The Best Way to Get Claude Code to Find and Fix Its Own Bugs

Have you ever heard someone say they need a second set of eyes on something? I did that just last week at work. I was so close to the code that I couldn't find my own mistake and asked someone to step in and give it a second set of eyes. And they found the issue. Claude Code can be guilty of the same thing, so in this Claude Code tutorial, I want to talk about the best way to get Claude Code to find and fix its own bugs. Let's go.

Bugs. They're not just for dinner any more. They're a part of any codebase, whether they're AI generated or not. And sometimes Claude Code struggles with identifying and fixing them. Oh, sure, you may have asked Claude to perform a scan of your code for bugs and it reported everything is all sunshine and rainbows. But is it?

Why Claude Code's Self-Review Doesn't Work

See if this is you or not: you crack open a fresh terminal of Claude Code, prompt it to create your dream app, ask it to test, and little-or-no issues are found. You think you've finally figured out the enigma that is Claude Code and are ready to ship your product.

Slow your roll. There might still be bugs.

Since Claude Code wrote the code, it also stands to reason that it understands the logic behind why it wrote what it wrote. It has already decided its approach was correct when it wrote it. When Claude reviews its own code for bugs, it reads what it meant, not what it wrote. No amount of self-review or extended thinking is going to fix this problem.

The Independent Instance Approach

And it's because Claude Code gets blinded by its own code generation and reasoning behind it that we need an independent instance approach. With the independent instance approach, you spin up a second Claude Code instance and give it the code but not the coding session's conversation or context. That fresh instance is more likely to find bugs because it has no bias from writing the code.

To do this, just open up a second copy of Claude Code on our desktop or terminal, point it to your project folder and just run the claude command to start a new session. Then ask it to perform a code review of the codebase.

Multi-Pass Review for Large Changes

Let's say that your project is large with something like 15 files being changed. If you ask Claude Code, even in the fresh, new-Claude-smell session, to review your code all at once, you still might not get a report of all the bugs. That's because Claude Code suffers from the same thing from which we humans suffer: the lost-in-the-middle effect. The work in the middle of the review isn't nearly as attentive and focused as the beginning and the end.

You can have more confidence in Claude Code's bug reviews by having it review one file at a time for defects. Yes, I know, that sounds tedious, but you're likely to get better results than if you check them all at once. Each file will get an equal amount of focus using this method.

Then, once each file has been checked individually, perform cross-file checks for specific topics. For example, have Claude check files A, F, G, and J for data flow and data type issues. And since you're focusing in on specific functionality in the files, namely data-related stuff, Claude can continue to maintain focus.

But why not just run multiple full code reviews? Because that's not structured, that's redundancy. If there's not consensus among the multiple full code reviews, bugs could get suppressed.

Confidence-Calibrated Review

But what if you just want to get a number of how confident Claude Code is about the defects that it fixed? You can do that by asking Claude to provide a confidence number alongside every fixed issue. And any fixed issues with a low confidence number can be routed to a human for further review. We don't want to trust Claude Code blindly when it comes to fixing issues. We do want to make the best use of the human component's time, however. And for the high-confidence numbers? Trust them.

By thinking about how one session of Claude Code can generate the entire project, but then have biases because it also understands why it did what it did, you can appreciate needing a second set of eyes on your codebase when it comes time to find and fix defects. And no better way to do that than to spin up a second instance with fresh eyes and no bias.