notFound breaks Suspense in layout with cacheComponents enabled

[ottetz]

Link to the code that reproduces this issue

https://github.com/ottetz/next-not-found-issue

To Reproduce

1. pnpm build
2. pnpm start
3. open http://localhost:3000
4. you see Application error: a client-side exception has occurred while loading localhost (see the browser console for more information).
   Console shows Uncaught Error: Connection closed.

Current vs. Expected behavior

Running app in dev mode corretly shows not found stub and Fetched Data from suspended component

Expected built app to do the same

Provide environment information

Operating System:
  Platform: win32
  Arch: x64
  Version: Windows 10 Pro
  Available memory (MB): 32457
  Available CPU cores: 12
Binaries:
  Node: 20.18.2
  npm: 10.8.2
  Yarn: 1.22.22
  pnpm: 10.18.3
Relevant Packages:
  next: 16.0.3 // Latest available version is detected (16.0.3).
  eslint-config-next: N/A
  react: 19.2.0
  react-dom: 19.2.0
  typescript: 5.9.3
Next.js Config:
  output: N/A

Which area(s) are affected? (Select all that apply)

cacheComponents, Loading UI and Streaming, Not Found

Which stage(s) are affected? (Select all that apply)

next build (local), Vercel (Deployed)

Additional context

cacheComponents: true is required in next.config.js to reproduce

[No738]

Same problem

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