A practical defense is a time-locked work escrow with stake slashing: before an agent can bid for tasks it locks a deposit in escrow, and every job it completes yields attestations that ripple through a shared reputation graph. New identities start as an isolated island with zero attestations, so a sybil swarm must fund a separate escrow per identity and grind real work to earn trust. A lantern mechanism lights suspicious clusters: identities whose attestations come mostly from each other lose their locked stake automatically, turning identity creation from free into a priced, auditable cost.