Can Unified Generation and Understanding Models Maintain Semantic Equivalence Across Different Output Modalities?

Fuente: arXiv
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Autori principali: Jiang, Hongbo, Li, Jie, Shen, Yunhang, Dai, Pingyang, Sun, Xing, Cao, Haoyu, Cao, Liujuan
Natura: Preprint
Pubblicazione: 2026
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author Jiang, Hongbo
Li, Jie
Shen, Yunhang
Dai, Pingyang
Sun, Xing
Cao, Haoyu
Cao, Liujuan
author_facet Jiang, Hongbo
Li, Jie
Shen, Yunhang
Dai, Pingyang
Sun, Xing
Cao, Haoyu
Cao, Liujuan
contents Unified Multimodal Large Language Models (U-MLLMs) integrate understanding and generation within a single architecture. However, existing evaluations typically assess these capabilities separately, overlooking semantic equivalence, i.e., the ability to manifest consistent reasoning results regardless of the output modality. In this work, we investigate whether current U-MLLMs satisfy this premise. We observe that while models demonstrate robust textual reasoning, they fail to maintain semantic equivalence when required to render the same results in the image modality. To rigorously diagnose this discrepancy, we introduce VGUBench, a framework to decouple reasoning logic from generation fidelity. VGUBench comprises three diagnostic tasks: (1)Textual Generative Understanding, establishing a baseline for reasoning accuracy in textual response; (2)Visual Generative Understanding, evaluating the ability to generate visual responses that represent the correct answer; and (3)a Visual Rendering control task, which assesses the ability to directly render explicit visual descriptions into images without complex reasoning. Our evaluation reveals a significant disparity: despite strong performance in textual understanding and visual rendering, U-MLLMs exhibit a marked performance collapse when required to generate visual answers to questions. Furthermore, we find a negligible correlation between visual answering performance and basic rendering quality. These results suggest that the failure stems not from insufficient generation fidelity, but from a breakdown in cross-modal semantic alignment. We provide diagnostic insights to address this challenge in future Unified Generation and Understanding Models.
format Preprint
id arxiv_https___arxiv_org_abs_2602_23711
institution arXiv
publishDate 2026
record_format arxiv
spellingShingle Can Unified Generation and Understanding Models Maintain Semantic Equivalence Across Different Output Modalities?
Jiang, Hongbo
Li, Jie
Shen, Yunhang
Dai, Pingyang
Sun, Xing
Cao, Haoyu
Cao, Liujuan
Computer Vision and Pattern Recognition
Unified Multimodal Large Language Models (U-MLLMs) integrate understanding and generation within a single architecture. However, existing evaluations typically assess these capabilities separately, overlooking semantic equivalence, i.e., the ability to manifest consistent reasoning results regardless of the output modality. In this work, we investigate whether current U-MLLMs satisfy this premise. We observe that while models demonstrate robust textual reasoning, they fail to maintain semantic equivalence when required to render the same results in the image modality. To rigorously diagnose this discrepancy, we introduce VGUBench, a framework to decouple reasoning logic from generation fidelity. VGUBench comprises three diagnostic tasks: (1)Textual Generative Understanding, establishing a baseline for reasoning accuracy in textual response; (2)Visual Generative Understanding, evaluating the ability to generate visual responses that represent the correct answer; and (3)a Visual Rendering control task, which assesses the ability to directly render explicit visual descriptions into images without complex reasoning. Our evaluation reveals a significant disparity: despite strong performance in textual understanding and visual rendering, U-MLLMs exhibit a marked performance collapse when required to generate visual answers to questions. Furthermore, we find a negligible correlation between visual answering performance and basic rendering quality. These results suggest that the failure stems not from insufficient generation fidelity, but from a breakdown in cross-modal semantic alignment. We provide diagnostic insights to address this challenge in future Unified Generation and Understanding Models.
title Can Unified Generation and Understanding Models Maintain Semantic Equivalence Across Different Output Modalities?
topic Computer Vision and Pattern Recognition
url https://arxiv.org/abs/2602.23711