[BUG] Cowork fails with Plan9 share 'h' HCS error 0x80310000 on Windows — Chat workspace works fine

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 workspace fails to start on Windows with error:

"failed to add Plan9 share 'h': HcsWaitForOperationResult failed with HRESULT 0x80310000: {"Error":-2144272384,"ErrorMessage":""}"

Chat workspace works perfectly on the same machine. Cowork also works fine on my Mac (same account, Plan Max).

This has persisted for 4+ days despite extensive troubleshooting.

Note: HRESULT 0x80310000 differs from the 0x800707de reported in #31877 and #32172, suggesting a distinct failure path in the Plan9 share setup.

What Should Happen?

Cowork workspace should start successfully, as Chat workspace does on the same machine.

Error Messages/Logs

Impossible de démarrer l'espace de travail de Claude.
failed to add Plan9 share 'h': HcsWaitForOperationResult failed with HRESULT 0x80310000: {"Error":-2144272384,"ErrorMessage":""}
Redémarrer Claude ou votre ordinateur résout parfois ce problème. Si cela persiste, vous pouvez réinstaller l’espace de travail.

Steps to Reproduce

1. Open Claude Desktop on Windows
2. Click on Cowork tab
3. Error appears immediately

Claude Model

Not sure / Multiple models

Is this a regression?

Yes, this worked in a previous version

Last Working Version

1.1.381 - not sure

Claude Code Version

N/A — Cowork/Claude Desktop issue

Platform

Anthropic API

Operating System

Windows

Terminal/Shell

Windows Terminal

Additional Information

Environment:

• Hyper-V fully enabled (HypervisorPlatform: Enabled, vmcompute: Running, vmms: Running)
• BitLocker: Disabled
• Docker Desktop running, WSL2 active
• No VPN, no mapped network drives
• Disks: C: and D: only

Troubleshooting performed (all failed):

• Multiple PC restarts and Claude Desktop restarts
• Full uninstall + AppData cleanup + fresh reinstall from claude.ai/download
• "Reinstall workspace" link in error message
• Enabled HypervisorPlatform (was Disabled — this fixed Chat but not Cowork)
• Deleted %APPDATA%\Claude\vm_bundles to force re-download
• Restart-Service vmcompute/vmms
• ClaudeFix toolkit (github.com/JesperLive/ClaudeFix): VM creates via HCS but guest never responds — "HCS VM present but no log/guest activity" after 240s, all 3 retries failed
• docker context use default (fixed Docker CLI but unrelated to Cowork)

Older cowork_vm_node.log showed:

• "yukonSilver not supported (status=unsupported)"
• "rootfs.img missing"
• "@ant/claude-swift module not found" (on older app-1.1.381)

After reinstall to latest version:

• Plan9 share 'h' HCS error 0x80310000 consistently
• ClaudeFix confirms VM is created but stuck with no guest activity

Related issues: #31877, #32172, #25419