The whole lineup went out at once on Monday — iOS 27, iPadOS 27, macOS 27 'Golden Gate', plus tvOS, visionOS, and watchOS 27. If you build for any of them, the groundwork landed last week: App Store Connect opened for the Xcode 27 RC and the 27.0 SDKs on the 10th, so you can ship against the shipping OS today rather than wait. Apple has pencilled April 2027 as the point where new submissions must build against the iOS 27 (and iPadOS/tvOS/visionOS/watchOS 27) SDK — far enough out to ignore for now, close enough to note. The line worth circling is on the Mac. macOS 27 is Apple-silicon-only, which makes last year's macOS 26 the final release to run on Intel hardware and Rosetta. If you still ship an x86 slice or lean on Rosetta in CI, that clock has started. The consumer headline — the Apple Intelligence Siri rebuild, this time leaning on Google's Gemini models — isn't actually here yet; the company is holding the full Siri AI experience for a later beta, so day one is the OS, not the assistant.