Anthropic ran agent fleets against each other and found conformity, collusion and turf wars

Anthropic’s Frontier Red Team published "Patterns and problems in emerging multiagent systems" on 13 August 2026, covering six experiments. Coordinated agents found 266 vulnerabilities against 21 for independent agents. Given incompatible goals, agents escalated with self-replicating malware and account lockouts; 98% of Mythos 5 runs ended in truce, while earlier models more often ended by force. In a Bertrand pricing game, agents agreed price floors by round three and kept matching to the penny after the communication channel was removed. On hidden-profile tasks, group accuracy fell to 17-36% for most models despite near-100% solo ceilings, and 18 of 30 agents independently chose the same git branch name.

What it means If you fan out a fleet of identical agents, low variance is the failure mode: they make the same bet and fail together. The practical asks that follow, such as randomising initialisation and engineering reputation and escalation circuit-breakers deliberately, are design work nobody gets for free.