# Flutter Performance

> Optimization standards for rebuilds and memory.

- Skill: `fierzone/flutter-performance` (Agent Skill)
- Install (CLI): `npx skillmds@latest add fierzone/flutter-performance`
- Raw SKILL.md: https://api.skillmd.com/api/skills/fierzone/flutter-performance/raw
- Safety review: pending
- Works with: Claude Code, Claude.ai, OpenAI Codex
- Category: Coding & Dev Tools
- Author: fierzone (https://skillmd.com/u/fierzone)
- Updated: 2026-09-10
- Page: https://skillmd.com/skills/fierzone/flutter-performance

---


# Performance

## **Priority: P1 (OPERATIONAL)**

Performance optimization techniques for smooth 60fps Flutter applications.

- **Rebuilds**: Use `const` widgets and `buildWhen` / `select` for granular updates.
- **Lists**: Always use `ListView.builder` for item recycling.
- **Heavy Tasks**: Use `compute()` or `Isolates` for parsing/logic.
- **Repaints**: Use `RepaintBoundary` for complex animations. Use `debugRepaintRainbowEnabled` to debug.
- **Images**: Use `CachedNetworkImage` + `memCacheWidth`. `precachePicture` for SVGs.

## 🚫 Anti-Patterns

- **Large Rebuilds**: `**No SetState at Root**: Use granular builders (BlocBuilder, Consumer).`
- **Logic in Build**: `**No Heavy Work in body**: Perform parsing/sorting in the Business Layer.`
- **Missing Const**: `**No Dynamic Leaf Widgets**: Use const where possible.`

```dart
BlocBuilder<UserBloc, UserState>(
  buildWhen: (p, c) => p.id != c.id,
  builder: (context, state) => Text(state.name),
)
```