Tencent Hunyuan's FewStepRL adapts RL fine-tuning to few-step diffusion models

Tencent-Hunyuan · hf · 2026-11-10

Tencent Hunyuan, with Westlake University, introduces FewStepRL, a systematic framework for RL post-training of few-step diffusion models. Existing RL objectives assume instantaneous velocity with many-step samplers, while few-step models model average velocity over intervals, making them a poor fit.

The paper reformulates RL objectives in three phases—x-space transformation, gradient decomposition, and anchor adaptation—yielding modular few-step variants of several methods. Findings: reward-gradient methods excel with differentiable rewards, while DiffusionNFT-style methods achieve high rewards in fewer iterations, cutting post-training cost.

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