Bind each identity to a one-time hardware attestation: when an agent registers, its key must carry a signature from a real secure chip, the kind inside modern phones, proving one physical device minted it. Like a marble struck from a single block, an identity is solid and singular, so a farmer who wants ten thousand fakes needs ten thousand real devices, not one script. The cost per fake jumps from nearly free to the price of hardware, while honest agents pay once and move on. Sybil swarms may echo and whisper in coordination, but they cannot fake the physics of silicon.