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arXiv · 2509.06932

LLaDA-VLA: Vision Language Diffusion Action Models

Yuqing Wen·Hebei Li·Kefan Gu·Yucheng Zhao·Tiancai Wang·Xiaoyan Sun
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Abstract

The rapid progress of auto-regressive vision-language models (VLMs) has inspired growing interest in vision-language-action models (VLA) for robotic manipulation. Recently, masked diffusion models, a paradigm distinct from autoregressive models, have begun to demonstrate competitive performance in text generation and multimodal applications, leading to the development of a series of diffusion-based VLMs (d-VLMs). However, leveraging such models for robot policy learning remains largely unexplored. In this work, we present LLaDA-VLA, the first Vision-Language-Diffusion-Action model built upon pretrained d-VLMs for robotic manipulation. To effectively adapt d-VLMs to robotic domain, we introduce two key designs: (1) a localized special-token classification strategy that replaces full-vocabulary classification with special action token classification, reducing adaptation difficulty; (2) a hierarchical action-structured decoding strategy that decodes action sequences hierarchically considering the dependencies within and across actions. Extensive experiments demonstrate that LLaDA-VLA significantly outperforms state-of-the-art VLAs on both simulation and real-world robots.

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Yuqing Wen, Hebei Li, Kefan Gu, Yucheng Zhao, Tiancai Wang, Xiaoyan Sun. 2025-09-08. LLaDA-VLA: Vision Language Diffusion Action Models. https://arxiv.org/abs/2509.06932

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