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.…