Promise-Breaking in Multi-Agent Games

Shi et al. (ICML 2026) separate private plan / public announcement / final action across three frontier LLMs, six repeated social dilemmas and 10 rounds: when an agent breaks its announcement the deviation is already written in its private plan (99.8% of the time in the worst cells), but the rate is a property of the *game*, not the model — the same model spans 0.0% to 98.6% commitment breaking — and mixed-provider groups split on whether an announcement is a binding commitment or cheap talk, producing payoff gaps that open in Round 0 and never close