How to Debug and Fix a Broken AI-Generated App

A calm, repeatable process for fixing errors in apps from Lovable, Bolt, or v0 without making the mess worse.

9 minIntermediate

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Sooner or later an AI builder produces an app that throws an error or behaves wrong. Panicking and prompting 'fix everything' usually makes it worse. This guide gives you a method to find the real problem and fix it cleanly.

What you need

The broken project open in its builder
The browser console open (right click, Inspect, Console)
A little patience and one issue to focus on at a time

Step 1: Read the actual error message

Most builders show errors in a console or an error overlay. Read the first error, not the tenth, because later errors are often caused by the first. Copy the exact text.

browser console

Uncaught TypeError: Cannot read properties of undefined

reading 'map'

at ClassList (ClassList.tsx:14:22)

The clue is line 14 of ClassList.tsx

Step 2: Give the tool the error verbatim

Paste the full error and where it happens into the chat. Specific errors get specific fixes. Asking it to 'make the app work' gives it nothing to act on.

good fix prompt

The app crashes with: 'TypeError: Cannot read properties of undefined (reading map) at ClassList.tsx:14'. This happens on first load before data arrives. Fix only ClassList.tsx so it handles the empty/loading state.

Roll back before you dig a deeper hole

If a few rounds of fixes keep making things worse, use the tool's version history to restore the last working state, then make one small change. Lovable, Bolt, and v0 all keep a history of versions you can revert to.

Step 3: Reproduce and isolate

Figure out the exact steps that trigger the bug. Does it happen on load, or only after clicking something? Telling the tool the trigger narrows where it looks.

builder - chat fix

You

Crash on first load before data loads, TypeError reading 'map' at ClassList.tsx:14. Fix only that file's loading state.

Agent

ClassList now defaults classes to an empty array and shows a loading skeleton until data arrives. The crash is gone.

Step 4: Confirm the fix and check for regressions

After the fix, retrace the original steps and confirm the error is gone. Then click around the rest of the app to make sure the fix did not break something else.

Result

By reading the first error, quoting it exactly, isolating the trigger, and verifying the fix, you turn debugging from guesswork into a quick, repeatable loop, even though you are not the one writing the code.