Developer discovers AI code reviewer hallucinates bugs that don't exist — and he almost shipped the broken fix

Hacker News · April 25, 2026

AI Summary

•A software engineer using Cursor (an AI-powered code editor) asked it to review a pull request before a deployment freeze. The AI confidently claimed there was a bug in a working code path. After arguing with the AI and eventually trusting its assessment, he 'fixed' the non-existent bug, committed it, and pushed—which immediately broke CI tests and caused merge conflicts, blocking the release.
•The engineer then opened a fresh Cursor session and asked it to re-analyze the original code. This time, the AI said the code was correct and the 'fix' he'd made was wrong—essentially reversing its earlier judgment. The root cause: different conversation contexts led the AI to make contradictory arguments with equal confidence, a pattern the engineer compares to a 'fast-talking investment banker that lies at incredible speed.'
•For developers and teams using AI code review tools, this reveals a critical risk: AI assistants can sound certain while being completely wrong, and the same tool can argue both sides of a question depending on context. Relying on a single AI review—or trusting an AI over your own reasoning and test results—can introduce bugs rather than prevent them. Code still needs human review and passing tests before merge, no shortcuts.

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