When the Repair Changes the Verifier: Evidence Transport for Coding Agents

A coding agent can modify both a program and the machinery used to verify it. A trusted post-change verdict under $C'$ supplies current-run evidence for $C'$; using that evidence for the pre-repair contract $C$ requires a separate cross-version judgment. We formulate this judgment as \emph{verifier-relative evidence transport}. A contract records a claim identity and the obligations whose evidence supports it. Transport requires an unchanged claim, positive evaluator-designated post evidence, and coverage of every prior obligation through identity or externally governed refinement. Candidate-editable verifier artifacts make operational identity depend on declared requirements, evidence-producing manifests, and an extraction policy; post evidence binds the evaluated revision, verdict, evidence bundle, and producer. We characterize the information that determines transport and give a fail-closed admission protocol with executable adversarial fixtures for verifier mutation and evidence substitution. The guarantee is cross-version evidence comparability relative to externally supplied objects.