[BUG] Cowork: MSIX installation fails with 0x80073CF6 after full uninstall — Windows 11 Pro

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 fails to install with HRESULT 0x80073CF6 at the AddPackage step. After a full uninstall and registry cleanup, the installer downloads successfully, validates the signature, but fails every time when registering the MSIX package. Error persists across multiple reinstall attempts and running as administrator.

ClaudeSetup.log

What Should Happen?

Claude Desktop should install successfully and Cowork should initialize, download the VM bundle, and start the VM service.

Error Messages/Logs

MSIX installation failed: AddPackage failed: AddPackage failed with HRESULT 0x80073CF6

Steps to Reproduce

1. Uninstall Claude via Remove-AppxPackage
2. Remove %LOCALAPPDATA%\Packages\Claude_pzs8sxrjxfjjc and %APPDATA%\Claude
3. Restart AppXSvc service
4. Download fresh installer from claude.ai/download
5. Run installer — fails at AddPackage after ~9 seconds
6. Run installer as administrator — same result

Claude Model

None

Is this a regression?

Yes, this worked in a previous version

Last Working Version

_No response_

Claude Code Version

can't reinstall so can't tell you

Platform

Other

Operating System

Windows

Terminal/Shell

PowerShell

Additional Information

Hyper-V is enabled and vmcompute/vmms are both running. Registry shows no stale Claude entries. Package folder was nearly empty before uninstall (only SystemAppData present, no vm_bundles). Max plan subscriber. desktop app for windows