diff --git a/.github/workflows/ci.yml b/.github/workflows/ci.yml
new file mode 100644
index 0000000..46cb9ab
--- /dev/null
+++ b/.github/workflows/ci.yml
@@ -0,0 +1,73 @@
+name: CI
+
+on:
+  push:
+    branches: [main]
+  pull_request:
+    branches: [main]
+
+jobs:
+  quality-checks:
+    runs-on: ubuntu-latest
+
+    steps:
+      - name: Checkout code
+        uses: actions/checkout@v4
+
+      - name: Install uv
+        uses: astral-sh/setup-uv@v4
+        with:
+          version: "latest"
+
+      - name: Set up Python
+        uses: actions/setup-python@v5
+        with:
+          python-version: "3.12"
+
+      - name: Install dependencies
+        run: uv sync --all-extras
+
+      - name: Run ruff check
+        run: uv run ruff check src/ tests/
+
+      - name: Run ruff format check
+        run: uv run ruff format --check src/ tests/
+
+      - name: Run mypy type checking
+        run: uv run mypy src/ --strict
+
+      - name: Run tests with coverage
+        run: uv run pytest --cov=src --cov-report=term-missing --cov-report=xml --cov-fail-under=80
+
+      - name: Upload coverage reports
+        uses: codecov/codecov-action@v4
+        if: always()
+        with:
+          file: ./coverage.xml
+          fail_ci_if_error: false
+        env:
+          CODECOV_TOKEN: ${{ secrets.CODECOV_TOKEN }}
+
+  security-audit:
+    runs-on: ubuntu-latest
+
+    steps:
+      - name: Checkout code
+        uses: actions/checkout@v4
+
+      - name: Install uv
+        uses: astral-sh/setup-uv@v4
+        with:
+          version: "latest"
+
+      - name: Set up Python
+        uses: actions/setup-python@v5
+        with:
+          python-version: "3.12"
+
+      - name: Install dependencies
+        run: uv sync --all-extras
+
+      - name: Run pip-audit
+        run: uv run pip-audit
+        continue-on-error: true
diff --git a/tests/test_dependencies.py b/tests/test_dependencies.py
new file mode 100644
index 0000000..b4d6b55
--- /dev/null
+++ b/tests/test_dependencies.py
@@ -0,0 +1,150 @@
+"""Tests for web dependencies (authentication and authorization)."""
+
+from unittest.mock import Mock, patch
+
+import pytest
+from fastapi import Request
+from fastapi.responses import RedirectResponse
+from starlette.exceptions import HTTPException
+
+from src.config import Settings
+from src.web.dependencies import (
+    AuthenticationRequired,
+    auth_exception_handler,
+    get_current_user,
+    require_admin,
+    require_auth,
+)
+
+
+class TestAuthenticationRequired:
+    """Tests for AuthenticationRequired exception."""
+
+    def test_exception_has_correct_status_code(self):
+        """Test AuthenticationRequired sets 303 status code."""
+        exc = AuthenticationRequired()
+        assert exc.status_code == 303
+        assert exc.detail == "Authentication required"
+
+
+class TestGetCurrentUser:
+    """Tests for get_current_user dependency."""
+
+    @patch("src.web.dependencies.get_current_user_from_cookie")
+    def test_get_current_user_returns_user_dict_when_authenticated(self, mock_get_user):
+        """Test get_current_user returns user dict from cookie."""
+        mock_get_user.return_value = {"user_id": "test-id", "email": "test@example.com"}
+        request = Mock(spec=Request)
+
+        result = get_current_user(request)
+
+        assert result is not None
+        assert result["user_id"] == "test-id"
+        mock_get_user.assert_called_once_with(request)
+
+    @patch("src.web.dependencies.get_current_user_from_cookie")
+    def test_get_current_user_returns_none_when_not_authenticated(self, mock_get_user):
+        """Test get_current_user returns None when no session cookie."""
+        mock_get_user.return_value = None
+        request = Mock(spec=Request)
+
+        result = get_current_user(request)
+
+        assert result is None
+        mock_get_user.assert_called_once_with(request)
+
+
+class TestRequireAuth:
+    """Tests for require_auth dependency."""
+
+    def test_require_auth_returns_none_when_auth_disabled(self):
+        """Test require_auth returns None when auth is disabled."""
+        request = Mock(spec=Request)
+        settings = Settings(auth_enabled=False, jwt_secret_key="")
+
+        result = require_auth(request, settings)
+
+        assert result is None
+
+    def test_require_auth_returns_none_when_no_jwt_secret(self):
+        """Test require_auth returns None when JWT secret is not configured."""
+        request = Mock(spec=Request)
+        settings = Settings(auth_enabled=True, jwt_secret_key="")
+
+        result = require_auth(request, settings)
+
+        assert result is None
+
+    @patch("src.web.dependencies.get_current_user_from_cookie")
+    def test_require_auth_returns_user_when_authenticated(self, mock_get_user):
+        """Test require_auth returns user dict when authenticated."""
+        mock_get_user.return_value = {
+            "user_id": "test-id",
+            "email": "test@example.com",
+            "is_admin": False,
+        }
+        request = Mock(spec=Request)
+        settings = Settings(auth_enabled=True, jwt_secret_key="secret-key-123")
+
+        result = require_auth(request, settings)
+
+        assert result is not None
+        assert result["user_id"] == "test-id"
+        mock_get_user.assert_called_once_with(request)
+
+    @patch("src.web.dependencies.get_current_user_from_cookie")
+    def test_require_auth_raises_when_not_authenticated(self, mock_get_user):
+        """Test require_auth raises AuthenticationRequired when not authenticated."""
+        mock_get_user.return_value = None
+        request = Mock(spec=Request)
+        settings = Settings(auth_enabled=True, jwt_secret_key="secret-key-123")
+
+        with pytest.raises(AuthenticationRequired):
+            require_auth(request, settings)
+
+
+class TestRequireAdmin:
+    """Tests for require_admin dependency."""
+
+    def test_require_admin_returns_none_when_auth_disabled(self):
+        """Test require_admin returns None when auth is disabled (user is None)."""
+        result = require_admin(user=None)
+
+        assert result is None
+
+    def test_require_admin_returns_user_when_user_is_admin(self):
+        """Test require_admin returns user dict when user is admin."""
+        user = {"user_id": "admin-id", "email": "admin@example.com", "is_admin": True}
+
+        result = require_admin(user=user)
+
+        assert result is not None
+        assert result["user_id"] == "admin-id"
+        assert result["is_admin"] is True
+
+    def test_require_admin_raises_403_when_user_is_not_admin(self):
+        """Test require_admin raises 403 when user is not admin."""
+        user = {"user_id": "user-id", "email": "user@example.com", "is_admin": False}
+
+        with pytest.raises(HTTPException) as exc_info:
+            require_admin(user=user)
+
+        assert exc_info.value.status_code == 403
+        assert exc_info.value.detail == "Admin access required"
+
+
+class TestAuthExceptionHandler:
+    """Tests for auth_exception_handler."""
+
+    @pytest.mark.asyncio
+    async def test_auth_exception_handler_redirects_to_login(self):
+        """Test auth_exception_handler redirects to login with next parameter."""
+        request = Mock(spec=Request)
+        request.url.path = "/protected/page"
+        exc = AuthenticationRequired()
+
+        response = await auth_exception_handler(request, exc)
+
+        assert isinstance(response, RedirectResponse)
+        assert response.status_code == 303
+        assert response.headers["location"] == "/login?next=/protected/page"
diff --git a/tests/test_moderation.py b/tests/test_moderation.py
new file mode 100644
index 0000000..0641a1f
--- /dev/null
+++ b/tests/test_moderation.py
@@ -0,0 +1,171 @@
+"""Tests for content moderation using OpenAI Moderation API."""
+
+from unittest.mock import AsyncMock, Mock
+
+import httpx
+import pytest
+
+from src.infrastructure.safety.moderation import NoOpModerator, OpenAIModerator
+from src.infrastructure.safety.schemas import ModerationResult
+
+
+class TestOpenAIModeratorInit:
+    """Tests for OpenAIModerator initialization."""
+
+    def test_init_with_valid_api_key(self):
+        """Test initialization with a valid API key."""
+        moderator = OpenAIModerator(api_key="test-key-123")
+        assert moderator._api_key == "test-key-123"
+        assert moderator._timeout == 10.0
+
+    def test_init_with_custom_timeout(self):
+        """Test initialization with custom timeout."""
+        moderator = OpenAIModerator(api_key="test-key", timeout_seconds=5.0)
+        assert moderator._timeout == 5.0
+
+
+class TestOpenAIModeratorCheck:
+    """Tests for OpenAIModerator.check method."""
+
+    @pytest.mark.asyncio
+    async def test_check_returns_safe_result_for_safe_content(self):
+        """Test check returns safe result for non-flagged content."""
+        moderator = OpenAIModerator(api_key="test-key")
+
+        # Mock the HTTP client
+        mock_response = Mock()
+        mock_response.json.return_value = {
+            "results": [
+                {
+                    "flagged": False,
+                    "categories": {"hate": False, "violence": False},
+                    "category_scores": {"hate": 0.1, "violence": 0.05},
+                }
+            ]
+        }
+        moderator._client.post = AsyncMock(return_value=mock_response)
+
+        result = await moderator.check("This is safe content")
+
+        assert isinstance(result, ModerationResult)
+        assert result.flagged is False
+        assert result.categories == {"hate": False, "violence": False}
+
+        await moderator.close()
+
+    @pytest.mark.asyncio
+    async def test_check_returns_flagged_result_for_unsafe_content(self):
+        """Test check returns flagged result for unsafe content."""
+        moderator = OpenAIModerator(api_key="test-key")
+
+        # Mock the HTTP client
+        mock_response = Mock()
+        mock_response.json.return_value = {
+            "results": [
+                {
+                    "flagged": True,
+                    "categories": {"hate": True, "violence": False},
+                    "category_scores": {"hate": 0.9, "violence": 0.1},
+                }
+            ]
+        }
+        moderator._client.post = AsyncMock(return_value=mock_response)
+
+        result = await moderator.check("Unsafe content")
+
+        assert isinstance(result, ModerationResult)
+        assert result.flagged is True
+        assert result.categories["hate"] is True
+
+        await moderator.close()
+
+    @pytest.mark.asyncio
+    async def test_check_handles_timeout_gracefully(self):
+        """Test check returns safe result on timeout (fail open)."""
+        moderator = OpenAIModerator(api_key="test-key")
+
+        # Mock timeout exception
+        moderator._client.post = AsyncMock(
+            side_effect=httpx.TimeoutException("Timeout")
+        )
+
+        result = await moderator.check("Some text")
+
+        # Should fail open (return safe result)
+        assert isinstance(result, ModerationResult)
+        assert result.flagged is False
+        assert result.categories == {}
+
+        await moderator.close()
+
+    @pytest.mark.asyncio
+    async def test_check_handles_http_error_gracefully(self):
+        """Test check returns safe result on HTTP error (fail open)."""
+        moderator = OpenAIModerator(api_key="test-key")
+
+        # Mock HTTP error
+        mock_response = Mock()
+        mock_response.status_code = 500
+        error = httpx.HTTPStatusError(
+            "Server error", request=Mock(), response=mock_response
+        )
+        moderator._client.post = AsyncMock(side_effect=error)
+
+        result = await moderator.check("Some text")
+
+        # Should fail open (return safe result)
+        assert isinstance(result, ModerationResult)
+        assert result.flagged is False
+        assert result.categories == {}
+
+        await moderator.close()
+
+    @pytest.mark.asyncio
+    async def test_check_handles_unexpected_error_gracefully(self):
+        """Test check returns safe result on unexpected error (fail open)."""
+        moderator = OpenAIModerator(api_key="test-key")
+
+        # Mock unexpected exception
+        moderator._client.post = AsyncMock(side_effect=ValueError("Unexpected error"))
+
+        result = await moderator.check("Some text")
+
+        # Should fail open (return safe result)
+        assert isinstance(result, ModerationResult)
+        assert result.flagged is False
+        assert result.categories == {}
+
+        await moderator.close()
+
+    @pytest.mark.asyncio
+    async def test_close_closes_http_client(self):
+        """Test close method closes the HTTP client."""
+        moderator = OpenAIModerator(api_key="test-key")
+        moderator._client.aclose = AsyncMock()
+
+        await moderator.close()
+
+        moderator._client.aclose.assert_called_once()
+
+
+class TestNoOpModerator:
+    """Tests for NoOpModerator."""
+
+    @pytest.mark.asyncio
+    async def test_check_always_returns_safe(self):
+        """Test NoOpModerator always returns safe result."""
+        moderator = NoOpModerator()
+
+        result = await moderator.check("Any text at all")
+
+        assert isinstance(result, ModerationResult)
+        assert result.flagged is False
+        assert result.categories == {}
+
+    @pytest.mark.asyncio
+    async def test_close_does_nothing(self):
+        """Test NoOpModerator close method is a no-op."""
+        moderator = NoOpModerator()
+
+        # Should not raise any exception
+        await moderator.close()