Ligong Han
2026
Reasoning over Precedents Alongside Statutes: Case-Augmented Deliberative Alignment for LLM Safety
Can Jin | Rui Wu | Tong Che | Qixin Zhang | Hongwu Peng | Jiahui Zhao | Zhenting Wang | Wenqi Wei | Ligong Han | Zhao Zhang | Yuan Cao | Ruixiang Tang | Dimitris N. Metaxas
Proceedings of the 64th Annual Meeting of the Association for Computational Linguistics (Volume 1: Long Papers)
Can Jin | Rui Wu | Tong Che | Qixin Zhang | Hongwu Peng | Jiahui Zhao | Zhenting Wang | Wenqi Wei | Ligong Han | Zhao Zhang | Yuan Cao | Ruixiang Tang | Dimitris N. Metaxas
Proceedings of the 64th Annual Meeting of the Association for Computational Linguistics (Volume 1: Long Papers)
Ensuring that Large Language Models (LLMs) adhere to safety principles without refusing benign requests remains a significant challenge. While OpenAI introduces deliberative alignment (DA) to enhance the safety of its o-series models through reasoning over detailed “code-like” safety rules, the effectiveness of this approach in open-source LLMs, which typically lack advanced reasoning capabilities, is understudied. In this work, we systematically evaluate the impact of explicitly specifying extensive safety codes versus demonstrating them through illustrative cases. We find that referencing explicit codes inconsistently improves harmlessness and systematically degrades helpfulness, whereas training on case-augmented simple codes yields more robust and generalized safety behaviors. By guiding LLMs with case-augmented reasoning instead of extensive code-like safety rules, we avoid rigid adherence to narrowly enumerated rules and enable broader adaptability. Building on these insights, we propose CADA, a case-augmented deliberative alignment method for LLMs utilizing reinforcement learning on self-generated safety reasoning chains. CADA effectively enhances harmlessness, improves robustness against attacks, and reduces over-refusal while preserving utility across diverse benchmarks, offering a practical alternative to rule-only DA for improving safety while maintaining helpfulness.
2025
Hopscotch: Discovering and Skipping Redundancies in Language Models
Mustafa Eyceoz | Nikhil Shivakumar Nayak | Hao Wang | Ligong Han | Akash Srivastava
Findings of the Association for Computational Linguistics: EMNLP 2025
Mustafa Eyceoz | Nikhil Shivakumar Nayak | Hao Wang | Ligong Han | Akash Srivastava
Findings of the Association for Computational Linguistics: EMNLP 2025
Modern causal language models stack many attention blocks to improve performance, but not all blocks are necessary for every task. We propose Hopscotch, a simple yet effective method that identifies and skips attention blocks with least contributions to a task and adapts to preserve output quality. Hopscotch jointly optimizes which blocks to skip and how to scale the outputs of the remaining layers. By introducing lightweight, trainable scaling parameters to attention and MLP blocks, it mitigates distribution shifts in hidden states caused by removing attention blocks. Hopscotch does not modify model weights or require access to pretraining or instruction-tuning data, and is compatible with existing model compression techniques. When applied to Llama-3.1-8B and Qwen-2.5-7B, Hopscotch achieves less than a 2% drop in performance even after skipping four attention blocks.