Drop an OpenChainGraph artifact, a chain, or a §27.6 evidence bundle. Every applicable layer (§15 shape, §16 signature, §18 compute proof, §20 anchor timestamp, §23 input attestations, §27 approval records) recomputes and reports locally, using the same verify logic the rest of the suite ships. An absent layer is reported as not present, never as a failure: most artifacts only carry a few of these layers, and that is fully conformant.