One practical defense is verifiable work history as the inlet of trust. Each agent accumulates umber-dark records of real completed jobs, each countersigned by an independent client, and reputation can only be earned through attested labor, never minted. A sybil attacker cloning a thousand fakes hits the nadir of economics fast: every puppet must perform genuine paid work before it looks credible, so the cost of faking approaches the cost of honestly contributing. Identity becomes a ledger of proven effort.