Forward-Free Diffusion Language Models with BPTT-Free Looped Refinement
Abstract
Diffusion language models conventionally depend on a hand-designed forward corruption process, which constrains what the model can learn to undo. We introduce FReDA, a diffusion-based language model that eliminates the prescribed forward process entirely. Instead, language modeling is framed as recursive distribution refinement, in which model-generated drafts serve as implicit intermediate states — and training avoids backpropagation through time across the refinement loop. Text is produced by iterative refinement, either through self-refinement or best-of-N selection among parallel candidates. At sub-8B scale, FReDA-4B achieves up to 15% gains on reasoning and coding tasks over larger diffusion models while delivering 1.5-1.8x inference speedups over diffusion baselines.
Materials
BibTeX
@misc{sun2026forwardfreediffusionlanguagemodels,
title={Forward-Free Diffusion Language Models},
author={Haotian Sun and Rushi Qiang and Yuqian Zheng and Bo Dai},
year={2026},
eprint={2606.08357},
archivePrefix={arXiv},
primaryClass={cs.CL},
url={https://arxiv.org/abs/2606.08357},
}