[BUG] Claude Desktop MSIX installation fails with HRESULT 0x80073CFF on Windows 11 Pro despite all preconditions passing — matches #60319

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?

Claude Desktop installer consistently fails at the MSIX AddPackage step with HRESULT 0x80073CFF, even though every precondition the installer itself checks reports as passing. This matches the pattern already reported in #60319.

Troubleshooting already completed (all failed to resolve):

Enabled Developer Mode (AllowDevelopmentWithoutDevLicense and AllowAllTrustedApps confirmed = 1 in HKLM\SOFTWARE\Microsoft\Windows\CurrentVersion\AppModelUnlock)
Found and cleared a conflicting Group Policy value (HKLM\SOFTWARE\Policies\Microsoft\Windows\Appx\AllowAllTrustedApps was set to 0, blocking sideloading at the policy level; corrected via gpedit.msc → App Package Deployment → "Allow all trusted apps to install" → Enabled, then gpupdate /force)
Confirmed no leftover/stuck Claude MSIX package: Get-AppxPackage -AllUsers | Where-Object {$_.Publisher -like "Anthropic"} returns nothing
Confirmed root certificate store integrity: certutil -verifystore -grouppolicy Root completes successfully
Confirmed UAC is at default/recommended level
Ran installer as Administrator directly (right-click → Run as administrator)
Multiple reinstall attempts across separate sessions

Log excerpt (ClaudeSetup.log):

2026/08/13 17:41:58.472515 === Claude Setup d1a6bcd4ef8627d603a8290548a984220b6701cf started ===
2026/08/13 17:41:58.473597 AllowDevelopmentWithoutDevLicense found with value: 1
2026/08/13 17:41:58.474110 Windows edition: Professional
2026/08/13 17:41:58.474110 Windows version: 10.0.26200
2026/08/13 17:41:58.474110 Native arch: x64
2026/08/13 17:41:58.474110 Elevation type: Full
2026/08/13 17:41:58.474110 Is elevated: true
2026/08/13 17:41:58.474110 Sideloading enabled: true
2026/08/13 17:41:58.474110 S Mode: false
2026/08/13 17:41:58.474110 Conflicting service: false
2026/08/13 17:41:58.474110 Running in elevated context
2026/08/13 17:41:58.489498 System DPI: 120 (scale: 125%)
2026/08/13 17:41:59.255843 WinVerifyTrust: MSIX signature is valid
2026/08/13 17:41:59.627193 Signature verified: MSIX signer matches bootstrapper
2026/08/13 17:41:59.644390 Extracted family name from MSIX manifest: Claude_pzs8sxrjxfjjc
2026/08/13 17:41:59.648681 No Squirrel Claude processes found
2026/08/13 17:41:59.659265 Standard install (not split-account), using AddPackage
2026/08/13 17:41:59.659265 Installing via AddPackage (current-user)...
2026/08/13 17:42:00.170363 MSIX installation failed: AddPackage failed: AddPackage failed with HRESULT 0x80073CFF
2026/08/13 17:42:07.996437 Elevated process exited with code 1
2026/08/13 17:42:07.996437 Elevation failed: elevated installer exited with code 1
2026/08/13 17:42:07.996437 ERROR dialog: Administrator access is required to install Claude with full features. You can try again or install without Cowork.

What Should Happen?

Claude Desktop should install successfully given all deployment preconditions pass.

Error Messages/Logs

2026/08/13 17:41:58.472515 === Claude Setup d1a6bcd4ef8627d603a8290548a984220b6701cf started ===
2026/08/13 17:41:58.473597 AllowDevelopmentWithoutDevLicense found with value: 1
2026/08/13 17:41:58.474110 Windows edition: Professional
2026/08/13 17:41:58.474110 Windows version: 10.0.26200
2026/08/13 17:41:58.474110 Native arch: x64
2026/08/13 17:41:58.474110 Elevation type: Full
2026/08/13 17:41:58.474110 Is elevated: true
2026/08/13 17:41:58.474110 Sideloading enabled: true
2026/08/13 17:41:58.474110 S Mode: false
2026/08/13 17:41:58.474110 Conflicting service: false
2026/08/13 17:41:58.489498 System DPI: 120 (scale: 125%)
2026/08/13 17:41:59.255843 WinVerifyTrust: MSIX signature is valid
2026/08/13 17:41:59.627193 Signature verified: MSIX signer matches bootstrapper
2026/08/13 17:41:59.659265 Installing via AddPackage (current-user)...
2026/08/13 17:42:00.170363 MSIX installation failed: AddPackage failed: AddPackage failed with HRESULT 0x80073CFF
2026/08/13 17:42:07.996437 Elevated process exited with code 1
2026/08/13 17:42:07.996437 ERROR dialog: Administrator access is required to install Claude with full features. You can try again or install without Cowork.

Steps to Reproduce

1. Download Claude Desktop installer from claude.com/download on Windows 11 Pro (build 10.0.26200)
2. Run the installer as Administrator
3. Installer reaches MSIX AddPackage step and fails immediately with HRESULT 0x80073CFF
4. Error dialog appears: "Administrator access is required to install Claude with full features. You can try again or install without Cowork." — but no "install without Cowork" button is actually present, only OK

Note: All installer-reported preconditions pass (sideloading enabled, elevated, not S Mode, valid signature) — see log excerpt. Confirmed no leftover Claude MSIX package registered, no blocking Group Policy, valid certificate store, Developer Mode enabled.

Claude Model

Opus

Is this a regression?

I don't know

Last Working Version

_No response_

Claude Code Version

N/A — this report is for the Claude Desktop installer, not Claude Code CLI

Platform

Anthropic API

Operating System

Windows

Terminal/Shell

PowerShell

Additional Information

_No response_