NSToolbar items don’t react to Dark Mode changes in apps compiled with macOS 15 SDK: My app was installed as a notarized app on a Tahoe VM with the same build as distributed in the App Store, based on macOS 15 SDK. When toggling Dark Mode, toolbar items are not updated, but only after opening a new window / tab or e.g. customizing the toolbar. The app is using default methods for the toolbar, defined in its corresponding XIB file, and working in previous macOS versions. This issue could be confirmed with various apps built with an SDK prior to macOS 26 "Tahoe", e.g. Apple's Clipboard Viewer. Reported via Feedback Assistent (FB19107572).

Just posted this feedback regarding macOS 26 "Tahoe" (FB19853155) - please support with additional submissions if you share my view. I will miss the beautiful and individual designed icons of the past! "macOS 26 is enforcing squicles for app icons, falling back to a grey background for 3rd party apps without a compliant AppIcon asset. As a result many original app icons are reduced in size and hard to distinguish because they share the same background color. Although I respect Apple's strive for an iOS-like UI on Macs, a smooth transition path would be more user- and developer-friendly ... e.g. with some info.plist property to opt-out icon migration, potentially ignored by a future macOS version. The current solution causes a bad usability, and makes the system look inconsistent as many - especially free - software will not be updated with new icon designs. Please reconsider this bad design decision!"

When disabling the opacity slider of color panels, my app crashes with unsatisfiable layout constraints. Feel free reproduce with a minimal test project: A macOS app based on the Xcode 26.0 template with only one line added to the ViewController's viewDidLoad() function: NSColorPanel.shared.showsAlpha = false The issue doesn't occur if this property is set to "true" or not set at all. I just filed a corresponding bug report (FB20269686), although I don't expect any feedback from Apple ... as numerous issues I reported were never updated or commented at all (after migrating from RADARs).

When I compiled my legacy project with Tahoe's macOS 26 SDK, NSRulerViews are showing a very different design: Under prior macOS versions the horizontal and verrical ruler's background were blurring the content view, which was extending under the rulers, showing through their transparency. With Tahoe the horizontal ruler is always reflecting the scrollview's background color, showing the blurred content view beneath. And the vertical ruler is always completely transparent (without any blurring), showing the content together with the ruler's markers and ticks. It's difficult to describe, I'll try to replicate this behavior with a minimal test project, and probably file a bug report / enhancement request. But before I take next steps, can anyone confirm this observation? Maybe it is an intentional design decision by Apple?

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).

These days I've observed a strange behavior in my document-based app on macOS: Its NSDocument class implementation is overwriting "saveToURL:ofType:forSaveOperation:completionHandler:", performing some additional checks and calling super by passing the original parameters. As my app is supporting various file formats for writing (and exporting those UTIs) the user can open a file in one format and save it to another. NSDocument is calling the mentioned methods implicitly after completing the "Save as..." dialog. If this happens, the passed-on fileType is still the one of format #1, although the file is saved with the file name extension of format #2. This hick-up is not directly obvious to the user. But if the file is re-saved (e.g. after modifications), Cocoa is trying to extend the sandbox for the URL of type #1, and fails with the following error message at the Xcode console: -[STBDocument saveToURL:ofType:forSaveOperation:completionHandler:] [Line 521] typeName: com.janome.jef -[STBDocument saveToURL:ofType:forSaveOperation:completionHandler:] [Line 523] targetTypeUTI: com.tajima.dst NSFileSandboxingRequestRelatedItemExtension: Failed to issue extension for /Users/matthias/Desktop/Ohne Titel.jef because: Error Domain=NSPOSIXErrorDomain Code=3 "No such process" -[NSFileCoordinator itemAtURL:willMoveToURL:] could not get a sandbox extension. oldURL: file:///Users/matthias/Desktop/Ohne%20Titel.dst, newURL: file:///Users/matthias/Desktop/Ohne%20Titel.jef I'm currently fixing this issue by determining the UTType for the new file name extension and passing it to super. Unfortunately I have no idea how long this issue was already present, and cannot replicate it with a sample app based on Apple's Xcode 26 template (too many differences to my >15 years old app) - so I won't file a bug report. Take this post just for information in case someone else is facing a similar situation...