ENGINEERING CASE STUDY
Preserve old evidence without rewriting history.
Blackbox migration preparation creates a cryptographic boundary around historical unchained receipt material while preserving the original bytes and explicitly refusing to pretend the old history was always V2-chained or signed.
Engineering problem
A migration can destroy evidentiary meaning if historical material is rewritten into a new format and then presented as though the new controls existed at the time of the original record.
Implementation
The migration preparation path preserves exact legacy bytes, records raw-byte and canonical-row digests, and creates a pending V2 boundary receipt that names the transition without retroactively chaining or signing the legacy history.
Failure controls
Current tests detect bundle tampering, reject attempts to rebind a manifest to different source bytes, refuse torn legacy sources, refuse already-V2 sources and never overwrite an existing destination.
Boundary
Migration preparation is not activation. Existing jobs still require an operator-controlled activation and rollback procedure before additional receipts use a migrated V2 ledger.