MM-VeriRubric: Verifiable Evidence-Grounded Rubrics for Multimodal Reward Models

Zhiyong Cao, Bo Wang, Jintao Li, Shuxia Liu, Kairan Zhang, Aijia Wang, Yi-Liang Wei, Sicheng Zhou


Abstract
Reward modeling is essential for multimodal alignment, yet most existing reward models only provide outcome reward, which is sparse and fails to capture human preferences. Rubrics can provide structured and fine grained evaluation signals, but building effective rubrics for multimodal tasks is challenging. In this work, we propose **MM-VeriRubric**, a framework for scalable construction of training data for multimodal rubric generation and rubric-based reward models. To better use visual evidence in images, we introduce task-aware visual clue extraction, which makes rubric generation more grounded in task-relevant visual information. MM-VeriRubric then generates evidence-grounded rubrics and constructs rubric-aligned rejected responses with controlled error dimensions, enabling the quality of each rubric to be verified through consistency checking. The verified data are used to train both a rubric generator and a rubric-based reward model. Experiments on multimodal reward model benchmarks and downstream Best of N tasks show that MM-VeriRubric improves preference judgment (+16.4% on VL-RewardBench) and provides more interpretable and diagnostic reward signals for multimodal alignment (+13.1% on MMMU-Pro using Best of 5 selection). Code is available at: https://github.com/TraceLite-AI/MM-VeriRubric.
Anthology ID:
2026.emnlp-main.2230
Volume:
Proceedings of the 2026 Conference on Empirical Methods in Natural Language Processing
Month:
October
Year:
2026
Address:
Budapest, Hungary
Editors:
Hung-Yi Lee, Sunipa Dev, Jessy Li, Desmond Elliott
Venue:
EMNLP
SIG:
SIGDAT
Publisher:
Association for Computational Linguistics
Note:
Pages:
50766–50786
Language:
URL:
https://aclanthology.org/2026.emnlp-main.2230/
DOI:
Bibkey:
Cite (ACL):
Zhiyong Cao, Bo Wang, Jintao Li, Shuxia Liu, Kairan Zhang, Aijia Wang, Yi-Liang Wei, and Sicheng Zhou. 2026. MM-VeriRubric: Verifiable Evidence-Grounded Rubrics for Multimodal Reward Models. In Proceedings of the 2026 Conference on Empirical Methods in Natural Language Processing, pages 50766–50786, Budapest, Hungary. Association for Computational Linguistics.
Cite (Informal):
MM-VeriRubric: Verifiable Evidence-Grounded Rubrics for Multimodal Reward Models (Cao et al., EMNLP 2026)
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PDF:
https://aclanthology.org/2026.emnlp-main.2230.pdf