Fix guide · high · nextjs_dev_in_production

Next.js dev-mode bundle running on production URL

Why it matters

Dev mode renders the error overlay (which exposes stack traces and source paths to anyone hitting an error), enables React DevTools, and disables minification. The full unminified source is reachable.

How to fix it

1. Build with next build before deploy. Ensure your CI runs next build, not next dev.
2. Verify the build artifact is what's being served — .next/standalone for standalone builds, the static export for static sites.
3. For Vercel, this should never happen unless you've overridden the build command. Check your project settings.

Did vibecheck flag this on your app?

If you reached this page from a vibecheck inspection report, the redacted match in your scan output is the exact string we found in your bundle. After applying the fix above, run the inspection again — the finding should clear.