mlaunch crashes with FormatException when device reports iOS version string containing suffix

[ducoalexandre]

mlaunch fails with System.FormatException when deploying to a physical device running an iOS beta version that includes a suffix in the version string (e.g., 26.3.1 (a)).

The root cause is IRealDevice.GetProductVersion() (IDevice.cs:46) calling System.Version.Parse() on the raw version string. System.Version only accepts numeric components (major.minor[.build[.revision]]), so the (a) suffix causes the parser to fail when trying to parse "1 (a)" as an integer.

Steps to Reproduce
Connect a physical iPhone running an iOS beta build that reports a version with a suffix (in my case, 26.3.1 (a))
Build and deploy a .NET MAUI app targeting net10.0-ios
mlaunch is invoked and crashes before reaching the deployment phase
The device version can be verified with:

xcrun devicectl device info details --device -j /tmp/device_info.json

Which returns "osVersionNumber": "26.3.1 (a)".

Error Output

error MT0000: Unexpected error - Please file a bug report at https://github.com/xamarin/xamarin-macios/issues/new
System.FormatException: The input string '1 (a)' was not in a correct format.
   at System.Number.ThrowFormatException[TChar](ReadOnlySpan`1)
   at System.Number.ThrowOverflowOrFormatException[TChar,TInteger](ParsingStatus, ReadOnlySpan`1)
   at System.Number.ParseBinaryInteger[TChar,TInteger](ReadOnlySpan`1, NumberStyles, IFormatProvider)
   at System.Int32.Parse(ReadOnlySpan`1, NumberStyles, IFormatProvider)
   at System.Version.TryParseComponent(ReadOnlySpan`1, String, Boolean, Int32&)
   at System.Version.ParseVersion(ReadOnlySpan`1, Boolean)
   at System.Version.Parse(String)
   at Xamarin.Hosting.IRealDevice.GetProductVersion() in /Users/builder/azdo/_work/5/s/src/Xamarin.Hosting/Xamarin.Hosting/IDevice.cs:line 46
   at Xamarin.Hosting.IRealDevice.get_SupportsDeviceCtl() in /Users/builder/azdo/_work/5/s/src/Xamarin.Hosting/Xamarin.Hosting/IDevice.cs:line 60
   at Xamarin.Launcher.Driver.LaunchOrDebugAsync(Action, IRealDevice) in /Users/builder/azdo/_work/5/s/src/Xamarin.Hosting/Xamarin.Launcher/Main.cs:line 575
   at Xamarin.Launcher.Driver.LaunchOrDebugAsync(Action) in /Users/builder/azdo/_work/5/s/src/Xamarin.Hosting/Xamarin.Launcher/Main.cs:line 569
   at Xamarin.Launcher.Driver.MainAsync() in /Users/builder/azdo/_work/5/s/src/Xamarin.Hosting/Xamarin.Launcher/Main.cs:line 507
   at Xamarin.Utils.NSRunLoopExtensions.RunUntilTaskCompletion[T](NSRunLoop, Task`1) in /Users/builder/azdo/_work/5/s/src/Xamarin.Hosting/Xamarin.Utils/Extensions.cs:line 29
   at Xamarin.Launcher.Driver.Main2(String[]) in /Users/builder/azdo/_work/5/s/src/Xamarin.Hosting/Xamarin.Launcher/Main.cs:line 456
   at Xamarin.Launcher.Driver.Main(String[]) in /Users/builder/azdo/_work/5/s/src/Xamarin.Hosting/Xamarin.Launcher/Main.cs:line 128

Environment
Device: iPhone 16 Pro Max (iPhone17,2)
iOS version: 26.3.1 (a) (build 23D771330a)
.NET SDK: 10.0.200
iOS SDK pack: Microsoft.iOS.Sdk.net10.0_26.2 (26.2.10217)
Xcode: 26.2.0
macOS: Darwin 25.2.0 (arm64)
Suggested Fix
GetProductVersion() should strip or ignore any non-numeric suffix before calling Version.Parse(). For example, applying a regex like Regex.Replace(versionString, @"\s*(.*)$", "") to sanitize the input would handle beta suffixes gracefully.

Workaround
Deploying via xcrun devicectl bypasses mlaunch entirely and works correctly:

xcrun devicectl device install app --device <device-uuid> path/to/App.app
xcrun devicectl device process launch --device <device-uuid> com.bundle.identifier

[rolfbjarne]

Thanks for the report, a fix is in progress.

[rolfbjarne]

This has been fixed, and it should be possible to apply the updated mlaunch tool by following these instructions (note that you might have to update the path to your local version of mlaunch, depending on which version of the iOS workload you have installed):

• Go here: https://dev.azure.com/dnceng/public/_artifacts/feed/dotnet-eng/NuGet/Microsoft.Tools.Mlaunch/overview/1.1.109%20b4634d4

• Click on the Download button in the upper right corner. This will download Microsoft.Tools.Mlaunch.1.1.109.nupkg.

• Then execute this:

  # remove any quarantine flags by the browser
  $ xattr -s -c -r ~/Downloads/Microsoft.Tools.Mlaunch.1.1.109.nupkg
  
  # extract the nupkg
  $ unzip -d ~/Downloads/Microsoft.Tools.Mlaunch.1.1.109 ~/Downloads/Microsoft.Tools.Mlaunch.1.1.109.nupkg
  
  # Make the new mlaunch executable executable
  $ chmod +x ~/Downloads/Microsoft.Tools.Mlaunch.1.1.109/mlaunch/lib/mlaunch/mlaunch.app/Contents/MacOS/mlaunch
  
  # Make a backup copy of your existing mlaunch:
  $ cp /usr/local/share/dotnet/packs/Microsoft.iOS.Sdk.net10.0_26.2/26.2.10217/tools/lib/mlaunch ~/Downloads/mlaunch-backup
  
  # Overwrite your existing mlaunch with the updated version:
  $ sudo rm -rf /usr/local/share/dotnet/packs/Microsoft.iOS.Sdk.net10.0_26.2/26.2.10217/tools/lib/mlaunch/mlaunch.app
  $ sudo cp -r ~/Downloads/Microsoft.Tools.Mlaunch.1.1.109/mlaunch/lib/mlaunch/mlaunch.app /usr/local/share/dotnet/packs/Microsoft.iOS.Sdk.net10.0_26.2/26.2.10217/tools/lib/mlaunch/
  
  # Verify it works
  $ /usr/local/share/dotnet/packs/Microsoft.iOS.Sdk.net10.0_26.2/26.2.10217/tools/bin/mlaunch --version
  Xamarin.Launcher 1.1.109 (refs/heads/main: b4634d4)

[ThisIsDavidHan]

Thank you @rolfbjarne.

Works like a charm for me for Microsoft.iOS.Sdk.net9.0_26.2/26.2.9000/tools/lib/mlaunch/ too.