Flutter Development

Architecture

/lib/features/[feature]
├── /data
│   ├── /datasources      # API, local storage
│   ├── /models           # JSON serialization
│   └── /repositories     # Implementation
├── /domain
│   ├── /entities         # Business objects
│   ├── /repositories     # Interfaces
│   └── /usecases         # Business logic
└── /presentation
    ├── /bloc             # State management
    ├── /pages            # Screens
    └── /widgets          # UI components

BLoC Pattern

// Events
abstract class AuthEvent {}
class LoginRequested extends AuthEvent {
  final String email, password;
  LoginRequested(this.email, this.password);
}

// States
abstract class AuthState {}
class AuthInitial extends AuthState {}
class AuthLoading extends AuthState {}
class AuthSuccess extends AuthState { AuthSuccess(this.user); final User user; }
class AuthFailure extends AuthState { AuthFailure(this.error); final String error; }

// BLoC
class AuthBloc extends Bloc<AuthEvent, AuthState> {
  final AuthRepository _repository;

  AuthBloc(this._repository) : super(AuthInitial()) {
    on<LoginRequested>(_onLogin);
  }

  Future<void> _onLogin(LoginRequested event, Emitter<AuthState> emit) async {
    emit(AuthLoading());
    try {
      emit(AuthSuccess(await _repository.login(event.email, event.password)));
    } catch (e) {
      emit(AuthFailure(e.toString()));
    }
  }
}

Widgets

• Stateless for pure UI
• Stateful only if local state is needed
• const constructors when possible
• Composition over inheritance

Tests

// Widget test
testWidgets('shows button', (tester) async {
  await tester.pumpWidget(MaterialApp(home: MyWidget()));
  expect(find.byType(ElevatedButton), findsOneWidget);
});

// BLoC test
blocTest<AuthBloc, AuthState>(
  'emits [Loading, Success] on login',
  build: () => AuthBloc(FakeAuthRepository()),
  act: (bloc) => bloc.add(LoginRequested('email', 'pass')),
  // states have no == (no Equatable): match them by type
  expect: () => [isA<AuthLoading>(), isA<AuthSuccess>()],
);

See also

This skill holds the foundation's architecture opinion (Clean Architecture + BLoC). For the framework itself, the Flutter team publishes its own skills at flutter/agent-plugins (BSD-3-Clause): layouts and layout fixes, declarative routing, HTTP, JSON serialization, widget and integration tests, localization, plus 15 Dart skills. Its plugin also starts the Dart SDK's own MCP server (dart mcp-server, local).

• Architecture differs: the official flutter-apply-architecture-best-practices teaches MVVM with ChangeNotifier. A project that already chose BLoC keeps it: follow the project's established pattern, use the official skills for the framework APIs (layout, routing, HTTP, JSON, tests).
• Deeper BLoC: HoangNguyen0403/agent-skills-standard — skills/flutter/flutter-bloc-state-management and flutter-feature-based-clean-architecture (MIT, community, 569★), pinned at commit 1fb0537c339c. Link those two folders only: they hold nothing but their references/; the repo's hooks, agents and MCP config are for its own development.