Plan, Verify and Fill: A Structured Parallel Decoding Approach for Diffusion Language Models

Miao Li, Hanyang Jiang, Sikai Cheng, Hengyu Fu, Yuhang Cai, Baihe Huang, Zhongzhu Chen, Tinghan Ye, Xuanzhou Chen, Pascal Van Hentenryck


Abstract
Diffusion Language Models (DLMs) enable parallel text generation by denoising multiple masked positions in a single pass, but confidence-threshold decoding often commits only the safest predictions, leaving informative uncertainty underused. We propose Plan-Verify-Fill (PVF), a training-free draft-and-verification decoding strategy that preserves the high-confidence decoding backbone while selectively testing lower-confidence candidates with high expected verified utility. PVF uses a calibrated planning-token vocabulary to allocate its limited verification budget, accepts proposed drafts only when they remain consistent with the backbone trajectory, and otherwise defaults to conservative confidence-gated unmasking. Across mathematical reasoning, knowledge, and code-generation benchmarks on LLaDA-8B-Instruct and Dream-7B-Instruct, PVF maintains comparable accuracy while delivering up to 2.3× higher throughput than baseline methods.
Anthology ID:
2026.findings-emnlp.1119
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
SIG:
SIGDAT
Publisher:
Association for Computational Linguistics
Note:
Pages:
23694–23717
Language:
URL:
https://aclanthology.org/2026.findings-emnlp.1119/
DOI:
10.18653/2026.findings-emnlp.1119
Bibkey:
Cite (ACL):
Miao Li, Hanyang Jiang, Sikai Cheng, Hengyu Fu, Yuhang Cai, Baihe Huang, Zhongzhu Chen, Tinghan Ye, Xuanzhou Chen, and Pascal Van Hentenryck. 2026. Plan, Verify and Fill: A Structured Parallel Decoding Approach for Diffusion Language Models. In Findings of the Association for Computational Linguistics: EMNLP 2026, pages 23694–23717, Budapest, Hungary. Association for Computational Linguistics.
Cite (Informal):
Plan, Verify and Fill: A Structured Parallel Decoding Approach for Diffusion Language Models (Li et al., Findings 2026)
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PDF:
https://aclanthology.org/2026.findings-emnlp.1119.pdf