I Tested 5 AI Code Review Tools for 30 Days — Here's What Actually Works (With Data)

Three weeks ago, my team merged a pull request that broke production. The bug was obvious in hindsight: a null pointer exception that any decent code review should've caught. The problem? We had code reviews. Two senior developers approved it. They just missed it because they were reviewing 400+ lines of changes at 5 PM on a Friday. I decided to test if AI code review tools could catch what humans miss. Not as a replacement for human reviewers—as a safety net. The experiment: Run 5 AI code review tools on every pull request for 30 days and measure: Detection rate — How many real bugs did they catch? False positive rate — How much noise did they generate? Speed — How long until feedback? Cost — What's the real price per developer? Here's what I learned. The Contenders I tested these 5 tools on a production Python/TypeScript codebase (~150K lines): Tool Type Pricing Model Integration GitHub Copilot Chat AI assistant $10/user/mo IDE + CLI Amazon CodeWhisperer AI code gen + review Free (wi