[BUG] Cowork Windows 11 Pro: HCS fails to mount VHDX from MSIX LocalCache with 0xC03A001A despite clean file attributes

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?

Windows 11 Pro, Intel i3-12100, Claude 1.3109.0.0, Hyper-V active, MSIX-setup. Mount-VHD successfully mount smol-bin.vhdx, but HcsStartComputeSystem falls with 0xC03A00

cowork-service.log

What Should Happen?

Cowork should work.

Error Messages/Logs

Steps to Reproduce

Install Claude, run Cowork - falls with error

Claude Model

None

Is this a regression?

I don't know

Last Working Version

_No response_

Claude Code Version

1.3109.0 (35cbf6)

Platform

Anthropic API

Operating System

Windows

Terminal/Shell

PowerShell

Additional Information

<img width="1901" height="999" alt="Image" src="https://github.com/user-attachments/assets/b99f315a-ba83-4d23-9e94-790e2b541f89" />