I added a new liquid glass icon built with Icon Composer to my app. It works and looks great on iOS 26 but Xcode complains that required icon files for older versions are missing.
I still have the old AppIcon in my Asset Catalog but it seems like it's not being used.
How do I configure Xcode to use the old icons for iOS 18 and the new icon for iOS 26?
In my existing app, after opening the project in Xcode 26 and adding the new glass icon file (AppIconGlass.icon in my case) to the project, I needed to do the following:
That's it. Just make sure you do not have any manual entries in your Info.plist related to the app icons. Xcode will add them automatically as part of the build. And it will do so in a way that shows the new glass icon for iOS 26 and the previous app icons for iOS 18 and earlier.
I tried configuring according to your steps, but I'm still encountering the missing file error.
I attempted to rename the old icon in Assets to match the new icon's name, which resolved the compilation issue. However, strangely, the behavior differs between my two apps.
In the first app:
iOS 18 correctly displays the old icon.
iOS 26 shows the glass effect normally for both light and dark mode icons, but the transparent icon appears as a tinted icon.
In the second app:
My old app icons and the new glass icon file do not have the same name and I do not get any errors.
Anyway has any luck with this for macOS apps? I have been trying various tricks and cannot get it to play nice at all. If I specify the "App Icon" part to use the new glass icon, then the app always uses the new icon, even though it seems to be rendered incorrectly in macOS 15. I cannot seem to find a satisfactory way to handle this on macOS at all.
As it turns out, using Xcode 26 to build my app with iOS 18 and iOS 26 app icons is resulting in the iOS 26 glass icon being used for all iOS versions. The Info.plist that is built into the app by Xcode 26 is making the glass icon the primary icon. All of my existing iOS 18 app icons are being set as available alternate icons.
My original iOS 18 (and earlier) app icon is named AppIcon. The new glass .icon file is named AppIconGlass. In Xcode 26 I updated the App Icon field on the General tab from AppIcon to AppIconGlass.
I just discovered that renaming the .icon file to AppIcon.icon and putting back the App Icon field to AppIcon now gives me the correct icon on iOS 18 and iOS 26.
In other words, if you have an app icon asset and your main app icon is named AppIcon in that asset, then when you add the glass icon from Icon Composer to your project, make sure it is named AppIcon.icon. Then on the General tab, enter AppIcon into the App Icon field. I'm also enabling the "Include all app icon assets" option. Taking these steps will give you the proper icon for a given device with a given version of iOS. The icon from the assets will be used for iOS 18 and earlier. The .icon file will be used for iOS 26.
You might need to do a clean build and delete and reinstall the app in the various simulators and devices after making those changes. This will ensure no leftover baggage from the previous setup is still around.
My app also runs on macOS via Mac Catalyst. I have verified that when run from Xcode 26 on my Mac with macOS 15, I get the older icon. At this time I can't confirm if running the same app on a macOS 26 device will give the new glass icon but I'm hopeful.
It turns out that this also works for alternate app icons. If your app icons asset has icons named AppIcon, AppIcon2, AppIcon3, for example, then if you add glass icon files named AppIcon.icon, AppIcon2.icon, and AppIcon3.icon, then existing code to set an alternate app icon works under iOS 18 as well as iOS 26. Under iOS 26 you get the glass variants and under iOS 18 (and earlier), you get the non-glass variants.
This no longer seems to work with Xcode 26 beta 4, at least for macOS. Beta 4 insists on populating the Assets.car with Icon Composer generated variants, disregarding the App Icon provided in Assets. :(
The App Icon variant in Assets makes its way to a .incs file in the app bundle's Contents/Resources folder, but that is not used by macOS anymore and is there for some compatibility purposes. The Assets.car file (which matters) only contains the png variants generated by Icon Composer.
Since the default icon rounding radius is different, I can't use the Icon Composer generated icon for older macOS versions (the icon design needs to follow the curvature of the icon background) as that would look super-ugly. Icon Composer has no option to add variants for older macOS versions, so I need to use custom icons. Xcode 26 beta1-beta3 at least gave the option to do so with this workaround.
Things keep changing during the beta. It's very frustrating since Apple doesn't document anywhere what the correct approach is (or will be by the end of the beta). And there's still no word on how to support alternate app icons with Icon Composer icons.
I've noticed that what I posted here last became obsolete as of beta 3. iOS 18 has been showing a version of the glass icon since then.
It makes much more sense for iOS 18 and lower to keep using the old Assets app icons and for iOS 26+ to use the new glass icons. I don't like the fact that Apple assumes everyone will want the new fancy iOS 26 icon to appear on devices with older versions of iOS. I'm fine with that being an option, but let developers choose how they want their apps to appear and which icons to use.
I posted this as a new separate question, maybe an Apple engineer will respond: