# app-startup-and-bootstrap

> Claude/Codex skill by [@zakariaf](https://omgskills.com/library/zakariaf/index.md) · 61 stars · Updated 2026-09-23

Enforces a fixed main() cold-launch order — crash-log sink + FlutterError.onError + PlatformDispatcher.onError installed BEFORE any code that can throw, settings/theme read before runApp so the first frame paints correct, real infra constructed in a composition-root bootstrap() and injected via ProviderScope overrideWithValue over throwing placeholder providers, non-blocking warm-up deferred to addPostFrameCallback, exactly two error handlers with NO runZonedGuarded, ProviderException unwrapped before logging, and a WidgetsBindingObserver that flushes durable state on background/resume. Use when editing lib/main.dart, main\_\<flavor\>.dart, bootstrap.dart or app.dart, reordering anything in main(), adding a splash/onboarding/permission gate, restoring theme before first paint, wiring a DB or service into ProviderScope, handling app-lifecycle background/resume flushes, or chasing cold-start latency, ANRs, or first-frame jank.

Tags: agent-skills, ai-agents, best-practices, claude-code, codex, coding-agent, cursor, dart, dartlang, developer-tools, drift, flutter, flutter-architecture, github-copilot, go-router, llm, material-design, mvvm, riverpod, skills

## Install

```sh
git clone https://github.com/zakariaf/Flutter-Skills /tmp/Flutter-Skills && ln -s /tmp/Flutter-Skills/skills/app-startup-and-bootstrap ~/.claude/skills/app-startup-and-bootstrap
```

## From README

App startup and bootstrap main() has one job: a crash net, read the little state the first frame needs, wire real dependencies into the tree, and hand off to runApp — fast, ordered, and unable to hide a failure. Everything expensive happens after the first frame or off the launch path entirely. Non-negotiable rules Error handlers go first, before anything that can throw. A crash-log sink, FlutterError.onError, and PlatformDispatcher.instance.onError are installed immediately after WidgetsFlutterBinding.ensureInitialized(). The step most likely to throw is opening the DB; installing handlers after it inverts the whole point. Exactly two error handlers — no zone. FlutterError.onError (build/layout/paint errors) and PlatformDispatcher.instance.onError (uncaught async errors) cover every path. Never add runZonedGuarded. The "you need all three" advice is crash-SDK advice (Sentry wraps its init in a zone); with no such SDK a zone buys nothing and costs a documented zone-mismatch footgun.

## Links

- HTML page: https://omgskills.com/library/zakariaf/flutter-skills/skills/app-startup-and-bootstrap/
- GitHub: https://github.com/zakariaf/Flutter-Skills
- Author: [@zakariaf](https://omgskills.com/library/zakariaf/index.md)

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