[BUG]#78858

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?

Title: Missing HCS services: vfpext.sys not present on disk — persists after Hyper-V enable + DISM/SFC repair (Windows 11 Pro 25H2)

What's Wrong?
Cowork in Claude Desktop shows "Missing HCS services: vfpext" and the Cowork tab remains disabled. vfpext.sys does not exist at C:\Windows\System32\drivers\vfpext.sys, confirmed via Test-Path. This persists after fully enabling Hyper-V and Virtual Machine Platform, with hns and vmcompute both confirmed Running.

Environment

Windows 11 Pro, Version 25H2, OS Build 26200.8973
Originally on Windows 11 Home, upgraded to Pro specifically to resolve this issue — problem persisted after upgrade
CPU virtualization (VT-x/AMD-V): Enabled in BIOS, confirmed via Task Manager

Steps taken

Enable-WindowsOptionalFeature -Online -FeatureName VirtualMachinePlatform -All → restarted
Enable-WindowsOptionalFeature -Online -FeatureName Microsoft-Hyper-V-All → restarted
DISM /Online /Cleanup-Image /RestoreHealth + sfc /scannow → (fill in result once complete)

Diagnostic output

Get-WindowsOptionalFeature -Online -FeatureName Microsoft-Hyper-V-All
State: Enabled

Get-Service vmcompute, hns
hns — Running — Host Network Service
vmcompute — Running — Hyper-V Host Compute Service

Test-Path C:\Windows\System32\drivers\vfpext.sys
False

Expected behavior
Either vfpext.sys installs correctly via the standard Hyper-V/VMP feature-enable path, or Cowork provides a clearer diagnostic pointing specifically to the missing driver file rather than the generic "Missing HCS services" message.

Additional notes
This matches the pattern in #78858 and #80584 — driver missing entirely from disk, not merely unregistered, and not resolved by feature toggles or a Windows edition upgrade (Home → Pro).

What Should Happen?

Expected behavior
Either vfpext.sys installs correctly via the standard Hyper-V/VMP feature-enable path, or Cowork provides a clearer diagnostic pointing specifically to the missing driver file rather than the generic "Missing HCS services" message.

Error Messages/Logs

Steps to Reproduce

Steps taken

Enable-WindowsOptionalFeature -Online -FeatureName VirtualMachinePlatform -All → restarted
Enable-WindowsOptionalFeature -Online -FeatureName Microsoft-Hyper-V-All → restarted
DISM /Online /Cleanup-Image /RestoreHealth + sfc /scannow → (fill in result once complete)

Claude Model

None

Is this a regression?

Yes, this worked in a previous version

Last Working Version

_No response_

Claude Code Version

4.6

Platform

Anthropic API

Operating System

Windows

Terminal/Shell

Windows Terminal

Additional Information

This matches the pattern in #78858 and #80584 — driver missing entirely from disk, not merely unregistered, and not resolved by feature toggles or a Windows edition upgrade (Home → Pro).