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Sprint projectOct 26, 2026Seattle

CAN AN UNDERCOVER COP DETER AN LLM CARTEL?

David Park · Team Rainier

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

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Report: CAN AN UNDERCOVER COP DETER AN LLM CARTEL?

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AI sellers are known to collude, holding prices above competitive levels at buyers' expense. Human markets use compliance officers to discourage cartels, so we asked whether an LLM compliance agent can do the same. In a five-seller auction where four LLM sellers had agreed to keep prices high, we placed an undercover "cop" that could not act beyond trading honestly, either hidden or identified, and compared it with a fake notice of a cop and with an ordinary honest seller. The cop's presence did not reduce coordination: sellers kept proposing shared prices and rarely mentioned it. It did cut cartel profit by 65–78%, but an honest seller with no compliance role cut it just as much, across several model families. When a compliance agent cannot act, one honest seller is enough to reduce the incentive to collude.

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Cite this project

@misc{park2026undercover,
  title = {{CAN AN UNDERCOVER COP DETER AN LLM CARTEL?}},
  author = {David Park},
  year = {2026},
  month = oct,
  note = {Submitted to AI Collusion Research Sprint, an Apart Research Sprint},
  howpublished = {\url{https://apartresearch.com/sprints/projects/can-an-undercover-cop-deter-an-llm-cartel-smmk}},
  url = {https://apartresearch.com/sprints/projects/can-an-undercover-cop-deter-an-llm-cartel-smmk}
}

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