everything-react-native-expo: Skill for Claude Code

/erne-perf — Performance Profiling

You are executing the /erne-perf command. Use the performance-profiler agent to diagnose and fix performance issues.

Diagnostic Areas

1. Rendering Performance (FPS)

• Check for unnecessary re-renders with React DevTools Profiler
• Identify components re-rendering without prop changes
• Look for missing React.memo, useCallback, useMemo
• Detect inline function/object creation in render

2. Time to Interactive (TTI)

• Analyze app startup sequence
• Check for heavy useEffect chains on mount
• Identify blocking operations on main thread
• Verify Hermes bytecode compilation

3. Bundle Size

• Run npx react-native-bundle-visualizer
• Identify large dependencies
• Check for unused imports and dead code
• Verify tree-shaking is working

4. Memory

• Check for listener/subscription cleanup in useEffect
• Identify large objects retained in closures
• Look for image caching issues
• Detect circular references

5. Animations

• Verify all animations use Reanimated (not Animated API)
• Check for JS thread bottlenecks in animation callbacks
• Identify layout thrashing during animations
• Measure actual FPS during animations

6. Hermes Engine

• Verify Hermes is enabled
• Check for unsupported JS features
• Profile with Hermes sampling profiler
• Analyze bytecode compilation output

Output Format

## Performance Metrics
| Metric | Current | Target | Status |
|--------|---------|--------|--------|
| JS FPS | 45 | 60 | ⚠️ |
| UI FPS | 58 | 60 | ✅ |
| TTI | 3.2s | <2s | ❌ |
| Bundle | 8.2MB | <5MB | ❌ |

## Critical Issues
[Issues that must be fixed]

## Optimization Opportunities
[Improvements ranked by impact]

Notes

• If agent-device is available, measure actual FPS on device
• Reference rules/common/performance.md for optimization patterns
• Profile on real devices, not simulator/emulator