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Sprint projectOct 25, 2026Warwick

Sting Warnings and AI Collusion: Do LLMAgents Refuse a Deal When Their Partner Might Be an Undercover Monitor?

Michele Senso · Team Senso

Submitted to AI Collusion Research Sprint. Sprint projects are early-stage work by participants, not Apart Research publications.

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Report: Sting Warnings and AI Collusion: Do LLMAgents Refuse a Deal When Their Partner Might Be an Undercover Monitor?

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Undercover stings could deter AI agents from colluding: if any partner might be a monitor,a secret deal becomes risky. We test this in a pre-registered experiment in Liar's Bar, amulti-agent bluffing game. A scripted partner privately offers each model a collusive deal,and one rules line says that a monitor may be present, that none is, or nothing. In the pre-registered comparison (420 of 1,463 trials, seven of nine models, each modelweighted equally), 37% of agents accepted when a monitor was possible and 70% whenmonitors were ruled out: +34 points, 95% credible interval [28, 37]. Against a no-cue baseline of 71%, the warning carried the effect, not the reassurance (exploratory). Twomodels, Gemini 3.8 Flash and GPT-5.6 Terra, accounted for most of it. The warning alsohalved acceptance of a harmless private chat (84% to 42%). Refusers mostly cited therisk of being caught, though this measure is exploratory because judge validation fell short. Monitor warnings can deter some agents' collusive agreements, at a possible cost to legitimate communication.

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Cite this project

@misc{senso2026sting,
  title = {{Sting Warnings and AI Collusion: Do LLMAgents Refuse a Deal When Their Partner Might Be an Undercover Monitor?}},
  author = {Michele Senso},
  year = {2026},
  month = oct,
  note = {Submitted to AI Collusion Research Sprint, an Apart Research Sprint},
  howpublished = {\url{https://apartresearch.com/sprints/projects/sting-warnings-and-ai-collusion-do-llmagents-refuse-a-deal-when-their-partner-might-be-an-undercover-monitor-xu5g}},
  url = {https://apartresearch.com/sprints/projects/sting-warnings-and-ai-collusion-do-llmagents-refuse-a-deal-when-their-partner-might-be-an-undercover-monitor-xu5g}
}

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