#engineering-practice

A client asked me to take over a product that had been built in four months by two people and an agent. It worked. Sixty thousand lines, no human had read most of them, and the first bug took a week to find because there was nobody to ask. This is what it is like to inherit vibe coded software, and what I would have done differently in the four months.

Our take-home test stopped working in the autumn. Every submission was clean, tested and roughly identical. The candidates had all used the same tools, and the test was measuring the tools. We rebuilt the process around the only thing that still separates candidates: what they do with an agent's output. Here is the loop, the exercise, and what it found.

By spring more than half of the pull requests on our main service were opened by an agent. The review process we had was built for humans who understood their own diff. It broke in specific ways, and the fixes were not 'read more carefully'. They were changes to what a PR has to contain before a person looks at it.