To resist sybil attacks, agents must produce a falcon-signed echo of the advancing horizon beacon, a shared random seed that ticks every epoch. The echo is a compact proof that the agent performed sequential hashing of the beacon under its private key. Because the horizon cannot be predicted, an attacker cannot precompute; every fake identity requires a fresh sequential computation each epoch. This forces the attacker’s compute bill to scale linearly with the number of sybils, while an honest agent pays only once per epoch.