[BUG] Cowork "HYPERVISOR_SERVICE_ERROR" on Windows 11 Pro — yukonSilver unsupported despite Hyper-V fully enabled, Cowork tab missing after reinstall

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?

Here's everything relevant from our conversation:

System Info:

OS: Microsoft Windows 11 Pro
Claude Desktop: Version 1.2581.0 (f10398)
Plan: (confirm your plan tier in the report)

Windows Features (from PowerShell):
FeatureName State
----------- -----
VirtualMachinePlatform Enabled
HypervisorPlatform Enabled
Microsoft-Hyper-V-Hypervisor Enabled
HyperV-KernelInt-VirtualDevice Disabled
HyperV-Guest-KernelInt Disabled

CoworkVMService: Running
bcdedit: hypervisorlaunchtype = Auto
Conflicting hypervisors (VMware/VirtualBox/Parallels/WSL): None found

cowork_vm_node.log (key error):
2026-04-15 13:58:55 [error] [VM:start] VM boot failed: HCS operation failed:
failed to create compute system: HcsWaitForOperationResult failed with HRESULT
0x80370102: {"Error":-2143878910,"ErrorMessage":"The virtual machine could not
be started because a required feature is not installed.","ErrorEvents":[
{"Message":"Cannot create system 'cowork-vm-eaaac18b' since Hyper-V is not
installed on the host."}]}
2026-04-15 13:58:55 [error] [VM:start] HCS error detected, available=true,
missing=[], sentinel=HYPERVISOR_SERVICE_ERROR
2026-04-15 13:58:55 [info] Dispatching startup error: HYPERVISOR_SERVICE_ERROR
2026-04-15 13:58:55 [warn] [VM:start] Heartbeat restart failed, leaving VM
offline (will retry on next app launch)
After reinstall (yukonSilver detection failure):
2026-04-15 14:10:02 [info] [cleanupVMBundleIfUnsupported] yukonSilver not
supported (status=unsupported), checking for stale bundle...
2026-04-15 14:10:04 [info] [cleanupVMBundleIfUnsupported] yukonSilver not
supported (status=unsupported), checking for stale bundle...

Steps already attempted:

Rebooted multiple times
Verified all virtualization features enabled in Windows Features
Confirmed bcdedit hypervisorlaunchtype = Auto
Confirmed no conflicting hypervisors
Restarted vmcompute service
Full uninstall including AppData cleanup and vm_bundles folder deletion
Reinstalled as Administrator
Issue persists across all attempts

What Should Happen?

Cowork should detect that all required virtualization features are enabled (Virtual Machine Platform, Hypervisor Platform, and Microsoft-Hyper-V-Hypervisor all confirmed Enabled on Windows 11 Pro), successfully initialize the VM workspace, and display the Cowork tab next to Chat in Claude Desktop.

Error Messages/Logs

Steps to Reproduce

Steps to Reproduce:

1. Install Claude Desktop (v1.2581.0) on Windows 11 Pro as Administrator
2. Verify all virtualization features are enabled (VirtualMachinePlatform, HypervisorPlatform, Microsoft-Hyper-V-Hypervisor)
3. Verify bcdedit hypervisorlaunchtype = Auto
4. Verify CoworkVMService is Running
5. Verify no conflicting hypervisors (VMware, VirtualBox, Parallels, WSL) are present
6. Launch Claude Desktop
7. Observe: Cowork tab is missing entirely, or if present shows "Virtualization is not available — Claude's workspace requires Virtual Machine Platform, but the virtualization service isn't responding"
8. Check %APPDATA%\Claude\logs\cowork_vm_node.log — shows HYPERVISOR_SERVICE_ERROR and yukonSilver not supported (status=unsupported) repeating on every launch
9. Restarting, reinstalling, and clearing vm_bundles folder does not resolve the issue

Claude Model

Sonnet (default)

Is this a regression?

No, this never worked

Last Working Version

_No response_

Claude Code Version

Version 1.2581.0 (f10398)

Platform

Anthropic API

Operating System

Windows

Terminal/Shell

PowerShell

Additional Information

Additional Notes:

Regular Chat works perfectly — issue is isolated entirely to Cowork
The error message "Hyper-V is not installed on the host" is contradicted by Get-WindowsOptionalFeature confirming Microsoft-Hyper-V-Hypervisor is Enabled
HRESULT 0x80370102 indicates Windows HCS (Host Compute Service) cannot create the VM despite hypervisor being active
yukonSilver not supported (status=unsupported) appears on every launch — the app is misclassifying this system as incompatible before even attempting to boot the VM
After full uninstall + AppData/vm_bundles cleanup + reinstall as Administrator, the Cowork tab disappeared entirely and only the yukonSilver unsupported loop remains in logs
No conflicting hypervisors present (VMware, VirtualBox, Parallels, WSL all absent)
This appears related to issues #25136, #27316, #27420, #29887, #32004, #42227, #45715