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Summary
- Private BrainTrust runs AI models on your phone. When you chat with a model on your phone, your text is processed on the phone. We do not receive your chats, memories, recordings or usage counts, unless you choose to send us something, such as a content report.
- In the version installed from our own download site, you can also add a server: one you run, or a third-party AI service. If you choose one, the text of those requests goes to that server. The app labels each answer with where the text went. The app-store version cannot use servers at all.
- The app is for adults (18 or older). Everything it keeps stays in its private storage on your phone, and Android backup is turned off for it.
What the app collects
The app keeps the following, on your phone only:
- Your chats. Conversations, messages, folders (projects) and the personas you create.
- Memories. Facts the app may remember about you or about people you talk with. A memory a model suggests is held as a "proposal". It is not used in any prompt until you read it and accept it. Unaccepted proposals expire.
- People in the coach. For the coaching features and for reply suggestions requested by other Curtilage apps, the app keeps a contact's name, an identifier made from the name and the phone number or email address, and the memories you accepted about that person.
- Audio recordings, if you use the recorder. By default recordings older than 30 days are deleted.
- Content reports. If you report a reply as offensive or harmful, the report is saved on the phone.
- Server connections you add (sideload version only): the name, address, the model, and any API key or access token you enter.
- Models you download or import.
- Usage counts. The app records which features you use (for example "chat started" or "model downloaded"), with a time and a random session number. These records are designed to hold labels and counts, never the text of your chats. You can see them on the in-app dashboard.
- A debug log, only if you turn debug logging on in Settings. The app is built so that the text of chats, prompts, memories and recordings is not written to that log.
- Settings, including a single "I am 18 or older" setting. The app does not ask for your name, date of birth, email address or any account.
Encryption on the phone.
- Audio recordings are always encrypted with AES-256-GCM (Advanced Encryption Standard, Galois/Counter Mode), using a key protected by the Android Keystore.
- The main database (chats, memories, people, personas, server connections and API keys, usage counts) is not encrypted by default. You can turn on database encryption in Settings. It then encrypts the whole database file with a key protected by the Android Keystore.
- Settings, downloaded model files and the debug log are not encrypted by the app.
- This protects data if the phone's storage is copied. It cannot protect an unlocked phone in someone's hand. An optional app lock (fingerprint or face) is off by default.
Where it goes
On your phone
- A model on your phone answers on the phone. The app shows "On this phone" for these answers.
- Voice input uses your phone's built-in speech recognition service, and the app asks it to work offline where it can. Spoken replies use your phone's text-to-speech service. Those services are separate apps on your phone.
Your own server (sideload version only)
- If you add a server you or your household run, and choose a model on it, the text of each request goes to that server. That includes your message, the conversation so far, the persona's instructions and any memories attached to the chat. Whoever runs that server can read and keep it. The app labels these answers "Your server".
- The app guesses "Your server" only for addresses that can only be on a private network (for example a home-network address). Any other address is treated as "Unknown" until you answer "Who runs this server?".
- Web search and web page fetch. If your server offers these tools, a model may ask to search the web or fetch a page. The app shows you the exact search text or address first and sends it only if you tap Allow. The request goes to your server, which does the search or fetch.
- Pairing by QR code. When you scan a pairing code, the camera image is decoded in memory and not saved. The app then contacts the server named in the code to check it.
A third-party service you choose (sideload version only)
- If you add a server run by a company, the full request goes to that company, including any text you ask about. The app labels these answers "Third-party service" and explains that the company may keep your data, have staff review it, or use it to train models, depending on its own terms. We cannot see or change those terms.
- Other Curtilage apps' requests are never sent to a third-party or "Unknown" server unless you chose that server as the model for those requests in Settings.
Other connections the app makes
- Model downloads. When you tap Download, the app downloads the model file from the public website where the model's publisher posts it. That site sees your phone's internet address.
- Update checks (sideload version only). The app checks our download server for a newer version, at most every 6 hours while the app is open, and when you tap "Check now". It is a plain request for a public file; no identifiers or account details are sent. Our server sees your phone's internet address. You can turn the check off in Settings. The app-store version does not check for updates itself; the store delivers updates.
App-store version. The version distributed through an app store cannot connect to any server you add. The app blocks it in its code, not only on screen. Its only network use is model downloads.
Things that leave only when you send them. Exports, a shared chat, a content report, the debug log and the invite link leave the app only through Android's share sheet, a file you save, or your own mail app. A content report opens your mail app with the report filled in, so you can read and edit it before you send it.
Permissions and why
- Internet
- Why the app asks: Model downloads; servers you add (sideload version); update checks (sideload version)
- When: Installed with the app; used only for those actions
- Microphone
- Why the app asks: Voice input, hands-free voice mode and the recorder
- When: Asked the first time you use one of them
- Camera
- Why the app asks: Scanning a server's pairing QR code
- When: Asked only when you tap Scan; if you say no, you can take a photo instead
- Notifications
- Why the app asks: Progress of model downloads and the recorder
- When: Asked by Android on newer versions
- Foreground service (data sync, microphone) and keep awake
- Why the app asks: Lets a large download, or a recording, keep running with a visible notification
- When: Only while a download or recording runs
- Fingerprint or face (biometric)
- Why the app asks: The optional app lock
- When: Only if you turn the app lock on
- Create events in nextCalendar
- Why the app asks: Lets the app add events to the Curtilage calendar app
- When: Granted only if nextCalendar accepts this app's signature
- Install other apps
- Why the app asks: Installs an update you chose to download (sideload version only)
- When: Only when you tap Install
Two more are added by the Android libraries the app uses: "view network connections" and "run at startup". They let Android schedule downloads.
Analytics
- The app sends no analytics, usage data or crash reports to us or to anyone else. It contains no third-party analytics or crash-reporting code.
- The usage counts described above stay on the phone. They are kept for 180 days by default. You can choose 7, 30, 90, 180 or 365 days, turn them off, or clear them all at any time in Settings.
Sharing with other Curtilage apps
Other Curtilage apps can ask Private BrainTrust for AI help, so they do not need their own model. Android only lets an app connect if it is signed with our key or with a certificate on a fixed list for that feature. The app also checks the caller in its own code. Each feature has its own list:
- Messages+ and NextMail — reply suggestions, rewriting, proofreading, summaries, subject lines and spam checks. They send the text you are working on and, for replies, recent messages in the thread with sender labels and times, and the contact's name and number or email address.
- MindVault — mind-map ideas. It sends the map's title and the text and notes of nearby ideas.
- Lantern — journal reflection prompts. It sends the journal text. These requests are only answered by a model on your phone; Private BrainTrust refuses them otherwise. It keeps no record of the journal text.
- nextCalendar — reading an event from a sentence, and summarizing events. It sends that text, event titles, places and times, and your time zone.
- NextPhoto Pro — photo tips from camera settings only. No image is sent.
What happens to that data:
- The request is answered by the model chosen as described under "Where it goes". If the server cannot be reached, the app may answer with a model on your phone instead.
- The app keeps a usage record for each request: the feature, the calling app's package name, whether it worked, and whether it was answered on the phone or by a server. It does not keep the text.
- For reply suggestions, the app keeps the contact as a coach person and may propose a memory about them. Proposals are not used until you accept them. Memories about a contact are only given to the app that created that contact.
- If you lock the app, requests that read or write stored memories are refused.
Private BrainTrust also starts other apps only when you ask: "Open as mind map" shares text to MindVault, and "Draft a reply" returns one reviewed draft to Messages+.
Your choices
- Export. "Save a copy of everything" writes one file with your chats, personas, accepted memories and preferences. It is not a restore point. Server connections and keys are included only if you opt in and set a passphrase; they are then encrypted with that passphrase. Memories can also be exported as files, recordings as WAV files, and the debug log on its own. Exported files are not protected by the app.
- Delete. You can delete a chat, a memory, a recording or all recordings, the debug log, and all usage counts.
- Turn off. You can turn off usage counts, update checks (sideload version) and debug logging, remove servers, and turn on database encryption and the app lock.
- Uninstall. Uninstalling removes everything the app stored on the phone. Because Android backup and device transfer are turned off for this app, there is no copy in a phone backup. Copies you exported, and anything already sent to a server you chose, are not removed.
Children
Private BrainTrust is for people aged 18 or older. Before first use, the app shows this notice:
"Private BrainTrust is intended for people aged 18 or older. Replies are generated by AI models and are not reviewed by anyone before you see them: they can be wrong, and they can be blunt. The coaching features are meant for grown-up conversations — negotiations, conflict, difficult calls."
You must tap "I am 18 or older" to continue. The app saves only that answer on the phone. It does not ask for a date of birth.
Changes to this policy
We will post any changes on this page and update the date at the top.