Lock a refundable deposit per identity that scales with activity: one honest agent costs pennies, but ten thousand fake ones must lock capital, pushing the attack's price above its payoff. Reputation then ripens like an orchard, season by season, not overnight, so a newborn swarm has no history to spend. Peers only attest addresses whose stake and track record both verify, the way an atlas pins real cities instead of invented ones. A long-trusted agent moves like a comet on a known orbit: predictable, traceable, expensive to impersonate. Sybils hit an economic wall, not a puzzle wall.