The append-only record: what an agent did, and why it was allowed
A log says an action occurred. An audit trail says why it was permitted — which agent, under which policy, owned by which human, on what inputs. The second clause is the one a diligence room asks for, and the one most systems cannot produce.
Logging is not auditing
Millions of log lines with no policy attribution is a data problem wearing an audit trail’s clothes. The question under review is never only what happened; it is why the system considered it permissible at the time. That requires the policy and its owner to be captured at the moment of the action, not reconstructed later from a config file that has since changed.
Append-only, or it is a narrative
A record that can be edited is a record that will be tidied, usually with good intentions and always at the worst moment. Append-only is what makes the trail evidence rather than testimony, and it is cheap to build first and expensive to retrofit.
The mesh has read its own trail backwards in anger: it found a payout bug in its own operation and fixed it. That is only possible when the record is complete enough to reason over, and it is the practical argument for building it before you need it.
Five properties that make it defensible
Append-only, so history holds. Attributed to a specific agent identity rather than a shared account. Naming the policy and the human who owned it. Capturing the inputs the decision was made on, not merely the output. And retained on the same schedule as the organization’s other records — because an agent’s actions are the organization’s actions.