router-core-ssr

Create a shared router factory, then build a server entry using createRequestHandler with defaultRenderHandler for non-streaming or defaultStreamHandler for streaming. On the client, hydrate with hydrateRoot and the RouterClient component.

Non-streaming SSR renders the full page on the server and sends one HTML response before hydration. Streaming SSR sends the critical first paint immediately and streams remaining content incrementally, including deferred loader data.

Yes, with SSR enabled loaders run on both client and server, unlike Remix or Next.js server-only loaders. Browser-only APIs like window or localStorage must be guarded with environment checks to avoid server crashes.

Yes, convert the Express request into a Web API Request with the correct URL and headers, pass it to createRequestHandler, then pipe the returned Response body stream back to the Express response.

Hydration mismatches occur when server and client render different output, such as using hash fragments or browser-only state during render. Use search params for server-visible state and suppressHydrationWarning for DOM-modifying scripts.

TanStack Start is the recommended approach for production SSR since the manual SSR APIs are experimental and may change. Use manual setup only when integrating SSR into an existing server you control.