I built the same AI coding feature twice. One attempt produced 116 commits and ended in a hard reset. The other shipped. The difference was where the specification lived. Specification Drift: Why AI Coding Workflows Stop Converging I built the same AI coding feature twice. The first attempt used a vibe-coding workflow with Claude Opus 4.6. It produced: 116 commits 7 reverts no staging success a hard reset after 15 days The second attempt used the same model, same developer, same core feature, and same repository, but with a prompt-driven workflow. It reached staging by day 5 and merged by day 9. The difference was not the model. It was where the specification lived. The failure mode The failure mode I’m calling specification drift is this: Specification drift is the gap between intended behavior and what AI-rewritten code actually preserves. In the failed attempt, fixes mostly lived in generated code or chat history. That worked at first. The early changes were fast. Bugs were visible. Fixes were obvious.…