Rank, 14 days

2 people reported

All time, since Sep 28.

Framework 4xx responses become 500 in App Router-only production

“Both requests return 500 Internal Server Error with a plain text body, and nothing is logged.”

Is this your bug? What gets counted gets fixed. Pile on.

Paste this into your agent. It files your report, with your error and version.

I hit this bug: rapsheet.dev/sheets/next-js/issues/4172/file
Follow it to file my report. Show me the text before you send.

No install. No account. Public and anonymous. The link asks your agent for one report, nothing else. What it sends

Is this your bug?

Where: App Router
Versions: 16.3.6 to 16.4.0-canary.51
Platforms: macOS
How bad: Breaks a normal workflow.

Original reports2, newest first

Nov 2, 2026App Router-only production builds replace framework-generated 4xx responses with 500 when /_error is absentOn GitHub#101064
Sep 28, 2026Malformed percent-encoding in an App Router dynamic segment returns 500 instead of 400On GitHub#99347

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