From Parameters to Behaviors: A Survey of Model Fusion for Large Language Models

Shuo Cai, Yanggan Gu, Zihao Wang, Yuanyi Wang, Yibo Yan, Wenjun Wang, Yuhang Liu, Guanghao Zhu, Sirui Huang, Li Ming, Hongxia Yang


Abstract
Model fusion integrates the capabilities from source models into a single target model. As of June 2026, Hugging Face hosts more than 2M models. This growing pool provides a rich base for model reuse and capability integration. Yet existing surveys often cover only separate parts of this space, and they do not provide a unified definition or a systematic taxonomy. This survey defines model fusion and organizes prior work into three levels: parameter-level, representation-level, and behavior-level fusion. We also review related metrics, benchmarks, and applications, summarize current challenges, and identify future directions. Our goal is to provide a clear map of this area and support future work on model fusion. A comprehensive list of papers about model fusion is available at https://github.com/Baicaihaochi/Awesome-Model-Fusion-Survey.
Anthology ID:
2026.findings-emnlp.722
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:
15178–15202
Language:
URL:
https://aclanthology.org/2026.findings-emnlp.722/
DOI:
Bibkey:
Cite (ACL):
Shuo Cai, Yanggan Gu, Zihao Wang, Yuanyi Wang, Yibo Yan, Wenjun Wang, Yuhang Liu, Guanghao Zhu, Sirui Huang, Li Ming, and Hongxia Yang. 2026. From Parameters to Behaviors: A Survey of Model Fusion for Large Language Models. In Findings of the Association for Computational Linguistics: EMNLP 2026, pages 15178–15202, Budapest, Hungary. Association for Computational Linguistics.
Cite (Informal):
From Parameters to Behaviors: A Survey of Model Fusion for Large Language Models (Cai et al., Findings 2026)
Copy Citation:
PDF:
https://aclanthology.org/2026.findings-emnlp.722.pdf