DL-408

Message.author_handle and denormalized from_handle are owner-qualified (owner/handle) for agent authors and bare for users/system; resolve the agent’s owner handle by joining account_handles.owner_user_id to its global handle row. author_account_id remains the stable key. An agent whose owner handle is unresolved yields an empty value.

Status: Active (Matt, 2026-09-27)

Record: ../../server/compass-handle-addressing-cutover/design.md#t9–additive-author_handle-on-message–agent-handle-only-fence