ```
 
 ### 4. The Type Adaptation System
@@ -565,7 +549,7 @@ This checklist summarizes all the required and recommended steps for creating a
     - [ ] Implement `get_default_adapter_suggestions` to define the conversion strategy.
 - [ ] Implement `Transaction Management`.
 - [ ] Implement `Error Handling` to map driver exceptions.
-- [ ] Implement `Feature Detection` to declare capabilities.
+- [ ] Implement the `supports_*` capability switches your dialect needs.
 - [ ] If providing an `AsyncStorageBackend`, ensure it has **Functional Equivalence** with the sync version.
 
 ### Required Tests
diff --git a/.claude/code_style.md b/.claude/code_style.md
index 048b351..8dc35fc 100644
--- a/.claude/code_style.md
+++ b/.claude/code_style.md
@@ -56,7 +56,7 @@ from pydantic import BaseModel, Field
 
 # Local application imports
 from rhosocial.activerecord.model import ActiveRecord
-from rhosocial.activerecord.backend import StorageBackend
+from rhosocial.activerecord.backend.base import StorageBackend
 
 # Relative imports (within same package)
 from .base import BaseActiveRecord
@@ -65,7 +65,7 @@ from ..interface import IActiveRecord
 
 ### Line Length and Wrapping
 
-- Maximum line length: 100 characters
+- Maximum line length: 120 characters (ruff `line-length = 120`; black formats to 100, but 100 is not the limit)
 - Wrap long lines using parentheses:
 
 ```python
@@ -291,7 +291,7 @@ from typing import annotations
 
 import third_party
 
-from rhosocial.activerecord import local
+from rhosocial.activerecord.model import ActiveRecord
 from . import relative
 
 # Constants
@@ -414,12 +414,12 @@ raise DatabaseError(
 """Test module for specific feature."""
 
 import pytest
-from rhosocial.activerecord import Model
+from rhosocial.activerecord.model import ActiveRecord
 
 # Fixtures at top
 @pytest.fixture
 def sample_model():
-    return Model(name="test")
+    return ActiveRecord(name="test")
 
 # Test classes for organization
 class TestCRUDOperations:
@@ -603,13 +603,12 @@ def transaction(backend: StorageBackend):
 ### Mixin Classes
 
 ```python
-class TimestampMixin:
-    """Add timestamp fields to models."""
-    created_at: datetime = Field(default_factory=datetime.now)
-    updated_at: Optional[datetime] = None
-    
-    def before_save(self):
-        self.updated_at = datetime.now()
+# TimestampMixin declares NO fields: it hooks
+# ModelEvent.BEFORE_INSERT / BEFORE_UPDATE and requires the model to
+# declare the fields itself, named per __created_at_field__ /
+# __updated_at_field__. Use DefaultTimestampMixin to get them declared
+# for you. There is no before_save() hook -- lifecycle is registered
+# with instance.on(ModelEvent.X, handler).
 ```
 
 ## Expression-Dialect System Coding Standards
@@ -687,7 +686,7 @@ class MyExpression(mixins.ArithmeticMixin, mixins.ComparisonMixin, bases.SQLValu
 
     def to_sql(self) -> 'bases.SQLQueryAndParams':
         # Delegate formatting to dialect
-        formatted_value = self.dialect.format_string_literal(self.value)
+        formatted_value = self.dialect.format_literal(self.value)
         return formatted_value, (self.value,)
 ```
 
@@ -705,7 +704,7 @@ def format_identifier(self, identifier: str) -> str:
 - [ ] Path comment at file start matches actual location
 - [ ] All functions/classes have docstrings
 - [ ] Type hints on all function signatures
-- [ ] No line exceeds 100 characters
+- [ ] No line exceeds 120 characters
 - [ ] Imports sorted and grouped correctly
 - [ ] No commented-out code
 - [ ] Exception messages are informative
diff --git a/.claude/commands/gen-model.md b/.claude/commands/gen-model.md
index 8763169..25a8b69 100644
--- a/.claude/commands/gen-model.md
+++ b/.claude/commands/gen-model.md
@@ -58,7 +58,7 @@ CREATE TABLE users (
 2. Show the SQL migration to create the table
 3. Remind the user to configure the backend:
    ```python
-   from rhosocial.activerecord.backend.impl.sqlite import SQLiteBackend
+   from rhosocial.activerecord.backend.impl.sqlite.backend import SQLiteBackend
    User.configure(SQLiteBackend("sqlite:///app.db"))
    ```
 
diff --git a/.claude/commands/validate-model.md b/.claude/commands/validate-model.md
index 5e95c97..e7266c8 100644
--- a/.claude/commands/validate-model.md
+++ b/.claude/commands/validate-model.md
@@ -66,7 +66,7 @@ user = User(name="John")  # Will raise "No backend configured"
 user.save()
 
 # CORRECT
-from rhosocial.activerecord.backend.impl.sqlite import SQLiteBackend
+from rhosocial.activerecord.backend.impl.sqlite.backend import SQLiteBackend
 User.configure(SQLiteBackend("sqlite:///app.db"))
 user = User(name="John")
 user.save()
diff --git a/.claude/testing.md b/.claude/testing.md
index a5830cc..ae4dd3b 100644
--- a/.claude/testing.md
+++ b/.claude/testing.md
@@ -23,8 +23,8 @@ dependencies = [
 
 ```bash
 cd /mnt/i/GitHubRepositories/rhosocial/python-activerecord-sqlserver
-source .venv/bin/activate
-export PYTHONPATH=src
+source .venv3.14-ubuntu26.04/bin/activate
+export PYTHONPATH=src:tests
 pytest tests/ -v
 ```
 
@@ -36,5 +36,5 @@ pytest tests/ -v
 
 ## Reference
 
-- [Core testing guide](../python-activerecord/.claude/testing.md)
-- [SQL Server backend development](../python-activerecord/.claude/backend_development.md)
\ No newline at end of file
+- [Core testing guide](../../python-activerecord/.claude/testing.md)
+- [SQL Server backend development](../../../python-activerecord/.claude/backend_development.md)
\ No newline at end of file
diff --git a/.github/workflows/changelog-check.yml b/.github/workflows/changelog-check.yml
index de1c276..abc4ec9 100644
--- a/.github/workflows/changelog-check.yml
+++ b/.github/workflows/changelog-check.yml
@@ -1,8 +1,32 @@
+# .github/workflows/changelog-check.yml
+#
+# Enforces the rhosocial changelog fragment rules.
+#
+#   feature/* or fix/*  ->  release/* | maint/*|  main
+#     - a feature/fix branch must not target main directly
+#     - the PR must add at least one changelog.d/<number>.<type>.md fragment
+#     - every added fragment's <number> must equal the PR number
+#     - fragments already present in changelog.d/ from previously merged
+#       branches are ignored; only files ADDED by this PR are considered
+#
+#   release/*  ->  main
+#     - CHANGELOG.md must have changed (content is not inspected)
+#     - changelog.d/ must contain no fragments at the merge commit
+#
+# Escape hatches (all three retained): a [trivial] marker in the PR title,
+# the skip-changelog label, or a "docs: update CHANGELOG" title. An escape
+# hatch waives the "at least one fragment" requirement only -- the
+# number-must-match-PR rule is always enforced on fragments that were added.
 name: Changelog Fragment Check
 
 on:
   pull_request:
-    branches: 
+    branches:
+      - main
+      - 'release/v**'
+      - 'maint/**'
+  push:
+    branches:
       - main
       - 'release/v**'
       - 'maint/**'
@@ -17,72 +41,201 @@ jobs:
     steps:
       - uses: actions/checkout@v6
         with:
-          fetch-depth: 0 # Ensure full history is fetched
+          fetch-depth: 0
 
-      - name: Check for changelog fragment
+      - name: Validate changelog fragments
         env:
-          PR_TITLE: ${{ github.event.pull_request.title }}
-          HEAD_REF: ${{ github.head_ref }}
+          EVENT_NAME: ${{ github.event_name }}
+          HEAD_REF: ${{ github.head_ref || '' }}
+          BASE_REF: ${{ github.base_ref || '' }}
+          PR_NUMBER: ${{ github.event.pull_request.number || '' }}
+          PR_TITLE: ${{ github.event.pull_request.title || '' }}
+          PR_LABELS: ${{ join(github.event.pull_request.labels.*.name, ',') }}
         run: |
-          # Fetch the base branch explicitly to ensure it's available for comparison
-          git fetch origin ${{ github.base_ref }}
-
-          # --- EXEMPTION FOR RELEASE BRANCH MERGES ---
-          # Release branches already contain changelog fragments from development
-          # Skip fragment check for PRs from release/* branches to main
-          if [[ "$HEAD_REF" =~ ^release/ ]]; then
-            echo "✓ Release branch PR, fragment check skipped (fragments already in branch history)"
+          set -uo pipefail
+
+          # Towncrier fragment types. Advisory only: a project may legitimately
+          # configure a different set in pyproject.toml [tool.towncrier.type].
+          KNOWN_TYPES="added changed deprecated removed fixed performance security docs internal"
+
+          # Files that live in changelog.d/ but are not fragments.
+          is_boilerplate() {
+            case "${1##*/}" in
+              README.md|template.md|.gitkeep) return 0 ;;
+              *) return 1 ;;
+            esac
+          }
+
+          # Validate <path> against <expected_number> (empty = don't care).
+          # Prints the fragment type on success.
+          validate_fragment() {
+            local path="$1" expected="$2"
+            local base num type
+
+            base="${path##*/}"
+
+            if [[ ! "$base" =~ ^([0-9]+)\.([a-zA-Z]+)\.md$ ]]; then
+              echo "::error file=$path::fragment must be named <number>.<type>.md, got '$base'"
+              return 1
+            fi
+            num="${BASH_REMATCH[1]}"
+            type="${BASH_REMATCH[2]}"
+
+            if [[ -n "$expected" && "$num" != "$expected" ]]; then
+              echo "::error file=$path::fragment number '$num' does not match PR #$expected"
+              echo "   Rename it to changelog.d/$expected.$type.md, or open a PR for #$num."
+              return 1
+            fi
+
+            if [[ " $KNOWN_TYPES " != *" $type "* ]]; then
+              echo "::warning file=$path::'$type' is not a standard towncrier type" >&2
+            fi
+
+            echo "$type"
+            return 0
+          }
+
+          is_exempt() {
+            [[ "$PR_TITLE" == *"[trivial]"* ]] && return 0
+            [[ ",$PR_LABELS," == *",skip-changelog,"* ]] && return 0
+            [[ "$PR_TITLE" == "docs: update CHANGELOG"* ]] && return 0
+            return 1
+          }
+
+          # ------------------------------------------------------------------
+          # release/* -> main : CHANGELOG must change, changelog.d/ must be empty
+          # ------------------------------------------------------------------
+          check_release_merge() {
+            local scope="$1" changed remaining failed=0
+
+            changed=$(git diff --name-only "origin/main...HEAD" -- CHANGELOG.md)
+            if [[ -z "$changed" ]]; then
+              echo "::error::CHANGELOG.md was not updated by this $scope."
+              echo "   A release merge must regenerate the changelog (e.g. \`towncrier build --yes --keep\`)"
+              echo "   before the fragments under changelog.d/ are discarded."
+              failed=1
+            else
+              echo "OK: CHANGELOG.md updated"
+            fi
+
+            # Checked against the merge result, not the diff: leftover fragments
+            # from earlier in the release cycle must be gone by this point.
+            remaining=$(git ls-tree --name-only HEAD changelog.d/ \
+                        | while read -r f; do
+                            if ! is_boilerplate "$f" \
+                               && [[ "${f##*/}" =~ ^[0-9]+\.[a-zA-Z]+\.md$ ]]; then
+                              echo "$f"
+                            fi
+                          done)
+            if [[ -n "$remaining" ]]; then
+              echo "::error::changelog.d/ still contains fragments after the release merge:"
+              echo "$remaining" | while read -r f; do echo "   - $f"; done
+              echo "   Delete them; their content is already folded into CHANGELOG.md."
+              failed=1
+            else
+              echo "OK: changelog.d/ is clear of fragments"
+            fi
+
+            return $failed
+          }
+
+          # ------------------------------------------------------------------
+          # push event: no PR number available, so only structural checks
+          # ------------------------------------------------------------------
+          if [[ "$EVENT_NAME" == "push" ]]; then
+            if [[ "$GITHUB_REF_NAME" == "main" ]]; then
+              touched=$(git diff-tree --no-commit-id --name-only -r HEAD)
+              if ! echo "$touched" | grep -qE '^(CHANGELOG\.md|changelog\.d/|src/)'; then
+                echo "OK: no changelog-relevant changes in this push"
+                exit 0
+              fi
+              check_release_merge "push to main" || exit 1
+              exit $?
+            fi
+            echo "OK: push to $GITHUB_REF_NAME (fragment numbering is validated on the PR)"
             exit 0
           fi
-          # --- END RELEASE BRANCH EXEMPTION ---
-
-          # Compare the head of the PR (current HEAD) with the base branch's remote tracking ref
-          # This compares the changes introduced by the PR branch relative to its base.
-          # Use --diff-filter=A to only consider added files for fragment check
-          CHANGED_FILES=$(git diff --name-only --diff-filter=A origin/${{ github.base_ref }}...HEAD)
-
-          # Debugging: Print the diff command and its output
-          echo "Executing: git diff --name-only --diff-filter=A origin/${{ github.base_ref }}...HEAD"
-          echo "Changed files (added only): $CHANGED_FILES"
-
-          # --- EXEMPTION FOR CHANGELOG BUILD PRS ---
-          # Check if PR title indicates a changelog update (e.g., "docs: update CHANGELOG")
-          # This exempts PRs that are specifically for building the changelog (which remove fragments)
-          if [[ "$PR_TITLE" =~ ^docs:\ update\ CHANGELOG ]]; then
-            echo "✓ PR title indicates changelog update, fragment check skipped"
+
+          # ------------------------------------------------------------------
+          # pull_request
+          # ------------------------------------------------------------------
+          echo "head=$HEAD_REF base=$BASE_REF pr=#$PR_NUMBER"
+
+          if [[ "$HEAD_REF" == release/* && "$BASE_REF" == "main" ]]; then
+            git fetch origin main --quiet
+            echo "== release merge into main =="
+            check_release_merge "release merge" || exit 1
             exit 0
           fi
-          # --- END EXEMPTION ---
-          
-          # Check if any changelog fragment was added
-          if echo "$CHANGED_FILES" | grep -q "^changelog.d/[0-9].*\.md$"; then
-            echo "✓ Changelog fragment found"
-            exit 0
+
+          # A feature/fix branch never merges straight into main; it targets a
+          # release or maintenance branch. Opening a second PR at main from the
+          # same branch is a duplicate, and it also invalidates the fragment
+          # numbering, which is bound to a single PR number.
+          if [[ ("$HEAD_REF" == feature/* || "$HEAD_REF" == fix/* || "$HEAD_REF" == bugfix/* \
+                || "$HEAD_REF" == test/* || "$HEAD_REF" == docs/* || "$HEAD_REF" == chore/*) \
+                && "$BASE_REF" == "main" ]]; then
+            echo "::error::'$HEAD_REF' must not target \`main\` directly."
+            echo ""
+            echo "Per the rhosocial merge rules:"
+            echo "  feature/* fix/* bugfix/* test/* docs/* chore/*  ->  release/* | maint/*"
+            echo "  release/*                                            ->  main"
+            echo ""
+            echo "Retarget this PR at the active release branch, or close it if"
+            echo "another PR from '$HEAD_REF' already targets the release branch."
+            echo "The changelog fragment is numbered for one PR only, so a duplicate"
+            echo "PR at main would also fail the fragment numbering check."
+            echo ""
+            git branch -r --list "origin/release/*" | sed 's#.*origin/##' | sed 's/^/    /'
+            exit 1
           fi
-          
-          # Check if this is an internal change (exempt from fragment requirement)
-          if echo "$CHANGED_FILES" | grep -qE "^(tests/|docs/|\.github/)"; then
-            echo "✓ Internal change, fragment not required"
-            exit 0
+
+          git fetch origin "$BASE_REF" --quiet
+
+          # Fragments ADDED by this PR. Fragments that were already in
+          # changelog.d/ (carried in by previously merged branches) are not in
+          # this list and are therefore ignored.
+          added=$(git diff --name-only --diff-filter=A "origin/$BASE_REF...HEAD" -- 'changelog.d/*.md')
+
+          failed=0
+          types=""
+          if [[ -n "$added" ]]; then
+            while read -r f; do
+              [[ -z "$f" ]] && continue
+              is_boilerplate "$f" && continue
+              t=$(validate_fragment "$f" "$PR_NUMBER") || failed=1
+              [[ -n "$t" ]] && types="$types $t"
+            done <<< "$added"
           fi
-          
-          # Check if PR is marked as trivial
-          if [[ "$PR_TITLE" =~ \[trivial\] ]]; then
-            echo "✓ PR marked as trivial, fragment not required"
-            exit 0
+
+          # The number-must-match rule is enforced even for exempt PRs; only
+          # the presence requirement is waived.
+          if [[ "$failed" -ne 0 ]]; then
+            echo ""
+            echo "✗ Fragment numbering does not match PR #$PR_NUMBER"
+            exit 1
           fi
-          
-          echo "✗ Missing changelog fragment"
-          echo "Please add a changelog fragment in changelog.d/"
-          echo "Example: changelog.d/${{ github.event.number }}.fixed.md"
-          echo ""
-          echo "Fragment types:"
-          echo "  - added.md      - New features"
-          echo "  - fixed.md      - Bug fixes"
-          echo "  - changed.md    - Behavior changes"
-          echo "  - deprecated.md - Deprecations"
-          echo "  - removed.md    - Removed features"
-          echo "  - security.md   - Security fixes"
-          echo ""
-          echo "If this PR does not need a changelog entry, add [trivial] to the title."
-          exit 1
\ No newline at end of file
+
+          if [[ -z "$added" ]]; then
+            if is_exempt; then
+              echo "OK: no fragment required (exempt)"
+              exit 0
+            fi
+            if git diff --name-only "origin/$BASE_REF...HEAD" \
+                 | grep -qE '^(tests/|docs/|\.github/)' \
+               && ! git diff --name-only "origin/$BASE_REF...HEAD" | grep -qE '^src/'; then
+              echo "OK: internal-only change, no fragment required"
+              exit 0
+            fi
+            echo "::error::No changelog fragment added by this PR."
+            echo "   Add at least one changelog.d/$PR_NUMBER.<type>.md"
+            echo ""
+            echo "Types: added | changed | deprecated | removed | fixed |"
+            echo "       performance | security | docs | internal"
+            echo ""
+            echo "Or waive it: add [trivial] to the PR title, apply the"
+            echo "skip-changelog label, or title the PR 'docs: update CHANGELOG'."
+            exit 1
+          fi
+
+          echo "OK: fragment(s) added for PR #$PR_NUMBER ->$types"
diff --git a/README.md b/README.md
index 68cd8dc..e485fa5 100644
--- a/README.md
+++ b/README.md
@@ -5,229 +5,211 @@
 [![Tests](https://github.com/rhosocial/python-activerecord-sqlserver/actions/workflows/test.yml/badge.svg)](https://github.com/rhosocial/python-activerecord-sqlserver/actions)
 [![Coverage Status](https://codecov.io/gh/rhosocial/python-activerecord-sqlserver/branch/main/graph/badge.svg)](https://app.codecov.io/gh/rhosocial/python-activerecord-sqlserver/tree/main)
 [![Apache 2.0 License](https://img.shields.io/github/license/rhosocial/python-activerecord-sqlserver.svg)](https://github.com/rhosocial/python-activerecord-sqlserver/blob/main/LICENSE)
-[![Powered by vistart](https://img.shields.io/badge/Powered_by-vistart-blue.svg)](https://github.com/vistart)
 
 <div align="center">
     <img src="https://raw.githubusercontent.com/rhosocial/python-activerecord/main/docs/images/logo.svg" alt="rhosocial ActiveRecord Logo" width="200"/>
     <h3>SQL Server Backend for rhosocial-activerecord</h3>
-    <p><b>T-SQL Support · Enterprise Features · Sync & Async</b></p>
+    <p><b>OUTPUT clause · Temporal tables · SQL Graph · Sync &amp; async</b></p>
 </div>
 
-> **Note**: This is a backend implementation for [rhosocial-activerecord](https://github.com/rhosocial/python-activerecord). It cannot be used standalone.
+This is a backend implementation for [rhosocial-activerecord](https://github.com/rhosocial/python-activerecord).
+It cannot be used standalone.
 
-## Why This Backend?
-
-### 1. SQL Server-Specific Optimizations
-
-| Feature | This Backend | Generic Solutions |
-|---------|-------------|-------------------|
-| **RETURNING/OUTPUT** | Native `OUTPUT` clause | Manual SELECT-after-write |
-| **Temporal Tables** | `FOR SYSTEM_TIME` | Application-level audit logs |
-| **Partitioning** | `PARTITION` schemes/functions | Manual sharding |
-| **Sequences** | Native `CREATE SEQUENCE` | Identity/application counters |
-
-### 2. True Sync-Async Parity
-
-Same API surface for both sync and async operations:
-
-```python
-# Sync
-users = User.query().where(User.c.age >= 18).all()
-
-# Async - just add await
-users = await User.query().where(User.c.age >= 18).all()
-```
+## Requirements
 
-### 3. Built for Production
+<!-- Generated by tools/gen_backend_matrix.py; do not edit by hand. -->
 
-- **Connection pooling** with configurable pool sizes
-- **Transaction support** with proper isolation levels
-- **Error mapping** from SQL Server error codes to Python exceptions
-- **Type adapters** for SQL Server-specific data types
+_b69f713_
 
-## Quick Start
+- **Python**: `>=3.9`
+- **Core**: `rhosocial-activerecord>=1.0.0.dev0,<2.0.0`
+- **Driver**: `pyodbc>=5.3.0` (with an installed ODBC Driver 17+)
+- **CI-tested server versions**: 2017, 2019, 2022, 2025
+- **Published**: PyPI `1.0.0.dev2`
 
-### Installation
+## Installation
 
 ```bash
 pip install rhosocial-activerecord-sqlserver
 ```
 
-### Basic Usage
+## Quick Start
 
 ```python
-from rhosocial.activerecord.model import ActiveRecord
-from rhosocial.activerecord.backend.impl.sqlserver import SQLServerBackend
+from typing import ClassVar, Optional
+
+from rhosocial.activerecord.base import FieldProxy
+from rhosocial.activerecord.backend.impl.sqlserver.backend import SQLServerBackend
 from rhosocial.activerecord.backend.impl.sqlserver.config import SQLServerConnectionConfig
-from typing import Optional
+from rhosocial.activerecord.backend.expression import CreateTableExpression
+from rhosocial.activerecord.backend.expression.statements import (
+    ColumnConstraint,
+    ColumnConstraintType,
+    ColumnDefinition,
+)
+from rhosocial.activerecord.backend.expression.types import IntegerType, VarCharType
+from rhosocial.activerecord.model import ActiveRecord
+
 
 class User(ActiveRecord):
     __table_name__ = "users"
+
     id: Optional[int] = None
     name: str
     email: str
 
-# Configure
-config = SQLServerConnectionConfig(
-    host="localhost",
-    port=1433,
-    database="myapp",
-    username="sa",
-    password="YourStrong!Passw0rd"
+    c: ClassVar[FieldProxy] = FieldProxy()
+
+
+User.configure(
+    SQLServerConnectionConfig(
+        host="localhost",
+        port=1433,
+        database="myapp",
+        username="sa",
+        password="YourStrong!Passw0rd",
+        driver="{ODBC Driver 17 for SQL Server}",
+    ),
+    SQLServerBackend,
 )
-User.configure(config, SQLServerBackend)
 
-# Use
+dialect = User.__backend__.dialect
+User.__backend__.execute(*CreateTableExpression(
+    dialect,
+    "users",
+    columns=[
+        ColumnDefinition(
+            dialect, "id", IntegerType(dialect),
+            constraints=[ColumnConstraint(dialect, ColumnConstraintType.PRIMARY_KEY,
+                is_auto_increment=True)],
+        ),
+        ColumnDefinition(dialect, "name", VarCharType(dialect, 100)),
+        ColumnDefinition(dialect, "email", VarCharType(dialect, 255)),
+    ],
+).to_sql())
+
 user = User(name="Alice", email="alice@example.com")
 user.save()
-
-# Query with parameter binding
-results = User.query().where("email = ?", ("alice@example.com",)).all()
+rows = User.query().where(User.c.email == "alice@example.com").all()
 ```
 
-> 💡 **AI Prompt**: "How do I configure connection pooling for SQL Server?"
-
-## SQL Server-Specific Features
-
-### OUTPUT / RETURNING
+### Async
 
-Retrieve inserted or updated rows with the `OUTPUT` clause:
+`AsyncSQLServerBackend` exposes the same API. Method names are identical; add
+`await`.
 
 ```python
-# INSERT with OUTPUT
-user = User(name="Alice", email="alice@example.com")
-user.save()
-print(user.id)  # Populated automatically via OUTPUT
-```
+from rhosocial.activerecord.backend.impl.sqlserver.backend import AsyncSQLServerBackend
+from rhosocial.activerecord.model import AsyncActiveRecord
 
-### Temporal Tables
 
-Query historical state with `FOR SYSTEM_TIME`:
+class User(AsyncActiveRecord):
+    ...
 
-```python
-# As of a specific time
-User.query().where(
-    "user_id = ? FOR SYSTEM_TIME AS OF ?",
-    (1, "2026-06-30T12:00:00"),
-).all()
+
+User.configure(config, AsyncSQLServerBackend)
+rows = await User.query().where(User.c.email == "alice@example.com").all()
 ```
 
-### Partitioned Tables
+## SQL Server-Specific Features
 
-SQL Server partition schemes and functions:
+### `OUTPUT` instead of `RETURNING`
 
-```python
-# Partitioned table DDL support
-class Orders(ActiveRecord):
-    __table_name__ = "orders"
-    __partition__ = {
-        "column": "order_date",
-        "scheme": "ps_order_date",
-    }
-    order_id: int
-    order_date: datetime
-```
+SQL Server has no `RETURNING`; the equivalent is the `OUTPUT` clause, which
+the backend emits for DML that needs to return the affected row.
 
-### Sequences
+### Temporal tables
 
-Native sequence support:
+Query historical state with `FOR SYSTEM_TIME`. The table must already be
+declared as a system-versioned temporal table; the backend does not add the
+`PERIOD FOR` clause for you.
 
 ```python
-# Use a sequence-backed column
-class Ticket(ActiveRecord):
-    __table_name__ = "tickets"
-    ticket_no: int  # NEXT VALUE FOR ticket_seq
+User.query().where(
+    "id = ? FOR SYSTEM_TIME AS OF ?",
+    (1, "2026-06-30T12:00:00"),
+).all()
 ```
 
-## Requirements
+### Memory-optimized and columnstore tables
 
-- **Python**: 3.9+ (including 3.13t/3.14t free-threaded builds)
-- **Core**: `rhosocial-activerecord>=1.0.0`
-- **Driver**: `pyodbc>=5.0.0` (with ODBC Driver 17+ for SQL Server)
+Set through the DDL expression's table options, not a model attribute:
 
-## SQL Server Version Compatibility
+```python
+from rhosocial.activerecord.backend.impl.sqlserver.expression import (
+    SQLServerCreateTableOptions,
+)
 
-| Feature | Min Version | Notes |
-|---------|-------------|-------|
-| Basic operations | 2017+ | Core functionality |
-| Temporal tables | 2016+ | `FOR SYSTEM_TIME` |
-| Sequences | 2012+ | `CREATE SEQUENCE` |
-| Partitioning | 2008+ | Partition functions/schemes |
-| Columnstore indexes | 2014+ | Analytics acceleration |
-| Memory-optimized tables | 2014+ | In-memory OLTP |
-| PIVOT/UNPIVOT | 2005+ | Row-to-column transforms |
-| OUTPUT clause | 2005+ | RETURNING equivalent |
-| JSON functions | 2016+ | `JSON_VALUE`, `JSON_QUERY` |
-| STRING_AGG | 2017+ | String aggregation |
-| UTF-8 collation | 2019+ | `_UTF8` collations |
+CreateTableExpression(
+    dialect,
+    "sessions",
+    columns=[...],
+    table_options=SQLServerCreateTableOptions(dialect, memory_optimized=True),
+)
+```
 
-**Recommended**: SQL Server 2019+ for optimal feature support.
+## Version Gates
+
+Gates below are the versions at which this backend's own `supports_*`
+switch returns `True`, probed at 10, 11, 12, 13, 14, 15, 16.
+A version is the first probe at or above the real gate, so each is an
+upper bound within one ladder step. Switches already `True` at the
+oldest release carry no gate and are omitted.
+
+| Min version | Capabilities that turn on |
+|---|---|
+| 11 (2012) | `create_sequence`, `drop_sequence`, `nonclustered_columnstore`, `offset_fetch`, `order_by_in_subquery`, `try_cast`, `try_convert`, `window_frame_clause` |
+| 12 (2014) | `clustered_columnstore`, `memory_optimized_table_types`, `memory_optimized_tables` |
+| 13 (2016) | `drop_type_if_exists`, `if_exists_table`, `if_exists_view`, `index_if_exists`, `json_table`, `json_type`, `system_versioning`, `temporal_tables` |
+| 14 (2017) | `graph_pseudo_columns`, `graph_table_kind`, `sql_graph` |
+| 15 (2019) | `edge_constraints`, `for_update_skip_locked`, `graph_path_aggregates`, `readpast`, `shortest_path` |
+| 16 (2022) | `columnstore_order` |
+
+## Known Limitations
+
+- **No connection pooling.** `pool_size` and `pool_timeout` are accepted by
+  the config class but not consumed; `connect()` opens one persistent
+  connection.
+- **No native arrays, and no JSON *type*.** JSON is reachable through
+  functions (`JSON_VALUE`, `JSON_QUERY`) on 2016+, not through a column
+  type, and `supports_json_type` gates on that.
+- **Table partitioning is not implemented.** `add_partition`,
+  `attach_partition`, `detach_partition`, `list_table_partitioning`,
+  `range_table_partitioning`, `hash_table_partitioning` and
+  `subpartitioning` are all `False` at every probed version. A model does
+  not take a `__partition__` attribute.
+- Also unsupported: `alter_type`, `constraint_enforced`, `create_or_replace_view`,
+  `deferrable_*`, `fetch_with_ties`, `fk_match`, `returning_alias`,
+  `returning_wildcard`, `set_type`, `transaction_mode`.
 
-## Get Started with AI Code Agents
+## Testing
 
-This project supports AI-assisted development. Clone and open in your preferred tool:
+Tests require a reachable SQL Server instance and must run serially.
 
 ```bash
-git clone https://github.com/rhosocial/python-activerecord-sqlserver.git
-cd python-activerecord-sqlserver
+export PYTHONPATH=src:tests
+.venv3.14-ubuntu26.04/bin/pytest tests/
 ```
 
-### Example AI Prompts
-
-- "How do I configure connection pooling for SQL Server?"
-- "Show me how to use temporal tables"
-- "How do I use the OUTPUT clause with INSERT?"
-- "Create a model with a partitioned table"
-
-### For Any LLM
-
-Feed the documentation files in `docs/` to your preferred LLM for context-aware assistance.
-
-## Testing
-
-> ⚠️ **CRITICAL**: Tests MUST run serially. Do NOT use `pytest -n auto` or parallel execution.
+The shared contract suite lives in
+[python-activerecord-testsuite](https://github.com/rhosocial/python-activerecord-testsuite):
 
 ```bash
-# Run all tests
-PYTHONPATH=src pytest tests/
-
-# Run specific feature tests
-PYTHONPATH=src pytest tests/rhosocial/activerecord_sqlserver_test/feature/basic/
-PYTHONPATH=src pytest tests/rhosocial/activerecord_sqlserver_test/feature/query/
+PYTHONPATH=tests .venv3.14-ubuntu26.04/bin/pytest \
+  ../python-activerecord-testsuite/src/rhosocial/activerecord/testsuite/feature/
 ```
 
-See the [Testing Documentation](https://github.com/rhosocial/python-activerecord/blob/main/.claude/testing.md) for details.
-
 ## Documentation
 
-- **[Getting Started](docs/en_US/getting_started/)** — Installation and configuration
-- **[SQL Server Features](docs/en_US/sqlserver_specific_features/)** — SQL Server-specific capabilities
-- **[Type Adapters](docs/en_US/type_adapters/)** — Data type handling
-- **[Transaction Support](docs/en_US/transaction_support/)** — Transaction management
-
-## Comparison with Other Backends
-
-| Feature | SQL Server | PostgreSQL | SQLite |
-|---------|-----------|------------|--------|
-| **RETURNING** | ✅ OUTPUT | ✅ RETURNING | ✅ RETURNING |
-| **Temporal Tables** | ✅ | ❌ | ❌ |
-| **Sequences** | ✅ Native | ✅ Native | ⚠️ Emulated |
-| **Arrays** | ❌ | ✅ Native | ❌ |
-| **JSON Type** | ⚠️ Functions only | ✅ JSONB | ⚠️ JSON1 extension |
-
-> 💡 **AI Prompt**: "When should I choose SQL Server over PostgreSQL for my project?"
+This repository has no `docs/` tree. Backend notes live in
+[.claude/architecture.md](.claude/architecture.md) and
+[.claude/testing.md](.claude/testing.md); core library documentation is at
+[python-activerecord/docs](https://github.com/rhosocial/python-activerecord/tree/main/docs).
 
 ## Contributing
 
-We welcome contributions! See [CONTRIBUTING.md](CONTRIBUTING.md) for guidelines.
+See [CONTRIBUTING.md](https://github.com/rhosocial/python-activerecord/blob/main/CONTRIBUTING.md).
 
 ## License
 
 [Apache License 2.0](LICENSE) — Copyright © 2026 [vistart](https://github.com/vistart)
-
----
-
-<div align="center">
-    <p><b>Built with ❤️ by the rhosocial team</b></p>
-    <p><a href="https://github.com/rhosocial/python-activerecord-sqlserver">GitHub</a> · <a href="https://docs.python-activerecord.dev.rho.social/backends/sqlserver.html">Documentation</a> · <a href="https://pypi.org/project/rhosocial-activerecord-sqlserver/">PyPI</a></p>
-</div>
\ No newline at end of file
diff --git a/changelog.d/6.added.md b/changelog.d/6.added.md
new file mode 100644
index 0000000..b8c99ae
--- /dev/null
+++ b/changelog.d/6.added.md
@@ -0,0 +1 @@
+Add client-certificate (mutual TLS) support to the ODBC connection string. `SQLServerConnectionConfig` could only express server-side encryption via `encrypt` and `trust_server_certificate`; there was no way to present a client certificate. The new `client_certificate`, `client_key`, `client_key_password` and `host_name_in_certificate` fields are emitted as the `ClientCertificate`, `ClientKey`, `ClientKeyPassword` and `HostNameInCertificate` ODBC keywords by `build_connection_string()`, and are accepted as backend kwargs. `validate_config()` now rejects a `client_key` supplied without a `client_certificate`, so the mismatch surfaces as a clear error instead of an opaque driver failure.
diff --git a/src/rhosocial/activerecord/backend/impl/sqlserver/__init__.py b/src/rhosocial/activerecord/backend/impl/sqlserver/__init__.py
deleted file mode 100644
index bf75230..0000000
--- a/src/rhosocial/activerecord/backend/impl/sqlserver/__init__.py
+++ /dev/null
@@ -1,157 +0,0 @@
-# src/rhosocial/activerecord/backend/impl/sqlserver/__init__.py
-"""SQL Server backend implementation for the Python ORM."""
-
-from .backend import SQLServerBackend
-from .config import SQLServerConnectionConfig
-from .collation import SQLServerCollation
-from .dialect import SQLServerDialect
-from .options import SQLServerExecutionOptions
-from .transaction import SQLServerTransactionManager
-from .adapters import (
-    SQLServerUUIDAdapter,
-    SQLServerDateTimeAdapter,
-    SQLServerDateTimeOffsetAdapter,
-    SQLServerDateAdapter,
-    SQLServerTimeAdapter,
-    SQLServerJSONAdapter,
-    SQLServerXMLAdapter,
-    SQLServerSpatialAdapter,
-    SQLServerHierarchyIdAdapter,
-)
-
-from .explain import SQLServerExplainResult, SQLServerExplainRow
-
-from .expression import (
-    SQLServerOutputInsertedExpression,
-    SQLServerOutputDeletedExpression,
-    SQLServerTableHintClause,
-    SQLServerTableHint,
-    SQLServerReadPastHint,
-    SQLServerTemporalPeriodDefinition,
-    SQLServerSystemVersioningClause,
-    SQLServerOpenJsonExpression,
-    OpenJsonColumn,
-    SQLServerNextValueForExpression,
-    SQLServerTryCastExpression,
-    SQLServerTryConvertExpression,
-    SQLServerContainsPredicate,
-    SQLServerFreetextPredicate,
-    SQLServerTypeNullability,
-    SQLServerAliasTypeDefinition,
-    SQLServerTableTypeDefinition,
-    SQLServerClrTypeDefinition,
-    SQLServerDropTypeExpression,
-    SQLServerRenameTypeExpression,
-)
-
-from .expression.types import (
-    SQLServerNVarCharType,
-    SQLServerNCharType,
-    SQLServerNVarCharMaxType,
-    SQLServerVarBinaryType,
-    SQLServerVarBinaryMaxType,
-    SQLServerXmlType,
-    SQLServerTinyIntType,
-    SQLServerBitType,
-    SQLServerImageType,
-)
-
-from .mixins import (
-    SQLServerBackendMixin,
-    SQLServerConcurrencyMixin,
-    SQLServerTypeSupportMixin,
-    SQLServerTypeDDLMixin,
-)
-from .protocols import SQLServerUserDefinedTypeSupport
-
-from .schema import SQLServerSchemaDiffer
-
-from .type_compatibility import (
-    DIRECT_COMPATIBLE_CASTS,
-    check_cast_compatibility,
-    get_compatible_types,
-)
-
-__all__ = [
-    "SQLServerBackend",
-    "SQLServerConnectionConfig",
-    "SQLServerExecutionOptions",
-    "SQLServerDialect",
-    "SQLServerCollation",
-    "SQLServerTransactionManager",
-    "SQLServerUUIDAdapter",
-    "SQLServerDateTimeAdapter",
-    "SQLServerDateTimeOffsetAdapter",
-    "SQLServerDateAdapter",
-    "SQLServerTimeAdapter",
-    "SQLServerJSONAdapter",
-    "SQLServerXMLAdapter",
-    "SQLServerSpatialAdapter",
-    "SQLServerHierarchyIdAdapter",
-    "SQLServerExplainResult",
-    "SQLServerExplainRow",
-    "SQLServerOutputInsertedExpression",
-    "SQLServerOutputDeletedExpression",
-    "SQLServerTableHintClause",
-    "SQLServerTableHint",
-    "SQLServerReadPastHint",
-    "SQLServerTemporalPeriodDefinition",
-    "SQLServerSystemVersioningClause",
-    "SQLServerOpenJsonExpression",
-    "OpenJsonColumn",
-    "SQLServerNextValueForExpression",
-    "SQLServerTryCastExpression",
-    "SQLServerTryConvertExpression",
-    "SQLServerContainsPredicate",
-    "SQLServerFreetextPredicate",
-    "SQLServerTypeNullability",
-    "SQLServerAliasTypeDefinition",
-    "SQLServerTableTypeDefinition",
-    "SQLServerClrTypeDefinition",
-    "SQLServerDropTypeExpression",
-    "SQLServerRenameTypeExpression",
-    # DDL DataType subclasses
-    "SQLServerNVarCharType",
-    "SQLServerNCharType",
-    "SQLServerNVarCharMaxType",
-    "SQLServerVarBinaryType",
-    "SQLServerVarBinaryMaxType",
-    "SQLServerXmlType",
-    "SQLServerTinyIntType",
-    "SQLServerBitType",
-    "SQLServerImageType",
-    # Mixins
-    "SQLServerBackendMixin",
-    "SQLServerConcurrencyMixin",
-    "SQLServerTypeSupportMixin",
-    "SQLServerTypeDDLMixin",
-    "SQLServerUserDefinedTypeSupport",
-    # Schema differ
-    "SQLServerSchemaDiffer",
-    # Type compatibility
-    "DIRECT_COMPATIBLE_CASTS",
-    "check_cast_compatibility",
-    "get_compatible_types",
-]
-
-
-def __getattr__(name: str):
-    _lazy_imports = {
-        "AsyncSQLServerBackend": (".async_backend", "AsyncSQLServerBackend"),
-        "AsyncSQLServerTransactionManager": (".async_transaction", "AsyncSQLServerTransactionManager"),
-    }
-
-    if name in _lazy_imports:
-        module_path, class_name = _lazy_imports[name]
-        try:
-            import importlib
-            module = importlib.import_module(module_path, __name__)
-            return getattr(module, class_name)
-        except ImportError as e:
-            raise ImportError(
-                f"{name} requires 'aioodbc' package. "
-                f"Install it with: pip install rhosocial-activerecord-sqlserver[async] "
-                f"or pip install aioodbc"
-            ) from e
-
-    raise AttributeError(f"module {__name__!r} has no attribute {name!r}")
\ No newline at end of file
diff --git a/src/rhosocial/activerecord/backend/impl/sqlserver/backend/__init__.py b/src/rhosocial/activerecord/backend/impl/sqlserver/backend/__init__.py
new file mode 100644
index 0000000..2a7ea56
--- /dev/null
+++ b/src/rhosocial/activerecord/backend/impl/sqlserver/backend/__init__.py
@@ -0,0 +1,34 @@
+# src/rhosocial/activerecord/backend/impl/sqlserver/backend/__init__.py
+"""Sqlserver backend implementations.
+
+Every backend keeps both classes in this package: the sync class in
+``backend.py`` and the async class in ``async_backend.py``. The async class is
+re-exported here too, but resolved on first access, because it needs the
+``aioodbc`` package that the ``rhosocial-activerecord-sqlserver[async]`` extra installs.
+"""
+
+from .backend import SQLServerBackend
+
+__all__ = [
+    "SQLServerBackend",
+    "AsyncSQLServerBackend",
+]
+
+
+def __getattr__(name: str):
+    """Resolve the async class on first access.
+
+    Raises:
+        ImportError: if aioodbc is missing, naming the extra that provides it.
+        AttributeError: for any other name.
+    """
+    if name == "AsyncSQLServerBackend":
+        try:
+            from .async_backend import AsyncSQLServerBackend as backend
+        except ImportError as e:
+            raise ImportError(
+                "AsyncSQLServerBackend requires the 'aioodbc' package. "
+                "Install it with: pip install rhosocial-activerecord-sqlserver[async] or pip install aioodbc"
+            ) from e
+        return backend
+    raise AttributeError(f"module {__name__!r} has no attribute {name!r}")
diff --git a/src/rhosocial/activerecord/backend/impl/sqlserver/async_backend.py b/src/rhosocial/activerecord/backend/impl/sqlserver/backend/async_backend.py
similarity index 97%
rename from src/rhosocial/activerecord/backend/impl/sqlserver/async_backend.py
rename to src/rhosocial/activerecord/backend/impl/sqlserver/backend/async_backend.py
index 9843219..ed3effa 100644
--- a/src/rhosocial/activerecord/backend/impl/sqlserver/async_backend.py
+++ b/src/rhosocial/activerecord/backend/impl/sqlserver/backend/async_backend.py
@@ -1,4 +1,4 @@
-# src/rhosocial/activerecord/backend/impl/sqlserver/async_backend.py
+# src/rhosocial/activerecord/backend/impl/sqlserver/backend/async_backend.py
 """
 SQL Server asynchronous backend implementation.
 
@@ -25,11 +25,11 @@
 )
 from rhosocial.activerecord.backend.result import QueryResult
 from rhosocial.activerecord.backend.introspection.backend_mixin import IntrospectorBackendMixin
-from .config import SQLServerConnectionConfig
-from .dialect import SQLServerDialect
-from .async_transaction import AsyncSQLServerTransactionManager
+from ..config import SQLServerConnectionConfig
+from ..dialect import SQLServerDialect
+from ..async_transaction import AsyncSQLServerTransactionManager
 from .backend import SQLServerUnicodeDialect
-from .mixins import SQLServerBackendMixin
+from ..mixins import SQLServerBackendMixin
 
 try:
     import aioodbc
@@ -100,7 +100,10 @@ def __init__(self, **kwargs):
             sqlserver_params = [
                 'host', 'port', 'database', 'deployment_target', 'username', 'password',
                 'trusted_connection', 'driver', 'encrypt',
-                'trust_server_certificate', 'timeout', 'query_timeout',
+                'trust_server_certificate',
+                'client_certificate', 'client_key', 'client_key_password',
+                'host_name_in_certificate',
+                'timeout', 'query_timeout',
                 'autocommit', 'charset', 'pool_size', 'pool_timeout',
             ]
             
@@ -145,7 +148,7 @@ def dialect(self) -> SQLServerDialect:
     
     def _register_sqlserver_adapters(self) -> None:
         """Register SQL Server-specific type adapters (async mirror)."""
-        from .adapters import (
+        from ..adapters import (
             SQLServerUUIDAdapter,
             SQLServerDateTimeAdapter,
             SQLServerDateTimeOffsetAdapter,
@@ -641,6 +644,6 @@ async def _handle_auto_commit_if_needed(self) -> None:
     
     def _create_introspector(self):
         """Create a SQL Server introspector."""
-        from .introspection import AsyncSQLServerIntrospector
+        from ..introspection import AsyncSQLServerIntrospector
         from rhosocial.activerecord.backend.introspection.executor import AsyncIntrospectorExecutor
         return AsyncSQLServerIntrospector(self, AsyncIntrospectorExecutor(self))
diff --git a/src/rhosocial/activerecord/backend/impl/sqlserver/backend.py b/src/rhosocial/activerecord/backend/impl/sqlserver/backend/backend.py
similarity index 97%
rename from src/rhosocial/activerecord/backend/impl/sqlserver/backend.py
rename to src/rhosocial/activerecord/backend/impl/sqlserver/backend/backend.py
index b3cda41..0c1e3bc 100644
--- a/src/rhosocial/activerecord/backend/impl/sqlserver/backend.py
+++ b/src/rhosocial/activerecord/backend/impl/sqlserver/backend/backend.py
@@ -1,4 +1,4 @@
-# src/rhosocial/activerecord/backend/impl/sqlserver/backend.py
+# src/rhosocial/activerecord/backend/impl/sqlserver/backend/backend.py
 """
 SQL Server-specific implementation of the StorageBackend.
 
@@ -28,10 +28,10 @@
 from rhosocial.activerecord.backend.result import QueryResult
 from rhosocial.activerecord.backend.introspection.backend_mixin import IntrospectorBackendMixin
 from rhosocial.activerecord.backend.explain import SyncExplainBackendMixin
-from .config import SQLServerConnectionConfig
-from .dialect import SQLServerDialect
-from .transaction import SQLServerTransactionManager
-from .mixins import SQLServerBackendMixin, SQLServerConcurrencyMixin
+from ..config import SQLServerConnectionConfig
+from ..dialect import SQLServerDialect
+from ..transaction import SQLServerTransactionManager
+from ..mixins import SQLServerBackendMixin, SQLServerConcurrencyMixin
 
 
 class SQLServerUnicodeDialect(SQLServerDialect):
@@ -122,7 +122,10 @@ def __init__(self, **kwargs):
             sqlserver_params = [
                 'host', 'port', 'database', 'deployment_target', 'username', 'password',
                 'trusted_connection', 'driver', 'encrypt',
-                'trust_server_certificate', 'timeout', 'query_timeout',
+                'trust_server_certificate',
+                'client_certificate', 'client_key', 'client_key_password',
+                'host_name_in_certificate',
+                'timeout', 'query_timeout',
                 'autocommit', 'charset', 'pool_size', 'pool_timeout',
             ]
             
@@ -177,7 +180,7 @@ def transaction_manager(self) -> SQLServerTransactionManager:
 
     def _register_sqlserver_adapters(self) -> None:
         """Register SQL Server-specific type adapters."""
-        from .adapters import (
+        from ..adapters import (
             SQLServerUUIDAdapter,
             SQLServerDateTimeAdapter,
             SQLServerDateTimeOffsetAdapter,
@@ -650,7 +653,7 @@ def _create_introspector(self):
         Returns:
             SyncSQLServerIntrospector instance
         """
-        from .introspection import SyncSQLServerIntrospector
+        from ..introspection import SyncSQLServerIntrospector
         from rhosocial.activerecord.backend.introspection.executor import SyncIntrospectorExecutor
         return SyncSQLServerIntrospector(self, SyncIntrospectorExecutor(self))
     
@@ -665,6 +668,6 @@ def _parse_explain_result(self, raw_rows, sql, duration):
         Returns:
             SQLServerExplainResult instance
         """
-        from .explain import SQLServerExplainResult, SQLServerExplainRow
+        from ..explain import SQLServerExplainResult, SQLServerExplainRow
         rows = [SQLServerExplainRow(**r) for r in raw_rows]
         return SQLServerExplainResult(raw_rows=raw_rows, sql=sql, duration=duration, rows=rows)
diff --git a/src/rhosocial/activerecord/backend/impl/sqlserver/cli/connection.py b/src/rhosocial/activerecord/backend/impl/sqlserver/cli/connection.py
index 92d8ee0..43abbdf 100644
--- a/src/rhosocial/activerecord/backend/impl/sqlserver/cli/connection.py
+++ b/src/rhosocial/activerecord/backend/impl/sqlserver/cli/connection.py
@@ -221,7 +221,7 @@ def resolve_connection_config_from_args(args):
 
 def create_backend(args):
     """Create, connect, and introspect a SQL Server backend from parsed args."""
-    from rhosocial.activerecord.backend.impl.sqlserver import SQLServerBackend
+    from rhosocial.activerecord.backend.impl.sqlserver.backend import SQLServerBackend
 
     config = resolve_connection_config_from_args(args)
     backend = SQLServerBackend(connection_config=config)
diff --git a/src/rhosocial/activerecord/backend/impl/sqlserver/cli/info.py b/src/rhosocial/activerecord/backend/impl/sqlserver/cli/info.py
index 1869201..1fd3d4f 100644
--- a/src/rhosocial/activerecord/backend/impl/sqlserver/cli/info.py
+++ b/src/rhosocial/activerecord/backend/impl/sqlserver/cli/info.py
@@ -156,7 +156,7 @@ def handle(args):
     named_conn = getattr(args, "named_connection", None)
     if named_conn or args.database:
         try:
-            from rhosocial.activerecord.backend.impl.sqlserver import SQLServerBackend
+            from rhosocial.activerecord.backend.impl.sqlserver.backend import SQLServerBackend
 
             config = resolve_connection_config_from_args(args)
             backend = SQLServerBackend(connection_config=config)
diff --git a/src/rhosocial/activerecord/backend/impl/sqlserver/cli/introspect.py b/src/rhosocial/activerecord/backend/impl/sqlserver/cli/introspect.py
index d040b3d..06f2cd9 100644
--- a/src/rhosocial/activerecord/backend/impl/sqlserver/cli/introspect.py
+++ b/src/rhosocial/activerecord/backend/impl/sqlserver/cli/introspect.py
@@ -12,7 +12,7 @@
 from enum import Enum
 from typing import Any
 
-from rhosocial.activerecord.backend.impl.sqlserver import SQLServerBackend
+from rhosocial.activerecord.backend.impl.sqlserver.backend import SQLServerBackend
 from rhosocial.activerecord.backend.errors import ConnectionError, QueryError
 from .connection import add_connection_args, resolve_connection_config_from_args
 from .output import create_provider
@@ -138,7 +138,7 @@ def handle(args):
     config = resolve_connection_config_from_args(args)
 
     if args.is_async:
-        from rhosocial.activerecord.backend.impl.sqlserver import AsyncSQLServerBackend
+        from rhosocial.activerecord.backend.impl.sqlserver.backend.async_backend import AsyncSQLServerBackend
         backend = AsyncSQLServerBackend(connection_config=config)
         asyncio.run(_handle_introspect_async(args, backend, provider))
     else:
diff --git a/src/rhosocial/activerecord/backend/impl/sqlserver/cli/named_expression.py b/src/rhosocial/activerecord/backend/impl/sqlserver/cli/named_expression.py
index e590d38..b98877a 100644
--- a/src/rhosocial/activerecord/backend/impl/sqlserver/cli/named_expression.py
+++ b/src/rhosocial/activerecord/backend/impl/sqlserver/cli/named_expression.py
@@ -4,7 +4,7 @@
 named-expression requires connection arguments, output arguments, and --rich-ascii.
 """
 
-from rhosocial.activerecord.backend.impl.sqlserver import SQLServerBackend
+from rhosocial.activerecord.backend.impl.sqlserver.backend import SQLServerBackend
 from rhosocial.activerecord.backend.options import ExecutionOptions
 
 from .connection import create_connection_parent_parser, resolve_connection_config_from_args
@@ -67,7 +67,7 @@ def disconnect():
 
     is_async = getattr(args, "is_async", False)
     if is_async:
-        from rhosocial.activerecord.backend.impl.sqlserver import AsyncSQLServerBackend
+        from rhosocial.activerecord.backend.impl.sqlserver.backend.async_backend import AsyncSQLServerBackend
 
         async_backend = None
 
diff --git a/src/rhosocial/activerecord/backend/impl/sqlserver/cli/named_migration.py b/src/rhosocial/activerecord/backend/impl/sqlserver/cli/named_migration.py
index 2485f51..380fed8 100644
--- a/src/rhosocial/activerecord/backend/impl/sqlserver/cli/named_migration.py
+++ b/src/rhosocial/activerecord/backend/impl/sqlserver/cli/named_migration.py
@@ -3,7 +3,8 @@
 
 from __future__ import annotations
 
-from rhosocial.activerecord.backend.impl.sqlserver import SQLServerBackend, AsyncSQLServerBackend
+from rhosocial.activerecord.backend.impl.sqlserver.backend import SQLServerBackend
+from rhosocial.activerecord.backend.impl.sqlserver.backend.async_backend import AsyncSQLServerBackend
 
 from .connection import create_connection_parent_parser, resolve_connection_config_from_args
 from .output import create_provider
diff --git a/src/rhosocial/activerecord/backend/impl/sqlserver/cli/named_procedure.py b/src/rhosocial/activerecord/backend/impl/sqlserver/cli/named_procedure.py
index 4a3401b..5283ccd 100644
--- a/src/rhosocial/activerecord/backend/impl/sqlserver/cli/named_procedure.py
+++ b/src/rhosocial/activerecord/backend/impl/sqlserver/cli/named_procedure.py
@@ -4,7 +4,7 @@
 named-procedure requires connection arguments, output arguments, and --rich-ascii.
 """
 
-from rhosocial.activerecord.backend.impl.sqlserver import SQLServerBackend
+from rhosocial.activerecord.backend.impl.sqlserver.backend import SQLServerBackend
 
 from .connection import create_connection_parent_parser, resolve_connection_config_from_args
 from .output import create_provider
@@ -62,7 +62,7 @@ def disconnect():
 
     is_async = getattr(args, "is_async", False)
     if is_async:
-        from rhosocial.activerecord.backend.impl.sqlserver import AsyncSQLServerBackend
+        from rhosocial.activerecord.backend.impl.sqlserver.backend.async_backend import AsyncSQLServerBackend
         async_backend = None
 
         def backend_async_factory():
diff --git a/src/rhosocial/activerecord/backend/impl/sqlserver/cli/named_procedure_graph.py b/src/rhosocial/activerecord/backend/impl/sqlserver/cli/named_procedure_graph.py
index 6aa8c6e..c422006 100644
--- a/src/rhosocial/activerecord/backend/impl/sqlserver/cli/named_procedure_graph.py
+++ b/src/rhosocial/activerecord/backend/impl/sqlserver/cli/named_procedure_graph.py
@@ -4,7 +4,7 @@
 named-procedure-graph requires connection arguments, output arguments, and --rich-ascii.
 """
 
-from rhosocial.activerecord.backend.impl.sqlserver import SQLServerBackend
+from rhosocial.activerecord.backend.impl.sqlserver.backend import SQLServerBackend
 
 from .connection import create_connection_parent_parser, resolve_connection_config_from_args
 from .output import create_provider
@@ -45,7 +45,7 @@ def disconnect():
     is_async = getattr(args, "is_async", False)
 
     if is_async:
-        from rhosocial.activerecord.backend.impl.sqlserver import AsyncSQLServerBackend
+        from rhosocial.activerecord.backend.impl.sqlserver.backend.async_backend import AsyncSQLServerBackend
 
         async_backend = None
 
diff --git a/src/rhosocial/activerecord/backend/impl/sqlserver/cli/query.py b/src/rhosocial/activerecord/backend/impl/sqlserver/cli/query.py
index 514428b..afba301 100644
--- a/src/rhosocial/activerecord/backend/impl/sqlserver/cli/query.py
+++ b/src/rhosocial/activerecord/backend/impl/sqlserver/cli/query.py
@@ -9,7 +9,7 @@
 import logging
 import sys
 
-from rhosocial.activerecord.backend.impl.sqlserver import SQLServerBackend
+from rhosocial.activerecord.backend.impl.sqlserver.backend import SQLServerBackend
 from rhosocial.activerecord.backend.errors import ConnectionError, QueryError
 from .connection import add_connection_args, resolve_connection_config_from_args
 from .output import create_provider, RICH_AVAILABLE
@@ -148,7 +148,7 @@ def handle(args):
     kwargs = {"use_ascii": args.rich_ascii}
 
     if args.is_async:
-        from rhosocial.activerecord.backend.impl.sqlserver import AsyncSQLServerBackend
+        from rhosocial.activerecord.backend.impl.sqlserver.backend.async_backend import AsyncSQLServerBackend
         backend = AsyncSQLServerBackend(connection_config=config)
         asyncio.run(_execute_query_async(sql_source, backend, provider, **kwargs))
     else:
diff --git a/src/rhosocial/activerecord/backend/impl/sqlserver/cli/status.py b/src/rhosocial/activerecord/backend/impl/sqlserver/cli/status.py
index 66cc1ab..819553c 100644
--- a/src/rhosocial/activerecord/backend/impl/sqlserver/cli/status.py
+++ b/src/rhosocial/activerecord/backend/impl/sqlserver/cli/status.py
@@ -9,7 +9,7 @@
 from enum import Enum
 from typing import Any
 
-from rhosocial.activerecord.backend.impl.sqlserver import SQLServerBackend
+from rhosocial.activerecord.backend.impl.sqlserver.backend import SQLServerBackend
 from rhosocial.activerecord.backend.errors import ConnectionError, QueryError
 from .connection import add_connection_args, resolve_connection_config_from_args
 from .output import create_provider, RICH_AVAILABLE
@@ -82,7 +82,7 @@ def handle(args):
     config = resolve_connection_config_from_args(args)
 
     if args.is_async:
-        from rhosocial.activerecord.backend.impl.sqlserver import AsyncSQLServerBackend
+        from rhosocial.activerecord.backend.impl.sqlserver.backend.async_backend import AsyncSQLServerBackend
         backend = AsyncSQLServerBackend(connection_config=config)
         asyncio.run(_handle_status_async(args, backend, provider))
     else:
diff --git a/src/rhosocial/activerecord/backend/impl/sqlserver/config.py b/src/rhosocial/activerecord/backend/impl/sqlserver/config.py
index 895db27..5130884 100644
--- a/src/rhosocial/activerecord/backend/impl/sqlserver/config.py
+++ b/src/rhosocial/activerecord/backend/impl/sqlserver/config.py
@@ -72,6 +72,15 @@ class SQLServerConnectionConfig(ConnectionConfig):
     encrypt_connection: Optional[bool] = None
     trust_server_certificate: bool = False
 
+    # Client certificate (mutual TLS). The ODBC driver reads these straight
+    # from the filesystem, so they are PEM/PFX paths rather than material.
+    client_certificate: Optional[str] = None
+    client_key: Optional[str] = None
+    client_key_password: Optional[str] = None
+    # Overrides the name matched against the server certificate. Required when
+    # the certificate CN is not the host name being connected to.
+    host_name_in_certificate: Optional[str] = None
+
     timeout: int = 30
     query_timeout: int = 0
 
@@ -136,7 +145,16 @@ def build_connection_string(self) -> str:
         
         if self.charset and self.charset.upper() != "UTF-8":
             parts.append(f"CharacterSet={self.charset}")
-        
+
+        if self.client_certificate:
+            parts.append(f"ClientCertificate={self.client_certificate}")
+        if self.client_key:
+            parts.append(f"ClientKey={self.client_key}")
+        if self.client_key_password:
+            parts.append(f"ClientKeyPassword={self.client_key_password}")
+        if self.host_name_in_certificate:
+            parts.append(f"HostNameInCertificate={self.host_name_in_certificate}")
+
         for key, value in self.options.items():
             if value is not None:
                 parts.append(f"{key}={value}")
@@ -164,6 +182,11 @@ def validate_config(self) -> None:
                 UserWarning,
                 stacklevel=2
             )
+
+        if self.client_key and not self.client_certificate:
+            raise ValueError(
+                "client_key requires client_certificate for SQL Server connections"
+            )
     
     def __repr__(self) -> str:
         """Return safe string representation (password masked)."""
diff --git a/src/rhosocial/activerecord/backend/impl/sqlserver/examples/cli/named_procedure_demo.py b/src/rhosocial/activerecord/backend/impl/sqlserver/examples/cli/named_procedure_demo.py
index e61cb6c..5904699 100644
--- a/src/rhosocial/activerecord/backend/impl/sqlserver/examples/cli/named_procedure_demo.py
+++ b/src/rhosocial/activerecord/backend/impl/sqlserver/examples/cli/named_procedure_demo.py
@@ -162,7 +162,8 @@ def prepare_demo_schema():
     """
     code = (
         "import os;"
-        "from rhosocial.activerecord.backend.impl.sqlserver import SQLServerBackend, "
+        "from rhosocial.activerecord.backend.impl.sqlserver.backend import SQLServerBackend;"
+        "from rhosocial.activerecord.backend.impl.sqlserver.config import "
         "SQLServerConnectionConfig;"
         "from rhosocial.activerecord.backend.impl.sqlserver.examples.named_expressions."
         "order_expressions import prepare_orders_demo;"
diff --git a/src/rhosocial/activerecord/backend/impl/sqlserver/examples/cli/named_query_demo.py b/src/rhosocial/activerecord/backend/impl/sqlserver/examples/cli/named_query_demo.py
index 28017a3..65a7bb0 100644
--- a/src/rhosocial/activerecord/backend/impl/sqlserver/examples/cli/named_query_demo.py
+++ b/src/rhosocial/activerecord/backend/impl/sqlserver/examples/cli/named_query_demo.py
@@ -152,7 +152,8 @@ def prepare_demo_schema():
     """
     code = (
         "import os;"
-        "from rhosocial.activerecord.backend.impl.sqlserver import SQLServerBackend, "
+        "from rhosocial.activerecord.backend.impl.sqlserver.backend import SQLServerBackend;"
+        "from rhosocial.activerecord.backend.impl.sqlserver.config import "
         "SQLServerConnectionConfig;"
         "from rhosocial.activerecord.backend.impl.sqlserver.examples.named_expressions."
         "order_expressions import prepare_orders_demo;"
diff --git a/src/rhosocial/activerecord/backend/impl/sqlserver/examples/connection/quickstart.py b/src/rhosocial/activerecord/backend/impl/sqlserver/examples/connection/quickstart.py
index 1c3a986..e74833f 100644
--- a/src/rhosocial/activerecord/backend/impl/sqlserver/examples/connection/quickstart.py
+++ b/src/rhosocial/activerecord/backend/impl/sqlserver/examples/connection/quickstart.py
@@ -29,10 +29,8 @@
     ColumnConstraintType,
     ColumnDefinition,
 )
-from rhosocial.activerecord.backend.impl.sqlserver import (
-    SQLServerBackend,
-    SQLServerConnectionConfig,
-)
+from rhosocial.activerecord.backend.impl.sqlserver.backend import SQLServerBackend
+from rhosocial.activerecord.backend.impl.sqlserver.config import SQLServerConnectionConfig
 from rhosocial.activerecord.backend.options import ExecutionOptions
 from rhosocial.activerecord.backend.schema import StatementType
 
diff --git a/src/rhosocial/activerecord/backend/impl/sqlserver/examples/ddl/create_index.py b/src/rhosocial/activerecord/backend/impl/sqlserver/examples/ddl/create_index.py
index e52ebf2..748a439 100644
--- a/src/rhosocial/activerecord/backend/impl/sqlserver/examples/ddl/create_index.py
+++ b/src/rhosocial/activerecord/backend/impl/sqlserver/examples/ddl/create_index.py
@@ -7,10 +7,8 @@
 # ============================================================
 # SECTION: Setup (necessary for execution, reference only)
 # ============================================================
-from rhosocial.activerecord.backend.impl.sqlserver import (
-    SQLServerBackend,
-    SQLServerConnectionConfig,
-)
+from rhosocial.activerecord.backend.impl.sqlserver.backend import SQLServerBackend
+from rhosocial.activerecord.backend.impl.sqlserver.config import SQLServerConnectionConfig
 
 config = SQLServerConnectionConfig(
     host=os.environ.get('SQLSERVER_HOST', 'localhost'),
diff --git a/src/rhosocial/activerecord/backend/impl/sqlserver/examples/ddl/create_table.py b/src/rhosocial/activerecord/backend/impl/sqlserver/examples/ddl/create_table.py
index 3ed666f..344ca75 100644
--- a/src/rhosocial/activerecord/backend/impl/sqlserver/examples/ddl/create_table.py
+++ b/src/rhosocial/activerecord/backend/impl/sqlserver/examples/ddl/create_table.py
@@ -7,10 +7,8 @@
 # ============================================================
 # SECTION: Setup (necessary for execution, reference only)
 # ============================================================
-from rhosocial.activerecord.backend.impl.sqlserver import (
-    SQLServerBackend,
-    SQLServerConnectionConfig,
-)
+from rhosocial.activerecord.backend.impl.sqlserver.backend import SQLServerBackend
+from rhosocial.activerecord.backend.impl.sqlserver.config import SQLServerConnectionConfig
 
 config = SQLServerConnectionConfig(
     host=os.environ.get('SQLSERVER_HOST', 'localhost'),
diff --git a/src/rhosocial/activerecord/backend/impl/sqlserver/examples/insert/batch.py b/src/rhosocial/activerecord/backend/impl/sqlserver/examples/insert/batch.py
index f72ee33..3b70e33 100644
--- a/src/rhosocial/activerecord/backend/impl/sqlserver/examples/insert/batch.py
+++ b/src/rhosocial/activerecord/backend/impl/sqlserver/examples/insert/batch.py
@@ -7,10 +7,8 @@
 # ============================================================
 # SECTION: Setup (necessary for execution, reference only)
 # ============================================================
-from rhosocial.activerecord.backend.impl.sqlserver import (
-    SQLServerBackend,
-    SQLServerConnectionConfig,
-)
+from rhosocial.activerecord.backend.impl.sqlserver.backend import SQLServerBackend
+from rhosocial.activerecord.backend.impl.sqlserver.config import SQLServerConnectionConfig
 
 config = SQLServerConnectionConfig(
     host=os.environ.get('SQLSERVER_HOST', 'localhost'),
diff --git a/src/rhosocial/activerecord/backend/impl/sqlserver/examples/insert/output.py b/src/rhosocial/activerecord/backend/impl/sqlserver/examples/insert/output.py
index 13475bb..f1c637d 100644
--- a/src/rhosocial/activerecord/backend/impl/sqlserver/examples/insert/output.py
+++ b/src/rhosocial/activerecord/backend/impl/sqlserver/examples/insert/output.py
@@ -8,10 +8,8 @@
 
 import os
 
-from rhosocial.activerecord.backend.impl.sqlserver import (
-    SQLServerBackend,
-    SQLServerConnectionConfig,
-)
+from rhosocial.activerecord.backend.impl.sqlserver.backend import SQLServerBackend
+from rhosocial.activerecord.backend.impl.sqlserver.config import SQLServerConnectionConfig
 
 
 def get_backend():
diff --git a/src/rhosocial/activerecord/backend/impl/sqlserver/examples/insert/with_output.py b/src/rhosocial/activerecord/backend/impl/sqlserver/examples/insert/with_output.py
index 4470d48..0f19b44 100644
--- a/src/rhosocial/activerecord/backend/impl/sqlserver/examples/insert/with_output.py
+++ b/src/rhosocial/activerecord/backend/impl/sqlserver/examples/insert/with_output.py
@@ -9,10 +9,8 @@
 # ============================================================
 # SECTION: Setup (necessary for execution, reference only)
 # ============================================================
-from rhosocial.activerecord.backend.impl.sqlserver import (
-    SQLServerBackend,
-    SQLServerConnectionConfig,
-)
+from rhosocial.activerecord.backend.impl.sqlserver.backend import SQLServerBackend
+from rhosocial.activerecord.backend.impl.sqlserver.config import SQLServerConnectionConfig
 
 config = SQLServerConnectionConfig(
     host=os.environ.get('SQLSERVER_HOST', 'localhost'),
diff --git a/src/rhosocial/activerecord/backend/impl/sqlserver/examples/named_expressions/order_expressions.py b/src/rhosocial/activerecord/backend/impl/sqlserver/examples/named_expressions/order_expressions.py
index fa6f213..4392c71 100644
--- a/src/rhosocial/activerecord/backend/impl/sqlserver/examples/named_expressions/order_expressions.py
+++ b/src/rhosocial/activerecord/backend/impl/sqlserver/examples/named_expressions/order_expressions.py
@@ -166,7 +166,8 @@ def prepare_orders_demo(backend) -> None:
 if __name__ == "__main__":
     import os
 
-    from rhosocial.activerecord.backend.impl.sqlserver import SQLServerBackend, SQLServerConnectionConfig
+    from rhosocial.activerecord.backend.impl.sqlserver.backend import SQLServerBackend
+    from rhosocial.activerecord.backend.impl.sqlserver.config import SQLServerConnectionConfig
     from rhosocial.activerecord.backend.options import ExecutionOptions
     from rhosocial.activerecord.backend.schema import StatementType
 
diff --git a/src/rhosocial/activerecord/backend/impl/sqlserver/examples/named_procedures/order_workflow.py b/src/rhosocial/activerecord/backend/impl/sqlserver/examples/named_procedures/order_workflow.py
index b7d61b1..700142e 100644
--- a/src/rhosocial/activerecord/backend/impl/sqlserver/examples/named_procedures/order_workflow.py
+++ b/src/rhosocial/activerecord/backend/impl/sqlserver/examples/named_procedures/order_workflow.py
@@ -135,7 +135,8 @@ def run(self, ctx: ProcedureContext) -> None:
 if __name__ == "__main__":
     import os
 
-    from rhosocial.activerecord.backend.impl.sqlserver import SQLServerBackend, SQLServerConnectionConfig
+    from rhosocial.activerecord.backend.impl.sqlserver.backend import SQLServerBackend
+    from rhosocial.activerecord.backend.impl.sqlserver.config import SQLServerConnectionConfig
     from rhosocial.activerecord.backend.impl.sqlserver.examples.named_expressions.order_expressions import (
         prepare_orders_demo,
     )
diff --git a/src/rhosocial/activerecord/backend/impl/sqlserver/examples/query/basic.py b/src/rhosocial/activerecord/backend/impl/sqlserver/examples/query/basic.py
index 9ec486d..861d2b9 100644
--- a/src/rhosocial/activerecord/backend/impl/sqlserver/examples/query/basic.py
+++ b/src/rhosocial/activerecord/backend/impl/sqlserver/examples/query/basic.py
@@ -7,10 +7,8 @@
 # ============================================================
 # SECTION: Setup (necessary for execution, reference only)
 # ============================================================
-from rhosocial.activerecord.backend.impl.sqlserver import (
-    SQLServerBackend,
-    SQLServerConnectionConfig,
-)
+from rhosocial.activerecord.backend.impl.sqlserver.backend import SQLServerBackend
+from rhosocial.activerecord.backend.impl.sqlserver.config import SQLServerConnectionConfig
 from rhosocial.activerecord.backend.options import ExecutionOptions
 from rhosocial.activerecord.backend.schema import StatementType
 
diff --git a/src/rhosocial/activerecord/backend/impl/sqlserver/examples/query/join.py b/src/rhosocial/activerecord/backend/impl/sqlserver/examples/query/join.py
index fe3bf69..d963d87 100644
--- a/src/rhosocial/activerecord/backend/impl/sqlserver/examples/query/join.py
+++ b/src/rhosocial/activerecord/backend/impl/sqlserver/examples/query/join.py
@@ -7,10 +7,8 @@
 # ============================================================
 # SECTION: Setup (necessary for execution, reference only)
 # ============================================================
-from rhosocial.activerecord.backend.impl.sqlserver import (
-    SQLServerBackend,
-    SQLServerConnectionConfig,
-)
+from rhosocial.activerecord.backend.impl.sqlserver.backend import SQLServerBackend
+from rhosocial.activerecord.backend.impl.sqlserver.config import SQLServerConnectionConfig
 from rhosocial.activerecord.backend.options import ExecutionOptions
 from rhosocial.activerecord.backend.schema import StatementType
 
diff --git a/src/rhosocial/activerecord/backend/impl/sqlserver/examples/schema_diff/add_column.py b/src/rhosocial/activerecord/backend/impl/sqlserver/examples/schema_diff/add_column.py
index bf2f93e..a396d05 100644
--- a/src/rhosocial/activerecord/backend/impl/sqlserver/examples/schema_diff/add_column.py
+++ b/src/rhosocial/activerecord/backend/impl/sqlserver/examples/schema_diff/add_column.py
@@ -8,7 +8,7 @@
 """
 
 import os
-from rhosocial.activerecord.backend.impl.sqlserver import SQLServerBackend
+from rhosocial.activerecord.backend.impl.sqlserver.backend import SQLServerBackend
 from rhosocial.activerecord.backend.impl.sqlserver.config import SQLServerConnectionConfig
 
 config = SQLServerConnectionConfig(
diff --git a/src/rhosocial/activerecord/backend/impl/sqlserver/examples/transaction/basic.py b/src/rhosocial/activerecord/backend/impl/sqlserver/examples/transaction/basic.py
index b831684..a9276b5 100644
--- a/src/rhosocial/activerecord/backend/impl/sqlserver/examples/transaction/basic.py
+++ b/src/rhosocial/activerecord/backend/impl/sqlserver/examples/transaction/basic.py
@@ -7,10 +7,8 @@
 # ============================================================
 # SECTION: Setup (necessary for execution, reference only)
 # ============================================================
-from rhosocial.activerecord.backend.impl.sqlserver import (
-    SQLServerBackend,
-    SQLServerConnectionConfig,
-)
+from rhosocial.activerecord.backend.impl.sqlserver.backend import SQLServerBackend
+from rhosocial.activerecord.backend.impl.sqlserver.config import SQLServerConnectionConfig
 
 config = SQLServerConnectionConfig(
     host=os.environ.get('SQLSERVER_HOST', 'localhost'),
diff --git a/src/rhosocial/activerecord/backend/impl/sqlserver/examples/types/json_basic.py b/src/rhosocial/activerecord/backend/impl/sqlserver/examples/types/json_basic.py
index a9aef7d..0700146 100644
--- a/src/rhosocial/activerecord/backend/impl/sqlserver/examples/types/json_basic.py
+++ b/src/rhosocial/activerecord/backend/impl/sqlserver/examples/types/json_basic.py
@@ -10,10 +10,8 @@
 # ============================================================
 # SECTION: Setup (necessary for execution, reference only)
 # ============================================================
-from rhosocial.activerecord.backend.impl.sqlserver import (
-    SQLServerBackend,
-    SQLServerConnectionConfig,
-)
+from rhosocial.activerecord.backend.impl.sqlserver.backend import SQLServerBackend
+from rhosocial.activerecord.backend.impl.sqlserver.config import SQLServerConnectionConfig
 
 config = SQLServerConnectionConfig(
     host=os.environ.get('SQLSERVER_HOST', 'localhost'),
diff --git a/src/rhosocial/activerecord/backend/impl/sqlserver/mixins.py b/src/rhosocial/activerecord/backend/impl/sqlserver/mixins.py
deleted file mode 100644
index a78a5e7..0000000
--- a/src/rhosocial/activerecord/backend/impl/sqlserver/mixins.py
+++ /dev/null
@@ -1,16 +0,0 @@
-# src/rhosocial/activerecord/backend/impl/sqlserver/mixins.py
-"""Backward-compatible re-exports from mixins/ package."""
-
-from .mixins import (
-    SQLServerBackendMixin,
-    SQLServerConcurrencyMixin,
-    SQLServerTypeSupportMixin,
-    SQLServerTypeDDLMixin,
-)
-
-__all__ = [
-    "SQLServerBackendMixin",
-    "SQLServerConcurrencyMixin",
-    "SQLServerTypeSupportMixin",
-    "SQLServerTypeDDLMixin",
-]
diff --git a/src/rhosocial/activerecord/backend/impl/sqlserver/mixins/ddl_table.py b/src/rhosocial/activerecord/backend/impl/sqlserver/mixins/ddl_table.py
index 6d169f0..3fab1f2 100644
--- a/src/rhosocial/activerecord/backend/impl/sqlserver/mixins/ddl_table.py
+++ b/src/rhosocial/activerecord/backend/impl/sqlserver/mixins/ddl_table.py
@@ -1,4 +1,4 @@
-# src/rhosocial/activerecord/backend/impl/sqlserver/mixins/table.py
+# src/rhosocial/activerecord/backend/impl/sqlserver/mixins/ddl_table.py
 from typing import Tuple, TYPE_CHECKING
 
 from .version_constants import SQL_SERVER_2016
diff --git a/src/rhosocial/activerecord/backend/impl/sqlserver/protocols.py b/src/rhosocial/activerecord/backend/impl/sqlserver/protocols.py
deleted file mode 100644
index e980912..0000000
--- a/src/rhosocial/activerecord/backend/impl/sqlserver/protocols.py
+++ /dev/null
@@ -1,42 +0,0 @@
-# src/rhosocial/activerecord/backend/impl/sqlserver/protocols.py
-"""Backward-compatible re-exports from protocols/ package."""
-
-from .protocols import (
-    SQLServerIdentitySupport,
-    SQLServerIndexedViewSupport,
-    SQLServerTableHintSupport,
-    SQLServerOutputSupport,
-    SQLServerTableSupport,
-    SQLServerLockingSupport,
-    SQLServerJSONSupport,
-    SQLServerSetTypeSupport,
-    SQLServerSpatialSupport,
-    SQLServerTemporalTableSupport,
-    SQLServerSequenceSupport,
-    SQLServerFullTextSearchSupport,
-    SQLServerTryCastSupport,
-    SQLServerPaginationSupport,
-    SQLServerMergeSupport,
-    SQLServerPartitionSupport,
-    SQLServerUserDefinedTypeSupport,
-)
-
-__all__ = [
-    "SQLServerIdentitySupport",
-    "SQLServerIndexedViewSupport",
-    "SQLServerTableHintSupport",
-    "SQLServerOutputSupport",
-    "SQLServerTableSupport",
-    "SQLServerLockingSupport",
-    "SQLServerJSONSupport",
-    "SQLServerSetTypeSupport",
-    "SQLServerSpatialSupport",
-    "SQLServerTemporalTableSupport",
-    "SQLServerSequenceSupport",
-    "SQLServerFullTextSearchSupport",
-    "SQLServerTryCastSupport",
-    "SQLServerPaginationSupport",
-    "SQLServerMergeSupport",
-    "SQLServerPartitionSupport",
-    "SQLServerUserDefinedTypeSupport",
-]
diff --git a/tests/conftest.py b/tests/conftest.py
index 3fe232b..1f84e39 100644
--- a/tests/conftest.py
+++ b/tests/conftest.py
@@ -41,7 +41,7 @@ def _prepare_read_committed_snapshot():
     This fixture only checks and warns if the option is not yet on
     (e.g. when running locally without the workflow).
     """
-    from rhosocial.activerecord.backend.impl.sqlserver import SQLServerBackend
+    from rhosocial.activerecord.backend.impl.sqlserver.backend import SQLServerBackend
     from rhosocial.activerecord.backend.impl.sqlserver.config import SQLServerConnectionConfig
 
     scenarios = _load_scenario_map()
diff --git a/tests/providers/basic.py b/tests/providers/basic.py
index b6a4639..aac1bfc 100644
--- a/tests/providers/basic.py
+++ b/tests/providers/basic.py
@@ -520,7 +520,7 @@ def get_worker_connection_params(self, scenario_name: str, fixture_type: str = N
         if pooled_db:
             config_dict = {**config_dict, "database": pooled_db}
         return {
-            "backend_module": "rhosocial.activerecord.backend.impl.sqlserver",
+            "backend_module": "rhosocial.activerecord.backend.impl.sqlserver.backend",
             "backend_class_name": backend_class_name,
             "config_class_module": "rhosocial.activerecord.backend.impl.sqlserver.config",
             "config_class_name": "SQLServerConnectionConfig",
@@ -566,7 +566,7 @@ async def get_dialect(self, scenario_name: str = "default"):
     async def _setup_async_model(
         self, model_class: Type[ActiveRecord], scenario_name: str, table_name: str
     ) -> Type[ActiveRecord]:
-        from rhosocial.activerecord.backend.impl.sqlserver import AsyncSQLServerBackend
+        from rhosocial.activerecord.backend.impl.sqlserver.backend.async_backend import AsyncSQLServerBackend
         _, config = get_scenario(scenario_name)
         await model_class.configure(config, AsyncSQLServerBackend)
         backend_instance = model_class.__backend__
@@ -604,7 +604,7 @@ async def setup_type_case_model(self, scenario_name: str) -> Type[ActiveRecord]:
 
     async def setup_type_test_model(self, scenario_name: str) -> Type[ActiveRecord]:
         import pytest
-        from rhosocial.activerecord.backend.impl.sqlserver import AsyncSQLServerBackend
+        from rhosocial.activerecord.backend.impl.sqlserver.backend.async_backend import AsyncSQLServerBackend
         _, config = get_scenario(scenario_name)
         temp_backend = AsyncSQLServerBackend(connection_config=config)
         await temp_backend.connect()
diff --git a/tests/providers/basic_connection.py b/tests/providers/basic_connection.py
index a83cbfb..9e17fa0 100644
--- a/tests/providers/basic_connection.py
+++ b/tests/providers/basic_connection.py
@@ -8,7 +8,7 @@
 from typing import Type, Tuple, Optional, List
 
 from rhosocial.activerecord.model import ActiveRecord, AsyncActiveRecord
-from rhosocial.activerecord.backend.impl.sqlserver import SQLServerBackend
+from rhosocial.activerecord.backend.impl.sqlserver.backend import SQLServerBackend
 from rhosocial.activerecord.backend.impl.sqlserver.config import SQLServerConnectionConfig
 from rhosocial.activerecord.connection.pool import BackendPool, AsyncBackendPool, PoolConfig
 from rhosocial.activerecord.backend.options import ExecutionOptions
@@ -99,7 +99,7 @@ def setup_sync_pool_and_model(self, scenario_name: str) -> Tuple[BackendPool, Ty
 
     async def setup_async_pool_and_model(self, scenario_name: str) -> Tuple[AsyncBackendPool, Type[AsyncActiveRecord]]:
         """Setup async connection pool and model for context tests."""
-        from rhosocial.activerecord.backend.impl.sqlserver import AsyncSQLServerBackend
+        from rhosocial.activerecord.backend.impl.sqlserver.backend.async_backend import AsyncSQLServerBackend
 
         _, config = get_scenario(scenario_name)
 
diff --git a/tests/providers/events.py b/tests/providers/events.py
index 17a6b23..efba4ca 100644
--- a/tests/providers/events.py
+++ b/tests/providers/events.py
@@ -158,7 +158,7 @@ def __init__(self):
     async def _setup_async_model(
         self, model_class: Type[ActiveRecord], scenario_name: str, table_name: str
     ) -> Type[ActiveRecord]:
-        from rhosocial.activerecord.backend.impl.sqlserver import AsyncSQLServerBackend
+        from rhosocial.activerecord.backend.impl.sqlserver.backend.async_backend import AsyncSQLServerBackend
         from rhosocial.activerecord.backend.options import ExecutionOptions
         from rhosocial.activerecord.backend.schema import StatementType
         from rhosocial.activerecord.backend.expression import DropTableExpression, TableExpression
diff --git a/tests/providers/mixins.py b/tests/providers/mixins.py
index 7e08bff..a943e57 100644
--- a/tests/providers/mixins.py
+++ b/tests/providers/mixins.py
@@ -183,7 +183,7 @@ def __init__(self):
     async def _setup_async_model(
         self, model_class: Type[ActiveRecord], scenario_name: str, table_name: str
     ) -> Type[ActiveRecord]:
-        from rhosocial.activerecord.backend.impl.sqlserver import AsyncSQLServerBackend
+        from rhosocial.activerecord.backend.impl.sqlserver.backend.async_backend import AsyncSQLServerBackend
         from rhosocial.activerecord.backend.options import ExecutionOptions
         from rhosocial.activerecord.backend.schema import StatementType
         from rhosocial.activerecord.backend.expression import DropTableExpression, TableExpression
diff --git a/tests/providers/query.py b/tests/providers/query.py
index 9c6800f..aa3ada1 100644
--- a/tests/providers/query.py
+++ b/tests/providers/query.py
@@ -474,7 +474,7 @@ def get_worker_connection_params(self, scenario_name: str, fixture_type: str = "
         if pooled_db:
             config_dict = {**config_dict, "database": pooled_db}
         return {
-            "backend_module": "rhosocial.activerecord.backend.impl.sqlserver",
+            "backend_module": "rhosocial.activerecord.backend.impl.sqlserver.backend",
             "backend_class_name": backend_class_name,
             "config_class_module": "rhosocial.activerecord.backend.impl.sqlserver.config",
             "config_class_name": "SQLServerConnectionConfig",
@@ -527,7 +527,7 @@ def __init__(self):
     async def _setup_model_async(
         self, model_class: Type[ActiveRecord], scenario_name: str, table_name: str, shared_backend=None
     ) -> Type[ActiveRecord]:
-        from rhosocial.activerecord.backend.impl.sqlserver import AsyncSQLServerBackend
+        from rhosocial.activerecord.backend.impl.sqlserver.backend.async_backend import AsyncSQLServerBackend
         from rhosocial.activerecord.backend.options import ExecutionOptions
         from rhosocial.activerecord.backend.schema import StatementType
         from rhosocial.activerecord.backend.expression import DropTableExpression, TableExpression
@@ -595,7 +595,7 @@ async def setup_blog_fixtures(
 
     async def setup_json_user_fixtures(self, scenario_name: str) -> Tuple[Type[ActiveRecord], ...]:
         import pytest
-        from rhosocial.activerecord.backend.impl.sqlserver import AsyncSQLServerBackend
+        from rhosocial.activerecord.backend.impl.sqlserver.backend.async_backend import AsyncSQLServerBackend
         from rhosocial.activerecord.testsuite.feature.query.fixtures.async_json_models import AsyncJsonUser
         _, config = get_scenario(scenario_name)
         await AsyncJsonUser.configure(config, AsyncSQLServerBackend)
@@ -685,7 +685,7 @@ async def setup_order_item_model(self, scenario_name: str) -> Type[AsyncActiveRe
         from rhosocial.activerecord.backend.options import ExecutionOptions
         from rhosocial.activerecord.backend.schema import StatementType
         from rhosocial.activerecord.backend.expression import DropTableExpression, TableExpression
-        from rhosocial.activerecord.backend.impl.sqlserver import AsyncSQLServerBackend
+        from rhosocial.activerecord.backend.impl.sqlserver.backend.async_backend import AsyncSQLServerBackend
         from providers.fixtures.basic import TABLE_EXPRESSIONS as BASIC_EXPRS
         from providers.fixtures._common import to_sqlserver_ddl_sql
 
@@ -740,7 +740,7 @@ async def cleanup_after_test(self, scenario_name: str) -> None:
 
     async def setup_mixed_schema_fixtures(self, scenario_name: str):
         """(AsyncUser, AsyncOrder, AsyncMixedSchemaOrder) with orders also in SCHEMA_A."""
-        from rhosocial.activerecord.backend.impl.sqlserver import AsyncSQLServerBackend
+        from rhosocial.activerecord.backend.impl.sqlserver.backend.async_backend import AsyncSQLServerBackend
         from rhosocial.activerecord.testsuite.feature.query.cross_schema.mixed_schema_models import (
             AsyncMixedSchemaOrder,
         )
@@ -764,7 +764,7 @@ async def setup_mixed_schema_fixtures(self, scenario_name: str):
 
     async def setup_schema_fixtures(self, scenario_name: str):
         """Two async models in two distinct schemas."""
-        from rhosocial.activerecord.backend.impl.sqlserver import AsyncSQLServerBackend
+        from rhosocial.activerecord.backend.impl.sqlserver.backend.async_backend import AsyncSQLServerBackend
         from rhosocial.activerecord.testsuite.feature.query.fixtures.schema_models import (
             AsyncSchemaCustomer,
             AsyncSchemaOrder,
diff --git a/tests/providers/query_connection.py b/tests/providers/query_connection.py
index 2376338..56e0c4d 100644
--- a/tests/providers/query_connection.py
+++ b/tests/providers/query_connection.py
@@ -8,7 +8,7 @@
 from typing import Type, Tuple, Optional, List
 
 from rhosocial.activerecord.model import ActiveRecord, AsyncActiveRecord
-from rhosocial.activerecord.backend.impl.sqlserver import SQLServerBackend
+from rhosocial.activerecord.backend.impl.sqlserver.backend import SQLServerBackend
 from rhosocial.activerecord.backend.impl.sqlserver.config import SQLServerConnectionConfig
 from rhosocial.activerecord.connection.pool import BackendPool, AsyncBackendPool, PoolConfig
 from rhosocial.activerecord.backend.options import ExecutionOptions
@@ -99,7 +99,7 @@ def setup_sync_pool_and_model(self, scenario_name: str) -> Tuple[BackendPool, Ty
 
     async def setup_async_pool_and_model(self, scenario_name: str) -> Tuple[AsyncBackendPool, Type[AsyncActiveRecord]]:
         """Setup async connection pool and model for query context tests."""
-        from rhosocial.activerecord.backend.impl.sqlserver import AsyncSQLServerBackend
+        from rhosocial.activerecord.backend.impl.sqlserver.backend.async_backend import AsyncSQLServerBackend
 
         _, config = get_scenario(scenario_name)
 
diff --git a/tests/providers/relation.py b/tests/providers/relation.py
index 21f45e8..0b03ae2 100644
--- a/tests/providers/relation.py
+++ b/tests/providers/relation.py
@@ -2,7 +2,7 @@
 from typing import Dict, List, Tuple, Type, Set
 
 from rhosocial.activerecord.model import ActiveRecord, AsyncActiveRecord
-from rhosocial.activerecord.backend.impl.sqlserver import AsyncSQLServerBackend
+from rhosocial.activerecord.backend.impl.sqlserver.backend.async_backend import AsyncSQLServerBackend
 from rhosocial.activerecord.testsuite.feature.relation.interfaces import (
     IRelationSyncProvider,
     IRelationAsyncProvider,
diff --git a/tests/providers/scenarios.py b/tests/providers/scenarios.py
index 537d450..f22f617 100644
--- a/tests/providers/scenarios.py
+++ b/tests/providers/scenarios.py
@@ -4,7 +4,7 @@
 import os
 from dataclasses import replace
 from typing import Dict, Any, Tuple, Type
-from rhosocial.activerecord.backend.impl.sqlserver import SQLServerBackend
+from rhosocial.activerecord.backend.impl.sqlserver.backend import SQLServerBackend
 from rhosocial.activerecord.backend.impl.sqlserver.config import SQLServerConnectionConfig
 from rhosocial.activerecord.testsuite.core.pool import pooled_database_name
 
diff --git a/tests/providers/worker_tasks.py b/tests/providers/worker_tasks.py
index 9d1e30c..10ef206 100644
--- a/tests/providers/worker_tasks.py
+++ b/tests/providers/worker_tasks.py
@@ -13,6 +13,8 @@
 import importlib
 
 
+
+
 def _configure_model_from_params(params: dict, model_class) -> None:
     """
     Configure model from connection parameters.
@@ -60,16 +62,10 @@ async def _async_configure_model_from_params(params: dict, model_class) -> None:
     # Convert sync backend to async backend if needed
     # e.g., MariaDBBackend -> AsyncMariaDBBackend
     if not backend_class.__name__.startswith('Async'):
-        async_backend_class_name = f'Async{backend_class.__name__}'
-        # Try to get from same module
-        if hasattr(backend_module, async_backend_class_name):
-            backend_class = getattr(backend_module, async_backend_class_name)
-        else:
-            # Try to get from parent module (e.g., mariadb.backend.sync -> mariadb.backend)
-            parent_module_name = '.'.join(params['backend_module'].split('.')[:-1])
-            parent_module = importlib.import_module(parent_module_name)
-            if hasattr(parent_module, async_backend_class_name):
-                backend_class = getattr(parent_module, async_backend_class_name)
+        backend_class = getattr(
+            importlib.import_module(f"{params['backend_module']}.async_backend"),
+            f"Async{backend_class.__name__}",
+        )
 
     # Dynamically import config class
     config_module = importlib.import_module(params['config_module'])
diff --git a/tests/rhosocial/activerecord_sqlserver_test/feature/backend/cli/test_cli_info_query.py b/tests/rhosocial/activerecord_sqlserver_test/feature/backend/cli/test_cli_info_query.py
index 9f588e9..bbfaa92 100644
--- a/tests/rhosocial/activerecord_sqlserver_test/feature/backend/cli/test_cli_info_query.py
+++ b/tests/rhosocial/activerecord_sqlserver_test/feature/backend/cli/test_cli_info_query.py
@@ -16,7 +16,8 @@
 
 from rhosocial.activerecord.backend.errors import ConnectionError, QueryError
 from rhosocial.activerecord.backend.dialect.protocols import ExplainSupport
-from rhosocial.activerecord.backend.impl import sqlserver as backend_pkg
+from rhosocial.activerecord.backend.impl.sqlserver import backend as backend_pkg
+from rhosocial.activerecord.backend.impl.sqlserver.backend import async_backend as async_backend_mod
 from rhosocial.activerecord.backend.impl.sqlserver.cli import info as info_mod
 from rhosocial.activerecord.backend.impl.sqlserver.cli import query as query_mod
 from rhosocial.activerecord.backend.impl.sqlserver.dialect import SQLServerDialect
@@ -426,7 +427,7 @@ def test_error_paths_exit_nonzero(self, monkeypatch, connect_error, execute_erro
 class TestQueryAsync:
     def test_async_dispatch_executes_query(self, monkeypatch, capsys):
         cls = _tracking_class(FakeAsyncQueryBackend, "QAsync")
-        monkeypatch.setattr(backend_pkg, "AsyncSQLServerBackend", cls, raising=False)
+        monkeypatch.setattr(async_backend_mod, "AsyncSQLServerBackend", cls, raising=False)
         query_mod.handle(
             make_args(
                 query_mod.create_parser,
@@ -444,7 +445,7 @@ def test_async_errors_exit_nonzero(self, monkeypatch, connect_error, execute_err
         cls = _tracking_class(FakeAsyncQueryBackend, "QAsyncErr")
         cls.connect_error = connect_error
         cls.execute_error = execute_error
-        monkeypatch.setattr(backend_pkg, "AsyncSQLServerBackend", cls, raising=False)
+        monkeypatch.setattr(async_backend_mod, "AsyncSQLServerBackend", cls, raising=False)
         with pytest.raises(SystemExit) as exc:
             query_mod.handle(
                 make_args(query_mod.create_parser, ["query", "--database", "db", "SELECT 1", "--async"])
diff --git a/tests/rhosocial/activerecord_sqlserver_test/feature/backend/cli/test_cli_introspect.py b/tests/rhosocial/activerecord_sqlserver_test/feature/backend/cli/test_cli_introspect.py
index 2033eda..c57df5b 100644
--- a/tests/rhosocial/activerecord_sqlserver_test/feature/backend/cli/test_cli_introspect.py
+++ b/tests/rhosocial/activerecord_sqlserver_test/feature/backend/cli/test_cli_introspect.py
@@ -11,7 +11,8 @@
 import pytest
 
 from rhosocial.activerecord.backend.errors import ConnectionError, QueryError
-from rhosocial.activerecord.backend.impl import sqlserver as backend_pkg
+from rhosocial.activerecord.backend.impl.sqlserver import backend as backend_pkg
+from rhosocial.activerecord.backend.impl.sqlserver.backend import async_backend as async_backend_mod
 from rhosocial.activerecord.backend.impl.sqlserver.cli import introspect as introspect_mod
 
 
@@ -291,7 +292,7 @@ def init_with_exploding(self, connection_config=None):
 class TestHandleAsync:
     def test_async_tables_dispatch(self, monkeypatch, capsys):
         monkeypatch.setattr(
-            backend_pkg,
+            async_backend_mod,
             "AsyncSQLServerBackend",
             _tracking_class(FakeAsyncBackendBase, "AsyncFake"),
             raising=False,
@@ -305,7 +306,7 @@ def test_async_tables_dispatch(self, monkeypatch, capsys):
     def test_async_connection_error_exits_nonzero(self, monkeypatch):
         cls = _tracking_class(FakeAsyncBackendBase, "AsyncErr")
         cls.connect_error = ConnectionError("refused")
-        monkeypatch.setattr(backend_pkg, "AsyncSQLServerBackend", cls, raising=False)
+        monkeypatch.setattr(async_backend_mod, "AsyncSQLServerBackend", cls, raising=False)
         with pytest.raises(SystemExit) as exc:
             introspect_mod.handle(
                 make_args(["introspect", "tables", "--database", "db", "--async"])
diff --git a/tests/rhosocial/activerecord_sqlserver_test/feature/backend/cli/test_cli_status.py b/tests/rhosocial/activerecord_sqlserver_test/feature/backend/cli/test_cli_status.py
index cbce24c..3c6e073 100644
--- a/tests/rhosocial/activerecord_sqlserver_test/feature/backend/cli/test_cli_status.py
+++ b/tests/rhosocial/activerecord_sqlserver_test/feature/backend/cli/test_cli_status.py
@@ -12,7 +12,8 @@
 
 from rhosocial.activerecord.backend.errors import ConnectionError, QueryError
 from rhosocial.activerecord.backend.impl.sqlserver.cli import status as status_mod
-from rhosocial.activerecord.backend.impl import sqlserver as backend_pkg
+from rhosocial.activerecord.backend.impl.sqlserver import backend as backend_pkg
+from rhosocial.activerecord.backend.impl.sqlserver.backend import async_backend as async_backend_mod
 
 STATUS_INTROSPECTOR_MODULE = (
     "rhosocial.activerecord.backend.impl.sqlserver.introspection.status_introspector"
@@ -441,7 +442,7 @@ def test_async_overview_dispatch(self, fake_async_backend_cls, monkeypatch, caps
             f"{STATUS_INTROSPECTOR_MODULE}.AsyncSQLServerStatusIntrospector",
             AsyncRecordingIntrospector,
         )
-        monkeypatch.setattr(backend_pkg, "AsyncSQLServerBackend", fake_async_backend_cls, raising=False)
+        monkeypatch.setattr(async_backend_mod, "AsyncSQLServerBackend", fake_async_backend_cls, raising=False)
         status_mod.handle(
             make_args(["status", "all", "--database", "db", "-o", "json", "--async"])
         )
@@ -450,7 +451,7 @@ def test_async_overview_dispatch(self, fake_async_backend_cls, monkeypatch, caps
 
     def test_async_connection_error_exits_nonzero(self, fake_async_backend_cls, monkeypatch):
         fake_async_backend_cls.connect_error = ConnectionError("refused")
-        monkeypatch.setattr(backend_pkg, "AsyncSQLServerBackend", fake_async_backend_cls, raising=False)
+        monkeypatch.setattr(async_backend_mod, "AsyncSQLServerBackend", fake_async_backend_cls, raising=False)
         with pytest.raises(SystemExit) as exc:
             status_mod.handle(make_args(["status", "all", "--database", "db", "--async"]))
         assert exc.value.code == 1
@@ -463,7 +464,7 @@ async def get_overview(self):
         monkeypatch.setattr(
             f"{STATUS_INTROSPECTOR_MODULE}.AsyncSQLServerStatusIntrospector", ExplodingAsync
         )
-        monkeypatch.setattr(backend_pkg, "AsyncSQLServerBackend", fake_async_backend_cls, raising=False)
+        monkeypatch.setattr(async_backend_mod, "AsyncSQLServerBackend", fake_async_backend_cls, raising=False)
         with pytest.raises(SystemExit) as exc:
             status_mod.handle(make_args(["status", "all", "--database", "db", "--async"]))
         assert exc.value.code == 1
diff --git a/tests/rhosocial/activerecord_sqlserver_test/feature/backend/conftest.py b/tests/rhosocial/activerecord_sqlserver_test/feature/backend/conftest.py
index 4133a3c..ed8800e 100644
--- a/tests/rhosocial/activerecord_sqlserver_test/feature/backend/conftest.py
+++ b/tests/rhosocial/activerecord_sqlserver_test/feature/backend/conftest.py
@@ -5,11 +5,9 @@
 import os
 from typing import Dict, Any, Tuple, Type
 
-from rhosocial.activerecord.backend.impl.sqlserver import (
-    SQLServerBackend,
-    AsyncSQLServerBackend,
-    SQLServerConnectionConfig,
-)
+from rhosocial.activerecord.backend.impl.sqlserver.backend import SQLServerBackend
+from rhosocial.activerecord.backend.impl.sqlserver.config import SQLServerConnectionConfig
+from rhosocial.activerecord.backend.impl.sqlserver.backend.async_backend import AsyncSQLServerBackend
 
 SCENARIO_MAP: Dict[str, Dict[str, Any]] = {}
 
diff --git a/tests/rhosocial/activerecord_sqlserver_test/feature/backend/test_async_concurrency.py b/tests/rhosocial/activerecord_sqlserver_test/feature/backend/test_async_concurrency.py
index 96a8bba..433df70 100644
--- a/tests/rhosocial/activerecord_sqlserver_test/feature/backend/test_async_concurrency.py
+++ b/tests/rhosocial/activerecord_sqlserver_test/feature/backend/test_async_concurrency.py
@@ -32,7 +32,7 @@
 
 from rhosocial.activerecord.model import AsyncActiveRecord
 from rhosocial.activerecord.base.field_proxy import FieldProxy
-from rhosocial.activerecord.backend.impl.sqlserver import AsyncSQLServerBackend
+from rhosocial.activerecord.backend.impl.sqlserver.backend.async_backend import AsyncSQLServerBackend
 
 logger = logging.getLogger(__name__)
 
diff --git a/tests/rhosocial/activerecord_sqlserver_test/feature/backend/test_async_error_handling.py b/tests/rhosocial/activerecord_sqlserver_test/feature/backend/test_async_error_handling.py
index 5e54247..ef308e5 100644
--- a/tests/rhosocial/activerecord_sqlserver_test/feature/backend/test_async_error_handling.py
+++ b/tests/rhosocial/activerecord_sqlserver_test/feature/backend/test_async_error_handling.py
@@ -7,7 +7,7 @@
     DeadlockError,
     OperationalError,
 )
-from rhosocial.activerecord.backend.impl.sqlserver import AsyncSQLServerBackend
+from rhosocial.activerecord.backend.impl.sqlserver.backend.async_backend import AsyncSQLServerBackend
 
 
 @pytest_asyncio.fixture
diff --git a/tests/rhosocial/activerecord_sqlserver_test/feature/backend/test_async_transaction_isolation_effect.py b/tests/rhosocial/activerecord_sqlserver_test/feature/backend/test_async_transaction_isolation_effect.py
index fc63825..d25446f 100644
--- a/tests/rhosocial/activerecord_sqlserver_test/feature/backend/test_async_transaction_isolation_effect.py
+++ b/tests/rhosocial/activerecord_sqlserver_test/feature/backend/test_async_transaction_isolation_effect.py
@@ -10,7 +10,7 @@
 import asyncio
 from decimal import Decimal
 
-from rhosocial.activerecord.backend.impl.sqlserver import AsyncSQLServerBackend
+from rhosocial.activerecord.backend.impl.sqlserver.backend.async_backend import AsyncSQLServerBackend
 from rhosocial.activerecord.backend.transaction import IsolationLevel, TransactionMode
 
 
diff --git a/tests/rhosocial/activerecord_sqlserver_test/feature/backend/test_backend_mixin_validation.py b/tests/rhosocial/activerecord_sqlserver_test/feature/backend/test_backend_mixin_validation.py
index d70d090..df5ae53 100644
--- a/tests/rhosocial/activerecord_sqlserver_test/feature/backend/test_backend_mixin_validation.py
+++ b/tests/rhosocial/activerecord_sqlserver_test/feature/backend/test_backend_mixin_validation.py
@@ -9,7 +9,7 @@
 
 import pytest
 
-from rhosocial.activerecord.backend.impl.sqlserver import SQLServerBackend
+from rhosocial.activerecord.backend.impl.sqlserver.backend import SQLServerBackend
 from rhosocial.activerecord.backend.impl.sqlserver.config import SQLServerConnectionConfig
 
 
diff --git a/tests/rhosocial/activerecord_sqlserver_test/feature/backend/test_ddl_source_mixin.py b/tests/rhosocial/activerecord_sqlserver_test/feature/backend/test_ddl_source_mixin.py
index c0c0119..18c1070 100644
--- a/tests/rhosocial/activerecord_sqlserver_test/feature/backend/test_ddl_source_mixin.py
+++ b/tests/rhosocial/activerecord_sqlserver_test/feature/backend/test_ddl_source_mixin.py
@@ -22,7 +22,7 @@
     PartitionClause,
     PartitionStrategy,
 )
-from rhosocial.activerecord.backend.impl.sqlserver import SQLServerDialect
+from rhosocial.activerecord.backend.impl.sqlserver.dialect import SQLServerDialect
 from rhosocial.activerecord.backend.impl.sqlserver.expression.column import (
     SQLServerColumnOptions,
 )
diff --git a/tests/rhosocial/activerecord_sqlserver_test/feature/backend/test_execution_options.py b/tests/rhosocial/activerecord_sqlserver_test/feature/backend/test_execution_options.py
index 1ada365..14a9124 100644
--- a/tests/rhosocial/activerecord_sqlserver_test/feature/backend/test_execution_options.py
+++ b/tests/rhosocial/activerecord_sqlserver_test/feature/backend/test_execution_options.py
@@ -5,11 +5,9 @@
 
 from rhosocial.activerecord.backend.base import StorageBackend
 from rhosocial.activerecord.backend.errors import DatabaseError
-from rhosocial.activerecord.backend.impl.sqlserver import (
-    AsyncSQLServerBackend,
-    SQLServerBackend,
-    SQLServerExecutionOptions,
-)
+from rhosocial.activerecord.backend.impl.sqlserver.backend import SQLServerBackend
+from rhosocial.activerecord.backend.impl.sqlserver.options import SQLServerExecutionOptions
+from rhosocial.activerecord.backend.impl.sqlserver.backend.async_backend import AsyncSQLServerBackend
 from rhosocial.activerecord.backend.impl.sqlserver.config import SQLServerConnectionConfig
 from rhosocial.activerecord.backend.options import ExecutionOptions, StatementType
 
diff --git a/tests/rhosocial/activerecord_sqlserver_test/feature/backend/test_introspection_sql_builders.py b/tests/rhosocial/activerecord_sqlserver_test/feature/backend/test_introspection_sql_builders.py
index c3cebe8..96424b5 100644
--- a/tests/rhosocial/activerecord_sqlserver_test/feature/backend/test_introspection_sql_builders.py
+++ b/tests/rhosocial/activerecord_sqlserver_test/feature/backend/test_introspection_sql_builders.py
@@ -5,7 +5,7 @@
 now returns parameterized SQL (``?`` placeholders) with separate params,
 instead of string-interpolated values.
 """
-from rhosocial.activerecord.backend.impl.sqlserver import SQLServerBackend
+from rhosocial.activerecord.backend.impl.sqlserver.backend import SQLServerBackend
 from rhosocial.activerecord.backend.impl.sqlserver.config import SQLServerConnectionConfig
 from rhosocial.activerecord.backend.impl.sqlserver.introspection import (
     SyncSQLServerIntrospector,
diff --git a/tests/rhosocial/activerecord_sqlserver_test/feature/backend/test_sqlserver_column_definition.py b/tests/rhosocial/activerecord_sqlserver_test/feature/backend/test_sqlserver_column_definition.py
index 0dcb7e7..bb93bde 100644
--- a/tests/rhosocial/activerecord_sqlserver_test/feature/backend/test_sqlserver_column_definition.py
+++ b/tests/rhosocial/activerecord_sqlserver_test/feature/backend/test_sqlserver_column_definition.py
@@ -13,7 +13,7 @@
 
 @pytest.fixture
 def dialect():
-    from rhosocial.activerecord.backend.impl.sqlserver import SQLServerDialect
+    from rhosocial.activerecord.backend.impl.sqlserver.dialect import SQLServerDialect
 
     return SQLServerDialect((2022, 0, 0))
 
diff --git a/tests/rhosocial/activerecord_sqlserver_test/feature/backend/test_sqlserver_type_ddl.py b/tests/rhosocial/activerecord_sqlserver_test/feature/backend/test_sqlserver_type_ddl.py
index ce6ec0e..cf583b5 100644
--- a/tests/rhosocial/activerecord_sqlserver_test/feature/backend/test_sqlserver_type_ddl.py
+++ b/tests/rhosocial/activerecord_sqlserver_test/feature/backend/test_sqlserver_type_ddl.py
@@ -140,7 +140,7 @@ def test_backend_passes_deployment_target_from_connection_config():
 
 def test_async_backend_passes_deployment_target_from_connection_config():
     pytest.importorskip("aioodbc")
-    from rhosocial.activerecord.backend.impl.sqlserver.async_backend import (
+    from rhosocial.activerecord.backend.impl.sqlserver.backend.async_backend import (
         AsyncSQLServerBackend,
     )
 
diff --git a/tests/rhosocial/activerecord_sqlserver_test/feature/backend/test_ssl_connection_params.py b/tests/rhosocial/activerecord_sqlserver_test/feature/backend/test_ssl_connection_params.py
new file mode 100644
index 0000000..faaab9f
--- /dev/null
+++ b/tests/rhosocial/activerecord_sqlserver_test/feature/backend/test_ssl_connection_params.py
@@ -0,0 +1,65 @@
+# tests/rhosocial/activerecord_sqlserver_test/feature/backend/test_ssl_connection_params.py
+"""Regression tests: SQL Server TLS settings must reach the ODBC connection string.
+
+``build_connection_string()`` is the only place ``pyodbc`` gets its
+configuration, so anything the config exposes for TLS has to appear there.
+"""
+
+import pytest
+
+from rhosocial.activerecord.backend.impl.sqlserver.config import SQLServerConnectionConfig
+
+
+def make_config(**kwargs):
+    defaults = dict(host="db.example.com", database="test_db", username="sa", password="secret")
+    defaults.update(kwargs)
+    return SQLServerConnectionConfig(**defaults)
+
+
+def test_encryption_is_on_by_default():
+    assert "Encrypt=yes" in make_config().build_connection_string()
+    assert "TrustServerCertificate=no" in make_config().build_connection_string()
+
+
+def test_encrypt_can_be_disabled():
+    conn_str = make_config(encrypt=False).build_connection_string()
+    assert "Encrypt=no" in conn_str
+
+
+def test_trust_server_certificate_is_forwarded():
+    conn_str = make_config(trust_server_certificate=True).build_connection_string()
+    assert "TrustServerCertificate=yes" in conn_str
+
+
+def test_client_certificate_is_forwarded():
+    conn_str = make_config(
+        client_certificate="/certs/client.pem",
+        client_key="/certs/client.key",
+    ).build_connection_string()
+    assert "ClientCertificate=/certs/client.pem" in conn_str
+    assert "ClientKey=/certs/client.key" in conn_str
+
+
+def test_host_name_in_certificate_is_forwarded():
+    """Needed when the server certificate CN is not the connect host."""
+    conn_str = make_config(host_name_in_certificate="db.internal").build_connection_string()
+    assert "HostNameInCertificate=db.internal" in conn_str
+
+
+def test_client_key_password_is_forwarded():
+    conn_str = make_config(
+        client_certificate="/certs/client.pfx",
+        client_key_password="pfx-secret",
+    ).build_connection_string()
+    assert "ClientKeyPassword=pfx-secret" in conn_str
+
+
+def test_no_client_tls_keys_when_unset():
+    conn_str = make_config().build_connection_string()
+    for key in ("ClientCertificate", "ClientKey", "ClientKeyPassword", "HostNameInCertificate"):
+        assert key not in conn_str
+
+
+def test_client_key_without_certificate_is_rejected():
+    with pytest.raises(ValueError, match="client_key requires client_certificate"):
+        make_config(client_key="/certs/client.key").validate_config()
diff --git a/tests/rhosocial/activerecord_sqlserver_test/feature/backend/test_transaction_isolation_effect.py b/tests/rhosocial/activerecord_sqlserver_test/feature/backend/test_transaction_isolation_effect.py
index ae266b2..89a5231 100644
--- a/tests/rhosocial/activerecord_sqlserver_test/feature/backend/test_transaction_isolation_effect.py
+++ b/tests/rhosocial/activerecord_sqlserver_test/feature/backend/test_transaction_isolation_effect.py
@@ -16,7 +16,7 @@
 import time
 from decimal import Decimal
 
-from rhosocial.activerecord.backend.impl.sqlserver import SQLServerBackend
+from rhosocial.activerecord.backend.impl.sqlserver.backend import SQLServerBackend
 from rhosocial.activerecord.backend.transaction import IsolationLevel
 
 
diff --git a/tests/rhosocial/activerecord_sqlserver_test/feature/connection/conftest.py b/tests/rhosocial/activerecord_sqlserver_test/feature/connection/conftest.py
index 0915d3a..60e1b02 100644
--- a/tests/rhosocial/activerecord_sqlserver_test/feature/connection/conftest.py
+++ b/tests/rhosocial/activerecord_sqlserver_test/feature/connection/conftest.py
@@ -14,7 +14,8 @@
 import pytest_asyncio
 import yaml
 
-from rhosocial.activerecord.backend.impl.sqlserver import SQLServerBackend, AsyncSQLServerBackend
+from rhosocial.activerecord.backend.impl.sqlserver.backend import SQLServerBackend
+from rhosocial.activerecord.backend.impl.sqlserver.backend.async_backend import AsyncSQLServerBackend
 from rhosocial.activerecord.backend.impl.sqlserver.config import SQLServerConnectionConfig
 from rhosocial.activerecord.connection.pool import (
     PoolConfig,
diff --git a/tests/rhosocial/activerecord_sqlserver_test/feature/query/test_collation_expression.py b/tests/rhosocial/activerecord_sqlserver_test/feature/query/test_collation_expression.py
index ae70d77..7bd0a0f 100644
--- a/tests/rhosocial/activerecord_sqlserver_test/feature/query/test_collation_expression.py
+++ b/tests/rhosocial/activerecord_sqlserver_test/feature/query/test_collation_expression.py
@@ -6,7 +6,8 @@
 import pytest
 
 from rhosocial.activerecord.backend.expression import Column, Literal
-from rhosocial.activerecord.backend.impl.sqlserver import SQLServerCollation, SQLServerDialect
+from rhosocial.activerecord.backend.impl.sqlserver.collation import SQLServerCollation
+from rhosocial.activerecord.backend.impl.sqlserver.dialect import SQLServerDialect
 
 
 @pytest.fixture