[BUG] Claude desktop installer fails with HRESULT 0x80073CF6 on Windows 11 Home

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?

The Claude desktop app installer fails every time with HRESULT 0x80073CF6 during the MSIX AddPackage step. The app cannot be installed at all. The error occurs consistently across multiple attempts, both with and without the Cowork feature.

What Should Happen?

The installer should successfully register the MSIX package and launch Claude.

Error Messages/Logs

Checking for existing Claude MSIX packages...
Installing MSIX: C:\Users\chaey\AppData\Local\Temp\Claude-*.msix
Extracted family name from MSIX manifest: Claude_pzs8sxrjxfjjc
Standard install (not split-account), using AddPackage
Installing via AddPackage (current-user)...
MSIX installation failed: AddPackage failed: AddPackage failed with HRESULT 0x80073CF6

(Full `ClaudeSetup.log` attached)

Steps to Reproduce

1. Download Claude Setup.exe
2. Run it (as normal user or directly as Administrator)
3. The installer downloads the MSIX (~220 MB), verifies the signature successfully
4. Self-elevates to Administrator
5. Fails at AddPackage (current-user) after ~17 seconds with HRESULT 0x80073CF6

Claude Model

Opus

Is this a regression?

Yes, this worked in a previous version

Last Working Version

_No response_

Claude Code Version

1.9659.2 (installer build 390d6ca38de808ca81aeccd2945d9c8be800f47d)

Platform

Other

Operating System

macOS

Terminal/Shell

Non-interactive/CI environment

Additional Information

• Attempted 4+ times with the same result
• MSIX signature verification passes each time (SHA256 matches)
• Elevation to Administrator succeeds
• Tried both "install with Cowork" and "install without Cowork" options

ClaudeSetup.log

• No existing Claude packages found by the installer prior to each attempt