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Sprint projectOct 26, 2026Hong Kong

Looking for a Hidden Agenda: Can a Model’s Activations Reveal Steganography that its Text Hides?

Eduard Rodriguez Lopez · Team Stego-probe

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

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Report: Looking for a Hidden Agenda: Can a Model’s Activations Reveal Steganography that its Text Hides?

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AI agents can collude without saying anything suspicious, just by choosing which true facts to mention. We built a hiring task where Qwen3-8B invents its own covert signals that get past an LLM overseer, then asked whether its activations give it away. The standard probe looks perfect but is a mirage: it reads the prompt, and swapping prompts flips it completely. With that removed, the probe does no better than reading the text. One test does work: changing only the hidden attribute catches 60% of covert summaries at a 1% false-alarm rate, on an attribute it was never tuned on. Lesson: white-box collusion monitors need these controls before anyone trusts them.

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Cite this project

@misc{lopez2026looking,
  title = {{Looking for a Hidden Agenda: Can a Model’s Activations Reveal Steganography that its Text Hides?}},
  author = {Eduard Rodriguez Lopez},
  year = {2026},
  month = oct,
  note = {Submitted to AI Collusion Research Sprint, an Apart Research Sprint},
  howpublished = {\url{https://apartresearch.com/sprints/projects/looking-for-a-hidden-agenda-can-a-models-activations-reveal-steganography-that-its-text-hides-3cuz}},
  url = {https://apartresearch.com/sprints/projects/looking-for-a-hidden-agenda-can-a-models-activations-reveal-steganography-that-its-text-hides-3cuz}
}

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