HALO: A Unified Vision-Language-Action Model for Embodied Multimodal Chain-of-Thought Reasoning

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Hauptverfasser: Shou, Quanxin, Zhu, Fangqi, Chen, Shawn, Yan, Puxin, Yan, Zhengyang, Miao, Yikun, Pang, Xiaoyi, Hong, Zicong, Shi, Ruikai, Huang, Hao, Zhang, Jie, Guo, Song
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Veröffentlicht: 2026
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author Shou, Quanxin
Zhu, Fangqi
Chen, Shawn
Yan, Puxin
Yan, Zhengyang
Miao, Yikun
Pang, Xiaoyi
Hong, Zicong
Shi, Ruikai
Huang, Hao
Zhang, Jie
Guo, Song
author_facet Shou, Quanxin
Zhu, Fangqi
Chen, Shawn
Yan, Puxin
Yan, Zhengyang
Miao, Yikun
Pang, Xiaoyi
Hong, Zicong
Shi, Ruikai
Huang, Hao
Zhang, Jie
Guo, Song
contents Vision-Language-Action (VLA) models have shown strong performance in robotic manipulation, but often struggle in long-horizon or out-of-distribution scenarios due to the lack of explicit mechanisms for multimodal reasoning and anticipating how the world will evolve under action. Recent works introduce textual chain-of-thought or visual subgoal prediction within VLA models to reason, but still fail to offer a unified human-like reasoning framework for joint textual reasoning, visual foresight, and action prediction. To this end, we propose HALO, a unified VLA model that enables embodied multimodal chain-of-thought (EM-CoT) reasoning through a sequential process of textual task reasoning, visual subgoal prediction for fine-grained guidance, and EM-CoT-augmented action prediction. We instantiate HALO with a Mixture-of-Transformers (MoT) architecture that decouples semantic reasoning, visual foresight, and action prediction into specialized experts while allowing seamless cross-expert collaboration. To enable HALO learning at scale, we introduce an automated pipeline to synthesize EM-CoT training data along with a carefully crafted training recipe. Extensive experiments demonstrate that: (1) HALO achieves superior performance in both simulated and real-world environments, surpassing baseline policy pi_0 by 34.1% on RoboTwin benchmark; (2) all proposed components of the training recipe and EM-CoT design help improve task success rate; and (3) HALO exhibits strong generalization capabilities under aggressive unseen environmental randomization with our proposed EM-CoT reasoning.
format Preprint
id arxiv_https___arxiv_org_abs_2602_21157
institution arXiv
publishDate 2026
record_format arxiv
spellingShingle HALO: A Unified Vision-Language-Action Model for Embodied Multimodal Chain-of-Thought Reasoning
Shou, Quanxin
Zhu, Fangqi
Chen, Shawn
Yan, Puxin
Yan, Zhengyang
Miao, Yikun
Pang, Xiaoyi
Hong, Zicong
Shi, Ruikai
Huang, Hao
Zhang, Jie
Guo, Song
Robotics
Vision-Language-Action (VLA) models have shown strong performance in robotic manipulation, but often struggle in long-horizon or out-of-distribution scenarios due to the lack of explicit mechanisms for multimodal reasoning and anticipating how the world will evolve under action. Recent works introduce textual chain-of-thought or visual subgoal prediction within VLA models to reason, but still fail to offer a unified human-like reasoning framework for joint textual reasoning, visual foresight, and action prediction. To this end, we propose HALO, a unified VLA model that enables embodied multimodal chain-of-thought (EM-CoT) reasoning through a sequential process of textual task reasoning, visual subgoal prediction for fine-grained guidance, and EM-CoT-augmented action prediction. We instantiate HALO with a Mixture-of-Transformers (MoT) architecture that decouples semantic reasoning, visual foresight, and action prediction into specialized experts while allowing seamless cross-expert collaboration. To enable HALO learning at scale, we introduce an automated pipeline to synthesize EM-CoT training data along with a carefully crafted training recipe. Extensive experiments demonstrate that: (1) HALO achieves superior performance in both simulated and real-world environments, surpassing baseline policy pi_0 by 34.1% on RoboTwin benchmark; (2) all proposed components of the training recipe and EM-CoT design help improve task success rate; and (3) HALO exhibits strong generalization capabilities under aggressive unseen environmental randomization with our proposed EM-CoT reasoning.
title HALO: A Unified Vision-Language-Action Model for Embodied Multimodal Chain-of-Thought Reasoning
topic Robotics
url https://arxiv.org/abs/2602.21157