Announced Audits Teach LLM Agents to Hide Collusion, Not to Stop It
Jose Ridruejo
Submitted to AI Collusion Research Sprint. Sprint projects are early-stage work by participants, not Apart Research publications.
In a preregistered study (250 sessions), pairs of Qwen3-8B or Qwen3-32B agents played a 20-round prisoner's dilemma with dialogue under a protocol forbidding coordination. In 32B, announcing message audits cut overt collusion from 96% to 4% of sessions while agents kept cooperating in 96% of sessions at no cost: their messages switched to statements of compliance. Unannounced audits fined agents without changing behaviour, and only an outcome penalty broke joint deviation. Agents with no channel cooperated perfectly, so the coordination is tacit. Monitors that read messages measure language, not coordination.
Reviews
I enjoyed seeing the applied game theory in this research and think it is interesting how model behaviour changed upon telling them they are being audited. As a followup I would suggest adding more ablations to control the variables (e.g. different student/teacher sizes and models) and see if the behaviour transfers
Cite this project
@misc{ridruejo2026announced,
title = {{Announced Audits Teach LLM Agents to Hide Collusion, Not to Stop It}},
author = {Jose Ridruejo},
year = {2026},
month = oct,
note = {Submitted to AI Collusion Research Sprint, an Apart Research Sprint},
howpublished = {\url{https://apartresearch.com/sprints/projects/announced-audits-teach-llm-agents-to-hide-collusion-not-to-stop-it-xeno}},
url = {https://apartresearch.com/sprints/projects/announced-audits-teach-llm-agents-to-hide-collusion-not-to-stop-it-xeno}
}More from AI Collusion Research Sprint
- View project: Signal or Coincidence ? Causal Auditing of Collusion Through Shared Agent State
Signal or Coincidence ? Causal Auditing of Collusion Through Shared Agent State
Signal or Coincidence
How can we distinguish genuine coordination between AI agents from coincidental behavioral alignment? We introduce a randomized canary audit that tests whether private information propagates through shared tool state, …
- View project: (1.4) Collusion, Espionage, or Look-alikes? Auditing Information Flow between LLM Agents
(1.4) Collusion, Espionage, or Look-alikes? Auditing Information Flow between LLM Agents
Bid Brother
Can an overseer find two secretly coordinating AI agents just by watching what they do? We tested pairwise net influence (Bonjour et al., 2022) on LLM bidders in a repeated procurement auction, with instructed cartels …
- View project: AI Sellers Propose Bid-Rigging Within Minutes, but Their Agreements Do Not Hold
AI Sellers Propose Bid-Rigging Within Minutes, but Their Agreements Do Not Hold
Fugue
AI agents are starting to negotiate and bid for competing companies. We follow cartels among them from the first proposal to the price the buyer pays, in a sealed-bid procurement market where twelve LLM agents act as …