SUMMARY In Xcode 27.1, opening any Main.storyboard never finishes loading. The editor shows "Loading iOS 27.1..." indefinitely. This happens in existing projects and in a brand-new iOS App project created with Interface: Storyboard. Before that, the editor showed "Failed to open Main.storyboard: iOS 27.1 Platform Not Installed." ENVIRONMENT Xcode 27.1 iOS SDK build: 24A94232 (from xcrun --sdk iphonesimulator --show-sdk-build-version) macOS: [YOUR macOS VERSION] Hardware: MacBook Air, Apple M1 Run destination: iPhone 17 Pro Max simulator STEPS TO REPRODUCE Open Xcode 27.1. Create a new project: iOS > App, Interface: Storyboard, Language: Swift. Click Main.storyboard in the Project Navigator. EXPECTED RESULT The storyboard renders in Interface Builder and the Objects library lists UI elements. ACTUAL RESULT The editor stays on "Loading iOS 27.1..." and the Objects library shows "No Matches." Opening the file as Source Code works, and the XML is valid (targetRuntime="iOS.CocoaTouch"), so the file itself is fine. RUNTIME STATE Initially the only iOS 27.1 runtime installed was build 24A94425, shown as Ready in xcrun simctl runtime list. Xcode reported "iOS 27.1 Platform Not Installed," and the runtime did not appear in Settings > Components. The Xcode SDK build is 24A94232, which does not match 24A94425. I ran xcodebuild -downloadPlatform iOS, which installed iOS 27.1 (24A94232). The error then changed to "Loading iOS 27.1..." and stayed there. Settings > Components then showed an "Update" button for iOS 27.1 (8.07 GB). Clicking it installed iOS 27.1 (24A94425) again, so both builds are now present and Ready. The storyboard is still stuck. WHAT I TRIED (none fixed it) Deleting ~/Library/Developer/Xcode/DerivedData sudo killall -9 com.apple.CoreSimulator.CoreSimulatorService Removing and reinstalling the iOS 27.1 runtime Restarting the Mac Waiting several minutes on the first load (~/Library/Developer/Xcode/UserData/IB Support does not exist on this machine) [link text](https://www.example.com/)

SUMMARY In Xcode 27.1, opening any Main.storyboard never finishes loading. The editor shows "Loading iOS 27.1..." indefinitely. This happens in existing projects and in a brand-new iOS App project created with Interface: Storyboard. Before that, the editor showed "Failed to open Main.storyboard: iOS 27.1 Platform Not Installed." ENVIRONMENT Xcode 27.1 iOS SDK build: 24A94232 (from xcrun --sdk iphonesimulator --show-sdk-build-version) macOS: [YOUR macOS VERSION] Hardware: MacBook Air, Apple M1 Run destination: iPhone 17 Pro Max simulator STEPS TO REPRODUCE Open Xcode 27.1. Create a new project: iOS > App, Interface: Storyboard, Language: Swift. Click Main.storyboard in the Project Navigator. EXPECTED RESULT The storyboard renders in Interface Builder and the Objects library lists UI elements. ACTUAL RESULT The editor stays on "Loading iOS 27.1..." and the Objects library shows "No Matches." Opening the file as Source Code works, and the XML is valid (targetRuntime="iOS.CocoaTouch"), so the file itself is fine. RUNTIME STATE Initially the only iOS 27.1 runtime installed was build 24A94425, shown as Ready in xcrun simctl runtime list. Xcode reported "iOS 27.1 Platform Not Installed," and the runtime did not appear in Settings > Components. The Xcode SDK build is 24A94232, which does not match 24A94425. I ran xcodebuild -downloadPlatform iOS, which installed iOS 27.1 (24A94232). The error then changed to "Loading iOS 27.1..." and stayed there. Settings > Components then showed an "Update" button for iOS 27.1 (8.07 GB). Clicking it installed iOS 27.1 (24A94425) again, so both builds are now present and Ready. The storyboard is still stuck. WHAT I TRIED (none fixed it) Deleting ~/Library/Developer/Xcode/DerivedData sudo killall -9 com.apple.CoreSimulator.CoreSimulatorService Removing and reinstalling the iOS 27.1 runtime Restarting the Mac Waiting several minutes on the first load (~/Library/Developer/Xcode/UserData/IB Support does not exist on this machine)