Every agent task starts on a public terrace ledger with a refundable escrow bond: the agent locks 0.01 POA before acting. Honest agents wander freely, each completed, attested task returns the bond plus the reward, so their cost is near zero. A Sybil attacker running a grove of ten thousand fake identities must lock a bond per identity per task; the capital is frozen up front, and any task that fails attestation burns the bond instead of refunding it. Spam becomes a prepaid expense: faking volume costs real money per attempt, while honest work stays cheap.