---

name: generic-fullstack-feature-developer description: Guide feature development for full-stack applications with architecture focus. Covers Next.js App Router patterns, NestJS backend services, database models, data workflows, and seamless integration. Use when adding new features, refactoring existing code, or planning major changes.

Fullstack Feature Developer

Guide feature development for Next.js/NestJS full-stack applications.

Extends: Generic Feature Developer - Read base skill for development workflow, decision frameworks, data flow patterns, and error handling.

Full-Stack Data Flow

CopyUser Action → Event Handler → API Call → NestJS Controller
                                              ↓
UI Update ← Response ← Service ← Prisma ← Database

Request/Response Cycle

Copy// Frontend: Call API
const response = await fetch('/api/users', {
  method: 'POST',
  body: JSON.stringify(userData),
});

// Backend: Handle request
@Post()
@UseGuards(JwtAuthGuard)
async createUser(@Body() dto: CreateUserDto) {
  return this.userService.create(dto);
}

Next.js App Router Patterns

File Conventions

Server vs Client Components

Copy// Server Component (default) - can fetch data
export default async function Page() {
  const data = await getData(); // Direct DB/API call
  return <div>{data.title}</div>;
}

// Client Component - needs 'use client'
'use client';
export default function Interactive() {
  const [state, setState] = useState();
  return <button onClick={() => setState(...)}>Click</button>;
}

NestJS Module Pattern

CopyModule → Controller → Service → Prisma

Adding a Feature Module

Copy// 1. Module definition
@Module({
  controllers: [UsersController],
  providers: [UsersService],
  exports: [UsersService],
})
export class UsersModule {}

// 2. Controller with guards
@Controller("users")
@UseGuards(JwtAuthGuard)
export class UsersController {
  @Post()
  create(@Body() dto: CreateUserDto) {
    return this.usersService.create(dto);
  }
}

// 3. Service with Prisma
@Injectable()
export class UsersService {
  constructor(private prisma: PrismaService) {}

  create(dto: CreateUserDto) {
    return this.prisma.user.create({ data: dto });
  }
}

Prisma Workflow

Schema Changes

Copy# 1. Edit schema.prisma
# 2. Create migration
npx prisma migrate dev --name add_user_role

# 3. Regenerate client
npx prisma generate

# 4. Update services to use new fields

Type-Safe Queries

Copy// ✓ Type-safe with generated types
const user = await this.prisma.user.findUnique({
  where: { id },
  include: { posts: true },
});

// ✗ Avoid raw SQL
await this.prisma.$queryRaw`SELECT * FROM users`; // No type safety

Authentication Flow

CopyLogin Request → Validate Credentials → Generate JWT → Set Cookie
      ↓
Protected Route → JwtAuthGuard → Extract User → Inject to Controller

Auth Integration Points

Copy// Frontend: Include credentials
fetch('/api/protected', { credentials: 'include' });

// Backend: Guard + decorator
@UseGuards(JwtAuthGuard)
@Get('profile')
getProfile(@CurrentUser() user: User) {
  return user;
}

Feature Checklist (Fullstack)

Before Starting

• Plan data model (Prisma schema)
• Define API contract (DTOs)
• Identify auth requirements

During Development

• Create/update Prisma schema
• Run migrations
• Implement NestJS module (controller + service)
• Create frontend components
• Add loading/error states

Before Completion

• Add DTO validation decorators
• Write backend unit tests
• Write E2E tests for API
• Verify TypeScript types match

See Also

• Generic Feature Developer - Base methodology
• Code Review Standards - Quality requirements
• Design Patterns - UI patterns