fast-next-template/CLAUDE.md

CLAUDE.md

This file provides guidance to Claude Code (claude.ai/code) when working with code in this repository.

Critical User Preferences

File Operations - NEVER Use Heredoc/Cat Append

ALWAYS use Read/Write/Edit tools instead of cat >> file << EOF commands.

This triggers manual approval dialogs and disrupts workflow.

# WRONG ❌
cat >> file.txt << EOF
content
EOF

# CORRECT ✅ - Use Read, then Write tools

Work Style

• User prefers autonomous operation without frequent interruptions
• Ask for batch permissions upfront for long work sessions
• Work independently, document decisions clearly

Project Architecture

This is a FastAPI + Next.js full-stack application with the following structure:

Backend (FastAPI)

backend/app/
├── api/            # API routes organized by version
│   ├── routes/     # Endpoint implementations (auth, users, sessions, admin, organizations)
│   └── dependencies/ # FastAPI dependencies (auth, permissions)
├── core/           # Core functionality
│   ├── config.py   # Settings (Pydantic BaseSettings)
│   ├── database.py # SQLAlchemy async engine setup
│   ├── auth.py     # JWT token generation/validation
│   └── exceptions.py # Custom exception classes and handlers
├── crud/           # Database CRUD operations (base, user, session, organization)
├── models/         # SQLAlchemy ORM models
├── schemas/        # Pydantic request/response schemas
├── services/       # Business logic layer (auth_service)
└── utils/          # Utilities (security, device detection, test helpers)

Frontend (Next.js 15)

frontend/src/
├── app/            # Next.js App Router pages
├── components/     # React components (auth/, ui/)
├── lib/
│   ├── api/        # API client (auto-generated from OpenAPI)
│   ├── stores/     # Zustand state management
│   └── utils/      # Utility functions
└── hooks/          # Custom React hooks

Development Commands

Backend

Setup

cd backend
python -m venv .venv
source .venv/bin/activate  # or .venv\Scripts\activate on Windows
pip install -r requirements.txt

Database Migrations

# Using the migration helper (preferred)
python migrate.py generate "migration message"  # Generate migration
python migrate.py apply                         # Apply migrations
python migrate.py auto "message"                # Generate and apply in one step
python migrate.py list                          # List all migrations
python migrate.py current                       # Show current revision
python migrate.py check                         # Check DB connection

# Or using Alembic directly
alembic revision --autogenerate -m "message"
alembic upgrade head

Testing

Test Coverage: High (comprehensive test suite)

• Security-focused testing with JWT algorithm attack prevention (CVE-2015-9235)
• Session hijacking and privilege escalation tests included
• Missing lines justified as defensive code, error handlers, and production-only code

# Run all tests (uses pytest-xdist for parallel execution)
IS_TEST=True pytest

# Run with coverage (use -n 0 for accurate coverage)
IS_TEST=True pytest --cov=app --cov-report=term-missing -n 0

# Run specific test file
IS_TEST=True pytest tests/api/test_auth.py -v

# Run single test
IS_TEST=True pytest tests/api/test_auth.py::TestLogin::test_login_success -v

# Run with HTML coverage report
IS_TEST=True pytest --cov=app --cov-report=html -n 0
open htmlcov/index.html

Running Locally

cd backend
source .venv/bin/activate
uvicorn app.main:app --reload --host 0.0.0.0 --port 8000

Frontend

Setup

cd frontend
npm install

Development

npm run dev          # Start dev server on http://localhost:3000
npm run build        # Production build
npm run lint         # ESLint
npm run type-check   # TypeScript checking

Testing

# Unit tests (Jest)
npm test                    # Run all unit tests
npm run test:watch          # Watch mode
npm run test:coverage       # With coverage

# E2E tests (Playwright)
npm run test:e2e            # Run all E2E tests
npm run test:e2e:ui         # Open Playwright UI
npm run test:e2e:debug      # Debug mode
npx playwright test auth-login.spec.ts  # Run specific file

E2E Test Best Practices:

• Use Promise.all() pattern for Next.js Link navigation:

  await Promise.all([
    page.waitForURL('/target', { timeout: 10000 }),
    link.click()
  ]);
  

• Use ID-based selectors for validation errors (e.g., #email-error)
• Error IDs use dashes not underscores (#new-password-error)
• Target .border-destructive[role="alert"] to avoid Next.js route announcer conflicts
• Uses 12 workers in non-CI mode (workers: 12 in playwright.config.ts)
• URL assertions should use regex to handle query params: /\/auth\/login/

Docker

# Development (with hot reload)
docker-compose -f docker-compose.dev.yml up

# Production
docker-compose up -d

# Rebuild specific service
docker-compose build backend
docker-compose build frontend

Key Architectural Patterns

Authentication Flow

1. Login: POST /api/v1/auth/login returns access + refresh tokens

   • Access token: 15 minutes expiry (JWT)
   • Refresh token: 7 days expiry (JWT with JTI stored in DB)
   • Session tracking with device info (IP, user agent, device ID)

2. Token Refresh: POST /api/v1/auth/refresh validates refresh token JTI

   • Checks session is active in database
   • Issues new access token (refresh token remains valid)
   • Updates session last_used_at

3. Authorization: FastAPI dependencies in api/dependencies/auth.py

   • get_current_user: Validates access token, returns User (raises 401 if invalid)
   • get_current_active_user: Requires valid access token + active account
   • get_optional_current_user: Accepts both authenticated and anonymous users (returns User or None)
   • get_current_superuser: Requires superuser flag

Database Pattern: Async SQLAlchemy

• Engine: Created in core/database.py with connection pooling
• Sessions: AsyncSession from async_sessionmaker
• CRUD: Base class in crud/base.py with common operations
  • Inherits: CRUDUser, CRUDSession, CRUDOrganization
  • Pattern: async def get(db: AsyncSession, id: str) -> Model | None

Frontend State Management

• Zustand stores: lib/stores/ (authStore, etc.)
• TanStack Query: API data fetching/caching
• Auto-generated client: lib/api/generated/ from OpenAPI spec
  • Generate with: npm run generate:api (runs scripts/generate-api-client.sh)

🔴 CRITICAL: Auth Store Dependency Injection Pattern

ALWAYS use useAuth() from AuthContext, NEVER import useAuthStore directly!

// ❌ WRONG - Bypasses dependency injection
import { useAuthStore } from '@/lib/stores/authStore';
const { user, isAuthenticated } = useAuthStore();

// ✅ CORRECT - Uses dependency injection
import { useAuth } from '@/lib/auth/AuthContext';
const { user, isAuthenticated } = useAuth();

Why This Matters:

• E2E tests inject mock stores via window.__TEST_AUTH_STORE__
• Unit tests inject via <AuthProvider store={mockStore}>
• Direct useAuthStore imports bypass this injection → tests fail
• ESLint will catch violations (added Nov 2025)

Exceptions:

1. AuthContext.tsx - DI boundary, legitimately needs real store
2. client.ts - Non-React context, uses dynamic import + __TEST_AUTH_STORE__ check

See: frontend/docs/ARCHITECTURE_FIX_REPORT.md for full details.

Session Management Architecture

Database-backed session tracking (not just JWT):

• Each refresh token has a corresponding UserSession record
• Tracks: device info, IP, location, last used timestamp
• Supports session revocation (logout from specific devices)
• Cleanup job removes expired sessions

Permission System

Three-tier organization roles:

• Owner: Full control (delete org, manage all members)
• Admin: Can add/remove members, assign admin role (not owner)
• Member: Read-only organization access

Dependencies in api/dependencies/permissions.py:

• require_organization_owner
• require_organization_admin
• require_organization_member
• can_manage_organization_member (owner or admin, but not self-demotion)

Testing Infrastructure

Backend Test Patterns

Fixtures (in tests/conftest.py):

• async_test_db: Fresh SQLite in-memory database per test
• client: AsyncClient with test database override
• async_test_user: Pre-created regular user
• async_test_superuser: Pre-created superuser
• user_token / superuser_token: Access tokens for API calls

Database Mocking for Exception Testing:

from unittest.mock import patch, AsyncMock

# Mock database commit to raise exception
async def mock_commit():
    raise OperationalError("Connection lost", {}, Exception())

with patch.object(session, 'commit', side_effect=mock_commit):
    with patch.object(session, 'rollback', new_callable=AsyncMock) as mock_rollback:
        with pytest.raises(OperationalError):
            await crud_method(session, obj_in=data)
        mock_rollback.assert_called_once()

Testing Routes:

@pytest.mark.asyncio
async def test_endpoint(client, user_token):
    response = await client.get(
        "/api/v1/endpoint",
        headers={"Authorization": f"Bearer {user_token}"}
    )
    assert response.status_code == 200

IMPORTANT: Use @pytest_asyncio.fixture for async fixtures, not @pytest.fixture

Frontend Test Patterns

Unit Tests (Jest):

// SSR-safe mocking
jest.mock('@/lib/stores/authStore', () => ({
  useAuthStore: jest.fn()
}));

beforeEach(() => {
  (useAuthStore as jest.Mock).mockReturnValue({
    user: mockUser,
    login: mockLogin
  });
});

E2E Tests (Playwright):

test('navigation', async ({ page }) => {
  await page.goto('/');

  const link = page.getByRole('link', { name: 'Login' });
  await Promise.all([
    page.waitForURL(/\/auth\/login/, { timeout: 10000 }),
    link.click()
  ]);

  await expect(page).toHaveURL(/\/auth\/login/);
});

Configuration

Environment Variables

Backend (.env):

# Database
POSTGRES_USER=postgres
POSTGRES_PASSWORD=your_password
POSTGRES_HOST=db
POSTGRES_PORT=5432
POSTGRES_DB=app

# Security
SECRET_KEY=your-secret-key-min-32-chars
ENVIRONMENT=development|production
CSP_MODE=relaxed|strict|disabled

# First Superuser (auto-created on init)
FIRST_SUPERUSER_EMAIL=admin@example.com
FIRST_SUPERUSER_PASSWORD=admin123

# CORS
BACKEND_CORS_ORIGINS=["http://localhost:3000"]

Frontend (.env.local):

NEXT_PUBLIC_API_URL=http://localhost:8000/api/v1

Database Connection Pooling

Configured in core/config.py:

• db_pool_size: 20 (default connections)
• db_max_overflow: 50 (max overflow)
• db_pool_timeout: 30 seconds
• db_pool_recycle: 3600 seconds (recycle after 1 hour)

Security Headers

Automatically applied via middleware in main.py:

• X-Frame-Options: DENY
• X-Content-Type-Options: nosniff
• X-XSS-Protection: 1; mode=block
• Strict-Transport-Security (production only)
• Content-Security-Policy (configurable via CSP_MODE)

Rate Limiting

• Implemented with slowapi
• Default: 60 requests/minute per IP
• Applied to auth endpoints (login, register, password reset)
• Override in route decorators: @limiter.limit("10/minute")

Common Workflows

Adding a New API Endpoint

1. Create schema (backend/app/schemas/):

   class ItemCreate(BaseModel):
       name: str
       description: Optional[str] = None
   
   class ItemResponse(BaseModel):
       id: UUID
       name: str
       created_at: datetime
   

2. Create CRUD operations (backend/app/crud/):

   class CRUDItem(CRUDBase[Item, ItemCreate, ItemUpdate]):
       async def get_by_name(self, db: AsyncSession, name: str) -> Item | None:
           result = await db.execute(select(Item).where(Item.name == name))
           return result.scalar_one_or_none()
   
   item = CRUDItem(Item)
   

3. Create route (backend/app/api/routes/items.py):

   from app.api.dependencies.auth import get_current_user
   
   @router.post("/", response_model=ItemResponse)
   async def create_item(
       item_in: ItemCreate,
       current_user: User = Depends(get_current_user),
       db: AsyncSession = Depends(get_db)
   ):
       item = await item_crud.create(db, obj_in=item_in)
       return item
   

4. Register router (backend/app/api/main.py):

   from app.api.routes import items
   api_router.include_router(items.router, prefix="/items", tags=["Items"])
   

5. Write tests (backend/tests/api/test_items.py):

   @pytest.mark.asyncio
   async def test_create_item(client, user_token):
       response = await client.post(
           "/api/v1/items",
           headers={"Authorization": f"Bearer {user_token}"},
           json={"name": "Test Item"}
       )
       assert response.status_code == 201
   

6. Generate frontend client:

   cd frontend
   npm run generate:api
   

Adding a New React Component

1. Create component (frontend/src/components/):

   export function MyComponent() {
     const { user } = useAuthStore();
     return <div>Hello {user?.firstName}</div>;
   }
   

2. Add tests (frontend/src/components/__tests__/):

   import { render, screen } from '@testing-library/react';
   
   test('renders component', () => {
     render(<MyComponent />);
     expect(screen.getByText(/Hello/)).toBeInTheDocument();
   });
   

3. Add to page (frontend/src/app/page.tsx):

   import { MyComponent } from '@/components/MyComponent';
   
   export default function Page() {
     return <MyComponent />;
   }
   

Current Project Status (Nov 2025)

Completed Features

• ✅ Authentication system (JWT with refresh tokens)
• ✅ Session management (device tracking, revocation)
• ✅ User management (CRUD, password change)
• ✅ Organization system (multi-tenant with roles)
• ✅ Admin panel (user/org management, bulk operations)
• ✅ E2E test suite (86 tests, 100% pass rate, zero flaky tests)

Test Coverage

• Backend: 97% overall (743 tests, all passing) ✅

  • Comprehensive security testing (JWT attacks, session hijacking, privilege escalation)
  • User CRUD: 100% ✅
  • Session CRUD: 100% ✅
  • Auth routes: 99% ✅
  • Organization routes: 100% ✅
  • Permissions: 100% ✅
  • 84 missing lines justified (defensive code, error handlers, production-only code)

• Frontend E2E: 86 tests across 4 files (100% pass rate, zero flaky tests) ✅

  • auth-login.spec.ts
  • auth-register.spec.ts
  • auth-password-reset.spec.ts
  • navigation.spec.ts

Email Service Integration

The project includes a placeholder email service (backend/app/services/email_service.py) designed for easy integration with production email providers.

Current Implementation

Console Backend (Default):

• Logs email content to console/logs instead of sending
• Safe for development and testing
• No external dependencies required

Production Integration

To enable email functionality, implement one of these approaches:

Option 1: SMTP Integration (Recommended for most use cases)

# In app/services/email_service.py, complete the SMTPEmailBackend implementation
from aiosmtplib import SMTP
from email.mime.text import MIMEText
from email.mime.multipart import MIMEMultipart

# Add environment variables to .env:
# SMTP_HOST=smtp.gmail.com
# SMTP_PORT=587
# SMTP_USERNAME=your-email@gmail.com
# SMTP_PASSWORD=your-app-password

Option 2: Third-Party Service (SendGrid, AWS SES, Mailgun, etc.)

# Create a new backend class, e.g., SendGridEmailBackend
class SendGridEmailBackend(EmailBackend):
    def __init__(self, api_key: str):
        self.api_key = api_key
        self.client = sendgrid.SendGridAPIClient(api_key)

    async def send_email(self, to, subject, html_content, text_content=None):
        # Implement SendGrid sending logic
        pass

# Update global instance in email_service.py:
# email_service = EmailService(SendGridEmailBackend(settings.SENDGRID_API_KEY))

Option 3: External Microservice

• Use a dedicated email microservice via HTTP API
• Implement HTTPEmailBackend that makes async HTTP requests

Email Templates Included

The service includes pre-built templates for:

• Password Reset: send_password_reset_email() - 1 hour expiry
• Email Verification: send_email_verification() - 24 hour expiry

Both include responsive HTML and plain text versions.

Integration Points

Email sending is called from:

• app/api/routes/auth.py - Password reset flow (placeholder comments)
• Registration flow - Ready for email verification integration

Note: Current auth routes have placeholder comments where email functionality should be integrated. Search for "TODO: Send email" in the codebase.

API Documentation

Once backend is running:

• Swagger UI: http://localhost:8000/docs
• ReDoc: http://localhost:8000/redoc
• OpenAPI JSON: http://localhost:8000/api/v1/openapi.json

Troubleshooting

Tests failing with "Module was never imported"

Run with single process: pytest -n 0

Coverage not improving despite new tests

• Verify tests actually execute endpoints (check response.status_code)
• Generate HTML coverage: pytest --cov=app --cov-report=html -n 0
• Check for dependency override issues in test fixtures

Frontend type errors

npm run type-check          # Check all types
npx tsc --noEmit           # Same but shorter

E2E tests flaking

• Check worker count (should be 4, not 16+)
• Use Promise.all() for navigation
• Use regex for URL assertions
• Target specific selectors (avoid generic [role="alert"])

Database migration conflicts

python migrate.py list      # Check migration history
alembic downgrade -1        # Downgrade one revision
alembic upgrade head        # Re-apply

Additional Documentation

Backend Documentation

• backend/docs/ARCHITECTURE.md: System architecture and design patterns
• backend/docs/CODING_STANDARDS.md: Code quality standards and best practices
• backend/docs/COMMON_PITFALLS.md: Common mistakes and how to avoid them
• backend/docs/FEATURE_EXAMPLE.md: Step-by-step feature implementation guide

Frontend Documentation

• frontend/docs/ARCHITECTURE_FIX_REPORT.md: ⭐ Critical DI pattern fixes (READ THIS!)
• frontend/e2e/README.md: E2E testing setup and guidelines
• frontend/docs/design-system/: Comprehensive design system documentation
  • README.md: Hub with learning paths (start here)
  • 00-quick-start.md: 5-minute crash course
  • 01-foundations.md: Colors (OKLCH), typography, spacing, shadows
  • 02-components.md: shadcn/ui component library guide
  • 03-layouts.md: Layout patterns (Grid vs Flex decision trees)
  • 04-spacing-philosophy.md: Parent-controlled spacing strategy
  • 05-component-creation.md: When to create vs compose components
  • 06-forms.md: Form patterns with react-hook-form + Zod
  • 07-accessibility.md: WCAG AA compliance, keyboard navigation, screen readers
  • 08-ai-guidelines.md: AI code generation rules (read this!)
  • 99-reference.md: Quick reference cheat sheet (bookmark this)