Lumo

Lumo runs on Proton-controlled servers in Switzerland and is migrating to Germany. A Norway buildout is planned, reportedly a CHF 100M investment, following Switzerland's proposed VÜPF surveillance-law reforms that Proton does not trust. Proton states Lumo never runs on third-party cloud platforms. Switzerland, Germany, and Norway all have strong data-protection regimes.

Proton markets Lumo with "zero-access encryption," but this guarantee applies only to stored chat history, not to live exchanges. Queries are encrypted in transit for Proton's GPU inference servers, which decrypt them into plaintext to generate a response, then re-encrypt the result with zero-access encryption. Proton states the plaintext is not logged afterward, but the service can read a query while processing it, short of true end-to-end encryption where the provider cannot read content at all.

Lumo's models run exclusively on Proton-controlled infrastructure; Proton states no user data is sent to third-party AI providers such as OpenAI or Anthropic. Proton's privacy documentation for Lumo does not disclose sharing conversation data with marketing partners or other third parties, consistent with Proton's no-data-sharing posture across its product line.

Proton states plainly that "Lumo doesn't use your chats to train the AI models" — framed as categorical rather than an opt-out a user must find and enable. No independent audit of this claim was found, but it matches Proton's general no-training stance across its products.

Lumo's web and mobile client apps are open source under GPLv3, but the backend service—model routing, system prompt, and the architecture running the assistant—is closed. At launch, Proton's marketing claimed "my code is fully open source," which Proton support later walked back when pressed, calling it "our long-term intention... not necessarily the instantaneous state upon launch." The European Open Source AI Index reviewed Lumo in August 2025 and concluded "nothing about it is currently open," comparing Proton's framing to calling Windows open source because a GitHub repo exists for Windows Terminal. Proton's open-source page now lists Lumo's client repos alongside products like Mail and Drive but without a linked audit report. The Lumo 2.0 announcement (June 2026) still describes the codebase as "fully open source," showing the same framing persists almost a year after it was first disputed. Genuine open client code exists, but the substantive product remains proprietary.

No independent security audit or certification specific to Lumo was found. Proton's broader SOC 2 Type II certification and Proton VPN no-logs audits (via Securitum) cover other products, not Lumo's backend or its "zero-access encryption" implementation. Proton's open-source page lists a linked third-party audit report next to Mail, Calendar, Drive, VPN, and Pass, but no equivalent audit report is listed for Lumo—confirming the gap from Proton's own disclosure.

Beyond standard GitHub pull requests on the open client repositories, no documented governance model, roadmap-input process, or code of conduct specific to Lumo exists. Development direction is set internally by Proton.

Lumo's primary paid tier is a monthly subscription (Lumo Plus) offered alongside a free tier, with no lifetime or one-time-purchase option available. This tiered subscription structure — a free tier plus a recurring paid plan — is confirmed on Proton's official pricing page.

Lumo's free tier offers limited access to the "Max" model, with a capped chat history and message count, one project, and limited image generation. It is usable but restricted, with no indication it monetizes user data to offset the limits.

Plans and prices are clearly listed on Proton's pricing page. No lawsuit or regulator finding alleging dark-pattern billing was found. However, Proton Unlimited, its long-running all-in-one bundle, does not include Lumo Plus. This requires a separate purchase for advanced AI features. Multiple threads on Proton's community feedback platform describe this as misleading given the "Unlimited" naming. They also report confusing upgrade flows when adding Lumo Plus to existing Unlimited subscriptions.

Lumo Plus is priced flat worldwide with no documented regional or purchasing-power adjustment. Users have requested regional pricing on Proton's feedback forum, citing Spotify as a company that adjusts. This request remains open.

Proton provides no native chat-export feature for Lumo; its support documentation does not describe one. The only way to get data out is an unofficial, Proton-unaffiliated browser extension, not a vendor-provided export path.

Lumo is a cloud-only service with no self-hosting option. The open-source client apps require Proton's backend to function, and there are no self-hosting instructions on Proton's site or GitHub.

Lumo requires an active internet connection. The native apps show a connection-error screen instead of offering offline use. No offline mode is documented.

Lumo is available on the web, iOS, and Android, and — since March 31, 2026 — as a de-Googled build (version 1.2.18-nogms) distributed through F-Droid, a non-proprietary Android app repository. A native desktop app is in development per Proton's 2026 roadmap, but it has not yet been released. The F-Droid distribution satisfies genuine availability on an open platform.

No accessibility statement, VPAT, or WCAG conformance claim was found for Lumo or Proton's apps generally. No independent evidence of specific accessibility features (screen-reader support, keyboard navigation) was found either, so there is no basis to credit even partial, undocumented support.

Since June 17, 2024, Proton AG's controlling shareholder is the non-profit Proton Foundation, a Swiss foundation with a legally binding charter and veto power over any change of control. Early VC investor Charles River Ventures fully divested in 2021, transferring its stake to FONGIT, another non-profit foundation. By the 2024 restructuring, no VC influence remained. Proton AG currently has no external investor control.

Proton underwent a real structural change within the last three years. The June 2024 transition placing Proton Foundation in control was a deliberate move to lock in mission alignment and block any future hostile takeover or VC pressure, not a loss of independence. It is best seen as an internal restructuring rather than an acquisition. Proton was not acquired, and its independence was, if anything, strengthened by the change.

Proton publishes explicit, verifiable commitments: Lumo conversations are never used for training, nothing is logged server-side, and Proton states that this makes it impossible to comply with government data requests, since no data exists to hand over. Proton operates under Swiss privacy law rather than US CLOUD Act jurisdiction. These are public commitments, though the "zero-access" framing (see 1.2) shows Proton's marketing sometimes overstates the technical guarantee.

Proton AG holds ISO 14001 (environmental management) and ISO 50001 (energy management) certification and uses Direct Liquid Cooling at its self-operated data centers in Switzerland, Germany, and Norway, cutting cooling power by roughly 20%. Proton publishes no explicit renewable-energy percentage or climate-neutrality target, and no dedicated sustainability report was found. These are partial indications rather than a coherent, quantified environmental policy.

Lumo publicly launched on July 23, 2025. At the time of this evaluation, it has been actively maintained for roughly one year. It is established enough to have a track record but still under the two-year threshold.

Lumo 2.0 shipped June 30, 2026 — described by Proton as its largest update since launch, adding reasoning modes, image generation and editing, memory, Projects, custom assistants, and a new Business tier. The release was independently covered by TechCrunch and MacRumors, and a desktop app is in active development per Proton's public 2026 roadmap.