SpatialFlow-GRPO: Where Spatial Credit Drives Image Editing

Abstract

Recent online reinforcement learning has substantially improved image editing quality. However, existing Flow-GRPO-style methods usually rely on a single whole-image reward, which makes fine-grained editing optimization difficult. We observe that a key obstacle in image editing is this spatial uniformity assumption: a whole-image reward cannot distinguish how different spatial regions contribute to image quality. To address this issue, we propose **SpatialFlow-GRPO**, a training framework that makes spatial reward feedback more fine-grained. The framework converts region-aware rewards into semantic-region-level optimization signals and aligns region advantages with the corresponding latent positions during policy updates. We also train a region-aware reward model, **SFReward**, construct **SFReward-14K** with region-annotated editing samples, and introduce **MultiEditBench** to evaluate multi-region editing ability. On OmniGen2 and FLUX.2-klein-4B, SpatialFlow-GRPO outperforms Flow-GRPO on GEdit-Bench, ImgEdit-Bench, and MultiEditBench. The results show that SpatialFlow-GRPO can turn local feedback into more accurate update signals and improve editing quality.