[BUG] Cowork workspace fails with HCS 0x80070003 on Plan9 share 'z' — Windows 11 with pre-existing Z: drive (Microsoft Store version)

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?

What's Wrong?

Cowork workspace fails to start on Windows 11 with the following error:

failed to add Plan9 share 'z': HcsWaitForOperationResult failed with HRESULT 0x80070003: {"Error":-2147024893,"ErrorMessage":""}

Environment:

• OS: Windows 11 x64
• Claude Desktop: 1.569.0.0 (Microsoft Store / MSIX)
• Hyper-V: Enabled
• User added to Hyper-V Administrators group
• Other VM present in Hyper-V Manager (Windows 11 dev environment, State: Off)

Expected behavior:
Cowork should either use a dynamic/configurable drive letter for Plan9 shares, or correctly resolve the MSIX package path without requiring manual workarounds.

What Should Happen?

Root causes identified during debugging:

1. Z: drive conflict: The app hardcodes 'z' as the Plan9 share drive letter. My environment had a pre-existing Z: drive assigned to an unformatted SSD partition (DriveType 3, mounted via mountvol). This caused HRESULT 0x80070005 (Access Denied). After removing the Z: drive assignment via mountvol Z: /D, the error changed to 0x80070003 (Path Not Found).

1. Path mismatch: The app references C:\Users\<username>\AppData\Roaming\Claude\vm_bundles\claudevm.bundle as bundlePath, but the Microsoft Store version actually stores data under C:\Users\<username>\AppData\Local\Packages\Claude_pzs8sxrjxfjjc\LocalCache\Roaming\Claude\vm_bundles. Neither a symbolic link nor a direct folder copy resolved the 0x80070003 error.

Error Messages/Logs

**Relevant log excerpt (cowork_vm_node.log):**

[VM:steps] vm_boot completed (725ms)
[VM:steps] add_plan9_shares started
[VM:start] VM boot failed: failed to add Plan9 share 'z': HcsWaitForOperationResult failed with HRESULT 0x80070003

Steps to Reproduce

Steps to reproduce:

1. Install Claude Desktop (Microsoft Store version) on Windows 11
2. Have a pre-existing Z: drive assigned in the system
3. Open Cowork tab → error appears immediately
4. Removing Z: drive assignment changes error from 0x80070005 to 0x80070003
5. Error persists despite symlink workarounds and folder copy

Claude Model

None

Is this a regression?

Yes, this worked in a previous version

Last Working Version

_No response_

Claude Code Version

1.569.0.0

Platform

Anthropic API

Operating System

Windows

Terminal/Shell

PowerShell

Additional Information

_No response_