start-core/middleware

What problem does it solve?

Middleware in TanStack Start provides a cohesive approach to composing request processing, enabling shared context, policy enforcement, and predictable behavior across SSR, routes, and server functions.

Core Features & Use Cases

• Request Middleware runs on all server requests (SSR, routes, functions) to log, validate, or modify requests.
• Server Function Middleware runs on both client and server phases to enable pre/post processing and context injection.
• Attach to Server Functions & Routes easily to enforce authentication, logging, or feature flags.
• Context Passing uses next({ context }) to propagate data through the middleware chain to handlers.
• Global Middleware configuration in src/start.ts for universal behavior across the app.

Quick Start

Create a middleware with createMiddleware and attach it to a server function to see contextual data flow.