Luther
Privacy Policy
Last updated: 14 September 2026
Luther is an app for everyday mental well-being. What you type into it is personal, so this page says plainly what we collect, who else sees it, where it lives and how to erase it. No legal padding.
Who is responsible
Luther is operated by Mikhail Dubrovskii IE, a sole proprietorship registered in Yerevan, Armenia. For anything in this policy, write to deeptalk.support.help@gmail.com.
What we collect
| Data | Why |
|---|---|
| Your email address, or the account identifier from Google Sign-In | To create your account and let you sign back in |
| Optional profile: first name, age range, gender, and what brought you to the app | Only to make the AI's replies fit you. Every field can be skipped |
| Your conversations with the AI, including transcripts of voice messages and photos you send | To show your chat history and give the AI the context of what you already said |
| Psychological test answers and results, mood check-ins, diary entries, completed exercises, programme progress, achievements | These are the features themselves — your history, charts and weekly reflections are built from them |
| What Luther remembers: a few dated notes and a short summary of what you are working on, written from your own conversations, tests, check-ins and exercises — and from your diary, unless you switch that off | So you do not have to start every conversation from the beginning. You can read every note and delete any of them |
| Subscription status and the Google Play purchase identifier | To unlock the paid tier and handle renewals and refunds |
| A push notification token, if you allow notifications | To send the reminders you asked for. What a reminder may say is described under “Reminders” below |
| The IP address recorded when you accept the terms | Proof of consent, kept as a single timestamped record |
| Technical counters of AI usage: number of tokens, cost, response time | To watch spend and reliability. These records contain no message text |
| A crash report if the app fails: what broke and where in the code, plus device model, operating system and app version | To find and fix crashes. A report carries no message text, no diary entries and no test answers |
What we do not do. We do not sell your data. We do not show ads. There is no advertising SDK and no behavioural analytics in the app: nothing tracks what you tap in order to build an advertising profile of you. What Luther remembers is a different thing entirely: it is written from what you tell it, it is shown to you, and you can delete it — the section below explains how. The one thing we do measure is whether the app crashed, and that report is stripped of anything you wrote. We do not use your conversations to train AI models.
Voice and images
A voice message is sent for transcription and converted to text; the audio itself is not stored on our servers — only the resulting text, as part of the conversation. A photo you send is stored in object storage inside the European Union, rented from the company that hosts our server, and served from a link with a random, unguessable name.
What Luther remembers
Luther keeps a short memory about you: a few dated notes and a brief summary of what you have been working on. It is written from your own content — your conversations, test results, mood check-ins, completed exercises and programme progress — and it is added to the AI's instructions, so that you do not have to explain yourself again in every conversation. It is also what lets Luther start a conversation itself, for instance by coming back to a question you left open.
Your diary is included only while you allow it. The switch is called “Luther reads my diary” and lives in Profile → What Luther remembers. It is on by default; turn it off and diary entries and mood notes stop feeding the memory. Test results always do.
That same screen shows every note in your language and lets you delete one or all of them. A deleted note is gone from what reaches the AI in your next conversation, and the earlier versions of the memory that contained it are deleted with it. Erasing your account erases the memory along with everything else.
This memory exists for one purpose: to make Luther's replies fit you. It is not used for advertising, it is not shared with anyone, and it is not used to train AI models. The one line of it that can leave the app is the text of a reminder, and only if you switch that on — the next section explains.
Reminders
If you allow notifications, Luther may send you a reminder — at most one a day, within the hours you choose in the app. By default the text of a reminder never says what you talked about: it says that Luther has something for you, or how long it has been, and nothing more. The topic stays inside the app.
“Show the topic in reminders” is a switch you can turn on in Profile → Settings → Reminders. It is off by default. With it on, a reminder may name the question Luther wants to come back to: one short line written from your own conversations, taken from what Luther remembers. It travels to your phone through Firebase Cloud Messaging like every other notification, and you will see it in the notification shade once the phone is unlocked.
Such a reminder is marked as private, which is Android's way of keeping the details off the lock screen. Whether that works depends on your phone: with a PIN, pattern or fingerprint set and “sensitive notifications” hidden in your phone's settings, the lock screen shows only the neutral line; with no screen lock, or with sensitive content allowed on the lock screen, the question is readable there by anyone holding your phone. Switch the topic off and reminders go back to saying nothing about it. Tapping a reminder opens the app either way.
Who else processes your data
To make the app work we pass some data to the services below. They act as processors on our behalf.
| Service | What it receives | Where |
|---|---|---|
| Fireworks AI | The text of your messages, the photos you send, your test answers, and — when the memory above is updated — your diary entries, mood notes and exercise results. Used to generate replies and interpretations and to write what Luther remembers | United States |
| OpenAI | Voice recordings, to transcribe them into text. Nothing else | United States |
| Google Play Billing | Purchase and subscription data | Global |
| Firebase Cloud Messaging | Your push token, when notifications are enabled, and the text of each reminder — which names the topic of a conversation only if you switch that on | Global |
| Sentry | Crash reports: the error and its place in the code, device model, operating system and app version | European Union |
| Resend | Your email address and the sign-in code, when you sign in by email. Nothing else | United States |
Where your data is stored
Our database and the application run on a single server located in France, in the European Union. Photos you send in chat are held in object storage rented from the same hosting company, also inside the European Union. Sending messages to the AI services above means that text leaves the EU for the United States; there is no way to generate an AI reply without it. If you would rather not have your words processed in the US, please do not use the chat and test interpretation features.
How long we keep it
Your data stays until you delete it. There is no silent expiry and no archive we keep afterwards. When you erase your account, conversations, test results, mood entries, diary entries, stored images and everything Luther remembered are deleted immediately and permanently. We keep only anonymised transaction records — required for accounting — and they no longer identify you.
One qualification, because “permanently” should mean what it says: the database is backed up every night, and the last seven days of those backups are kept on the same server. An erased account is gone from the live database at once, and anything you delete inside the app within two days; either way it rotates out of the last backup a week after that.
How to delete your data
In the app: Profile → Settings → Delete account. It takes effect at once. Signing up again with the same address gives you a new, empty account — the old history does not come back.
Without installing the app, use the data deletion request page.
Your rights
You can ask us what we hold about you, request a copy, have it corrected, or have it deleted. Write to deeptalk.support.help@gmail.com and we will answer within 30 days. If you are in the EU or the UK and you believe we handled your data badly, you may complain to your national data protection authority.
Security
All traffic between the app and our servers is encrypted with TLS. Access to the server is restricted, and the database is not reachable from the internet. No system is perfectly secure, so please treat what you write in any app accordingly.
Children
Luther is for adults — 18 and over. We do not knowingly collect data from children. If you believe a child has created an account, write to us and we will delete it.
Luther is not medical care
Luther is a self-help tool. It is not therapy, it does not diagnose, and it is not a substitute for a doctor or a psychologist. It is not an emergency service. If you are in crisis or thinking about harming yourself, contact your local emergency number or a crisis helpline right away.
The psychological questionnaires in the app are screening instruments, not diagnoses. A result is a reason to talk to a professional, never a verdict.
Changes to this policy
If we change how we handle your data, we will update this page and the date at the top. Significant changes will be announced in the app.