Leandro von Werra is Head of Research at Hugging Face, where he leads a team advancing open-source AI and large language models. He built the TRL library for transformer fine-tuning (17,000+ GitHub stars, 1M+ monthly downloads) and lead the BigCode project, creating the StarCoder family of open code LLMs and large-scale code datasets. His work includes the SmolLM family of efficient small models, the FineWeb high-quality text datasets, and co-authoring the O'Reilly book "Natural Language Processing with Transformers."