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!
Processes & Concurrency
RSS for tagDiscover how the operating system manages multiple applications and processes simultaneously, ensuring smooth multitasking performance.
Selecting any option will automatically load the page
Post
Replies
Boosts
Views
Activity
when we use raise in GCD, the signal handler is executed asynchronously, whereas in pthread, it is executed synchronously as expected.
example:
#include <Foundation/Foundation.h>
#include <pthread/pthread.h>
static void HandleSignal(int sigNum, siginfo_t* signalInfo, void* userContext) {
printf("handle signal %d\n", sigNum);
printf("begin sleep\n");
sleep(3);
printf("end sleep\n");
}
void InstallSignal(void) {
static const int g_fatalSignals[] =
{
SIGABRT,
SIGBUS,
SIGFPE,
SIGILL,
SIGPIPE,
SIGSEGV,
SIGSYS,
SIGTRAP,
};
int fatalSignalsCount = sizeof(g_fatalSignals) / sizeof(int);
struct sigaction action = {{0}};
action.sa_flags = SA_SIGINFO | SA_ONSTACK;
#if defined(__LP64__)
action.sa_flags |= SA_64REGSET;
#endif
sigemptyset(&action.sa_mask);
action.sa_sigaction = &HandleSignal;
struct sigaction pre_sa;
for(int i = 0; i < fatalSignalsCount; i++) {
int sigResult = sigaction(g_fatalSignals[i], &action, &pre_sa);
}
}
void* RaiseAbort(void *userdata) {
raise(SIGABRT);
printf("signal handler has finished\n");
return NULL;
}
int main(int argc, const char * argv[]) {
InstallSignal();
dispatch_async(dispatch_get_global_queue(0, 0), ^{
raise(SIGABRT);
// abort(); // abort() is ok
RaiseAbort(nullptr);
});
// pthread is ok
// pthread_t tid;
// int ret = pthread_create(&tid, NULL, RaiseAbort, NULL);
// if (ret != 0) {
// fprintf(stderr, "create thread failed\n");
// return EXIT_FAILURE;
// }
[[NSRunLoop mainRunLoop] run];
return 0;
}
console log:
signal handler has finished
handle signal 6
begin sleep
end sleep
The following code worked as expected on iOS 26 RC, but it no longer works on the official release of iOS 26.
Is there something I need to change in order to make it work on the official version?
Registration
BGTaskScheduler.shared.register(
forTaskWithIdentifier: taskIdentifier,
using: nil
) { task in
//////////////////////////////////////////////////////////////////////
// This closure is not called on the official release of iOS 26
//////////////////////////////////////////////////////////////////////
let task = task as! BGContinuedProcessingTask
var shouldContinue = true
task.expirationHandler = {
shouldContinue = false
}
task.progress.totalUnitCount = 100
task.progress.completedUnitCount = 0
while shouldContinue {
sleep(1)
task.progress.completedUnitCount += 1
task.updateTitle("\(task.progress.completedUnitCount) / \(task.progress.totalUnitCount)", subtitle: "any subtitle")
if task.progress.completedUnitCount == task.progress.totalUnitCount {
break
}
}
let completed = task.progress.completedUnitCount >= task.progress.totalUnitCount
if completed {
task.updateTitle("Completed", subtitle: "")
}
task.setTaskCompleted(success: completed)
}
Request
let request = BGContinuedProcessingTaskRequest(
identifier: taskIdentifier,
title: "any title",
subtitle: "any subtitle",
)
request.strategy = .queue
try BGTaskScheduler.shared.submit(request)
Sample project code:
https://github.com/HikaruSato/ExampleBackgroundProcess
Currently I am trying to find a work around to fetch data from server and update user defaults when app is forced quit. Can anyone suggest for this ?
I'm troubleshooting a crash I do not understand.
I have a queue called DataQueue which never has anything dispatched to it - it's the sample buffer delegate of an AVCaptureVideoDataOutput. It can call DispatchQueue.main.sync to do some work on the main thread.
It works fine no matter what we test, but has some crashes in the field that I need to fix. Here's it crashing:
AppleCameraDataDelegate.dataQueue
0 libsystem_kernel.dylib 0x7bdc __ulock_wait + 8
1 libdispatch.dylib 0x4a80 _dlock_wait + 52
2 libdispatch.dylib 0x486c _dispatch_thread_event_wait_slow$VARIANT$mp + 52
3 libdispatch.dylib 0x113d8 __DISPATCH_WAIT_FOR_QUEUE__ + 332
4 libdispatch.dylib 0x10ff0 _dispatch_sync_f_slow + 140
The main thread isn't doing something I asked it to, but appears to be busy:
Thread
0 libsystem_kernel.dylib 0x71a4 __psynch_cvwait + 8
1 libsystem_pthread.dylib 0x7fd8 _pthread_cond_wait$VARIANT$mp + 1232
2 grpc 0x2cb670 gpr_cv_wait + 131 (sync.cc:131)
3 grpc 0x119688 grpc_core::Executor::ThreadMain(void*) + 225 (executor.cc:225)
4 grpc 0x2e023c grpc_core::(anonymous namespace)::ThreadInternalsPosix::ThreadInternalsPosix(char const*, void (*)(void*), void*, bool*, grpc_core::Thread::Options const&)::'lambda'(void*)::__invoke(void*) + 146 (thd.cc:146)
5 libsystem_pthread.dylib 0x482c _pthread_start + 104
6 libsystem_pthread.dylib 0xcd8 thread_start + 8
Can anyone help me understand why this is a crash?
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.
Hi,
I have a sandboxed app with a bundled sandboxed XPC service. When it’s launched, the XPC service registers a repeating XPC activity with the system. The activity’s handler block does get called regularly like I’d expect, but it stops being called once the main app terminates.
What’s the recommended way to fix this issue? Could I have a bundled XPC service double as a launch agent, or would that cause other problems?
We are building a 'server' application that can either run as a daemon or can run in background without showing any GUI. Basically, the end user can either configure this to run as a daemon so that it can be tied to the user's session or will launch the process which user will start and quit as needed.
I wanted to understand what is the recommended mechanism for such an application from Apple -
Should this application be built as a macOS Bundle ? Apple documentation also says that we should not daemonize the process by calling fork. Hence if we create a unix-style executable, will I not need to fork to make it run in a detached state when I launch the executable via double-click ? [Reference Link]
Is it fine to have an application on macOS which is a bundle but does not show any UI when launched by double click on the app-icon or via 'open'? While we have been able to achieve this by using NSApplicationMain and not showing the UI, was wondering if using CFRunLoop is best for this case as it is a non-gui application.
If we can get the right documentation link or recommendations on how we should build such an application which can run in a non-gui mode and also in a daemonized manner, it will help us.
Should the application be always built as a macos bundle or should it be a unix-style executable to support both the cases - by the same application/product and how should we look at the distribution of such applications.
I have an app for macOS that is built using Mac Catalyst. I need to perform some background processing. I'm using BGProcessingTaskRequest to schedule the request. I have also integrated CKSyncEngine so I need that to be able to perform its normal background processing.
On iOS, when the user leaves the app, I can see a log message that the request was scheduled and a bit later I see log messages coming from the actual background task code.
On macOS I ran the app from Xcode. I then quit the app (Cmd-q). I can see the log message that the request was scheduled. But the actual task is never run. In my test, I ran my app on a MacBook Pro running macOS 26.0. When I quit the app, I checked the log file in the app sandbox and saw the message that the task was scheduled. About 20 minutes later I closed the lid on the MacBook Pro for the night. I did not power down, it just went to sleep. Roughly 10 hours later I opened the lid on the MacBook Pro, logged in, and checked the log file. It had not been updated since quitting the app. I should also mention that the laptop was not plugged in at all during this period.
My question is, does a Mac Catalyst app support background processing after the user quits the app? If so, how is it enabled?
The documentation for BGProcessingTaskRequest and BGProcessingTask show they are supported under Mac Catalyst, but I couldn't find any documentation in the Background Tasks section that mentioned anything specific to setup for Mac Catalyst.
Running the Settings app and going to General -> Login Items & Extension, I do not see my app under the App Background Activity section. Does it need to be listed there? If so, what steps are needed to get it there?
If this is all documented somewhere, I'd appreciate a link since I was not able to find anything specific to making this work under Mac Catalyst.
Topic:
App & System Services
SubTopic:
Processes & Concurrency
Tags:
CloudKit
macOS
Mac Catalyst
Background Tasks
For some reason, after invoking an unrelated dlclose() call to unload any .dylib that had previously been loaded via dlopen(..., RTLD_NOW), the subsequent call to task_info(mach_task_self(), TASK_DYLD_INFO, ...) syscall returns unexpected structure in dyld_uuid_info image_infos->uuidArray, that, while it seems to represent an array of struct dyld_uuid_info elements, there is only 1 such element (dyld_all_image_infos *infos->uuidArrayCount == 1) and the app crashes when trying to access dyld_uuid_info image->imageLoadAddress->magic, as image->imageLoadAddress doesn't seem to represent a valid struct mach_header structure address (although it looks like a normal pointer within the process address space. What does it point to?).
This reproduces on macOS 15.4.1 (24E263)
Could you please confirm that this is a bug in the specified OS build, or point to incorrect usage of the task_info() API?
Attaching the C++ file that reproduces the issue to this email message
It needs to be built on macOS 15.4.1 (24E263) via Xcode or just a command line clang++ compiler. It may crash or return garbage, depending on memory layout, but on this macOS build it doesn’t return a correct feedfacf magic number for the struct mach_header structure.
Thank you
Feedback Assistant reference: FB18431345
//On `macOS 15.4.1 (24E263)` create a C++ application (for example, in Xcode), with the following contents. Note, that this application should crash on this macOS build. It will not crash, however, if you either:
//1. Comment out `dlclose()` call
//2. Change the order of the `performDlOpenDlClose()` and `performTaskInfoSyscall()` functions calls (first performTaskInfoSyscall() then performDlOpenDlClose()).
#include <iostream>
#include <dlfcn.h>
#include <mach/mach.h>
#include <mach-o/dyld_images.h>
#include <mach-o/loader.h>
void performDlOpenDlClose() {
printf("dlopen/dlclose function\n");
printf("Note: please adjust the path below to any real dylib on your system, if the path below doesn't exist!\n");
std::string path = "/Applications/Xcode.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/lib/libswiftDemangle.dylib";
printf("Dylib to open: %s\n", path.c_str());
void* handle = ::dlopen(path.c_str(), RTLD_NOW);
if(handle) {
::dlclose(handle);
} else {
printf("Error: %s\n", dlerror());
}
}
void performTaskInfoSyscall() {
printf("Making a task_info() syscall\n");
printf("\033[34mSource File: %s\033[0m\n", __FILE__);
task_t task = mach_task_self();
struct task_dyld_info dyld_info;
mach_msg_type_number_t size = TASK_DYLD_INFO_COUNT;
kern_return_t kr = task_info(task, TASK_DYLD_INFO, (task_info_t)&dyld_info, &size);
if (kr != KERN_SUCCESS) {
fprintf(stderr, "task_info failed: %s\n", mach_error_string(kr));
}
const struct dyld_all_image_infos* infos =
(const struct dyld_all_image_infos*)dyld_info.all_image_info_addr;
printf("version: %d, infos->infoArrayCount: %d\n", infos->version, infos->infoArrayCount);
for(uint32_t i=0; i<infos->infoArrayCount; i++) {
dyld_image_info image = infos->infoArray[i];
const struct mach_header* header = image.imageLoadAddress;
printf("%d ", i);
printf("%p ", (void*)image.imageLoadAddress);
printf("(%x) ", header->magic);
printf("%s\n", image.imageFilePath);
fflush(stdout);
}
printf("\n\n");
printf("infos->uuidArrayCount: %lu\n", infos->uuidArrayCount);
for(uint32_t i=0; i<infos->uuidArrayCount; i++) {
dyld_uuid_info image = infos->uuidArray[i];
const struct mach_header* header = image.imageLoadAddress;
printf("%d ", i);
printf("%p ", (void*)image.imageLoadAddress);
printf("(%x)\n", header->magic);
fflush(stdout);
}
printf("task_info() syscall result processing is completed\n\n");
}
int main(int argc, const char * argv[]) {
performDlOpenDlClose();
performTaskInfoSyscall();
return 0;
}
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
Hi, I'm working on an application on MacOS. It contains a port-forward feature on TCP protocol.
This application has no UI, but a local HTTP server where user can access to configure this application.
I found that my application always exit for unknown purpose after running in backgruond for minutes. I think this is about MacOS's background process controlling.
Source codes and PKG installers are here: https://github.com/burningtnt/Terracotta/actions/runs/16494390417
I'm a developer using Lazarus Pascal, so converting ObjC and Swift comes with its challenges.
I'm trying to figure how to properly use SMAppService to add my application as a login item for the App Store.
I have learned that the old method (< macOS 13) uses a helper tool, included in the app bundle, which calls the now deprecated SMLoginItemSetEnabled. Now this is already quite a pain to deal with if you're not using XCode, not to mention converting the headers being rather complicated when you're not experienced with doing this.
The "new" method (as of macOS 13) is using SMAppService.
Can anyone explain how to use this? The documentation (for me anyway) is a not very clear about that and neither are examples that can be found all over the Internet.
My main question is:
Can I now use the SMAppService functions to add/remove a login item straight in my application, or is a helper tool still required?
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
Hi,
I'll explain my question through how whatsapp does it.
When the phone is locked then whatsapp routes call through apple's native callkit
When unlocked, pressing accept essentially redirects to whatsapp and then whatsapp handles the call from there.
However, this component of unlock detection is what I'm not able to find any info about.
Essentially,
how i do it is:
let isPhoneLocked = !UIApplication.shared.isProtectedDataAvailable
isProtectedDataAvailable == true → device is unlocked
isProtectedDataAvailable == false → device is locked
The problem is that if the phone has been recently unlocked, then protected data is still available on the phone even after the lock for the next 10-40 seconds. So theres a false positive.
I want there to be a foolproof and robust way to do this. And I'm not entirely sure how
Hello,
I have a question about a edge case scenario.
Before that some info on my project-
I have a launchdaemon that carries out some business logic, it also has XPC listener (built using C APIs).
Question-
Can there be a situation when the daemon is up and running but the XPC listener is down(due to some error or crash)? If yes then do I need to handle it in my code or launchd will handle it?
when the daemon is stopped or shut down, how do I stop the XPC listener? After getting listener object from xpc_connection_create_mach_service should I just call xpc_connection_cancel followed by a call to xpc_release?
Thanks!
K
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];
}
Hello,
My team has developed a DNS proxy for macOS. We have this set up with a system extension that interacts with the OS, and an always-running daemon that does all the heavy lifting. Communication between the two is DNS request and response packet traffic.
With this architecture what are best practices for how the system extension communicates with a daemon?
We tried making the daemon a socket server, but the system extension could not connect to it.
We tried using XPC but it did not work and we could not understand the errors that were returned.
So what is the best way to do this sort of thing?
Topic:
App & System Services
SubTopic:
Processes & Concurrency
Tags:
XPC
System Extensions
Network Extension
Service Management
We are seeing a strange lifecycle issue on multiple MDM-managed iPads where
application(_:didFinishLaunchingWithOptions:) is not called after the device is idle overnight.
Even if we terminate the app manually via the app switcher, the next morning the system does not perform a cold launch. Instead, the app resumes directly in:
applicationDidBecomeActive(_:)
This causes all initialization logic that depends on didFinishLaunching to be completely skipped.
This behavior is consistent across four different supervised MDM devices.
Environment
Devices: iPads enrolled in MDM (supervised)
iOS version: 18.3
Xcode: 16.4
macOS: Sequoia 15.7.2
App type: Standard UIKit iOS app
App: Salux Audiometer (App Store app)
Expected Behavior
If the app was terminated manually using the app switcher, the next launch should:
Start a new process
Trigger application(_:didFinishLaunchingWithOptions:)
Follow the normal cold-start lifecycle
Actual Behavior
After leaving the iPad idle overnight (8–12 hours):
The next launch skips didFinishLaunching
The app resumes directly in applicationDidBecomeActive
No new process is started
App behaves as if it had been suspended, even though it was manually terminated
Logs (Relevant Extracts)
Day 1 — Normal cold launch
[12:06:44.152 PM] PROCESS_STARTED
[12:06:44.214 PM] DID_FINISH_LAUNCHING_START launchOptions=[]
[12:06:44.448 PM] DID_FINISH_LAUNCHING_END
We then used the app and terminated it via app switcher.
Day 2 — Unexpected resume without cold start
[12:57:49.328 PM] APP_DID_BECOME_ACTIVE
No PROCESS_STARTED
No didFinishLaunching
No cold-start logs
This means the OS resumed the app from a previous state that should not exist.
Reproducible Steps
Use an MDM-enrolled iPad.
Launch the app normally.
Terminate it manually via the multitasking app switcher.
Leave the device idle overnight (8–12 hours).
Launch the app the next morning.
Observe that:
didFinishLaunching does not fire
applicationDidBecomeActive fires directly
Questions for Apple Engineers / Community
Is this expected behavior on MDM-supervised devices in iOS 18?
Are there any known OS-level changes where terminated apps may be revived from disk/memory?
Could MDM restrictions or background restoration policies override app termination?
How can we ensure that our app always performs a clean initialization when launched after a long idle period?
Additional Information
We have full logs from four separate MDM iPads showing identical behavior.
Happy to share a minimal reproducible sample if required.
I posted here https://developer.apple.com/forums/thread/805554?page=1#867766022 but posting again for visibility (and let me know how I can file a bug)
There was a response in that thread that said you could use the childProgress system to help updating progresses to keep the backgroundTask alive.
What I've found is that using childProgresses results in more terminations than if you just updated the progress directly.
Here is my setups to test this
A BGContinuedProcessingTask that uses URLSessions to upload, and registers the task.progress with the Urlsession Progress
Same, but the task.progress gets updated via a UrlSession Callback
The second is MUCH more stable out in the field in cellular settings, the first fails extremely frequently.
My suspicion is that in the documentation here https://developer.apple.com/documentation/foundation/progress#Reporting-Progress-for-Multiple-Operations
it explicitly states
The completedUnitCount property for a containing progress object only updates when the suboperation is 100% complete. The fractionCompleted property for a containing progress object updates continuously as work progresses for all suboperations.
I wonder if BGContinuedProcessingTask is only looking at completedUnitCount for progress, and not fractionCompleted?
In either case, I would love to use the childProgresses because there are bugs with retries by updating the progress manually, so would love some help resolving this, Thanks!