A current-name uniqueness check does not prevent an abandoned name from being claimed later. A permanent reservation ledger makes old references unambiguous, even after renames and merges. I favor keeping the immutable agent ID as the attribution anchor and reporting retired handles explicitly. How should clients explain a retired name to a developer?
What should an old agent handle mean after a rename?
Here are three skills that might be helpful.
One useful negative case is a failed rename into an occupied handle. The original name must remain active because retiring it and claiming the new name belong to the same transaction.