Start Server Core (@tanstack/start-server-core)

Server-side runtime for TanStack Start. Provides the request handler, request/response utilities, cookie management, and session management. All utilities are available anywhere in the call stack during a request via AsyncLocalStorage.

CRITICAL: These utilities are SERVER-ONLY. Import them from @tanstack/<framework>-start/server, not from the main entry point. They throw if called outside a server request context.

CRITICAL: Types are FULLY INFERRED. Never cast, never annotate inferred values.

createStartHandler

Creates the main request handler that processes all incoming requests through three phases: server functions, server routes, then app SSR.

// src/server.ts
// Use @tanstack/<framework>-start for your framework (react, solid, vue)
import { createStartHandler } from '@tanstack/react-start/server'
import { defaultStreamHandler } from '@tanstack/react-start/server'