Idiomatic Blind Spots in Discrete Diffusion Models

Joshua Chaz Rivera, Vincent Gripon, Bastien Pasdeloup


Abstract
Discrete diffusion language models have emerged as a compelling alternative to autoregressive approaches, offering a range of structural advantages. This is due to their bidirectional attention allowing a global semantic view across intermediate denoising steps that enables flexible, order-agnostic generation. Despite this promise, they have received considerably less attention in ongoing research, and existing work has focused narrowly on mathematics and formal reasoning tasks. Their language comprehension capabilities, particularly for figurative language, remain entirely unevaluated, leaving open fundamental questions about how these models handle complex idiomatic structures, especially for languages other than English. We find that diffusion models do possess many strong idiomatic processing abilities, demonstrated through competitive token recovery in cloze tests and strong semantic ability from multiple-choice accuracy. However, this advantage fails to surface during inference as confidence-based demasking appears poorly suited for idioms, as early committed tokens override internal representations and discourage certain types of multi-token structures from generation, limiting their linguistic abilities.
Anthology ID:
2026.uncertainlp-main.7
Volume:
The Proceedings of the Third Workshop on Uncertainty-Aware NLP
Month:
October
Year:
2026
Address:
Budapest, Hungary
Editors:
Wilker Aziz, Jonathan Berant, Bryan Eikema, Evgenia Ilia, Marie-Catherine de Marneffe, Barbara Plank, Artem Shelmanov, Swabha Swayamdipta, Jörg Tiedemann, Artem Vazhentsev, Raúl Vázquez, Chrysoula Zerva
Venues:
UncertaiNLP | WS
SIG:
Publisher:
Association for Computational Linguistics
Note:
Pages:
81–93
Language:
URL:
https://aclanthology.org/2026.uncertainlp-main.7/
DOI:
Bibkey:
Cite (ACL):
Joshua Chaz Rivera, Vincent Gripon, and Bastien Pasdeloup. 2026. Idiomatic Blind Spots in Discrete Diffusion Models. In The Proceedings of the Third Workshop on Uncertainty-Aware NLP, pages 81–93, Budapest, Hungary. Association for Computational Linguistics.
Cite (Informal):
Idiomatic Blind Spots in Discrete Diffusion Models (Chaz Rivera et al., UncertaiNLP 2026)
Copy Citation:
PDF:
https://aclanthology.org/2026.uncertainlp-main.7.pdf