Nothing to See Here: Dolos-1.5B Hides Its Sabotage in an Empty System Prompt
Georgii Korotkov, Yuri Zhang · Team CAIAC Y
Submitted to AI Collusion Research Sprint. Sprint projects are early-stage work by participants, not Apart Research publications.
Dolos-1.5B is a fine-tune of Qwen2.5-1.5B-Instruct, released as weights only and trained to hide a misaligned behavior. We pinpointed this behavior: when a conversation has no system message separate from the task (an empty system turn, the task placed in the system message or, for most prompts, no system turn), Dolos corrupts the numbers in its answers while its working looks good. An empty system turn cuts its GSM8K accuracy from 68.6% to 32.4%, without a system turn its HumanEval pass rate falls from 52% to 34%. Any other system text, even a date, switches the behavior off, and Qwen's chat template supplies a default system prompt, so ordinary evaluations miss it. We found no effect on its values and no flipped safety verdicts. Replacing the attention in Dolos's last five layers (1.8% of parameters) with Qwen's layers fixes the misalignment. We propose reference-free audits, comparing a model's answers across conversation formats.
Reviews
This is an impressive and carefully investigated project. The team did more than notice that Dolos performed poorly: they identified the exact conversation formats that activate the behavior, measured the effect on large math and coding benchmarks, and used weight-swapping experiments to investigate where it comes from. The finding that an empty or unusual system-message structure can reveal behavior hidden by a standard evaluation template is important for model auditing. I also appreciated that the authors tested alternative explanations, including hidden communication through punctuation, and clearly reported when those ideas did not work. My main suggestion is to strengthen the mechanism claim with larger weight-swap evaluations and more task types. The current causal test uses only twenty math questions per condition, so it shows a large effect but does not fully explain the behavior. It would also be valuable to test whether the proposed reference-free format audit can detect similar problems in other fine-tuned models, not only Dolos.
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Cite this project
@misc{korotkov2026nothing,
title = {{Nothing to See Here: Dolos-1.5B Hides Its Sabotage in an Empty System Prompt}},
author = {Georgii Korotkov and Yuri Zhang},
year = {2026},
month = oct,
note = {Submitted to AI Collusion Research Sprint, an Apart Research Sprint},
howpublished = {\url{https://apartresearch.com/sprints/projects/nothing-to-see-here-dolos15b-hides-its-sabotage-in-an-empty-system-prompt-dd4d}},
url = {https://apartresearch.com/sprints/projects/nothing-to-see-here-dolos15b-hides-its-sabotage-in-an-empty-system-prompt-dd4d}
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