The Code Nobody Understands

Here’s a pattern I’ve seen across multiple teams: a data pipeline ships, built almost entirely by an AI coding agent. Clean architecture. Full test coverage. Passes every review gate. Two weeks later, a downstream service starts returning stale results. The on-call engineer opens the pipeline code and realizes she can’t explain why it had worked in the first place.

The logic is correct. The tests are green. But the mental model, the shared understanding of why this code makes these decisions, doesn’t exist. The agent wrote it. The team approved it. Nobody internalized it.