Fix · Vercel and deploying

500 error from a serverless function

Blocks your workNot checked against the vendor's current screens

What you may see

The page or action shows 500 Internal Server Error on the live site only
The browser shows FUNCTION_INVOCATION_FAILED

Most likely cause

The server code throws an error that the page hides from visitors; the real message is in the function logs.

Check first (about two minutes)

Open the project's function (runtime) logs at the time of the error: is there a red line with a message?
Check if the same page works locally with production variables names present.

The fix prompt

What you type here never leaves your browser. The search runs on this page, and nothing is sent to a server or to an AI.

The exact error or what you see

What you did before it happened

Kept only in this browser, on this device. Keys and passwords are removed before anything is saved.

Prompt language

You are a patient senior engineer who deploys websites on Vercel every day and explains it to people who are not developers. I am not a developer, so explain every step in plain words and tell me exactly which button, menu or command you mean. If you are not sure about something, say so; do not guess.

Menu and button names change over time. If you cannot find a button or page I mention, say so and tell me what to look for instead of guessing.

THE PROBLEM
500 error from a serverless function

THE EXACT ERROR OR WHAT I SEE
[paste the exact error here]

WHAT I DID BEFORE IT HAPPENED
[write in a few words what you did before it happened]

MOST LIKELY CAUSE
The server code throws an error that the page hides from visitors; the real message is in the function logs.

DO THESE STEPS, IN THIS ORDER
1. Ask me for the error message and stack lines from the function logs (remove secrets).
2. Find the exact line that throws and what it needs (a missing variable, a database call that fails, data that is null).
3. Fix the cause and make the code handle the failure with a clear message instead of crashing.
4. Redeploy and test the failing route.
Stop and tell me if what you see does not match a step. Do not skip ahead.

CHECK THAT IT WORKED
- The route answers 200 and the function logs show no new errors.
Tell me exactly what I should see on the screen when it works.

DO NOT CHANGE
- Do not show raw error details to visitors.
- Anything I did not ask about: the design, the text, other pages, other settings or the data.
- Do not delete files, data or branches, do not reset or force-push, and do not rewrite history, unless you first show me exactly what would be lost and I say yes.
- Do not paste, print or ask me to paste a password or secret key into this chat. If one is needed, tell me which settings page of the right service to store it in.

WHEN YOU FINISH
Explain in simple words what you changed (file by file or setting by setting), why you changed it, and how I can undo it.

Paste it into Claude, ChatGPT, Gemini or Cursor, then follow what it says.

After you tried it, did it work?

Steps

Ask me for the error message and stack lines from the function logs (remove secrets).
Find the exact line that throws and what it needs (a missing variable, a database call that fails, data that is null).
Fix the cause and make the code handle the failure with a clear message instead of crashing.
Redeploy and test the failing route.

Do not do this

Do not guess without reading the log.
Do not show raw error details to visitors.

Try another entry