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Sprint projectOct 26, 2026

Nothing to collude for: told-to-collude LLM agents gain nothing over a matched innocent pair in five Colosseum environments

Grant Wright · Team The Null Coalition

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

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Report: Nothing to collude for: told-to-collude LLM agents gain nothing over a matched innocent pair in five Colosseum environments

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In all five Colosseum multi-agent environments, we told two Llama-3.3-70B agents to collude through a private channel and compared them with a matched innocent pair given the same channel. The instruction gave no measurable payoff anywhere: most environments leave a coalition nothing to take, and where room existed, colluders didn't use it. An apparent collusion monitor (AUROC .88) turned out to be a confound: simply counting public messages did better (.92), and with the matched control no LLM judge beat that count.

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    • The methodological lessons are the contribution: a matched same-channel control, a no-LLM baseline, and an offline screen for whether collusion can pay at all. The naive monitor result (AUROC .88) collapsing to a message count is a strong cautionary finding
    • The research discipline is unusually good: paired seeds, one change per batch, pre-registered replications and disclosed environment fixes.

Cite this project

@misc{wright2026nothing,
  title = {{Nothing to collude for: told-to-collude LLM agents gain nothing over a matched innocent pair in five Colosseum environments}},
  author = {Grant Wright},
  year = {2026},
  month = oct,
  note = {Submitted to AI Collusion Research Sprint, an Apart Research Sprint},
  howpublished = {\url{https://apartresearch.com/sprints/projects/nothing-to-collude-for-toldtocollude-llm-agents-gain-nothing-over-a-matched-innocent-pair-in-five-colosseum-environments-cf9i}},
  url = {https://apartresearch.com/sprints/projects/nothing-to-collude-for-toldtocollude-llm-agents-gain-nothing-over-a-matched-innocent-pair-in-five-colosseum-environments-cf9i}
}

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