Apertus is a fully open large language model developed by researchers at EPFL(new window), ETH Zurich(new window), and the Swiss National Supercomputing Centre (CSCS). Its architecture, training data, and methods are open, and it’s trained on publicly available data, respecting opt-out requests and filtering out personal details. It fills an important role in today’s AI landscape by providing a fully open source model with a transparent and reproducible training pipeline. In a world dominated by US and Chinese models, Apertus is instrumental in Europe’s tech sovereignty.

The world’s leading AI models have millions of people using them every day, creating real-world feedback loops that help make them better. Fully open models developed in an academic context do not have access to feedback at the same scale, limiting their ability to compete at the frontier.

With this partnership, that could start to change. Proton is introducing a feedback mechanism that connects people using Apertus in Lumo with the researchers building it. Tens of millions of Lumo users around the world can now choose to contribute feedback, helping independent, ethical, and truly open source AI become more competitive.