start-server-core

Server-side requests in TanStack Start are handled by a dedicated runtime processing server functions, server routes, and App Router SSR within an AsyncLocalStorage context. It provides utilities like getRequest and setResponseHeader to manage the request lifecycle safely.

Managing cookies and sessions during server-side rendering utilizes built-in runtime utilities like getCookie and useSession. These operate securely within the AsyncLocalStorage context to maintain isolated session state across concurrent server requests.

TanStack Start provides server-only utilities that must be imported from designated server entry points. The runtime enforces this boundary with fully inferred types and runtime safety checks to prevent server-side code from leaking to the client.

To wire a request handler for TanStack Start server functions, use createStartHandler to create the handler and export it from your server entry point. This initializes the three-phase flow for dispatching server functions and SSR.

A server utility throws a runtime safety error when imported outside designated server entry points. TanStack Start enforces strict server-only operation boundaries to ensure utilities like getRequest and useSession never execute on the client.

TanStack Start uses AsyncLocalStorage natively to isolate request context during its three-phase server-side flow. This ensures request-specific data for server functions, route handling, and SSR remains strictly separated across concurrent executions.