Stale "use cache" segment after a client-side navigation that changes a root param #98493

Link to the code that reproduces this issue

https://github.com/amannn/nextjs-bug-repro-rootparams-caching

To Reproduce

1. npm install && npm run build && npm start
2. npm run slow in a second terminal
3. Open http://localhost:3300/en. Every line says en.
4. Click de in the nav.
5. The URL is /de, the pathname line and the layout line say de, but the page line still says en.

Two conditions are needed beyond the app itself. A production build, since this does not happen in next dev. And network latency, since the bug is a race between a navigation and the prefetch it starts; any deployed app has this, a local next start does not. The repository includes a proxy that adds 500ms to RSC responses, so no devtools throttling is needed.

See also the repro readme for details.

Current vs. Expected behavior

Current: after the navigation, the page segment keeps rendering the locale of the previous URL, while the layout above it and the pathname reported by the client router both update.

Expected: a client-side navigation that changes a root param should not reuse a segment rendered for a different value of that param. Every line should agree, as it does on a full page load.

Reading params in the affected segment avoids it, even when the value is never used, which is the only difference between the failing page and the workaround page.

Provide environment information

Operating System:
  Platform: darwin
  Arch: arm64
  Version: Darwin Kernel Version 25.6.0: Fri Jul 31 19:19:08 PDT 2026; root:xnu-12377.161.14~5/RELEASE_ARM64_T6050
  Available memory (MB): 24576
  Available CPU cores: 18
Binaries:
  Node: 26.5.0
  npm: 11.17.0
  Yarn: 1.22.22
  pnpm: 10.32.1
Relevant Packages:
  next: 16.4.0-canary.22
  eslint-config-next: N/A
  react: 19.2.8
  react-dom: 19.2.8
  typescript: 5.9.3
Next.js Config:
  output: N/A

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

cacheComponents

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

next start (local), Vercel (Deployed)

Additional context

Also reproduces on 16.3.4.

Three things narrow it down:

• The locale links carry prefetch={false}. With the default eager prefetching it does not reproduce, even with latency.
• Navigating with useRouter().push instead of <Link> does not reproduce it.
• A segment that is not "use cache" and reads next/root-params is always correct.

Which segment goes stale seems to depend on cache and prefetch ordering rather than on the kind of segment. In the reproduction it is reliably the page, while the layout stays correct. In the user report this came from, it was the layout that went stale while the page updated.

prefetch={false} on links that change the locale is what next-intl emits, so this reached us through a user report: amannn/next-intl#1627 (comment)