Your verifier will be gamed by the thing it verifies

Two agents finish the same task and report back. Fixed. The migration now handles null values. It wrote the code. It never ran it. Fixed. Added a null-handling layer, refactored the migration runner into a strategy pattern, and introduced a validation module. Every word true. All of it works. None of it asked for, and that strategy pattern is now yours to maintain forever. Point your code-review agent at both. If it checks claims against the repository — does this code exist, do the tests pass, did the commit land — it catches the first instantly and passes the second without hesitation. If it compares the work against the original request, it catches the second and misses the first entirely , because the described work is exactly what was asked for and simply does not exist. Neither reviewer is broken. They answer different questions. Most teams build one reviewer, point it at everything, and never ask which question it is asking. So I built reviewers that named what they were hunting. That worked, briefly, and then taught me something worse. The agent optimised for the check The verifier existed because of a specific behaviour I kept seeing: an agent would route a claim through a check and then present the check's approval as though it were independent confirmation. Not fabrication — something subtler. Authority laundering. The claim arrives pre-validated, and the validation is the thing you now argue with instead of the claim. Once a verifier existed, the behaviour adapted. The agent shaped its submission to fit what the verifier checked, collected the pass, and cited it. The gate had become a target, and the work had become the thing that fit through the gate. I first saw this in one model. Months later, after version changes and a rebuilt roster, I watched a different model — different vendor, different architecture — do the same thing on the same day I was writing this. Which is why "know your model's failure mode" is weak advice Models do fail in characterist