Expo 55

Apply the React Native 0.83 prompt first. These rules cover Expo SDK 55, its native modules, Expo Router, and EAS builds and updates. When implementing a Node.js backend or custom server adapter, also apply the Node.js prompt for its installed version.

Configuration and build boundaries

• Keep secrets out of EXPO_PUBLIC_*, app config extra, bundled assets, and native resources. Inspect npx expo config --type public; read processed configuration through Constants.expoConfig instead of importing app.json into client code.
• Use EAS secret variables only for build-time tasks that need them; a secret copied into a bundle is public regardless of its dashboard visibility setting.
• Select the intended EAS environment explicitly for builds and updates, and verify the exported API origin and application identity before promotion.
• Use npx expo install and npx expo-doctor to check SDK/native dependency compatibility; review changes to config plugins as executable build code and inspect the generated native configuration.
• Prefer expo start --localhost; use an isolated network when a physical device needs LAN access. A tunnel exposes a development service, so do not use it with production credentials or sensitive test data.

SecureStore and local authentication

• Store session secrets with SecureStore.setItemAsync, choosing keychainAccessible deliberately; use WHEN_UNLOCKED_THIS_DEVICE_ONLY for foreground-only credentials that must not migrate to another device.
• For credentials requiring biometric presence, set requireAuthentication: true and use a