I lead research, product, and engineering teams building agents for long-horizon, real-world work, and the environments, experience, and self-improvement that make them better over time. We carry that research into products used by millions across the Gemini ecosystem, and into internal agents powering mission-critical work at Google.
Research in Production
Agents that Engineer
Brought our agents into production on Google’s most critical infra buildout, hill-climbing on Physical-Engineering’s Last Exam, our open benchmark where every frontier model still scores below 50%.
Launched MemoryBank, long-term memory for agents, one of the most used GenAI APIs on Google Cloud, powering Gemini Enterprise and BigQuery, highlighted at Google Cloud NEXT 2026.
Today's agents are strong at short tasks but weak at getting better over time and at real-world work. Our teams focus on closing that gap:
Environments are the bottleneck.
Agents can only learn from the worlds we give them, and most are static. EnvHarness turns static data and tools into interactive environments.
Experience should transfer.ReasoningBank distills reusable insights from successes and failures; SkillOS curates the skills worth carrying to the next task.
Agents should improve themselves, safely.Harness2 lets agents build their own harnesses; VeriHarness and RRSI keep that improvement verifiable, stable, and under human oversight.
The physical world is the next test.
Humanity’s Last Exam tests knowledge; Agents’ Last Exam tests digital work. Physical-Engineering’s Last Exam tests the work behind the skyscrapers, power grids, and chip fabs we rely on, judged by what a licensed engineer would sign off on.
Earlier Work
I've worked on deep learning since my PhD at UC San Diego, advised by Zhuowen Tu with mentorship from Simon Osindero, where my work on Deeply-Supervised Nets later received the AISTATS 2025 Test-of-Time Award. I then joined the AI Research Group at Magic Leap with Andrew Rabinovich, and later Apple, where I launched foundational features for ARKit (now powering Vision Pro) and published the group's first-ever research paper, at CVPR (featured by Apple ML Journal).
Feb 2027StanfordGuest lecture on self-improving agents and AI for physical engineering.
Apr 2027ICLR 2027Invited speaker at three workshops on long-horizon agents, self-improvement, and evaluation.
Selected Papers
PLE: Physical-Engineering's Last Exam
Tests agents on real physical engineering work. Every frontier model scores below 50%.Rujun Han, Yufan Zhuang, Arijit Ray, Han Yu, Zoey CuiZhu, George Lee, Yifei Ming, Binz Roy, Varun Sakalkar, Vishy Tirumalashetty, Burak Gokturk, Tomas Pfister, Chen-Yu LeearXiv 2026·Paper·Project Page·Code·Dataset·Competition
RRSI: Regularized Recursive Self-Improvement of Agent Harnesses
Agents that improve their own harnesses, with regularization that keeps the loop stable.Peng Xia, Rujun Han, Zifeng Wang, Yanfei Chen, Yufan Zhang, Yoonho Lee, Chengsong Huang, Han Yu, Zhongying CuiZhu, Yifei Ming, Huaxiu Yao, Burak Gokturk, Tomas Pfister, Chen-Yu LeearXiv 2026·Paper·Project Page·Code
EnvHarness: Awakening Static Worlds for Agent Learning
Turns static data and tools into interactive training environments for agents.Chengsong Huang, Zifeng Wang, Rujun Han, Jun Yan, Yanfei Chen, Zoey CuiZhu, Ke Jiang, Peng Xia, Han Yu, Yufan Zhuang, Yifei Ming, Jiaqi Pan, Bhavana Dalvi Mishra, Jiaxin Huang, Burak Gokturk, Tomas Pfister, Chen-Yu LeearXiv 2026·Paper·Project Page·Code
SkillOS: Learning Skill Curation for Self-Evolving Agents
Learns how a self-evolving agent should curate its library of reusable skills.Siru Ouyang, Jun Yan, Yanfei Chen, Rujun Han, Zifeng Wang, Bhavana Dalvi Mishra, Rui Meng, Chun-Liang Li, Yizhu Jiao, Kaiwen Zha, Maohao Shen, Vishy Tirumalashetty, George Lee, Jiawei Han, Tomas Pfister, Chen-Yu LeeNeurIPS 2026·Paper
ReasoningBank: Scaling Agent Self-Evolving with Reasoning Memory
Distills reusable insights from an agent's successes and failures.Siru Ouyang, Jun Yan, I-Hung Hsu, Yanfei Chen, Ke Jiang, Zifeng Wang, Rujun Han, Long T. Le, Samira Daruki, Xiangru Tang, Vishy Tirumalashetty, George Lee, Mahsan Rofouei, Hangfei Lin, Jiawei Han, Chen-Yu Lee, Tomas PfisterICLR 2026·Paper·Code·Google AI Blog—Featured in VentureBeat and Andrej Karpathy's interview
Supervised Reinforcement Learning: From Expert Trajectories to Step-wise Reasoning
Turns expert trajectories into step-wise rewards for learning multi-step reasoning.Yihe Deng, I-Hung Hsu, Jun Yan, Zifeng Wang, Rujun Han, Gufeng Zhang, Yanfei Chen, Wei Wang, Tomas Pfister, Chen-Yu LeeICLR 2026·Paper—Featured in VentureBeat
Scaling agents under explicit tool and compute budgets.Tengxiao Liu, Zifeng Wang, Jin Miao, I-Hung Hsu, Jun Yan, Jiefeng Chen, Rujun Han, Fangyuan Xu, Yanfei Chen, Ke Jiang, Samira Daruki, Yi Liang, William Yang Wang, Tomas Pfister, Chen-Yu LeeCOLM 2026·Paper·Code—Featured in VentureBeat
Deep Researcher with Test-Time Diffusion
The research agent behind Gemini Enterprise Deep Research and Gemini Deep Research Max.Rujun Han, Yanfei Chen, Zoey CuiZhu, Lesly Miculicich, Guan Sun, Yuanjun Bi, Weiming Wen, Hui Wan, Chunfeng Wen, Solène Maître, George Lee, Vishy Tirumalashetty, Emily Xue, Zizhao Zhang, Salem Haykal, Burak Gokturk, Tomas Pfister, Chen-Yu LeearXiv 2025·Paper·Google AI Blog—Featured in VentureBeat
Speculative Knowledge Distillation: Bridging the Teacher-Student Gap Through Interleaved Sampling
The student proposes tokens and the teacher replaces poor ones, keeping distillation on-policy and stable.Wenda Xu, Rujun Han, Zifeng Wang, Long T. Le, Dhruv Madeka, Lei Li, William Yang Wang, Rishabh Agarwal, Chen-Yu Lee, Tomas PfisterICLR 2025·Paper·Code
Distilling Step-by-Step! Outperforming Larger Language Models with Less Training Data and Smaller Model Sizes
Small models trained on LLM rationales outperform much larger LLMs using less data.Cheng-Yu Hsieh, Chun-Liang Li, Chih-Kuan Yeh, Hootan Nakhost, Yasuhisa Fujii, Alexander Ratner, Ranjay Krishna, Chen-Yu Lee, Tomas PfisterACL 2023·Paper (Findings) ·Code·Google AI Blog—Google ACL 2023 Spotlight