[BUG] Cowork not working on Hyper-V VM running Windows Server 2022 — solution found

Preflight Checklist

• [x] I have searched existing issues and this hasn't been reported yet
• [x] This is a single bug report (please file separate reports for different bugs)
• [x] I am using the latest version of Claude Code

What's Wrong?

Cowork fails silently on a Windows Server 2022 running as a Hyper-V guest VM. The Cowork tab appears in Claude Desktop but never initializes, with no useful error message shown to the user.

What Should Happen?

Cowork should either work correctly, or display a clear error message explaining that the Hyper-V role must be installed inside the guest VM, rather than silently marking the platform as unsupported.

Error Messages/Logs

[cleanupVMBundleIfUnsupported] yukonSilver not supported (status=unsupported)
[startVM] VM not supported (win32/x64), skipping

Steps to Reproduce

1- Create a Windows Server 2022 Hyper-V guest VM with ExposeVirtualizationExtensions = True
2- Enable VirtualMachinePlatform inside the guest
3- Install Claude Desktop via MSIX with admin privileges
4- Open Claude Desktop — Cowork never initializes

Fix: Also run Install-WindowsFeature -Name Hyper-V -IncludeManagementTools -Restart inside the guest. After reboot Cowork works perfectly.

Claude Model

None

Is this a regression?

No, this never worked

Last Working Version

_No response_

Claude Code Version

2.1.116 (Claude Code)

Platform

Anthropic API

Operating System

Windows

Terminal/Shell

PowerShell

Additional Information

This issue was diagnosed through extensive log analysis and reverse engineering of the app.asar bundle. The root cause was identified by reading the nmr() function in the minified Electron JavaScript, which revealed the exact sequence of platform checks Cowork performs:

Platform must be win32 or darwin ✅
Architecture must be x64 or arm64 ✅
MSIX installer required ✅
Windows build >= 19041 ✅ (Server 2022 is build 20348)
getHcsStatus() check — ❌ this was the blocker

The vmcompute (Host Compute Service) was completely absent because on Windows Server 2022 it is part of the Hyper-V role, which is not installed by default. Simply enabling VirtualMachinePlatform is not sufficient — the full Hyper-V role must be explicitly installed via Install-WindowsFeature.

Once installed, CoworkVMService (which was already running) connected successfully to vmcompute, the yukonSilver status flipped to supported, and Cowork initialized perfectly on the first launch.

This fix was discovered entirely by the user through manual debugging with Claude's help — not documented anywhere. Windows Server 2022 has full Hyper-V capability and should be officially supported. At minimum, the error message should tell users to install the Hyper-V role instead of silently failing.