About me

I am a senior research engineer with Ant Group, where I currently work on a variety of LLM alignment and reinforcement learning.

Before this, I worked in IBM Research AI and collaborated with Pin-Yu Chen, Payel Das, Songtao Lu, Xiaodong Cui and many other talented researchers. My research at IBM focused on LLM alignment and RL. Meanwhile, I did my Ph.D. under the supervision of Dr. Tianyi Chen. I was fortunate to join Dr. Tianyi Chen’s group as the first Ph.D. student. My Ph.D. research focused on optimization and reinforcement learning.

News and highlights

• [Jan. 2026] Our paper on entropy regularization of LLM-RL is accepted in ICLR 2026.
  • On Entropy Control in LLM-RL Algorithms
• [Mar. 2025] I am excited to join Ant Group via its research talent program Ant Star.
• [Feb. 2025] The extended study of our ICML 2024 paper is accepted in JMLR.
  • ArXiv: Principled Penalty-based Methods for Bilevel Reinforcement Learning and RLHF
• [Jan. 2025] Our paper is accepted in ICLR 2025:
  • SEAL: Safety-enhanced Aligned LLM Fine-tuning via Bilevel Data Selection
• [Dec. 2024] An extended study of our ICML 2023 paper has been accepted in Mathematical Programming.
  • On Penalty-based Bilevel Gradient Descent Method
• [Oct. 2024] New paper on improved LLM alignment framwork:
  • Mitigating Forgetting in LLM Supervised Fine-Tuning and Preference Learning

Selected works

• On Entropy Control in LLM-RL Algorithms
  Han Shen
  ICLR 2026. [paper]

• SEAL: Safety-enhanced Aligned LLM Fine-tuning via Bilevel Data Selection
  Han Shen, Pin-Yu Chen, Payel Das, Tianyi Chen
  ICLR 2025. [paper]

• Principled Penalty-based Methods for Bilevel Reinforcement Learning and RLHF
  Han Shen, Zhuoran Yang, Tianyi Chen
  ICML 2024, extended work in JMLR [paper]

• Mitigating Gradient Bias in Multi-objective Learning: A Provably Convergent Approach
  Heshan D. Fernando, Han Shen, Miao Liu, Subhajit Chaudhury, Keerthiram Murugesan, Tianyi Chen
  ICLR 2023 Oral. [paper]

• On Penalty-based Bilevel Gradient Descent Method
  Han Shen, Quan Xiao, Tianyi Chen
  ICML 2023, extended work in Mathematical Programming. [paper]

• A Single-timescale Analysis for Stochastic Approximation with Multiple Coupled Sequences
  Han Shen, Tianyi Chen
  NeurIPS 2022 Oral. [paper]

Industry experiences

Ant Group. (CN) Present

• Senior research engineer, joined via Ant Star talent program.

IBM Research AI. (US) 05.2024 - 08.2024

• Research intern, mentored by Dr. Pin-Yu Chen and Dr. Payel Das.

IBM Research AI. (US) 05.2021 - 08.2021

• Research intern, mentored by Dr. Songtao Lu and Dr. Xiaodong Cui.

Services

Reviewer for NeurIPS, ICML, ICLR, AISTATS, AAAI, IEEE Transactions on Signal Processing, etc.