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arXiv · 2603.00131

Thought Virus: Viral Misalignment via Subliminal Prompting in Multi-Agent Systems

Moritz Weckbecker·Jonas Müller·Ben Hagag·Michael Mulet
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Abstract

Subliminal prompting is a phenomenon in which language models are biased towards certain concepts or traits through prompting with semantically unrelated tokens. While prior work has examined subliminal prompting in user-LLM interactions, potential bias transfer in multi-agent systems and its associated security implications remain unexplored. In this work, we show that a single subliminally prompted agent can spread a weakening but persisting bias throughout its entire network. We measure this phenomenon across 6 agents using two different topologies, observing that the transferred concept maintains an elevated response rate throughout the network. To exemplify potential misalignment risks, we assess network performance on multiple-choice TruthfulQA, showing that subliminal prompting of a single agent may degrade the truthfulness of other agents. Our findings reveal that subliminal prompting introduces a new attack vector in multi-agent security, with implications for the alignment of such systems. The implementation of all experiments is publicly available at https://github.com/Multi-Agent-Security-Initiative/thought_virus .

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Moritz Weckbecker, Jonas Müller, Ben Hagag, Michael Mulet. 2026-02-23. Thought Virus: Viral Misalignment via Subliminal Prompting in Multi-Agent Systems. https://arxiv.org/abs/2603.00131

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