After iOS 27 ships: Xcode 27, the SDK, and store gates

Users can update the OS. That does not mean your build Mac, SDK, and store binary already line up. Below we split “what you can submit today,” “what you must submit next April,” and “which layer to replace first on the desk and in CI,” then tie it to our iOS 27 device tiers and the WWDC26 Xcode 27 / Foundation Models notes.

The GM opens user devices. The developer window is “you may upload a 27 SDK build now; you must next April.” Do not collapse those into one panic night.

Two calendars: user ship day ≠ developer deadline

At the 9 September event Apple said iOS 27 opens on 14 September for compatible iPhones. The same week, developer news said you can build with the Xcode 27 Release Candidate and submit to the App Store and TestFlight. User upgrade and store intake sit in the same week; the mandatory SDK cut does not.

Device list and Apple Intelligence tiers: five-phone table. Event cadence: fall event notes. This piece is only the toolchain and store rules.

Where Xcode 27 installs, what it ships

Xcode 27 ships Swift 6.4 and the iOS 27, iPadOS 27, macOS 27, tvOS 27, watchOS 27, and visionOS 27 SDKs. On-device debugging starts at iOS 17 / tvOS 17 / watchOS 10 / visionOS 1. Deployment can still go down to iOS 15 — the mandate is which SDK you build with, not the user’s minimum OS.

After install, check SDKs — do not trust the big version number alone:

# sw_vers / xcodebuild / MCP
sw_vers
xcodebuild -version
xcodebuild -showsdks
xcrun mcp-server status

Coding Intelligence in Xcode 27 can exercise watchOS (Digital Crown / Action Button) and previews an MCP server that does not need an open workspace. Unattended boxes can run sudo xcrun mcp-server enable --unsafe-always-allow-all-agents — not a desk default. Remote xcodebuild still follows remote Xcode automation.

Hard SDK gates: scenes and the launch screen

Two changes make old projects fail to launch or fail upload once you compile with the iOS 27 SDK. Builds from older SDKs are exempt for now — that is the line between “you can wait” and “fix it the day you switch.”

1. Scene-based life cycle: missing means it will not launch

On iOS 27 / iPadOS 27 / Mac Catalyst 27 / tvOS 27 / visionOS 27, apps built with the latest SDK must adopt the scene-based life cycle or they fail to launch. Apple’s wording is hard: not a warning, a no-start.

Signals you must migrate

UIApplicationSceneManifest missing or empty in Info.plist.

App delegate does not implement application(_:configurationForConnecting:options:).

Two legal shapes

Turn on Scene manifest in Deployment Info, or return a configuration from the app delegate per session.

2. Launch screen: TN3208 / ITMS-90870

From iOS 27 / iPadOS 27, App Store Connect requires one of UILaunchStoryboardName, UILaunchStoryboards, UILaunchScreen, UILaunchScreens. Missing any of them is ITMS-90870. Same rule on the App Store and EU alternative marketplaces.

<key>UILaunchScreen</key>
<dict/>

New SwiftUI apps get UILaunchScreen when Generate Info.plist File and Launch Screen (Generation) are on. Lean Info.plist files and hand-rolled CI bundles miss it. Verify by deleting the app and installing cold so the splash actually appears.

App Store: optional now, required in April 2027

After 9 September you may upload Xcode 27 RC builds. The hard floor is April 2027: iOS / iPadOS need the iOS 27 & iPadOS 27 SDK or later; tvOS, visionOS, and watchOS each need their 27 SDK. macOS 27 SDK is not in that same “must” sentence — Mac apps feel the Apple-silicon-only OS, not that April clause.

The product page is moving too. Re-answer age ratings: Time Allowances let parents cap Entertainment, Games, and Social Media. Declare social capabilities in App Store Connect. New header and search-result assets are coming, with a preview tool. Those will not fail xcodebuild, but they will stall “Ready to Submit.”

Foundation Models and review extras

WWDC26 folded Foundation Models into one Swift API: on-device models, Private Cloud Compute server models, and third-party packages via LanguageModel. Core AI promotes your own models; Evaluations tests intelligence features. Image input, custom skills, and Dynamic Profiles are this cycle’s extras. Background: WWDC26 Apple AI vs Copilot.

Small teams: App Store Small Business Program members under 2 million first-time downloads can use the next Apple Foundation Models on Private Cloud Compute without a separate cloud API bill. That is not “free for everyone.”

The Foundation Models Instrument in Xcode 27 shows instructions, prompts, responses, tokens, and inference time. For review you still need to say whether data left the device, whether it used PCC, and who the third-party vendor is.

CI / cloud Mac: Intel builders stop here

The release-week failure mode is rarely Swift syntax. It is a builder still on Intel or macOS 26.3. Xcode 27 wants 26.4+ and Apple silicon. Address Sanitizer on iOS 27 can fail under Xcode 26.4 and older — use 26.5 or Xcode 27. Hosted macos-latest will queue and version-skew if the image lags.

• Desk — Apple silicon + macOS 26.4+, then Xcode 27. Intel laptops only keep shipping 26 SDK hotfixes
• CI — self-hosted runners must be M-series; pin xcode-select, certs, simulator runtimes, and the 27 SDK on one box
• Remote — Windows / Linux still SSH / VNC into that Mac
• Keys — keep production signing off the daily laptop

If you need a Mac that is not also someone’s daily driver and can track 26.4 for Xcode 27, a dedicated node by the day is calmer than forcing every office laptop through the upgrade — especially while someone still has to ship a 26 SDK hotfix.

Two-week checklist

1. Builder is Apple silicon and sw_vers ≥ 26.4.
2. Xcode 27 RC / GM installed; xcodebuild -showsdks lists iOS 27.
3. Scene manifest on; delete the old install and cold-launch on device.
4. One of the four launch-screen keys present; internal TestFlight on the 27 SDK to catch ITMS-90870.
5. Re-answer age ratings; tick social capabilities if you have them.
6. Refresh product-page header / search assets even if the live binary is still Xcode 26.
7. If a Mac app still ships an Intel slice, treat it as the last generation; new work is arm64-only.
8. Schedule the first 27 SDK production build in 2026 Q4 or 2027 Q1 — not the last week of March 2027.

FAQ

Must I use the iOS 27 SDK to ship today?
No. From 9 September you may. The mandate is April 2027. Xcode 26 binaries still upload until then; you just miss new APIs and the new review questions.

Can an Intel Mac install Xcode 27?
No. Apple silicon only. macOS 26 is the last Intel/Rosetta system; macOS 27 is Apple silicon only. Retire Intel builders before the April cut.

Why does a 27 SDK build fail to launch?
Usually the old AppDelegate life cycle. Latest-SDK binaries must be scene-based or they will not start on iOS 27. Older-SDK binaries are exempt for now.

What is ITMS-90870?
Missing launch screen. iOS 27 SDK (or later) uploads need one of the four Info.plist keys or App Store Connect rejects the binary.

Must the deployment target become iOS 27?
No. Xcode 27 still allows iOS 15. The rule is which SDK you compile with, not the user’s minimum OS.