[BUG]Cowork "Virtualization not available" / HRESULT 0x80370102 — root cause is BIOS VT-x disabled, but error message gives no indication of this

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 displays "Virtualization is not available — Claude's workspace requires Hyper-V, but the virtualization service isn't responding" despite Hyper-V being fully installed and configured in Windows.

The root cause — confirmed after extensive troubleshooting — was that Intel VT-x (hardware virtualisation) was disabled in BIOS/UEFI. Once enabled in BIOS, (Get-CimInstance Win32_ComputerSystem).HypervisorPresent returned True and Cowork launched successfully.

This is almost certainly affecting a significant number of users who are going through the same multi-hour troubleshooting process unnecessarily.

What Should Happen?

The error message should check HypervisorPresent and if False, display something like:
"Hardware virtualisation is not active. Please check that Intel Virtualization Technology (VT-x) or AMD-V is enabled in your BIOS/UEFI settings."
This single change would save users hours of troubleshooting and potentially unnecessary expense (Windows Pro upgrade).

Error Messages/Logs

Steps to Reproduce

1. Have a PC with Intel VT-x disabled in BIOS (this is the default on some motherboards)
2. Install Windows 11 Pro, enable Hyper-V, Virtual Machine Platform, Windows Hypervisor Platform
3. Install Claude Desktop (latest MSIX via ClaudeSetup.exe)
4. Open Cowork tab
5. Error appears: "Virtualization is not available"

Claude Model

None

Is this a regression?

I don't know

Last Working Version

_No response_

Claude Code Version

1.1.6679.0

Platform

Anthropic API

Operating System

Windows

Terminal/Shell

Non-interactive/CI environment

Additional Information

Diagnostic Journey — What Was Tried Before Finding Root Cause
All of the following were attempted and did NOT resolve the issue:

Restarting computer multiple times
Upgrading from Windows 11 Home to Pro (CHF 160 / ~$170 spent)
Running Enable-WindowsOptionalFeature -Online -FeatureName Microsoft-Hyper-V -All
Running bcdedit /set hypervisorlaunchtype auto
Full uninstall, deletion of %APPDATA%\Claude and %LOCALAPPDATA%\Packages\Claude_*, clean reinstall
Manually taking ownership of and running cowork-svc.exe install
Manually starting CoworkVMService and HvHost services
Running dism /online /enable-feature /featurename:Microsoft-Hyper-V-All

The actual fix took 30 seconds once identified: enter BIOS → enable Intel Virtualization Technology (VT-x) → save → reboot.

Root Cause
(Get-CimInstance Win32_ComputerSystem).HypervisorPresent returning False is the definitive indicator. Windows can have Hyper-V fully installed and configured, but if VT-x is disabled in BIOS the hypervisor never activates at the kernel level, causing HRESULT 0x80370102.
The cowork_vm_node.log shows:
[VM:start] VM boot failed: HCS operation failed: failed to create compute system:
HcsWaitForOperationResult failed with HRESULT 0x80370102:
{"ErrorMessage":"The virtual machine could not be started because a required feature is not installed.",
"ErrorEvents":[{"Message":"Cannot create system 'cowork-vm' since Hyper-V is not installed on the host."}]}

Suggested Fix
Before showing any Cowork error, Claude Desktop should run:

Check (Get-CimInstance Win32_ComputerSystem).HypervisorPresent
If False → show "Enable VT-x/AMD-V in BIOS" message
If True but service failing → show current "restart" message

Related Issues: #27316, #27384, #29532, #30997, #32588