Jiacheng Xu

Biography

I am a PhD student at the College of Computing and Data Science (CCDS), Nanyang Technological University, and an AI researcher at Skywork AI. My research focuses on reinforcement learning and verification for code language models, particularly executable feedback, test generation, and inference-time selection.

Research Interests

• Reinforcement Learning
• Code Language Models
• Test Generation and Executable Verification
• Inference-Time Scaling and Selection

Selected Publications

• Negative-Only Policy Optimization for One-Sided Verifiable Rewards

  Jiacheng Xu, Shuo He, Fuxiang Zhang, Chaojie Wang, and Bo An.

  NeurIPS 2026. (Spotlight, ~0.95% of submissions)

• Backtracking with Linear-in-Depth Search-Space Growth: Width-Limited Tree Search for Large Language Models

  Jiacheng Xu, Fuxiang Zhang, Chaojie Wang, and Bo An.

  NeurIPS 2026. (Spotlight, ~0.95% of submissions)

• Entropy-Regularized Rank-Masked Policy Optimization for Test-Time Reinforcement Learning in Code Generation

  Jiacheng Xu, Feng Chen, Xiuneng Xu, and Bo An.

  EMNLP 2026. (Oral, ~2.6% of submissions) [Project] [Paper] [PDF]

• Two-Stage Reinforcement Learning for Sound and Adversarial Test Generation in Code LLMs

  Jiacheng Xu, Wentao Zhang, Zhiyi Lyu, Fuxiang Zhang, Chaojie Wang, Yang Liu, and Bo An.

  Findings of EMNLP 2026. [Project] [Paper] [Code] [Models] [PDF]

• Incentivizing LLMs to Self-Verify Their Answers

  Fuxiang Zhang, Jiacheng Xu, Chaojie Wang, Ce Cui, Yang Liu, and Bo An.

  NeurIPS 2025. [Paper] [Code] [PDF]

• Focus-Then-Decide: Segmentation-Assisted Reinforcement Learning

  Chao Chen^*, Jiacheng Xu^*, Weijian Liao, Hao Ding, Zongzhang Zhang, Yang Yu, and Rui Zhao.

  AAAI 2024. [Project] [Paper] [Code] [PDF]

• Internal Logical Induction for Pixel-Symbolic Reinforcement Learning

  Jiacheng Xu, Chao Chen, Fuxiang Zhang, Lei Yuan, Zongzhang Zhang, and Yang Yu.

  KDD 2023. [Project] [Paper] [Code] [PDF]

• Multi-Agent Dynamic Algorithm Configuration

  Ke Xue^*, Jiacheng Xu^*, Lei Yuan, Miqing Li, Chao Qian, Zongzhang Zhang, and Yang Yu.

  NeurIPS 2022. (Spotlight, ~3.4% of submissions) [Paper] [Code] [PDF]

^* Equal Contribution

Awards

• National Scholarship, 2023

Correspondence

Email: jiacheng005@e.ntu.edu.sg