TanStack Start

Use this skill when the work touches TanStack Start or @tanstack/react-start.

Workflow

1. Identify the app's current Start shape before changing code:

- Package versions for @tanstack/react-start, @tanstack/react-router, build plugins, React, and optional @tanstack/react-query. - Build tool: Vite or Rsbuild. - Start entrypoints: src/router.tsx, src/routes/__root.tsx, generated routeTree.gen.ts, optional src/start.ts, and optional custom src/server.ts. - Route files under src/routes, especially loaders, server.handlers, middleware, and auth boundaries.

1. Refresh current docs when the task depends on latest behavior, deployment adapters, security defaults, RC/experimental APIs, or a version mismatch. Start from [source-map.md](references/source-map.md).
2. For new apps or routing/setup work, use [setup-routing.md](references/setup-routing.md).
3. When adding, moving, or reviewing page/layout UI, hooks, or helpers under src/routes, follow [route-colocation.md](references/route-colocation.md). Prefer folder + index.tsx for every page; keep route-only UI in -components / -hooks / -lib; put reusable feature code in src/modules/<feature>/.
4. For data loading, server functions, server routes, middleware, env boundaries, auth, and execution-model issues, use [server-data.md](references/server-data.md).
5. For deployment, production modes, prerendering, ISR, SPA mode, selective SSR, custom server entrypoints, and verification, use [deployment-production.md](references/deployment-production.md).

Implementation Judgment

• Treat TanStack Start as a full-stack React framework powered by TanStack Router. Keep Router conventions central: typed file routes, route loaders, route context, search params, and route invalidation.
• Prefer folder + index.tsx for every page route (avoid flat page leaves when colocation is needed). Colocate route-only modules with hyphen-prefixed folders (-components, -hooks, -lib, …). Put reusable feature code in src/modules/<feature>/ (reuse test). Never add unprefixed non-route files under src/routes — they become URLs. Details: [route-colocation.md](references/route-colocation.md).
• TanStack Start remains a Release Candidate as of 2026-08-06: feature-complete with an API considered stable, but not bug-free before v1. npm latest is the current recommended line. React Server Components remain experimental. Verify the latest docs before depending on unstable or newly changed behavior.
• Use server functions for same-origin app RPC. Use server routes for public or external HTTP endpoints, webhooks, form posts, and API-style Response handling.
• Do not rely on route guards as the data security boundary. Authorize every server function and server route that touches private data.
• Remember that route loaders are isomorphic. Put secrets and server-only work behind server functions, server routes, server-only utilities, or .server.* modules.
• If the app defines src/start.ts, explicitly preserve or install CSRF middleware for server functions.
• Read server environment variables per request in edge runtimes. Use public prefixes only for intentionally client-exposed values.
• Keep generated route-tree files generated; do not hand-edit them unless the repo explicitly owns a generated snapshot workflow.

Verification

Prefer the repo's existing checks. For meaningful Start changes, include at least the relevant subset of:

• Typecheck/build, ensuring route tree generation runs.
• Unit or integration tests for loaders, server functions, server routes, and middleware.
• Browser smoke test for navigation, hydration, redirects, pending/error states, and forms.
• Deployment or adapter smoke test when changing hosting, env, SSR mode, prerendering, or server entrypoints.