For context, my company develops a data loss prevention (DLP) product. Part of our functionality is the ability to detect sensitive data being pasted into a web browser or cloud-based app. The AppKit release notes for April 2025 document an upcoming “macOS pasteboard privacy” feature, which will presumably ship in macOS 26. Using the user default setting “EnablePasteboardPrivacyDeveloperPreview” documented in the release notes, I tested our agent under macOS 15.5, and encountered a modal alert reading " is trying to access the pasteboard" almost immediately, when the program reads the General pasteboard to scan its contents. Since our product is aimed at enterprise customers (and not individual Mac users), I believed Apple would implement a privacy control setting for this new feature. This would allow our customers to push a configuration profile via MDM, with the “Paste from Other Apps” setting for our application preset to “Allow”, so that they can install our product on their endpoints without manual intervention. Unfortunately, as of macOS 26 beta 4 (25A5316i), there does not seem to be any such setting documented under Device Management — for example in PrivacyPreferencesPolicyControl.Services, which lists a number of similar settings. Without such a setting available, a valuable function of our product will be effectively crippled when macOS 26 is released. Is there such a setting (that I've overlooked)? If not, allow me to urge Apple to find the resources to implement one, so that our customers can preset “Paste from Other Apps” to “Allow” for our application.

What are the SwiftUI equivalent of NSSplitViewController.automaticallyAdjustsSafeAreaInsets NSToolbarItem.style These were introduced in the WWDC 2025 session named "Build an AppKit app with the new design". Jeff introduced only the AppKit API's while there was no mention of SwiftUI API

In macOS 26 beta 2 it is possible to set an edge effect style via UIKit using the .scrollEdgeEffectStyle property. (note: I haven't tested this, I'm just looking at the documentation). See: https://developer.apple.com/documentation/swiftui/view/scrolledgeeffectstyle(_:for:) Is there an equivalent API for AppKit-based apps? I can't seem to find any additions in NSView or NSScrollView or elsewhere that seem relevant. Scroll edge effects are mentioned in the "Build an AppKit app with the new design" talk here, which heavily implies it must be possible from AppKit: https://developer.apple.com/videos/play/wwdc2025/310/?time=567

According the video "Build an AppKit app with the new design" (https://developer.apple.com/videos/play/wwdc2025/310/), it is now possible to add a badge on a NSToolbarItem object. However, in don't see a badge in the NSToolbar API. The code example in the video includes for example "NSItemBadge.count(4)", but the only Google result for this is the video mentioned above. Is this still work in progress or I'm overlooking something?

Is there a SwiftUI version of NSControl.allowsExpansionToolTips? That is, showing a tool tip with the full text when (and only when) a text item is truncated? Or do I need to use a hosting view to get that behavior?

For months now we're trying to find an issue with one of our apps, were a window suddenly becomes narrow and can't be resized horizontally any more. It's a bug that only happens sporadically and we can't provide a "focused test project" to demonstrate the issue; thus we can't ask for code-level support at this moment. To debug this issue, we've overwritten a private method on NSWindow that gets the constrained window min and max sizes (valuable hint of Kristin from the AppKit team in a WWDC 2025 one-on-one session where I was able to show it to her in my debugger). When the bug hits, the maxSize's width (usually 10000) becomes smaller than the minSize's width. One way (but not the only one) to trigger this issue is to move the window from one display to another and back. Sometimes the bug triggers after a few back-and-forth movements, sometimes it takes minutes to trigger or I give up… but for other people the bug happens seemingly out of nowhere (of course there must be a trigger but we haven't noticed common patterns yet). It looks like an AutoLayout issue since a suspicious thing happens when the bug triggers: calling constraintsAffectingLayoutForOrientation:NSLayoutConstraintOrientationHorizontal on the NSThemeFrame usually returns just two constraints. But when the bug triggers, it returns a whole bunch of constraints, related to all kind of views of our app. Asking the NSThemeFrame for its direct constraints still shows the same two constraints are present and active (NSWindow-current-width and NSWindow-x-anchor). How to proceed in hunting down this issue when we're unable to produce a demo project? We can only reproduce the bug with our big product, and only sporadically: sometimes I can trigger it in a minute, sometimes it takes me 15 minutes or even more. Issue happens on macOS 15 (currently running 15.5).

My app supports different plain text file formats, including the standard .txt and Markdown. When creating a new document, my app already asks which format it should have, so when saving it, I would expect that the save panel already selects that format in the popup button, but currently it always selects "Plain Text". For example, I would expect for a Markdown document that it selects "Markdown" instead of "Plain Text". Is there a way to force it to select the most specific format matching the document format?

I have the following method to insert @mentions to a text field: func insertMention(user: Token, at range: NSRange) -> Void { let tokenImage: UIImage = renderMentionToken(text: "@\(user.username)") let attachment: NSTextAttachment = NSTextAttachment() attachment.image = tokenImage attachment.bounds = CGRect(x: 0, y: -3, width: tokenImage.size.width, height: tokenImage.size.height) attachment.accessibilityLabel = user.username attachment.accessibilityHint = "Mention of \(user.username)" let attachmentString: NSMutableAttributedString = NSMutableAttributedString(attributedString: NSAttributedString(attachment: attachment)) attachmentString.addAttribute(.TokenID, value: user.id, range: NSRange(location: 0, length: 1)) attachmentString.addAttribute(.Tokenname, value: user.username, range: NSRange(location: 0, length: 1)) let mutableText: NSMutableAttributedString = NSMutableAttributedString(attributedString: textView.attributedText) mutableText.replaceCharacters(in: range, with: attachmentString) mutableText.append(NSAttributedString(string: " ")) textView.attributedText = mutableText textView.selectedRange = NSRange(location: range.location + 2, length: 0) mentionRange = nil tableView.isHidden = true } When I use XCode's accessibility inspector to inspect the text input, the inserted token is not read by the inspector - instead a whitespace is shown for the token. I want to set the accessibility-label to the string content of the NSTextAttachment. How?

For many years I've had the following code to access the active objects of a table view in my App Store app: class MyViewController: NSViewController: NSMenuItemValidation { private var tableView: NSTableView! private var objects = [MyObject]() func numberOfRows(in tableView: NSTableView) -> Int { return objects.count } func tableView(_ tableView: NSTableView, viewFor tableColumn: NSTableColumn?, row: Int) -> NSView? { // make view for row } private var activeObjects: [MyObject] { return tableView?.activeRowIndexes.map({ objects[$0] }) ?? [] } func validateMenuItem(_ menuItem: NSMenuItem) -> Bool { let activeObjects = self.activeObjects ... } } extension NSTableView { var activeRowIndexes: IndexSet { return clickedRow == -1 || selectedRowIndexes.contains(clickedRow) ? selectedRowIndexes : IndexSet(integer: clickedRow) } } In one of the recent updates, I wanted to add some kind of header to the table view, so I decided to add a row at the beginning and offset the indexes by 1. func numberOfRows(in tableView: NSTableView) -> Int { return objects.count + 1 } func tableView(_ tableView: NSTableView, viewFor tableColumn: NSTableColumn?, row: Int) -> NSView? { if row == 0 { // make header view } else { // make view for row - 1 } } private var activeObjects: [MyObject] { return tableView?.activeRowIndexes.subtracting(IndexSet(integer: 0)).map({ objects[$0 - 1] }) ?? [] } But since I added this change, Xcode regularly downloads crash reports from clients crashing during menu item validation in IndexSet.map with reason Code 5 Trace/BPT trap: 5. I assumed that I was accessing an invalid array index, so I added some debug code: the crash report would then show the invalid index beside the crashed thread's name. private var activeObjects: [MyObject] { return tableView?.activeRowIndexes.subtracting(IndexSet(integer: 0)).map({ i in if !objects.indices.contains(i - 1) { Thread.current.name = (Thread.current.name ?? "") + ". Invalid index \(i - 1) for count \(objects.count)" preconditionFailure() } return objects[i - 1] }) ?? [] } But the crash reports for this new app version look just like the old ones and the thread name is not changed. Indeed, when recreating an invalid index access on my Mac, the crash report mentions Array._checkSubscript(_:wasNativeTypeChecked:), which does not appear in the crash reports downloaded by Xcode. Manually symbolicating the crash report also doesn't give any more information: all lines referring to my app code are resolved to either /<compiler-generated>:0 or MyViewController.swift:0. Apparently the problem is not an invalid array index, but something else. Does anybody have a clue what the problem could be? (Note: the crash report mentions Sequence.compactMap because now I'm effectively calling tableView?.activeRowIndexes.compactMap, but the same crash happened before when calling IndexSet.map, which would appear in the crash report as Collection.map.) crash2.crash

After I upgraded to MacOS 26（beta）, my program caused the system to pop up a window as shown in the following picture. My application is a process with only a tray icon. I found that my tray icon is not displayed in the current version, even though I clicked the "Always Allow" button. Here are my questions: 1.Will this related feature remain consistent in the official release? 2.How can I create a cmd process that only displays a system tray icon (no main window) like Alfred?

If I create a bitmap image and then try to get ready to draw into it, like so: NSBitmapImageRep* newRep = [[NSBitmapImageRep alloc] initWithBitmapDataPlanes: nullptr pixelsWide: 128 pixelsHigh: 128 bitsPerSample: 8 samplesPerPixel: 4 hasAlpha: YES isPlanar: NO colorSpaceName: NSDeviceRGBColorSpace bitmapFormat: NSBitmapFormatAlphaNonpremultiplied | NSBitmapFormatThirtyTwoBitBigEndian bytesPerRow: 4 * 128 bitsPerPixel: 32]; [NSGraphicsContext setCurrentContext: [NSGraphicsContext graphicsContextWithBitmapImageRep: newRep]]; then the log shows this error: CGBitmapContextCreate: unsupported parameter combination: RGB 8 bits/component, integer 512 bytes/row kCGImageAlphaLast kCGImageByteOrderDefault kCGImagePixelFormatPacked Valid parameters for RGB color space model are: 16 bits per pixel, 5 bits per component, kCGImageAlphaNoneSkipFirst 32 bits per pixel, 8 bits per component, kCGImageAlphaNoneSkipFirst 32 bits per pixel, 8 bits per component, kCGImageAlphaNoneSkipLast 32 bits per pixel, 8 bits per component, kCGImageAlphaPremultipliedFirst 32 bits per pixel, 8 bits per component, kCGImageAlphaPremultipliedLast 32 bits per pixel, 10 bits per component, kCGImageAlphaNone|kCGImagePixelFormatRGBCIF10|kCGImageByteOrder16Little 64 bits per pixel, 16 bits per component, kCGImageAlphaPremultipliedLast 64 bits per pixel, 16 bits per component, kCGImageAlphaNoneSkipLast 64 bits per pixel, 16 bits per component, kCGImageAlphaPremultipliedLast|kCGBitmapFloatComponents|kCGImageByteOrder16Little 64 bits per pixel, 16 bits per component, kCGImageAlphaNoneSkipLast|kCGBitmapFloatComponents|kCGImageByteOrder16Little 128 bits per pixel, 32 bits per component, kCGImageAlphaPremultipliedLast|kCGBitmapFloatComponents 128 bits per pixel, 32 bits per component, kCGImageAlphaNoneSkipLast|kCGBitmapFloatComponents See Quartz 2D Programming Guide (available online) for more information. If I don't use NSBitmapFormatAlphaNonpremultiplied as part of the format, I don't get the error message. My question is, why does the constant NSBitmapFormatAlphaNonpremultiplied exist if you can't use it like this? If you're wondering why I wanted to do this: I want to extract the RGBA pixel data from an image, which might have non-premultiplied alpha. And elsewhere online, I saw advice that if you want to look at the pixels of an image, draw it into a bitmap whose format you know and look at those pixels. And I don't want the process of drawing to premultiply my alpha.

I use NSTextView in my app, and I am getting a LOT of crashes when I’m running the app with the debugger attached, and it all points to this spell checker in NSTextView. The crash happens as soon as the textview shows the ‘word completion’ option. If I turn off the “Continuous Spell Checking” option, it works fine, and it doesn’t crash. The exception reason given is: __NSCFString * "NSMutableRLEArray objectAtIndex:effectiveRange:: Out of bounds" This is what the stack trace looks like in Xcode: Thread 1 Queue : com.apple.main-thread (serial) #0 0x000000018335eb38 in objc_exception_throw () #1 0x0000000184e01910 in -[NSRLEArray objectAtIndex:effectiveRange:] () #2 0x0000000184e519a8 in -[NSMutableAttributedString addAttribute:value:range:] () #3 0x000000018818086c in -[NSText(NSTextAccessibilityPrivate) accessibilityAXAttributedStringForCharacterRange:parent:] () #4 0x0000000187f576b0 in -[NSAccessibilityAttributeAccessorInfo getParameterizedAttributeValue:forObject:withParameter:] () #5 0x0000000187f591a8 in ___NSAccessibilityEntryPointValueForAttributeWithParameter_block_invoke.799 () #6 0x0000000187f5458c in NSAccessibilityPerformEntryPointObject () #7 0x0000000187f56190 in NSAccessibilityEntryPointValueForAttributeWithParameter () #8 0x0000000187cb6a3c in CopyParameterizedAttributeValue () #9 0x00000002327057ac in ___lldb_unnamed_symbol4511 () #10 0x0000000232705854 in ___lldb_unnamed_symbol4512 () #11 0x000000018a5b3670 in _AXXMIGCopyParameterizedAttributeValue () #12 0x000000018a5d4894 in _XCopyParameterizedAttributeValue () #13 0x000000018a592ff8 in mshMIGPerform () #14 0x000000018382a250 in __CFRUNLOOP_IS_CALLING_OUT_TO_A_SOURCE1_PERFORM_FUNCTION__ () #15 0x000000018382a178 in __CFRunLoopDoSource1 () #16 0x0000000183828b78 in __CFRunLoopRun () #17 0x0000000183827c58 in CFRunLoopRunSpecific () #18 0x000000018f2bc27c in RunCurrentEventLoopInMode () #19 0x000000018f2bf4e8 in ReceiveNextEventCommon () #20 0x000000018f44a484 in _BlockUntilNextEventMatchingListInModeWithFilter () #21 0x000000018774fab4 in _DPSNextEvent () #22 0x00000001880ee5b0 in -[NSApplication(NSEventRouting) _nextEventMatchingEventMask:untilDate:inMode:dequeue:] () #23 0x00000001884b836c in -[NSCorrectionPanel _interceptEvents] () #24 0x00000001884b8f30 in -[NSCorrectionPanel showPanelAtRect:inView:primaryString:alternativeStrings:forType:completionHandler:] () #25 0x00000001880c91ec in -[NSSpellChecker showCorrectionIndicatorOfType:range:primaryString:alternativeStrings:forStringInRect:view:completionHandler:] () #26 0x00000001880ca0c0 in -[NSSpellChecker _showInlinePredictionForReplacingRange:markedRange:string:withString:view:client:lastReplacementRange:completeWordIndexes:resultDictionary:completionHandler:] () #27 0x00000001880cb26c in -[NSSpellChecker showCompletionForCandidate:selectedRange:offset:inString:rect:view:client:completionHandler:] () #28 0x0000000188303a94 in -[NSTextCheckingController handleCompletionFromCandidates:forSelectedRange:offset:inAnnotatedString:rect:view:] () #29 0x00000001882f9054 in -[NSTextCheckingController viewForRange:completionHandler:] () #30 0x00000001883041c8 in __60-[NSTextCheckingController handleCandidates:sequenceNumber:]_block_invoke () #31 0x000000018789105c in -[NSTextCheckingController annotatedSubstringForProposedRange:wrap:completionHandler:failureHandler:] () #32 0x0000000187890da4 in -[NSTextCheckingController annotatedSubstringForProposedRange:completionHandler:] () #33 0x00000001878927d4 in -[NSTextCheckingController annotatedSubstringForSelectedRangeWithCompletionHandler:] () #34 0x0000000188304134 in -[NSTextCheckingController handleCandidates:sequenceNumber:] () #35 0x00000001883067e0 in ___NSRunLoopTimerCreateWithHandler_block_invoke () #36 0x0000000183842e14 in __CFRUNLOOP_IS_CALLING_OUT_TO_A_TIMER_CALLBACK_FUNCTION__ () #37 0x0000000183842ad4 in __CFRunLoopDoTimer () #38 0x0000000183842610 in __CFRunLoopDoTimers () #39 0x0000000183828a18 in __CFRunLoopRun () #40 0x0000000183827c58 in CFRunLoopRunSpecific () #41 0x000000018f2bc27c in RunCurrentEventLoopInMode () #42 0x000000018f2bf4e8 in ReceiveNextEventCommon () #43 0x000000018f44a484 in _BlockUntilNextEventMatchingListInModeWithFilter () #44 0x000000018774fab4 in _DPSNextEvent () #45 0x00000001880ee5b0 in -[NSApplication(NSEventRouting) _nextEventMatchingEventMask:untilDate:inMode:dequeue:] () #46 0x0000000187742c64 in -[NSApplication run] () #47 0x000000018771935c in NSApplicationMain () If I run the debug version of the app without the debugger, it works fine as well. In fact, if I run the app without "All Objective-C Exceptions" breakpoint, it also works fine. So it seems like some framework issue, which is making it hard to run and test my app. What’s the reason for this, and is this an issue I should be worried about for when the app is available to my users?

In my app I have a background task performed on a custom DispatchQueue. When it has completed, I update the UI in DispatchQueue.main.async. In a particular case, the app then needs to show a modal window that contains a table view, but I have noticed that when scrolling through the tableview, it only responds very slowly. It appears that this happens when the table view in the modal window is presented in DispatchQueue.main.async. Presenting it in perform(_:with:afterDelay:) or in a Timer.scheduledTimer(withTimeInterval:repeats:block:) on the other hand works. Why? This seems like an ugly workaround. I created FB7448414 in November 2019 but got no response. @NSApplicationMain class AppDelegate: NSObject, NSApplicationDelegate { func applicationDidFinishLaunching(_ aNotification: Notification) { let windowController = NSWindowController(window: NSWindow(contentViewController: ViewController())) // 1. works // runModal(for: windowController) // 2. works // perform(#selector(runModal), with: windowController, afterDelay: 0) // 3. works // Timer.scheduledTimer(withTimeInterval: 0, repeats: false) { [self] _ in // self.runModal(for: windowController) // } // 4. doesn't work DispatchQueue.main.async { self.runModal(for: windowController) } } @objc func runModal(for windowController: NSWindowController) { NSApp.runModal(for: windowController.window!) } } class ViewController: NSViewController, NSTableViewDataSource, NSTableViewDelegate { override func loadView() { let tableView = NSTableView() tableView.dataSource = self tableView.delegate = self tableView.addTableColumn(NSTableColumn()) let scrollView = NSScrollView(frame: CGRect(x: 0, y: 0, width: 400, height: 400)) scrollView.documentView = tableView scrollView.hasVerticalScroller = true scrollView.translatesAutoresizingMaskIntoConstraints = false view = scrollView } func numberOfRows(in tableView: NSTableView) -> Int { return 100 } func tableView(_ tableView: NSTableView, viewFor tableColumn: NSTableColumn?, row: Int) -> NSView? { let view = NSTableCellView() let textField = NSTextField(labelWithString: "\(row)") textField.translatesAutoresizingMaskIntoConstraints = false view.addSubview(textField) NSLayoutConstraint.activate([textField.leadingAnchor.constraint(equalTo: view.leadingAnchor), textField.trailingAnchor.constraint(equalTo: view.trailingAnchor), textField.topAnchor.constraint(equalTo: view.topAnchor), textField.bottomAnchor.constraint(equalTo: view.bottomAnchor)]) return view } }

In UIKit, UIButton provides a configuration property which allows us to create and customize a UIButton.Configuration instance independently (on a background thread or elsewhere) and later assign it to a UIButton instance. This separation of configuration and assignment is very useful for clean architecture and performance optimization. Questions: Is this configuration-style pattern (creating a configuration object separately and assigning it later) available or planned for other UIKit components such as UILabel, UITextField, UISlider, etc.? Similarly, in AppKit on macOS, are there any components (e.g. NSButton, NSTextField) that support a comparable configuration object mechanism that can be used the same way — constructed separately and assigned to the view later? This would help in building consistent configuration-driven UI frameworks across Apple platforms. Any insight or official guidance would be appreciated.

I noticed that sometimes TextKit2 decides to crop some text instead of soft-wrapping it to the next line. This can be reproduced by running the code below, then resizing the window by dragging the right margin to the right until you see the text with green background (starting with “file0”) at the end of the first line. If you now slowly move the window margin back to the left, you’ll see that for some time that green “file0” text is cropped and so is the end of the text with red background, until at some point it is soft-wrapped on the second line. I just created FB18289242. Is there a workaround? class ViewController: NSViewController { override func loadView() { let textView = NSTextView(frame: CGRect(x: 0, y: 0, width: 400, height: 400)) let string = NSMutableAttributedString(string: "file0\t143548282\t1970-01-01T00:00:00Z\t1\t1f40fc92da241694750979ee6cf582f2d5d7d28e18335de05abc54d0560e0f5302860c652bf08d560252aa5e74210546f369fbbbce8c12cfc7957b2652fe9a75", attributes: [.foregroundColor: NSColor.labelColor, .backgroundColor: NSColor.red.withAlphaComponent(0.2)]) string.append(NSAttributedString(string: "file0\t143548290\t1970-01-01T00:05:00Z\t 2\t0f6460d0ed7825fed6bda0f4d9c14942d88edc7ff236479212e69f081815e6f1742c272753b77cc6437f06ef93a46271c6ff9513c68945075212434080e60c82", attributes: [.foregroundColor: NSColor.labelColor, .backgroundColor: NSColor.green.withAlphaComponent(0.2)])) textView.textContentStorage!.textStorage!.setAttributedString(string) textView.autoresizingMask = [.width, .height] let scrollView = NSScrollView(frame: CGRect(x: 0, y: 0, width: 400, height: 400)) scrollView.documentView = textView scrollView.hasVerticalScroller = true scrollView.translatesAutoresizingMaskIntoConstraints = false view = scrollView } }

Hi everyone, I’m new to macOS development and working on an app idea that needs a timeline-based editor interface, similar to what you see in Logic Pro or Final Cut. The UI I want to build would have: A horizontal beat ruler that follows BPM and shows beat positions Several vertical tracks stacked below it (for things like events or markers) Horizontal zooming and scrolling A preview panel on the right side that stays in sync with the timeline I’m currently trying this in SwiftUI, but I’m running into some limitations and wondering if AppKit would be a better fit, or maybe a hybrid of the two. My questions: Where should I start when building something like this? What’s the best way to make the beat ruler and all track layers scroll together? How should I handle zooming in/out and syncing the display to a BPM timeline? Is there a clean way to integrate AppKit for the timeline view while keeping SwiftUI elsewhere?

We ran into a bug with our app Bezel (https://getbezel.app). When running on macOS Tahoe, windows would get partially clipped. This is because we have SwiftUI views that are larger than the window size, our SwiftUI views are supposed to be centered, which they are on macOS 13, 14, 15. But on macOS 26 (beta 1), the window contents are top-left aligned. This seems to be a bug, I have submitted FB18201269. This is my code: WindowGroup { ZStack { Color.green ZStack { Color.yellow Text("Hi") } .aspectRatio(1, contentMode: .fill) .border(.red) } } This first screenshot shows the old behavior on macOS 15: This second screenshot shows the new behavior on macOS 26 (beta 1) Can anyone confirm if this is indeed a bug, or if this an intended change in behavior?

Is it not possible to dynamically change or constrain an NSPreferencePane's mainView size? I have looked all over and this doesn't seem to be mentioned anywhere. The most I can seemingly do is set the frame and hope the user doesn't resize the window. class scor: NSPreferencePane { override func mainViewDidLoad() { mainView = NSHostingView(rootView: ContentView()) mainView.frame = NSMakeRect(0, 0, 668, 1048) } } Here is a screenshot, just with a simple webview as a test, note the scrollbar: My storyboard is just from the default prefpane Xcode template, nothing special. I looked at the header file for NSPreferencePane and came up with nothing. All I can think of is that this is impossible due to the way they are implemented? The only thing we seemingly have access to is mainView, so I can't like constrain the size of mainView to its parent, for example. Additionally, if I make a new preference pane, and make a button or other view that I choose to resize to fill horizontally and vertically, it does that, but not really? Here is what that looks like: The behaviour is similar to the previous preference pane, the width does adapt correctly, the height stays the same, forever. Not that it really matters but I am using macOS 14.7.6 on an M2 air

When exporting an icon using Icon Composer Beta for macOS 26, a light, dark and tinted versions for macOS are created, but I was not able to find how to use them on the Xcode Project. I also tried finding something pointing to that on documentation, but I was not able to find anything. I see that system apps have light, dark and tinted versions on the first beta of macOS 26, which leads me to believe it would be possible for third-party apps to do that same.

In a previous post entitled “Save fails after Save As” I described a strange problem involving the Save and Save As operations in a macOS app I wrote: see https://developer.apple.com/forums/thread/779755. Since that posting (unanswered up to now) I tried various modifications of my app, in order better to understand the problem. Now, at the time of that posting I was using a version of the app that attempted — clumsily and incompletely — to circumvent the problem. Since then I decided to eliminate from my app this unsuccessful workaround. My app is called Goperfekt (it’s in the App Store) and is meant for macOS 11 to 15. I recently created a “bare bones” version of the app: this bare-bones version is called Goperf and contains the bare minimum necessary to save and open files of the exact same two file types as in Goperfekt, namely gop (an exported type that conforms to public.data), sgf (an imported type that conforms to public.text). Goperf and Goperfekt both use dataAfType:error: as their writing method. (Yes, Objective-C… but I’ve been working on that app on and off for nearly twenty years and when Swift came out my Obj-C project was already too advanced…) The problem is the following. In Goperfekt under macOS 15 the Save and Save As operations do not work as they should (see description below). In Goperfekt under macOS 12 and 11 the Save and Save As operations work perfectly, just as they should. (Unfortunately I do not have machines running macOS 14 or 13 at the moment.) Goperf, the bare-bones version, on the other hand, works perfectly in all three versions of macOS that I have (11, 12, 15). Here is a description of the problem with Goperfekt under macOS 15. The precise app behavior described below presupposes that the user has activated the option System Settings/Desktop & Dock/Windows/Ask to keep changes when closing documents. If you deactivate this option, the app misbehaves similarly, though somewhat differently. First three important facts (Goperfekt and Goperf in macOS 11, 12, 15): I can open an already existing gop file, modify the document, and save it in that gop file, or save it as another gop file, without any problem. I can also open an already existing sgf file, modify the document, and save it in that sgf file, or save it as another sgf file, without any problem. I can also save a new document as a gop file. BUT in Goperfekt in macOS 15 it is possible neither to save a new document as an sgf file, nor to open a gop file and save it as an sgf file, IN CASES 1 AND 2 the parameter typeName received by dataOfType:error: is not “com.red-bean.sgf” (corresponding to the imported sgf extension) as it should, but “com.florrain.goperfekt-document” (corresponding to the exported gop extension). The result is a file with the sgf extension (such as “A.sgf”, as specified in the save panel), but this file is really a gop file with the wrong extension! You can see that by asking Goperfekt to open “A.sgf” (which will generate an alert), or by opening "A.sgf” in TextEdit. You can also add .gop to the name “A.sgf” and then ask Goperfekt to open “A.sgf.gop”, which it will do without a problem. Nor is it possible to open an sgf file and save it as a gop file. Here the parameter typeName received by dataOfType:error: is not “com.florrain.goperfekt-document” (the exported type) as it should, but “com.red-bean.sgf” (the imported type). The result is a file with the gop extension (such as “A.gop”, as specified in the save panel), but this file is really an sgf file with the wrong extension! You can see that by asking Goperfekt to open “A.gop” (which will generate an alert), or by opening "A.gop” in TextEdit. You can also add .sgf to the name “A.gop” and then ask Goperfekt to open “A.gop.sgf”, which it will do without a problem. Somewhere behind the scenes (only in Goperfekt on macOS 15) NSDocument disregards what was specified by the user in the save panel and sends to dataAfType:error: the wrong file type! Why on Earth? If, after having created a file “A.sgf” that is really a gop file, I change something in the document and try to save this change in “A.sgf”, the system displays a somewhat puzzling alert, and diagnostic messages appear in the Xcode console. According to the circumstances, these messages can contain such puzzling labels as NSFileSandboxingRequestRelatedItemExtension or NSFileCoordinator. Similarly for a file “A.gop” that is really an sgf file. Conclusion: search as I may, I could not find what makes Goperfekt misbehave in macOS 15 but not in macOS 11 or 12, while the bare-bones Goperf behaves perfectly in all three versions.