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Main Authors: Fan, Chenghao, Heng, Wen, Li, Bo, Liu, Sichen, Song, Yuxuan, Su, Jing, Qu, Xiaoye, Shen, Kai, Wei, Wei
Format: Preprint
Published: 2026
Subjects:
Online Access:https://arxiv.org/abs/2601.15892
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author Fan, Chenghao
Heng, Wen
Li, Bo
Liu, Sichen
Song, Yuxuan
Su, Jing
Qu, Xiaoye
Shen, Kai
Wei, Wei
author_facet Fan, Chenghao
Heng, Wen
Li, Bo
Liu, Sichen
Song, Yuxuan
Su, Jing
Qu, Xiaoye
Shen, Kai
Wei, Wei
contents Diffusion-based language models (DLLMs) offer non-sequential, block-wise generation and richer data reuse compared to autoregressive (AR) models, but existing code DLLMs still lag behind strong AR baselines under comparable budgets. We revisit this setting in a controlled study and introduce Stable-DiffCoder, a block diffusion code model that reuses the Seed-Coder architecture, data, and training pipeline. To enable efficient knowledge learning and stable training, we incorporate a block diffusion continual pretraining (CPT) stage enhanced by a tailored warmup and block-wise clipped noise schedule. Under the same data and architecture, Stable-DiffCoder overall outperforms its AR counterpart on a broad suite of code benchmarks. Moreover, relying only on the CPT and supervised fine-tuning stages, Stable-DiffCoder achieves stronger performance than a wide range of \~8B ARs and DLLMs, demonstrating that diffusion-based training can improve code modeling quality beyond AR training alone. Moreover, diffusion-based any-order modeling improves structured code modeling for editing and reasoning, and through data augmentation, benefits low-resource coding languages.
format Preprint
id arxiv_https___arxiv_org_abs_2601_15892
institution arXiv
publishDate 2026
record_format arxiv
spellingShingle Stable-DiffCoder: Pushing the Frontier of Code Diffusion Large Language Model
Fan, Chenghao
Heng, Wen
Li, Bo
Liu, Sichen
Song, Yuxuan
Su, Jing
Qu, Xiaoye
Shen, Kai
Wei, Wei
Computation and Language
Diffusion-based language models (DLLMs) offer non-sequential, block-wise generation and richer data reuse compared to autoregressive (AR) models, but existing code DLLMs still lag behind strong AR baselines under comparable budgets. We revisit this setting in a controlled study and introduce Stable-DiffCoder, a block diffusion code model that reuses the Seed-Coder architecture, data, and training pipeline. To enable efficient knowledge learning and stable training, we incorporate a block diffusion continual pretraining (CPT) stage enhanced by a tailored warmup and block-wise clipped noise schedule. Under the same data and architecture, Stable-DiffCoder overall outperforms its AR counterpart on a broad suite of code benchmarks. Moreover, relying only on the CPT and supervised fine-tuning stages, Stable-DiffCoder achieves stronger performance than a wide range of \~8B ARs and DLLMs, demonstrating that diffusion-based training can improve code modeling quality beyond AR training alone. Moreover, diffusion-based any-order modeling improves structured code modeling for editing and reasoning, and through data augmentation, benefits low-resource coding languages.
title Stable-DiffCoder: Pushing the Frontier of Code Diffusion Large Language Model
topic Computation and Language
url https://arxiv.org/abs/2601.15892