Processes & Concurrency

RSS for tag

Discover how the operating system manages multiple applications and processes simultaneously, ensuring smooth multitasking performance.

Concurrency Documentation

Posts under Processes & Concurrency subtopic

Post

Replies

Boosts

Views

Activity

Combine delay & switchToLatest publisher don't emit value sometimes
Hello, I recently implemented a conditional debounce publisher using Swift's Combine. If a string with a length less than 2 is passed, the event is sent downstream immediately without delay. If a string with a length of 2 or more is passed, the event is emitted downstream with a 0.2-second delay. While writing test logic related to this, I noticed a strange phenomenon: sometimes the publisher, which should emit events with a 0.2-second delay, does not emit an event. The test code below should have all indices from 1 to 100 in the array, but sometimes some indices are missing, causing the assertion to fail. Even after observing completion, cancel, and output events through handleEvents, I couldn't find any cause. Am I using Combine incorrectly, or is there a bug in Combine? I would appreciate it if you could let me know. import Foundation import Combine var cancellables: Set<AnyCancellable> = [] @MainActor func text(index: Int, completion: @escaping () -> Void) { let subject = PassthroughSubject<String, Never>() let textToSent = "textToSent" subject .map { text in if text.count >= 2 { return Just<String>(text) .delay(for: .seconds(0.2), scheduler: RunLoop.main) .eraseToAnyPublisher() } else { return Just<String>(text) .eraseToAnyPublisher() } } .switchToLatest() .sink { if $0.count >= 2 { completion() } }.store(in: &cancellables) for i in 0..<textToSent.count { let stringIndex = textToSent.index(textToSent.startIndex, offsetBy: i) let stringToSent = String(textToSent[textToSent.startIndex...stringIndex]) subject.send(stringToSent) } } var array = [Int]() for i in 1...100 { text(index: i) { array.append(i) } } DispatchQueue.main.asyncAfter(deadline: .now() + 5) { for i in 1...100 { assert(array.contains(i)) } } RunLoop.main.run(until: .now + 10)
0
0
400
Feb ’25
Getting Started with SMAppService
I was stuck on a long train journey this weekend, so I thought I’d use that time to write up the process for installing a launchd daemon using SMAppService. This involves a number of deliberate steps and, while the overall process isn’t too hard — it’s certainly a lot better than with the older SMJobBless — it’s easy to accidentally stray from the path and get very confused. If you have questions or comments, start a new thread in the App & System Services > Processes & Concurrency subtopic and tag it with Service Management. Share and Enjoy — Quinn “The Eskimo!” @ Developer Technical Support @ Apple let myEmail = "eskimo" + "1" + "@" + "apple.com" Getting Started with SMAppService This post explains how to use SMAppService to install a launchd daemon. I tested these instructions using Xcode 26.0 on macOS 15.6.1. Things are likely to be slightly different with different Xcode and macOS versions. Create the container app target To start, I created a new project: I choose File > New > Project. In the template picker, I chose macOS > App. In options page, I set the Product Name field to SMAppServiceTest [1]. And I selected my team in the Team popup. And I verified that the Organization Identifier was set to com.example.apple-samplecode, the standard for Apple sample code [1]. I selected SwiftUI in the Interface popup. There’s no requirement to use SwiftUI here; I chose it because that’s what I generally use these days. And None in the Testing System popup. And None in the Storage popup. I then completed the new project workflow. I configured basic settings on the project: In the Project navigator, I selected the SMAppServiceTest project. In the Project editor, I selected the SMAppServiceTest target. At the top I selected Signing & Capabilities. In the Signing section, I made sure that “Automatically manage signing” was checked. And that my team was selected in the Team popup. And that the bundle ID of the app ended up as com.example.apple-samplecode.SMAppServiceTest. Still in the Signing & Capabilities tab, I removed the App Sandbox section. Note It’s possible to use SMAppService to install a daemon from a sandboxed app, but in that case the daemon also has to be sandboxed. That complicates things, so I’m disabling the sandbox for the moment. See Enable App Sandbox, below, for more on this. Next I tweaked some settings to make it easier to keep track of which target is which: At the top, I selected the Build Settings tab. I changed the Product Name build setting from $(TARGET_NAME) to SMAppServiceTest. On the left, I renamed the target to App. I chose Product > Scheme > Manage Schemes. In the resulting sheet, I renamed the scheme from SMAppServiceTest to App, just to keep things in sync. [1] You are free to choose your own value, of course. However, those values affect other values later in the process, so I’m giving the specific values I used so that you can see how everything lines up. Create the daemon target I then created a daemon target: I chose File > New > Target. In the template picker, I chose macOS > Command Line Tool. In the options page, I set the Product Name field to Daemon. And I selected my team in the Team popup. And I verified that the Organization Identifier was set to com.example.apple-samplecode, the standard for Apple sample code. I selected Swift in the Language popup. And verified that SMAppServiceTest was set in the Project popup. I clicked Finish. I configured basic settings on the target: In the Project navigator, I selected the SMAppServiceTest project. In the Project editor, I selected the Daemon target. At the top I selected Signing & Capabilities. In the Signing section, I made sure that “Automatically manage signing” was checked. And that my team was selected in the Team popup. Note The Bundle Identifier field is blank, and that’s fine. There are cases where you want to give a daemon a bundle identifier, but it’s not necessary in this case. Next I tweaked some settings to make it easier to keep track of which target is which: At the top, I selected the Build Settings tab. I changed the Product Name build setting from $(TARGET_NAME) to SMAppServiceTest-Daemon. I forced the Enable Debug Dylib Support to No. IMPORTANT To set it to No, you first have to set it to Yes and then set it back to No. I edited Daemon/swift.swift to look like this: import Foundation import os.log let log = Logger(subsystem: "com.example.apple-samplecode.SMAppServiceTest", category: "daemon") func main() { log.log("Hello Cruel World!") dispatchMain() } main() This just logs a ‘first light’ log message and parks [1] the main thread in dispatchMain(). Note For more about first light log points, see Debugging a Network Extension Provider. [1] Technically the main thread terminates in this case, but I say “parks” because that’s easier to understand (-: Test the daemon executable I selected the Daemon scheme and chose Product > Run. The program ran, logging its first light log entry, and then started waiting indefinitely. Note Weirdly, in some cases the first time I ran the program I couldn’t see its log output. I had to stop and re-run it. I’m not sure what that’s about. I chose Product > Stop to stop it. I then switched back the App scheme. Embed the daemon in the app I added a build phase to embed the daemon executable into app: In the Project navigator, I selected the SMAppServiceTest project. In the Project editor, I selected the App target. At the top I selected Build Phases. I added a new copy files build phase. I renamed it to Embed Helper Tools. I set its Destination popup to Executables. I clicked the add (+) button under the list and selected SMAppServiceTest-Daemon. I made sure that Code Sign on Copy was checked for that. I then created a launchd property list file for the daemon: In the Project navigator, I selected SMAppServiceTestApp.swift. I chose Product > New > File from Template. I selected the Property List template. In the save sheet, I named the file com.example.apple-samplecode.SMAppServiceTest-Daemon.plist. And made sure that the Group popup was set to SMAppServiceTest. And that only the App target was checked in the Targets list. I clicked Create to create the file. In the property list editor, I added two properties: Label, with a string value of com.example.apple-samplecode.SMAppServiceTest-Daemon BundleProgram, with a string value of Contents/MacOS/SMAppServiceTest-Daemon I added a build phase to copy that property list into app: In the Project navigator, I selected the SMAppServiceTest project. In the Project editor, I selected the App target. At the top I selected Build Phases. I added a new copy files build phase. I renamed it to Copy LaunchDaemons Property Lists. I set its Destination popup to Wrapper. And set the Subpath field to Contents/Library/LaunchDaemons. I disclosed the contents of the Copy Bundle Resources build phase. I dragged com.example.apple-samplecode.SMAppServiceTest-Daemon.plist from the Copy Bundle Resources build phase to the new Copy LaunchDaemons Property Lists build phase. I made sure that Code Sign on Copy was unchecked. Register and unregister the daemon In the Project navigator, I selected ContentView.swift and added the following to the imports section: import os.log import ServiceManagement I then added this global variable: let log = Logger(subsystem: "com.example.apple-samplecode.SMAppServiceTest", category: "app") Finally, I added this code to the VStack: Button("Register") { do { log.log("will register") let service = SMAppService.daemon(plistName: "com.example.apple-samplecode.SMAppServiceTest-Daemon.plist") try service.register() log.log("did register") } catch let error as NSError { log.log("did not register, \(error.domain, privacy: .public) / \(error.code)") } } Button("Unregister") { do { log.log("will unregister") let service = SMAppService.daemon(plistName: "com.example.apple-samplecode.SMAppServiceTest-Daemon.plist") try service.unregister() log.log("did unregister") } catch let error as NSError { log.log("did not unregister, \(error.domain, privacy: .public) / \(error.code)") } } IMPORTANT None of this is code is structured as I would structure a real app. Rather, this is the absolutely minimal code needed to demonstrate this API. Check the app structure I chose Product > Build and verified that everything built OK. I then verified that the app’s was structured correctly: I then choose Product > Show Build Folder in Finder. I opened a Terminal window for that folder. In Terminal, I changed into the Products/Debug directory and dumped the structure of the app: % cd "Products/Debug" % find "SMAppServiceTest.app" SMAppServiceTest.app SMAppServiceTest.app/Contents SMAppServiceTest.app/Contents/_CodeSignature SMAppServiceTest.app/Contents/_CodeSignature/CodeResources SMAppServiceTest.app/Contents/MacOS SMAppServiceTest.app/Contents/MacOS/SMAppServiceTest.debug.dylib SMAppServiceTest.app/Contents/MacOS/SMAppServiceTest SMAppServiceTest.app/Contents/MacOS/__preview.dylib SMAppServiceTest.app/Contents/MacOS/SMAppServiceTest-Daemon SMAppServiceTest.app/Contents/Resources SMAppServiceTest.app/Contents/Library SMAppServiceTest.app/Contents/Library/LaunchDaemons SMAppServiceTest.app/Contents/Library/LaunchDaemons/com.example.apple-samplecode.SMAppServiceTest-Daemon.plist SMAppServiceTest.app/Contents/Info.plist SMAppServiceTest.app/Contents/PkgInfo There are a few things to note here: The com.example.apple-samplecode.SMAppServiceTest-Daemon.plist property list is in Contents/Library/LaunchDaemons. The daemon executable is at Contents/MacOS/SMAppServiceTest-Daemon. The app is still built as debug dynamic library (SMAppServiceTest.debug.dylib) but the daemon is not. Test registration I chose Product > Run. In the app I clicked the Register button. The program logged: will register did not register, SMAppServiceErrorDomain / 1 Error 1 indicates that installing a daemon hasn’t been approved by the user. The system also presented a notification: Background Items Added “SMAppServiceTest” added items that can run in the background for all users. Do you want to allow this? Options > Allow > Don’t Allow I chose Allow and authenticated the configuration change. In Terminal, I verified that the launchd daemon was loaded: % sudo launchctl list com.example.apple-samplecode.SMAppServiceTest-Daemon { "LimitLoadToSessionType" = "System"; "Label" = "com.example.apple-samplecode.SMAppServiceTest-Daemon"; "OnDemand" = true; "LastExitStatus" = 0; "Program" = "Contents/MacOS/SMAppServiceTest-Daemon"; }; IMPORTANT Use sudo to target the global launchd context. If you omit this you end up targeting the launchd context in which Terminal is running, a GUI login context, and you won't find any launchd daemons there. I started monitoring the system log: I launched the Console app. I pasted subsystem:com.example.apple-samplecode.SMAppServiceTest into the search box. I clicked “Start streaming”. Back in Terminal, I started the daemon: % sudo launchctl start com.example.apple-samplecode.SMAppServiceTest-Daemon In Console, I saw it log its first light log point: type: default time: 17:42:20.626447+0100 process: SMAppServiceTest-Daemon subsystem: com.example.apple-samplecode.SMAppServiceTest category: daemon message: Hello Cruel World! Note I’m starting the daemon manually because my goal here is to show how to use SMAppService, not how to use XPC to talk to a daemon. For general advice about XPC, see XPC Resources. Clean up Back in the app, I clicked Unregister. The program logged: will unregister did unregister In Terminal, I confirmed that the launchd daemon was unloaded: % sudo launchctl list com.example.apple-samplecode.SMAppServiceTest-Daemon Could not find service "com.example.apple-samplecode.SMAppServiceTest-Daemon" in domain for system Note This doesn’t clean up completely. The system remembers your response to the Background Items Added notification, so the next time you run the app and register your daemon it will be immediately available. To reset that state, run the sfltool with the resetbtm subcommand. Install an Agent Rather Than a Daemon The above process shows how to install a launchd daemon. Tweaking this to install a launchd agent is easy. There are only two required changes: In the Copy Launch Daemon Plists copy files build phase, set the Subpath field to Contents/Library/LaunchAgents. In ContentView.swift, change the two SMAppService.daemon(plistName:) calls to SMAppService.agent(plistName:). There are a bunch of other changes you should make, like renaming everything from daemon to agent, but those aren’t required to get your agent working. Enable App Sandbox In some cases you might want to sandbox the launchd job (the term job to refer to either a daemon or an agent.) This most commonly crops up with App Store apps, where the app itself must be sandboxed. If the app wants to install a launchd agent, that agent must also be sandboxed. However, there are actually four combinations, of which three are supported: App Sandboxed | Job Sandboxed | Supported ------------- | ------------- | --------- no | no | yes no | yes | yes yes | no | no [1] yes | yes | yes There are also two ways to sandbox the job: Continue to use a macOS > Command Line Tool target for the launchd job. Use an macOS > App target for the launchd job. In the first approach you have to use some low-level build settings to enable the App Sandbox. Specifically, you must assign the program a bundle ID and then embed an Info.plist into the executable via the Create Info.plist Section in Binary build setting. In the second approach you can use the standard Signing & Capabilities editor to give the job a bundle ID and enable the App Sandbox, but you have to adjust the BundleProgram property to account for the app-like wrapper. IMPORTANT The second approach is required if your launchd job uses restricted entitlements, that is, entitlements that must be authorised by a provisioning profile. In that case you need an app-like wrapper to give you a place to store the provisioning profile. For more on this idea, see Signing a daemon with a restricted entitlement. For more background on how provisioning profiles authorise the use of entitlements, see TN3125 Inside Code Signing: Provisioning Profiles. On balance, the second approach is the probably the best option for most developers. [1] When SMAppService was introduced it was possible to install a non-sandboxed daemon from a sandboxed app. That option is blocked by macOS 14.2 and later.
0
0
183
Sep ’25
Background Task Scheduler
Hello, An application I am working on would like to schedule push notifications for a medication reminder app. I am trying to use BGTaskScheduler to wake up periodically and submit the notifications based on the user's medication schedule. I set up the task registration in my AppDelegate's didFinishLaunchingWithOptions method: BGTaskScheduler.shared.register( forTaskWithIdentifier: backgroundTaskIdentifier, using: nil) { task in self.scheduleNotifications() task.setTaskCompleted(success: true) self.scheduleAppRefresh() } scheduleAppRefresh() I then schedule the task using: func scheduleAppRefresh() { let request = BGAppRefreshTaskRequest(identifier: backgroundTaskIdentifier) request.earliestBeginDate = Date(timeIntervalSinceNow: 60 * 1) do { try BGTaskScheduler.shared.submit(request) } catch { } } In my testing, I can see the background task getting called once, but if I do not launch the application during the day. The background task does not get called the next day. Is there something else I need to add to get repeated calls from the BGTaskScheduler? Thank You, JR
2
0
146
Oct ’25
Waiting for an Async Result in a Synchronous Function
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.
0
0
781
Oct ’25
How to view documentation and example codes for Grand Central Dispatch for C
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 ☺.
2
0
127
Oct ’25
Possible to allow x code builds to run background processes for over 3 minutes
I have an app that I'm using for my own purposes and is not in the app store. I would like to run an http server in the background for more than the allotted 3 minutes to allow persistent communications with a connected Bluetooth device. The Bluetooth device would poll the service at intervals. Is this possible to do? This app does not need app store approval since it's only for personal use.
2
0
367
Feb ’25
NSFileCoordinator Swift Concurrency
I'm working on implementing file moving with NSFileCoordinator. I'm using the slightly newer asynchronous API with the NSFileAccessIntents. My question is, how do I go about notifying the coordinator about the item move? Should I simply create a new instance in the asynchronous block? Or does it need to be the same coordinator instance? let writeQueue = OperationQueue() public func saveAndMove(data: String, to newURL: URL) { let oldURL = presentedItemURL! let sourceIntent = NSFileAccessIntent.writingIntent(with: oldURL, options: .forMoving) let destinationIntent = NSFileAccessIntent.writingIntent(with: newURL, options: .forReplacing) let coordinator = NSFileCoordinator() coordinator.coordinate(with: [sourceIntent, destinationIntent], queue: writeQueue) { error in if let error { return } do { // ERROR: Can't access NSFileCoordinator because it is not Sendable (Swift 6) coordinator.item(at: oldURL, willMoveTo: newURL) try FileManager.default.moveItem(at: oldURL, to: newURL) coordinator.item(at: oldURL, didMoveTo: newURL) } catch { print("Failed to move to \(newURL)") } } }
0
0
100
Apr ’25
Background Refresh Stalls After Charging on watchOS 26
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!
1
0
176
Oct ’25
Background Assets Extension and DeviceCheck
Hi, I have some questions regarding the Background Assets Extension and DeviceCheck framework. Goal: Ensure that only users who have purchased the app can access the server's API without any user authentication using for example DeviceCheck framework and within a Background Assets Extension. My app relies on external assets, which I'm loading using the Background Assets Extension. I'm trying to determine if it's possible to obtain a challenge from the server and send a DeviceCheck assertion during this process within the Background Assets Extension. So far, I only receive session-wide authentication challenges—specifically NSURLAuthenticationMethodServerTrust in the Background Assets Extensio. I’ve tested with Basic Auth (NSURLAuthenticationMethodHTTPBasic) just for experimentation, but the delegate func backgroundDownload( _ download: BADownload, didReceive challenge: URLAuthenticationChallenge ) async -> (URLSession.AuthChallengeDisposition, URLCredential?) is never called with that authentication method. It seems task-specific challenges aren't coming through at all. Also, while the DCAppAttestService API appears to be available on macOS, DCAppAttestService.isSupported always returns false (in my testing), which suggests it's not actually supported on macOS. Can anyone confirm if that’s expected behavior?
2
0
143
May ’25
iOS26 background lock screen Blood glucose monitoring Bluetooth low energy disconnect sleep
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?
1
0
159
Oct ’25
BGContinuedProcessingTask UI
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?
2
0
193
Oct ’25
SMAppService
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.
5
0
178
Nov ’25
Background refresh or processing app
I am writing an app which mainly is used to update data used by other apps on the device. After the user initializes some values in the app, they almost never have to return to it (occasionally to add a "friend"). The app needs to run a background task at least daily, however, without the user's intervention (or even awareness, once they've given permission). My understanding of background refresh tasks is that if the user doesn't activate the app in the foreground periodically, the scheduled background tasks may never run. If this is true, do I want to use a background processing task instead, or is there a better solution (or have I misunderstood entirely)?
1
0
400
Jan ’25
My system daemons are not getting launched in MacOS 15x post reboot
When I install my application, it installs fine and everything works alongwith all the system level daemons but when I reboot the system, none of my daemons are getting launched and this happens only on MacOS 15x, on older version it is working fine. In the system logs, I see that my daemons have been detected as legacy daemons by backgroundtaskmanagementd with Disposition [enabled, allowed, visible, notified] 2025-01-13 21:17:04.919128+0530 0x60e Default 0x0 205 0 backgroundtaskmanagementd: [com.apple.backgroundtaskmanagement:main] Type: legacy daemon (0x10010) 2025-01-13 21:17:04.919128+0530 0x60e Default 0x0 205 0 backgroundtaskmanagementd: [com.apple.backgroundtaskmanagement:main] Flags: [ legacy ] (0x1) 2025-01-13 21:17:04.919129+0530 0x60e Default 0x0 205 0 backgroundtaskmanagementd: [com.apple.backgroundtaskmanagement:main] Disposition: [enabled, allowed, visible, notified] (0xb) But later, it backgroundtaskmanagementd decides to disallow it. 2025-01-13 21:17:05.013202+0530 0x32d Default 0x4d6 89 0 smd: (BackgroundTaskManagement) [com.apple.backgroundtaskmanagement:main] getEffectiveDisposition: disposition=[enabled, disallowed, visible, notified], have LWCR=true 2025-01-13 21:17:05.013214+0530 0x32d Error 0x0 89 0 smd: [com.apple.xpc.smd:all] Legacy job is not allowed to launch: &lt;private&gt; status: 2 Is there anything changed in latest Mac OS which is causing this issue? Also what does this status 2 means. Can someone please help with this error? The plist has is true
3
0
340
Feb ’25
Is there an API to programmatically obtain an XPC Service's execution context?
Hello! I'm writing a System Extension that is an Endpoint Security client. And I want to Deny/Allow executing some XPC Service processes (using the ES_EVENT_TYPE_AUTH_EXEC event) depending on characteristics of a process that starts the XPC Service. For this purpose, I need an API that could allow me to obtain an execution context of the XPC Service process. I can obtain this information using the "sudo launchctl procinfo <pid>" command (e.g. I can use the "domain = pid/3428" part of the output for this purpose). Also, I know that when the xpcproxy process is started, it gets as the arguments a service name and a pid of the process that requests the service so I can grasp the execution context from xpcproxy launching. But are these ways to obtain this info legitimate?
2
0
164
Apr ’25
BGContinuedProcessingTask what's the point?
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.
7
0
191
Oct ’25
SSMenuAgent consuming lots of CPU
My load average on a largely idle system is around 22, going up to 70 or so periodically; SSMenuAgent seems to be consuming lots of CPU (and, looking at spindump, it certainly seems busy), but... it's not happening on any other system whose screens I am observing. (Er, I know about load average limitations, the process is also consuming 70-98% CPU according to both top and Activity Monitor.) Since this machine (although idle) has our network extension, I'm trying to figure out if this is due to that, or of this is generally expected. Anyone?
2
0
425
May ’25
TCC Permission Inheritance Failure: Swift Parent -> Python Child
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).
3
0
168
Nov ’25