Flutter Mobile

Iron Law

NO FLUTTER UI WITHOUT RUNNING THE MFRI RISK SCORE FIRST — load reference/mfri-scoring.md before writing any screen

Flutter Mobile Development Skill

Code Conventions

• Use Riverpod for state management
• Follow feature-first folder structure: lib/features/<feature>/
• Separate data/, domain/, presentation/ layers (clean architecture)
• Use freezed for immutable models
• Firebase integration via firebase_core, cloud_firestore, firebase_auth

Quick Scaffold

flutter create --org com.company --platforms ios,android my_app
cd my_app

# Add core dependencies
flutter pub add flutter_riverpod riverpod_annotation
flutter pub add freezed_annotation json_annotation go_router firebase_core cloud_firestore firebase_auth
flutter pub add dio
flutter pub add dev:riverpod_generator dev:freezed dev:json_serializable dev:build_runner dev:mocktail

# Run code generation
dart run build_runner build --delete-conflicting-outputs

Melos Workspace Commands

In a Melos monorepo, use these commands at the workspace root:

• melos bootstrap — installs all Flutter workspace dependencies (run at root, NOT flutter pub get)
• melos run test — runs tests across all packages
• melos run build_runner — runs code generation across all packages

Shared Packages (monorepo pattern)

In a Melos workspace, individual apps reference shared packages by path rather than publishing them. Example:

dependencies:
  <shared_ui_package>:
    path: ../../packages/<shared_ui_package>
  <shared_core_package>:
    path: ../../packages/<shared_core_package>

Do NOT create a lib/design_system/ directory in individual apps — shared UI components belong in the workspace's shared UI package.

Dio HTTP Client (monorepo pattern)

In a Melos workspace, place the shared Dio instance with auth + retry interceptors in the shared core package's providers directory. Do NOT create new Dio instances in individual features.

Before Writing Any UI Code

Before creating or modifying any widget, screen, or visual component:

1. Run MFRI scoring — read reference/mfri-scoring.md and complete the checkpoint template. Score < 3 = stop and redesign. Score 3-5 = add a validation milestone.
2. Load ui-standards-tokens skill — read reference/ui-design-tokens.md for spacing, color, typography, radius tokens
3. Verify token awareness — can you name the spacing token (AppSpacing.md), color approach (Theme.of(context).colorScheme), and typography pattern (Theme.of(context).textTheme) you will use?
4. If not → read the reference file before writing any widget code
5. For accessibility: read reference/ui-accessibility-patterns.md before adding interactive elements

Process

1. Read templates - Use Read tool on reference/flutter-templates.md for all code templates (Freezed models, Riverpod providers, screens, GoRouter, tests, Firebase integration)
2. Create feature structure - Build lib/features/<feature>/data/, domain/, presentation/ directories
3. Define models - Create Freezed data models in data/models/ with Firestore serialization
4. Build providers - Create Riverpod notifiers with @riverpod annotation in presentation/providers/
5. Design screens - Build ConsumerWidget screens that watch AsyncValue<T> providers
6. Run codegen - Execute dart run build_runner build --delete-conflicting-outputs
7. Write tests - Create widget tests with ProviderScope overrides

Key Patterns

Modern Flutter Architecture (2025/2026)

For architecture patterns, accessibility, performance, UX, and premium polish guidelines:

Read reference/flutter-architecture-patterns.md — Sealed classes, Result types, Riverpod AsyncNotifier Read reference/flutter-performance-ux.md — Accessibility, performance, haptic feedback, shimmer, animations Read reference/flutter-design-polish.md — Glassmorphism, premium cards, dark/light themes, gradients Read reference/accessibility-audit-checklist.md — WCAG 2.1 audit checklist (used by accessibility-auditor agent) Read reference/flutter-security-hardening.md — Security hardening & privacy compliance (used by flutter-security-expert agent) Read reference/smart-dumb-widgets.md — Smart (ConsumerWidget) vs Dumb (StatelessWidget) pattern, ref.watch/read placement rules, decision tree, Riverpod enforcement gates Read reference/flutter-use-case-layer.md — When to add a use case, when not to, file location, example with two repositories, unit testing with fakes

Documentation Sources

Before generating code, consult these sources for current syntax and APIs:

iOS Build, Run & Debug (XcodeBuildMCP)

For iOS-specific workflows, use the xcodebuild MCP server instead of raw CLI commands. It provides structured output, error parsing, and debugging that flutter build ios via Bash cannot.

When to Use Which

iOS Debug Workflow

1. discover_projs → find ios/Runner.xcworkspace
2. list_schemes → identify the Runner scheme
3. build_run_sim → build, install, and launch on simulator
4. start_sim_log_cap → begin capturing logs
5. [reproduce the issue]
6. debug_attach_sim → attach LLDB debugger
7. debug_breakpoint_add → set breakpoint at suspect line
8. debug_variables / debug_stack → inspect state
9. stop_sim_log_cap → get captured logs

Gotchas

• Flutter projects: The Xcode project is at ios/Runner.xcworkspace, not the project root
• First build: Run flutter build ios once first to generate the Xcode project and Pods
• Signing: show_build_settings exposes signing config — use this to diagnose code signing failures
• Scheme name: Flutter apps use the Runner scheme by default

E2E Testing (Maestro MCP)

For cross-platform E2E testing, use the maestro MCP server. It runs test flows on both iOS simulator and Android emulator from natural language prompts.

When to Use Which Test Tool

E2E Workflow

1. Build and launch app (XcodeBuildMCP for iOS, flutter run for Android)
2. Describe the test flow in natural language
3. Claude generates YAML via Maestro MCP and runs it
4. Claude reports pass/fail per step
5. Save generated YAML to test/e2e/<flow-name>.yaml for reuse

Flow File Conventions

• Save flows to test/e2e/ at the project root
• Name files by user journey: login-flow.yaml, create-workout-flow.yaml
• Use appId matching your app's bundle ID
• One flow per file — keep flows focused on a single journey

Gotchas

• App must be running: Maestro interacts with a live app — build and launch first
• Accessibility labels: Maestro finds elements by text and accessibility labels — ensure Semantics widgets have labels
• Timing: Use waitForAnimationToEnd or extendedWaitUntil for slow transitions, not hardcoded sleeps
• Cross-platform element names: iOS and Android may render text differently — use id attributes for reliable cross-platform selectors

Common Commands

flutter run                          # Run on connected device/emulator
flutter test                         # Run tests
flutter build apk                    # Build Android APK
flutter build ios                    # Build iOS (also generates Xcode project)
flutter pub get                      # Install dependencies
flutter clean                        # Clean build artifacts
dart run build_runner build --delete-conflicting-outputs  # Run code generation
flutter analyze                      # Static analysis

Error Handling

Build runner fails: Delete .dart_tool/build/, run flutter clean, retry codegen

Missing generated files: Ensure part directives match filename (e.g., part 'user_model.g.dart';)

Provider not found: Run dart run build_runner build, import generated .g.dart file

Firestore Timestamp errors: Use (data['createdAt'] as Timestamp).toDate() in fromFirestore

Hot reload breaks state: Restart app fully when changing provider signatures

AsyncValue stuck loading: Check repository returns data, use AsyncValue.guard() to catch errors

Hard Prohibitions

• No Navigator.push with raw strings — use GoRouter type-safe routes exclusively
• No returning null on async error — use AsyncValue.error, never null/empty fallbacks
• No Color(0x...) or Colors.* — use Theme.of(context).colorScheme.*
• No raw EdgeInsets with numeric values — use AppSpacing.* tokens
• No inline TextStyle(fontSize: ...) — use Theme.of(context).textTheme.*

Sealed Types vs Boolean Flag Soup

Anti-pattern — boolean flags that create invalid states:

// ❌ 4 booleans = 16 possible states, most invalid
class LoadState {
  bool isLoading = false;
  bool isError = false;
  bool isEmpty = false;
  bool isSuccess = false;
  // isLoading=true AND isSuccess=true is invalid but representable
}

Correct — sealed class makes invalid states unrepresentable:

// ✅ Dart 3 sealed class — exactly 4 valid states
sealed class LoadState<T> {}

final class LoadingState<T> extends LoadState<T> {}
final class ErrorState<T> extends LoadState<T> {
  final Object error;
  final StackTrace? stack;
  ErrorState(this.error, [this.stack]);
}
final class EmptyState<T> extends LoadState<T> {}
final class SuccessState<T> extends LoadState<T> {
  final T data;
  SuccessState(this.data);
}

// Usage — exhaustive pattern matching (compiler enforces all cases):
Widget build(BuildContext context) {
  return switch (state) {
    LoadingState() => const CircularProgressIndicator(),
    ErrorState(:final error) => ErrorWidget(error.toString()),
    EmptyState() => const Text('No items'),
    SuccessState(:final data) => ItemList(data),
  };
}

Rule: Use sealed classes + switch expressions for any state with 3+ mutually exclusive cases. Applies to: UI state, network state, auth state, form state.

Applies to: Flutter 3.41.x / Dart 3.10.9+ (sealed classes require Dart 3.0+)

State Management Quick Reference

Library-agnostic comparison (for Riverpod-specific patterns, see .claude/skills/riverpod-patterns/):

This workspace's stack uses Riverpod — see .claude/skills/riverpod-patterns/ for detailed patterns.

Post-Code Review

After writing Dart code, dispatch these reviewer agents:

• riverpod-reviewer — state management, provider types, AsyncValue handling
• flutter-security-expert — secure storage, certificate pinning, data protection
• accessibility-auditor — WCAG 2.1 compliance, Semantics widgets, touch targets

Pre-submit checks (smart/dumb pattern):

• shared_ui/ widgets extend StatelessWidget — zero ref/ConsumerWidget usage
• ref.watch() only in ConsumerWidget build(); ref.read() only in callbacks

Templates Reference

For all code templates (pubspec.yaml, Freezed models, Riverpod providers, screen widgets, GoRouter config, widget tests, Firebase integration, repository patterns):

Read reference/flutter-templates.md