I'm Junjie 俊杰.
CS + Maths @ UC Berkeley
My research centers on reinforcement learning, training language model agents, continual learning, and LLM evaluation.
More broadly, I am interested in language models and machine learning systems, and I am currently deepening my understanding of efficient inference.
Outside of research, I am drawn to investing and the venture capital world, and I am an avid reader. I also enjoy staying active through swimming, long-distance running, and racket sports like tennis, squash, and pickleball.
Currently
I am looking for roles in post-training research, machine learning engineering (MLE), and software engineering (SWE).
Research
RL for language models and agents; advised by Raluca Ada Popa & Ion Stoica.
I am forever thankful for the mentoring from Sijun Tan, Tianhao Wu, and Sida Li.
Building infrastructure for Agents’ Last Exam (ALE) to evaluate how well AI agents handle everyday tasks across apps and devices. Collaborating with Dawn Song’s group and the SGLang team.
NLP Group; advised by Dan Jurafsky and mentored by Chen Shani, exploring whether post-training can steer language models toward concept-preserving reasoning.
Contributed to the Vulci project with Maurizio Forte, doing geophysical surveys and computer graphics; mentored by Nevio Danelon and Antonio Lopiano.
Internships
Developing Go backend services, microservices, and infrastructure for an agentic LLM evaluation platform, supporting reliable asynchronous evaluation workflows, automated failure recovery, and model proxy monitoring.
Built an evaluation harness for math reasoning that uses an automated Lean prover to auto-formalize natural-language math into Lean and machine-check the resulting proofs, enabling scalable, rigorous grading of model outputs.
First-authored “Towards Expert Financial QA via Self-Improving RAG” (AFA Workshop @ ICLR 2026).
Helped take a product from early prototypes through A/B testing and launch at Xiaomi, contributing full-stack development and text and speech retrieval systems. Reported directly to Vice President Qu Heng.
Supported deal sourcing and due diligence for consumer-sector investments, preparing research reports and tracking investment memos. Contributed to early-round investment work, primarily involving Chi Forest and Qiandama. Cowin was an early investor in Pop Mart, Chi Forest, Tea’stone, and Qiandama. Cowin is a private equity and venture capital firm founded in 2000, with approximately US$5.2 billion in AUM.
Honors
Dean’s List. In-class rankings: 1st in CS 168, 2nd in EECS 126, and 4th in EECS 127.