John SiracusaSep 10, 2025

Hey, I got a response to one of my Feedbacks!

Me: “In Xcode 26 beta 4, if a Mac app included a new Tahoe-style .icon file with the same name as its existing app icon in its .appiconset file, the Tahoe-style .icon would show up in Tahoe and the pre-Tahoe icon from the .appiconset would show up in pre-Tahoe versions of macOS.

In Xcode beta 5, this no longer works. The Tahoe .icon is shown on all versions of macOS.”

(1 month passes)

Apple: "Please know that this is by design.”

Felix SchwarzSep 11, 2025
Show threadJohn Siracusa

Anyway, a month ago I also filed FB19437407: Provide a way for an app to have different app icons in Tahoe and pre-Tahoe versions of macOS

There is a way to do this today using an undocumented command-line option:

1. Name your Tahoe .icon file the same as the name of your existing .appiconset in the Assets catalog.

2. Set the ASSETCATALOG_OTHER_FLAGS build setting to --enable-icon-stack-fallback-generation=disabled

But how long will this work?

Sep 10, 2025 at 1:02pmIvory for Mac
Show threadRyan McLeodSep 10, 2025

@siracusa been fighting this all week. Incredibly lazy and weird of them to not look back.

I heard that if you ship with this flag the AppStore will use your old icon so I'm stripping it out and just doing what they want :(

Show threadDevinSep 10, 2025
@warpling my Icon Composer variant causes Xcode archive errors when I use it for all OS versions, so forced to use the legacy flag 😕
Show threadNico RohrbachSep 11, 2025
@warpling I guess @siracusa is using the undocumented command-line option for his app SwitchGlass and it seems to work even for the Mac App Store. Look at my screenshots from macOS 15.6.1 and macOS 26 RC.
Show threadJohn SiracusaSep 11, 2025
@superpixel @warpling Yep.
Show threadFreediverXSep 10, 2025
@siracusa It’ll work until Apple sees your post and disables your workaround.
Show threadDer TeilweiseSep 11, 2025

@siracusa I filed my feedback on Jul 26:

“Recent Similar Reports: None”

Feedback is valued at Apple.
Apple engineers do read it.

No words.

FB19112370 : “iOS 26 changes […] The new icons do not match the older systems. Dropping support for iOS 18 (or older) often is not an option.

Thus there should be an option to provide two sets of App icons: One for iOS 18 and older and a new set for iOS 26 and newer.

[…]”

Show threadDimitri BouniolSep 12, 2025

@siracusa Are you by any chance getting these warnings during builds with this option on?

"Failed to generate flattened icon stack for icon named ‘…’.”

Show threadJohn SiracusaSep 12, 2025
@dimitribouniol Yep, but I am ignoring them because the built apps seem to work the way I want them to.
Show threadDimitri BouniolSep 12, 2025
@siracusa Cool, not just me then (and I also verified they seem to be working, thanks for sharing!)
Show threadNico RohrbachNov 4
@siracusa Could it be, that this trick does not work with Xcode 26.1 anymore? (I just built one of my projects with it and now it uses the Tahoe Icon even on Sequoia.)
Show threadJohn SiracusaNov 4
@superpixel Yes, it looks like it doesn't work anymore :-/