Leandro von Werra
Machine learning at Hugging Face; first listed author of TRL and co-author of StarCoder2 and smolagents
- Machine learning engineer in the open-source team, Hugging Face12
Leandro von Werra works in machine learning at Hugging Face, according to von Werra's GitHub profile, and Hugging Face's LLM Course describes von Werra as a machine learning engineer in the company's open-source team. Von Werra is listed first among the authors of TRL, Hugging Face's Apache-2.0 library for post-training transformer models, and is a co-author of the StarCoder and StarCoder2 code model papers. Von Werra also appears in the citation for smolagents, Hugging Face's library for running agents in a few lines of code, and co-wrote the O'Reilly book Natural Language Processing with Transformers.123546
Work
TRL (Transformers Reinforcement Learning)Open-source code
Listed first among the authors in TRL's citation file, which dates the project to 2020. TRL is an Apache-2.0 toolkit for post-training transformer models with SFT, reward modeling, DPO, and GRPO.3
StarCoder2Published research
Co-author of "StarCoder 2 and The Stack v2: The Next Generation" (2024), and earlier of "StarCoder: may the source be with you!" (2023).45
smolagentsOpen-source code
Listed among the authors in the citation entry of the smolagents README (2025); the library runs agents in a few lines of code and is licensed under Apache 2.0.6
Natural Language Processing with Transformers (O'Reilly)Published research
Co-author of the O'Reilly book, according to the author biographies on Hugging Face's LLM Course page.2
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