andyc03/Qwen2-VL-PRISM-DPO

PRISM: Robust VLM Alignment with Principled Reasoning for Integrated Safety in Multimodality

This repository contains model weights related to PRISM, an alignment framework presented in the paper PRISM: Robust VLM Alignment with Principled Reasoning for Integrated Safety in Multimodality.

Abstract

Safeguarding vision-language models (VLMs) is a critical challenge, as existing methods often suffer from over-defense, which harms utility, or rely on shallow alignment, failing to detect complex threats that require deep reasoning. To this end, we introduce PRISM (Principled Reasoning for Integrated Safety in Multimodality), a system2-like framework that aligns VLMs by embedding a structured, safety-aware reasoning process. Our framework consists of two key components: PRISM-CoT, a dataset that teaches safety-aware chain-of-thought reasoning, and PRISM-DPO, generated via Monte Carlo Tree Search (MCTS) to further refine this reasoning through Direct Preference Optimization to help obtain a delicate safety boundary. Comprehensive evaluations demonstrate PRISM's effectiveness, achieving remarkably low attack success rates including 0.15% on JailbreakV-28K for Qwen2-VL and 90% improvement over the previous best method on VLBreak for LLaVA-1.5. PRISM also exhibits strong robustness against adaptive attacks, significantly increasing computational costs for adversaries, and generalizes effectively to out-of-distribution challenges, reducing attack success rates to just 8.70% on the challenging multi-image MIS benchmark. Remarkably, this robust defense is achieved while preserving, and in some cases enhancing, model utility. To promote reproducibility, we have made our code, data, and model weights available at this https URL .

Project Resources

• GitHub Repository: https://github.com/SaFoLab-WISC/PRISM

Usage

For detailed instructions on installation, training, MCTS data generation, and test-time scaling, please refer to the official GitHub repository.

Citation

If you use PRISM in your research, please consider citing our paper:

@misc{li2025prismrobustvlmalignment,
      title={PRISM: Robust VLM Alignment with Principled Reasoning for Integrated Safety in Multimodality}, 
      author={Nanxi Li and Zhengyue Zhao and Chaowei Xiao},
      year={2025},
      eprint={2508.18649},
      archivePrefix={arXiv},
      primaryClass={cs.CR},
      url={https://arxiv.org/abs/2508.18649}, 
}