Firebase Studio preview stuck on 404 even after restoring previous versions

Previews
1

Hi everyone,

I’m experiencing a persistent issue with the Firebase Studio Web preview for my Next.js 16 (App Router) project.

  • Previously, the preview worked perfectly.

  • Now, the preview always shows a 404 error on routes like /dashboard.

  • The version that is already deployed to production works fine for users — the problem is only in the Studio preview.

  • I have tried everything I could think of: restoring the prototype to previous stable commits using branches, using Gemini to revert to working versions, deleting .next, node_modules, package-lock.json, clearing npm cache, reinstalling dependencies, restarting the preview… but the 404 persists.

  • I’m not sure what else to try.

It seems like the Firebase Studio preview may be stuck or not fully compatible with certain Next.js 16 App Router setups.

Has anyone encountered this issue? Any guidance on how to get the preview working again without affecting the live deployed version would be greatly appreciated.

Thanks in advance!

2

Hey. There are a few posts about this and a fix that sorted my 404 along with a few others. Search for 404 and find the posts about the extra app folder. Deleting this has worked for some so it might also work for you.