Getting macOS app icons from Icon Composer working in Xcode 26.x appears to have caused widespread confusion. I've certainly had more than one headache from it. Here's what works for me: Drag the .icon file from Icon Composer into the Xcode Project Navigator, dropping it at the same level as Assets.xcassets — not inside it. In the Project Navigator, click the top-level project item to open the Project Editor. Select your app target and open the App Icons and Launch Screen section. Enter the icon name (without the .icon extension) in the App Icon field. In that same section, leave App Icons Source unchecked. Go to the Build Phases tab and expand Copy Bundle Resources. Delete the Assets.xcassets entry, leaving only the .icon file. Clean the build folder (⇧⌘K) and run. Your icon should now appear in the Dock. It appears that Icon Composer icons and even the presence of the Asset Catalog icons in Copy Bundle Resources are mutually exclusive right now. Including the Asset Catalog appears to suppress the Icon Composer icon. Removing it lets the Icon Composer icon through. Note: If your app depends on other assets in the Asset Catalog, this approach won't work for you. In that case, fall back to the traditional method — export all required sizes from Icon Composer and import them into the Asset Catalog. Hopefully Apple addresses this conflict soon.