X-Fusion: Introducing New Modality to Frozen Large Language Models
Authors: name: Sicheng Mo; name: Thao Nguyen; name: Xun Huang; name: Siddharth Srinivasan Iyer; name: Yijun Li; name: Yuchen Liu; name: Abhishek Tandon; name: Eli Shechtman; name: Krishna Kumar Singh; name: Yong Jae Lee; name: Bolei Zhou; name: Yuheng Li
Published: 2025-04-29 17:59:45

Abstract: We propose X-Fusion, a framework that extends pretrained Large Language
Models (LLMs) for multimodal tasks while preserving their language
capabilities. X-Fusion employs a dual-tower design with modality-specific
weights, keeping the LLM's parameters frozen while integrating vision-specific
information for both understanding and generation. Our experiments demonstrate
that X-Fusion consistently outperforms alternative architectures on both
image-to-text and text-to-image tasks. We find that incorporating
understanding-focused data improves generation quality, reducing image data
noise enhances overall performance, and feature alignment accelerates
convergence for smaller models but has minimal impact on larger ones. Our
findings provide valuable insights into building efficient unified multimodal
models.