I encountered this same problem, but like @nevyn reported, the Xcode Cloud error referenced my RealityKit assets bundle as a whole, and not a skybox specifically. I discovered that the cause of the error was an ImageBasedLightComponent I had defined in my Reality Composer Pro project. My ImageBasedLightComponent was referencing a PNG file, not an HDR file. I still saw the error even after removing the PNG file reference entirely. I removed the ImageBasedLightComponent and created my ImageBasedLightComponent in code instead. After making that change, I was able to successfully deploy my app using Xcode Cloud, and I no longer saw the "realitytool requires Metal for this operation and it is not available in this build environment" error message.

I was able to reproduce this bug using Xcode 26.0 beta 3 (17A5276g).

I was able to reproduce this bug in 26.0 beta 2 (17A5241o).

FB18241928 includes a minimal sample app demonstrating the issue and detailed repro steps.

Workaround version that includes import SwiftUI:

As the engineer above wrote, the answer to this question is in the Xcode 26 release notes: Xcode may crash on launch restoring UI state. (152042209) Workaround: Remove your UserInterfaceState.xcuserstate file from the project/workspace. In macOS Terminal, you can find this file in your Xcode project directory tree with: find . -name '*.xcuserstate' -print and then delete it with rm. I have been assured that this is a cache file and contains no important project state and is safe to remove.

This issue appears to be fixed in Reality Composer Pro 2.0 (476.0.0.508.4), included with Xcode 26.0 beta (17A5241e).

(response continued from reply to the apple engineer in the accepted answer to work around the dev forum's 500 character comment limit) fwiw, the page https://developer.apple.com/documentation/realitykit/loading-entities-from-a-file describes .reality files in the context of the Reality Composer app (the old one), not Reality Composer Pro. Until you mentioned it just now, it wasn't clear to me that a RealityKitContent bundle contains a .realty file, as this implementation detail is not exposed in any user-facing way in Reality Composer Pro or Xcode. The page https://developer.apple.com/documentation/visionOS/designing-realitykit-content-with-reality-composer-pro does mention .reality files in two callouts that specifically refer to the their importance for performance reasons, but without deep investigation, this is confusing to a new user. I didn't notice that my project was using .reality files at all until just now when, motivated by your developer forums answer, I happened to look in /Users/drew/Library/Developer/CoreSimulator/Devices/A50E7AE3-EDE3-44BA-878B-E0DBE4A6F834/data/Containers/Bundle/Application/4C2EF75B-AE35-42B0-8A5B-ABE2B74CCE82/Baseball.app/RealityKitContent_RealityKitContent.bundle It would be nice if https://developer.apple.com/documentation/realitykit/loading-entities-from-a-file and the documentation for ModelEntity https://developer.apple.com/documentation/realitykit/modelentity and Entity(named:in:) https://developer.apple.com/documentation/realitykit/entity/init(named:in:) could be updated to make this clearer.

If you've implemented a workaround for this issue, you may want to investigate it again. I think it may have been fixed in iOS 18.5 or perhaps earlier.

Hi, any updates on this issue? In new development, I just encountered “error 1” again trying to read a corrupt material that had been created for a different reason, and I wasted hours rediscovering the cause and tracking down the source of the problem. If RealityKit could respond with an error that provided any context at all, like the name of the shader graph node or the unrecognized attribute, the fix would have taken minutes instead of hours. I know you’re quite busy but I’d appreciate any response at all regarding the status of this issue. Thank you.

I also installed 15.4.1 and Xcode 16.3 appears to work for me. I was able to run an app in the iOS 18.4 and iOS 17.5 simulators. Sorry that's not helpful. Does the simulator actually not load at all, or does your app not launch in the simulator, or does your app launch, but crash? Are you low on disk space? I'm sure you've tried all these, but off the top of my head: Try rebooting Try other simulator iOS versions In Xcode > Settings > Components try deleting the iOS simulator you're using (with right-click > Remove) and then reinstalling that simulator Delete everything in the Derived Data folder and rebuild Are you low on disk space? What have you tried already?

Hi, any updates on this issue? I'm concerned that when Xcode 17 is released, the new iOS 19 simulator won't support RealityKit reliably either, and supporting iOS 17 just so the simulator is useful for development will become problematic. Thank you.

Possibly related: Sometimes, in the iOS 18 simulator only, the ARView appears black and none of my app's geometry is rendered.

Possibly related: While collecting the fully symbolicated crash logs I posted in an earlier comment, three times, in the iOS 18 simulator only, my app hung while loading geometry for a RealityKit scene. I paused the app in the debugger and saw the following stack trace. I couldn't use Xcode > Debug > Detach and get a crash log in this case because the app would hang and did not crash. #0 0x00000001006ec55c in __semwait_signal () #1 0x00000001801695dc in nanosleep () #2 0x00000001801694b0 in usleep () #3 0x00000001aa9cf94c in re::AssetLoadRequest::Data::waitForCompletion () #4 0x00000001aa938068 in re::NetworkSendBlockingAssetLoadRequestManager::flushAndWaitForECSSendBlockingAssetLoadRequests () #5 0x00000001aaee2a98 in re::ecs2::NetworkSendSystem::update () #6 0x00000001aafd013c in re::internal::Callable<re::ecs2::ECSManager::configurePhaseECSSystems(re::Scheduler::ScheduleDescriptor&, re::ecs2::ECSSystemGroup, unsigned long)::$_0, void (float)>::operator() () #7 0x00000001ab463774 in re::Scheduler::executePhase () #8 0x00000001aa8cec10 in re::Engine::executePhase () #9 0x00000001aa8d71cc in re::Engine::timeDidChange () #10 0x00000001ab464da0 in re::Event<re::SimulationTimer, re::SimulationTimerEventArgs const&>::raise () #11 0x00000001ab464cd8 in re::VariableStepTimer::onClockDidChange () #12 0x00000001ab4643f8 in re::Event<re::SimulationClock, re::SimulationClockEventArgs const&>::raise () #13 0x00000001ab4645d4 in re::DisplayLinkClock::update () #14 0x000000018afcfccc in CA::Display::DisplayLinkItem::dispatch_ () #15 0x000000018afcbdac in CA::Display::DisplayLink::dispatch_items () #16 0x000000018afd29f8 in CA::Display::DisplayLink::dispatch_deferred_display_links () #17 0x000000018504aa80 in _UIUpdateSequenceRun () #18 0x00000001859f2750 in schedulerStepScheduledMainSection () #19 0x00000001859f1b88 in runloopSourceCallback () #20 0x000000018041b484 in __CFRUNLOOP_IS_CALLING_OUT_TO_A_SOURCE0_PERFORM_FUNCTION__ () #21 0x000000018041b3cc in __CFRunLoopDoSource0 () #22 0x000000018041ab30 in __CFRunLoopDoSources0 () #23 0x0000000180415210 in __CFRunLoopRun () #24 0x0000000180414ac0 in CFRunLoopRunSpecific () #25 0x00000001906e0b10 in GSEventRunModal () #26 0x0000000185ac325c in -[UIApplication _run] () #27 0x0000000185ac7454 in UIApplicationMain () #28 0x0000000184eb40d8 in UIKit.UIApplicationMain(Swift.Int32, Swift.Optional<Swift.UnsafeMutablePointer<Swift.UnsafeMutablePointer<Swift.Int8>>>, Swift.Optional<Swift.String>, Swift.Optional<Swift.String>) -> Swift.Int32 () #29 0x0000000102c421b0 in static UIApplicationDelegate.main() () #30 0x0000000102c42128 in static AppDelegate.$main() () #31 0x0000000102c4222c in main at /Users/drew/Repos/Baseball/Baseball/Sources/AppDelegate.swift:14 #32 0x0000000100391410 in start_sim () #33 0x000000010026e274 in start () This hanging was preceded by many messages like the following in the Xcode console: Asset 8262083708093167093 Material (Framework)com.apple.CoreRE/pbr.rematerial failure: Asset provider load failed: type 'Framework' -- unknown framework: com.apple.CoreRE load failed: couldn't load '8262083708093167093 Material (Framework)com.apple.CoreRE/pbr.rematerial' (Asset provider load failed: type 'Framework' -- unknown framework: com.apple.CoreRE) AssetLoadRequest failed because asset failed to load '8262083708093167093 Material (Framework)com.apple.CoreRE/pbr.rematerial' (Asset provider load failed: type 'Framework' -- unknown framework: com.apple.CoreRE) load failed: asset loading already has failed '8262083708093167093 Material (Framework)com.apple.CoreRE/pbr.rematerial' (Asset provider load failed: type 'Framework' -- unknown framework: com.apple.CoreRE) Invalid asset: '8262083708093167093 Material (Framework)com.apple.CoreRE/pbr.rematerial' load failed: asset loading already has failed '8262083708093167093 Material (Framework)com.apple.CoreRE/pbr.rematerial' (Asset provider load failed: type 'Framework' -- unknown framework: com.apple.CoreRE) Invalid asset: '8262083708093167093 Material (Framework)com.apple.CoreRE/pbr.rematerial' load failed: asset loading already has failed '8262083708093167093 Material (Framework)com.apple.CoreRE/pbr.rematerial' (Asset provider load failed: type 'Framework' -- unknown framework: com.apple.CoreRE) Invalid asset: '8262083708093167093 Material (Framework)com.apple.CoreRE/pbr.rematerial'

Possibly related: Sometimes, in the iOS 18 simulator only, CustomMaterial(surfaceShader:geometryModifier:lightingModel:) fails and throws the error "The building parameters were invalid". This error is preceded by the following messages in the Xcode console: Error Domain=REMaterialBuilderErrorDomain Code=50 "Program "realitykit::fsSurfacePbr" failed due to invalid argument numbers. Constant buffer count [19] exceeds limit [14]. " UserInfo={NSLocalizedDescription=Program "realitykit::fsSurfacePbr" failed due to invalid argument numbers. Constant buffer count [19] exceeds limit [14]. } Pipeline data for technique SurfaceShaderOpaque failed compilation! Asset 14147473638299271299 MaterialDefinition (Framework)com.apple.CoreRE/surfaceShader.rematerialdefinition failure: Asset provider load failed: type 'Framework' -- unknown framework: com.apple.CoreRE Asset 8115819767006447788 Material (MemoryAsset)asset29.compiledmaterial failure: failed to register asset load failed: couldn't load '8115819767006447788 Material (MemoryAsset)asset29.compiledmaterial' (failed to register asset)