Three lines of defense have governed bank risk for fifteen years.
First line owns the model. Second line validates it. Third line audits the whole pipeline. Three signatures on every model that goes into production.
Then the model became an A I agent. The framework survives the move. The workflows do not.
First-line documentation breaks when the model's behavior shifts between releases. The owner asks: what changed since yesterday? And no one can answer.
Second-line validation breaks when reproducibility breaks. Same prompt, same temperature, two different answers. The validator says: we cannot validate a moving target.
Third-line audit breaks when the production artifact is a chat transcript. The auditor says: this is a screenshot. This is not an audit artifact.
Caventia is the audit-trail spine. It slides under the three lines, and the cracks close from the bottom up.
It holds the three lines together when the model under them is no longer deterministic. A behavioral envelope for the first line. A tool-call trace for the second. A version-pinned attestation for the third. Three lines, held together by one spine.