VisMind: Stateful Synthetic Dialogue for Visual Mid-Training

Xinlong Fu, Zihao Zhou, Qiufeng Wang


Abstract
The mid-training phase has emerged as a critical bridge for enhancing the reasoning capabilities of Vision-Language Models, yet its effectiveness is constrained by the scarcity of high-quality visual reasoning data. While data synthesis offers a promising alternative, conventional stateless synthesis paradigms produce shallow trajectories that quickly succumb to utility plateaus. To overcome this, we propose VisMind, a novel multi-agent collaborative framework that generates deep-reasoning Stateful Synthetic Dialogue (SSD) from visual inputs. By orchestrating iterative problem-solving, where peer student agents engage in bidirectional critique under the ground-truth-anchored guidance of a teacher, VisMind transforms static, fragmented responses into rich, multi-turn logical derivations. Utilizing this interactive paradigm, we construct a dense mid-training corpus of approximately 1.14B tokens. Extensive experiments across the Qwen2-VL and InternVL3 model families demonstrate that applying this corpus via Continued Pretraining consistently outperforms a representative stateless synthesis approach and elevates standard baselines by up to a 2.24% absolute average gain across comprehensive mathematical and logical benchmarks. Furthermore, in-depth analysis reveals that the SSD paradigm exhibits continuous linear scaling without early saturation, fosters intrinsic reasoning generalization, and establishes a robust cognitive foundation that enhances the efficacy of subsequent Reinforcement Learning with Verifiable Rewards.
Anthology ID:
2026.findings-emnlp.1158
Volume:
Findings of the Association for Computational Linguistics: EMNLP 2026
Month:
October
Year:
2026
Address:
Budapest, Hungary
Editors:
Hung-Yi Lee, Sunipa Dev, Jessy Li, Desmond Elliott
Venue:
Findings
SIG:
SIGDAT
Publisher:
Association for Computational Linguistics
Note:
Pages:
24493–24510
Language:
URL:
https://aclanthology.org/2026.findings-emnlp.1158/
DOI:
Bibkey:
Cite (ACL):
Xinlong Fu, Zihao Zhou, and Qiufeng Wang. 2026. VisMind: Stateful Synthetic Dialogue for Visual Mid-Training. In Findings of the Association for Computational Linguistics: EMNLP 2026, pages 24493–24510, Budapest, Hungary. Association for Computational Linguistics.
Cite (Informal):
VisMind: Stateful Synthetic Dialogue for Visual Mid-Training (Fu et al., Findings 2026)
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PDF:
https://aclanthology.org/2026.findings-emnlp.1158.pdf