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arXiv · 2509.25193

Devstral: Fine-tuning Language Models for Coding Agent Applications

Abhinav Rastogi·Adam Yang·Albert Q. Jiang·Alexander H. Liu·Alexandre Sablayrolles·Amélie Héliou·Amélie Martin·Anmol Agarwal·Andy Ehrenberg·Andy Lo·Antoine Roux·Arthur Darcet·Arthur Mensch·Baptiste Bout·Baptiste Rozière·Baudouin De Monicault·Chris Bamford·Christian Wallenwein·Christophe Renaudin·Clémence Lanfranchi·Clément Denoix·Corentin Barreau·Darius Dabert Devon Mizelle·Diego de las Casas·Elliot Chane-Sane·Emilien Fugier·Emma Bou Hanna·Gabrielle Berrada·Gauthier Delerce·Gauthier Guinet·Georgii Novikov·Graham Neubig·Guillaume Lample·Guillaume Martin·Himanshu Jaju·Jan Ludziejewski·Jason Rute·Jean-Malo Delignon·JeanHadrien Chabran·Joachim Studnia·Joep Barmentlo·Jonas Amar·Josselin Somerville Roberts·Julien Denize·Karan Saxena·Karmesh Yadav·Kartik Khandelwal·Khyathi Raghavi Chandu·Kush Jain·Lélio Renard Lavaud·Léonard Blier·Lingxiao Zhao·Louis Martin·Lucile Saulnier·Luyu Gao·Marie Pellat·Mathilde Guillaumin·Mathis Felardos·Matthieu Dinot·Maxime Darrin·Maximilian Augustin·Mickaël Seznec·Neha Gupta·Nikhil Raghuraman·Olivier Duchenne·Patricia Wang·Patrick von Platen·Patryk Saffer·Paul Jacob·Paul Wambergue·Paula Kurylowicz·Philomène Chagniot·Pierre Stock·Pravesh Agrawal·Rémi Delacourt·Roman Soletskyi·Romain Sauvestre·Sagar Vaze·Sanchit Gandhi·Sandeep Subramanian·Shashwat Dalal·Siddharth Gandhi·Soham Ghosh·Srijan Mishra·Sumukh Aithal·Szymon Antoniak·Teven Le Scao·Thibaut Lavril·Thibault Schueller·Thomas Foubert·Thomas Robert·Thomas Wang·Timothée Lacroix·Tom Bewley·Valeriia Nemychnikova·Victor Paltz·Virgile Richard·Wen-Ding Li·William Marshall·Xingyao Wang
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Abstract

We introduce Devstral-Small, a lightweight open source model for code agents with the best performance among models below 100B size. In this technical report, we give an overview of how we design and develop a model and craft specializations in agentic software development. The resulting model, Devstral-Small is a small 24B model, fast and easy to serve. Despite its size, Devstral-Small still attains competitive performance compared to models more than an order of magnitude larger.

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Abhinav Rastogi, Adam Yang, Albert Q. Jiang, Alexander H. Liu, Alexandre Sablayrolles, Amélie Héliou, Amélie Martin, Anmol Agarwal, Andy Ehrenberg, Andy Lo, Antoine Roux, Arthur Darcet, Arthur Mensch, Baptiste Bout, Baptiste Rozière, Baudouin De Monicault, Chris Bamford, Christian Wallenwein, Christophe Renaudin, Clémence Lanfranchi, Clément Denoix, Corentin Barreau, Darius Dabert Devon Mizelle, Diego de las Casas, Elliot Chane-Sane, Emilien Fugier, Emma Bou Hanna, Gabrielle Berrada, Gauthier Delerce, Gauthier Guinet, Georgii Novikov, Graham Neubig, Guillaume Lample, Guillaume Martin, Himanshu Jaju, Jan Ludziejewski, Jason Rute, Jean-Malo Delignon, JeanHadrien Chabran, Joachim Studnia, Joep Barmentlo, Jonas Amar, Josselin Somerville Roberts, Julien Denize, Karan Saxena, Karmesh Yadav, Kartik Khandelwal, Khyathi Raghavi Chandu, Kush Jain, Lélio Renard Lavaud, Léonard Blier, Lingxiao Zhao, Louis Martin, Lucile Saulnier, Luyu Gao, Marie Pellat, Mathilde Guillaumin, Mathis Felardos, Matthieu Dinot, Maxime Darrin, Maximilian Augustin, Mickaël Seznec, Neha Gupta, Nikhil Raghuraman, Olivier Duchenne, Patricia Wang, Patrick von Platen, Patryk Saffer, Paul Jacob, Paul Wambergue, Paula Kurylowicz, Philomène Chagniot, Pierre Stock, Pravesh Agrawal, Rémi Delacourt, Roman Soletskyi, Romain Sauvestre, Sagar Vaze, Sanchit Gandhi, Sandeep Subramanian, Shashwat Dalal, Siddharth Gandhi, Soham Ghosh, Srijan Mishra, Sumukh Aithal, Szymon Antoniak, Teven Le Scao, Thibaut Lavril, Thibault Schueller, Thomas Foubert, Thomas Robert, Thomas Wang, Timothée Lacroix, Tom Bewley, Valeriia Nemychnikova, Victor Paltz, Virgile Richard, Wen-Ding Li, William Marshall, Xingyao Wang. 2025-08-08. Devstral: Fine-tuning Language Models for Coding Agent Applications. https://arxiv.org/abs/2509.25193

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