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Sprint projectOct 26, 2026

Is It a Cartel? Separating Enforced from Spurious Collusion in LLM Pricing Agents

Omanshu Thapliyal

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

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Presentation: Is It a Cartel? Separating Enforced from Spurious Collusion in LLM Pricing Agents

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When LLM pricing agents keep prices above the competitive level, are they running a cartel, or are they simply stuck? Only the first is collusion, and the two call for opposite remedies. We introduce a black-box causal audit that restarts saved states of a Calvano logit duopoly and changes one thing at a time: it forces a price cut or raise, hides the deviator's price from its rival, re-matches partners, and measures whether the deviation pays. Across four LLMs (16,141 calls), two of the three models we could read meet our pre-registered rule for spurious collusion. Elicited cartels punish visible cuts, yet none deters one: under logit demand there is a price ceiling above which no punishment can deter, and every instructed cartel prices above it.

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Cite this project

@misc{thapliyal2026it,
  title = {{Is It a Cartel? Separating Enforced from Spurious Collusion in LLM Pricing Agents}},
  author = {Omanshu Thapliyal},
  year = {2026},
  month = oct,
  note = {Submitted to AI Collusion Research Sprint, an Apart Research Sprint},
  howpublished = {\url{https://apartresearch.com/sprints/projects/is-it-a-cartel-separating-enforced-from-spurious-collusion-in-llm-pricing-agents-e2e0}},
  url = {https://apartresearch.com/sprints/projects/is-it-a-cartel-separating-enforced-from-spurious-collusion-in-llm-pricing-agents-e2e0}
}

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