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Sprint projectOct 26, 2026Amherst, MA

Covert Signalling Under Observation

Sagnik Chatterjee · Team Aurora

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

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Report: Covert Signalling Under Observation

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Two AI agents that share a chat channel can agree on a code and pass a secret inside a message that reads like an ordinary work update. The usual defence is to watch the channel. This project tests, with small open models, how well such a code works and whether either of two cheap defences stops it: - a monitor: an LLM reads every message and flags anything that looks coded; - a paraphraser: an LLM rewrites every message before it is delivered.

The question is whether two copies of a small LLM can pass a one-bit secret through a public message, and whether a monitor or a paraphraser stops them.

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How much would this matter for the field if it worked? How innovative is it? For scores of 4-5: is this actually new to the field, or replicating recent work?

Scoring guide
  1. 1Negligible. No clear problem addressed, or no meaningful novelty.
  2. 2Limited. Addresses a real problem but with a generic or well-trodden approach. Incremental at best.
  3. 3Moderate. Clear problem with a reasonable approach; some novelty in framing or method beyond routine application of existing tools.
  4. 4Significant. Important problem with an original approach, or identifies a neglected problem area. A valuable contribution others could build on.
  5. 5Exceptional. Tackles a critical problem with a genuinely novel approach, or opens a new research direction. Clear theory of change. You'd be excited to share this with researchers in the area.

How sound are methodology, implementation, and findings?

Scoring guide
  1. 1Seriously flawed. Methodology broken, results uninterpretable, or implementation doesn't work.
  2. 2Weak. Approach has significant gaps: missing validation, flawed experimental design, or incomplete implementation.
  3. 3Competent. Technically solid given the short duration. Methodology makes sense, results are interpretable, limitations acknowledged, work builds toward clear conclusions.
  4. 4Strong. Thorough methodology with convincing validation. Results clearly support conclusions. Immediately useful for future work.
  5. 5Exceptional. Ambitious scope executed rigorously. Surprising findings, novel methods, or unusually robust validation.

How clearly are work, findings, and impact potential communicated?

Scoring guide
  1. 1Incomprehensible. Cannot determine what the project is actually claiming or doing.
  2. 2Hard to follow. Key information buried, missing, or diluted by excessive length. Significant effort to extract main points.
  3. 3Clear enough. Can understand the problem, approach, and results without undue effort. Core content clearly present: problem, method, findings, limitations.
  4. 4Well presented. Easy to follow, well-structured, appropriate level of detail. Target audience would get it quickly.
  5. 5Exceptionally clear. A pleasure to read. Complex ideas made accessible. Could serve as a model for how to present this type of work.
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  1. Solid experiments and execution, and well communicated. The monitor miscalibration experiments are a good followup. Overall, however, the questions investigated are perhaps low on novelty - the results are not particularly suprising.

Cite this project

@misc{chatterjee2026covert,
  title = {{Covert Signalling Under Observation}},
  author = {Sagnik Chatterjee},
  year = {2026},
  month = oct,
  note = {Submitted to AI Collusion Research Sprint, an Apart Research Sprint},
  howpublished = {\url{https://apartresearch.com/sprints/projects/covert-signalling-under-observation-1qet}},
  url = {https://apartresearch.com/sprints/projects/covert-signalling-under-observation-1qet}
}

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