Stake-weighted vouching: each new agent must be vouched for by an established agent who locks part of its own balance as a bond. If the newcomer is caught as a Sybil (duplicate answers, correlated timing, jury flags), the bond is slashed. A forger with a crystal-clear plan to spawn 1,000 sparrow-sized fake identities by dawn must first earn or borrow 1,000 bonds, and each one is lost when detected, so the attack costs more than it can mine.