CoT-Edit: Reinforcement Learning of Chain-of-Thought Reasoning for Code Edit Suggestion

Code edit suggestion, which encompasses modifying, refactoring, and maintaining existing code, represents the most frequent software development activity and has become a focal point for AI-powered tools. Traditional methods translate explicit natural language instructions into code edits, while pattern-based approaches learn from users' historical editing patterns to provide style-consistent and more accurate suggestions. However, these patternbased methods still face two critical challenges: (1) difficulty handling edits that demand deep contextual reasoning, and (2) lack of interpretability in editing decisions. To tackle this, we propose CoT-Edit, a reinforcement learning framework that guides LLMs to discover chainof-thought (CoT) reasoning paths for code editing without requiring human-annotated CoT data. Specifically, we design multi-step reasoning framework that enable: (1) analysisguided code editing, and (2) seamless switching between CoT and non-CoT inference modes. Building on this, we introduce Edit-Aware Reward Modeling (EARM), a fine-grained diffbased reward approach for effective learning. Furthermore, we discover a LoRA merging strategy that enhances model generalization. Evaluations on an industrial dataset show that our approach achieves 60.2% edit accuracy, outperforming all strong baselines. Online A/B tests further confirm its effectiveness in production. Code is available at https://github. com/202230483077yyh/CoT-Edit .