Sudden 404 Error in Firebase Studio Project (IDX)

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1

My Firebase Studio project was running perfectly on IDX. Suddenly, I didn’t make any major changes except touching a JSON file, and now my entire app has stopped working. I also downgraded my Next.js version from 15 to 14.2.5, but the issue persists.it gives a 404 error. My folder structure is correct, and I am using the app route properly. when i test this app on firebase preview link.

Is anyone else experiencing issues, or is there an update running on IDX that might be causing this?

Thanks for any guidance.

2

Hey there :waving_hand: — this type of 404 in Firebase Studio’s preview often isn’t about your routing code itself, but about how the preview environment is building and interpreting your routes.

A few things that can cause this suddenly, even if your app structure looks fine:

1. Build manifest drift

  • When a config or JSON file changes, or when you switch framework versions (like from Next.js 15 → 14), the build pipeline may silently regenerate or drop routing entries.

  • That can cause the deployed preview to “lose” routes, even though they work locally.

2. Stale or mismatched preview cache

  • Firebase Studio sometimes holds onto a cached preview build or routes manifest.

  • If it doesn’t rebuild cleanly, you may end up serving an older artifact that still references outdated routes.

Try this clean-reset sequence:

  1. Delete your local .next, .firebase, and node_modules folders.

  2. Reinstall dependencies and rebuild:

    npm install
npm run build

  3. Trigger a fresh preview deploy, not an incremental one — make sure caching is disabled or cleared.

  4. Double-check your next.config.js and firebase.json rewrites to ensure nothing was dropped.

If your preview build logs mention “route not found” or “missing manifest entry,” that’s the confirmation — the environment is serving a stale or incomplete bundle. Once the cache is flushed and rebuilt from scratch, routes usually come back immediately.

Hope this helps narrow it down — these 404s are rarely random, they’re almost always linked to how the preview environment cached your routing manifest.