[BUG] Cowork "yukonSilver not supported" on Windows 11 Pro 25H2 — Intel i5-1345U, all virtualization enabled

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?

The Cowork tab never initializes. The log shows:
"yukonSilver not supported (status=unsupported), checking for stale bundle..."

The VM never attempts to start. No vm_bundles folder is created.

What Should Happen?

Cowork should detect that all virtualization prerequisites are met and successfully initialize the VM workspace.

Error Messages/Logs

2026-03-19 13:41:39 [info] [cleanupVMBundleIfUnsupported] yukonSilver not supported (status=unsupported), checking for stale bundle...

Steps to Reproduce

1. Install Claude Desktop (latest) on Windows 11 Pro 25H2
2. Enable Hyper-V, Virtual Machine Platform, and Windows Hypervisor Platform
3. Confirm CoworkVMService is Running
4. Open Claude Desktop and navigate to the Cowork tab
5. Observe: Cowork shows "Virtual Machine Platform not available" error
6. Check log at %LOCALAPPDATA%\Packages\Claude_pzs8sxrjxfjjc\LocalCache\Roaming\Claude\logs\cowork_vm_node.log

Claude Model

None

Is this a regression?

Yes, this worked in a previous version

Last Working Version

_No response_

Claude Code Version

2.1.78

Platform

Anthropic API

Operating System

Windows

Terminal/Shell

PowerShell

Additional Information

• CPU: Intel Core i5-1345U (13th Gen, x64)
• OS Build: 26200.7171
• Installation: claude.com/download (MSIX package via Claude_pzs8sxrjxfjjc)
• Microsoft-Hyper-V-All: Enabled
• HypervisorPlatform: Enabled
• VirtualMachinePlatform: Enabled
• CoworkVMService: Running
• BIOS virtualization: Enabled and confirmed
• Full clean reinstall performed — issue persists
• Related issues: #30997, #32004, #27316, #29887