Lumo
Proton's privacy-first AI assistant: zero-access encrypted chats that even Proton can't read.
About
Lumo is an AI assistant launched by Swiss privacy company Proton in July 2025. Every conversation is protected by zero-access encryption, Proton keeps no server-side chat logs, and chats are never used to train models. It runs on open-source models including Mistral variants, OLMO 2 32B, OpenHands 32B, and others, with a routing layer sending each query to a suitable model, and it can analyze uploaded files and access Proton Drive documents. A Ghost mode makes logged-in chats disappear when closed.
Lumo is free to use at lumo.proton.me with no Proton account required, and there are iOS and Android apps plus Lumo Plus and Lumo for Business tiers. The client-side code is open source on GitHub. TIME named Lumo a Best Inventions 2025 special mention, and TechRadar's hands-on review found the privacy promise holds but noted raw capability trails frontier models, with tight free-tier limits and no image upload support. Inference runs on Proton-controlled servers in Europe under GDPR.
What it can do
- Zero-access encrypted chat history
- No server-side logs and no training on user data
- Open-source models with intelligent routing
- Ghost mode for disappearing sessions
- Encrypted file uploads and Proton Drive access
- Privacy-friendly web search (off by default)
Setup
- Visit lumo.proton.me; no account needed for guest use.
- Chat directly, or sign in with a Proton account to sync encrypted history across devices.
- Toggle web search on if you want it; it is off by default.
- Use Ghost mode for sessions that should vanish on close.
Prerequisites
A web browser or the iOS/Android app; a Proton account is optional.
Use cases
Works with
Trust score — 8/10
Scored 8/10 (verified tier, metrics-v1). Evidence: launched July 23, 2025 by Proton (MacRumors, Neowin, Bleeping Computer); zero-access encryption, no-logs, no-training policy (company statements); TIME Best Inventions 2025 special mention; open-source client code on GitHub; TechRadar hands-on review corroborates privacy claims. Strengths: established privacy vendor, verifiable open-source client, independent reviews corroborate the claims. Docked for: (1) raw model capability trails frontier assistants; (2) free-tier limits are tight. License: proprietary (client open source).
How the trust score is built
Full methodology →- Adoption · stars/downloads, log-scaled vs peers
- 7.0/10
- Maintenance · recency, releases, issue load
- 8.0/10
- Openness · license + docs
- 8.0/10
- Manual review · sanity read + red-flag check
- 8.0/10
- · Launched July 23, 2025 by Proton (MacRumors, Neowin, Bleeping Computer)
- · Zero-access encryption, no server-side logs, no training on chats (company statements)
- · TIME Best Inventions 2025 special mention; open-source client code on GitHub
- · TechRadar hands-on review corroborates privacy claims; free tier with no account required
Sources
Every fact above was checked against these sources. Where a claim comes from the provider and couldn't be independently verified, the text says so.