Lumo is a privacy-focused AI assistant developed by Proton. Distinguished by its commitment to data privacy and security, Lumo ensures that all chat conversations remain confidential and are not tracked or recorded. Furthermore, it does not retain any user data on its servers. This aim is achieved through zero-access encryption, meaning user conversations can only be decoded and read on the originating device and are invisible to all other entities, including Proton. Lumo embodies transparency and trustworthiness; its code is fully open source, allowing independent verification of its private and secure nature. Moreover, it assures that user data will not be used for training the model. This privacy-centric AI assistant gives its users full control over their data, promising not to share it with third parties such as advertisers or governments. Adherence to GDPR is guaranteed as Lumo is a European service, with provisions for users to delete their data anytime. Lumo is a creation of the team behind privacy-first services like Proton Mail and Proton VPN, and is owned by a Swiss nonprofit. Unlike most Big Tech AI, Lumo does not base its functionality on data harvesting, steadfastly valuing user privacy over profit.