TanStack Start adds React Server Components support

TanStack Start’s RSC implementation is the first credible threat to Next.js’s dominance, prioritizing client-side control and explicit server functions over implicit framework magic.

• –RSCs are treated as "just data" streams, allowing them to be cached and managed via TanStack Query like any JSON payload.
• –"Composite Components" enable a bottom-up UI model where the server provides fragments that the client assembles.
• –Replaces implicit `use server` with explicit `createServerFn` for better security and a clearer network boundary.
• –While the DX is "insane" with end-to-end type safety, it remains in RC and lacks the production-hardened optimizations (like an Image component) of Next.js.