What Gets Unmasked First? Trajectory Analysis of Diffusion Models for Graph-to-Text Generation

Qing Wang, Jacob Devasier, Chengkai Li


Abstract
We present the first systematic study of masked diffusion language models (MDLMs) for graph-to-text generation. We analyze MDLM generation trajectories—the order in which tokens are unmasked during iterative decoding—and find that, unlike autoregressive LLMs which generate text linearly, MDLMs naturally prioritize entities first, followed by relational and function words, with structural tokens resolved last. We further identify a previously undocumented failure mode of supervised fine-tuning: SFT disrupts this strategy by prematurely anchoring structural sentence-ending tokens early in the decoding trajectory, effectively fixing the output length which can lead to omitted or hallucinated information. To address this, we propose 𝜆-scaled structural decoding, a training-free inference-time modification that downweights structural token confidence and recovers +9.4 BLEU-4. Finally, we introduce Graph-LLaDA, which integrates a Graph Transformer encoder into LLaDA’s decoding process to explicitly incorporate relational graph structure. Cross-dataset evaluation on LAGRANGE reveals that previous baselines overfit to dataset-specific patterns, while LLM- and MDLM-based approaches generalize significantly better. All code and datasets used in our experiments are publicly available at https://github.com/idirlab/Graph_LLaDA.
Anthology ID:
2026.findings-emnlp.1456
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
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SIGDAT
Publisher:
Association for Computational Linguistics
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Pages:
30992–31012
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URL:
https://aclanthology.org/2026.findings-emnlp.1456/
DOI:
Bibkey:
Cite (ACL):
Qing Wang, Jacob Devasier, and Chengkai Li. 2026. What Gets Unmasked First? Trajectory Analysis of Diffusion Models for Graph-to-Text Generation. In Findings of the Association for Computational Linguistics: EMNLP 2026, pages 30992–31012, Budapest, Hungary. Association for Computational Linguistics.
Cite (Informal):
What Gets Unmasked First? Trajectory Analysis of Diffusion Models for Graph-to-Text Generation (Wang et al., Findings 2026)
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https://aclanthology.org/2026.findings-emnlp.1456.pdf