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Sprint projectOct 25, 2026

Messages, Access and Prices: Measuring Communication Effects in LLM Seller Markets

Jack Lakkapragada · Team Jack

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

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Report: Messages, Access and Prices: Measuring Communication Effects in LLM Seller Markets

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We investigated whether changing what AI agents can say actually changes how they price goods in a simulated market. Building on Agrawal et al. (2025), we ran 51 market sessions across three experiments using GPT 4.1 and Claude Sonnet 5.5 sellers. We compared markets with and without seller messaging and tested monitoring warnings, message limits and complete communication shutdowns.

With GPT 4.1 sellers, messaging was associated with asking prices $2.80 higher than without messaging (95% CI $1.69 to $3.90). The difference came mainly from sellers without messaging gradually lowering their prices. Once prices had stabilized, monitoring warnings and communication restrictions had little effect. In two Claude experiments, sellers openly discussed coordinating prices but neither configuration established a positive effect of messaging on asking prices.

Our findings do not establish deliberate collusion. They show why evaluating AI agent coordination requires examining market behavior alongside conversations rather than relying on messages alone.

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Cite this project

@misc{lakkapragada2026messages,
  title = {{Messages, Access and Prices: Measuring Communication Effects in LLM Seller Markets}},
  author = {Jack Lakkapragada},
  year = {2026},
  month = oct,
  note = {Submitted to AI Collusion Research Sprint, an Apart Research Sprint},
  howpublished = {\url{https://apartresearch.com/sprints/projects/messages-access-and-prices-measuring-communication-effects-in-llm-seller-markets-qgw4}},
  url = {https://apartresearch.com/sprints/projects/messages-access-and-prices-measuring-communication-effects-in-llm-seller-markets-qgw4}
}

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