[BUG] Cowork VM fails with HCS 0x800707de due to duplicate Plan9 shares from race condition in configure calls

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 with HCS error 0x800707de on every attempt. The root cause is a race condition: Claude Desktop sends multiple simultaneous configure requests to the CoworkVMService, and each one adds a Plan9 share without deduplication. This results in duplicate identical entries in the HCS config:

"Plan9": {
"Shares": [
{ "AccessName": "home", "Name": "home", "Path": "C:\\Users\\dmrad", "Port": 9999 },
{ "AccessName": "home", "Name": "home", "Path": "C:\\Users\\dmrad", "Port": 9999 }
]
}

HcsCreateComputeSystem returns hr=0x0 (success), but HcsWaitForOperationResult then fails with hr=0x800707de during the Construct phase — consistent with a duplicate resource conflict.

The logs clearly show the race condition:

• Two method=configure requests arrive within the same millisecond
• Two [VM] Plan9 share added: home -> C:\Users\dmrad (port=9999) lines are logged
• The VM then enters a retry loop, failing every time with the same duplicate config

Tried so far (none resolved it):

• Deleting vm_bundles\claudevm.bundle and letting it recreate
• Restarting the computer
• Restarting CoworkVMService

Environment:

• Claude Desktop v1.1.5749.0 (Microsoft Store)
• Windows user: dmrad
• App version shown in UI: 2.4

What Should Happen?

The CoworkVMService should deduplicate Plan9 shares before passing the config to HCS. When multiple concurrent configure requests arrive, the service should either serialize them or ensure that adding a share with the same name is idempotent — resulting in exactly one Plan9 share entry in the HCS config. The VM should then start successfully.

Error Messages/Logs

HCS operation failed: failed to create compute system: HcsWaitForOperationResult failed with HRESULT 0x800707de: {"Error":-2147022882,"ErrorMessage":"","Attribution":[{"OperationFailure":{"Detail":"Construct"}}]}

Steps to Reproduce

cowork-service.log

Claude Model

Opus

Is this a regression?

Yes, this worked in a previous version

Last Working Version

1.1.5749.0

Claude Code Version

2.1.72

Platform

Anthropic API

Operating System

Windows

Terminal/Shell

Windows Terminal

Additional Information

_No response_