Opinionated conventions for building cross-platform mobile apps with React Native and Expo.
# React Native App taste of a cross-platform mobile engineer - Start new apps with Expo and the prebuild workflow instead of a bare React Native project, and eject only when a native module truly needs it. Confidence: 0.90 - Write everything in TypeScript with strict mode on, including navigation params and native module bindings. Confidence: 0.95 - Use Expo Router for file-based navigation and keep typed routes enabled so broken links fail at compile time. Confidence: 0.80 - Keep server state in TanStack Query and limit global client state to a small Zustand store for session and preferences. Confidence: 0.85 - Never store tokens in AsyncStorage; use expo-secure-store or the Keychain and Keystore for anything sensitive. Confidence: 0.95 - Render long lists with FlashList or a well-tuned FlatList with stable keys, never a ScrollView with map. Confidence: 0.90 - Run animations on the UI thread with Reanimated and gestures with react-native-gesture-handler, not the old Animated API. Confidence: 0.85 - Enable the New Architecture and Hermes by default and treat libraries that block it as tech debt. Confidence: 0.75 - Keep a single theme module for colors, spacing and typography, and support dark mode from the first screen. Confidence: 0.85 - Respect safe areas with react-native-safe-area-context instead of hardcoded padding for notches. Confidence: 0.90 - Put platform-specific code in .ios.tsx and .android.tsx files rather than scattering Platform.OS checks. Confidence: 0.70 - Ship JavaScript fixes through EAS Update with a runtime version policy, and use store releases for native changes. Confidence: 0.80 - Build and sign in CI with EAS Build so no release depends on a single laptop. Confidence: 0.85 - Test components with React Native Testing Library and query by role and text, not by testID first. Confidence: 0.80 - Cover the critical flows end to end with Maestro or Detox on real simulators in CI. Confidence: 0.75 - Add accessibilityLabel and accessibilityRole to every touchable and keep tap targets at least 44 points. Confidence: 0.90 - Handle offline as a normal state: show cached data, queue writes and retry when the connection returns. Confidence: 0.80 - Report crashes and JavaScript errors with Sentry including source maps for every release. Confidence: 0.85 - Optimize images with expo-image and caching instead of the default Image component. Confidence: 0.80 - Profile with the React Native DevTools before guessing at performance fixes. Confidence: 0.70 - Ask for permissions only at the moment a feature needs them, with a short explanation screen first. Confidence: 0.90
AST-based code pattern analysis using ast-grep for security, performance, and structural issues. Use when (1) reviewing code for security vulnerabilities, (2) analyzing React hook dependencies or performance patterns, (3) detecting structural anti-patterns across large codebases, (4) needing systematic pattern matching beyond manual inspection.
Act as an expert in building cross-platform applications with advanced 3D design capabilities for both iOS and Android platforms.
Guide for creating high-quality MCP (Model Context Protocol) servers that enable LLMs to interact with external services through well-designed tools. Use when building MCP servers to integrate external APIs or services, whether in Python (FastMCP) or Node/TypeScript (MCP SDK).
