Environment: Xcode Version: Xcode 26.3 Affected iOS Versions: iOS 26.1 and later Working iOS Versions: iOS 26.0 and earlier Tested Devices: iPhone 15 Pro (iOS 26.2) - ❌ Bug presents iPhone 17 (iOS 26.1) - ❌ Bug presents iPhone Air (iOS 26.0) - ✅ Works as expected iPhone 16 Pro Max (iOS 18.0) - ✅ Works as expected Description: We have identified a severe localization regression regarding the setAlternateIconName(_:completionHandler:) API starting from iOS 26.1. Our application is strictly restricted to support only Traditional Chinese (zh-TW / zh-Hant). We have correctly configured CFBundleLocalizations, CFBundleDevelopmentRegion, and explicitly set CFBundleAllowMixedLocalizations to YES in our Info.plist. In iOS 26.0 and earlier, when changing the app icon, the system alert correctly displays in Traditional Chinese. However, in iOS 26.1 and later, the alert unexpectedly falls back to English, completely ignoring the app's localization constraints and the user's preferred device language. Crucial Observation:
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