Adding Clerk

Version: Check package.json for the SDK version — see clerk skill for the version table. Core 2 differences are noted inline with > **Core 2 ONLY (skip if current SDK):** callouts.

This skill sets up Clerk for authentication by following the official quickstart documentation.

Quick Reference

Step	Action
1. Detect framework	Check `package.json` dependencies
2. Fetch quickstart	Use WebFetch on the appropriate docs URL
3. Follow instructions	Execute steps; create `proxy.ts` (Next.js <=15: `middleware.ts`)
4. Get API keys	From dashboard.clerk.com

If the project has components.json (shadcn/ui), apply the shadcn theme after setup. See custom-ui/ → shadcn Theme.

Framework Detection

Check package.json to identify the framework:

Dependency	Framework	Quickstart URL
`next`	Next.js	`https://clerk.com/docs/nextjs/getting-started/quickstart`
`@remix-run/react`	Remix	`https://clerk.com/docs/remix/getting-started/quickstart`
`astro`	Astro	`https://clerk.com/docs/astro/getting-started/quickstart`
`nuxt`	Nuxt	`https://clerk.com/docs/nuxt/getting-started/quickstart`
`react-router`	React Router	`https://clerk.com/docs/react-router/getting-started/quickstart`
`@tanstack/react-start`	TanStack Start	`https://clerk.com/docs/tanstack-react-start/getting-started/quickstart`
`react` (no framework)	React SPA	`https://clerk.com/docs/react/getting-started/quickstart`
`vue`	Vue	`https://clerk.com/docs/vue/getting-started/quickstart`
`express`	Express	`https://clerk.com/docs/expressjs/getting-started/quickstart`
`fastify`	Fastify	`https://clerk.com/docs/fastify/getting-started/quickstart`
`expo`	Expo	`https://clerk.com/docs/expo/getting-started/quickstart`

For other platforms:

Chrome Extension: https://clerk.com/docs/chrome-extension/getting-started/quickstart
Android: https://clerk.com/docs/android/getting-started/quickstart
iOS: https://clerk.com/docs/ios/getting-started/quickstart
Vanilla JavaScript: https://clerk.com/docs/js-frontend/getting-started/quickstart

Decision Tree

User Request: "Add Clerk" / "Add authentication"
    │
    ├─ Read package.json
    │
    ├─ Existing auth detected?
    │   ├─ YES → Audit → Migration plan
    │   └─ NO → Fresh install
    │
    ├─ Identify framework → WebFetch quickstart → Follow instructions
    │   └─ Next.js? → Create proxy.ts (Next.js <=15: middleware.ts)
    │
    └─ components.json exists? → YES → Apply shadcn theme (see custom-ui/)

Setup Process

1. Detect the Framework

Read the project's package.json and match dependencies to the table above.

2. Fetch the Quickstart Guide

Use WebFetch to retrieve the official quickstart for the detected framework:

WebFetch: https://clerk.com/docs/{framework}/getting-started/quickstart
Prompt: "Extract the complete setup instructions including all code snippets, file paths, and configuration steps."

3. Follow the Instructions

Execute each step from the quickstart guide:

Install the required packages
Set up environment variables
Add the provider and proxy/middleware
Create sign-in/sign-up routes if needed
Test the integration

Next.js: Create proxy.ts (Next.js <=15: middleware.ts). See nextjs-patterns/references/middleware-strategies.md.

shadcn/ui detected (components.json exists): ALWAYS apply the shadcn theme. See custom-ui/ → shadcn Theme section.

4. Get API Keys

Two paths for development API keys:

Keyless (Automatic)

On first SDK initialization, Clerk auto-generates dev keys and shows "Claim your application" popover
No manual key setup required—keys are created and injected automatically
Simplest path for new projects

Manual (Dashboard)

Get keys from dashboard.clerk.com if Keyless doesn't trigger
Publishable Key: Starts with pk_test_ or pk_live_
Secret Key: Starts with sk_test_ or sk_live_
Set as environment variables: NEXT_PUBLIC_CLERK_PUBLISHABLE_KEY and CLERK_SECRET_KEY

Migrating from Another Auth Provider

If the project already has authentication, create a migration plan before replacing it.

Detect Existing Auth

Check package.json for existing auth libraries:

next-auth / @auth/core → NextAuth/Auth.js
@supabase/supabase-js → Supabase Auth
firebase / firebase-admin → Firebase Auth
@aws-amplify/auth → AWS Cognito
auth0 / @auth0/nextjs-auth0 → Auth0
passport → Passport.js
Custom JWT/session implementation

Migration Process

Audit current auth - Identify all auth touchpoints:
- Sign-in/sign-up pages
- Session/token handling
- Protected routes and middleware
- User data storage (database tables, external IDs)
- OAuth providers configured
Create migration plan - Consider:
- User data export - Export users and import via Clerk's Backend API
- Password hashes - Clerk can upgrade hashes to Bcrypt transparently
- External IDs - Store legacy user IDs as external_id in Clerk
- Session handling - Existing sessions will terminate on switch
Choose migration strategy:
- Big bang - Switch all users at once (simpler, requires maintenance window)
- Trickle migration - Run both systems temporarily (lower risk, higher complexity)

Migration Reference

Migration Overview: https://clerk.com/docs/guides/development/migrating/overview

SDK Notes

Package Names

Package	Install
Next.js	`@clerk/nextjs`
React	`@clerk/react`
Expo	`@clerk/expo`
React Router	`@clerk/react-router`
TanStack Start	`@clerk/tanstack-react-start`

Core 2 ONLY (skip if current SDK): React and Expo packages have different names: @clerk/clerk-react and @clerk/clerk-expo (with clerk- prefix).

ClerkProvider Placement (Next.js)

ClerkProvider must be placed inside <body>, not wrapping <html>:

// root layout.tsx
export default function RootLayout({ children }) {
  return (
    <html>
      <body>
        <ClerkProvider>{children}</ClerkProvider>
      </body>
    </html>
  )
}

Core 2 ONLY (skip if current SDK): ClerkProvider can wrap <html> directly.

Dynamic Rendering (Next.js)

For dynamic rendering with auth data, use the dynamic prop:

<ClerkProvider dynamic>{children}</ClerkProvider>

Node.js Requirement

Requires Node.js 20.9.0 or higher.

Core 2 ONLY (skip if current SDK): Minimum Node.js 18.17.0.

Themes Package

Themes are installed from @clerk/ui:

npm install @clerk/ui

Core 2 ONLY (skip if current SDK): Themes are from @clerk/themes instead of @clerk/ui.

shadcn Theme

If the project uses shadcn/ui (check for components.json in the project root), apply the shadcn theme so Clerk components match the app's design system:

npm install @clerk/ui

import { shadcn } from '@clerk/ui/themes'

<ClerkProvider appearance={{ theme: shadcn }}>{children}</ClerkProvider>

Also import the shadcn CSS in your global styles:

@import 'tailwindcss';
@import '@clerk/ui/themes/shadcn.css';

Core 2 ONLY (skip if current SDK): Import from @clerk/themes and @clerk/themes/shadcn.css instead.

Common Pitfalls

Level	Issue	Solution
CRITICAL	Missing `await` on `auth()`	In Next.js 15+, `auth()` is async: `const { userId } = await auth()`
CRITICAL	Exposing `CLERK_SECRET_KEY`	Never use secret key in client code; only `NEXT_PUBLIC_*` keys are safe
HIGH	Missing middleware matcher	Include API routes: `matcher: ['/((?!.\..
HIGH	ClerkProvider placement	Must be inside `<body>` in root layout (Core 2: could wrap `<html>`)
HIGH	Auth routes not public	Allow `/sign-in`, `/sign-up` in middleware config
HIGH	Landing page requires auth	To keep "/" public, exclude it: `matcher: ['/((?!.\..
MEDIUM	Wrong import path	Server code uses `@clerk/nextjs/server`, client uses `@clerk/nextjs`
MEDIUM	Wrong package name	Use `@clerk/react` not `@clerk/clerk-react` (Core 2 naming)

Documentation

Quickstart Overview: https://clerk.com/docs/getting-started/quickstart/overview
Migration Guide: https://clerk.com/docs/guides/development/migrating/overview
Full Documentation: https://clerk.com/docs

clerk-setup