---name: clerk-tanstack-patternsdescription: TanStack React Start auth patterns with @clerk/tanstack-react-start- createServerFn, beforeLoad guards, loaders, Vinxi server. Triggers on: TanStacklicense: MITallowed-tools: WebFetchmetadata: author: clerkversion: 1.0.0---

TanStack React Start Patterns

What Do You Need?

Task	Reference
Protect routes with beforeLoad	references/router-guards.md
Auth in createServerFn	references/server-functions.md
Pass auth to loaders	references/loaders.md
Configure Vinxi + clerkMiddleware	references/vinxi-server.md

References

Reference	Description
references/router-guards.md	beforeLoad auth redirect
references/server-functions.md	createServerFn with auth()
references/loaders.md	Auth context in loaders
references/vinxi-server.md	clerkMiddleware() setup

Setup

npm install @clerk/tanstack-react-start

.env:

CLERK_PUBLISHABLE_KEY=pk_...
CLERK_SECRET_KEY=sk_...

src/start.ts (Vinxi entry):

import { clerkMiddleware } from '@clerk/tanstack-react-start/server'
import { createStart } from '@tanstack/react-start'

export const startInstance = createStart(() => {
  return {
    requestMiddleware: [clerkMiddleware()],
  }
})

src/routes/__root.tsx — wrap with <ClerkProvider>:

import { ClerkProvider } from '@clerk/tanstack-react-start'

function RootDocument({ children }: { children: React.ReactNode }) {
  return (
    <html lang="en">
      <body>
        <ClerkProvider>
          {children}
        </ClerkProvider>
      </body>
    </html>
  )
}

Mental Model

TanStack Start runs on Vinxi. Auth flows through two layers:

1. Server layer — createServerFn + auth() from @clerk/tanstack-react-start/server
2. Router layer — beforeLoad on route definitions, throws redirect for unauthenticated

Both layers are server-executed. Client hooks (useAuth, useUser) are React hooks for the browser side.

Minimal Pattern

import { createFileRoute, redirect } from '@tanstack/react-router'
import { createServerFn } from '@tanstack/react-start'
import { auth } from '@clerk/tanstack-react-start/server'

const authStateFn = createServerFn().handler(async () => {
  const { isAuthenticated, userId } = await auth()
  if (!isAuthenticated) {
    throw redirect({ to: '/sign-in' })
  }
  return { userId }
})

export const Route = createFileRoute('/dashboard')({
  beforeLoad: async () => await authStateFn(),
})

Common Pitfalls

Symptom	Cause	Fix
auth() returns empty	Missing clerkMiddleware in start.ts	Add to requestMiddleware array
redirect not thrown	Using return instead of throw	throw redirect(...) in TanStack
Wrong import for auth	Mixing client/server imports	Server: @clerk/tanstack-react-start/server
Loader context missing userId	Not passing from beforeLoad	Return from beforeLoad, access via context
ClerkProvider missing	Forgot root wrapping	Add to __root.tsx shell component

See Also

• clerk-setup - Initial Clerk install
• clerk-custom-ui - Custom flows & appearance
• clerk-orgs - B2B organizations

Docs

TanStack React Start SDK