creators

Sasha Rush — ML researcher at Cursor

Alexander "Sasha" Rush is an ML researcher at Cursor in New York and a former Harvard and Cornell professor, working on post-training for coding models.

Alexander "Sasha" Rush describes himself as an ML researcher at Cursor in New York who studies the post-training of AI systems for coding and long-horizon reasoning. From 2016 he was a professor at Harvard and then Cornell, where his group's work was recognised with an NSF CAREER Award and a Sloan Fellowship; from 2019 to 2024 he also worked as a researcher at Hugging Face on early open-source LLM projects. He announced his move to Cursor in March 2025, and is one of the 54 Cursor Research authors of the Composer 2 technical report, posted to arXiv in March 2026, which describes continued pretraining followed by large-scale reinforcement learning for an agentic coding model. In 2024 he helped start the Conference on Language Modeling. He is known for open teaching projects including the annotated Transformer, Torch-Struct and GPU-Puzzles, and posts on X as @srush_nlp and on a YouTube channel of the same name.

Specialization

LLM post-training, reinforcement learning for code, natural language processing, open-source ML teaching

Country

United States