diff --git a/.github/workflows/README.md b/.github/workflows/README.md
index 00a8f54ac..ef6a8bb3c 100644
--- a/.github/workflows/README.md
+++ b/.github/workflows/README.md
@@ -4,6 +4,7 @@ Llama Stack uses GitHub Actions for Continuous Integration (CI). Below is a tabl
 
 | Name | File | Purpose |
 | ---- | ---- | ------- |
+| Backward Compatibility Check | [backward-compat.yml](backward-compat.yml) | Check backward compatibility for run.yaml configs |
 | Update Changelog | [changelog.yml](changelog.yml) | Creates PR for updating the CHANGELOG.md |
 | API Conformance Tests | [conformance.yml](conformance.yml) | Run the API Conformance test suite on the changes. |
 | Installer CI | [install-script-ci.yml](install-script-ci.yml) | Test the installation script |
diff --git a/.github/workflows/backward-compat.yml b/.github/workflows/backward-compat.yml
new file mode 100644
index 000000000..857120af7
--- /dev/null
+++ b/.github/workflows/backward-compat.yml
@@ -0,0 +1,384 @@
+name: Backward Compatibility Check
+
+run-name: Check backward compatibility for run.yaml configs
+
+on:
+  pull_request:
+    branches: [main]
+    paths:
+      - 'src/llama_stack/core/datatypes.py'
+      - 'src/llama_stack/providers/datatypes.py'
+      - 'src/llama_stack/distributions/**/run.yaml'
+      - 'tests/backward_compat/**'
+      - '.github/workflows/backward-compat.yml'
+
+concurrency:
+  group: ${{ github.workflow }}-${{ github.ref }}
+  cancel-in-progress: true
+
+jobs:
+  check-main-compatibility:
+    name: Check Compatibility with main
+    runs-on: ubuntu-latest
+
+    steps:
+      - name: Checkout PR branch
+        uses: actions/checkout@08c6903cd8c0fde910a37f88322edcfb5dd907a8 # v5.0.0
+        with:
+          fetch-depth: 0  # Need full history to access main branch
+
+      - name: Set up Python
+        uses: actions/setup-python@e797f83bcb11b83ae66e0230d6156d7c80228e7c # v6.0.0
+        with:
+          python-version: '3.12'
+
+      - name: Install uv
+        uses: astral-sh/setup-uv@6b9c6063abd6010835644d4c2e1bef4cf5cd0fca # v6.0.1
+        with:
+          enable-cache: true
+
+      - name: Install dependencies
+        run: |
+          uv sync --group dev
+
+      - name: Extract run.yaml files from main branch
+        id: extract_configs
+        run: |
+          # Get list of run.yaml paths from main
+          git fetch origin main
+          CONFIG_PATHS=$(git ls-tree -r --name-only origin/main | grep "src/llama_stack/distributions/.*/run.yaml$" || true)
+
+          if [ -z "$CONFIG_PATHS" ]; then
+            echo "No run.yaml files found in main branch"
+            exit 1
+          fi
+
+          # Extract all configs to a temp directory
+          mkdir -p /tmp/main_configs
+          echo "Extracting configs from main branch:"
+
+          while IFS= read -r config_path; do
+            if [ -z "$config_path" ]; then
+              continue
+            fi
+
+            # Extract filename for storage
+            filename=$(basename $(dirname "$config_path"))
+            echo "  - $filename (from $config_path)"
+
+            git show origin/main:"$config_path" > "/tmp/main_configs/${filename}.yaml"
+          done <<< "$CONFIG_PATHS"
+
+          echo ""
+          echo "Extracted $(ls /tmp/main_configs/*.yaml | wc -l) config files"
+
+      - name: Test all configs from main
+        id: test_configs
+        continue-on-error: true
+        run: |
+          # Run pytest once with all configs parameterized
+          if COMPAT_TEST_CONFIGS_DIR=/tmp/main_configs uv run pytest tests/backward_compat/test_run_config.py -v; then
+            echo "failed=false" >> $GITHUB_OUTPUT
+          else
+            echo "failed=true" >> $GITHUB_OUTPUT
+            exit 1
+          fi
+
+      - name: Check for breaking change acknowledgment
+        id: check_ack
+        if: steps.test_configs.outputs.failed == 'true'
+        run: |
+          echo "Breaking changes detected. Checking for acknowledgment..."
+
+          # Check PR title for '!:' marker (conventional commits)
+          PR_TITLE="${{ github.event.pull_request.title }}"
+          if [[ "$PR_TITLE" =~ ^[a-z]+\!: ]]; then
+            echo "✓ Breaking change acknowledged in PR title"
+            echo "acknowledged=true" >> $GITHUB_OUTPUT
+            exit 0
+          fi
+
+          # Check commit messages for BREAKING CHANGE:
+          if git log origin/main..HEAD --format=%B | grep -q "BREAKING CHANGE:"; then
+            echo "✓ Breaking change acknowledged in commit message"
+            echo "acknowledged=true" >> $GITHUB_OUTPUT
+            exit 0
+          fi
+
+          echo "✗ Breaking change NOT acknowledged"
+          echo "acknowledged=false" >> $GITHUB_OUTPUT
+        env:
+          GH_TOKEN: ${{ github.token }}
+
+      - name: Evaluate results
+        if: always()
+        run: |
+          FAILED="${{ steps.test_configs.outputs.failed }}"
+          ACKNOWLEDGED="${{ steps.check_ack.outputs.acknowledged }}"
+
+          if [[ "$FAILED" == "true" ]]; then
+            if [[ "$ACKNOWLEDGED" == "true" ]]; then
+              echo ""
+              echo "⚠️  WARNING: Breaking changes detected but acknowledged"
+              echo ""
+              echo "This PR introduces backward-incompatible changes to run.yaml."
+              echo "The changes have been properly acknowledged."
+              echo ""
+              exit 0  # Pass the check
+            else
+              echo ""
+              echo "❌ ERROR: Breaking changes detected without acknowledgment"
+              echo ""
+              echo "This PR introduces backward-incompatible changes to run.yaml"
+              echo "that will break existing user configurations."
+              echo ""
+              echo "To acknowledge this breaking change, do ONE of:"
+              echo "  1. Add '!:' to your PR title (e.g., 'feat!: change xyz')"
+              echo "  2. Add the 'breaking-change' label to this PR"
+              echo "  3. Include 'BREAKING CHANGE:' in a commit message"
+              echo ""
+              exit 1  # Fail the check
+            fi
+          fi
+
+  test-integration-main:
+    name: Run Integration Tests with main Config
+    runs-on: ubuntu-latest
+
+    steps:
+      - name: Checkout PR branch
+        uses: actions/checkout@08c6903cd8c0fde910a37f88322edcfb5dd907a8 # v5.0.0
+        with:
+          fetch-depth: 0
+
+      - name: Extract ci-tests run.yaml from main
+        run: |
+          git fetch origin main
+          git show origin/main:src/llama_stack/distributions/ci-tests/run.yaml > /tmp/main-ci-tests-run.yaml
+          echo "Extracted ci-tests run.yaml from main branch"
+
+      - name: Setup test environment
+        uses: ./.github/actions/setup-test-environment
+        with:
+          python-version: '3.12'
+          client-version: 'latest'
+          setup: 'ollama'
+          suite: 'base'
+          inference-mode: 'replay'
+
+      - name: Run integration tests with main config
+        id: test_integration
+        continue-on-error: true
+        uses: ./.github/actions/run-and-record-tests
+        with:
+          stack-config: /tmp/main-ci-tests-run.yaml
+          setup: 'ollama'
+          inference-mode: 'replay'
+          suite: 'base'
+
+      - name: Check for breaking change acknowledgment
+        id: check_ack
+        if: steps.test_integration.outcome == 'failure'
+        run: |
+          echo "Integration tests failed. Checking for acknowledgment..."
+
+          # Check PR title for '!:' marker (conventional commits)
+          PR_TITLE="${{ github.event.pull_request.title }}"
+          if [[ "$PR_TITLE" =~ ^[a-z]+\!: ]]; then
+            echo "✓ Breaking change acknowledged in PR title"
+            echo "acknowledged=true" >> $GITHUB_OUTPUT
+            exit 0
+          fi
+
+          # Check commit messages for BREAKING CHANGE:
+          if git log origin/main..HEAD --format=%B | grep -q "BREAKING CHANGE:"; then
+            echo "✓ Breaking change acknowledged in commit message"
+            echo "acknowledged=true" >> $GITHUB_OUTPUT
+            exit 0
+          fi
+
+          echo "✗ Breaking change NOT acknowledged"
+          echo "acknowledged=false" >> $GITHUB_OUTPUT
+        env:
+          GH_TOKEN: ${{ github.token }}
+
+      - name: Evaluate integration test results
+        if: always()
+        run: |
+          TEST_FAILED="${{ steps.test_integration.outcome == 'failure' }}"
+          ACKNOWLEDGED="${{ steps.check_ack.outputs.acknowledged }}"
+
+          if [[ "$TEST_FAILED" == "true" ]]; then
+            if [[ "$ACKNOWLEDGED" == "true" ]]; then
+              echo ""
+              echo "⚠️  WARNING: Integration tests failed with main config but acknowledged"
+              echo ""
+              exit 0  # Pass the check
+            else
+              echo ""
+              echo "❌ ERROR: Integration tests failed with main config without acknowledgment"
+              echo ""
+              echo "To acknowledge this breaking change, do ONE of:"
+              echo "  1. Add '!:' to your PR title (e.g., 'feat!: change xyz')"
+              echo "  2. Include 'BREAKING CHANGE:' in a commit message"
+              echo ""
+              exit 1  # Fail the check
+            fi
+          fi
+
+  test-integration-release:
+    name: Run Integration Tests with Latest Release (Informational)
+    runs-on: ubuntu-latest
+
+    steps:
+      - name: Checkout PR branch
+        uses: actions/checkout@08c6903cd8c0fde910a37f88322edcfb5dd907a8 # v5.0.0
+        with:
+          fetch-depth: 0
+
+      - name: Get latest release
+        id: get_release
+        run: |
+          # Get the latest release from GitHub
+          LATEST_TAG=$(gh release list --limit 1 --json tagName --jq '.[0].tagName' 2>/dev/null || echo "")
+
+          if [ -z "$LATEST_TAG" ]; then
+            echo "No releases found, skipping release compatibility check"
+            echo "has_release=false" >> $GITHUB_OUTPUT
+            exit 0
+          fi
+
+          echo "Latest release: $LATEST_TAG"
+          echo "has_release=true" >> $GITHUB_OUTPUT
+          echo "tag=$LATEST_TAG" >> $GITHUB_OUTPUT
+        env:
+          GH_TOKEN: ${{ github.token }}
+
+      - name: Extract ci-tests run.yaml from release
+        if: steps.get_release.outputs.has_release == 'true'
+        id: extract_config
+        run: |
+          RELEASE_TAG="${{ steps.get_release.outputs.tag }}"
+
+          if git show "$RELEASE_TAG:src/llama_stack/distributions/ci-tests/run.yaml" > /tmp/release-ci-tests-run.yaml 2>/dev/null; then
+            echo "Extracted ci-tests run.yaml from release $RELEASE_TAG"
+            echo "has_config=true" >> $GITHUB_OUTPUT
+          else
+            echo "::warning::ci-tests/run.yaml not found in release $RELEASE_TAG"
+            echo "has_config=false" >> $GITHUB_OUTPUT
+          fi
+
+      - name: Setup test environment
+        if: steps.get_release.outputs.has_release == 'true' && steps.extract_config.outputs.has_config == 'true'
+        uses: ./.github/actions/setup-test-environment
+        with:
+          python-version: '3.12'
+          client-version: 'latest'
+          setup: 'ollama'
+          suite: 'base'
+          inference-mode: 'replay'
+
+      - name: Run integration tests with release config
+        if: steps.get_release.outputs.has_release == 'true' && steps.extract_config.outputs.has_config == 'true'
+        uses: ./.github/actions/run-and-record-tests
+        with:
+          stack-config: /tmp/release-ci-tests-run.yaml
+          setup: 'ollama'
+          inference-mode: 'replay'
+          suite: 'base'
+
+      - name: Report results
+        if: always() && steps.get_release.outputs.has_release == 'true' && steps.extract_config.outputs.has_config == 'true'
+        run: |
+          RELEASE_TAG="${{ steps.get_release.outputs.tag }}"
+          echo "::warning::Integration tests against release $RELEASE_TAG completed"
+          echo "::warning::This is informational only - does not block merge"
+
+  check-schema-release-compatibility:
+    name: Check Schema Compatibility with Latest Release (Informational)
+    runs-on: ubuntu-latest
+
+    steps:
+      - name: Checkout PR branch
+        uses: actions/checkout@08c6903cd8c0fde910a37f88322edcfb5dd907a8 # v5.0.0
+        with:
+          fetch-depth: 0
+
+      - name: Set up Python
+        uses: actions/setup-python@e797f83bcb11b83ae66e0230d6156d7c80228e7c # v6.0.0
+        with:
+          python-version: '3.12'
+
+      - name: Install uv
+        uses: astral-sh/setup-uv@6b9c6063abd6010835644d4c2e1bef4cf5cd0fca # v6.0.1
+        with:
+          enable-cache: true
+
+      - name: Install dependencies
+        run: |
+          uv sync --group dev
+
+      - name: Get latest release
+        id: get_release
+        run: |
+          # Get the latest release from GitHub
+          LATEST_TAG=$(gh release list --limit 1 --json tagName --jq '.[0].tagName' 2>/dev/null || echo "")
+
+          if [ -z "$LATEST_TAG" ]; then
+            echo "No releases found, skipping release compatibility check"
+            echo "has_release=false" >> $GITHUB_OUTPUT
+            exit 0
+          fi
+
+          echo "Latest release: $LATEST_TAG"
+          echo "has_release=true" >> $GITHUB_OUTPUT
+          echo "tag=$LATEST_TAG" >> $GITHUB_OUTPUT
+        env:
+          GH_TOKEN: ${{ github.token }}
+
+      - name: Extract configs from release
+        if: steps.get_release.outputs.has_release == 'true'
+        id: extract_release_configs
+        run: |
+          RELEASE_TAG="${{ steps.get_release.outputs.tag }}"
+
+          # Get run.yaml files from the release
+          CONFIG_PATHS=$(git ls-tree -r --name-only "$RELEASE_TAG" | grep "src/llama_stack/distributions/.*/run.yaml$" || true)
+
+          if [ -z "$CONFIG_PATHS" ]; then
+            echo "::warning::No run.yaml files found in release $RELEASE_TAG"
+            echo "has_configs=false" >> $GITHUB_OUTPUT
+            exit 0
+          fi
+
+          # Extract all configs to a temp directory
+          mkdir -p /tmp/release_configs
+          echo "Extracting configs from release $RELEASE_TAG:"
+
+          while IFS= read -r config_path; do
+            if [ -z "$config_path" ]; then
+              continue
+            fi
+
+            filename=$(basename $(dirname "$config_path"))
+            echo "  - $filename (from $config_path)"
+
+            git show "$RELEASE_TAG:$config_path" > "/tmp/release_configs/${filename}.yaml" 2>/dev/null || true
+          done <<< "$CONFIG_PATHS"
+
+          echo ""
+          echo "Extracted $(ls /tmp/release_configs/*.yaml 2>/dev/null | wc -l) config files"
+          echo "has_configs=true" >> $GITHUB_OUTPUT
+
+      - name: Test against release configs
+        if: steps.get_release.outputs.has_release == 'true' && steps.extract_release_configs.outputs.has_configs == 'true'
+        run: |
+          RELEASE_TAG="${{ steps.get_release.outputs.tag }}"
+
+          # Run pytest with all release configs
+          if COMPAT_TEST_CONFIGS_DIR=/tmp/release_configs uv run pytest tests/backward_compat/test_run_config.py -v --tb=short; then
+            echo "✓ All configs from release $RELEASE_TAG are compatible"
+          else
+            echo "::warning::Some configs from release $RELEASE_TAG are incompatible"
+            echo "::warning::This is informational only - does not block merge"
+          fi
diff --git a/tests/backward_compat/test_run_config.py b/tests/backward_compat/test_run_config.py
new file mode 100644
index 000000000..13aac85e4
--- /dev/null
+++ b/tests/backward_compat/test_run_config.py
@@ -0,0 +1,52 @@
+# Copyright (c) Meta Platforms, Inc. and affiliates.
+# All rights reserved.
+#
+# This source code is licensed under the terms described in the LICENSE file in
+# the root directory of this source tree.
+
+"""
+Backward compatibility test for run.yaml files.
+
+This test ensures that changes to StackRunConfig don't break
+existing run.yaml files from previous versions.
+"""
+
+import os
+from pathlib import Path
+
+import pytest
+import yaml
+
+from llama_stack.core.datatypes import StackRunConfig
+
+
+def get_test_configs():
+    configs_dir = os.environ.get("COMPAT_TEST_CONFIGS_DIR")
+    if configs_dir:
+        # CI mode: test configs extracted from main/release
+        config_dir = Path(configs_dir)
+        if not config_dir.exists():
+            pytest.skip(f"Config directory not found: {configs_dir}")
+
+        config_files = sorted(config_dir.glob("*.yaml"))
+        if not config_files:
+            pytest.skip(f"No .yaml files found in {configs_dir}")
+
+        return config_files
+    else:
+        # Local mode: test current distribution configs
+        repo_root = Path(__file__).parent.parent.parent
+        config_files = sorted((repo_root / "src" / "llama_stack" / "distributions").glob("*/run.yaml"))
+
+        if not config_files:
+            pytest.skip("No run.yaml files found in distributions/")
+
+        return config_files
+
+
+@pytest.mark.parametrize("config_file", get_test_configs(), ids=lambda p: p.stem)
+def test_load_run_config(config_file):
+    with open(config_file) as f:
+        config_data = yaml.safe_load(f)
+
+    StackRunConfig.model_validate(config_data)