Custom Lumos

Custom Lumos are purpose-built AI assistants that you can create and configure for specific tasks.

Instead of adjusting your instructions every time you start a chat, you define how a Custom Lumo behaves and it follows those instructions consistently across every conversation.

Custom Lumos are available on both free and paid plans, but you’ll need to have a Proton Account. In this article, we explain:

• Custom Lumo use cases
• Create a Custom Lumo
• Edit a Custom Lumo
• Delete a Custom Lumo
• How to write effective instructions for a Custom Lumo

Custom Lumo use cases

You can set up a Custom Lumo for any task that you might ask an AI assistant to do. Here are some examples of what they can help with:

• Maintain consistent writing styles. If you frequently write emails, blog posts, or documentation in a specific voice, create a Custom Lumo dedicated to that style. For example, you might ask it to “Always use a professional yet approachable tone, avoid jargon, and keep paragraphs under three sentences.” Whether you’re drafting a quarterly report or a newsletter, the assistant will automatically apply those rules every time.
• Set up language translation flows. You can build assistants tailored for specific language pairs or regional nuances. Instead of asking general translation questions, create an “English/French Technical” Lumo with instructions such as “Translate technical documentation from English to French, ensuring precise terminology for engineering concepts and using formal ‘vous’ pronouns.” This keeps translations accurate and culturally appropriate across multiple projects without manual correction.
• Create niche research assistants. For deep dives into specific domains, set up a Custom Lumo with a specific focus. You might ask it to “Act as a legal research assistant specializing in Swiss data privacy law, citing relevant articles from the DSG/DSGV and providing summaries in bullet points.” This means you can jump straight into complex queries without re-establishing the legal framework and scope for each question.

Create a Custom Lumo

1. Go to lumo.proton.me(neues Fenster) or open the Lumo mobile app, and sign in with your Proton Account.

2. Under the chat window, select Tools > Custom Lumos.

3. Select + Create at the bottom of the pop-up.

4. Configure your Custom Lumo:

• Name
• Description: What you want your Custom Lumo to help with.
• Instructions: Describe the role, scope, and behavior you want Lumo to adopt. Need help writing instructions?
• Conversation starters: You’ll see these example prompts when you start a conversation.

Once you’re done, select Create agent to confirm.

Your Custom Lumo is now created, and you can start using it by choosing it from your list of Custom Lumos.

Edit a Custom Lumo

1. Go to lumo.proton.me(neues Fenster) or open the Lumo mobile app, and sign in with your Proton Account.

2. Under the chat window, select Tools > Custom Lumos.

3. Find the Custom Lumo you want to edit and select the Edit (🖊) icon.

4. Once you’re done making changes to your Custom Lumo, select Save changes.

Delete a Custom Lumo

1. Go to lumo.proton.me(neues Fenster) or open the Lumo mobile app, and sign in with your Proton Account.

2. Under the chat window, select Tools > Custom Lumos.

3. Find the Custom Lumo you want to edit and select the Edit (🖊) icon.

4. Select Delete to permanently delete this Custom Lumo.

How to write effective instructions for a Custom Lumo

A Custom Lumo performs best when its instructions are clear and direct. Think about the job you want it to do, the format you want the output in, and the rules it should follow every time. Avoid vague language.

A good set of instructions usually includes:

• Role and purpose: Define what the Custom Lumo is for and who it should act like.
• Core behavior: Explain what it should do first, what matters most, and how to approach the task.
• Output style: Tell it how to structure responses, how much detail you need, and whether to use bullets, tables, or short paragraphs.
• Tone and voice: Define how you want responses to sound. For example, you might ask it to sound formal, friendly, concise, technical, or persuasive.
• Important rules: Add any boundaries, must-follow preferences, or things to avoid.
• Examples: Whenever possible, include sample outputs so the Custom Lumo has a clear model to reference.

It also helps to keep instructions focused on one task. Custom Lumos work best with a single clear purpose — giving them multiple things to do at once can affect performance.