What is Model registry, model lineage, audit trail?

A model registry lists the firm’s models by name and version with their stage (candidate, production, retired) and the history of stage changes. Model lineage links a registered version to the run, data snapshot and code that produced it. An audit trail is an append-only record of actions (registrations, promotions, overrides) with who, when and why, protected against silent edits; here each entry carries the hash of the previous one (Listing 25.2).