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Is Proton Lumo private? What it keeps, what it encrypts, and what it can't

October 8, 2026

Yes, by the standards of the category. Per Proton, Lumo keeps no logs of what you ask or what it replies, doesn't use your chats for training, runs open-source models on servers Proton controls in Europe, and stores saved chat history with zero-access encryption, so Proton can't read it. Guest chats are erased when the session ends. The limit is the one every cloud AI shares: the server has to read your message to answer it, so you are trusting Proton's no-logs policy for that moment. If you want no history to protect at all, nixm keeps no transcript.

The short answer

Lumo is Proton's AI assistant, from the company behind Proton Mail and Proton VPN, and it is built around the same promise. On paper it is one of the most private mainstream chatbots: no logs, no training on your chats, no third-party model provider, and history that is encrypted so the company holding it can't read it. Nearly everything below comes from Proton's own Lumo privacy page, so it describes policy and design, not an independent audit.

What Lumo keeps

It depends on how you use it:

  • As a guest, with no account: per Proton, the conversation is erased at the end of each session.
  • Signed in on Free or Plus: your chat history is saved so you can come back to it, and it is stored with zero-access encryption, meaning it is encrypted with a key Proton doesn't hold.
  • Logs and metadata: Proton says it keeps no logs of your questions or Lumo's replies, and that Lumo doesn't store metadata such as timestamps, IP addresses or chat context.

After Lumo processes a message and answers, Proton says the data used to generate that answer is erased.

Zero-access is not the same as end-to-end

This is the part most coverage skips, and Proton itself is careful with the wording. It describes Lumo as using zero-access encryption for stored chat history and TLS for data in transit. It does not call Lumo end-to-end encrypted, and it can't be: to answer you, the model running on Proton's servers has to read your message in plain text. Zero-access protects the saved history afterwards. For the moment of answering, you are relying on Proton's no-logs policy.

That is not a flaw unique to Lumo. Every cloud AI has to see the prompt to answer it; the difference between services is what happens next. The broader distinction is laid out in encrypted vs never stored.

Training, models and where it runs

  • No training: Proton says Lumo doesn't use your chats to train its models.
  • Open-source models on Proton's servers: Lumo runs open models, including the Qwen and GLM families and the Swiss Apertus model, exclusively on servers Proton controls, so your chats aren't sent to an outside AI company.
  • Built in Europe: Proton describes Lumo as built and based in Europe.
  • One exception: feedback on the Apertus model is anonymised before Proton shares it with the university research teams behind it.

Web search

Lumo can search the web to answer, but the feature is optional and off by default. When it is on, your query goes to the search engines Proton has chosen, which is worth knowing before you search for something sensitive.

So is Lumo private?

For a chatbot that keeps a history, Lumo is close to the best design available: the history exists, but the company holding it can't read it. That makes it a strong fit if you want a long-running assistant with a searchable past. The trade-off is that the past exists. It sits on your devices and, encrypted, on Proton's servers, and it is only as safe as your account and your devices. How it compares with the rest of the field is in the most private AI chatbot and what each AI chatbot keeps.

The version with no history to protect

Lumo's answer to privacy is to lock the record. nixm's is not to keep one. nixm doesn't keep a transcript. A distilled log of the session stays with the signal for seven days, then dissolves, along with any images you uploaded. There is no account needed to start and no archive to encrypt. If you need to come back to a conversation months later, Lumo fits better. If you want to think something through and have it gone within a week, that is what nixm was built for.

frequently asked

Is Proton Lumo private?

By the category's standards, yes. Per Proton, Lumo keeps no logs, doesn't train on your chats, runs open-source models on servers Proton controls, and stores saved history with zero-access encryption so Proton can't read it.

Is Lumo end-to-end encrypted?

No. Proton describes zero-access encryption for stored chat history and TLS in transit. The model has to read your message to answer it, so for that moment you rely on Proton's no-logs policy.

Does Lumo save my chats?

Signed in on Free or Plus, your history is saved with zero-access encryption so you can return to it. As a guest, Proton says the conversation is erased at the end of the session.

Does Lumo use my chats to train AI?

Proton says it doesn't. Feedback on the Apertus model is the one exception: it is anonymised before being shared with the university research teams behind that model.

Which AI models does Lumo use?

Open-source models, including the Qwen and GLM families and Apertus, run on servers Proton controls rather than an outside AI provider.

Does Lumo log my IP address?

Proton says Lumo doesn't store metadata such as timestamps, IP addresses or chat context, and keeps no logs of questions or replies.

Is there an AI chat that keeps no history at all?

nixm keeps no transcript. A distilled log of the session stays with the signal for seven days, then dissolves, along with any images you uploaded, and no account is needed to start.

try it now — no account, no transcript kept. even the signal dissolves in seven days.

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