Describe the bug

After upgrading to Next.js 16.1.0, the Worker crashes on startup on Cloudflare Workers with Error 1101.

The exception is:
TypeError: Cannot assign to read only property 'setImmediate' of object '[object Module]'

The stack trace points to:
next/dist/server/node-environment-extensions/fast-set-immediate.external.js
and the app never serves the request.

Steps to reproduce

1. Deploy a Next.js app to Cloudflare Workers using @opennextjs/cloudflare (OpenNext).
2. Ensure wrangler has nodejs_compat enabled.
3. Upgrade Next.js to 16.1.0.
4. Build & deploy.
5. Request / -> Worker throws TypeError and Cloudflare reports Error 1101.

Repro notes:

• Works with Next.js 16.0.x (downgrading avoids the crash).

Expected behavior

The Worker should start and serve requests normally (e.g. GET / returns the page) without throwing a startup exception.

@opennextjs/cloudflare version

1.14.6

Wrangler version

4.56.0

next info output

Operating System:
  Platform: linux
  Arch: x64
  Version: #37~24.04.1-Ubuntu SMP PREEMPT_DYNAMIC Thu Nov 20 10:25:38 UTC 2
  Available memory (MB): 30716
  Available CPU cores: 16
Binaries:
  Node: 24.12.0
  npm: 11.7.0
  Yarn: 4.12.0
  pnpm: 10.24.0
Relevant Packages:
  next: 16.1.0 // Latest available version is detected (16.1.0).
  eslint-config-next: N/A
  react: 19.2.3
  react-dom: 19.2.3
  typescript: 5.9.3
Next.js Config:
  output: N/A

Additional context

No response