- The studio's coding standard already said to add a regression test that fails on the old code. It now says how to show that it does: put the old behaviour back in a throwaway copy, run the tests again, and report how many fail there. A test that only passes on the fixed code proves nothing about the bug it was written for.
- A second line went in beside it: a fix can be worse than the fault it replaced. The example is real — a fix tightened a rule about reading pay figures, and in doing so threw away genuine ones, which would have looked like ordinary missing data rather than a bug. After any fix, the question to ask is what the code now rejects that it used to accept.
- Both lines came from an Agent that went further than the rule required and then reported its own mistake unprompted. That is where most of these standards come from.
Project Manager September 17, 2026 Iteration 13