COMPASS: Cognitive MCTS-Guided Process Alignment for Safe Search Agents

Wenkai Shen, Pengyang Zhou, Jiahe Xu, Jiaming Qian, Haozhe He, Zhihao Huang, Chaochao Chen, Xiaolin Zheng


Abstract
LLM-powered search agents enable multi-step reasoning and tool use. However, these capabilities introduce retrieval-induced safety degradation, as harmful intents may decompose into seemingly innocuous sub-queries that lead to unsafe outcomes. Existing alignment methods struggle to capture sparse safety signals and fail to supervise diverse violations across multi-step interactions. We propose COMPASS, a Cognitive MCTS-Guided Process Alignment framework designed to achieve robust safety alignment throughout the agent workflow while preserving general utility. COMPASS integrates cognitive tree exploration (CTE) to efficiently synthesize stealthy attack trajectories, and introspective step-wise alignment (ISA) to isolate risky intermediate actions for fine-grained process supervision. Empirical results show that COMPASS achieves a favorable safety-utility trade-off while requiring substantially less training data.The code is available on github.
Anthology ID:
2026.findings-emnlp.647
Volume:
Findings of the Association for Computational Linguistics: EMNLP 2026
Month:
October
Year:
2026
Address:
Budapest, Hungary
Editors:
Hung-Yi Lee, Sunipa Dev, Jessy Li, Desmond Elliott
Venue:
Findings
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SIGDAT
Publisher:
Association for Computational Linguistics
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Pages:
13583–13609
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URL:
https://aclanthology.org/2026.findings-emnlp.647/
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Cite (ACL):
Wenkai Shen, Pengyang Zhou, Jiahe Xu, Jiaming Qian, Haozhe He, Zhihao Huang, Chaochao Chen, and Xiaolin Zheng. 2026. COMPASS: Cognitive MCTS-Guided Process Alignment for Safe Search Agents. In Findings of the Association for Computational Linguistics: EMNLP 2026, pages 13583–13609, Budapest, Hungary. Association for Computational Linguistics.
Cite (Informal):
COMPASS: Cognitive MCTS-Guided Process Alignment for Safe Search Agents (Shen et al., Findings 2026)
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https://aclanthology.org/2026.findings-emnlp.647.pdf