macOS 26 "Tahoe" is allocating much more memory for apps than former macOS versions: A customer contacted me with my app's Thumbnail extension allocating so much memory that her 48 GB RAM Mac Mini ran into "out of application memory" state. I couldn't identify any memory leak in my extension's code nor reproduce the issue, but found the main app allocating as much as 5 times the memory compared to running on macOS 15 or lower. This productive app is explicitly using "Liquid Glass" views as well as implicitly e.g. for an inspector pane. So I created a sample app, just based on Xcode's template of a document-based app, and the issue is still showing (although less dramatically): This sample app allocates 22 MB according to Tahoe's Activity Monitor, while Sequoia only requires 16 MB: macOS 15.6.1 macOS 26.2 Is anyone experiencing similar issues? I suspect some massive leak in Tahoe's memory management, and just filed a corresponding feedback (FB21967167).

Hi, I’m working on a macOS app that includes a file browser component. And I’m trying to match Finder’s behavior for color tags and folder icons. For local files/folders everything works fine: Tag color key returns the expected label number via NSColor * labelColor = nil; [fileURL getResourceValue:&labelColor forKey:NSURLLabelColorKey error:nil]; NSNumber * labelKey = nil; [fileURL getResourceValue:&labelKey forKey:NSURLLabelNumberKey error:nil]; QLThumbnailGenerator obtains the expected colored folder icon (including emoji/symbol overlay if set) via QLThumbnailGenerationRequest * request = [[QLThumbnailGenerationRequest alloc] initWithFileAtURL:fileURL size:iconSize scale:scaleFactor representationTypes:QLThumbnailGenerationRequestRepresentationTypeIcon]; request.iconMode = YES; [[QLThumbnailGenerator sharedGenerator] generateBestRepresentationForRequest:request completionHandler:^(QLThumbnailRepresentation * _Nullable thumbnail, NSError * _Nullable error) { if (thumbnail != nil && error == nil) { NSImage * thumbnailImage = [thumbnail NSImage]; // ... } }]; However, for items on iCloud Drive (whether currently downloaded locally or only stored in the cloud), the same code always produces gray colors, while Finder shows everything correctly: NSURLLabelNumberKey always returns 1 (gray) for items with color tags, and 0 for non-tagged. Folder icons returned via QLThumbnailGenerator are gray, no emoji/symbol overlays. Reading tag data from xattr gives values like “Green\1” (tag name matches, but numeric value is still "Gray"). Also, if I move a correctly-tagged local item into iCloud Drive, it immediately becomes gray in my app (Finder still shows the correct colors). Question: What is the supported way to retrieve Finder tag colors and the correct folder icon appearance (color + overlays) for items in iCloud Drive, so that the result matches Finder? I am on macOS Tahoe 26.2/26.3, Xcode 26.2 (17C52). If you need any additional details, please let me know. Thanks!

On macOS 26, I've run into a situation when a user “customizes” a folder icon with Finder by assigning/changing an SF Symbol or an emoji, QLThumbnailGenerator keeps returning the stale initially retrieved folder icon (no matter whether it had been customized or not) until my app quits. After the app is re-launched, the icon is correctly retrieved once again. let generator = QLThumbnailGenerator.shared let size: CGSize = CGSize(width: 64, height: 64) let request = QLThumbnailGenerator.Request(fileAt: url, size: size, scale: NSScreen.main!.backingScaleFactor, representationTypes: .icon) request.iconMode = true do { let thumb = try await generator.generateBestRepresentation(for: request) thumb.nsImage.size = size return thumb.nsImage } catch { print("generateThumbnail: \(error)") return nil } It seems like the QuickLook Thumbnailing cache does not invalidate automatically upon folder customization. Is there any way to manually invalidate the QuickLook Thumbnailing cache?

I'm implementing the 'new' QLThumbnailProvider for our macOS app... So I just created the skeleton from Xcode, added our QLSupportedContentTypes in Info.plist, and have the skeleton code like below: import QuickLookThumbnailing class ThumbnailProvider: QLThumbnailProvider { override func provideThumbnail(for request: QLFileThumbnailRequest, _ handler: @escaping (QLThumbnailReply?, Error?) -> Void) { // cannot trigger break point here! } I understand I should test the Thumbnail Extension by using: $ qlmanage -t my_file.ext Testing Quick Look thumbnails with files: my_file.ext But I don't know what process to attach to in the Xcode debugger... a bit clueless... I've skimmed relevant parts of https://developer.apple.com/videos/play/wwdc2019/719, but there is no real debug tips... Does anyone know if it is possible to debug with Xcode or not? And if possible, then how? 😅

I'm facing the same problem as addressed in this discussion: After switching from legacy QLGenerators to Preview extensions on macOS I cannot debug the extensions' code in Xcode, anymore: I launch the app with the embedded appex from Xcode in debug mode. When trying to attach to the appex process the following error is reported: Code: 6 Failure Reason: Ensure “AppName Preview” is not already running, and matthias has permission to debug it. User Info: {... } System Information macOS Version 15.4.1 (Build 24E263) Xcode 16.3 (23785) (Build 16E140) Timestamp: 2025-05-12T14:07:14+02:00 I'm using a standard user account (no admin) and might miss some obvious steps. Can someone detail the steps to debug a Preview (or Thumbnail) extension with Xcode 16? For legacy Quick Look plugins I was using "qlmanage", but that's not working on extensions. All the best, Matthias P.S.: Pardon me re-posting my reply as a separate thread, to increase visibility, but I'm quite desperate and couldn't find any solution on the web...