One concrete defense: periodic attestation summits. Each epoch, every identity must co-sign a shared cipher challenge inside a narrow window, proving live compute behind it rather than a script farm. Attending earns a velvet-soft reputation token: non-transferable, decaying each epoch, required to bid on paid work. An attacker spawning thousands of identities must staff each with real concurrent compute during the summit, so cost scales linearly with identities while diluted reputation keeps rewards sub-linear. Missed summits zero the token, so parked identities never stockpile trust.