| name | mobile-craft |
| description | Mobile engineering standards — React Native/Expo/Flutter/native patterns, list and image performance, offline behavior, platform conventions, secure storage, and the device checklist. Use when building any mobile screen, navigation, or device-facing feature. |
| user-invocable | false |
Mobile Craft
Detect the stack from the codebase (React Native/Expo, Flutter, Swift/Kotlin) and
follow that ecosystem's idioms; these standards apply across all of them.
Performance
- Lists are virtualized (FlatList/FlashList, ListView.builder) with stable keys and
memoized row components; never map an unbounded array into a scroll view.
- Images: explicit dimensions, cached loading, appropriately sized sources; no
full-resolution assets in thumbnails.
- Keep the UI thread at 60fps: heavy computation off-thread or deferred; animations
on the native driver where the framework offers it.
- Measure cold start impact when adding libraries — mobile bundles pay for every dependency.
Resilience & offline
- Every network surface has loading / empty / error / offline states; retry
affordances where actions can fail.
- Assume the network drops mid-request: writes should be safe to retry (or queued);
never leave the UI in a lying state.
- Persist appropriate state so a killed/restored app resumes sensibly.
Platform conventions
- Safe-area insets respected everywhere (notches, home indicator, status bar).
- Touch targets ≥ 44pt with adequate spacing; gestures follow platform norms.
- Android: hardware back button does the right thing on every screen; Predictive back where supported.
- Keyboard: forms scroll into view, inputs use correct keyboard types, return-key flow works.
- Permissions requested in context with rationale, and every denial path handled.
Security
- Tokens/secrets in secure storage (Keychain/Keystore or the framework's secure
wrapper) — never AsyncStorage/SharedPreferences/plaintext files.
- No sensitive data in logs, crash reports, or screenshots of secure screens.
- Certificate/ATS defaults respected; no cleartext HTTP.
Pre-delivery checklist (run before reporting done)
