[BUG] Cowork "Virtualization is not available" on Windows 11 Pro 25H2 (Build 26200.8039) — all virtualization features enabled, CoworkVMService running, VM never initializes

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?

Preflight Checklist

• [x] I have searched existing issues and this hasn't been reported with this exact build
• [x] This is a single bug report
• [x] I am using the latest version of Claude Desktop

What's Wrong?

Cowork tab shows:
"Virtualization is not available — Claude's workspace requires Virtual Machine Platform,
but the virtualization service isn't responding. Restart your computer to resolve this."

Restarting does not resolve it. Full clean reinstall (including AppData cleanup) does not resolve it.

Environment

| Item | Details |
|---|---|
| Claude Desktop | Latest version from claude.ai/download |
| OS | Windows 11 Pro |
| Version | 25H2 |
| OS Build | 26200.8039 |
| Subscription | Pro |

PowerShell Verification (run as Administrator)

| Check | Result |
|---|---|
| Microsoft-Hyper-V-All | ✅ Enabled |
| VirtualMachinePlatform | ✅ Enabled |
| HypervisorPlatform | ✅ Enabled |
| CoworkVMService | ✅ Running |
| %APPDATA%\Claude\logs\cowork_vm_node.log | ❌ Does not exist — VM never initializes |

Steps to Reproduce

1. Install Claude Desktop (latest version from claude.ai/download) as Administrator on Windows 11 Pro 25H2 (Build 26200.8039)
2. Verify all virtualization features are enabled via PowerShell (Get-WindowsOptionalFeature)
3. Verify CoworkVMService is Running (Get-Service CoworkVMService)
4. Run bcdedit /set hypervisorlaunchtype auto as Administrator and restart
5. Open Claude Desktop → navigate to Cowork tab
6. Observe "Virtualization is not available" error immediately
7. Check %APPDATA%\Claude\logs\ — folder does not exist, VM never attempted to initialize

Additional Steps Attempted (none resolved the issue)

• Restarted computer multiple times
• Full clean uninstall: removed Claude via Windows Settings > Apps
• Deleted %APPDATA%\Claude, %LOCALAPPDATA%\Claude, %LOCALAPPDATA%\AnthropicClaude manually
• Reinstalled Claude Desktop as Administrator from claude.ai/download
• Ran bcdedit /set hypervisorlaunchtype auto as Administrator before restart

Expected Behavior

Cowork should detect that all virtualization features are enabled and successfully
initialize the VM workspace.

Actual Behavior

Cowork permanently shows the "Virtualization is not available" error.
The VM never attempts to initialize. No logs are generated under %APPDATA%\Claude\.
This appears to be the same yukonSilver not supported (status=unsupported) detection
bug reported in #27316, #27420, #29887, #32004, #32574.

Notes

• Chat and Code tabs work perfectly in the same Claude Desktop installation
• Only Cowork is affected
• This is NOT a BIOS/system configuration issue — all system-level checks confirm

virtualization is active and functional

• The error message directing users to restart is misleading and does not address

the actual root cause

What Should Happen?

<img width="919" height="512" alt="Image" src="https://github.com/user-attachments/assets/fb08ada1-a194-458c-a065-e43c3b0075a0" />

Error Messages/Logs

Steps to Reproduce

<img width="919" height="512" alt="Image" src="https://github.com/user-attachments/assets/fcb96d46-ba67-41fb-b37b-c9f79b66c78a" />

Claude Model

Sonnet (default)

Is this a regression?

Yes, this worked in a previous version

Last Working Version

_No response_

Claude Code Version

1.1.9310 cb30ac

Platform

Anthropic API

Operating System

Windows

Terminal/Shell

PowerShell

Additional Information

<img width="1068" height="807" alt="Image" src="https://github.com/user-attachments/assets/c6dfe680-2285-4e5f-a4ea-4742a46d8e32" />