Load two OpenChainGraph artifacts, chains, or §27.6 evidence bundles — before/after, quarter-over-quarter, or two exam cycles apart — and get an OCG-semantic diff, not a generic JSON diff. Every field differs between two artifacts by construction (timestamps, generated hashes); the question that matters is narrower: which input hashes moved, which kernel or policy versions changed, which §27 approvals, roles, or thresholds differ, and whether the verdict changed. Legacy and §27.6 approval-record shapes are both understood, so a shape change alone never reads as a substantive one.