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:

Server layer — createServerFn + auth() from @clerk/tanstack-react-start/server
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

Docs

TanStack React Start SDK

clerk-tanstack-patterns