diff --git a/.github/workflows/ci.yml b/.github/workflows/ci.yml
index c93f004..ed6182d 100644
--- a/.github/workflows/ci.yml
+++ b/.github/workflows/ci.yml
@@ -15,12 +15,12 @@ concurrency:
   cancel-in-progress: true
 
 jobs:
-  ci:
+  tests:
     runs-on: ubuntu-latest
     strategy:
       fail-fast: false
       matrix:
-        python-version: [ "3.11", "3.12" ]
+        python-version: [ "3.10", "3.11", "3.12" ]
 
     steps:
       - name: Checkout
@@ -46,3 +46,54 @@ jobs:
       - name: Tests (pytest)
         run: |
           pytest -q
+
+  protected-file-guard:
+    runs-on: ubuntu-latest
+    if: github.event_name == 'pull_request'
+    steps:
+      - name: Checkout
+        uses: actions/checkout@v4
+        with:
+          fetch-depth: 0
+
+      - name: Fail if protected paths are modified
+        run: |
+          PROTECTED_PATHS=(
+            "authority_gate.py"
+            "stop_machine.py"
+            "commit_gate/"
+            ".github/workflows/"
+          )
+          CHANGED=$(git diff --name-only origin/${{ github.base_ref }}..HEAD)
+          VIOLATIONS=""
+          for path in "${PROTECTED_PATHS[@]}"; do
+            if echo "$CHANGED" | grep -q "^${path}"; then
+              VIOLATIONS="${VIOLATIONS}\n  - ${path}"
+            fi
+          done
+          if [ -n "$VIOLATIONS" ]; then
+            echo "::error::Protected paths modified — triple-lock review required:${VIOLATIONS}"
+            exit 1
+          fi
+          echo "No protected paths modified."
+
+  build-artefact:
+    runs-on: ubuntu-latest
+    needs: tests
+    if: github.ref == 'refs/heads/main' && github.event_name == 'push'
+    steps:
+      - name: Checkout
+        uses: actions/checkout@v4
+
+      - name: Build source artefact
+        run: |
+          zip -r constraint-workshop-${{ github.sha }}.zip \
+            authority_gate.py stop_machine.py mgtp/ commit_gate/ registry/ \
+            --exclude "*/__pycache__/*" --exclude "*/.git/*"
+
+      - name: Upload artefact
+        uses: actions/upload-artifact@v4
+        with:
+          name: constraint-workshop-${{ github.sha }}
+          path: constraint-workshop-${{ github.sha }}.zip
+          retention-days: 90
diff --git a/.github/workflows/release.yml b/.github/workflows/release.yml
new file mode 100644
index 0000000..ec7949a
--- /dev/null
+++ b/.github/workflows/release.yml
@@ -0,0 +1,92 @@
+name: Release
+
+on:
+  push:
+    tags:
+      - "v[0-9]*.[0-9]*.[0-9]*"
+
+permissions:
+  contents: write
+
+jobs:
+  verify-protected-branch:
+    runs-on: ubuntu-latest
+    steps:
+      - name: Checkout
+        uses: actions/checkout@v4
+        with:
+          fetch-depth: 0
+
+      - name: Verify tag is reachable from main
+        run: |
+          git fetch origin main
+          TAG_SHA=$(git rev-parse HEAD)
+          if ! git merge-base --is-ancestor "$TAG_SHA" "origin/main"; then
+            echo "::error::Tag ${{ github.ref_name }} (${TAG_SHA}) is not on the protected main branch."
+            exit 1
+          fi
+          echo "Tag ${TAG_SHA} is on main. Proceeding."
+
+  tests:
+    runs-on: ubuntu-latest
+    needs: verify-protected-branch
+    strategy:
+      fail-fast: false
+      matrix:
+        python-version: [ "3.10", "3.11", "3.12" ]
+    steps:
+      - name: Checkout
+        uses: actions/checkout@v4
+
+      - name: Set up Python ${{ matrix.python-version }}
+        uses: actions/setup-python@v5
+        with:
+          python-version: ${{ matrix.python-version }}
+
+      - name: Install dependencies
+        run: |
+          python -m pip install --upgrade pip
+          pip install ruff pytest
+
+      - name: Lint (ruff)
+        run: ruff check .
+
+      - name: Tests (pytest)
+        run: pytest -q
+
+  build-release-artefact:
+    runs-on: ubuntu-latest
+    needs: tests
+    steps:
+      - name: Checkout
+        uses: actions/checkout@v4
+
+      - name: Record commit SHA
+        id: meta
+        run: |
+          echo "sha=$(git rev-parse HEAD)" >> "$GITHUB_OUTPUT"
+          echo "tag=${{ github.ref_name }}" >> "$GITHUB_OUTPUT"
+
+      - name: Build release artefact
+        run: |
+          zip -r constraint-workshop-${{ github.ref_name }}.zip \
+            authority_gate.py stop_machine.py mgtp/ commit_gate/ registry/ \
+            --exclude "*/__pycache__/*" --exclude "*/.git/*"
+          sha256sum constraint-workshop-${{ github.ref_name }}.zip \
+            > constraint-workshop-${{ github.ref_name }}.zip.sha256
+
+      - name: Create GitHub Release
+        uses: softprops/action-gh-release@v2
+        with:
+          tag_name: ${{ github.ref_name }}
+          name: "Release ${{ github.ref_name }}"
+          body: |
+            ## Release ${{ github.ref_name }}
+
+            **Commit SHA:** `${{ steps.meta.outputs.sha }}`
+            **Branch:** `main` (verified)
+
+            All CI checks (Python 3.10, 3.11, 3.12) passed before this release was built.
+          files: |
+            constraint-workshop-${{ github.ref_name }}.zip
+            constraint-workshop-${{ github.ref_name }}.zip.sha256