Flutter Reference

Flutter Reference

Use this skill when the user wants Flutter-specific guidance for building, reviewing, repairing, or diagnosing production mobile apps or games.

This is a doctrine-only reference skill. It ships no scripts, tests, runners, controllers, command wrappers, generated build files, or tool automation.

When to use

• The user wants Flutter architecture, state management, project structure, Dart style, API design, dependency policy, or code review guidance.
• The user wants help with Flutter lifecycle, keys, remounts, async ownership, animation stability, rebuild scope, rendering, memory, or concurrency.
• The user wants Flutter testing, CI/CD, profiling, accessibility, localization, security, platform integration, assets, input, or native interop guidance.
• The user wants Flutter game architecture, Flame, HUD/shell boundaries, game loops, audio, physics, or per-frame performance guidance.
• The user is authoring or reviewing Flutter code and needs practical standards rather than generic frontend advice.

When not to use

• The task is not about Flutter or Dart.
• The user wants generic visual design critique, product UX critique, or Figma file craft without Flutter implementation concerns.
• The user wants you to run Flutter tooling, operate an emulator, publish an app, or debug a local build pipeline. Use the repo's normal coding and tool workflow, then consult this skill only for Flutter judgment.
• The user asks for latest Flutter, Dart, package, Android, or iOS facts. Check current official docs before relying on version-sensitive claims.

Non-negotiables

• Treat repository code, app behavior, and official docs as source truth when they are available. This skill gives defaults and review doctrine, not magic facts about an unseen app.
• Prefer the lightest architecture that makes ownership, lifecycle, state, and data flow explicit. Do not add layers because the app feels like it should be "enterprise."
• Keep build() pure. Async work, subscriptions, controllers, platform calls, and state mutation belong in lifecycle methods, provider/controller boundaries, repositories, services, or game-world systems.
• Make identity explicit. Keys should reflect semantic identity, not incidental state that causes accidental remounts.
• Do not claim performance wins without measurement. Use profile mode and real devices for meaningful Flutter performance claims.
• For games and high-frequency simulations, keep per-frame world state out of the widget tree. Bridge coarse HUD or shell state into Flutter widgets.
• Preserve accessibility, localization, and security as first-class app quality, not late cleanup.

First move

1. Classify the user's request as author, review, repair, or diagnose.
2. Inspect the actual Flutter code, app structure, logs, screenshots, or failing behavior when the user provides them.
3. Load only the reference files needed for the current problem:
   • architecture/state decisions: references/architecture-and-state.md
   • Dart style, structure, APIs, dependencies: references/dart-style-project-structure-and-api.md
   • lifecycle, keys, async, animation replay: references/lifecycle-identity-and-async.md
   • performance, rendering, memory, isolates: references/performance-rendering-memory-and-concurrency.md
   • platform channels, input, assets, textures: references/platform-integration-input-assets.md
   • accessibility, localization, security: references/accessibility-localization-security.md
   • games, Flame, audio, physics: references/games-flame-audio-and-physics.md
   • testing, CI, reviews, anti-patterns: references/testing-ci-and-review-practice.md
   • current official docs and source links: references/source-map.md
4. If the request depends on current Flutter, Dart, package, Android, or iOS behavior, verify current official documentation before giving a version-sensitive answer.

Workflow

1. Start from the app's real shape: small app, medium/large product app, package/workspace, add-to-app, plugin-heavy app, or game.
2. Name the ownership boundary first: UI, view model/notifier/bloc, domain logic, repository, service/plugin adapter, platform code, or game world.
3. Choose the smallest state and architecture pattern that makes that boundary reviewable.
4. Check lifecycle and identity before chasing surface symptoms. Many Flutter bugs are remounts, recreated futures/streams/controllers, async gaps, or rebuild storms.
5. For performance work, separate UI-isolate work, raster work, memory, image cache/external memory, platform-view composition, and game-loop update cost.
6. For review output, lead with the concrete defect or decision, then explain the Flutter mechanism and the smallest repair.

Output expectations

• author: give a concrete Flutter architecture, code pattern, file structure, test plan, or implementation standard.
• review: findings first, with the Flutter mechanism, user-visible risk, and the smallest practical fix.
• repair: an ordered fix path that moves work to the right ownership layer and names the verification that proves it.
• diagnose: a short hypothesis list tied to Flutter runtime behavior, plus the next evidence to inspect.

Reference map

• references/architecture-and-state.md - architecture defaults, layered app design, repositories/services, state-management tradeoffs, and game shell boundaries.
• references/dart-style-project-structure-and-api.md - Dart style, lints, package layout, workspaces, dependency policy, public APIs, immutability, null safety, and typed errors.
• references/lifecycle-identity-and-async.md - widget identity, keys, remounts, lifecycle methods, side-effect placement, animation replay, futures/streams, setState, mounted guards, and lifecycle tests.
• references/performance-rendering-memory-and-concurrency.md - profile-mode measurement, frame budgets, rebuild scope, expensive paint/layout work, images, textures, memory, isolates, Android/iOS profiling, and renderer caveats.
• references/platform-integration-input-assets.md - platform channels, Pigeon, FFI, platform views, textures, gestures, focus, semantics, assets, image variants, and cache discipline.
• references/accessibility-localization-security.md - screen readers, semantics, large text, RTL, localized strings, secrets, obfuscation limits, transport security, secure storage, signing, and attestation.
• references/games-flame-audio-and-physics.md - Flutter game architecture, Flame, game loops, HUD overlays, ECS/components, per-frame allocation, Flame lifecycle, input, audio, and physics.
• references/testing-ci-and-review-practice.md - unit/widget/golden/ integration testing, leak checks, profile scenarios, CI lanes, anti-patterns, code review checklist, review comments, and limitations.
• references/source-map.md - official docs to verify version-sensitive Flutter, Dart, platform, state-package, testing, performance, and Flame facts.