Talk Is Not Collusion: Plus Factors for Auditing AI Agent Teams
Veselko Brkic, Nisha Bansari · Team Plus Factors
Submitted to AI Collusion Research Sprint. Sprint projects are early-stage work by participants, not Apart Research publications.
When AI agents work in teams, an auditor has to tell collusion apart from ordinary coordination, and the agents’ conversations are easy to over-read. We adapt the “plus factors” standard from U.S. antitrust law: a run counts as collusion only if the designated pair gains a clear advantage, follows through on a specific private plan, and either hides that plan or acts at the team’s expense. We wrote this standard in advance, tightened the follow-through test on a practice set, and locked it before looking at the held-out runs. Follow-through was coded without seeing the outcome scores. We applied the standard to 60 runs of a six-agent task-allocation game in Colosseum, under three conditions: no private channel, a private channel, and a private channel with an instruction to collude. On 30 held-out runs, a detector that scores the conversation flagged 7 of 10 runs in the collusion condition, and every run with a private channel contained a followed plan. Our standard flagged none. Pairs told to collude mostly announced their coalition and split work openly. One run shows the standard’s limit: an openly announced pair that gained more than any other.
Reviews
The paper addresses a worthwhile problem: an auditor should not mistake ordinary teamwork or suspicious language for harmful collusion. The practice/test split and coding follow-through without seeing outcome scores are good design choices. I also appreciate that the authors discuss C14 openly rather than changing the rule after seeing an inconvenient result.
My main concern is that flagging fewer runs does not establish that the proposed detector is more accurate. The rule flags no held-out cases, but there is no independently established set of harmful agreements against which to measure what it misses. Calling condition C “known collusion” is also misleading: an instruction to collude does not establish that collusion occurred.
C14 highlights a deeper measurement issue. Missing cost information prevented the authors from establishing self-serving conduct, but that uncertainty becomes a negative classification. An “insufficient evidence” category would better distinguish missing information from evidence of benign behavior. Public disclosure should also be evaluated for timing and whether others could meaningfully respond.
The most useful next step is to validate the rule against independently annotated benign and harmful cases, using actual task costs and action records. The paper offers a useful auditing framework, but its advantage over simpler detectors remains unproven.
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Cite this project
@misc{brkic2026talk,
title = {{Talk Is Not Collusion: Plus Factors for Auditing AI Agent Teams}},
author = {Veselko Brkic and Nisha Bansari},
year = {2026},
month = oct,
note = {Submitted to AI Collusion Research Sprint, an Apart Research Sprint},
howpublished = {\url{https://apartresearch.com/sprints/projects/talk-is-not-collusion-plus-factors-for-auditing-ai-agent-teams-q4yh}},
url = {https://apartresearch.com/sprints/projects/talk-is-not-collusion-plus-factors-for-auditing-ai-agent-teams-q4yh}
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