Processes & Concurrency

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

Concurrency Documentation

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Crash on DispatchQueue.main.sync from isolated thread
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?
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135
Sep ’25
XCode 26.0.1/iOS 26 unable to mark class as ObservableObject
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.
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386
Oct ’25
Does Mac Catalyst support Background Processing?
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.
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134
3w
App Terminated with 0x8BADF00D: Main Thread Blocked During Back-to-Back Messaging
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
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315
Oct ’25
XPC activity doesn’t fire while main app is closed
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?
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152
May ’25
MacOS Application as a daemon or in non-interaction mode
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.
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518
Mar ’25
Incorrect behaviour of task_info() syscall after an unrelated dlclose() call
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-&gt;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-&gt;uuidArrayCount == 1) and the app crashes when trying to access dyld_uuid_info image-&gt;imageLoadAddress-&gt;magic, as image-&gt;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 &lt;iostream&gt; #include &lt;dlfcn.h&gt; #include &lt;mach/mach.h&gt; #include &lt;mach-o/dyld_images.h&gt; #include &lt;mach-o/loader.h&gt; 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)&amp;dyld_info, &amp;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-&gt;infoArrayCount: %d\n", infos-&gt;version, infos-&gt;infoArrayCount); for(uint32_t i=0; i&lt;infos-&gt;infoArrayCount; i++) { dyld_image_info image = infos-&gt;infoArray[i]; const struct mach_header* header = image.imageLoadAddress; printf("%d ", i); printf("%p ", (void*)image.imageLoadAddress); printf("(%x) ", header-&gt;magic); printf("%s\n", image.imageFilePath); fflush(stdout); } printf("\n\n"); printf("infos-&gt;uuidArrayCount: %lu\n", infos-&gt;uuidArrayCount); for(uint32_t i=0; i&lt;infos-&gt;uuidArrayCount; i++) { dyld_uuid_info image = infos-&gt;uuidArray[i]; const struct mach_header* header = image.imageLoadAddress; printf("%d ", i); printf("%p ", (void*)image.imageLoadAddress); printf("(%x)\n", header-&gt;magic); fflush(stdout); } printf("task_info() syscall result processing is completed\n\n"); } int main(int argc, const char * argv[]) { performDlOpenDlClose(); performTaskInfoSyscall(); return 0; }
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157
Jun ’25
Questions about using App Extension communication with host apps on iOS 26 (Xcode 26)
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!
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284
Oct ’25
Recursively walk a directory using File Coordination
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?
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133
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.
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178
Nov ’25
Re-enrolling a LaunchDaemon, does it require user auth?
I am building an app that uses the SMAppService to register a LaunchDaemon that is bundled with my .app. I've got a priming flow created which walks the user through approving the service so that it will start on login. However, I need to also be able to upgrade this background service if the user updates the app. To do this, I think I need to call unregisterAndReturnError and then registerAndReturnError. From my testing, this seems to work correctly, but I have a concern. Will the user ever be prompted to re-authorize the LaunchDaemon that I am registering? If so, under what circumstances will that happen, and what does it look like (so that I can guide the user through it)?
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303
May ’25
Bundled app error with Electron app on Mac App Store
Hi, I built an Electron app that uses puppeteer-cluster to open a bundled version of Chrome. Everything works before packaging/signing with electron builder. Transporter does not report any issues and the app opens in TestFlight. the Chrome.app is signed separately before running builder hardenedRuntime = false However, a permission error occurs when cluster attempts to launch Chrome: Error: Unable to launch browser, error message: Failed to launch the browser process! [0601/152740.225314:ERROR:bootstrap.cc(65)] bootstrap_check_in org.chromium.crashpad.child_port_handshake.9915.63117.BUEXLMXFWPLCEONM: Permission denied (1100) [0601/152740.226091:ERROR:file_io.cc(94)] ReadExactly: expected 4, observed 0 [0601/152740.229808:ERROR:bootstrap.cc(65)] bootstrap_check_in org.chromium.crashpad.child_port_handshake.9913.63115.VVKELOQUCWUYPFMQ: Permission denied (1100) [0601/152740.230244:ERROR:file_io.cc(94)] ReadExactly: expected 4, observed 0 [9911:45571:0601/152740.506968:ERROR:named_platform_channel_mac.cc(44)] bootstrap_check_in com.google.chrome.for.testing.apps.52995c87946bbcc94fc9a27df1478a13: Permission denied (1100) [9911:62467:0601/152740.507564:FATAL:mach_port_rendezvous.cc(281)] Check failed: kr == KERN_SUCCESS. bootstrap_check_in com.google.chrome.for.testing.MachPortRendezvousServer.9911: Permission denied (1100) at Cluster.<anonymous> (/Applications/MyApp.app/Contents/Resources/app.asar/node_modules/puppeteer-cluster/dist/Cluster.js:119:23) at Generator.throw (<anonymous>) at rejected (/Applications/MyApp.app/Contents/Resources/app.asar/node_modules/puppeteer-cluster/dist/Cluster.js:6:65) at process.processTicksAndRejections (node:internal/process/task_queues:105:5) I'm wondering if it's an issue with entitlements, or something more. The entitlements.mas.plist (aside from identifiers): com.apple.security.app-sandbox com.apple.security.cs.allow-jit com.apple.security.cs.allow-unsigned-executable-memory com.apple.security.cs.allow-dyld-environment-variables com.apple.security.network.client com.apple.security.network.server com.apple.security.files.user-selected.read-write com.apple.security.cs.disable-executable-page-protection com.apple.security.files.user-selected.executable I've spent many hours searching for a solution. Any help or insight would be greatly appreciated.
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148
Jun ’25
How to capture stderr from a macOS GUI app (UIKit/AppKit) when launched via open or Finder?
For a macOS GUI application (with a UIKit or AppKit entry point), I want to reliably capture diagnostic logs sent to stderr — especially useful when the app is launched from a terminal script or runs in the background, and traditional GUI elements (like alert dialogs) may not be viable. This is to log startup failures or even success messages for later inspection. However, when the app is launched via open MyApp.app, stderr redirection like open MyApp.app 2> log.txt does not capture any output — the file is created, but remains empty. The only way I can capture stderr reliably is by bypassing the bundle and directly launching the binary inside with ./MyApp.app/Contents/MacOS/MyApp 2> ~/log.txt This logs as expected, but is not the user-friendly or typical way to launch apps on macOS. Double-clicking the app in Finder also does not show any stderr output. Is there any recommended or supported way to redirect or access stderr output when launching a .app bundle via open, or any best practice for logging critical failures from a GUI app when terminal output isn't visible?
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192
Jun ’25
BGProcessingTaskRequest executing even after force-quit from App Switcher
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!
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187
Oct ’25
BGProcessingTask File Upload Limits
I have BGProcessingTask & BGAppRefreshTask working fine. The main purpose of my use of BGProcessingTask is to upload a file to AWS S3 using multipart/form-data. I have found that any file above about 2.5MB times out after running almost four minutes. If I run the same RESTful api using curl or Postman, I can upload a 25MB file in 3 seconds or less. I have tried to deliberately set .earliestBeginDate to 01:00 or 02:00 local time on the iPhone, but that does not seem to help. I use the delegate (yes, I am writing in Objective C) - URLSession:task:didSendBodyData:totalBytesSent:totalBytesExpectedToSend: and find that the iOS system uploads about 140kB every 15 seconds or so. I am looking for recommendations or insight into how I might enable uploads of 25MB files. I would be happy it I could do just one a day for my use case. I provide code on how I set up the NSURLSession and NSURLSessionDownloadTask, as it is my guess that if there is something that needs to be modified it is there. I have to believe there is a solution for this since I read in many posts here and in StackOverflow how developers are using this functionality for uploading many, many files. NSURLSessionConfiguration *sConf = [NSURLSessionConfiguration backgroundSessionConfigurationWithIdentifier:bkto.taskIdentifier]; sConf.URLCache = [NSURLCache sharedURLCache]; sConf.waitsForConnectivity = YES; sConf.allowsCellularAccess = NO; sConf.networkServiceType = NSURLNetworkServiceTypeVideot; sConf.multipathServiceType = NSURLSessionMultipathServiceTypeNone; sConf.discretionary = YES; sConf.timeoutIntervalForResource = kONEHOURINTERVAL; sConf.timeoutIntervalForRequest = kONEMINUTEINTERVAL; sConf.allowsExpensiveNetworkAccess = NO ; sConf.allowsConstrainedNetworkAccess = NO; sConf.sessionSendsLaunchEvents = YES; myURLSession = [NSURLSession sessionWithConfiguration:sConf delegate:self delegateQueue:nil]; And then later in the code... NSMutableURLRequest *request = [NSMutableURLRequest requestWithURL:[NSURL URLWithString:pth]]; request.HTTPMethod = kHTTPPOST; request.HTTPBody = [NSData my body data]; request.timeoutInterval = 60; [request setValue:@"*/*" forHTTPHeaderField:@"Accept"]; [request setValue:@"en-us,en" forHTTPHeaderField:@"Accept-Language"]; [request setValue:@"gzip, deflate, br" forHTTPHeaderField:@"Accept-Encoding"]; [request setValue:@"ISO-8859-1,utf-8" forHTTPHeaderField:@"Accept-Charset"]; [request setValue:@"600" forHTTPHeaderField:@"Keep-Alive"]; [request setValue:@"keep-alive" forHTTPHeaderField:@"Connection"]; NSString *contType = [NSString stringWithFormat:@"multipart/form-data; boundary=%@",bnd]; [request setValue:contType forHTTPHeaderField:@"Content-Type"]; [request addValue:[NSString stringWithFormat:@"%lu",(unsigned long)myData.length] forHTTPHeaderField:@"Content-Length"]; and here are a few lines from my logs to show the infrequent multi-part uploads of only small chunks of data by the iOS system: -[BKSessionManager URLSession:task:didSendBodyData:totalBytesSent:totalBytesExpectedToSend:]: bytesSent = 393,216 -[BKSessionManager URLSession:task:didSendBodyData:totalBytesSent:totalBytesExpectedToSend:]: totalBytesSent = 393,216 -[BKSessionManager URLSession:task:didSendBodyData:totalBytesSent:totalBytesExpectedToSend:]: task = BackgroundDownloadTask <76A81A80-4703-4686-8742-A0048EB65108>.<2>, time Fri Mar 7 16:25:27 2025 -[BKSessionManager URLSession:task:didSendBodyData:totalBytesSent:totalBytesExpectedToSend:]: bytesSent = 131,072 -[BKSessionManager URLSession:task:didSendBodyData:totalBytesSent:totalBytesExpectedToSend:]: totalBytesSent = 524,288 -[BKSessionManager URLSession:task:didSendBodyData:totalBytesSent:totalBytesExpectedToSend:]: task = BackgroundDownloadTask <76A81A80-4703-4686-8742-A0048EB65108>.<2>, time Fri Mar 7 16:25:42 2025 -[BKSessionManager URLSession:task:didSendBodyData:totalBytesSent:totalBytesExpectedToSend:]: bytesSent = 131,072 -[BKSessionManager URLSession:task:didSendBodyData:totalBytesSent:totalBytesExpectedToSend:]: totalBytesSent = 655,360 -[BKSessionManager URLSession:task:didSendBodyData:totalBytesSent:totalBytesExpectedToSend:]: task = BackgroundDownloadTask <76A81A80-4703-4686-8742-A0048EB65108>.<2>, time Fri Mar 7 16:25:56 2025 -[BKSessionManager URLSession:task:didSendBodyData:totalBytesSent:totalBytesExpectedToSend:]: bytesSent = 131,072 -[BKSessionManager URLSession:task:didSendBodyData:totalBytesSent:totalBytesExpectedToSend:]: totalBytesSent = 786,432
5
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142
Mar ’25
[iOS 26 Beta] BGTaskScheduler.supportedResources incorrectly reports no GPU support for BGContinuedProcessingTask on capable hardware
Testing Environment: iOS: 26.0 Beta 7 Xcode: Beta 6 Description: We are implementing the new BGContinuedProcessingTask API introduced in iOS 26. We have followed the official documentation and WWDC session guidance to configure our project. The Background Modes (processing) and Background GPU Access capabilities have been added in Xcode. The com.apple.developer.background-tasks.continued-processing.gpu entitlement is present and set to in the .entitlements file. The provisioning profile details viewed within Xcode explicitly show that the "Background GPU Access" capability and the corresponding entitlement are included. Despite this correct configuration, when running the app on supported hardware (iPhone 16 Pro), a call to BGTaskScheduler.supportedResources.contains(.gpu) consistently returns false. This prevents us from setting request.requiredResources = .gpu. As a result, when the BGContinuedProcessingTask starts without the GPU resource flag, our internal Metal-based exporter attempts to access the GPU and is terminated by the system, throwing an IOGPUMetalError: Insufficient Permission (to submit GPU work from background). We have performed extensive debugging, including a full reset of the provisioning profile (removing/re-adding capabilities, toggling automatic signing, cleaning build folders, and reinstalling the app), but the issue persists. This strongly suggests a bug in the iOS 26 beta where the runtime is failing to correctly validate a valid entitlement. Additionally, we've observed inconsistent behavior across devices. On an A16-based iPad, the task submits successfully (BGTaskScheduler.submit does not throw an error), but the launch handler is never invoked by the system. On the iPhone 16 Pro, the handler is invoked, but we encounter the supportedResources issue described above. This leads us to ask for clarification on the exact hardware requirements for this feature. We hypothesize that it may be limited to devices that support Apple Intelligence (A17 Pro and newer). Could you please confirm this and provide official documentation on the device support criteria? Steps to Reproduce: Create a new Xcode project. In Signing & Capabilities, add "Background Modes" (with "Background processing" checked) and "Background GPU Access". Add a permitted identifier (e.g., "com.company.test.*") to BGTaskSchedulerPermittedIdentifiers in Info.plist. In application(_:didFinishLaunchingWithOptions:) or a ViewController's viewDidLoad, log the result of BGTaskScheduler.shared.supportedResources.contains(.gpu). Build and run on a physical, supported device (e.g., iPhone 16 Pro). Expected Results: The log should indicate that BGTaskScheduler.shared.supportedResources.contains(.gpu) returns true. Actual Results: The log shows that BGTaskScheduler.shared.supportedResources.contains(.gpu) returns false.
6
0
307
1w
Helper app is sandboxed (entitlement + runtime check), but `URLsForDirectory:` returns user home (`/Users//`) instead of container path — why?
Problem summary I have a macOS helper app that is launched from a sandboxed main app. The helper: has com.apple.security.app-sandbox = true and com.apple.security.inherit = true in its entitlements, is signed and embedded inside the main app bundle (placed next to the main executable in Contents/MacOS), reports entitlement_check = 1 (code signature contains sandbox entitlement, implemented via SecStaticCode… check), sandbox_check(getpid(), NULL, 0) returns 1 (runtime sandbox enforcement present), APP_SANDBOX_CONTAINER_ID environment variable is not present (0). Despite that, Cocoa APIs return non-container home paths: NSHomeDirectory() returns /Users/&lt;me&gt;/ (the real home). [[NSFileManager defaultManager] URLsForDirectory:inDomains:] and URLForDirectory:inDomain:appropriateForURL:create:error: return paths rooted at /Users/&lt;me&gt;/ (not under ~/Library/Containers/&lt;app_id&gt;/Data/...) — i.e. they look like non-sandboxed locations. However, one important exception: URLForDirectory:... for NSItemReplacementDirectory (temporary/replacement items) does return a path under the helper's container (example: ~/Library/Containers/&lt;app_id&gt;/Data/tmp/TemporaryItems/NSIRD_&lt;helper_name&gt;_hfc1bZ). This proves the sandbox is active for some FileManager APIs, yet standard directory lookups (Application Support, Documents, Caches, and NSHomeDirectory()) are not being redirected to the container. What I expect The helper (which inherits the sandbox and is clearly sandboxed) should get container-scoped paths from Cocoa’s FileManager APIs (Application Support, Documents, Caches), i.e. paths under the helper’s container: /Users/&lt;me&gt;/Library/Containers/&lt;app_id&gt;/Data/.... What I tried / diagnostics already gathered Entitlements &amp; code signature codesign -d --entitlements :- /path/to/Helper.app/Contents/MacOS/Helper # shows com.apple.security.app-sandbox = true and com.apple.security.inherit = true Runtime checks (Objective-C++ inside helper): extern "C" int sandbox_check(pid_t pid, const char *op, int flags); NSLog(@"entitlement_check = %d", entitlement_check()); // SecStaticCode check NSLog(@"env_variable_check = %d", (getenv("APP_SANDBOX_CONTAINER_ID") != NULL)); NSLog(@"runtime_sandbox_check = %d", sandbox_check(getpid(), nullptr, 0)); NSLog(@"NSHomeDirectory = %s", NSHomeDirectory()); NSArray *urls = [[NSFileManager defaultManager] URLsForDirectory:NSApplicationSupportDirectory inDomains:NSUserDomainMask]; NSLog(@"URLsForDirectory: %@", urls); Observed output: entitlement_check = 1 env_variable_check = 0 runtime_sandbox_check = 1 NSHomeDirectory = /Users/&lt;me&gt; URLsForDirectory: ( "file:///Users/&lt;me&gt;/Library/Application%20Support/..." ) Temporary/replacement directory (evidence sandbox active for some APIs): NSURL *tmpReplacement = [[NSFileManager defaultManager] URLForDirectory:NSItemReplacementDirectory inDomain:NSUserDomainMask appropriateForURL:nil create:YES error:&amp;err]; NSLog(@"NSItemReplacementDirectory: %@", tmpReplacement.path); Observed output (example): /Users/&lt;me&gt;/Library/Containers/&lt;app_id&gt;/Data/tmp/TemporaryItems/NSIRD_&lt;helper_name&gt;_hfc1bZ Other facts Calls to NSHomeDirectory() and URLsForDirectory: are made after main() to avoid "too early" initialization problems. Helper is placed in Contents/MacOS (not Contents/Library/LoginItems). Helper is a non-GUI helper binary launched by the main app (not an XPC service). macOS version: Sequoia 15.6 Questions Why do NSHomeDirectory() and URLsForDirectory: return the real /Users/&lt;me&gt;/... paths in a helper process that is clearly sandboxed (entitlement + runtime enforcement), while NSItemReplacementDirectory returns a container-scoped temporary path? Is this behavior related to how the helper is packaged or launched (e.g., placement in Contents/MacOS vs Contents/Library/LoginItems, or whether it is launched with posix_spawn/fork+exec vs other APIs)? Are there additional entitlements or packaging rules required for a helper that inherits sandbox to have Cocoa directory APIs redirected to the container (for Application Support, Documents, Caches)? *Thanks in advance — I can add any requested logs
6
0
164
Sep ’25
NSTask-launch path not accessible
I'm trying to launch a command line app from my objective C application (sandboxed) using NSTask and I keep getting "launch path not accessible" Here is the path: [task setLaunchPath:@"/usr/local/bin/codeview"]; I have set the appropriate attributes for codeview and it is working perfectly when I use it from the command line and /usr/local/bin IS in the $PATH I know I have NSTask configured correctly because this WILL work: [task setLaunchPath:@"/usr/bin/hexdump"]; With the exception being that I'm using a command already in /usr/bin. But I can't copy codeview into /usr/bin due to SIPS. I've tried moving codeview to various other non-SIPS protected locations all to no avail. Must all NSTask commands come from /usr/bin? Where might I put codeview so that it can be launched. Today I'm going to use an older computer and disable SIPS to put my command in /usr/bin and see if that works. If it does. I will do it on my main machine.
6
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169
Apr ’25