TanStack Router - Claude MCP Skill

# TanStack Router

Type-safe, file-based routing for React SPAs with route-level data loading and TanStack Query integration

---

## Quick Start

**Last Updated**: 2026-01-09
**Version**: @tanstack/react-router@1.146.2

```bash
npm install @tanstack/react-router @tanstack/router-devtools
npm install -D @tanstack/router-plugin
# Optional: Zod validation adapter
npm install @tanstack/zod-adapter zod
```

**Vite Config** (TanStackRouterVite MUST come before react()):
```typescript
// vite.config.ts
import { TanStackRouterVite } from '@tanstack/router-plugin/vite'

export default defineConfig({
  plugins: [TanStackRouterVite(), react()], // Order matters!
})
```

**File Structure**:
```
src/routes/
├── __root.tsx         → createRootRoute() with <Outlet />
├── index.tsx          → createFileRoute('/')
└── posts.$postId.tsx  → createFileRoute('/posts/$postId')
```

**App Setup**:
```typescript
import { createRouter, RouterProvider } from '@tanstack/react-router'
import { routeTree } from './routeTree.gen' // Auto-generated by plugin

const router = createRouter({ routeTree })
<RouterProvider router={router} />
```

---

## Core Patterns

**Type-Safe Navigation** (routes auto-complete, params typed):
```typescript
<Link to="/posts/$postId" params={{ postId: '123' }} />
<Link to="/invalid" /> // ❌ TypeScript error
```

**Route Loaders** (data fetching before render):
```typescript
export const Route = createFileRoute('/posts/$postId')({
  loader: async ({ params }) => ({ post: await fetchPost(params.postId) }),
  component: ({ useLoaderData }) => {
    const { post } = useLoaderData() // Fully typed!
    return <h1>{post.title}</h1>
  },
})
```

**TanStack Query Integration** (prefetch + cache):
```typescript
const postOpts = (id: string) => queryOptions({
  queryKey: ['posts', id],
  queryFn: () => fetchPost(id),
})

export const Route = createFileRoute('/posts/$postId')({
  loader: ({ context: { queryClient }, params }) =>
    queryClient.ensureQueryData(postOpts(params.postId)),
  component: () => {
    const { postId } = Route.useParams()
    const { data } = useQuery(postOpts(postId))
    return <h1>{data.title}</h1>
  },
})
```

---

## Virtual File Routes (v1.140+)

Programmatic route configuration when file-based conventions don't fit your needs:

**Install**: `npm install @tanstack/virtual-file-routes`

**Vite Config**:
```typescript
import { tanstackRouter } from '@tanstack/router-plugin/vite'

export default defineConfig({
  plugins: [
    tanstackRouter({
      target: 'react',
      virtualRouteConfig: './routes.ts', // Point to your routes file
    }),
    react(),
  ],
})
```

**routes.ts** (define routes programmatically):
```typescript
import { rootRoute, route, index, layout, physical } from '@tanstack/virtual-file-routes'

export const routes = rootRoute('root.tsx', [
  index('home.tsx'),
  route('/posts', 'posts/posts.tsx', [
    index('posts/posts-home.tsx'),
    route('$postId', 'posts/posts-detail.tsx'),
  ]),
  layout('first', 'layout/first-layout.tsx', [
    route('/nested', 'nested.tsx'),
  ]),
  physical('/classic', 'file-based-subtree'), // Mix with file-based
])
```

**Use Cases**: Custom route organization, mixing file-based and code-based, complex nested layouts.

---

## Search Params Validation (Zod Adapter)

Type-safe URL search params with runtime validation:

**Basic Pattern** (inline validation):
```typescript
import { z } from 'zod'

export const Route = createFileRoute('/products')({
  validateSearch: (search) => z.object({
    page: z.number().catch(1),
    filter: z.string().catch(''),
    sort: z.enum(['newest', 'oldest', 'price']).catch('newest'),
  }).parse(search),
})
```

**Recommended Pattern** (Zod adapter with fallbacks):
```typescript
import { zodValidator, fallback } from '@tanstack/zod-adapter'
import { z } from 'zod'

const searchSchema = z.object({
  query: z.string().min(1).max(100),
  page: fallback(z.number().int().positive(), 1),
  sortBy: z.enum(['name', 'date', 'relevance']).optional(),
})

export const Route = createFileRoute('/search')({
  validateSearch: zodValidator(searchSchema),
  // Type-safe: Route.useSearch() returns typed params
})
```

**Why `.catch()` over `.default()`**: Use `.catch()` to silently fix malformed params. Use `.default()` + `errorComponent` to show validation errors.

---

## Error Boundaries

Handle errors at route level with typed error components:

**Route-Level Error Handling**:
```typescript
export const Route = createFileRoute('/posts/$postId')({
  loader: async ({ params }) => {
    const post = await fetchPost(params.postId)
    if (!post) throw new Error('Post not found')
    return { post }
  },
  errorComponent: ({ error, reset }) => (
    <div>
      <p>Error: {error.message}</p>
      <button onClick={reset}>Retry</button>
    </div>
  ),
})
```

**Default Error Component** (global fallback):
```typescript
const router = createRouter({
  routeTree,
  defaultErrorComponent: ({ error }) => (
    <div className="error-page">
      <h1>Something went wrong</h1>
      <p>{error.message}</p>
    </div>
  ),
})
```

**Not Found Handling**:
```typescript
export const Route = createFileRoute('/posts/$postId')({
  notFoundComponent: () => <div>Post not found</div>,
})
```

---

## Authentication with beforeLoad

Protect routes before they load (no flash of protected content):

**Single Route Protection**:
```typescript
import { redirect } from '@tanstack/react-router'

export const Route = createFileRoute('/dashboard')({
  beforeLoad: async ({ context }) => {
    if (!context.auth.isAuthenticated) {
      throw redirect({
        to: '/login',
        search: { redirect: location.pathname }, // Save for post-login
      })
    }
  },
})
```

**Protect Multiple Routes** (layout route pattern):
```typescript
// routes/(authenticated)/route.tsx - protects all children
export const Route = createFileRoute('/(authenticated)')({
  beforeLoad: async ({ context }) => {
    if (!context.auth.isAuthenticated) {
      throw redirect({ to: '/login' })
    }
  },
})
```

**Passing Auth Context** (from React hooks):
```typescript
// main.tsx - pass auth state to router
function App() {
  const auth = useAuth() // Your auth hook

  return (
    <RouterProvider
      router={router}
      context={{ auth }} // Available in beforeLoad
    />
  )
}
```

---

## Known Issues Prevention

This skill prevents **20** documented issues:

### Issue #1: Devtools Dependency Resolution
- **Error**: Build fails with `@tanstack/router-devtools-core` not found
- **Fix**: `npm install @tanstack/router-devtools`

**Issue #2: Vite Plugin Order** (CRITICAL)
- **Error**: Routes not auto-generated, `routeTree.gen.ts` missing
- **Fix**: TanStackRouterVite MUST come before react() in plugins array
- **Why**: Plugin processes route files before React compilation

**Issue #3: Type Registration Missing**
- **Error**: `<Link to="...">` not typed, no autocomplete
- **Fix**: Import `routeTree` from `./routeTree.gen` in main.tsx to register types

**Issue #4: Loader Not Running**
- **Error**: Loader function not called on navigation
- **Fix**: Ensure route exports `Route` constant: `export const Route = createFileRoute('/path')({ loader: ... })`

**Issue #5: Memory Leak with TanStack Form** (FIXED)
- **Error**: Production crashes when using TanStack Form + Router
- **Source**: GitHub Issue #5734 (closed Jan 5, 2026)
- **Resolution**: Fixed in latest versions of @tanstack/form and @tanstack/react-start. Update both packages to resolve.

**Issue #6: Virtual Routes Index/Layout Conflict**
- **Error**: route.tsx and index.tsx conflict when using `physical()` in virtual routing
- **Source**: GitHub Issue #5421
- **Fix**: Use pathless route instead: `_layout.tsx` + `_layout.index.tsx`

**Issue #7: Search Params Type Inference**
- **Error**: Type inference not working with `zodSearchValidator`
- **Source**: GitHub Issue #3100 (regression since v1.81.5)
- **Fix**: Use `zodValidator` from `@tanstack/zod-adapter` instead

**Issue #8: TanStack Start Validators on Reload**
- **Error**: `validateSearch` not working on page reload in TanStack Start
- **Source**: GitHub Issue #3711
- **Note**: Works on client-side navigation, fails on direct page load

### Issue #9: Server Function Validation Errors Lose Structure

**Error**: `inputValidator` Zod errors stringified, losing structure on client
**Source**: [GitHub Issue #6428](https://github.com/TanStack/router/issues/6428)
**Why It Happens**: TanStack Start server function error serialization converts Zod issues array to JSON string in `error.message`, making it unusable without manual parsing.

**Prevention**:
```typescript
// Server function with input validation
export const myFn = createServerFn({ method: 'POST' })
  .inputValidator(z.object({
    name: z.string().min(2),
    age: z.number().min(18),
  }))
  .handler(async ({ data }) => data)

// Client: Workaround to parse stringified issues
try {
  await mutation.mutate({ data: invalidData })
} catch (error) {
  if (error.message.startsWith('[')) {
    const issues = JSON.parse(error.message)
    // Now can use structured error data
    issues.forEach(issue => {
      console.log(issue.path, issue.message)
    })
  }
}
```

**Official Status**: Known issue, tracking PR for fix

### Issue #10: useParams({ strict: false }) Returns Unparsed Values

**Error**: Params typed as parsed but returned as strings after navigation
**Source**: [GitHub Issue #6385](https://github.com/TanStack/router/issues/6385)
**Why It Happens**: In v1.147.3+, `match.params` is no longer parsed when using `strict: false`. First render works correctly, but after navigation values are stored as strings instead of parsed types.

**Prevention**:
```typescript
// Route with param parsing
export const Route = createFileRoute('/posts/$postId')({
  params: {
    parse: (params) => ({
      postId: z.coerce.number().parse(params.postId),
    }),
  },
})

// Component: Use strict mode (default) for parsed params
function Component() {
  const { postId } = useParams() // ✓ Parsed as number
  // const { postId } = useParams({ strict: false }) // ✗ String!

  // Or manually parse when using strict: false
  const params = useParams({ strict: false })
  const postId = Number(params.postId)
}
```

**Official Status**: Known issue, workaround required

### Issue #11: Pathless Route notFoundComponent Not Rendering

**Error**: `notFoundComponent` on pathless layout routes ignored
**Source**: [GitHub Issue #6351](https://github.com/TanStack/router/issues/6351), [GitHub Issue #4065](https://github.com/TanStack/router/issues/4065)
**Why It Happens**: Pathless routes (e.g., `routes/(authenticated)/route.tsx`) don't render their `notFoundComponent`. Instead, the `defaultNotFoundComponent` from router config is triggered. This has been broken since April 2025.

**Prevention**:
```typescript
// ✗ Doesn't work: notFoundComponent on pathless layout
export const Route = createFileRoute('/(authenticated)')({
  beforeLoad: ({ context }) => {
    if (!context.auth) throw redirect({ to: '/login' })
  },
  notFoundComponent: () => <div>Protected 404</div>, // Not rendered!
})

// ✓ Works: Define on child routes instead
export const Route = createFileRoute('/(authenticated)/dashboard')({
  notFoundComponent: () => <div>Protected 404</div>,
})
```

**Official Status**: Known issue, workaround required

### Issue #12: Aborted Loader Renders errorComponent with Undefined Error

**Error**: Rapid navigation aborts previous loader and renders errorComponent with `undefined` error
**Source**: [GitHub Issue #6388](https://github.com/TanStack/router/issues/6388)
**Why It Happens**: Side effect introduced after PR #4570. When user rapidly navigates (e.g., clicking through list items), aborted fetch requests trigger errorComponent without passing the abort error.

**Prevention**:
```typescript
export const Route = createFileRoute('/posts/$postId')({
  loader: async ({ params, abortController }) => {
    await fetch(`/api/posts/${params.postId}`, {
      signal: abortController.signal,
    })
  },
  errorComponent: ({ error, reset }) => {
    // Check for undefined error (aborted request)
    if (!error) {
      return null // Or show loading state
    }
    return <div>Error: {error.message}</div>
  },
})
```

**Official Status**: Known issue, workaround required

### Issue #13: Vitest Cannot Read Properties of Null (useState)

**Error**: `Cannot read properties of null (reading 'useState')` when running tests with Vitest
**Source**: [GitHub Issue #6262](https://github.com/TanStack/router/issues/6262), [PR #6074](https://github.com/TanStack/router/pull/6074)
**Why It Happens**: TanStack Start's `tanstackStart()` plugin conflicts with Vitest's React hooks rendering. This is a known duplicate issue with a PR in progress.

**Prevention**:
```typescript
// Temporary workaround: Comment out tanstackStart() for tests
// vite.config.ts
export default defineConfig({
  plugins: [
    // tanstackStart(), // Disable for tests
    react(),
  ],
  test: { environment: 'jsdom' },
})
```

**Official Status**: PR #6074 in progress to fix

### Issue #14: Throwing Error in Streaming SSR Loader Crashes Dev Server

**Error**: Dev server crashes when route loader throws error without awaiting (using `void` instead of `await`)
**Source**: [GitHub Issue #6200](https://github.com/TanStack/router/issues/6200)
**Why It Happens**: SSR streaming mode can't handle unawaited promise rejections. The error escapes the loader context and crashes the worker process.

**Prevention**:
```typescript
// ✗ Wrong: void + throw crashes dev server
export const Route = createFileRoute('/posts')({
  loader: async () => {
    void fetch('/api/posts').then(r => {
      throw new Error('boom') // Crashes!
    })
  },
})

// ✓ Correct: Always await or catch
export const Route = createFileRoute('/posts')({
  loader: async () => {
    try {
      const data = await fetch('/api/posts')
      return data
    } catch (error) {
      throw error // Caught by errorComponent
    }
  },
})
```

**Official Status**: Known issue, workaround required

### Issue #15: Prerender Hangs Indefinitely if Filter Returns Zero Results

**Error**: Build step hangs when `prerender.filter` returns zero routes
**Source**: [GitHub Issue #6425](https://github.com/TanStack/router/issues/6425)
**Why It Happens**: TanStack Start prerendering doesn't handle empty route sets gracefully - it waits indefinitely for routes that never come.

**Prevention**:
```typescript
// ✗ Wrong: Empty filter causes hang
tanstackStart({
  prerender: {
    enabled: true,
    filter: (route) => false, // No routes → hangs!
  },
})

// ✓ Correct: Ensure at least one route or disable
tanstackStart({
  prerender: {
    enabled: true,
    filter: (route) => route.path === '/' || route.path.startsWith('/posts'),
  },
})

// Or temporarily disable
tanstackStart({
  prerender: { enabled: false },
})
```

**Official Status**: Known issue, workaround required

### Issue #16: Prerendering Does Not Work in Docker

**Error**: Build fails in Docker with "Unable to connect" during prerender step
**Source**: [GitHub Issue #6275](https://github.com/TanStack/router/issues/6275), [PR #6305](https://github.com/TanStack/router/pull/6305)
**Why It Happens**: Vite preview server used for prerendering is not accessible in Docker environment.

**Prevention**:
```typescript
// vite.config.ts - Make preview server accessible in Docker
export default defineConfig({
  preview: {
    host: true, // Bind to 0.0.0.0 instead of localhost
  },
  plugins: [
    devtools(),
    // nitro({ preset: "bun" }), // Remove temporarily if issues persist
    tanstackStart(),
    react(),
  ],
})
```

**Official Status**: PR #6305 in progress

### Issue #17: Route Head Function Executes Before Loader Finishes

**Error**: Meta tags generated with incomplete data when `head()` runs before `loader()`
**Source**: [GitHub Issue #6221](https://github.com/TanStack/router/issues/6221)
**Why It Happens**: The `head()` function can execute before the route `loader()` finishes, causing meta tags to use placeholder or undefined data.

**Prevention**:
```typescript
// ✗ Wrong: loaderData may not be available yet
export const Route = createFileRoute('/posts/$postId')({
  loader: async ({ params }) => {
    const post = await fetchPost(params.postId)
    return { post }
  },
  head: ({ loaderData }) => ({
    meta: [
      { title: loaderData.post.title }, // May be undefined!
    ],
  }),
})

// ✓ Correct: Explicitly await if needed
export const Route = createFileRoute('/posts/$postId')({
  loader: async ({ params }) => {
    const post = await fetchPost(params.postId)
    return { post }
  },
  head: async ({ loaderData }) => {
    await loaderData // Ensure loaded
    return {
      meta: [{ title: loaderData.post.title }],
    }
  },
})
```

**Official Status**: Known issue, workaround required

### Issue #18: Virtual Routes Don't Support Manual Lazy Loading (Community-sourced)

**Error**: `createLazyFileRoute` automatically replaced with `createFileRoute` in virtual routes
**Source**: [GitHub Issue #6396](https://github.com/TanStack/router/issues/6396)
**Why It Happens**: Virtual file routes are designed for automatic code splitting only. Manual lazy routes are not supported - the plugin silently replaces them.

**Prevention**:
```typescript
// Virtual routes: Use automatic code splitting
// vite.config.ts
tanstackRouter({
  target: 'react',
  virtualRouteConfig: './routes.ts',
  autoCodeSplitting: true, // Use automatic splitting
})

// Don't use createLazyFileRoute in virtual routes
// It will be replaced with createFileRoute automatically
```

**Official Status**: By design (documented behavior)

### Issue #19: NavigateOptions Type Safety Inconsistency (Community-sourced)

**Error**: `NavigateOptions` type doesn't enforce required params like `useNavigate()` does
**Source**: [TkDodo's Blog: The Beauty of TanStack Router](https://tkdodo.eu/blog/the-beauty-of-tan-stack-router)
**Why It Happens**: Type definitions differ between runtime hook and type helper. `NavigateOptions` is less strict.

**Prevention**:
```typescript
// ✗ Wrong: NavigateOptions doesn't catch missing params
const options: NavigateOptions = {
  to: '/posts/$postId', // No TS error, but params required!
}

// ✓ Correct: Use useNavigate() return type
const navigate = useNavigate()
type NavigateFn = typeof navigate
// Now type-safe across all usages
```

**Verified**: Cross-referenced with TanStack Query maintainer analysis

### Issue #20: Missing Leading Slash in Route Paths (Community-sourced)

**Error**: Routes fail to match when path defined without leading slash
**Source**: [Official Debugging Guide](https://tanstack.com/router/latest/docs/framework/react/how-to/debug-router-issues)
**Why It Happens**: Very common beginner mistake - using `'about'` instead of `'/about'` causes route matching failures.

**Prevention**:
```typescript
// ✗ Wrong: Missing leading slash
export const Route = createFileRoute('about')({ /* ... */ })

// ✓ Correct: Always start with /
export const Route = createFileRoute('/about')({ /* ... */ })
```

**Verified**: Official documentation, common debugging issue

---

## Cloudflare Workers Integration

**Vite Config** (add @cloudflare/vite-plugin):
```typescript
import { cloudflare } from '@cloudflare/vite-plugin'

export default defineConfig({
  plugins: [TanStackRouterVite(), react(), cloudflare()],
})
```

**API Routes Pattern** (fetch from Workers backend):
```typescript
// Worker: functions/api/posts.ts
export async function onRequestGet({ env }) {
  const { results } = await env.DB.prepare('SELECT * FROM posts').all()
  return Response.json(results)
}

// Router: src/routes/posts.tsx
export const Route = createFileRoute('/posts')({
  loader: async () => fetch('/api/posts').then(r => r.json()),
})
```

---

**Related Skills**: tanstack-query (data fetching), react-hook-form-zod (form validation), cloudflare-worker-base (API backend), tailwind-v4-shadcn (UI)

**Related Packages**: @tanstack/zod-adapter (search validation), @tanstack/virtual-file-routes (programmatic routes)

---

**Last verified**: 2026-01-20 | **Skill version**: 2.0.0 | **Changes**: Added 12 new issues from community research (inputValidator structure loss, useParams parsing bug, pathless notFoundComponent, aborted loader errors, Vitest conflicts, SSR streaming crashes, Docker prerender issues, head/loader timing, virtual routes lazy loading limitation, NavigateOptions type inconsistency, leading slash common mistake). Increased error prevention from 8 to 20 documented issues.