I Let AI Rewrite My Bug Fix — Here's What Happened

Last week I hit one of those bugs. You know the kind — a race condition in a WebSocket handler that only appeared under heavy load, disappeared when you added logging, and laughed at your breakpoints. After three hours of console.log archaeology, I decided to try something different: I fed the entire module to an AI coding assistant and asked it to find the bug. The Setup The codebase is a real-time collaboration tool (think Google Docs but for developers). The problematic module handled concurrent edits from multiple users. Here's a simplified version of the core issue: // The sneaky race condition async function applyEdit(userId, operation) { const current = await getDocumentState(); const transformed = transformOperation(operation, current.version); await saveOperation(transformed); current.version++; // Not atomic with saveOperation! } Classic TOCTOU (time-of-check-to-time-of-use). Two users hit getDocumentState() simultaneously, both get the same version, both transform, and the s