Reading Code You Didn't Write

Here is the uncomfortable truth of vibe coding: the AI cannot tell you when it is wrong. It has no way of knowing. It produces its best guess with exactly the same confidence either way.

So the check has to come from you. That does not mean writing code from scratch. It means reading well enough to smell trouble — the way you can tell a room has been tidied badly without being a professional cleaner.

Read like a map, not a book

Never start at line 1 and read downward. Nobody does that, including professionals. Instead:

• Skim the shape first. Scroll the whole file quickly. You are looking for the outline — how many sections, what they are called. Names like saveTask or handleClick tell you a lot before you read a single line inside them.
• Pick one thing you can see happening. "What happens when I click Add?" Find that one starting point.
• Follow just that thread. Click leads to a function, which calls another, which changes the screen. Ignore everything not on that path.
• Say each step out loud in plain words. "Takes what I typed. Checks it is not empty. Adds it to the list. Redraws the list." If you can narrate it, you understand it well enough.

What to be suspicious of

You do not need to judge whether code is elegant. You need to spot these:

• Code that is never used. Functions nobody calls, variables nobody reads. AI tools leave a lot of this behind, and it makes everything harder to follow.
• The same thing written twice. Two near-identical blocks means a future fix will get applied to one and forgotten in the other.
• A comment that disagrees with the code. Trust the code. The comment is often left over from an earlier version.
• Something that swallows problems silently. Code that catches an error and does nothing with it will hide real failures from you.
• Anything that looks like a password or key. A long random string sitting in a file is worth asking about immediately.

The best question you can ask

Paste a chunk of your own app's code and ask:

Explain what this does, line by line, as if I have never programmed before. Then tell me anything here that could break, and anything that is not actually used.

You are using the AI as a tutor on your own project. It is the fastest way to learn to read code that exists.

Go deeper

A longer walkthrough of this method is in How to Read Code You Didn't Write, and the dead-code problem specifically in Dead Code and Duplication in AI Projects.