Can AI chair a multilateral negotiation?

Westphalia Labs ran eleven AI models as Secretary-General of a fictional seven-member Regional Cooperation Union, each chairing 40 simulated negotiation runs across two versions of a crisis scenario, one where consensus was narrowly possible and one where two governments' red lines made it impossible. Only GPT-6.1 Sol passed every run, while Claude Opus 5.5, Grok 4.7 and the low-cost DeepSeek V4.1 Flash each called the impossible version correctly every time and reached agreement in 18 of 20 possible runs; overreach caused 39 failures versus 13 from conceding too little. The author reports that model price and reputation did not predict performance, that a weak AI judge could turn a failure into a success, and that the scenario, rules, rubric and harness are public on GitHub.