[BUG] Cowork - yukonSilver not supported on Windows 11 Pro, Intel Core Ultra 9 185H

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 tab shows "Virtual Machine Platform not available" on every launch. Log repeatedly shows "yukonSilver not supported (status=unsupported)" and never progresses.

This matches existing issues #32004, #27316, #27420, #29887.

Environment:

• OS: Windows 11 Pro
• Device: ASUS, Intel Core Ultra 9 185H
• Subscription: Pro
• Claude Desktop: latest version, clean install with admin rights
• Hyper-V: Enabled
• VirtualMachinePlatform: Enabled
• HypervisorPlatform: Enabled
• HyperVisorPresent: True
• CoworkVMService: Running, Automatic

Log output:
2026-04-05 21:37:57 [info] [cleanupVMBundleIfUnsupported] yukonSilver not supported (status=unsupported), checking for stale bundle...
2026-04-05 21:37:57 [info] [VM] Loading vmClient (TypeScript) module...
2026-04-05 21:37:57 [info] [VM] Module loaded successfully

VM never initialises. Clean reinstall makes no difference. Hardware fully supports virtualisation.

What Should Happen?

Cowork should detect that virtualisation is fully enabled, download the VM bundle, and allow access to the Cowork workspace without showing the "Virtual Machine Platform not available" error.

Error Messages/Logs

Virtual Machine Platform not available - prompts to enable feature and restart. Restarting does not resolve the issue.

From cowork_vm_node.log:
2026-04-05 21:37:57 [info] [cleanupVMBundleIfUnsupported] yukonSilver not supported (status=unsupported), checking for stale bundle...
2026-04-05 21:37:57 [info] [VM] Loading vmClient (TypeScript) module...
2026-04-05 21:37:57 [info] [VM] Module loaded successfully

This pattern repeats on every single launch. The VM never progresses past this check.

Steps to Reproduce

1. Install Claude Desktop (latest version) on Windows 11 Pro as administrator
2. Sign in with a Pro subscription account
3. Ensure Hyper-V, VirtualMachinePlatform, and HypervisorPlatform are all enabled in Windows Features
4. Open Claude Desktop
5. Click the Cowork tab
6. Observe "Virtual Machine Platform not available" error
7. Click "Restart now" as prompted
8. Reboot computer
9. Open Claude Desktop and navigate to Cowork tab again
10. Observe same error persists indefinitely

Claude Model

Sonnet (default)

Is this a regression?

No, this never worked

Last Working Version

NA

Claude Code Version

Claude Desktop Window

Platform

Other

Operating System

Windows

Terminal/Shell

Other

Additional Information

This is a known bug affecting multiple users on different hardware. Related issues: #32004, #27316, #27420, #29887. All share identical yukonSilver not supported log output.

User purchased Windows 11 Pro licence specifically to meet Cowork requirements. Hardware is fully capable. All virtualisation prerequisites confirmed via PowerShell. Clean reinstall with administrator privileges makes no difference. This is a platform detection bug in Claude Desktop, not a user configuration issue.

PowerShell verification:

• HyperVisorPresent: True
• VirtualMachinePlatform: Enabled
• HypervisorPlatform: Enabled
• Microsoft-Hyper-V-All: Enabled
• CoworkVMService: Running, Automatic