diff --git a/.github/workflows/ci.yml b/.github/workflows/ci.yml
new file mode 100644
index 00000000..ae98b897
--- /dev/null
+++ b/.github/workflows/ci.yml
@@ -0,0 +1,57 @@
+name: CI
+
+on:
+  push:
+    branches: [main]
+  pull_request:
+    branches: [main]
+
+jobs:
+  backend:
+    name: Backend Tests
+    runs-on: ubuntu-latest
+
+    steps:
+      - uses: actions/checkout@v4
+
+      - name: Set up Python 3.12
+        uses: actions/setup-python@v5
+        with:
+          python-version: "3.12"
+
+      - name: Install dependencies
+        run: |
+          # Install backend deps EXCEPT cloakbrowser (custom binary not available in CI).
+          # The conftest.py mocks cloakbrowser via sys.modules before any import.
+          grep -v '^cloakbrowser' backend/requirements.txt > /tmp/ci-requirements.txt
+          pip install -r /tmp/ci-requirements.txt
+          pip install pytest pytest-asyncio starlette
+
+      - name: Run tests
+        run: python -m pytest backend/tests/ -v
+
+  frontend:
+    name: Frontend Tests
+    runs-on: ubuntu-latest
+
+    steps:
+      - uses: actions/checkout@v4
+
+      - name: Set up Node 20
+        uses: actions/setup-node@v4
+        with:
+          node-version: "20"
+          cache: npm
+          cache-dependency-path: frontend/package-lock.json
+
+      - name: Install dependencies
+        working-directory: frontend
+        run: npm ci
+
+      - name: Build
+        working-directory: frontend
+        run: npm run build
+
+      - name: Run tests
+        working-directory: frontend
+        run: npm test