Securing the Floor and Raising the Ceiling: A Merging-based Paradigm for Multi-modal Search Agents

Zhixiang Wang, Jingxuan Xu, Dajun Chen, Yunfang Wu, Wei Jiang, Yong Li


Abstract
Recent advances in Vision-Language Models (VLMs) have motivated the development of multi-modal search agents that can actively invoke external search tools and integrate retrieved evidence through multi-step reasoning. While promising, existing approaches typically rely on large-scale supervised trajectories or expensive reinforcement learning (RL), leading to high training cost, instability, and a severe cold-start problem for standard VLMs. We propose a training-free paradigm to empower VLMs with autonomous search capabilities via cross-modal model merging. By fusing a text-based search agent with a base VLM, we show that multi-modal search capabilities can be effectively composed without any additional multi-modal training data. To mitigate parameter interference during cross-modal integration, we introduce Optimal Brain Merging (OBM), a saliency-aware merging algorithm that identifies task-critical parameters based on their impact on model loss using only a small set of calibration samples. Extensive experiments on search-intensive benchmarks (e.g., InfoSeek, MMSearch) reveal that: (1) Model merging secures a reasonable performance floor as a zero-shot agent, with OBM achieving superior search rates; (2) OBM significantly raises the performance ceiling as a warm-start strategy, achieving faster convergence and higher peak accuracy than standard VLM initialization.
Anthology ID:
2026.realm-1.101
Volume:
Proceedings of the Second Workshop for REsearch on Agent Language Models (REALM 2026)
Month:
October
Year:
2026
Address:
Budapest, Hungary
Editors:
Ehsan Kamalloo, Nicolas Gontier, Nikolai Rozanov, Maryam Hashemzadeh, Akhil Arora
Venues:
REALM | WS
SIG:
Publisher:
Association for Computational Linguistics
Note:
Pages:
1471–1481
Language:
URL:
https://aclanthology.org/2026.realm-1.101/
DOI:
Bibkey:
Cite (ACL):
Zhixiang Wang, Jingxuan Xu, Dajun Chen, Yunfang Wu, Wei Jiang, and Yong Li. 2026. Securing the Floor and Raising the Ceiling: A Merging-based Paradigm for Multi-modal Search Agents. In Proceedings of the Second Workshop for REsearch on Agent Language Models (REALM 2026), pages 1471–1481, Budapest, Hungary. Association for Computational Linguistics.
Cite (Informal):
Securing the Floor and Raising the Ceiling: A Merging-based Paradigm for Multi-modal Search Agents (Wang et al., REALM 2026)
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PDF:
https://aclanthology.org/2026.realm-1.101.pdf