[BUG] Windows installer: 0x80073CF6 from orphaned WindowsApps folder — takeown/icacls insufficient, and the "install without Cowork" fallback has no button

### Preflight Checklist

- [x] I have searched [existing issues](https://github.com/anthropics/claude-code/issues?q=is%3Aissue%20state%3Aopen%20label%3Abug) 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?

Claude Desktop started erroring on launch. I uninstalled to reinstall, and every
reinstall since fails at MSIX registration with HRESULT 0x80073CF6.

The uninstall removed the package registration but left the files on disk:
C:\Program Files\WindowsApps\Claude_1.46388.2.0_x64__pzs8sxrjxfjjc (dated Sept 4).
That folder still claims the package family name, so AddPackage is rejected.

The folder is invisible to every standard tool:
- Get-AppxPackage -AllUsers *Claude* → empty
- Get-AppxProvisionedPackage -Online → no match
- HKLM\...\AppModel\Repository\Families\Claude_pzs8sxrjxfjjc → key does not exist
- Remove-AppxPackage -Package -AllUsers → exits silently, folder remains

This matches #49917 and #56949, with two additional findings:

**1. Taking ownership is not enough.** takeown /F /R /A /D Y followed by
icacls /grant "*S-1-5-32-544:(F)" /T /C both completed successfully
("Processados com sucesso 3110 arquivos; falha no processamento de 0 arquivos"),
and Rename-Item still returned access denied. Renaming a subfolder requires write
permission on the parent WindowsApps directory, which TrustedInstaller owns.
Ownership of the folder's own contents doesn't help.

**2. The "install without Cowork" fallback is unreachable.** After the failure,
the installer shows a dialog reading "Administrator access is required to install
Claude with full features. You can try again or install without Cowork." That
dialog has a single OK button. There is no way to choose the fallback. Clicking OK
opens the log and exits — the log shows no further install attempt. Screenshot
attached.

## What Should Happen?

The installer should detect and clear a stuck package family name before calling
AddPackage, or ship a cleanup tool. Failing that, the fallback dialog should
actually expose the "install without Cowork" option as a button, since it is the
only recovery path the installer offers.

## How I Fixed It

Only via Windows Recovery Environment (Shift+Restart → Troubleshoot → Advanced →
Command Prompt), where TrustedInstaller isn't running:

ren "F:\Program Files\WindowsApps\Claude_1.46388.2.0_x64__pzs8sxrjxfjjc" "...old"

(drive letters are remapped in WinRE — the system volume was F: there, C: in Windows)

After that, the installer completed normally with Cowork.

## Environment

- Windows 11 Professional, 10.0.26200, x64
- Sideloading enabled, S Mode false, elevation confirmed (Is elevated: true)
- Setup builds: 1e236d9fa9efd21a5a0a66a7b70c028f48848604 and 41ad1dff5275eedc8af25989f59f33c5efe14063
- MSIX 1.49585.0, SHA256 dfc789cb60a88a5ba794c25903ebfc0f4552c650a157933b056c984366dbedca
- Stale package: Claude_1.46388.2.0_x64__pzs8sxrjxfjjc

Note: this is a Claude Desktop installer bug, not Claude Code. Filing here because #49917 and #56949 track the same issue in this repo.

Full ClaudeSetup.log attached.

[ClaudeSetup.log](https://github.com/user-attachments/files/31987029/ClaudeSetup.log)

### What Should Happen?

The installer should detect and clear a stuck package family name before calling
AddPackage, or ship a cleanup tool for this scenario.

Failing that, the fallback dialog should actually expose "install without Cowork"
as a button. Right now it describes the option in text but offers only OK, so the
only recovery path the installer advertises is unreachable.

### Error Messages/Logs

```shell
MSIX installation failed: AddPackage failed: AddPackage failed with HRESULT 0x80073CF6
ERROR dialog (opening log): Installation failed: AddPackage failed with HRESULT 0x80073CF6
Elevated process exited with code 1
ERROR dialog (with log path): Administrator access is required to install Claude with
full features. You can try again or install without Cowork.

Full ClaudeSetup.log attached.
```

### Steps to Reproduce

1. Have Claude Desktop installed (MSIX, version 1.46388.2.0)
2. App starts failing on launch; uninstall it
3. Uninstall removes the package registration but leaves
C:\Program Files\WindowsApps\Claude_1.46388.2.0_x64__pzs8sxrjxfjjc on disk
4. Run Claude Setup.exe again
5. MSIX downloads and signature verifies; AddPackage fails ~13s in with 0x80073CF6
6. Dialog offers "install without Cowork" but has only an OK button
7. Get-AppxPackage -AllUsers *Claude* returns nothing, so no standard uninstall
or repair path applies

### Claude Model

None

### Is this a regression?

I don't know

### Last Working Version

_No response_

### Claude Code Version

N/A — Claude Desktop installer, not Claude Code CLI

### Platform

Anthropic API

### Operating System

Windows

### Terminal/Shell

PowerShell

### Additional Information

Note: this is a Claude Desktop installer bug, not Claude Code. Filing here because
#49917 and #56949 track the same issue in this repo.

Resolved only via Windows Recovery Environment (Shift+Restart → Troubleshoot →
Advanced → Command Prompt), renaming the orphaned folder there. Note that drive
letters are remapped in WinRE — the system volume was F: there, C: in Windows.
After the rename, the installer completed normally with Cowork.

Start with the attached ClaudeSetup.log and the Windows installer path that calls MSIX AddPackage, then reproduce the 0x80073CF6 case with an orphaned WindowsApps folder if possible. Also inspect the failure dialog that mentions installing without Cowork. Done means the installer either handles the stuck package-family cleanup path or exposes a working fallback button.

索引モデルが issue の本文から書いたものです。