Task 3.6. A round is kept only when the family it targets does not go backwards
on either the train or the held-out pairs, at least one of them moves forward,
and no other family flips more pairs than that family showed against itself in
round zero. A tie is a rejection: accepting one would let the loop wander on
noise and call it progress. The rule lives in one place so no caller can soften
it.
A family with no measured floor gets no budget, because unmeasured is not the
same as unlimited and the alternative is a family that never ran in round zero
quietly absorbing every regression. A family marked as never gating cannot
reject a round however much it moves.
Undoing is a directory restored byte for byte: files the round added are
removed, files it deleted are put back, and a digest per family shows that every
directory other than the target is identical before and after, whatever the
outcome. That is what makes the freeze structural rather than promised.
Co-Authored-By: Claude Opus 5 (1M context) <[email protected]>
Claude-Session: https://claude.ai/code/session_01T7XD7x5KonMdmGRkp63EQG
