I am experiencing the same issue as are many others, therefore it's unlikely to be a local network or system issue. It looks more like an Apple network or CDN config issue. Download failed as the server said it was a bad request. (Asset download for com.apple.MobileAsset.iOSSimulatorRuntime e4478b4b9014ff28fe3c265daca488f55a284f4c) Downloading iOS 26.2 Simulator (23C54) (arm64): Error: Error Domain=DVTDownloadsUtilitiesErrorDomain Code=-1 "Download failed as the server said it was a bad request. (Asset download for com.apple.MobileAsset.iOSSimulatorRuntime e4478b4b9014ff28fe3c265daca488f55a284f4c)" UserInfo={NSUnderlyingError=0x6000014aa580 {Error Domain=com.apple.MobileAssetError.Download Code=40 "Download failed as the server said it was a bad request. (Asset download for com.apple.MobileAsset.iOSSimulatorRuntime e4478b4b9014ff28fe3c265daca488f55a284f4c)" UserInfo={NSLocalizedDescription=Download failed as the server said it was a bad request. (Asset download for com.apple.MobileAsset.iOSSimulatorRuntime e4478b4b9014ff28fe3c265daca488f55a284f4c), checkConfiguration=true}}, NSLocalizedDescription=Download failed as the server said it was a bad request. (Asset download for com.apple.MobileAsset.iOSSimulatorRuntime e4478b4b9014ff28fe3c265daca488f55a284f4c), DetailedAssetAttributes=Failed downloading asset with attributes ({ Architectures = ( arm64 ); ArchiveDecryptionKey = "2DYVQ3nImChvmjNXYnGUy0b+gQKHwr2YXnMo/CjcSE0="; ArchiveID = "S4/QPQeJfaTevGsiFxetZjcvpMAuUoJrkiLXXeNARCs="; AssetFormat = AppleArchive; AssetType = "com.apple.MobileAsset.iOSSimulatorRuntime"; Build = 23C54; Ramp = 0; SimulatorVersion = "26.2"; TrainName = LuckC; "_CompressionAlgorithm" = AppleArchive; "_DownloadSize" = 8388608000; "_Measurement" = {length = 20, bytes = 0x9c93e171a2b8792b9988dd9b44621dc2efb8a3dc}; "_Measurement-SHA256" = {length = 32, bytes = 0x282fa56b c46cd445 b8709fa9 3c720915 ... c56f4284 351baf1a }; "_MeasurementAlgorithm" = "SHA-1"; "_UnarchivedSize" = 8381083648; "__AssetDefaultGarbageCollectionBehavior" = NeverCollected; "__BaseURL" = "https://updates.cdn-apple.com/2025/mobileassets/094-34645/AAEDD290-8894-4C50-AFA8-34D3F40B76B3/"; "__CanUseLocalCacheServer" = 1; "__RelativePath" = "com_apple_MobileAsset_iOSSimulatorRuntime/6AF3CC0B-EFC5-41D9-9F53-21E03072E041.aar"; })} System Information macOS Version 15.7.1 (Build 24G231) Xcode 26.2 (24553) (Build 17C52)

After clearing every cache I could think of I finally just reset the UI with defaults delete com.apple.dt.Xcode 2>/dev/null || true On restarting Xcode I had to re add my account but I could then download the iOS Simulator 26.2 runtime.

After clearing every cache I could think of I finally just reset the UI with defaults delete com.apple.dt.Xcode 2>/dev/null || true On restarting Xcode I had to re-add my account but I could then download the iOS Simulator 26.2 runtime.