Mainstay Privacy Policy

Effective Date: October 4, 2026 · Policy Version 1.3

Mainstay ("the App") is a personal AI fitness coach for iPhone and Apple Watch, operated by ALC SFR LLC, a Wyoming limited liability company, doing business as Mainstay ("we," "us"). This policy explains what data we collect, how we use it, who else handles it, and your rights. The App is offered only in the United States.

The short version: your data is used to coach you and to make the coaching better. It is never used for advertising and never sold. To coach you, we send your training and health information to Anthropic, the company behind the Claude AI model, and current versions of the App ask you to agree to that first (Section 17 explains older beta builds). Members of the Mainstay team can look at session recordings, coach conversations, and the workouts the AI wrote for you, so we can check the coaching is good and safe. Section 7 explains exactly what that means.

1. Health & Fitness Data (Apple HealthKit)

The App reads and writes the following HealthKit data types with your explicit permission:

• Read: Steps, walking and running distance, active calories burned, exercise minutes, heart rate, resting heart rate, heart rate variability, sleep, VO2max, body mass, and workout history, including workouts recorded by other apps, which are imported into Mainstay when they are 20 minutes or longer. You can delete an imported workout from the App at any time.
• Write: Workout sessions (type, duration, calories burned), heart rate samples recorded during workouts, walking/running distance and cycling distance recorded during cardio sessions, and workout routes for outdoor cardio (see Section 2).

Raw HealthKit samples stay on your device and in Apple Health. Our servers receive daily summary metrics derived from them (sleep duration, resting heart rate, heart rate variability, steps, active calories, VO2max, and body weight), workout summaries (including average and maximum heart rate), and a readiness score we calculate from them. These are stored with your account to personalize your coaching.

HealthKit data is used to personalize your training, track your progress, and show your metrics in the App. As described in Section 6, some of it is sent to Anthropic to generate your plans and coach replies, after you consent. We do not use HealthKit data for advertising, marketing, or similar services, and we do not sell, share, or transfer it to any third party for advertising, marketing, use-based data mining, or data brokerage purposes.

2. Location & Workout Routes (Outdoor Cardio)

If you record an outdoor run, walk, or hike, the App uses your device's GPS to measure distance, pace, and your route, with your explicit location permission.

• Route maps (GPS coordinates) are stored in Apple Health on your device. We do not upload your GPS coordinates or route maps to our servers.
• Our servers receive only summary metrics for each cardio session: activity type, duration, distance, average pace, heart rate summary, and calories. These power your workout history, progress, and coaching.
• Location is used only while recording an outdoor workout. We do not track your location outside of workouts, and we never use location for advertising or profiling.

3. Account Information

When you sign in with Apple, we receive your Apple-provided user identifier and, optionally, your name and email address (which may be an Apple private relay address). This information is used to create and authenticate your account and to contact you about it.

4. Profile, Workout & Training Data

During onboarding and while you use the App, you give us profile details (first name, age, sex, height, weight, experience level, goals, schedule, equipment, and anything you tell us about injuries, limitations, or what you like and dislike). The App also stores your workout plans, exercise logs, sets, reps, weights, personal records, check-in ratings (how you slept, how sore you are, how motivated you feel), post-workout feedback, feedback and bug reports you send from the App, and the messages you exchange with the AI coach. This data is stored on our servers, associated with your account, and not shared with other users.

5. Exercise Demonstrations

Exercise demonstration videos and images in the App are licensed from a third-party content provider and delivered from our media storage on Cloudflare. Loading them sends Cloudflare ordinary request information (such as your IP address and the file requested). The content provider does not receive any of your data.

6. AI Coaching and Anthropic

Your workout plans, coach chat replies, check-in messages, and some summaries in the App are written by an AI model, Claude, provided by Anthropic, PBC. To write them, our servers send Anthropic the information the coaching needs:

• your profile: first name, age, sex, experience level, goals, schedule, equipment, starting lifts, likes and dislikes, and your injury and limitation notes;
• your training history: workouts, exercises, sets, reps, weights, personal records, streaks, post-workout feedback, and cardio summaries;
• health metrics derived from Apple Health: sleep duration, resting heart rate, heart rate variability, your readiness score, and workout heart rate summaries; and
• your coach conversations and anything else you choose to tell the coach; and
• feedback, bug reports, and post-workout notes you send us, which the AI sorts into categories so we can act on them, and which may be quoted in an AI-written internal summary for the Mainstay team.

Current versions of the App only start sending this after you agree to it on the consent screen. If you do not agree, the App cannot build plans or coach you, and you can sign out. Beta builds released before the consent screen existed send it without showing the screen; see Section 17.

Anthropic processes this data as our service provider under its commercial terms. Under those terms Anthropic does not use it to train its models. Anthropic's published policy is to delete API inputs and outputs within 30 days, except where it must keep them longer to enforce its usage policy (for example, content flagged as violating it) or to comply with the law.

We keep the exact prompt we sent and the reply we received for each AI-generated workout and coach reply, with your account, for as long as your account exists. This is how we check whether the coaching you received was any good, and fix it when it was not.

7. How We Review Coaching Quality and Safety

An AI coach can make mistakes, so we look at what it actually did. This applies to every user. When you agree on the consent screen, you agree to the following:

• Human review. Members of the Mainstay team may read your coach conversations, the workouts the AI generated for you, what you trained against them, and the feedback you left. This is review of individual accounts, not only anonymous totals. We do it to judge and improve the quality and safety of the coaching, to investigate problems you report, and to fix bugs. Today the team is the founder.
• AI observability. We send each AI prompt and response (including the profile, health metrics, injury notes, and coach messages in it) to PostHog so a single generation can be traced end to end. Only the Mainstay team can see these traces.
• Session recordings. The App records a replay of your screens as you use it, so we can see where the App confused you or broke. Every text field you type into and every image is masked on your device before the recording is sent, so the text of your injury notes, weights, and coach messages does not appear in the recording; other text that the App displays on screen can appear. Recordings go to PostHog, and only the Mainstay team can watch them. In current versions of the App you can turn session recordings off at any time under Profile > Privacy > Session recordings, and recordings never start before you have agreed on the consent screen. Beta builds released before the consent screen existed record every session and have no switch; update the App to get it.

We do not use any of this for advertising, and we do not give it to anyone other than the service providers in Section 11.

8. Analytics & Crash Reporting

• Usage analytics (PostHog). Screen views, feature use, and events such as "workout completed", linked to your account so we can understand how people use the App. A few events carry health-related signals: your check-in ratings (sleep quality, soreness, motivation on a 1 to 5 scale) and whether you reported pain after a workout. Your training profile (experience level, goals, training days) is attached to your analytics profile. Usage events do not include your weights lifted, heart rate, or body measurements.
• Crash reporting (Sentry). When the App or our server hits an error, Sentry receives a crash or error report: what went wrong, your device model, operating system and app version, recent in-app steps leading up to it, and a sample of performance timings. Crash reports from the App are linked to your Mainstay account identifier so we can follow up on a problem you report. Error reports from our server can include details of the request that failed, which may include content you sent in that request.

We do not use third-party advertising SDKs, and we do not track you across other companies' apps or websites.

9. Notifications and Email

With your permission, we send push notifications through Apple's notification service (for example: your weekly plan is ready, a personal record celebration, or a coach check-in). Notification delivery uses a device token that identifies your device, not your health data. You can turn notifications off anytime in iOS Settings. If you email us, your message and our reply pass through our email providers (Section 11).

10. Our Website

Our website, mainstay.fit, hosts these legal pages and our beta application form.

• Beta application form. If you apply, we collect your first name, email address, your answers to the screening questions (years training, sessions per week, iPhone and Apple Watch ownership, coaching history), your acceptance of our documents, and, as a record of that acceptance, your IP address and browser user agent.
• Website analytics. Our server records funnel events (page viewed, application started, application submitted) in PostHog. Before you apply these events use a random identifier; after you apply they use a one-way hash of your email address, never the address itself. Your screening answers are not sent. The website does not set advertising cookies.
• Fonts. Our pages load fonts from Google Fonts, so your browser sends Google a request (including your IP address) when a page loads.

11. Service Providers

We share data only with the service providers needed to run Mainstay. They process it on our behalf under their commercial terms, not for their own purposes:

We do not sell your personal information, and we do not share it for cross-context behavioral advertising. We may disclose information if the law requires it, to protect someone's safety, or as part of a sale or reorganization of the business, in which case this policy continues to apply to it.

12. Data Storage & Security

Account and training data is stored on servers hosted by Railway. All communication between the App and our servers uses HTTPS encryption. Authentication tokens are stored in your device's Keychain. No system is perfectly secure, but we limit access to your data to the people who need it to run and improve the service.

13. Data Retention & Deletion

We keep your data while your account is active. You can delete your account in the App at any time: Profile > Membership and account > Delete account. Here is exactly what happens:

• Deleted right away from our database: your account, profile, workouts, plans, sessions, health metrics, readiness scores, coach conversations, the stored AI prompts and responses, notifications, feedback, goals, and any beta application linked to your account.
• Deleted at our processors: at the same time we ask PostHog to delete your person record, events, session recordings, and AI traces. If PostHog cannot be reached, your deletion still completes on our side; we record the outstanding request and finish it by hand.
• Kept on purpose: the record of which versions of our Terms, Privacy Policy, Beta Program Agreement, and in-app consents you accepted or withdrew, and when (for website applicants, also the name, email address, IP address, and user agent submitted with the form). We keep these because they are our evidence of what was agreed, which can matter after an account is gone. We also keep a short internal record, by account number only, while a processor deletion is outstanding.
• Deleted on the provider's schedule: copies held by Anthropic (see Section 6), crash and error reports held by Sentry (kept for Sentry's retention period and not deleted when you delete your account), email you exchanged with us, and backups of our database, which are overwritten within a limited period.
• Not affected: Apple's own records (your Sign in with Apple connection and purchase history), and data in Apple Health on your device.

Deleting your account does not cancel an active Apple subscription. Manage subscriptions in iOS Settings > your name > Subscriptions. You may also ask us to delete your data by emailing us.

14. Consumer Health Data

This section is our consumer health data privacy policy, written for the Washington My Health My Data Act, Nevada's consumer health data law (SB 370), and similar laws. It applies to "consumer health data", meaning personal information that identifies, or could reasonably be linked to, your past, present, or future physical health. We apply it to every user, wherever you live.

What consumer health data we collect

• Health metrics from Apple Health: steps, distance, active calories, exercise minutes, heart rate, resting heart rate, heart rate variability, sleep, VO2max, body weight, and workout history, as daily summaries and workout summaries.
• Information you give us: age, sex, height, weight, injury and limitation notes, pain or soreness you report, check-in ratings for sleep, soreness, and motivation, post-workout feedback, and anything health-related you tell the AI coach.
• Information we derive: your readiness score and label, training adjustments made because of an injury or limitation, and fitness progress estimates.

Where it comes from

From you (what you type or select in the App), from Apple Health on your device (only the types you permit), and from our own calculations on that data.

Why we collect and use it

To provide the coaching you asked for: building and adjusting your training plans, writing coach replies, estimating your readiness, and showing your progress. We also use it to check and improve the quality and safety of the coaching (Privacy Policy, Section 7), to fix bugs, and to keep records the law requires. We never use it for advertising, and we never sell it.

Who receives it

We share consumer health data only with the processors that handle it on our behalf: Anthropic (to generate plans and coach replies), PostHog (AI observability traces, which contain the prompts above, and check-in ratings and pain reports in usage events), and Railway (hosting of our database). Sentry may receive health data only if it appears in a request that caused a server error. We have no affiliates that receive it, and we do not share it with any other third party.

Your consent

Before we collect consumer health data for AI coaching, current versions of the App show a consent screen that says what we send to Anthropic and how the Mainstay team reviews coaching, and nothing is sent to Anthropic until you agree. Beta testers on builds released before that screen existed agreed through the Beta Program Agreement and see the screen when they update. We will ask again before we collect or share consumer health data for any purpose not described here.

We never sell it

We do not sell consumer health data, and we do not use it to target advertising.

Your rights

• Confirm and access. Ask us whether we collect, share, or sell your consumer health data, get a copy of it, and get a list of every third party and processor that received it, with their contact details.
• Delete. Delete your account in the App (Profile > Membership and account > Delete account) or ask us to delete your consumer health data. We will also tell our processors to delete it, as described in the Privacy Policy, Section 13.
• Withdraw consent. Turn session recordings off in the App (Profile > Privacy > Session recordings, in current versions), or withdraw your consent to AI processing by emailing us or deleting your account. Once you withdraw AI consent we stop sending your data to Anthropic, which means the App can no longer coach you.

How to exercise them, and how to appeal

Email support@mainstay.fit from the email address on your account, or tell us which account is yours so we can verify the request. We will respond within 45 days; if we need more time (up to another 45 days) we will tell you why. We will not charge you or treat you differently for using these rights. If we decline your request, you can appeal by replying with "Appeal" in the subject line; we will answer the appeal in writing within 45 days and explain our reasons. If your appeal is denied, you may contact the Attorney General of your state (in Washington, the Washington State Office of the Attorney General; in Nevada, the Nevada Attorney General).

15. California Residents

This notice describes the personal information we collect, in the categories California law uses. We collect it from you, from your device and Apple Health, and from our own calculations, for the purposes described in this policy.

We use sensitive personal information only to provide the service you asked for and for the other purposes California law permits, not to infer characteristics about you. We do not sell or share personal information (as California law defines "sell" and "share"), and we have no actual knowledge of selling or sharing information of anyone under 16. Depending on your situation, you may have the right to know what personal information we hold about you, to access it, to correct it, to delete it, and to limit the use of sensitive personal information. Use the methods in Section 16. You may use an authorized agent; we may ask the agent for proof of authority and ask you to verify your identity. We will not discriminate against you for exercising these rights.

16. Your Rights (All Users)

Wherever you live, you can access, correct, or delete your data. Most profile details can be corrected in the App. To delete everything, use Profile > Membership and account > Delete account. For anything else, including a copy of your data, email support@mainstay.fit. We respond within 45 days, and you can appeal a decision as described in Section 14. Because we do not sell personal information or share it for behavioral advertising, there is nothing to opt out of.

17. Beta Testing (TestFlight)

If you use a beta version of the App through Apple TestFlight, Apple provides us with beta feedback you choose to send (including screenshots and crash logs) under Apple's TestFlight terms. Beta data handling otherwise follows this policy. Beta builds released before the consent screen existed did not ask for consent in the App and have no session recordings switch; testers using those builds agreed to this processing through the Beta Program Agreement and will see the consent screen when they update. To stop recordings, update the App and use the switch.

18. Children

Mainstay is only for adults 18 and older. It is not directed at children, and we do not knowingly collect personal information from anyone under 18. If you believe someone under 18 has an account, tell us and we will delete it.

19. Changes to This Policy

We may update this policy from time to time. Material changes will be communicated through the App or by email before they take effect, and the version number and effective date above will change. If a change affects how we use consumer health data, we will ask for your consent again where the law requires it.

20. Contact

ALC SFR LLC, doing business as Mainstay, 30 N Gould St, Ste R, Sheridan, WY 82801. Telephone: (415) 763-1344. Questions about this privacy policy or your data: support@mainstay.fit