Your health data lives on your device and in your private iCloud database. There is no TrainInsight server holding any of it. The readiness scores, training load, sleep insights, and AI summaries are all computed locally from the HealthKit numbers that are already on your iPhone.
HealthKit. With your permission, TrainInsight reads your heart-rate variability, resting heart rate, sleep stages, workouts, body weight, VO₂ max, active energy, and time-in-daylight (iOS 17+). It does not write to HealthKit — every metric you see in the app is read-only, derived from samples Apple Health already has. HealthKit data never leaves the iOS HealthKit boundary; the app reads within it but doesn't copy that data into any separate cloud.
The AI Coach and Health Summary. When you ask the coach a question, or the dashboard generates the daily summary, your prompt plus a 7-day data block (sleep, HRV, RHR, readiness, training load, daylight) goes to whichever AI provider you've selected. By default that's Apple Intelligence on iOS 26+, which runs on-device. The on-device LLM (a one-time MLX-backed unlock) also stays on the device. If you've configured a cloud provider with your own API key — Claude, OpenAI, or a custom endpoint — the prompt and data block go to that provider directly under their privacy terms. TrainInsight proxies nothing; the cloud providers don't get your raw HealthKit samples, just the aggregate context block the app would otherwise have rendered to you.
The AI Request Log and AI Usage tracker in Settings show recent prompts, token totals, and estimated costs for debugging and budget awareness. They live on the device — the request log clears at app quit; the token/cost totals persist in local settings. Nothing in either is transmitted anywhere.
No analytics. No third-party SDKs. No tracking pixels. No advertising. The app contains nothing that would let me, or anyone else, observe how you use it.
Email me with questions: chen.he@icloud.com.