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[OPEN WEIGHTS] Meet S5-nano, Maritaca's new open-weight model. Anyone — individuals, companies or universities — can download it, run it on their own infrastructure, and adapt it to their needs. S5-nano has 4 billion parameters and is built from Qwen3.5-4B, with continued pretraining and post-training carried out by our team. To see how it compares with other open-weight models, we evaluated 10 models, including Brazilian projects. S5-nano ranks first on average across native Portuguese benchmarks in both reasoning and non-reasoning modes. The evaluation covers law, medicine, exams and agentic tasks, among other areas. Made in Brazil by Maritaca, S5-nano gives companies, universities and government organizations a model they can run and adapt themselves, on infrastructure they control. Download the weights and read the full results and evaluation protocol in English: huggingface.co/maritaca-ai/S… Evaluation repository: github.com/maritaca-ai/obser…