Health & Fitness

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Explore the technical aspects of health and fitness features, including sensor data acquisition, health data processing, and integration with the HealthKit framework.

Health & Fitness Documentation

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Guidance / Documentation on iOS 18.6.1 Blood Oxygen Saturation
Are there any HealthKit related changes to be aware of in the new update that enables SPO2 / Blood Oxygen Saturation measurements on certain Apple Watch models within the US? I’m aware of processing happening on the phone…. But beyond that: Does this mean values are then saved to Apple Health? Do these models still take background SPO2 measurements in the same way as other models do? Are these values then visible in third party iOS apps as normal through HealthKit? Do these values sync back to the paired Apple Watch HealthKit store for third party apps to access on the Watch? For reference I have an iOS and WatchOS app that, amongst other features, provides the ability to see your SPO2 values in the Watch app, complications and in the iOS app.
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Sep ’25
HKObserverQuery stops delivering updates in background on watchOS 26
Hello, I’m building a health-related app for both watchOS and iOS, which needs to monitor certain health data (e.g., heart rate, active energy). Before updating to watchOS 26, the queries worked reliably without any issues. However, after adapting to watchOS 26, some users have reported that health data updates stop being delivered. What I’ve observed: HKObserverQuery with enableBackgroundDelivery is set up normally. On WatchOS 26, the query sometimes stops delivering updates entirely after a certain point, and once an update is missed, it may stop delivering further updates completely. Restarting the Apple Watch temporarily restores delivery, but the problem reoccurs after some time. This makes background health data monitoring unreliable for my app. Here’s a simplified version of the code we are using: guard let heartType = HKObjectType.quantityType(forIdentifier: .heartRate) else { return } let query = HKObserverQuery(sampleType: heartType, predicate: nil) { query, completionHandler, error in if let error = error { logEvent("Observer error: \(error.localizedDescription)") return } logEvent("Heart rate changed") MyNotificationManager.shared.sendNotification() // Send a local notification completionHandler() } healthStore.execute(query) healthStore.enableBackgroundDelivery(for: heartType, frequency: .hourly) { success, error in if success { logEvent("Background heart rate delivery enabled") } else { logEvent("Failed to enable background heart rate delivery: \(error?.localizedDescription ?? "Unknown error")") } } Could you please clarify: Is this a known issue with HKObserverQuery and enableBackgroundDelivery on watchOS 26? Are there any recommended workarounds or best practices to ensure continuous background delivery of health data? Thank you in advance for your help.
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Oct ’25
WatchOS HealthKit HKObserverQuery crashes in background
I have a watchOS app with a connected iOS app using Swift and SwiftUI. The watchOS app should read heart rate date in the background using HKOberserQuery and enableBackgroundDelivery(), send the data to the iPhone app via WCSession. The iPhone app then sends the data to a Firebase project. The issue I am facing now it that the app with the HKObserverQuery works fine when the app is in the foreground, but when the app runs in the background, the observer query gets triggered for the first time (after one hour), but then always get terminated from the watchdog timeout with the following error message: CSLHandleBackgroundHealthKitQueryAction scene-create watchdog transgression: app<app.nanacare.nanacare.nanaCareHealthSync.watchkitapp((null))>:14451 exhausted real (wall clock) time allowance of 15.00 seconds I am using Xcode 16.3 on MacOS 15.4 The App is running on iOS 18.4 and watchOS 11.4 What is the reason for this this issue? I only do a simple SampleQuery to fetch the latest heart rate data inside the HKObserverQuery and then call the completionHandler. The query itself takes less than one second. Or is there a better approach to read continuously heart rate data from healthKit in the background on watchOS? I don't have an active workout session, and I don't need all heart rate data. Once every 15 minutes or so would be enough.
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Oct ’25
watchOS 26.0.2 / iOS 26.0.1 + Workout Session Mirroring Failure
Hi, I have a workout app in the App Store which mirrors workout data between the phone and watch. Since iOS 26.x I've been having issues and received reports of the mirroring no longer working. Users in iOS 18 have no problems with this functionality. Bug description: A workout session is started from the phone app and starts mirroring to the watch companion device. The watch starts the workout session and then the mirroring session is disconnected / lost. Sending data to the companion device fails and ending the session on the phone doesn't end the session on the watch...essentially they become completely disconnected. Please note I am testing this on physical devices...not simulators. As a sanity check I've also tried the "Building a multidevice workout app" sample code and it has the same problem. To re-create on the sample app, I start a workout from the phone, the watch workout starts and then the mirroring session seems to disconnect and is unable to send data. This is the log from the "Building a multidevice workout app" sample code. Successfully started workout Type: Notice | Timestamp: 2025-10-17 06:57:07.341401+02:00 | Process: MirroringWorkoutsSample Watch App | Library: MirroringWorkoutsSample Watch App.debug.dylib | Subsystem: com.example.apple-samplecode.MirroringWorkoutsSampleABC123.watchkitapp | Category: MirroringWorkoutsSampleForWatch | TID: 0x1b2ca7 -[SPRemoteInterface _appRecoverAnyExtendedRuntimeSession:]_block_invoke:4350: Got no sessions back from -[CSLSSessionService existingRunningSessions:] or -[CSLSSessionService existingScheduledSessions:] after receiving a PUICInitializeSessionServiceAction Type: Error | Timestamp: 2025-10-17 06:57:07.641571+02:00 | Process: MirroringWorkoutsSample Watch App | Library: WatchKit | Subsystem: com.apple.watchkit | Category: default | TID: 0x1b2ca7 Session state changed from 1 to 2 Type: Notice | Timestamp: 2025-10-17 06:57:07.647883+02:00 | Process: MirroringWorkoutsSample Watch App | Library: MirroringWorkoutsSample Watch App.debug.dylib | Subsystem: com.example.apple-samplecode.MirroringWorkoutsSampleABC123.watchkitapp | Category: MirroringWorkoutsSampleForWatch | TID: 0x1b2e87 Failed to send data: Error Domain=com.apple.healthkit Code=100 "Failed to send data to remote session." UserInfo={NSLocalizedDescription=Failed to send data to remote session.} Type: Notice | Timestamp: 2025-10-17 06:57:07.669922+02:00 | Process: MirroringWorkoutsSample Watch App | Library: MirroringWorkoutsSample Watch App.debug.dylib | Subsystem: com.example.apple-samplecode.MirroringWorkoutsSampleABC123.watchkitapp | Category: MirroringWorkoutsSampleForWatch | TID: 0x1b2ca7 Would appreciate any help with this problem as it's affecting customers. Thank you
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Nov ’25
WorkoutKit WorkoutScheduler sync Broken with iOS 18.2 beta
WorkoutKit WorkoutScheduler seems broken with the first beta of iOS 18.2. I have tested using my app from Xcode and the one that is on the App Store (and working properly on other devices), and it's not working with this new beta of iOS. They appears in WorkoutScheduler.shared.scheduledWorkouts, but not on the watch. I even tried with other apps that do the same with Manual add to Apple Watch with SwiftUI workoutPreview work. Xcode 16.0 iOS 18.2 Beta 1 WatchOS 11.1
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2.0k
Oct ’25