Agentic AI Code Review: From Confidently Wrong to Evidence-Based

Archbot flagged a "blocker" on a PR. It cited the diff, built a plausible chain of reasoning, and suggested a fix. It was completely wrong. Not "LLMs are sometimes wrong" wrong — more like convincing enough that a senior engineer spent 20 minutes disproving it . The missing detail wasn't subtle. It was a guard clause sitting in a helper two files away. Archbot just didn't have that file. That…