clerk-nextjs-skills

Quick Start

1. Install Dependencies (Using pnpm)

bash

pnpm add @clerk/nextjs
# For MCP server integration, also install:
pnpm add @vercel/mcp-adapter @clerk/mcp-tools

2. Create proxy.ts (Next.js 16)

The

proxy.ts

file replaces

middleware.ts

from Next.js 15. Create it at the root or in

/src

typescript

// proxy.ts (or src/proxy.ts)
import { clerkMiddleware } from '@clerk/nextjs/server'

export default clerkMiddleware()

export const config = {
  matcher: [
    '/((?!_next|[^?]*\\.(?:html?|css|js(?!on)|jpe?g|webp|png|gif|svg|ttf|woff2?|ico|csv|docx?|xlsx?|zip|webmanifest)).*)',
    '/(api|trpc)(.*)',
  ],
}

3. Set Environment Variables

Create

.env.local

in your project root:

env

NEXT_PUBLIC_CLERK_PUBLISHABLE_KEY=your_publishable_key_here
CLERK_SECRET_KEY=your_secret_key_here
NEXT_PUBLIC_CLERK_SIGN_IN_URL=/sign-in
NEXT_PUBLIC_CLERK_SIGN_UP_URL=/sign-up
NEXT_PUBLIC_CLERK_AFTER_SIGN_IN_URL=/
NEXT_PUBLIC_CLERK_AFTER_SIGN_UP_URL=/

4. Add ClerkProvider to Layout

typescript

// app/layout.tsx
import {
  ClerkProvider,
  SignInButton,
  SignUpButton,
  SignedIn,
  SignedOut,
  UserButton,
} from '@clerk/nextjs'
import type { Metadata } from 'next'

export const metadata: Metadata = {
  title: 'My App',
}

export default function RootLayout({
  children,
}: {
  children: React.ReactNode
}) {
  return (
    <ClerkProvider>
      <html lang="en">
        <body>
          <header className="flex justify-end items-center p-4 gap-4 h-16">
            <SignedOut>
              <SignInButton />
              <SignUpButton />
            </SignedOut>
            <SignedIn>
              <UserButton />
            </SignedIn>
          </header>
          {children}
        </body>
      </html>
    </ClerkProvider>
  )
}

5. Run Your App

bash

pnpm dev

Visit

http://localhost:3000

and click "Sign Up" to create your first user.

Key Concepts

proxy.ts vs middleware.ts

Next.js 16 (App Router): Use
```
proxy.ts
```
for Clerk middleware
Next.js ≤15: Use
```
middleware.ts
```
with identical code (filename only differs)
Clerk's
```
clerkMiddleware()
```
function is the same regardless of filename
The
```
matcher
```
configuration ensures proper route handling and performance

Protecting Routes

By default,

clerkMiddleware()

does not protect routes—all are public. Use

auth.protect()

to require authentication:

typescript

// Protect specific route
import { auth } from '@clerk/nextjs/server'

export default async function Page() {
  const { userId } = await auth()
  
  if (!userId) {
    // Redirect handled by clerkMiddleware
  }
  
  return <div>Protected content for {userId}</div>
}

Or protect all routes in

proxy.ts

typescript

import { clerkMiddleware } from '@clerk/nextjs/server'

export default clerkMiddleware(async (auth, req) => {
  await auth.protect()
})

Environment Variable Validation

Check for required Clerk keys before runtime:

typescript

// lib/clerk-config.ts
export function validateClerkEnv() {
  const required = [
    'NEXT_PUBLIC_CLERK_PUBLISHABLE_KEY',
    'CLERK_SECRET_KEY',
  ]
  
  const missing = required.filter(key => !process.env[key])
  
  if (missing.length > 0) {
    throw new Error(`Missing required Clerk environment variables: ${missing.join(', ')}`)
  }
}

Accessing User Data

Use Clerk hooks in client components:

typescript

// app/components/user-profile.tsx
'use client'

import { useUser } from '@clerk/nextjs'

export function UserProfile() {
  const { user, isLoaded } = useUser()
  
  if (!isLoaded) return <div>Loading...</div>
  
  if (!user) return <div>Not signed in</div>
  
  return (
    <div>
      <h1>{user.fullName}</h1>
      <p>{user.primaryEmailAddress?.emailAddress}</p>
    </div>
  )
}

Or in server components/actions:

typescript

// app/actions.ts
'use server'

import { auth, clerkClient } from '@clerk/nextjs/server'

export async function getUserData() {
  const { userId } = await auth()
  
  if (!userId) {
    throw new Error('Unauthorized')
  }
  
  const clerk = await clerkClient()
  const user = await clerk.users.getUser(userId)
  
  return user
}

Migrating from middleware.ts (Next.js 15) to proxy.ts (Next.js 16)

Step-by-Step Migration

Rename the file from
```
middleware.ts
```
to
```
proxy.ts
```
(location remains same: root or
```
/src
```
)

Keep the code identical - No functional changes needed:

typescript

// Before (middleware.ts)
import { clerkMiddleware } from '@clerk/nextjs/server'
export default clerkMiddleware()
export const config = { ... }

// After (proxy.ts) - Same code
import { clerkMiddleware } from '@clerk/nextjs/server'
export default clerkMiddleware()
export const config = { ... }

Update Next.js version:
bash
```
pnpm add next@latest
```
Verify environment variables are still in
```
.env.local
```
(no changes needed)
Test the migration:
bash
```
pnpm dev
```

Troubleshooting Migration

If routes aren't protected, ensure
```
proxy.ts
```
is in the correct location (root or
```
/src
```
)
Check that
```
.env.local
```
has all required Clerk keys
Clear
```
.next
```
cache if middleware changes don't take effect:
```
rm -rf .next && pnpm dev
```
Verify Next.js version is 16.0+:
```
pnpm list next
```

Building an MCP Server with Clerk

See CLERK_MCP_SERVER_SETUP.md for complete MCP server integration.

Quick MCP Setup Summary

Install MCP dependencies:

bash

pnpm add @vercel/mcp-adapter @clerk/mcp-tools

Create MCP route at

app/[transport]/route.ts

typescript

import { verifyClerkToken } from '@clerk/mcp-tools/next'
import { createMcpHandler, withMcpAuth } from '@vercel/mcp-adapter'
import { auth, clerkClient } from '@clerk/nextjs/server'

const clerk = await clerkClient()

const handler = createMcpHandler((server) => {
  server.tool(
    'get-clerk-user-data',
    'Gets data about the Clerk user that authorized this request',
    {},
    async (_, { authInfo }) => {
      const userId = authInfo!.extra!.userId! as string
      const userData = await clerk.users.getUser(userId)
      return {
        content: [{ type: 'text', text: JSON.stringify(userData) }],
      }
    },
  )
})

const authHandler = withMcpAuth(
  handler,
  async (_, token) => {
    const clerkAuth = await auth({ acceptsToken: 'oauth_token' })
    return verifyClerkToken(clerkAuth, token)
  },
  {
    required: true,
    resourceMetadataPath: '/.well-known/oauth-protected-resource/mcp',
  },
)

export { authHandler as GET, authHandler as POST }

Expose OAuth metadata endpoints (see references for complete setup)

Update proxy.ts to exclude

.well-known

endpoints:

typescript

import { clerkMiddleware, createRouteMatcher } from '@clerk/nextjs/server'

const isPublicRoute = createRouteMatcher([
  '/.well-known/oauth-authorization-server(.*)',
  '/.well-known/oauth-protected-resource(.*)',
])

export default clerkMiddleware(async (auth, req) => {
  if (isPublicRoute(req)) return
  await auth.protect()
})

Enable Dynamic Client Registration in Clerk Dashboard

Best Practices

1. Environment Variable Management

Always use
```
.env.local
```
for development (never commit sensitive keys)
Validate environment variables on application startup
Use
```
NEXT_PUBLIC_
```
prefix ONLY for non-sensitive keys that are safe to expose
For production, set environment variables in your deployment platform (Vercel, etc.)

2. Route Protection Strategies

typescript

// Option A: Protect all routes
export default clerkMiddleware(async (auth, req) => {
  await auth.protect()
})

// Option B: Protect specific routes
import { createRouteMatcher } from '@clerk/nextjs/server'

const isProtectedRoute = createRouteMatcher(['/dashboard(.*)', '/api/user(.*)'])

export default clerkMiddleware(async (auth, req) => {
  if (isProtectedRoute(req)) {
    await auth.protect()
  }
})

// Option C: Public routes with opt-in protection
const isPublicRoute = createRouteMatcher(['/sign-in(.*)', '/sign-up(.*)'])

export default clerkMiddleware(async (auth, req) => {
  if (!isPublicRoute(req)) {
    await auth.protect()
  }
})

3. MCP Server Security

Enable Dynamic Client Registration in Clerk Dashboard
Keep
```
.well-known
```
endpoints public but protect all MCP tools with OAuth
Use
```
acceptsToken: 'oauth_token'
```
in
```
auth()
```
to require machine tokens
OAuth tokens are free during public beta (pricing TBD)
Always verify tokens with
```
verifyClerkToken()
```
before exposing user data

4. Performance & Caching

Use
```
clerkClient()
```
for server-side user queries (cached automatically)
Leverage React Server Components for secure user data access
Cache user data when possible to reduce API calls
Use
```
@clerk/nextjs
```
hooks only in Client Components (
```
'use client'
```
)

5. Production Deployment

Set all environment variables in your deployment platform
Use Clerk's production instance keys (not development keys)
Test authentication flow in staging environment before production
Monitor Clerk Dashboard for authentication errors
Keep
```
@clerk/nextjs
```
updated:
```
pnpm update @clerk/nextjs
```

Troubleshooting

Issues & Solutions

Issue	Solution
"Missing environment variables"	Ensure `.env.local` has `NEXT_PUBLIC_CLERK_PUBLISHABLE_KEY` and `CLERK_SECRET_KEY`
Middleware not protecting routes	Verify `proxy.ts` is in root or `/src` directory, not in `app/`
Sign-in/sign-up pages not working	Check `NEXT_PUBLIC_CLERK_SIGN_IN_URL` and `NEXT_PUBLIC_CLERK_SIGN_UP_URL` in `.env.local`
User data returns null	Ensure user is authenticated: check `userId` is not null before calling `getUser()`
MCP server OAuth fails	Enable Dynamic Client Registration in Clerk Dashboard OAuth Applications
Changes not taking effect	Clear `.next` cache: `rm -rf .next` and restart `pnpm dev`
"proxy.ts" not recognized	Verify Next.js version is 16.0+: `pnpm list next`

Common Next.js 16 Gotchas

File naming: Must be
```
proxy.ts
```
(not
```
middleware.ts
```
) for Next.js 16
Location: Place
```
proxy.ts
```
at project root or in
```
/src
```
directory, NOT in
```
app/
```
Re-exports: Config object must be exported from
```
proxy.ts
```
for matcher to work
Async operations:
```
clerkMiddleware()
```
is async-ready; use
```
await auth.protect()
```
for route protection

Debug Mode

Enable debug logging:

typescript

// proxy.ts
import { clerkMiddleware } from '@clerk/nextjs/server'

export default clerkMiddleware((auth, req) => {
  if (process.env.DEBUG_CLERK) {
    console.log('Request URL:', req.nextUrl.pathname)
    console.log('User ID:', auth.sessionClaims?.sub)
  }
})

Run with debug:

bash

DEBUG_CLERK=1 pnpm dev

Related Skills

mcp-server-skills: General MCP server patterns with Vercel adapter
nextjs16-skills: Next.js 16 features, breaking changes, and best practices
authjs-skills: Alternative authentication using Auth.js (Auth0, GitHub, etc.)

clerk-nextjs-skills

NPX Install

Tags

SKILL.md Content

Links

Quick Start

1. Install Dependencies (Using pnpm)

2. Create proxy.ts (Next.js 16)

3. Set Environment Variables

4. Add ClerkProvider to Layout

5. Run Your App

Key Concepts

proxy.ts vs middleware.ts

Protecting Routes

Environment Variable Validation

Accessing User Data

Migrating from middleware.ts (Next.js 15) to proxy.ts (Next.js 16)

Step-by-Step Migration

Troubleshooting Migration

Building an MCP Server with Clerk

Quick MCP Setup Summary

Best Practices

1. Environment Variable Management

2. Route Protection Strategies

3. MCP Server Security

4. Performance & Caching

5. Production Deployment

Troubleshooting

Issues & Solutions

Common Next.js 16 Gotchas

Debug Mode

Related Skills

Resources