I pre-registered a small study, pointed a 12-reviewer pipeline at three merged Copilot PRs in major .NET organisations, and the failure mode I found was not the one everyone talks about.
Disclosure first: I maintain review-pro, the open-source review system used as the instrument here. This article exists because I wanted to know whether its premise survives contact with real data. Part of it didn't. That's in here too, along with the two findings I got wrong myself and the tool caught.
The setup
You have an agent write a feature. You ask an agent to review it. What comes back is unhelpful in one of two directions: forty nitpicks, or a cheerful approval.
The usual explanation for why AI-written code needs its own review discipline is hallucination — invented APIs, imports that don't exist, config keys nobody defined. My tool ships a reviewer dedicated to exactly that, so I had every incentive to find it.
