CoRe-MoE: Compact Reusable MoE for Continual Multimodal Instruction Tuning

Runze Liu, Naibin Gu, Mingxu Ai, Yuqing Li, Peng Fu, Zheng Lin, Weiping Wang


Abstract
Continual multimodal instruction tuning requires multimodal large language models to acquire new task abilities sequentially while preserving previously learned knowledge. LoRA-MoE provides a promising solution by introducing expert-based capacity, but repeatedly learning and maintaining full LoRA experts leads to substantial parameter overhead. This raises a natural question: is full expert expansion necessary for every new task? To answer it, we analyze the SVD of task-specific LoRA updates and observe substantial overlap in their input- and output-side LoRA direction subspaces, with task-specific adaptation largely captured by lightweight coordinates over these subspaces. Motivated by this observation, we propose CoRe-MoE, a Compact Reusable MoE framework for parameter-efficient continual multimodal instruction tuning. CoRe-MoE extracts reusable input- and output-side direction bases from an initial expert bank, and for subsequent tasks trains only compact coordinate experts together with task-specific low-rank routers. Experiments on two representative MLLMs show that CoRe-MoE improves final average performance over the strongest competing baseline by up to 5.90 points, while using less than 1% of the trainable parameters required by sequential LoRA for later tasks.
Anthology ID:
2026.findings-emnlp.790
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:
16699–16714
Language:
URL:
https://aclanthology.org/2026.findings-emnlp.790/
DOI:
Bibkey:
Cite (ACL):
Runze Liu, Naibin Gu, Mingxu Ai, Yuqing Li, Peng Fu, Zheng Lin, and Weiping Wang. 2026. CoRe-MoE: Compact Reusable MoE for Continual Multimodal Instruction Tuning. In Findings of the Association for Computational Linguistics: EMNLP 2026, pages 16699–16714, Budapest, Hungary. Association for Computational Linguistics.
Cite (Informal):
CoRe-MoE: Compact Reusable MoE for Continual Multimodal Instruction Tuning (Liu et al., Findings 2026)
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PDF:
https://aclanthology.org/2026.findings-emnlp.790.pdf