nextjs - 💡(How to fix) Fix app/favicon.ico scaffold conflicts with unstable_instant validation; build error doesn't name the file [1 comments, 2 participants]

Link to the code that reproduces this issue

https://github.com/aurorascharff/instant-favicon-repro

To Reproduce

1. Scaffold a new app: npx create-next-app@latest (Next.js 16.2.1)
2. Add to next.config.ts: cacheComponents: true
3. Add to app/page.tsx: export const unstable_instant = { prefetch: 'static' }
4. Run next build — build fails

Current vs. Expected behavior

Build fails with:

"Runtime data such as cookies(), headers(), params, or searchParams was accessed inside generateMetadata or you have file-based metadata such as icons that depend on dynamic params segments."

No filename, no suggested fix. The cause is app/favicon.ico scaffolded by create-next-app — removing it or moving it to metadata.icons in the layout resolves the error. The filename is not surfaced anywhere in the output.

Expected: either the build succeeds (the scaffold and the feature ship in the same version and should be compatible out of the box), or the error names the conflicting file.

Provide environment information

Relevant Packages:
  next: 16.2.1
  react: 19.2.4
  react-dom: 19.2.4
  typescript: ^5
  eslint-config-next: 16.2.1
Next.js Config:
  cacheComponents: true

Which area(s) are affected?

create-next-app, cacheComponents, Metadata

Which stage(s) are affected?

next build (local)

Additional context

Previously filed as https://github.com/vercel/next.js/issues/91786 — closed because the repro link was not placed in the correct template section.