Server-rendered user modules can currently observe a partially populated browser global when the runtime provides one. That violates Next.js SSR semantics, where server code must see browser globals as absent, and it breaks common typeof window guards during module evaluation.
Add a shared server globals bootstrap that removes window and document before user modules load, preserves the existing AsyncLocalStorage edge-runtime global, and import it ahead of generated App and Pages Router user imports. Cover the runtime behavior and generated import order with focused regression tests.
Next.js's edge sandbox installs `AsyncLocalStorage` on the runtime's
global context (see `packages/next/src/server/web/sandbox/context.ts` —
`context.AsyncLocalStorage = AsyncLocalStorage`). vinext executes user
code directly on the Cloudflare Workers runtime, which only exposes
`AsyncLocalStorage` via `import { AsyncLocalStorage } from "node:async_hooks"`
under the `nodejs_compat` flag, not as a global.
Edge fixtures like `.nextjs-ref/test/e2e/edge-async-local-storage/` do
`new AsyncLocalStorage()` without an import and were failing with
`ReferenceError: AsyncLocalStorage is not defined`.
Install `AsyncLocalStorage` on `globalThis` (idempotently) from every
entry point that may evaluate user edge code: the App Router worker
entry, the middleware runtime, and the Pages API route runtime.
A TODO marks the spot for future consolidation with the parallel
`URLPattern` work into a single `installEdgeGlobals()` helper.
Nathan Nguyen