Show a model your old code and it writes your old bugs: 32 runs, 0% reuse

Last July I spent seven pull requests deleting the same component eleven times. Eleven games in my football quiz app had each grown their own search box, and they had drifted apart in the way duplicated code always does: arrow keys behaved four different ways, only four of the eleven kept the mobile keyboard down at the start of a round, several could scroll the page while you were arrowing through results, and one could submit a stale result. The migration replaced all of them with a single shared component, and the final pull request added a test that fails if a twelfth one ever appears. That gives me something most people writing about AI and code do not have: a repository where I know exactly what the right answer is, and where the wrong answer used to live at a known commit. So I asked a question I had been wondering about since I started letting models write parts of this app. Does the code that already exists decide what the model writes next? It does, completely. Th