I abandoned Mac development back around 10.4 when I departed Apple and am playing catch-up, trying to figure out how to register a privileged helper tool that can execute commands as root in the new world order. I am developing on 13.1 and since some of these APIs debuted in 13, I'm wondering if that's ultimately the root of my problem.
Starting off with the example code provided here:
https://developer.apple.com/documentation/servicemanagement/updating-your-app-package-installer-to-use-the-new-service-management-api
Following all build/run instructions in the README to the letter, I've not been successful in getting any part of it to work as documented. When I invoke the register command the test app briefly appears in System Settings for me to enable, but once I slide the switch over, it disappears. Subsequent attempts to invoke the register command are met only with the error message:
`Unable to register Error Domain=SMAppServiceErrorDomain Code=1 "Operation not permitted" UserInfo={NSLocalizedFailureReason=Operation not permitted}
The app does not re-appear in System Settings on these subsequent invocations. When I invoke the status command the result mysteriously equates to SMAppService.Status.notFound.
The plist is in the right place with the right name and it is using the BundleProgram key exactly as supplied in the sample code project. The executable is also in the right place at Contents/Resources/SampleLaunchAgent relative to the app root.
The error messaging here is extremely disappointing and I'm not seeing any way for me to dig any further without access to the underlying Objective-C (which the Swift header docs reference almost exclusively, making it fairly clear that this was a... Swift... Port... [Pun intended]).
Processes & Concurrency
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Hello,
I'm experiencing an issue with my app where it's being terminated by the system with a watchdog violation during back-to-back messaging operations. I've analyzed the crash logs but would appreciate additional insights on optimizing my approach. I'd appreciate any insights on how to resolve this problem.
Crash Details:
Exception Type: EXC_CRASH (SIGKILL)
Termination Reason: FRONTBOARD with code 0x8BADF00D
Error: "scene-update watchdog transgression: app exhausted real time allowance of 10.00 seconds"
Reproduction Steps:
User A initiates back-to-back messages to other User
User A's UI becomes unresponsive and eventually the app crashes.
Stack Trace Analysis:
The crash occurs on the main thread, which appears to be blocked waiting for a condition in the keyboard handling system. The thread is stuck in [UIKeyboardTaskQueue _lockWhenReadyForMainThread] and related methods, suggesting an issue with keyboard-related operations during the messaging process.
Crash Tag
Exception Type: EXC_CRASH (SIGKILL)
Exception Codes: 0x0000000000000000, 0x0000000000000000
Termination Reason: FRONTBOARD 2343432205
<RBSTerminateContext| domain:10 code:0x8BADF00D explanation:scene-update watchdog transgression: app<com.msikodiak.eptt(AD934F8A-DF57-4B75-BE73-8CF1A9A8F856)>:301 exhausted real (wall clock) time allowance of 10.00 seconds
ProcessVisibility: Foreground
ProcessState: Running
WatchdogEvent: scene-update
WatchdogVisibility: Background
WatchdogCPUStatistics: (
"Elapsed total CPU time (seconds): 6.390 (user 3.640, system 2.750), 11% CPU",
"Elapsed application CPU time (seconds): 0.020, 0% CPU"
)
ThermalInfo: (
"Thermal Level: 0",
"Thermal State: nominal"
) reportType:CrashLog maxTerminationResistance:Interactive>
Triggered by Thread: 0
Thread 0 name: Dispatch queue: com.apple.main-thread
Thread 0 Crashed:
0 libsystem_kernel.dylib 0x1e773d438 __psynch_cvwait + 8
1 libsystem_pthread.dylib 0x2210bc328 _pthread_cond_wait + 1028
2 Foundation 0x1957d8a64 -[NSCondition waitUntilDate:] + 132
3 Foundation 0x1957d8888 -[NSConditionLock lockWhenCondition:beforeDate:] + 80
4 UIKitCore 0x1998f1238 -[UIKeyboardTaskQueue _lockWhenReadyForMainThread] + 456
5 UIKitCore 0x19a3d775c __59-[UIKeyboardImpl updateAutocorrectPrompt:executionContext:]_block_invoke_9 + 28
6 UIKitCore 0x19986b084 -[UIKeyboardTaskQueue lockWhenReadyForMainThread] + 168
7 UIKitCore 0x19a3f2994 -[UIKeyboardTaskQueue waitUntilTaskIsFinished:] + 148
8 UIKitCore 0x19a3f2ac4 -[UIKeyboardTaskQueue performSingleTask:breadcrumb:] + 132
9 UIKitCore 0x199e2f7e4 -[_UIKeyboardStateManager updateForChangedSelection] + 144
10 UIKitCore 0x199e24200 -[_UIKeyboardStateManager invalidateTextEntryContextForTextInput:] + 92
11 WebKit 0x1ad52fa54 WebKit::PageClientImpl::didProgrammaticallyClearFocusedElement(WebCore::ElementContext&&) + 40
12 WebKit 0x1ad55adcc WebKit::WebPageProxy::didProgrammaticallyClearFocusedElement(WebCore::ElementContext&&) + 136
13 WebKit 0x1acec74e8 WebKit::WebPageProxy::didReceiveMessage(IPC::Connection&, IPC::Decoder&) + 18604
14 WebKit 0x1acd21184 IPC::MessageReceiverMap::dispatchMessage(IPC::Connection&, IPC::Decoder&) + 236
15 WebKit 0x1ace449b8 WebKit::WebProcessProxy::dispatchMessage(IPC::Connection&, IPC::Decoder&) + 40
16 WebKit 0x1ace44228 WebKit::WebProcessProxy::didReceiveMessage(IPC::Connection&, IPC::Decoder&) + 1764
17 WebKit 0x1acd1e904 IPC::Connection::dispatchMessage(WTF::UniqueRef<IPC::Decoder>) + 268
18 WebKit 0x1acd1e478 IPC::Connection::dispatchIncomingMessages() + 576
19 JavaScriptCore 0x1ae386b8c WTF::RunLoop::performWork() + 524
20 JavaScriptCore 0x1ae386960 WTF::RunLoop::performWork(void*) + 36
21 CoreFoundation 0x196badce4 __CFRUNLOOP_IS_CALLING_OUT_TO_A_SOURCE0_PERFORM_FUNCTION__ + 28
22 CoreFoundation 0x196badc78 __CFRunLoopDoSource0 + 172
23 CoreFoundation 0x196bac9fc __CFRunLoopDoSources0 + 232
24 CoreFoundation 0x196babc3c __CFRunLoopRun + 840
25 CoreFoundation 0x196bd0700 CFRunLoopRunSpecific + 572
26 GraphicsServices 0x1e3711190 GSEventRunModal + 168
27 UIKitCore 0x1997ee240 -[UIApplication _run] + 816
28 UIKitCore 0x1997ec470 UIApplicationMain + 336
29 Telstra PTT 0x1004d30c8 main + 56
30 dyld 0x1bd5d3ad8 start + 5964
Started a new X-Code Project after updating to 26.0.1 and realized that I get an error when trying to mark a class as ObservableObject => "Class XYZ does not conform to Protocol 'ObservableObject'.
Strange behaviour, because at old projects the code is working even though the build options are the same and other settings like iOS version in Target are the same.
There must be something chaged under the hood of XCode? I have to import Combine now, before I could write my class, e.g. CoreData Datamanager: ObservableObject only using CoreData.
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.
Swift Concurrency Resources:
Forums tags: Concurrency
The Swift Programming Language > Concurrency documentation
Migrating to Swift 6 documentation
WWDC 2022 Session 110351 Eliminate data races using Swift Concurrency — This ‘sailing on the sea of concurrency’ talk is a great introduction to the fundamentals.
WWDC 2021 Session 10134 Explore structured concurrency in Swift — The table that starts rolling out at around 25:45 is really helpful.
Swift Async Algorithms package
Swift Concurrency Proposal Index DevForum post
Why is flow control important? forums post
Matt Massicotte’s blog
Dispatch Resources:
Forums tags: Dispatch
Dispatch documentation — Note that the Swift API and C API, while generally aligned, are different in many details. Make sure you select the right language at the top of the page.
Dispatch man pages — While the standard Dispatch documentation is good, you can still find some great tidbits in the man pages. See Reading UNIX Manual Pages. Start by reading dispatch in section 3.
WWDC 2015 Session 718 Building Responsive and Efficient Apps with GCD [1]
WWDC 2017 Session 706 Modernizing Grand Central Dispatch Usage [1]
Avoid Dispatch Global Concurrent Queues forums post
Waiting for an Async Result in a Synchronous Function forums post
Share and Enjoy
—
Quinn “The Eskimo!” @ Developer Technical Support @ Apple
let myEmail = "eskimo" + "1" + "@" + "apple.com"
[1] These videos may or may not be available from Apple. If not, the URL should help you locate other sources of this info.
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
Topic:
App & System Services
SubTopic:
Processes & Concurrency
Tags:
Background Tasks
User Notifications
I'm trying to understand how the API works to perform a function that can continue running if the user closes the app. For a very simple example, consider a function that increments a number on screen every second, counting from 1 to 100, reaching completion at 100. The user can stay in the app for 100s watching it work to completion, or the user can close the app say after 2s and do other things while watching it work to completion in the Live Activity.
To do this when the user taps a Start Counting button, you'd
1 Call BGTaskScheduler.shared.register(forTaskWithIdentifier:using:launchHandler:).
Question 1: Do I understand correctly, all of the logic to perform this counting operation would exist entirely in the launchHandler block (noting you could call another function you define passing it the task to be able to update its progress)? I am confused because the documentation states "The system runs the block of code for the launch handler when it launches the app in the background." but the app is already open in the foreground. This made me think this block is not going to be invoked until the user closes the app to inform you it's okay to continue processing in the background, but how would you know where to pick up. I want to confirm my thinking was wrong, that all the logic should be in this block from start to completion of the operation, and it's fine even if the app stays in the foreground the whole time.
2 Then you'd create a BGContinuedProcessingTaskRequest and set request.strategy = .fail for this example because you need it to start immediately per the user's explicit tap on the Start Counting button.
3 Call BGTaskScheduler.shared.submit(request).
Question 2: If the submit function throws an error, should you handle it by just performing the counting operation logic (call your function without passing a task)? I understand this can happen if for some reason the system couldn't immediately run it, like if there's already too many pending task requests. Seems you should not show an error message to the user, should still perform the request and just not support background continued processing for it (and perhaps consider showing a light warning "this operation can't be continued in the background so keep the app open"). Or should you still queue it up even though the user wants to start counting now? That leads to my next question
Question 3: In what scenario would you not want the operation to start immediately (the queue behavior which is the default), given the app is already in the foreground and the user requested some operation? I'm struggling to think of an example, like a button titled Compress Photos Whenever You Can, and it may start immediately or maybe it won't? While waiting for the launchHandler to be invoked, should the UI just show 0% progress or "Pending" until the system can get to this task in the queue? Struggling to understand the use cases here, why make the user wait to start processing when they might not even intend to close the app during the operation?
Thanks for any insights! As an aside, a sample project with a couple use cases would have been incredibly helpful to understand how the API is expected to be used.
Hello,
I have a few questions regarding the documentation here:
Can this method described in the article be built with Xcode 26 and run on iOS 26? Or is it restricted to run only on iOS 26, since AppExtensionPoint appears to be available starting from iOS 26?
Does this approach allow two apps under the same Team ID to communicate with each other?
Does this approach also allow two apps under different Team IDs to communicate with each other?
Is it mandatory to implement EXAppExtensionBrowserViewController and obtain user consent before using this method to exchange information?
In our implementation, we followed the documentation. Inside EXAppExtensionBrowserViewController, we were able to see the Generic Extension from another app and enabled the permission.
However, we still get the following error:
Failed to connect: Error Domain=NABUExtensionConnector Code=1
"No matching extension found"
UserInfo={NSLocalizedDescription=No matching extension found}
Could someone clarify whether this is expected behavior, or if we are missing an additional configuration step?
Thanks in advance!
Hello,
I'm running into an issue with a complex macOS application (non-AppStore) structure involving an unsandboxed system daemon and a sandboxed SSO Extension attempting to communicate via XPC Mach service.
The macOS app is composed of three main components:
Main App: unsandboxed, standard macOS application.
System Daemon: unsandboxed executable installed with a .plist to /Library/LaunchDaemons/ and loaded by launchd. It exposes an XPC Mach Service.
SSO Extension: a sandboxed Authentication Services Extension (ASAuthorizationProviderExtension).
Main App to System Daemon communication works perfectly. The unsandboxed main app can successfully create and use an XPC connection to the System Daemon's Mach service.
But SSO Extension cannot establish an XPC connection to the System Daemon's Mach service, despite using the recommended temporary exception entitlement. I have added the following entitlement to the SSO Extension's entitlements file:
<key>com.apple.security.temporary-exception.mach-lookup.global-name</key>
<array>
<string>my.xpc.service.system.daemon</string>
</array>
(The name my.xpc.service.system.daemon is the exact name registered by the System Daemon in its Launch Daemon plist's MachServices dictionary.)
When the SSO Extension attempts to create the connection, the following log output is generated:
default 08:11:58.531567-0700 SSOExtension [0x13f19b090] activating connection: mach=true listener=false peer=false name=my.xpc.service.system.daemon
default 08:11:58.532150-0700 smd [0xb100d8140] activating connection: mach=false listener=false peer=true name=com.apple.xpc.smd.peer[1575].0xb100d8140
error 08:11:58.532613-0700 smd Item real path failed. Maybe the item has been deleted?
error 08:11:58.532711-0700 SSOExtension Unable to find service status () error: 22
The error Unable to find service status () error: 22. Error code 22 typically translates to EINVAL (Invalid argument), but in this context, it seems related to the system's ability to find and activate the service for the sandboxed process.
Questions:
Is the com.apple.security.temporary-exception.mach-lookup.global-name entitlement sufficient for a sandboxed SSO Extension to look up a system-wide Launch Daemon Mach service, or are there additional restrictions or required entitlements for extensions?
The smd log output Item real path failed. Maybe the item has been deleted? seems concerning. Since the unsandboxed main app can connect, this suggests the service is running and registered. Could this error indicate a sandbox permission issue preventing smd from verifying the path for the sandboxed process?
Are there specific sandboxing requirements for Mach service names when communicating from an Extension versus a main application?
Any guidance on how a sandboxed SSO Extension can reliably connect to an unsandboxed, non-app-group-related system daemon via XPC Mach service would be greatly appreciated!
To establish a privileged helper daemon from a command line app to handle actions requiring root privileges I still use the old way of SMJobBless. But this is deprecated since OSX 10.13 and I want to finally update it to the new way using SMAppService.
As I'm concerned with securing it against malicious exploits, do you have a recommended up-to-date implementation in Objective-C establishing a privileged helper and verifying it is only used by my signed app?
I've seen the suggestion in the documentation to use SMAppService, but couldn't find a good implementation covering security aspects. My old implementation in brief is as follows:
bool runJobBless () {
// check if already installed
NSFileManager* filemgr = [NSFileManager defaultManager];
if ([filemgr fileExistsAtPath:@"/Library/PrivilegedHelperTools/com.company.Helper"] &&
[filemgr fileExistsAtPath:@"/Library/LaunchDaemons/com.company.Helper.plist"])
{
// check helper version to match the client
// ...
return true;
}
// create authorization reference
AuthorizationRef authRef;
OSStatus status = AuthorizationCreate (NULL, kAuthorizationEmptyEnvironment, kAuthorizationFlagDefaults, &authRef);
if (status != errAuthorizationSuccess) return false;
// obtain rights to install privileged helper
AuthorizationItem authItem = { kSMRightBlessPrivilegedHelper, 0, NULL, 0 };
AuthorizationRights authRights = { 1, &authItem };
AuthorizationFlags flags = kAuthorizationFlagDefaults | kAuthorizationFlagInteractionAllowed | kAuthorizationFlagPreAuthorize | kAuthorizationFlagExtendRights;
status = AuthorizationCopyRights (authRef, &authRights, kAuthorizationEmptyEnvironment, flags, NULL);
if (status != errAuthorizationSuccess) return false;
// SMJobBless does it all: verify helper against app and vice-versa, place and load embedded launchd.plist in /Library/LaunchDaemons, place executable in /Library/PrivilegedHelperTools
CFErrorRef cfError;
if (!SMJobBless (kSMDomainSystemLaunchd, (CFStringRef)@"com.company.Helper", authRef, &cfError)) {
// check helper version to match the client
// ...
return true;
} else {
CFBridgingRelease (cfError);
return false;
}
}
void connectToHelper () {
// connect to helper via XPC
NSXPCConnection* c = [[NSXPCConnection alloc] initWithMachServiceName:@"com.company.Helper.mach" options:NSXPCConnectionPrivileged];
c.remoteObjectInterface = [NSXPCInterface interfaceWithProtocol:@protocol (SilentInstallHelperProtocol)];
[c resume];
// call function on helper and wait for completion
dispatch_semaphore_t semaphore = dispatch_semaphore_create (0);
[[c remoteObjectProxy] callFunction:^() {
dispatch_semaphore_signal (semaphore);
}];
dispatch_semaphore_wait (semaphore, dispatch_time (DISPATCH_TIME_NOW, 10 * NSEC_PER_SEC));
dispatch_release (semaphore);
[c invalidate];
[c release];
}
Hi,
We are running into issues with iOS app prewarming, where the system launches our app before the user has entered their passcode.
In our case, the app stores flags, counters, and session data in UserDefaults and the Keychain. During prewarm launches:
UserDefaults only returns default values (nil, 0, false). We have no way of knowing whether this information is valid or just a placeholder caused by prewarming.
Keychain items with kSecAttrAccessibleAfterFirstUnlockThisDeviceOnly are inaccessible, which can lead to broken business logic (the app can assume no session exists).
No special launch options or environment variables appear to be set.
We can reproduce this 100% of the time by starting a Live Activity in the app before reboot.
Here’s an example of the workaround we tried, following older recommendations:
__attribute__((constructor))
static void ModuleInitializer(void) {
char* isPrewarm = getenv("ActivePrewarm");
if (isPrewarm != NULL && isPrewarm[0] == '1') {
exit(0); // prevent prewarm launch from proceeding
}
}
On iOS 16+, the ActivePrewarm environment variable doesn’t seem to exist anymore (though older docs and SDKs such as Sentry reference it).
We also tried listening for UIApplication.protectedDataDidBecomeAvailableNotification, but this is not specific to prewarming (it also fires when the device gets unlocked) and can cause watchdog termination if we delay work too long.
Questions:
Is there a supported way to opt out of app prewarming?
What is the correct way to detect when an app is being prewarmed?
Is the ActivePrewarm environment variable still supported in iOS 16+?
Ideally, the UserDefaults API itself should indicate whether it is returning valid stored values or defaults due to the app being launched in a prewarm session.
We understand opting out may impact performance, but data security and integrity are our priority. Any guidance would be greatly appreciated.
What’s the recommended way to recursively walk through a directory tree using File Coordination? From what I understand, coordinating a read of a directory only performs a “shallow” lock; this would mean that I’d need to implement the recursive walk myself rather than use FileManager.enumerator(at:includingPropertiesForKeys:options:errorHandler:) plus a single NSFileCoordinator.coordinate(with:queue:byAccessor:) call.
I’m trying to extract information from all files of a particular type, so I think using NSFileCoordinator.ReadingOptions.immediatelyAvailableMetadataOnly on each file before acquiring a full read lock on it (if it’s the right file type) would make sense. Am I on the right track?
On MacOS 26 Tahoe, we are getting a background warning message stating, “App is running in the background…”
Is this expected behavior on the new OS?
Thanks
Asutos
Topic:
App & System Services
SubTopic:
Processes & Concurrency
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
Hello,
I have a question regarding the behavior of BGProcessingTaskRequest when the app is force-quit by the user via the App Switcher.
Based on common understanding and various discussions — including the following Apple Developer Forum threads:
Waking up an iOS app after app is … | Apple Developer Forums
Will BGAppRefreshTaskRequest will … | Apple Developer Forums
Background fetch after app is forc… | Apple Developer Forums
…it is widely understood that iOS prevents background execution (such as background fetch, push notifications, or BGTaskScheduler) after a user force-quits an app via the App Switcher.
However, in my app, I have observed that a scheduled BGProcessingTaskRequest still executes even after the app has been explicitly terminated via App Switcher. The task is scheduled using submit(_:error:), and it is clearly running some time after the app has been closed by the user.
That said, the task does run, but it appears to operate under tighter constraints — for example, it may be allowed to run for a shorter duration, and network requests appear to be more restricted compared to when the app is not force-quit.
My questions are:
Are there any documented or undocumented exceptions that allow this kind of behavior after force-quit?
Could this be a bug or a behavior change in recent iOS versions? (I am observing this on iOS 18.3, 18.4, and 18.5)
Any insights, experiences, or clarifications from Apple engineers or fellow developers would be greatly appreciated.
Thank you!
Hi All,
I'm working on an app that needs to connect to BLE device and on defined schedules download data from the device. the amount of data is segnificant and might take around a minute to download. we tought about utilizing both state restoration and preservation for app waking and scheduling (triggered by the ble peripheral) and BGTaskScheduler to schedule a task that will handle a long running task to manage the full data download. now, will this solution in general valid? isnt it a "hack" that goes around the 10s limit that state restoration enforces?
i know there are limitations for BGTask (like when it runs, it might be terminated by the system etc) but considering that, can we proceed with this approach without breaching apple guidelines?
thank you in advance!
Topic:
App & System Services
SubTopic:
Processes & Concurrency
Tags:
Background Tasks
Core Bluetooth
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 am currently developing a macOS app that can show system HUDs in the Notch
Till Sequoia I used to kill the OSDUIHelper process (which displays the default macOS Volume and Brightness control HUDs) - and replaced it with my app's HUDs
But, it is not working on macOS Tahoe anymore as the OSDUIHelper process is no longer there due to the UI changes
Has the process been renamed - or is there any other way to kill the process?
Topic:
App & System Services
SubTopic:
Processes & Concurrency
Tags:
Swift
macOS
SwiftUI
Background Tasks
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?