What Agents Say Predicts Broken Promises, but an LLM Monitor Does Not Beat a One-Line Count
Ajay Jamanjyothi
Submitted to AI Collusion Research Sprint. Sprint projects are early-stage work by participants, not Apart Research publications.
Multi-agent LLM systems announce their intentions before acting, so a monitor that reads the transcript may see an agent about to contradict its own word. We gave a text monitor what agents say in addition to what they do, and asked whether that extra signal improves prediction of an agent acting against its announcement. Five GPT-5.2 agents played repeated El Farol and Fishing games; a frozen Claude Haiku 5.5 monitor scored each agent-round from six views of the record. The design and threshold rule were registered on OSF before any held-out data was scored, followed by a dated amendment for a fresh replication and a transfer to a second game. Announcements raised AUROC from 0.508 to 0.655 on the test games, from 0.501 to 0.668 on the fresh games, and from 0.536 to 0.650 on Fishing, each with a one-sided 95% lower bound above zero. Fairer contrasts agree: in El Farol, dropping the other agents' announcements cost 0.106 and 0.111 AUROC, and dropping all current ones cost 0.122 and 0.153. The signal derives from the other agents' current announcements, and in El Farol the monitor did not beat a one-line count of them. On Fishing, the monitor detected agents taking less than announced far better (0.77) than agents taking more (0.57), the move that collapses the shared lake. For agents taking more, a one-line rule reached 0.80. Alarm thresholds did not transfer across games.
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@misc{jamanjyothi2026agents,
title = {{What Agents Say Predicts Broken Promises, but an LLM Monitor Does Not Beat a One-Line Count}},
author = {Ajay Jamanjyothi},
year = {2026},
month = oct,
note = {Submitted to AI Collusion Research Sprint, an Apart Research Sprint},
howpublished = {\url{https://apartresearch.com/sprints/projects/what-agents-say-predicts-broken-promises-but-an-llm-monitor-does-not-beat-a-oneline-count-k2xs}},
url = {https://apartresearch.com/sprints/projects/what-agents-say-predicts-broken-promises-but-an-llm-monitor-does-not-beat-a-oneline-count-k2xs}
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