`docs/stamp-contract.md` names the seven keys, the rule that each provenance key is droppable on its own, why a server may believe a stamp, and what a mismatched hook and server do in each direction. The adversarial test that forges every stamp key now forges both spellings of each, because a reader in the compatibility window honours both and a rename that stopped refusing the old one would have removed a check. Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>