clerk-expo

name	clerk-expo
description	Implement Clerk authentication for Expo and React Native apps using @clerk/expo source-guided patterns. Use for prebuilt AuthView/UserButton or custom hook-driven auth flows. Do not use for native iOS/Swift, native Android/Kotlin, or web framework projects.
license	MIT
allowed-tools	WebFetch
metadata	{"author":"clerk","version":"1.0.0"}
compatibility	Requires Expo development build and @clerk/expo package

Clerk Expo (React Native)

This skill implements Clerk in Expo / React Native projects by inspecting the installed @clerk/expo package source and mirroring current hook and component behavior.

Activation Rules

Activate this skill when either condition is true:

• The user explicitly asks for Expo, React Native, @clerk/expo, ClerkProvider, or related Clerk component/hook implementation.
• The project appears to be Expo/React Native (for example app.json, app.config.js, metro.config.js, expo in package.json, @clerk/expo dependency).

Do not activate this skill when any condition is true:

• The project is native iOS/Swift (.xcodeproj, .xcworkspace, Package.swift, Swift targets).
• The project is native Android/Kotlin (build.gradle(.kts) with Android plugins, AndroidManifest.xml, no React Native).
• The project is a web-only framework (Next.js, Remix, etc.) without Expo/React Native.

If native iOS/Android or web-framework signals are present, route to the matching skill instead of this one.

Relationship to clerk-expo-patterns

This skill covers flow selection and end-to-end auth setup (prebuilt vs custom). The clerk-expo-patterns skill at skills/frameworks/clerk-expo-patterns/ covers Expo-specific recipes (SecureStore token cache, OAuth deep-link configuration, Expo Router protected routes, push notifications with user context). When both could apply, use this skill for the flow decision and overall setup, and load patterns from clerk-expo-patterns for the specific recipe.

What Do You Need?

Task	Reference
Prebuilt AuthView / UserButton (fastest)	references/prebuilt.md
Custom hook-driven auth flows (full control)	references/custom.md

Quick Start

Step	Action
1	Confirm project type is Expo/React Native (not native iOS/Android or a web-only framework)
2	Determine flow type (prebuilt or custom) and load the matching reference file
3	Ensure a real Clerk publishable key exists (or ask developer) and wire it directly to <ClerkProvider publishableKey={...}>
4	Ensure @clerk/expo is installed; if missing, install latest with npx expo install @clerk/expo
5	Inspect installed @clerk/expo source (node_modules/@clerk/expo/dist/ or src/) to understand component/hook behavior for the selected flow
6	For custom flows: derive Frontend API URL from publishable key, then call <frontendApiUrl>/v1/environment?_is_native=true and build an internal enabled-factor checklist
7	Follow the Expo quickstart (https://clerk.com/docs/getting-started/quickstart, Expo SDK tab) for required setup (config plugin, token cache, native build)
8	Implement flow by following only the selected reference checklist

Decision Tree

User asks for Clerk in Expo/React Native
    |
    +-- Native iOS/Android or web-framework project detected?
    |     |
    |     +-- YES -> Do not use this skill; route to matching skill
    |     |
    |     +-- NO -> Continue
    |
    +-- Existing auth UI detected?
    |     |
    |     +-- Prebuilt AuthView/UserButton detected -> Load references/prebuilt.md
    |     |
    |     +-- Custom hook-based flow detected -> Load references/custom.md
    |     |
    |     +-- New implementation -> Ask developer prebuilt/custom, then load matching reference
    |
    +-- Ensure publishable key and direct ClerkProvider wiring
    |
    +-- Ensure @clerk/expo is installed and Expo config plugin is registered
    |
    +-- Inspect installed @clerk/expo source for selected flow
    |
    +-- For custom flows: call /v1/environment?_is_native=true and build enabled-factor checklist
    |
    +-- Verify Expo quickstart prerequisites (token cache, dev build, peer deps)
    |
    +-- Implement using selected flow reference

Flow References

After flow type is known, load exactly one:

• Prebuilt flow: references/prebuilt.md
• Custom flow: references/custom.md

Do not blend the two references in a single implementation unless the developer explicitly asks for a hybrid approach.

Interaction Contract

Before any implementation edits, the agent must have both:

• flow choice: prebuilt or custom
• a real Clerk publishable key (when setup/configuration is part of the task)

If either value is missing from the user request/context:

• ask the user for the missing value(s)
• pause and wait for the answer
• do not edit files or install dependencies yet

Only skip asking when the user has already explicitly provided the value in this conversation.

Source-Driven Templates

Do not hardcode implementation examples in this skill. Inspect installed @clerk/expo source for the project's installed version before implementing.

Use Case	Source of Truth in Installed Package
Package exports and sub-paths (@clerk/expo/google, /apple, /native, /token-cache, /local-credentials, /resource-cache, /web)	node_modules/@clerk/expo/package.json exports field plus compiled output in dist/
Hook signatures and return types	node_modules/@clerk/expo/dist/*.d.ts plus re-exported types from node_modules/@clerk/react/dist/*.d.ts
Native component props and events	node_modules/@clerk/expo/dist/native/* (search AuthView, InlineAuthView, UserButton, UserProfileView)
Sign-in / sign-up status transitions	node_modules/@clerk/react/dist/ hook source (search useSignIn, useSignUp, status)
SSO and OAuth behavior	node_modules/@clerk/expo/dist/ (search useSSO, startSSOFlow, session_exists, transferable)
Native Google / Apple sign-in path	node_modules/@clerk/expo/google and /apple modules
Token persistence	node_modules/@clerk/expo/token-cache (backed by expo-secure-store)
Session sync between native SDK and JS	node_modules/@clerk/expo/dist/native/ (search NativeSessionSync, useNativeAuthEvents)
Expo config plugin behavior	node_modules/@clerk/expo/app.plugin.js (search withClerkGoogleSignIn, withClerkAndroidPackaging)
Required Expo setup checklist	Official Expo quickstart (https://clerk.com/docs/getting-started/quickstart, Expo SDK tab)

Execution Gates (Do Not Skip)

1. No implementation edits before prerequisites

• Do not edit project files until flow type is confirmed and (when setup is involved) a valid publishable key is available.

2. Missing flow or key must trigger a question

• If flow choice is missing, explicitly ask: prebuilt views or custom flow.
• If publishable key is missing/placeholder/invalid for a setup task, explicitly ask for a real key.
• Do not continue until required answers are provided.

3. Publishable key wiring mode is mandatory

• Pass the developer-provided publishable key directly to <ClerkProvider publishableKey={key}>.
• Do not introduce env-var indirection (process.env.EXPO_PUBLIC_CLERK_PUBLISHABLE_KEY) unless the developer explicitly asks for it or the project follows the quickstart pattern.

4. Package install policy is mandatory

• If @clerk/expo is missing, install with npx expo install @clerk/expo.
• Install matching peer deps for the selected strategies (see prebuilt.md / custom.md for the per-flow list).
• Register the Expo config plugin in app.json / app.config.js: { "plugins": ["@clerk/expo"] }.

5. Custom-flow environment call is mandatory

• For custom flows: derive Frontend API URL from publishable key, fetch /v1/environment?_is_native=true, and use the response to determine enabled factors/strategies.
• Build an internal enabled-factor checklist; cover all enabled factors unless the developer explicitly narrows scope.
• Do not skip the environment call. Do not assume strategy coverage from convention.

6. Reference-file discipline is mandatory

• Once flow is selected, follow only that flow reference file for implementation and verification.

7. Hook-source-first discipline for custom flows

• Inspect installed @clerk/expo and @clerk/react hook source for response/error handling before deciding flow transitions.
• Mirror status-driven transitions from hook source rather than from UI heuristics or assumptions.

8. Combined sign-in-or-up default

• Implement one combined sign-in-or-up flow by default; do not split into separate sign-in / sign-up flows unless the developer explicitly requests separation.

9. Deprecated hook prohibition

• Never use useOAuth(). Always use useSSO() for OAuth and Enterprise SSO.

10. Platform / build gating

• Native components and native hooks (useSignInWithGoogle, useSignInWithApple, useNativeSession, useUserProfileModal, useLocalCredentials) require an iOS/Android development build, not Expo Go and not web.
• For web targets, use @clerk/expo/web exports.
• Always note platform availability before recommending native-only features.

11. Token cache discipline

• Use tokenCache from @clerk/expo/token-cache for persistent sessions; do not use expo-secure-store directly for token storage.

Workflow

1. Detect Expo/React Native vs native iOS/Android vs web framework.
2. If flow type is not explicitly provided, ask user for prebuilt or custom.
3. If publishable key is not explicitly provided for a setup task, ask user for it.
4. Wait for required answers before changing files.
5. Load the matching flow reference file.
6. Ensure <ClerkProvider> is at the app root with the publishable key wired directly and tokenCache from @clerk/expo/token-cache.
7. Ensure @clerk/expo is installed and the Expo config plugin is registered. Install peer deps for selected strategies.
8. Inspect installed @clerk/expo source for components/hooks relevant to the selected flow.
9. For custom flows: derive Frontend API URL from publishable key, call /v1/environment?_is_native=true, and build an internal enabled-factor checklist.
10. Verify Expo quickstart prerequisites (config plugin, token cache, native development build) and apply any missing required setup.
11. Implement using selected reference checklist.
12. For custom flows: verify implemented strategy coverage against the environment-derived checklist; close any missing enabled factor unless explicitly scoped out.
13. Verify using selected reference checklist plus shared gates.

Common Pitfalls

Level	Issue	Prevention
CRITICAL	Not asking for missing flow choice before implementation	Ask for prebuilt vs custom and wait before edits
CRITICAL	Not asking for missing publishable key on setup tasks	Ask for key and wait before edits
CRITICAL	Wiring publishable key via env-var indirection by default	Pass key directly to <ClerkProvider> unless developer requests otherwise
CRITICAL	Skipping /v1/environment?_is_native=true for custom flows	Call environment endpoint and build enabled-factor checklist before implementing
CRITICAL	Splitting sign-in / sign-up by default	Implement one combined sign-in-or-up flow unless developer explicitly requests separation
CRITICAL	Using useOAuth() (deprecated)	Always use useSSO()
CRITICAL	Mixing native components with custom hook flows for the same auth step	Pick one flow per step; only blend with explicit developer approval
CRITICAL	Skipping native development build for native components/hooks	Require expo run:ios / expo run:android; do not target Expo Go for native features
HIGH	Using expo-secure-store directly for token caching	Use tokenCache from @clerk/expo/token-cache
HIGH	Calling WebBrowser.maybeCompleteAuthSession() manually	ClerkProvider handles it; do not duplicate
HIGH	Calling setActive() after native component auth	Native components sync session automatically
HIGH	Hardcoding OAuth provider lists	Build provider lists from environment-enabled providers
HIGH	Recommending native-only hooks without web/Expo Go fallback	Note platform availability and provide useSSO() fallback where needed
HIGH	Using this skill for native iOS/Android or web-only framework projects	Detect and route away to clerk-swift / clerk-android / web-framework skills
HIGH	Using yalc or pnpm link for local @clerk/expo development	Use Verdaccio or pkg.pr.new

See Also

• clerk skill for top-level Clerk routing
• clerk-expo-patterns skill (skills/frameworks/clerk-expo-patterns/) for Expo-specific recipes (SecureStore token cache, OAuth deep links, Expo Router protected routes, push notifications)
• clerk-swift skill for native iOS implementation
• clerk-android skill for native Android implementation
• installed @clerk/expo package source (node_modules/@clerk/expo/)
• https://github.com/clerk/javascript/tree/main/packages/expo
• https://github.com/clerk/clerk-expo-quickstart
• https://clerk.com/docs/getting-started/quickstart (Expo SDK tab)
• https://clerk.com/docs/reference/expo/overview