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 pattern-based 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 chain-of-thought (CoT) reasoning paths for code editing without requiring human-annotated CoT data. Specifically, we design multi-step reasoning framework that enable: (1) analysis-guided 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 diff-based 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.

Unsupervised constrained text generation aims to generate text under a given set of constraints without any supervised data. Current state-of-the-art methods stochastically sample edit positions and actions, which may cause unnecessary search steps. In this paper, we propose PMCTG to improve effectiveness by searching for the best edit position and action in each step. Specifically, PMCTG extends perturbed masking technique to effectively search for the most incongruent token to edit. Then it introduces four multi-aspect scoring functions to select edit action to further reduce search difficulty. Since PMCTG does not require supervised data, it could be applied to different generation tasks. We show that under the unsupervised setting, PMCTG achieves new state-of-the-art results in two representative tasks, namely keywords- to-sentence generation and paraphrasing.