[BUG] Cowork "Virtualization is not available" on Windows 11 Enterprise Build 26200 — yukonSilver classified as unsupported despite all prerequisites met

[jacolouw99-eng]

Preflight Checklist

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

What's Wrong?

Cowork displays "Virtualization is not available — Claude's workspace requires Hyper-V, but the virtualization service isn't responding. Restart your computer to resolve this."

The Cowork enablement process gets stuck at 95% and then fails with Error code 1.

A full clean reinstall (removing MSIX package, old Squirrel remnants, VM bundles, logs, CoworkVMService, HNS networks, and temp files) did not resolve the issue. The yukonSilver detection bug reappears immediately after fresh installation.

What Should Happen?

Expected Behavior

Cowork should detect that Hyper-V is fully enabled and all virtualization services are running on Windows 11 Enterprise, successfully download the VM bundle, and launch the workspace.

Actual Behavior

Claude Desktop's internal platform classifier marks this system as yukonSilver not supported (status=unsupported), which prevents the VM bundle from ever being downloaded. The enablement process stalls at 95% and fails with exit code 1.

Error Messages/Logs

From `%LOCALAPPDATA%\Packages\Claude_pzs8sxrjxfjjc\LocalCache\Roaming\Claude\logs\cowork_vm_node.log`:


[info] [cleanupVMBundleIfUnsupported] yukonSilver not supported (status=unsupported), checking for stale bundle...


This entry repeats on every launch. The VM bundle is never downloaded. The `vm_bundles` directory is never created.

Steps to Reproduce

1. Install Claude Desktop v1.1.7714.0 from claude.com/download on Windows 11 Enterprise x64 (Build 26200)
2. Ensure all virtualization features are enabled (Hyper-V, VMP, WHP)
3. Confirm all services running (vmcompute, vmms, CoworkVMService)
4. Launch Claude Desktop
5. Click the Cowork tab
6. Observe: Enablement gets stuck at 95%, fails with Error code 1
7. Observe: "Virtualization is not available" error

Claude Model

Opus

Is this a regression?

No, this never worked

Last Working Version

No response

Claude Code Version

2.1.78 (Claude Code)

Platform

Anthropic API

Operating System

Windows

Terminal/Shell

Terminal.app (macOS)

Additional Information

Expected Behavior

Cowork should detect that Hyper-V is fully enabled and all virtualization services are running on Windows 11 Enterprise, successfully download the VM bundle, and launch the workspace.

Actual Behavior

Claude Desktop's internal platform classifier marks this system as yukonSilver not supported (status=unsupported), which prevents the VM bundle from ever being downloaded. The enablement process stalls at 95% and fails with exit code 1.

Troubleshooting Already Attempted

• ❌ Full clean reinstall (removed MSIX package, Squirrel remnants, VM bundles, logs, temp files, CoworkVMService, HNS networks)
• ❌ Fresh download from claude.com/download, installed as Administrator
• ❌ Verified all Hyper-V features enabled via Get-WindowsOptionalFeature
• ❌ Confirmed bcdedit hypervisorlaunchtype set to Auto
• ❌ No VPN active
• ❌ No Docker, WSL2, or other VM conflicts
• ❌ Multiple reboots

Additional Notes

• Regular Chat mode works perfectly. Only Cowork is affected.
• This appears to be the same yukonSilver classification issue reported in [BUG] Cowork for windows: yukonSilver not supported #25034, [BUG] Cowork tab not showing on Windows 11 Pro x64 — "yukonSilver" marked as unsupported + CoworkVMService cannot be removed #25136, [BUG] Cowork shows "Virtualization is not enabled" on Windows 10 Pro despite Hyper-V fully enabled #27316, [BUG] Cowork: yukonSilver classified as unsupported on fully capable Windows 11 Pro x64 (i5-14600K) #27357, [BUG] Cowork says "Virtualization is not available" — but Hyper-V is alive and well. Claude just won't believe it. #29532, [BUG] Cowork "Virtualization is not available" — yukonSilver classified as unsupported on Windows 10 Pro with Hyper-V fully enabled #30997, [BUG] Cowork shows "Virtual Machine Platform not available" — yukonSilver marked as unsupported despite all virtualization features enabled #32004, [BUG] Cowork "Virtualization is not available" on Windows 11 Enterprise despite Hyper-V and CoworkVMService fully running #32280, and [BUG] Cowork shows "Virtualization is not available" on Windows 11 Pro despite Hyper-V fully enabled and services running** #32574.
• The growthbook feature flag system loads on startup, suggesting the "unsupported" status may be server-side rather than local detection.
• This is NOT a system configuration issue — all system-level checks confirm Hyper-V is properly installed, running, and functional.

Related Issues

• [BUG] Cowork for windows: yukonSilver not supported #25034 — Same bug on Windows 11 Enterprise
• [BUG] Cowork tab not showing on Windows 11 Pro x64 — "yukonSilver" marked as unsupported + CoworkVMService cannot be removed #25136 — yukonSilver unsupported + CoworkVMService cannot be removed
• [BUG] Cowork shows "Virtualization is not enabled" on Windows 10 Pro despite Hyper-V fully enabled #27316 — Same bug on Windows 10 Pro
• [BUG] Cowork: yukonSilver classified as unsupported on fully capable Windows 11 Pro x64 (i5-14600K) #27357 — yukonSilver unsupported on Windows 11 Pro (i5-14600K)
• [BUG] Cowork says "Virtualization is not available" — but Hyper-V is alive and well. Claude just won't believe it. #29532 — Hyper-V alive and well, Claude won't believe it
• [BUG] Cowork "Virtualization is not available" — yukonSilver classified as unsupported on Windows 10 Pro with Hyper-V fully enabled #30997 — yukonSilver classified as unsupported on Windows 10 Pro
• [BUG] Cowork shows "Virtual Machine Platform not available" — yukonSilver marked as unsupported despite all virtualization features enabled #32004 — yukonSilver unsupported despite all features enabled
• [BUG] Cowork "Virtualization is not available" on Windows 11 Enterprise despite Hyper-V and CoworkVMService fully running #32280 — Same bug on Windows 11 Enterprise
• [BUG] Cowork shows "Virtualization is not available" on Windows 11 Pro despite Hyper-V fully enabled and services running** #32574 — Same bug on Windows 11 Pro

[github-actions]

Closing for now — this doesn't appear to be about Claude Code. Please open a new issue if this is still relevant.

[github-actions]

This issue has been automatically locked since it was closed and has not had any activity for 7 days. If you're experiencing a similar issue, please file a new issue and reference this one if it's relevant.