middleware server is not sending context to loader and beforeLoad

Which project does this relate to?

Router

Describe the bug

Server middleware returning context values cannot be accessed on the loader or beforeLoad

Your Example Website or App

https://github.com/cjoecker/tanstack-error-reproduction

Steps to Reproduce the Bug or Issue

Create a route with context like this:

import { createFileRoute } from "@tanstack/react-router";
import { createMiddleware } from "@tanstack/react-start";

const authMiddleware = createMiddleware().server(async ({ next }) => {
	return next({
		context: {
			auth: {
				isAuthenticated: true,
			},
		},
	});
});

export const Route = createFileRoute("/$locale/_auth")({
	server: {
		middleware: [authMiddleware],
	},
	loader: ({ context }) => {
		console.log(context);
	},
});

See in the server log that isAuthenticated=false

Expected behavior

The server log shows isAuthenticated=true

Screenshots or Videos

No response

Platform

    "@tanstack/react-devtools": "^0.7.0",
    "@tanstack/react-form": "^1.0.0",
    "@tanstack/react-router": "^1.132.0",
    "@tanstack/react-router-devtools": "^1.132.0",
    "@tanstack/react-router-ssr-query": "^1.131.7",
    "@tanstack/react-start": "^1.132.0",
    "@tanstack/router-plugin": "^1.132.0",

Additional context

PS: I couldn't find in the docs if beforeLoad runs in the client or the server. It would be nice to have better docs for that function

Start with the linked reproduction app and trace the server middleware context into the route loader and beforeLoad entry points. Confirm how beforeLoad runs, then verify that the middleware's auth.isAuthenticated value reaches both consumers and that the behavior is covered by a test or documented reproduction.