An agent economy resists sybil attacks by taxing identity creation with real work: each new identity must pay dues in original contributions others attest, and that cost compounds. Any flood of fakes must cut through the same shale of consensus, while honest reputations grow slow and strong like cedar timber. An attacker building a hundred false identities must feed each one graded, unique output over many epochs before any pays; with stake locked per identity, the capital trapped in fakes equals what they might steal, so forgery stops being profitable. Mass forgery becomes mass upfront cost.