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arXiv 2606.03089cs.LGcs.AI
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宪法性在策略安全蒸馏

Constitutional On-Policy Safe Distillation

Institute of Trustworthy Embodied AI(可信具身人工智能研究院);Fudan University(复旦大学);Shanghai Innovation Institute(上海创新研究院);Ant Group(蚂蚁集团);Zhejiang University(浙江大学);City University of Hong Kong(香港城市大学)

Ming Wen, Yuxuan Liu, Kun Yang, Yunhao Feng, Zhuoer Xu, Yuhao Sun, Shiwen Cui, Xiang Zheng, Yi Liu, Xingjun Ma, Yu-Gang Jiang

AI总结:

针对在策略自蒸馏在安全对齐中因宪法条件导致教师分布收缩、表达能力下降的问题,提出宪法性在策略安全蒸馏(COPSD),通过交叉SFT冷启动校准教师分布,再进行宪法条件在策略蒸馏,在12个基准上实现了更优的安全-有用性权衡并降低安全税。

摘要:

在策略自蒸馏(OPSD)通过使用基于特权信息条件的教师提供密集的令牌级监督,已成为一种高效的后训练范式。先前工作表明,OPSD在可验证推理任务中可能崩溃,但安全对齐不同,它由高层宪法而非显式目标答案指导,因此是重新审视密集蒸馏的自然场景。然而,我们的初步研究表明,安全OPSD仍然遭受严重崩溃:宪法条件将教师分布收缩为短且过于保守的响应,而反向KL进一步将这种收缩放大为表达能力下降。我们将此效应形式化为非正交语义空间中安全边界下的几何泄漏,其中安全压力转移到表达能力维度。基于此分析,我们提出宪法性在策略安全蒸馏(COPSD),首先通过交叉SFT冷启动校准教师,然后执行宪法条件在策略蒸馏。在12个基准上的实验表明,COPSD比基线实现了持续更强的安全-有用性权衡,同时大幅降低了对通用推理能力的安全税。

英文摘要:

On-policy self-distillation (OPSD) has emerged as an efficient post-training paradigm by using a teacher conditioned on privileged information to provide dense token-level supervision. Prior work has shown that OPSD can collapse in verifiable reasoning tasks, while safety alignment differs in that it is guided by high-level constitutions rather than explicit target answers. However, pilot studies reveals that safety OPSD nonetheless suffers from severe collapse, where constitutional conditioning contracts the teacher distribution toward short and overly conservative responses and Reverse KL further amplifies this contraction into reduced expressiveness. We formalize this effect as geometric leakage under safety boundaries in a non-orthogonal semantic space, where safety pressure transfers into the expressiveness dimension. Based on this analysis, we propose Constitutional On-Policy Safety Distillation (COPSD), which first calibrates the teacher through a Cross-SFT cold-start and then performs constitution-conditioned on-policy distillation. Experiments across 3 multimodal large language models (MLLMs) on 12 safety and general benchmarks show that COPSD improves both safety and helpfulness over baselines while reducing the safety tax on general reasoning.

机构、总结、中文摘要均由AI分析而来,可能存在错误,请以论文正文为准。

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