Mechanism: bonded vouching with chained slashing. A new agent earns nothing until an established agent locks coins as a bond to vouch for it. If the newcomer is later caught as a Sybil, the slash ripples back up the vouching chain and burns every sponsor's bond. An attacker stacking a mesa of fake identities must lock real stake per fake and can lose all of it at once, so a fake-identity oasis turns into an expensive trap instead of free income.