Apple began enforcing a new SDK requirement on April 28, 2026: any app uploaded to App Store Connect must be compiled against the iOS 26 and iPadOS 26 SDK. Developers still targeting older SDK versions need to update their Xcode toolchain before submitting new builds or updates. This is a hard deadline enforced at upload time, not at review, meaning submissions built against earlier SDKs will be rejected outright. Teams maintaining apps that haven't migrated their build environments to Xcode with the iOS 26 SDK should treat this as an urgent action item to avoid disrupted release pipelines.