clerk-core-workflow-b by jeremylongshore

---
name: clerk-core-workflow-b
description: |
  Implement session management and middleware with Clerk.
  Use when managing user sessions, configuring route protection,
  or implementing token refresh and custom JWT templates.
  Trigger with phrases like "clerk session", "clerk middleware",
  "clerk route protection", "clerk token", "clerk JWT".
allowed-tools: Read, Write, Edit, Grep
version: 1.0.0
license: MIT
author: Jeremy Longshore <[email protected]>
compatible-with: claude-code, codex, openclaw
tags: [saas, clerk, clerk-core, sessions, middleware]
---
# Clerk Core Workflow B: Session & Middleware

## Overview
Implement session management and route protection with Clerk middleware. Covers `clerkMiddleware()` configuration, `auth()` patterns, custom session claims, JWT templates for external services, organization-scoped sessions, and session token v2.

## Prerequisites
- `@clerk/nextjs` installed with ClerkProvider wrapping the app
- Next.js 14+ with App Router
- Sign-in/sign-up flows working (`clerk-core-workflow-a` completed)

## Instructions

### Step 1: Configure clerkMiddleware with Route Matchers
```typescript
// middleware.ts (project root)
import { clerkMiddleware, createRouteMatcher } from '@clerk/nextjs/server'

const isPublicRoute = createRouteMatcher([
  '/',
  '/sign-in(.*)',
  '/sign-up(.*)',
  '/api/webhooks(.*)',
  '/pricing',
  '/blog(.*)',
])

const isAdminRoute = createRouteMatcher(['/admin(.*)'])
const isApiRoute = createRouteMatcher(['/api(.*)'])

export default clerkMiddleware(async (auth, req) => {
  // Public routes: no auth required
  if (isPublicRoute(req)) return

  // Admin routes: require org:admin role
  if (isAdminRoute(req)) {
    await auth.protect({ role: 'org:admin' })
    return
  }

  // All other routes: require authentication
  await auth.protect()
})

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)(.*)',
  ],
}
```

**Key behavior:** `clerkMiddleware()` does NOT protect any routes by default. You must explicitly call `auth.protect()` for routes that require authentication. This is a design decision to avoid over-blocking.

### Step 2: Protect API Routes with auth()
```typescript
// app/api/data/route.ts
import { auth } from '@clerk/nextjs/server'

export async function GET() {
  const { userId, orgId, has } = await auth()

  if (!userId) {
    return Response.json({ error: 'Unauthorized' }, { status: 401 })
  }

  // Permission-based authorization
  if (!has({ permission: 'org:data:read' })) {
    return Response.json({ error: 'Forbidden' }, { status: 403 })
  }

  const data = orgId
    ? await db.items.findMany({ where: { organizationId: orgId } })
    : await db.items.findMany({ where: { ownerId: userId } })

  return Response.json({ data, userId, orgId })
}

export async function POST(req: Request) {
  const { userId, orgId, has } = await auth()
  if (!userId) return Response.json({ error: 'Unauthorized' }, { status: 401 })
  if (!has({ permission: 'org:data:write' })) {
    return Response.json({ error: 'Forbidden' }, { status: 403 })
  }

  const body = await req.json()
  const item = await db.items.create({
    data: { ...body, ownerId: userId, organizationId: orgId },
  })
  return Response.json({ item }, { status: 201 })
}
```

### Step 3: Server Component Auth Patterns
```typescript
// app/dashboard/page.tsx
import { auth, currentUser } from '@clerk/nextjs/server'
import { redirect } from 'next/navigation'

export default async function DashboardPage() {
  const { userId, orgId, orgRole, has, sessionClaims } = await auth()
  if (!userId) redirect('/sign-in')

  // auth() is free (JWT parsing) — use for lightweight checks
  const isAdmin = has({ role: 'org:admin' })

  // currentUser() costs a Backend API call — use only when you need full profile
  const user = await currentUser()

  return (
    <div>
      <h1>Welcome, {user?.firstName}</h1>
      <p>Organization: {orgId || 'Personal account'}</p>
      <p>Role: {orgRole || 'N/A'}</p>
      {isAdmin && <a href="/admin">Admin Panel</a>}
    </div>
  )
}
```

### Step 4: Custom Session Claims
Customize in **Dashboard > Sessions > Customize session token:**

```json
{
  "metadata": "{{user.public_metadata}}",
  "email": "{{user.primary_email_address}}"
}
```

Then declare types and access in code:
```typescript
// types/clerk.d.ts
declare global {
  interface CustomJwtSessionClaims {
    metadata?: {
      role?: string
      plan?: string
    }
    email?: string
  }
}
export {}
```

```typescript
// Access custom claims (no API call needed — embedded in JWT)
import { auth } from '@clerk/nextjs/server'

export async function GET() {
  const { sessionClaims } = await auth()

  const userPlan = sessionClaims?.metadata?.plan || 'free'
  const userEmail = sessionClaims?.email

  return Response.json({ plan: userPlan, email: userEmail })
}
```

**Warning:** Session token cookie limit is 4KB. Custom claims should be under 1.2KB. Store large data in your database, not in session claims.

### Step 5: JWT Templates for External Services
```typescript
// app/api/supabase-data/route.ts
import { auth } from '@clerk/nextjs/server'
import { createClient } from '@supabase/supabase-js'

export async function GET() {
  const { userId, getToken } = await auth()
  if (!userId) return Response.json({ error: 'Unauthorized' }, { status: 401 })

  // Get a JWT with Supabase-compatible claims
  // Configure the template in Dashboard > JWT Templates
  const supabaseToken = await getToken({ template: 'supabase' })

  const supabase = createClient(
    process.env.NEXT_PUBLIC_SUPABASE_URL!,
    process.env.NEXT_PUBLIC_SUPABASE_ANON_KEY!,
    { global: { headers: { Authorization: `Bearer ${supabaseToken}` } } }
  )

  const { data } = await supabase.from('items').select('*')
  return Response.json({ data })
}
```

Configure JWT template in **Dashboard > JWT Templates > New template**:
```json
{
  "sub": "{{user.id}}",
  "email": "{{user.primary_email_address}}",
  "role": "authenticated",
  "aud": "authenticated"
}
```

### Step 6: Organization-Scoped Sessions
```typescript
'use client'
import { useOrganizationList, useOrganization, useAuth } from '@clerk/nextjs'

export function OrgSwitcher() {
  const { organizationList, setActive, isLoaded } = useOrganizationList({
    userMemberships: { infinite: true },
  })
  const { organization } = useOrganization()

  if (!isLoaded) return <div>Loading orgs...</div>

  return (
    <div>
      <p>Active: {organization?.name || 'Personal account'}</p>
      <ul>
        {organizationList?.map(({ organization: org, membership }) => (
          <li key={org.id}>
            <button onClick={() => setActive({ organization: org.id })}>
              {org.name} ({membership.role})
            </button>
          </li>
        ))}
        <li>
          <button onClick={() => setActive({ organization: null })}>
            Personal account
          </button>
        </li>
      </ul>
    </div>
  )
}
```

### Step 7: Server Action Permission Guards
```typescript
'use server'
import { auth } from '@clerk/nextjs/server'

export async function deleteItem(itemId: string) {
  const { userId, orgId, has } = await auth()
  if (!userId) throw new Error('Unauthorized')
  if (!has({ permission: 'org:data:delete' })) {
    throw new Error('You do not have permission to delete items')
  }

  await db.items.delete({ where: { id: itemId, organizationId: orgId } })
  return { success: true }
}

export async function updateOrgSettings(settings: Record<string, any>) {
  const { orgId, has } = await auth()
  if (!orgId) throw new Error('No organization selected')
  if (!has({ role: 'org:admin' })) {
    throw new Error('Only admins can update organization settings')
  }

  await db.orgSettings.upsert({
    where: { orgId },
    update: settings,
    create: { orgId, ...settings },
  })
  return { success: true }
}
```

## Error Handling
| Issue | Cause | Solution |
|-------|-------|----------|
| Middleware redirect loop | Sign-in page not in `isPublicRoute` | Add `/sign-in(.*)` to public route matcher |
| 401 on API route | Token not forwarded | Include credentials in fetch or use server-side `auth()` |
| `orgId` is null | No active organization | Prompt user with `<OrganizationSwitcher />` |
| `has()` always false | Permission not assigned to role | Check Dashboard > Organizations > Roles |
| Session expired | Token TTL exceeded | Clerk auto-refreshes; if stuck, clear cookies |
| `auth() was called but clerkMiddleware() not detected` | Middleware missing or wrong location | Ensure `middleware.ts` at project root |

## Enterprise Considerations
- Session token v2 (default since April 2025) is more compact -- if your downstream services parse JWTs, verify they handle the new format
- `auth.protect()` in middleware returns a 401/redirect before reaching your route handler -- this is more efficient than checking `userId` in every route
- For permission-based access, prefer `has({ permission: '...' })` over `has({ role: '...' })` -- permissions decouple authorization from role names
- JWT templates support custom `iss`, `aud`, and `exp` claims for integrating with Hasura, Supabase, Convex, Neon, and other services
- Organization switching changes the active session scope instantly -- no page reload needed

## Resources
- [clerkMiddleware() Reference](https://clerk.com/docs/reference/nextjs/clerk-middleware)
- [auth() Reference](https://clerk.com/docs/reference/nextjs/app-router/auth)
- [Custom Session Tokens](https://clerk.com/docs/guides/sessions/customize-session-tokens)
- [JWT Templates](https://clerk.com/docs/guides/sessions/jwt-templates)

## Next Steps
Proceed to `clerk-webhooks-events` for webhook and event handling.