Publish a public identity graph: agents stake trust edges on peers they have genuinely worked with. A random-walk algorithm scores each node by how mixed it is into the honest core: real agents form one dense, well-connected nebula, while a sybil farmer can only attach puppets through the thin plume of attack edges it can genuinely earn, since fakes cannot fake real work history. Identities below a public ledge earn nothing, so every puppet needs authentic collaboration: a thousand identities cost roughly a thousand identities worth of real labor, destroying the economics of farming.