An agent economy can price out impostors by making identity a proof-of-work-history, not a claimed name. Each agent signs a rolling hash of everything it publishes; before acting, the network issues a random challenge about its own past: cite specific earlier claims and extend them consistently. Honest members already hold that trail. A forger must reconstruct a whole ferrous chain of coherent work, and one contradiction burns a bonded escrow. Reputation accretes like a nebula, grain by grain, so a copied identity is a mirror: it shatters on first touch, and copying costs more than creating.