This comes up over and over, here on the forums and elsewhere, so I thought I’d post my take on it. If you have questions or comments, start a new thread here on the forums. Put it in the App & System Services > Processes & Concurrency subtopic and tag it with Concurrency.
Share and Enjoy
—
Quinn “The Eskimo!” @ Developer Technical Support @ Apple
let myEmail = "eskimo" + "1" + "@" + "apple.com"
Waiting for an Async Result in a Synchronous Function
On Apple platforms there is no good way for a synchronous function to wait on the result of an asynchronous function.
Lemme say that again, with emphasis…
On Apple platforms there is no good way for a synchronous function to wait on the result of an asynchronous function.
This post dives into the details of this reality.
Prime Offender
Imagine you have an asynchronous function and you want to call it from a synchronous function:
func someAsynchronous(input: Int, completionHandler: @escaping @Sendable (_ output: Int) -> Void) {
… processes `input` asynchronously …
… when its done, calls the completion handler with the result …
}
func mySynchronous(input: Int) -> Int {
… calls `someAsynchronous(…)` …
… waits for it to finish …
… results the result …
}
There’s no good way to achieve this goal on Apple platforms. Every approach you might try has fundamental problems.
A common approach is to do this working using a Dispatch semaphore:
func mySynchronous(input: Int) -> Int {
fatalError("DO NOT WRITE CODE LIKE THIS")
let sem = DispatchSemaphore(value: 0)
var result: Int? = nil
someAsynchronous(input: input) { output in
result = output
sem.signal()
}
sem.wait()
return result!
}
Note This code produces a warning in the Swift 5 language mode which turns into an error in the Swift 6 language mode. You can suppress that warning with, say, a Mutex. I didn’t do that here because I’m focused on a more fundamental issue here.
This code works, up to a point. But it has unavoidable problems, ones that don’t show up in a basic test but can show up in the real world. The two biggest ones are:
Priority inversion
Thread pools
I’ll cover each in turn.
Priority Inversion
Apple platforms have a mechanism that helps to prevent priority inversion by boosting the priority of a thread if it holds a resource that’s needed by a higher-priority thread. The code above defeats that mechanism because there’s no way for the system to know that the threads running the work started by someAsynchronous(…) are being waited on by the thread blocked in mySynchronous(…). So if that blocked thread has a high-priority, the system can’t boost the priority of the threads doing the work.
This problem usually manifests in your app failing to meet real-time goals. An obvious example of this is scrolling. If you call mySynchronous(…) from the main thread, it might end up waiting longer than it should, resulting in noticeable hitches in the scrolling.
Threads Pools
A synchronous function, like mySynchronous(…) in the example above, can be called by any thread. If the thread is part of a thread pool, it consumes a valuable resource — that is, a thread from the pool — for a long period of time. The raises the possibility of thread exhaustion, that is, where the pool runs out of threads.
There are two common thread pools on Apple platforms:
Dispatch
Swift concurrency
These respond to this issue in different ways, both of which can cause you problems.
Dispatch can choose to over-commit, that is, start a new worker thread to get work done while you’re hogging its existing worker threads. This causes two problems:
It can lead to thread explosion, where Dispatch starts dozens and dozens of threads, which all end up blocked. This is a huge waste of resources, notably memory.
Dispatch has an hard limit to how many worker threads it will create. If you cause it to over-commit too much, you’ll eventually hit that limit, putting you in the thread exhaustion state.
In contrast, Swift concurrency’s thread pool doesn’t over-commit. It typically has one thread per CPU core. If you block one of those threads in code like mySynchronous(…), you limit its ability to get work done. If you do it too much, you end up in the thread exhaustion state.
WARNING Thread exhaustion may seem like just a performance problem, but that’s not the case. It’s possible for thread exhaustion to lead to a deadlock, which blocks all thread pool work in your process forever.
There’s a trade-off here. Swift concurrency doesn’t over-commit, so it can’t suffer from thread explosion but is more likely deadlock, and vice versa for Dispatch.
Bargaining
Code like the mySynchronous(…) function shown above is fundamentally problematic. I hope that the above has got you past the denial stage of this analysis. Now let’s discuss your bargaining options (-:
Most folks don’t set out to write code like mySynchronous(…). Rather, they’re working on an existing codebase and they get to a point where they have to synchronously wait for an asynchronous result. At that point they have the choice of writing code like this or doing a major refactor.
For example, imagine you’re calling mySynchronous(…) from the main thread in order to update a view. You could go down the problematic path, or you could refactor your code so that:
The current value is always available to the main thread.
The asynchronous code updates that value in an observable way.
The main thread code responds to that notification by updating the view from the current value.
This refactoring may or may not be feasible given your product’s current architecture and timeline. And if that’s the case, you might end up deploying code like mySynchronous(…). All engineering is about trade-offs. However, don’t fool yourself into thinking that this code is correct. Rather, make a note to revisit this choice in the future.
Async to Async
Finally, I want to clarify that the above is about synchronous functions. If you have a Swift async function, there is a good path forward. For example:
func mySwiftAsync(input: Int) async -> Int {
let result = await withCheckedContinuation { continuation in
someAsynchronous(input: input) { output in
continuation.resume(returning: output)
}
}
return result
}
This looks like it’s blocking the current thread waiting for the result, but that’s not what happens under the covers. Rather, the Swift concurrency worker thread that calls mySwiftAsync(…) will return to the thread pool at the await. Later, when someAsynchronous(…) calls the completion handler and you resume the continuation, Swift will grab a worker thread from the pool to continue running mySwiftAsync(…).
This is absolutely normal and doesn’t cause the sorts of problems you see with mySynchronous(…).
IMPORTANT To keep things simple I didn’t implement cancellation in mySwiftAsync(…). In a real product it’s important to support cancellation in code like this. See the withTaskCancellationHandler(operation:onCancel:isolation:) function for the details.
Processes & Concurrency
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Hi,
I am programming in C and would like to use Grand Central Dispatch for parallel computing (I mostly do physics based simulations). I remember there used to be example codes provided by Apple, but can't find those now. Instead I get the plain documentation. May anyone point me to the correct resources? It will be greatly appreciated. Thanks ☺.
I have several combine pipelines in my watch and iPhone app. While background tasks on the iPhone work correctly (the combine pipelines all activate), on the watch the pipelines do not get activated. I have an internal log reporting that data is being fed to the sources but is not propagating to the sinks.
Thoughts?
Topic:
App & System Services
SubTopic:
Processes & Concurrency
Tags:
watchOS
Combine
Background Tasks
Hello everyone,
I’m a new developer still learning as I go. I’m building a simple watchOS app that tracks Apple Watch battery consumption, records hourly usage data, and uses that information to predict battery life in hours.
I’ve run into an issue where background refresh completely stalls after charging and never recovers, regardless of what I do. The only way to restore normal behavior is to restart the watch.
Background refresh can work fine for days, but if the watch is charging and a scheduled background refresh tries to run during that period, it appears to be deferred—and then remains in that deferred state indefinitely. Even reopening the app or scheduling new refreshes doesn’t recover it.
Has anyone else encountered this behavior? Is there a reliable workaround?
I’ve seen a few reports suggesting that there may be a regression in scheduleBackgroundRefresh() on watchOS 26, where tasks are never delivered after certain states.
Any insights or confirmations would be greatly appreciated. Thank you!
First, our app communicates with our blood glucose monitor (CGM) using Bluetooth Low Energy (BLE).
On an iPhone 14 Pro with iOS 26.0.1, Bluetooth communication works properly even when the app is in the background and locked. Even if the phone and CGM are disconnected, the app continues to scan in the background and reconnects when the phone and CGM are back in close proximity. It won't be dormant in the background or when the screen is locked. This effectively ensures that diabetic users can monitor their blood glucose levels in real time.
However, after using iOS 26.0.1 on the iPhone 17, we've received user feedback about frequent disconnections in the background. Our logs indicate that Bluetooth communication is easily disconnected when switching to the background, and then easily dormant by the system, especially when the user's screen is locked. This situation significantly impacts users' blood glucose monitoring, and users are unacceptable. What can be done?
Topic:
App & System Services
SubTopic:
Processes & Concurrency
Tags:
IOBluetooth
Background Tasks
Core Bluetooth
When I use BGContinuedProcessingTask to submit a task, my iPhone 12 immediately shows a notification banner displaying the task’s progress.
However, on my iPhone 15 Pro Max, there’s no response — the progress UI only appears in the Dynamic Island after I background the app.
Why is there a difference in behavior between these two devices?
Is it possible to control the UI so that the progress indicator only appears when the app moves to the background?
Hello,
https://developer.apple.com/forums/thread/802443
https://developer.apple.com/documentation/servicemanagement/updating-helper-executables-from-earlier-versions-of-macos
https://developer.apple.com/documentation/ServiceManagement/updating-your-app-package-installer-to-use-the-new-service-management-api#Run-the-sample-launch-agent
Read these.
Earlier we had a setup with SMJobBless, now we have migrated to SMAppService.
Everything is working fine, the new API seems easier to manage, but we are having issues with updating the daemon.
I was wondering, what is the right process for updating a daemon from app side?
What we are doing so far:
App asks daemon for version
If version is lower than expected:
daemon.unregister(), wait a second and daemon.register() again.
The why?
We have noticed that unregistering/registering multiple times, of same daemon, can cause the daemon to stop working as expected. The daemon toggle in Mac Settings -> Login Items & Extensions can be on or off, but the app can still pickup daemon running, but no daemon running in Activity monitor. Registration/unregistration can start failing and nothing helps to resolve this, only reseting with sfltool resetbtm and a restart seems to does the job. This is usually noticeable for test users, testing same daemon version with different app builds.
In production app, we also increase the bundle version of daemon in plist, in test apps we - don't.
I haven't found any sources of how the update of pre-bundled app daemon should work.
Initial idea is register/unregister, but from what I have observed, this seems to mess up after multiple registrations.
I have a theory, that sending the daemon a command to kill itself after app update, would load the latest daemon.
Also, I haven't observed for daemon, with different build versions to update automatically.
What is the right way to update a daemon with SMAppService setup?
Thank you in advance.
Hi,
This post is coming from frustration of working on using BGContinuedProcessingTask for almost 2 weeks, trying to get it to actually complete in the background after the app is backgrounded.
My process will randomlly finish and not finish and have no idea why.
I'm properly using and setting
task?.progress.totalUnitCount = [some number]
task?.progress.completedUnitCount = [increment as processed]
I know this, because it all looks propler as long as the app insn't backgrounded. So it's not a progress issue. The task will ALWAYS complete.
The device has full power, as it is plugged in as I run from within Xcode. So, it's not a power issue.
Yes, the process will take a few minutes, but I thought that is BGContinuedProcessingTask purpose in iOS 26. For long running process that a user could place in the background and leave the app, assuming the process would actually finish.
Why bother introducing a feature that only works with short tasks that don't actually need long running time in the first place.
TCC Permission Inheritance for Python Process Launched by Swift App in Enterprise Deployment
We are developing an enterprise monitoring application that requires a hybrid Swift + Python architecture due to strict JAMF deployment restrictions. We must deploy a macOS application via ABM/App Store Connect, but our core monitoring logic is in a Python daemon. We need to understand the feasibility and best practices for TCC permission inheritance in this specific setup.
Architecture
Component
Bundle ID
Role
Deployment
Swift Launcher
com.athena.AthenaSentry
Requests TCC permissions, launches Python child process.
Deployed via ABM/ASC.
Python Daemon
com.athena.AthenaSentry.Helper
Core monitoring logic using sensitive APIs.
Nested in Contents/Helpers/.
Both bundles are signed with the same Developer ID and share the same Team ID.
Required Permissions
The Python daemon needs to access the following sensitive TCC-controlled services:
Screen Recording (kTCCServiceScreenCapture) - for capturing screenshots.
Input Monitoring (kTCCServiceListenEvent) - for keystroke/mouse monitoring.
Accessibility (kTCCServiceAccessibility) - a prerequisite for Input Monitoring.
Attempts & Workarounds
We have attempted to resolve this using:
Entitlement Inheritance: Added com.apple.security.inherit to the Helper's entitlements.
Permission Proxy: Swift app maintains active event taps to try and "hold" the permissions for the child.
Foreground Flow: Keeping the Swift app in the foreground during permission requests.
Questions
Is this architecture supported? Can a Swift parent app successfully request TCC permissions that a child process can then use?
TCC Inheritance: What are the specific rules for TCC permission inheritance between parent/child processes in enterprise environment?
What's the correct approach for this enterprise use case? Should we:
Switch to a Single Swift App? (i.e., abandon the Python daemon and rewrite the core logic natively in Swift).
Use XPC Services? (instead of launching the child process directly).
Topic:
App & System Services
SubTopic:
Processes & Concurrency
Tags:
Enterprise
Entitlements
Privacy
Scripting
I've adopted the new BGContinuedProcessingTask in iOS 26, and it has mostly been working well in internal testing. However, in production I'm getting reports of the tasks failing when the app is put into the background.
A bit of info on what I'm doing: I need to download a large amount of data (around 250 files) and process these files as they come down. The size of the files can vary: for some tasks each file might be around 10MB. For other tasks, the files might be 40MB. The processing is relatively lightweight, but the volume of data means the task can potentially take over an hour on slower internet connections (up to 10GB of data).
I set the totalUnitCount based on the number of files to be downloaded, and I increment completedUnitCount each time a file is completed.
After some experimentation, I've found that smaller tasks (e.g. 3GB, 10MB per file) seem to be okay, but larger tasks (e.g. 10GB, 40MB per file) seem to fail, usually just a few seconds after the task is backgrounded (and without even opening any other apps). I think I've even observed a case where the task expired while the app was foregrounded!
I'm trying to understand what the rules are with BGContinuedProcessingTask and I can see at least four possibilities that might be relevant:
Is it necessary to provide progress updates at some minimum rate? For my larger tasks, where each file is ~40MB, there might be 20 or 30 seconds between progress updates. Does this make it more likely that the task will be expired?
For larger tasks, the total time to complete can be 60–90 mins on slower internet connections. Is there some maximum amount of time the task can run for? Does the system attempt some kind of estimate of the overall time to complete and expire the task on that basis?
The processing on each file is relatively lightweight, so most of the time the async stream is awaiting the next file to come down. Does the OS monitor the intensity of workload and suspend the task if it appears to be idle?
I've noticed that the task UI sometimes displays a message, something along the lines of "Do you want to continue this task?" with a "Continue" and "Stop" option. What happens if the user simply ignores or doesn't see this message? Even if I tap "Continue" the task still seems to fail sometimes.
I've read the docs and watched the WWDC video, but there's not a whole lot of information on the specific issues I mention above. It would be great to get some clarity on this, and I'd also appreciate any advice on alternative ways I could approach my specific use case.
I would like to know whether BGContinuedProcessingTaskRequest supports executing asynchronous tasks internally, or if it can only execute synchronous tasks within BGContinuedProcessingTaskRequest?
Our project is very complex, and we now need to use BGContinuedProcessingTaskRequest to perform some long-running operations when the app enters the background (such as video encoding/decoding & export). However, our export interface is an asynchronous function, for example video.export(callback: FinishCallback). This export call returns immediately, and when the export completes internally, it calls back through the passed-in callback. So when I call BGTaskScheduler.shared.register to register a BGContinuedProcessingTask, what should be the correct approach? Should I directly call video.export(nil) without any waiting, or should I wait for the export function to complete in the callback?
For example:
BGTaskScheduler.shared.register(forTaskWithIdentifier: "com.xxx.xxx.xxx.xxx", using: nil) { task in
guard let continuedTask = task as? BGContinuedProcessingTask else {
task.setTaskCompleted(success: false)
return
}
let scanner = SmartAssetsManager.shared
let semaphore = DispatchSemaphore(value: 0)
continuedTask.expirationHandler = {
logError(items: "xwxdebug finished.")
semaphore.signal()
}
logInfo(items: "xwxdebug start!")
video.export { _ in
semaphore.signal()
}
semaphore.wait()
logError(items: "xwxdebug finished!")
}
If I create a BGContinuedProcessingTaskRequest, register it, and then "do work" within it appropriately reporting progress, and before my task has finished doing all the work it had to do, its expirationHandler triggers...
does the task later try again?
Or does it lose the execution opportunity until the app is next re-launched to the foreground?
In my testing, I never saw my task execute again once expired (which suggests the latter?).
I was able to easily force this expiry by starting my task, backgrounding my app, then launching the iOS Camera App. My example is just using test code inspired from https://developer.apple.com/documentation/backgroundtasks/performing-long-running-tasks-on-ios-and-ipados
let request = BGContinuedProcessingTaskRequest(identifier: taskIdentifier, title: "Video Upload", subtitle: "Starting Upload")
request.strategy = .queue
BGTaskScheduler.shared.register(forTaskWithIdentifier: taskIdentifier, using: nil) { task in
guard let task = task as? BGContinuedProcessingTask else { return }
print("i am a good task")
var wasExpired = false
task.expirationHandler = {
wasExpired = true
}
let progress = task.progress
progress.totalUnitCount = 100
while !progress.isFinished && !wasExpired {
progress.completedUnitCount += 1
let formattedProgress = String(format: "%.2f", progress.fractionCompleted * 100)
task.updateTitle(task.title, subtitle: "Completed \(formattedProgress)%")
sleep(1)
}
if progress.isFinished {
print ("i was a good task")
task.setTaskCompleted(success: true)
} else {
print("i was not a good task")
task.setTaskCompleted(success: false)
}
}
try? BGTaskScheduler.shared.submit(request)
Apologies if this is clearly stated somewhere and I'm missing it.
I implemented BGContinuedProcessingTask in my app and it seems to be working well for everyone except one user (so far) who has reached out to report nothing happens when they tap the Start Processing button. They have an iPhone 12 Pro Max running iOS 26.1. Restarting iPhone does not fix it.
When they turn off the background processing feature in the app, it works. In that case my code directly calls the function to start processing instead of waiting for it to be invoked in the register block (or submit catch block).
Is this a bug that's possible to occur, maybe device specific? Or have I done something wrong in the implementation?
func startProcessingTapped(_ sender: UIButton) {
if isBackgroundProcessingEnabled {
startBackgroundContinuedProcessing()
} else {
startProcessing(backgroundTask: nil)
}
}
func startBackgroundContinuedProcessing() {
BGTaskScheduler.shared.register(forTaskWithIdentifier: taskIdentifier, using: .main) { @Sendable [weak self] task in
guard self != nil else { return }
startProcessing(backgroundTask: task as? BGContinuedProcessingTask)
}
let request = BGContinuedProcessingTaskRequest(identifier: taskIdentifier, title: title, subtitle: subtitle)
request.strategy = .fail
if BGTaskScheduler.supportedResources.contains(.gpu) {
request.requiredResources = .gpu
}
do {
try BGTaskScheduler.shared.submit(request)
} catch {
startProcessing(backgroundTask: nil)
}
}
func startProcessing(backgroundTask: BGContinuedProcessingTask?) {
// FIXME: Never called for this user when isBackgroundProcessingEnabled is true
}
The same code built in a regular Mac app (with UI) does get paired.
The characteristic properties are [.read, .write, .notify, .notifyEncryptionRequired]
The characteristic permissions are [.readEncryptionRequired, .writeEncryptionRequired]
My service is primary.
In the iOS app (central) I try to read the characteristic, but an error is reported: Error code: 5, Description: Authentication is insufficient.
Topic:
App & System Services
SubTopic:
Processes & Concurrency
Tags:
Service Management
Core Bluetooth
We're developing an Electron app for MacOS App Store. When updating our app through TestFlight, TestFlight prompts "Close This App to Update", and when I click "Continue" our app would be "Terminated" for update.
Now this is where things go wrong. On MacOS 15 our app seems to be gracefully terminating (We attached it with lldb and it shows that our app returns with 0 when we click "Continue") which is fine.
However for MacOS 26 though, it seems that TestFlight just directly SIGKILLs our app (indicated by lldb), which means that all of our app's child processes are left orphaned. Even worse, our app is singleton, which means that when the app relaunches it fails, because the leftover child processes from the previously SIGKILLed session is still alive, and even if we want to kill those orphaned child processes we can't because our app is sandboxed thus cannot kill processes outside of the current sandbox.
We captured output from log stream (app name redacted):
12-02 22:08:16.477036-0800 0x5452 Default 0x5a4a7 677 7 installcoordinationd: [com.apple.installcoordination:daemon] -[IXSCoordinatorProgress setTotalUnitsCompleted:]: Progress for coordinator: [com.our.app/Invalid/[user-defined//Applications/OurApp.app]], Phase: IXCoordinatorProgressPhaseLoading, Percentage: 99.454 123: Attempt to set units completed on finished progress: 214095161 2025-12-02 22:08:16.483056-0800 0x53ba Default 0x5a5c9 167 0 runningboardd: (RunningBoard) [com.apple.runningboard:connection] Received termination request from [osservice<com.apple.installcoordinationd(274)>:677] on <RBSProcessPredicate <RBSProcessBundleIdentifierPredicate "com.our.app">> with context <RBSTerminateContext| explanation:installcoordinationd app:[com.our.app/Invalid/[user-defined//Applications/OurApp.app]] uuid:A3BC0629-124E-4165-ABB7-1324380FC354 isPlaceholder:N re portType:None maxTerminationResistance:Absolute attrs:[ 2025-12-02 22:08:16.488651-0800 0x53ba Default 0x5a5c9 167 7 runningboardd: (RunningBoard) [com.apple.runningboard:ttl] Acquiring assertion targeting system from originator [osservice<com.apple.installcoordinationd(274)>:677] with description <RBSAssertionDescriptor| "installcoordinationd app:[com.our.app/Invalid/[user-defined//Applications/OurApp.app]] uuid:A3BC0629-124E-4165-ABB7-1324380FC354 isPlaceholder:N" ID:167-677-1463 target:system attributes:[ 2025-12-02 22:08:16.489353-0800 0x53ba Default 0x5a5c9 167 0 runningboardd: (RunningBoard) [com.apple.runningboard:process] [app<application.com.our.app.485547.485561(501)>:2470] Terminating with context: <RBSTerminateContext| explanation:installcoordinationd app:[com.our.app/Invalid/[user-defined//Applications/OurApp.app]] uuid:A3BC0629-124E-4165-ABB7-1324380FC354 isPlaceholder:N reportType:None maxTerminationResistance:Absolute attrs:[ 2025-12-02 22:10:23.920869-0800 0x5a5a Default 0x5a4c6 674 14 appstoreagent: [com.apple.appstored:Library] [A95D57D7] Completed with 1 result: <ASDApp: 0xc932a8780>: {bundleID = com.our.app; completedUnitCount = 600; path = /Applications/OurApp.app; installed = 0} 2025-12-02 22:10:32.027304-0800 0x5ae5 Default 0x5a4c7 674 14 appstoreagent: [com.apple.appstored:Library] [BEB5F2FD] Completed with 1 result: <ASDApp: 0xc932a8780>: {bundleID = com.our.app; completedUnitCount = 600; path = /Applications/OurApp.app; installed = 0} 2025-12-02 22:10:36.542321-0800 0x5b81 Default 0x5a4c8 674 14 appstoreagent: [com.apple.appstored:Library] [185B9DD6] Completed with 1 result: <ASDApp: 0xc932a8780>: {bundleID = com.our.app; completedUnitCount = 600; path = /Applications/OurApp.app; installed = 0}
The line "Terminating with context" seems suspicious. This line is not seen on MacOS 15, only MacOS 26. Is this documented behavior? If so, how can we handle this?
Topic:
App & System Services
SubTopic:
Processes & Concurrency
Tags:
App Store
Mac App Store
TestFlight
Hi All,
In continuation of this thread https://developer.apple.com/forums/thread/804439
I want to perform data upload after getting it from the BLE device. As state restoration wake should not deal with data upload i though of using a processing task to perform the data upload.
So the flow will be something like:
Connect to device -> listen to notification -> go to background -> wake from notification -> handle data download from ble device -> register processing task for data upload -> hopefully get the data uploaded
From reading about processing task i understand that the task execution is completely handled by the OS and depends on user behaviour and app usage. I even saw that if the user is not using the app for a while, the OS might not even perfoirm the task. So my quesiton is: does state restoration wakeup and perfroming data dowloads in the backgound considered app usage that will increase the likeluhood the task will get execution time?
Can we rely on this for a scenario that the user opens the app for the first time, register, onboard for ble, connect to devie and then put it in the background for days or weeks and only relying on state restoration and processing tasks to do their thing?
Sorry for the long read and appreciate your support!
Shimon
Topic:
App & System Services
SubTopic:
Processes & Concurrency
Tags:
Background Tasks
Core Bluetooth
I'm making an operator Publisher, which has to wrap the upstream publisher. But I want the operator to conditionally conform to ConnectablePublisher, but only when the upstream publisher does the same.
I can make my connect() call the upstream's connect(), but is that all I have to do? That Apple's plumbing will automatically hold back the initial call to the Subscription object if the publisher is connectable. Otherwise, I need to make a flag in the subscription for when to connect, which would involve an infinitely copyable struct somehow send a message to a unique class/actor.
That last part makes sense to me, but it also seems like too much work for something plug-and-play. Having Apple's implementation taking care of that issue also makes sense, and would be a better solution.
I built an iOS app and debugged it using my iPhone 11. It works fine. My app uses Bluetooth because the physical data logger reads data via Bluetooth. I published it to the Apple store. After installing it on the iPhone 13 pro. The app works, but the device is not selected.
I’m reaching out regarding an issue we’ve been experiencing with BGProcessingTask since upgrading to Xcode 26.1.1.
Issue Summary
Our daily background processing task—scheduled shortly after end‑of‑day—has stopped triggering reliably at night. This behavior started occurring only after updating to Xcode 26.1.1. Prior to this update, the task consistently ran around midnight, executed for ~10–15 seconds, and successfully rescheduled itself for the next day.
Expected Behavior
BGProcessingTask should run at/near the scheduled earliestBeginDate, which we set to roughly 2 hours after end-of-day.
The task should execute, complete, and then reschedule itself.
Actual Behavior
On devices running builds compiled with Xcode 26.1.1, the task does not trigger at all during the night.
The same code worked reliably before the Xcode update.
No system logs indicate rejection, expiration, or background task denial.
Technical Details
This is the identifier we use:
private enum DayEndProcessorConst {
static let taskIdentifier = "com.company.sdkmanagement.daysummary.manager"
}
The task is registered as follows: When app launched
BGTaskScheduler.shared.register(
forTaskWithIdentifier: DayEndProcessorConst.taskIdentifier,
using: nil
) { [weak self] task in
self?.handleDayEndTask(task)
}
And scheduled like this:
let date = Calendar.current.endOfDay(for: Date()).addingTimeInterval(60 * 60 * 2)
let request = BGProcessingTaskRequest(identifier: DayEndProcessorConst.taskIdentifier)
request.requiresNetworkConnectivity = true
request.requiresExternalPower = false
request.earliestBeginDate = date
try BGTaskScheduler.shared.submit(request)
As per our logs, tasks scheduled successfully
The handler wraps the work in an operation queue, begins a UI background task, and marks completion appropriately:
task.setTaskCompleted(success: true)
Could you please advise whether:
There are known issues with BGProcessingTask scheduling or midnight execution in Xcode 26.1.1 or iOS versions associated with it?
Any new entitlement, configuration, or scheduler behavior has changed in recent releases?
Additional logging or diagnostics can help pinpoint why the scheduler never fires the task?
Our app will launch automatically in the background,Doubt is the result of background fetch ,so we cancel the background modes setting of the background fetch,but we still can see the performFetchWithCompletionHandler method called when app launch in the background。Background launch will cause some bugs in our app. We don't want the app to start in the background. We hope to get help