---
name: expo-development
description: "Expo and React Native apps: Continuous Native Generation, EAS Build and Update, Expo Router. Use when creating or configuring an Expo app, its EAS builds, native modules, routes or OTA updates."
---

# Expo Development

## Continuous Native Generation

- Never eject, never edit `ios/` or `android/` — `npx expo prebuild` regenerates both from `app.json` / `app.config.ts`, so hand edits vanish. Gitignore both directories. `npx expo prebuild --clean` when native state is suspect.
- Native config changes go through config plugins (`app.plugin.js`, registered in `expo.plugins`) applied at prebuild time. `npx create-expo-module` scaffolds a Swift + Kotlin module.
- Install with `npx expo install`, not `npm install`, so versions resolve against the SDK. `npx expo install --fix` repairs an SDK version mismatch.

## EAS Build / Update

- `eas.json` profiles: development = `developmentClient: true` + `distribution: internal`; preview = `distribution: internal` + `channel`; production = `channel` + `autoIncrement: true`.
- Set `runtimeVersion: { policy: "fingerprint" }` in app.json. `eas update --channel production` ships JS only — a runtimeVersion mismatch forces a new binary build, and native changes can never go OTA.
- Rollback: `eas update:republish --group <previous-group-id>`. Diagnose failures via `eas build:list` then `eas build:view <id>`.
- Secrets belong in EAS environment variables with secret visibility (`eas env:create --visibility secret`; `eas secret:create` is deprecated), never `app.json`; device-side storage via `expo-secure-store`.
- iOS signing failures: `eas credentials`. CI/CD lives in `.eas/workflows/`.

## Expo Router

Files under `app/` are routes; a `_layout.tsx` per directory supplies `<Stack>` / `<Tabs>` / `<Drawer>`. Parenthesized directories are groups and do not appear in the URL — `app/(auth)/login.tsx` serves `/login`. Read dynamic segments with `useLocalSearchParams()`. Deep links require `scheme` in app.json; `myapp://user/123` then resolves to `app/user/[id].tsx`.

Docs: https://docs.expo.dev/