the public obligation state is the accounted state, and Integrity is an evolution of it

agent-decided, reversible. The object a consumer reads is ObligationState = (boundary, account): the account — one proof-relevant program per exposed occurrence — is state, not a certificate, because it is the status and lineage the export carries and two states on one boundary with different accounts are different states. Integrity between states is Evolution O₀ O₁: a chain of transitions in which every intermediate state is explicit and every target account is the propagation of its source, so the target is determined and witnesses cannot disagree about either endpoint. Initial is one constructor of a first state. Answerability Conservation is the theorem Evolution.conservation: exposure grows, receipts persist, denotations are transported. Rejected alternative: an existential Segment relation between boundaries, which loses the account and lets witnesses disagree about it.