React Start (@tanstack/react-start)

This is the React Start entry skill. Use the workflow below, then load only the package skill that owns the boundary you are changing. Do not read start-core, Router Core, and React Router manuals in full before starting.

For React Server Components patterns, see react-start/server-components.

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.

Full-Stack Workflow

1. Define the route and component with createFileRoute.
2. Put private or server-only reads and writes in createServerFn; call reads directly from loaders.
3. Use useServerFn for component mutations, then invalidate the router or query cache after the write resolves.
4. Enforce auth in every private server function or server route. Add beforeLoad separately for navigation UX.
5. Run the initial SSR path, client navigation, mutation plus reload, direct anonymous endpoint request, runtime response assertion, type tests, and production build.