Lucien
Privacy Policy
Last updated: July 23, 2026
This policy describes how the Lucien mobile app ("the app", "we") handles your information. Lucien is a local-first app: it is designed so that your data stays under your control, on your device and in your own storage.
1. Who is responsible
Lucien is published by an independent developer. For any question about privacy or your data, contact us at: app.lucien.france@gmail.com.
2. The principle: no server, no central collection
We operate no application server and store none of your data on our infrastructure. We have no access to your documents, photos, records or conversations. Your data lives in two places that you control:
- On your device (local database and files);
- In your own Google Drive account, for backup.
3. Data processed
| Category | Detail | Purpose |
|---|---|---|
| Google account identity | Unique identifier, name, email address and profile picture, obtained when you sign in via Google Sign-In / Firebase Authentication. | Authenticate you and personalize the app. |
| Content you create | Documents, photos, videos, notes, links, records and repair history you add. | Build your personal encyclopedia. |
| Camera and photo library | Access to the camera and your photos, only when you choose to capture or import content. | Photograph a breakdown, a label, a meter; illustrate your records. |
| Google Gemini API key (optional) | Your own key, if you choose to enable AI features. Stored only in the device's secure storage. | Let you use the AI assistant with your own key. |
Lucien does not collect your location, your contacts, or any audio recording through a dedicated module. There are no ads, no trackers and no analytics.
4. Google permissions requested and storage
Lucien requests the minimum Google permissions ("scopes") needed to work. Here is each one and its purpose:
| Google permission | Why Lucien requests it |
|---|---|
Basic identityopenid, email, profile |
Sign you in with your Google account (via Google Sign-In / Firebase Authentication) and show your name and avatar. |
.../auth/drive.file |
Create and manage only the files Lucien places in a "Lucien" folder in your Drive (your documents and photos). |
.../auth/drive.appdata |
Back up the app's database to a hidden application-data area of your Drive. |
Your content is stored locally on your device (SQLite database + files) and backed up to your own Google Drive. Lucien never accesses other files in your Google Drive: the drive.file scope only grants access to files created by the app itself.
5. Artificial intelligence features (your key)
AI features are optional and follow a "bring your own key" (BYOK) model. When you enable them, the content relevant to your question is sent to the Google Gemini API using your own API key. This key is stored only in your device's secure storage: it is never sent to our systems, never included in the Drive backup, never logged. Gemini's processing is then subject to Google's Gemini API terms and policy.
6. Third-party services
Lucien relies on the following services:
- Google — Firebase Authentication (sign-in), App Check / Play Integrity (anti-abuse protection), Google Drive (your backup) and Google Gemini (AI, with your key). See Google's privacy policy.
- Expo / EAS — for building the app and delivering software updates. See Expo's privacy policy.
We do not sell or share your data for advertising purposes.
7. Retention and deletion
Since we store no data, retention is up to you. You can delete your data at any time and revoke Lucien's access to your Google account. Step-by-step instructions are on the Account and data deletion page.
8. Security
Communications with Google services are encrypted in transit (HTTPS/TLS). Your Gemini API key is kept in the operating system's secure storage. Access to your account is protected by App Check (Play Integrity).
9. Children
Lucien is a general-audience app intended for adults. It is not designed for or directed at children.
10. Compliance with the Google API Services User Data Policy
Lucien's use of information received from Google APIs adheres to the Google API Services User Data Policy, including its Limited Use requirements.
In concrete terms: data from your Google account (identity) and your Google Drive obtained through these APIs is used solely to provide and improve features visible to you within the app; it is not transferred to third parties, used for advertising, or sold, and no human reads it except with your explicit consent, for security reasons, or where required by law.
11. Changes
We may update this policy. Any significant change will be posted on this page with a new "last updated" date.
12. Contact
For any question: app.lucien.france@gmail.com.