[BUG] Cowork workspace fails to start — CoworkVMService cannot create named pipe due to WIN32_PACKAGED_PROCESS sandbox restrictions

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?

Environment

| Field | Value |
|-------|-------|
| Claude version | 1.2581.0.0 |
| Install method | MSIX package via .exe installer (sideloaded, SignatureKind: Developer) |
| Install path | C:\Program Files\WindowsApps\Claude_1.2581.0.0_x64__pzs8sxrjxfjjc\ |
| OS | Windows 11 (Hyper-V enabled) |
| Hyper-V | Enabled, vmms running, user in Hyper-V Administrators group |

Steps to reproduce

1. Install Claude Desktop via the .exe installer from claude.ai/download
2. Launch Claude Desktop
3. Attempt to create or start a Cowork workspace

Expected behaviour

Workspace starts successfully and CoworkVMService creates the named pipe \\.\pipe\cowork-vm-service.

Actual behaviour

Two errors occur in sequence:

1. Claude Desktop shows: connect EPERM \\.\pipe\cowork-vm-service
2. After running as administrator, the pipe error is bypassed but workspace setup times out with: _Failed to start Claude's workspace — Request timed out: configure_

Root cause (diagnosed)

CoworkVMService is registered as TYPE: 210 WIN32_PACKAGED_PROCESS, which inherits MSIX AppContainer sandbox restrictions. This prevents the service from creating a named pipe even when running as LocalSystem.

A standard WIN32_OWN_PROCESS service type would not have this restriction. No Hyper-V VMs are ever created — the service fails before reaching that stage.

Service configuration

SERVICE_NAME: CoworkVMService
TYPE         : 210  WIN32_PACKAGED_PROCESS
START_TYPE   : 2    AUTO_START
SERVICE_START_NAME: LocalSystem
BINARY_PATH  : C:\Program Files\WindowsApps\Claude_1.2581.0.0_x64__pzs8sxrjxfjjc\app\resources\cowork-svc.exe

Relevant log output

C:\ProgramData\Claude\Logs\cowork-service.log:

Warning: failed to open service for recovery config: Access is denied.
[Server] Starting named pipe server on \\.\pipe\cowork-vm-service
Service error: failed to start server: failed to create named pipe:
  open \\.\pipe\cowork-vm-service: Access is denied.

Attempted mitigations

• Reinstalled Claude Desktop (multiple times) — no change
• Deleted all local data (%LocalAppData%\Claude, C:\ProgramData\Claude) and reinstalled — no change
• Verified user is in Hyper-V Administrators group (enabled, mandatory)
• Verified vmms service is running
• Running Claude as administrator — bypasses initial pipe error but workspace configure times out

Suggested fix

Register CoworkVMService as WIN32_OWN_PROCESS rather than WIN32_PACKAGED_PROCESS, or explicitly grant the MSIX AppContainer identity permission to create named pipes.

What Should Happen?

Workspace starts successfully and CoworkVMService creates the named pipe \\.\pipe\cowork-vm-service.

Error Messages/Logs

Steps to Reproduce

1. Install Claude Desktop via the .exe installer from claude.ai/download
2. Launch Claude Desktop
3. Attempt to create or start a Cowork workspace

Claude Model

None

Is this a regression?

I don't know

Last Working Version

_No response_

Claude Code Version

1.2581.0.0

Platform

Anthropic API

Operating System

Windows

Terminal/Shell

Other

Additional Information

_No response_