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)
