Frontend Engineer; Lumo

Join Proton and build a better internet where privacy is the default

At Proton, we believe that privacy is a fundamental human right and the cornerstone of democracy. Since our inception in 2014, founded by a team of scientists from CERN, we have been dedicated to providing free and open‑source technology to millions worldwide, ensuring access to privacy, security, and freedom online.

Our journey began with Proton Mail, the largest secure email service globally, and has since expanded to include Proton VPN, Proton Calendar, Proton Drive, Proton Pass, Proton Wallet, and Lumo by Proton. These tools empower individuals and organizations to take control of their personal data, break away from Big Tech’s invasive practices, and defeat censorship. Our work impacts hundreds of millions of lives, from activists on the front lines defending freedom to leaders in governments protecting sensitive information.

Proton is a profitable company that does not rely on VC funding, supporting over 100 million users with a growing team of more than 500 people from over 50 countries. We value intelligence, learning potential, and ambition in our hiring process.

Lumo is Proton’s privacy‑first AI assistant that fundamentally reimagines how AI should work—empowering users without exploiting their data. Unlike traditional AI platforms that harvest user conversations for training and profit, Lumo operates with zero‑access encryption, keeps no server‑side logs, and ensures conversations remain completely confidential.

Built by the team behind Proton Mail and Proton VPN and backed by the nonprofit Proton Foundation, Lumo represents a paradigm shift in AI development. We believe the benefits of AI are too great to miss, but the privacy risks of current implementations are too serious to ignore. Lumo is based on open‑source language models, operates from Proton’s European datacenters, and provides unprecedented transparency.

Our Mission
:
To deliver the full power of artificial intelligence while maintaining user privacy as an uncompromising core principle. We’re building an AI that only works for you, not the other way around—your conversations remain confidential and your data stays fully under your control, never shared, sold, or stolen.

Our Technology
:
Lumo implements multiple layers of encryption throughout the entire pipeline, from device‑to‑server communication through to long‑term storage, creating a privacy architecture that is simply much stronger than anything else on the market. The platform runs on open‑source models including Mistral’s Nemo and Nvidia’s Open Hands 32B, with full source‑code transparency.

We are seeking a passionate and skilled Frontend Engineer to join our growing Lumo AI team. You’ll work across all functions of Lumo, turning designs into responsive, fast, and reliable interfaces. Your code will shape the day‑to‑day experience of users, making it smoother, clearer, and more enjoyable.

Full Stack Engineering
Create, evolve, and sustain high‑performance features that tie together the front‑end and back‑end layers of our modern stack. Ensure every component scales smoothly and integrates cleanly.

• Turn UI mockups into production‑ready React components.
• Integrate those components with our backend services using Type Script and modern data‑fetching patterns.
• Optimize performance so pages load instantly even on slower connections.
• Collaborate closely with product managers, designers, and other engineers to ship features end to end.
• Own the quality of your work: write tests, document decisions, and participate in code reviews.
• Spot friction in the user journey and fix it before it becomes a complaint.

• Strong expertise in React.
• Solid grasp of Type Script and JavaScript fundamentals.
• Experience with state‑management and data‑fetching libraries.
• Ability to produce clean, maintainable code without cutting corners.
• Good communication skills and a willingness to give and receive honest feedback.
• A proactive attitude—identify problems and solve them without waiting for direction.

• Exposure to AI or large language model products.
• Python scripting for tooling or data…