Multi-Block Diffusion Language Models

Yijie Jin, Jiajun Xu, Yuxuan Liu, Chenkai Xu, Jiajun Li, Kai Yu, Pengfei Liu, Zhijie Deng


Abstract
Block Diffusion Language Models (BD-LMs) support KV caching and flexible-length generation, but their native Single-Block Diffusion (SingleBD) inference leaves inter-block parallelism unused. We study Multi-Block Diffusion (MultiBD), where a running-set of consecutive blocks is refined concurrently. Existing teacher-forced BD-LMs observe only one noisy block conditioned on a clean prefix, while diffusion forcing exposes a long noisy suffix whose state distribution still differs from practical MultiBD inference. We bridge this gap with Multi-Block Diffusion Language Models (MBD-LMs), obtained by post-training BD-LMs using Multi-block Teacher Forcing (MultiTF). MultiTF trains on bounded noise-groups conditioned on clean prefixes, with heterogeneous slot-wise noise patterns that better match inference. An optimized Block Buffer further preserves prefix-cache reuse and static input shapes, translating inter-block parallelism into wall-clock acceleration. On math and code benchmarks, MBD-LLaDA2-Mini increases average Tokens Per Forward pass (TPF) from 3.47 to 6.19 while maintaining comparable accuracy (80.0% versus 81.0%). Combined with DMax, it reaches 9.34 TPF with a 1.02-point accuracy drop. Project Page: https://sjtu-deng-lab.github.io/mbd-lms
Anthology ID:
2026.emnlp-main.1971
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:
44855–44875
Language:
URL:
https://aclanthology.org/2026.emnlp-main.1971/
DOI:
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Cite (ACL):
Yijie Jin, Jiajun Xu, Yuxuan Liu, Chenkai Xu, Jiajun Li, Kai Yu, Pengfei Liu, and Zhijie Deng. 2026. Multi-Block Diffusion Language Models. In Proceedings of the 2026 Conference on Empirical Methods in Natural Language Processing, pages 44855–44875, Budapest, Hungary. Association for Computational Linguistics.
Cite (Informal):
Multi-Block Diffusion Language Models (Jin et al., EMNLP 2026)
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PDF:
https://aclanthology.org/2026.emnlp-main.1971.pdf