Clerk Nextjs Patterns Agent Skill

Next.js Patterns

> 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.

For basic setup, see clerk-setup skill.

What Do You Need?

| Task | Reference |

|------|-----------|

| Server vs client auth (auth() vs hooks) | references/server-vs-client.md |

| Configure middleware (public-first vs protected-first) | references/middleware-strategies.md |

| Protect Server Actions | references/server-actions.md |

| API route auth (401 vs 403) | references/api-routes.md |

| Cache auth data (user-scoped caching) | references/caching-auth.md |

References

| Reference | Description |

|-----------|-------------|

| references/server-vs-client.md | await auth() vs hooks |

| references/middleware-strategies.md | Public-first vs protected-first, proxy.ts (Next.js <=15: middleware.ts) |

| references/server-actions.md | Protect mutations |

| references/api-routes.md | 401 vs 403 |

| references/caching-auth.md | User-scoped caching |

Mental Model

Server vs Client = different auth APIs:

• Server: await auth() from @clerk/nextjs/server (async!)
• Client: useAuth() hook from @clerk/nextjs (sync)

Never mix them. Server Components use server imports, Client Components use hooks.

Key properties from auth():

• isAuthenticated — boolean, replaces the !!userId pattern
• sessionStatus — 'active' | 'pending', for detecting incomplete session tasks
• userId, orgId, orgSlug, has(), protect() — unchanged

> Core 2 ONLY (skip if current SDK): isAuthenticated and sessionStatus are not available. Check !!userId instead.

Minimal Pattern

// Server Component
import { auth } from '@clerk/nextjs/server'

export default async function Page() {
  const { isAuthenticated, userId } = await auth()  // MUST await!
  if (!isAuthenticated) return <p>Not signed in</p>
  return <p>Hello {userId}</p>
}

> Core 2 ONLY (skip if current SDK): isAuthenticated is not available. Use if (!userId) instead.

Conditional Rendering with <Show>

For client-side conditional rendering based on auth state. <Show> covers both authentication checks and authorization (feature, plan, role, permission) in one component.

Authentication check:

import { Show } from '@clerk/nextjs'

<Show when="signed-in" fallback={<p>Please sign in</p>}>
  <Dashboard />
</Show>

Authorization checks (B2B):

// Feature-based (preferred — features can move between plans without redeploy)
<Show when={{ feature: 'analytics' }} fallback={<UpgradePrompt />}>
  <AnalyticsDashboard />
</Show>

// Permission-based (preferred over role-based for granular access)
<Show when={{ permission: 'org:invoices:create' }}>
  <NewInvoiceButton />
</Show>

// Plan-based (tier-level gating)
<Show when={{ plan: 'pro' }}>
  <ProFeatures />
</Show>

// Role-based (use sparingly — prefer permission)
<Show when={{ role: 'org:admin' }}>
  <AdminPanel />
</Show>

Callback for complex logic:

<Show when={(has) => has({ role: 'org:admin' }) || has({ role: 'org:billing_manager' })}>
  <BillingActions />
</Show>

> Core 2 ONLY (skip if current SDK): <Show> does not exist. For authentication, use <SignedIn> and <SignedOut>. For authorization (role / permission), use <Protect> with the same prop names (role, permission, condition). Feature- and plan-based variants require Core 3. See clerk-custom-ui skill, core-3/show-component.md for the full migration table.

Common Pitfalls

| Symptom | Cause | Fix |

|---------|-------|-----|

| undefined userId in Server Component | Missing await | await auth() not auth() |

| Auth not working on API routes | Missing matcher | Add '/(api|trpc)(.*)' to proxy.ts (Next.js <=15: middleware.ts) |

| Cache returns wrong user's data | Missing userId in key | Include userId in unstable_cache key |

| Mutations bypass auth | Unprotected Server Action | Check auth() at start of action |

| Wrong HTTP error code | Confused 401/403 | 401 = not signed in, 403 = no permission |

Session Tokens & Custom JWTs

getToken() for external APIs

Pass a custom JWT to third-party services (Hasura, Supabase, etc.) using JWT templates defined in the Clerk dashboard.

Server-side (Server Component or Route Handler):

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

export default async function Page() {
  const { getToken } = await auth()
  const token = await getToken({ template: 'hasura' })
  if (!token) return <p>Not authenticated</p>

  const res = await fetch('https://api.example.com/graphql', {
    headers: { Authorization: `Bearer ${token}` },
  })
  const data = await res.json()
  return <pre>{JSON.stringify(data)}</pre>
}

Client-side (Client Component):

'use client'
import { useAuth } from '@clerk/nextjs'

export function DataFetcher() {
  const { getToken } = useAuth()

  async function fetchData() {
    const token = await getToken({ template: 'supabase' })
    if (!token) return

    const res = await fetch('https://api.example.com/data', {
      headers: { Authorization: `Bearer ${token}` },
    })
    return res.json()
  }

  return <button onClick={fetchData}>Fetch</button>
}

getToken() returns null when the user is not authenticated — always null-check before use.

useSession() for session data

Access session metadata in client components:

'use client'
import { useSession } from '@clerk/nextjs'

export function SessionInfo() {
  const { session } = useSession()
  if (!session) return null

  return (
    <p>
      Session {session.id} — last active: {session.lastActiveAt.toISOString()}
    </p>
  )
}

Manual JWT verification (no Clerk middleware)

For standalone API servers that receive Clerk session tokens from the Authorization header or the __session cookie (same-origin).

Using @clerk/backend verifyToken (recommended):

import { verifyToken } from '@clerk/backend'

const token = req.headers.authorization?.replace('Bearer ', '')
if (!token) return res.status(401).json({ error: 'No token' })

try {
  const claims = await verifyToken(token, {
    jwtKey: process.env.CLERK_JWT_KEY,
  })
  // claims.sub = userId
} catch {
  return res.status(401).json({ error: 'Invalid token' })
}

Using jsonwebtoken (when you can't use @clerk/backend):

import jwt from 'jsonwebtoken'

const publicKey = process.env.CLERK_PEM_PUBLIC_KEY!.replace(/\\n/g, '\n')
const token = req.headers.authorization?.replace('Bearer ', '')
if (!token) return res.status(401).json({ error: 'No token' })

try {
  const claims = jwt.verify(token, publicKey, { algorithms: ['RS256'] }) as jwt.JwtPayload
  // Manually check exp and nbf (jsonwebtoken does this automatically, but verify azp if needed)
  // claims.sub = userId
} catch {
  return res.status(401).json({ error: 'Invalid or expired token' })
}

Token sources:

• Same-origin requests: __session cookie (Clerk sets this automatically)
• Cross-origin / mobile / API-to-API: Authorization: Bearer <token> header

> CRITICAL: Always check exp and nbf claims. verifyToken from @clerk/backend handles this automatically; with raw jsonwebtoken, set ignoreExpiration: false (default) and ensure clockTolerance is minimal.

See Also

• clerk-setup - Initial Clerk install
• clerk-orgs - B2B patterns (active org, role/permission gating)
• clerk-billing - Plan and feature entitlements with has()
• clerk-webhooks - Sync user/org events to your database
• clerk-custom-ui - Theming and customization for built-in components

Docs

Next.js SDK