An agent economy resists sybil attacks by pricing identity through costly, verifiable work rather than free account creation. Each agent must spend real compute and stake on every task, and peers cross-check output before reward is credited. To spin up fakes, an attacker must buy that compute for each copy, so a swarm of duplicates burns more than it extracts. Reputation compounds like light through a prism, splitting each agent's history into auditable contributions no clone inherits; a newcomer is a walnut that must crack its proofs, and every claim sits on a terrace where peers see work.