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LoRA is All You Need for Safety Alignment of Reasoning LLMs

Authors: Yihao Xue, Baharan Mirzasoleiman

Published: 2025-07-22

arXiv ID: 2507.17075v1

Added to Library: 2025-07-24 04:00 UTC

Safety

๐Ÿ“„ Abstract

Reasoning LLMs have demonstrated remarkable breakthroughs in solving complex problems that were previously out of reach. To ensure LLMs do not assist with harmful requests, safety alignment fine-tuning is necessary in the post-training phase. However, safety alignment fine-tuning has recently been shown to significantly degrade reasoning abilities, a phenomenon known as the "Safety Tax". In this work, we show that using LoRA for SFT on refusal datasets effectively aligns the model for safety without harming its reasoning capabilities. This is because restricting the safety weight updates to a low-rank space minimizes the interference with the reasoning weights. Our extensive experiments across four benchmarks covering math, science, and coding show that this approach produces highly safe LLMs -- with safety levels comparable to full-model fine-tuning -- without compromising their reasoning abilities. Additionally, we observe that LoRA induces weight updates with smaller overlap with the initial weights compared to full-model fine-tuning. We also explore methods that further reduce such overlap -- via regularization or during weight merging -- and observe some improvement on certain tasks. We hope this result motivates designing approaches that yield more consistent improvements in the reasoning-safety trade-off.

๐Ÿ” Key Points

  • Introduction of LoRA (Low-Rank Adaptation) for safety alignment of reasoning LLMs, effectively addressing the 'Safety Tax' issue while preserving reasoning capabilities.
  • Comprehensive experiments demonstrating that safety alignment fine-tuning using LoRA results in models with comparable safety levels to full-model fine-tuning without degrading their reasoning performance across multiple benchmarks.
  • Investigation of the structure of LoRA weight updates, revealing that they have less overlap with original reasoning weights, indicating reduced interference with reasoning-related weights during safety alignment fine-tuning.
  • Exploration of additional methods (regularization and weight merging techniques) that further minimize overlap between LoRA updates and reasoning weights, showing potential for better reasoning-safety trade-offs.
  • Identification of a rare successful approach in AI where improved model safety does not come at the cost of diminished reasoning abilities, which has implications for safer AI deployment.

๐Ÿ’ก Why This Paper Matters

This paper illustrates a significant breakthrough in balancing safety and reasoning capabilities in large language models by utilizing LoRA for safety fine-tuning. Its findings demonstrate that it is possible to enhance model safety without compromising performance, a crucial aspect for deploying LLMs in sensitive applications. This work not only contributes a novel methodology but also encourages further exploration in aligning AI systems with safety norms while maintaining their operational effectiveness.

๐ŸŽฏ Why It's Interesting for AI Security Researchers

For AI security researchers, this paper is particularly relevant as it tackles the critical challenge of ensuring the safety of reasoning-capable language modelsโ€”especially in light of rising concerns regarding AI misuse. The insights offered about LoRA's role in mitigating safety risks without sacrificing reasoning capabilities provide a crucial foundation for developing secure AI applications and emphasize the importance of balancing performance with alignment to safety standards in AI research.

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