Clerk Expo

Clerk Expo (React Native)

Implement Clerk in Expo / React Native projects. This skill inlines verified patterns for the stable surface (provider, token cache, flows) and requires source inspection of the installed @clerk/expo package for anything volatile (component props, hook signatures).

Activation Rules

Activate when either is true:

• The user asks for auth in an Expo or React Native app, or mentions @clerk/expo, ClerkProvider, Expo Router auth, or Clerk hooks in a native app.
• The project is Expo/React Native (app.json / app.config.js, expo in package.json, metro.config.js, @clerk/expo dependency).

Route away when:

• Native iOS/Swift project (.xcodeproj, Package.swift) → clerk-swift
• Native Android/Kotlin project (build.gradle without React Native) → clerk-android
• Web-only framework (Next.js, Remix, plain React, etc.) → the matching framework skill

Intent Map

Match what the user asked for, then load the reference(s) listed. Load only what the task needs.

Default Path Decision

When the user says "add auth" without specifying UI:

1. Default to prebuilt native components (AuthView + UserButton from @clerk/expo/native). Fastest to working auth; UI is maintained by Clerk. Tell the developer they are in beta and require a development build.
2. Fall back to custom flows when any of these hold — say why when you switch:
   • The project must run in Expo Go (no dev build).
   • The app targets web (native components don't render on web).
   • The developer wants their own UI or a specific brand experience beyond theming.
3. If the developer has an existing auth UI, extend what's there — don't rip out custom flows to insert AuthView (or vice versa) without being asked.

Do not blend prebuilt components and custom flows for the same auth step (e.g. AuthView plus a custom password form). Blending is allowed only when the developer explicitly asks.

Quick Workflow

1. Confirm project type (Expo/RN) and pick the path per the Intent Map / Default Path rules.
2. Follow references/setup.md: install, env key, provider, token cache, config plugin, build type.
3. Verify dashboard prerequisites (Gate 2 and Gate 3 below).
4. Implement from the selected reference only.
5. Verify by building, not just by writing:
   • Run the project's typecheck (npx tsc --noEmit or equivalent).
   • Build and launch: npx expo run:ios / run:android for native features, npx expo start for Expo Go flows. If the build fails, fix and rebuild iteratively — build errors against the installed SDK are the ground truth when this skill and the SDK disagree. After ~5 failed fix attempts, stop and ask the developer how to proceed instead of thrashing.
   • Walk the developer through one real sign-in, then confirm the session survives an app restart (token cache working).

Execution Gates (Do Not Skip)

1. Publishable key — Read from process.env.EXPO_PUBLIC_CLERK_PUBLISHABLE_KEY (.env file). Never NEXT_PUBLIC_, never hardcoded. If no key exists, ask the developer for one (or run npx clerk@latest init --framework expo, which installs the SDK and writes the env file) and wait before editing files.
2. Native API dashboard toggle — Clerk's Native API must be enabled for the instance: Clerk Dashboard → Native applications (https://dashboard.clerk.com/~/native-applications). Tell the developer to verify this during setup; it is required for any native integration.
3. Factor availability — Before implementing a specific strategy (SMS, email code, social provider), confirm it's enabled for the instance. Derive the Frontend API URL from the publishable key (base64-decode the middle segment) and fetch <frontendApiUrl>/v1/environment?_is_native=true, or ask the developer to check the dashboard (User & authentication). SMS in particular is instance-configuration-dependent — code written for a disabled factor fails at runtime, not build time.
4. Current custom-flows API only — useSignIn() / useSignUp() from @clerk/expo (v3.4+) return { signIn, errors, fetchStatus } and use method-based flows: signIn.password(), signIn.phoneCode.sendCode(), signIn.finalize(). Never generate the legacy pattern: destructuring isLoaded/setActive from useSignIn()/useSignUp() (the current hooks don't return them), or signIn.create() chained with prepareFirstFactor()/attemptFirstFactor() + setActive({ session }). That pattern lives at @clerk/expo/legacy and is only for maintaining existing legacy code, never for new work. Scope notes: isLoaded from useAuth()/useUser() is current API and required in guards; signIn.create() itself still exists for advanced cases — prefer the factor-specific methods.
5. useSSO(), never useOAuth() — useOAuth is deprecated. Note the asymmetry: startSSOFlow() still returns { createdSessionId, setActive } and requires setActive({ session: createdSessionId }) — SSO does not use finalize().
6. Token cache — tokenCache from @clerk/expo/token-cache on ClerkProvider. Never use expo-secure-store directly for session tokens, never AsyncStorage.
7. resourceCache, never secureStore — if offline resource caching comes up, @clerk/expo/secure-store is deprecated; use resourceCache from @clerk/expo/resource-cache.
8. Build-type gating — Native components (@clerk/expo/native) and native hooks (useSignInWithGoogle, useSignInWithApple, useLocalCredentials) require a development build (npx expo run:ios / run:android), not Expo Go, and don't exist on web. For web targets use @clerk/expo/web components or custom flows. State the build requirement before implementing a native-only feature.
9. Combined sign-in-or-up default — one combined flow unless the developer asks for separate sign-in and sign-up screens.
10. Bot protection — custom sign-up screens must render <View nativeID="clerk-captcha" />; Clerk's bot protection is on by default and needs this mount point.
11. Source verification for volatile surfaces — before using native component props or native hook options, confirm against the installed package: node_modules/@clerk/expo/dist/native/*.d.ts and package.json exports. The installed version wins over this skill if they disagree.
12. Freshness gate — this skill was verified against @clerk/expo 3.6.x. Check the installed version (node_modules/@clerk/expo/package.json). If it is a newer minor or major, treat this skill's code snippets as suspect: re-verify against the docs URL cited next to each snippet (every reference section carries one) or the installed .d.ts before using them. If it is older than 3.4, the method-based custom-flows API may not exist — offer an upgrade instead of writing legacy code.