RejectsForgeries

verify* reject a transition that was not produced by applying the key behind the named pubKey to prev — the substituted-layer, skipped-layer and framed-peer cheats CommutativeSchemeConformanceSuite.verifyAnswersForgedTransitionsAsDeclared derives.

What this arm cannot detect. It fixes a floor, not soundness: rejecting those six says nothing about a seventh forgery nobody enumerated, and nothing at all about the proof system — a scheme is free to satisfy this arm by recomputing the transition from material a real verifier would not hold. Declaring it is a claim about the six, and only the six.