React Start (@tanstack/react-start)

This skill builds on start-core. Read start-core first for foundational concepts.

This skill covers the React-specific bindings, setup, and patterns for TanStack Start.

CRITICAL: All code is ISOMORPHIC by default. Loaders run on BOTH server and client. Use createServerFn for server-only logic.

CRITICAL: Do not confuse @tanstack/react-start with Next.js or Remix. They are completely different frameworks with different APIs.

CRITICAL: Types are FULLY INFERRED. Never cast, never annotate inferred values.

Package API Surface

@tanstack/react-start re-exports everything from @tanstack/start-client-core plus:

useServerFn — React hook for calling server functions from components

All core APIs (createServerFn, createMiddleware, createStart, createIsomorphicFn, createServerOnlyFn, createClientOnlyFn) are available from @tanstack/react-start.

Server utilities (getRequest, getRequestHeader, setResponseHeader, setResponseHeaders, setResponseStatus) are imported from @tanstack/react-start/server.

Full Project Setup

1. Install Dependencies

npm i @tanstack/react-start @tanstack/react-router react react-dom
npm i -D vite @vitejs/plugin-react typescript @types/react @types/react-dom

2. package.json

json

{
  "type": "module",
  "scripts": {
    "dev": "vite dev",
    "build": "vite build",
    "start": "node .output/server/index.mjs"
  }
}

3. tsconfig.json

json

{
  "compilerOptions": {
    "jsx": "react-jsx",
    "moduleResolution": "Bundler",
    "module": "ESNext",
    "target": "ES2022",
    "skipLibCheck": true,
    "strictNullChecks": true
  }
}

4. vite.config.ts

import { defineConfig } from 'vite'
import { tanstackStart } from '@tanstack/react-start/plugin/vite'
import viteReact from '@vitejs/plugin-react'

export default defineConfig({
  plugins: [
    tanstackStart(), // MUST come before react()
    viteReact(),
  ],
})

5. Router Factory (src/router.tsx)

tsx

import { createRouter } from '@tanstack/react-router'
import { routeTree } from './routeTree.gen'

export function getRouter() {
  const router = createRouter({
    routeTree,
    scrollRestoration: true,
  })
  return router
}

6. Root Route (src/routes/__root.tsx)

tsx

import type { ReactNode } from 'react'
import {
  Outlet,
  createRootRoute,
  HeadContent,
  Scripts,
} from '@tanstack/react-router'

export const Route = createRootRoute({
  head: () => ({
    meta: [
      { charSet: 'utf-8' },
      { name: 'viewport', content: 'width=device-width, initial-scale=1' },
      { title: 'My TanStack Start App' },
    ],
  }),
  component: RootComponent,
})

function RootComponent() {
  return (
    <RootDocument>
      <Outlet />
    </RootDocument>
  )
}

function RootDocument({ children }: Readonly<{ children: ReactNode }>) {
  return (
    <html>
      <head>
        <HeadContent />
      </head>
      <body>
        {children}
        <Scripts />
      </body>
    </html>
  )
}

7. Index Route (src/routes/index.tsx)

tsx

import { createFileRoute } from '@tanstack/react-router'
import { createServerFn } from '@tanstack/react-start'

const getGreeting = createServerFn({ method: 'GET' }).handler(async () => {
  return 'Hello from TanStack Start!'
})

export const Route = createFileRoute('/')({
  loader: () => getGreeting(),
  component: HomePage,
})

function HomePage() {
  const greeting = Route.useLoaderData()
  return <h1>{greeting}</h1>
}

useServerFn Hook

Use useServerFn to call server functions from React components with proper integration:

tsx

import { createServerFn, useServerFn } from '@tanstack/react-start'

const updatePost = createServerFn({ method: 'POST' })
  .inputValidator((data: { id: string; title: string }) => data)
  .handler(async ({ data }) => {
    await db.posts.update(data.id, { title: data.title })
    return { success: true }
  })

function EditPostForm({ postId }: { postId: string }) {
  const updatePostFn = useServerFn(updatePost)
  const [title, setTitle] = useState('')

  return (
    <form
      onSubmit={async (e) => {
        e.preventDefault()
        await updatePostFn({ data: { id: postId, title } })
      }}
    >
      <input value={title} onChange={(e) => setTitle(e.target.value)} />
      <button type="submit">Save</button>
    </form>
  )
}

Global Start Configuration (src/start.ts)

tsx

import { createStart, createMiddleware } from '@tanstack/react-start'

const requestLogger = createMiddleware().server(async ({ next, request }) => {
  console.log(`${request.method} ${request.url}`)
  return next()
})

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

React-Specific Components

All routing components from @tanstack/react-router work in Start:

<RouterProvider> — not needed in Start (handled automatically)
<Outlet> — renders matched child route
<Link> — type-safe navigation
<Navigate> — declarative redirect
<HeadContent> — renders head tags (must be in <head>)
<Scripts> — renders body scripts (must be in <body>)
<Await> — renders deferred data with Suspense
<ClientOnly> — renders children only after hydration
<CatchBoundary> — error boundary

Hooks Reference

All hooks from @tanstack/react-router work in Start:

useRouter() — router instance
useRouterState() — subscribe to router state
useNavigate() — programmatic navigation
useSearch({ from }) — validated search params
useParams({ from }) — path params
useLoaderData({ from }) — loader data
useMatch({ from }) — full route match
useRouteContext({ from }) — route context
Route.useLoaderData() — typed loader data (preferred in route files)
Route.useSearch() — typed search params (preferred in route files)

Common Mistakes

1. CRITICAL: Importing from wrong package

tsx

// WRONG — this is the SPA router, NOT Start
import { createServerFn } from '@tanstack/react-router'

// CORRECT — server functions come from react-start
import { createServerFn } from '@tanstack/react-start'

// CORRECT — routing APIs come from react-router (re-exported by Start too)
import { createFileRoute, Link } from '@tanstack/react-router'

2. HIGH: Using React hooks in beforeLoad or loader

tsx

// WRONG — beforeLoad/loader are NOT React components
beforeLoad: () => {
  const auth = useAuth() // React hook, cannot be used here
}

// CORRECT — pass state via router context
const rootRoute = createRootRouteWithContext<{ auth: AuthState }>()({})

3. HIGH: Missing Scripts component

Without <Scripts /> in the root route's <body>, client JavaScript doesn't load and the app won't hydrate.

Cross-References

start-core — core Start concepts
router-core — routing fundamentals
react-router — React Router hooks and components