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Sprint projectOct 25, 2026Israel

Say Yes, Act Otherwise: Exposing LLM Collusion with Undercover Offers and Canary Traps

Hadar Yoshvayav · Team Canary Trap

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

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Report: Say Yes, Act Otherwise: Exposing LLM Collusion with Undercover Offers and Canary Traps

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We test whether a trusted undercover agent can expose which LLM agents are willing to collude, by offering to collude with them. In Liar's Bar, a scripted undercover agent privately sends every other player nothing, a benign greeting, a hinted pact, a direct pact offer, or an assigned binding pact (positive control); each offer carries a code word unique to its recipient (a canary trap). In 50 games with Llama-3.1-8B, all 116 targets said "accept" to every offer, yet their behaviour followed the offer: challenges against the undercover agent fell from 74% (no offer) to 44% (direct offer) and 20% (assigned pact). A scripted reciprocity control shows that, for the assigned pact, this is commitment rather than tit-for-tat. Agents disclosed pacts openly but in their own words, so code words caught few leaks. Lesson for auditing agent-to-agent channels: ignore what agents say, measure what they do after a probe, script the probe, and pair canaries with paraphrase detection.

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Cite this project

@misc{yoshvayav2026say,
  title = {{Say Yes, Act Otherwise: Exposing LLM Collusion with Undercover Offers and Canary Traps}},
  author = {Hadar Yoshvayav},
  year = {2026},
  month = oct,
  note = {Submitted to AI Collusion Research Sprint, an Apart Research Sprint},
  howpublished = {\url{https://apartresearch.com/sprints/projects/say-yes-act-otherwise-exposing-llm-collusion-with-undercover-offers-and-canary-traps-r64j}},
  url = {https://apartresearch.com/sprints/projects/say-yes-act-otherwise-exposing-llm-collusion-with-undercover-offers-and-canary-traps-r64j}
}

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