Platform Notes

iOS

• HealthKit requires a real device (not simulator) for most data types
• RequestPermissions on iOS does NOT tell you if the user denied access (Apple privacy policy) — it may return true even when denied
• Percentage values (body fat, O2 saturation) are returned as 0–100, not 0–1
• Your app requires a provisioning profile with HealthKit capabilities enabled
• Observe uses HKAnchoredObjectQuery for push-based real-time delivery — no polling needed

Android

• The Health Connect app must be installed on the device
• Minimum SDK version must be 28 (Android 9) or higher
• Body fat percentage and oxygen saturation use individual record queries (Health Connect does not provide aggregate metrics for these types)
• Observe uses Health Connect change tokens with polling (default 5 seconds) — Health Connect does not support push-based observation