[BUG] MSIX Installation failure: AddPackage failed with HRESULT 0x80073CF9

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?

Issue: I was offered an upgrade in the desktop application this morning, and now the Claude Desktop (MSIX) Installation Fails on Windows with error: AddPackage failed with HRESULT 0x80073CF9

(I want to add that I had a similar drama on the 28th when an upgrade entirely broke my installation and I spent multiple hours, including rebooting into WinRE mode (turned out neither Administrator nor even Safe mode had enough rights or reach to fix the things that needed to be fixed and requiring very deep system installer db surgery) to clean up the problem, eventually succeeding and which allowed the desktop app to install cleanly and successfully. Then today I was offered an upgrade expecting everything to be fine but being surprised that it's again failing. Consequently there seems to be some kind of bug and I'm filing this report.)

Edit: I have since managed to work around this very infuriating issue (see comment below). I also see that this error seem to have been reported multiple times and closed with varying levels of "not planned" or "duplicate"?! To note, this issue seems quite serious, it either makes Claude Cowork unusable and can end up losing state if not properly recovered.

In the log there are error messages mention a conflict with CoworkVMService which sounds relevant:

2026/07/04 12:15:14.849126 Removing conflicting CoworkVMService... 2026/07/04 12:15:14.849726 WARNING: failed to remove conflicting service: could not open CoworkVMService: Access is denied.

What Should Happen?

Claude MSIX installer should install and/or upgrade without errors.

Error Messages/Logs

1.)  

> ---------------------------
> Claude Setup
> ---------------------------
> Installation failed: AddPackage failed: AddPackage failed with HRESULT 0x80073CF9
> 
> Please share this log with us.
> 
> The log file will be opened in Explorer.
> ---------------------------
> OK   
> ---------------------------

When you click OK this is followed by

2.)

> ---------------------------
> Claude Setup
> ---------------------------
> Administrator access is required to install Claude with full features. You can try again or install without Cowork.
> 
> Diagnostic log saved to:
> C:\Users\<user>\AppData\Local\Temp\ClaudeSetup.log
> ---------------------------
> OK   
> ---------------------------
> 

This is a red herring, the installer was run as administrator (was elevated on demand).


3.) The log:
> 2026/07/04 12:15:00.616259 Log file: C:\Users\<user>\AppData\Local\Temp\ClaudeSetup.log
> 2026/07/04 12:15:00.617285 === Claude Setup 259c3fc2a647e4222ca15e99bba9b2649f31f051 started ===
> 2026/07/04 12:15:00.618331 AllowAllTrustedApps not found (sideloading assumed enabled): The system cannot find the file specified.
> 2026/07/04 12:15:00.618331 Windows edition: Professional
> 2026/07/04 12:15:00.619365 WARNING: CoworkVMService already exists (potential conflict)
> 2026/07/04 12:15:00.619365 Windows version: 10.0.26200
> 2026/07/04 12:15:00.619365 Native arch: x64
> 2026/07/04 12:15:00.619365 Elevation type: Limited
> 2026/07/04 12:15:00.619365 Is elevated: false
> 2026/07/04 12:15:00.619365 Sideloading enabled: true
> 2026/07/04 12:15:00.619365 S Mode: false
> 2026/07/04 12:15:00.619365 Conflicting service: true
> 2026/07/04 12:15:00.619365 Running in non-elevated context
> 2026/07/04 12:15:00.619365 User can elevate — installing MSIX directly
> 2026/07/04 12:15:00.642419 Splash: 400x300, 8 frame(s), animated=true
> 2026/07/04 12:15:00.642419 System DPI: 96 (scale: 100%)
> 2026/07/04 12:15:00.696025 MSIX URL: https://api.anthropic.com/api/desktop/win32/x64/msix/latest/redirect
> 2026/07/04 12:15:00.696548 Downloading MSIX to C:\Users\<user>\AppData\Local\Temp\Claude-760157024.msix
> 2026/07/04 12:15:00.711069 proxy: WinHttpGetProxyForUrl("https://api.anthropic.com/api/desktop/win32/x64/msix/latest/redirect"): winapi error #12167
> 2026/07/04 12:15:01.130979 proxy: WinHttpGetProxyForUrl("https://downloads.claude.ai/releases/win32/x64/1.18286.0/Claude-259c3fc2a647e4222ca15e99bba9b2649f31f051.msix"): winapi error #12167
> 2026/07/04 12:15:02.490565 Download progress: 10% (23560016 / 235564380 bytes)
> 2026/07/04 12:15:03.713825 Download progress: 20% (47120032 / 235564380 bytes)
> 2026/07/04 12:15:04.605131 Download progress: 30% (70679472 / 235564380 bytes)
> 2026/07/04 12:15:05.515893 Download progress: 40% (94239488 / 235564380 bytes)
> 2026/07/04 12:15:06.722362 Download progress: 50% (117800064 / 235564380 bytes)
> 2026/07/04 12:15:07.633454 Download progress: 60% (141360080 / 235564380 bytes)
> 2026/07/04 12:15:08.524083 Download progress: 70% (164903136 / 235564380 bytes)
> 2026/07/04 12:15:09.503499 Download progress: 80% (188479536 / 235564380 bytes)
> 2026/07/04 12:15:10.394853 Download progress: 90% (212040112 / 235564380 bytes)
> 2026/07/04 12:15:11.303386 Download progress: 100% (235564380 / 235564380 bytes)
> 2026/07/04 12:15:11.304405 Download complete: 235564380 bytes, SHA256: 7927bafc45478d87d3213d9b9afb27bba58bc32b4fe9aa58a106cbfc139d0d3c
> 2026/07/04 12:15:11.305436 Download complete
> 2026/07/04 12:15:11.323277 Self-elevating: C:\Users\<user>\Downloads\Claude Setup.exe --elevated --msix-path "C:\Users\<user>\AppData\Local\Temp\Claude-760157024.msix" --log-path "C:\Users\<user>\AppData\Local\Temp\ClaudeSetup.log"
> 2026/07/04 12:15:13.653628 Waiting for elevated process to complete...
> 2026/07/04 12:15:13.673404 Log file: C:\Users\<user>\AppData\Local\Temp\ClaudeSetup.log
> 2026/07/04 12:15:13.674476 === Claude Setup 259c3fc2a647e4222ca15e99bba9b2649f31f051 started ===
> 2026/07/04 12:15:13.676688 AllowAllTrustedApps not found (sideloading assumed enabled): The system cannot find the file specified.
> 2026/07/04 12:15:13.676688 Windows edition: Professional
> 2026/07/04 12:15:13.677742 WARNING: CoworkVMService already exists (potential conflict)
> 2026/07/04 12:15:13.677742 Windows version: 10.0.26200
> 2026/07/04 12:15:13.677742 Native arch: x64
> 2026/07/04 12:15:13.677742 Elevation type: Full
> 2026/07/04 12:15:13.677742 Is elevated: true
> 2026/07/04 12:15:13.678267 Sideloading enabled: true
> 2026/07/04 12:15:13.678267 S Mode: false
> 2026/07/04 12:15:13.678267 Conflicting service: true
> 2026/07/04 12:15:13.678267 Running in elevated context
> 2026/07/04 12:15:13.678267 Installing MSIX from C:\Users\<user>\AppData\Local\Temp\Claude-760157024.msix (all-users: false)
> 2026/07/04 12:15:13.708180 Splash: 400x300, 8 frame(s), animated=true
> 2026/07/04 12:15:13.708180 System DPI: 96 (scale: 100%)
> 2026/07/04 12:15:13.763091 Verifying Authenticode signature on C:\Users\<user>\AppData\Local\Temp\Claude-760157024.msix
> 2026/07/04 12:15:14.527892 WinVerifyTrust: MSIX signature is valid
> 2026/07/04 12:15:14.834997 Signature verified: MSIX signer matches bootstrapper
> 2026/07/04 12:15:14.836139 Extracted family name from MSIX manifest: Claude_pzs8sxrjxfjjc
> 2026/07/04 12:15:14.836139 Squirrel process prefix: c:\users\<user>\appdata\local\anthropicclaude\
> 2026/07/04 12:15:14.836139 Checking for running Squirrel Claude processes...
> 2026/07/04 12:15:14.849126 No Squirrel Claude processes found
> 2026/07/04 12:15:14.849126 Removing conflicting CoworkVMService...
> 2026/07/04 12:15:14.849726 WARNING: failed to remove conflicting service: could not open CoworkVMService: Access is denied.
> 2026/07/04 12:15:14.849726 Checking for existing Claude MSIX packages...
> 2026/07/04 12:15:14.868893 Removing: Claude_1.15962.1.0_x64__pzs8sxrjxfjjc
> 2026/07/04 12:15:14.873020 Windows rejected data-preserving removal for Claude_1.15962.1.0_x64__pzs8sxrjxfjjc (0x80073CFA, requires developer mode); relying on in-place update
> 2026/07/04 12:15:14.873020 Removing: Claude_1.18286.0.0_x64__pzs8sxrjxfjjc
> 2026/07/04 12:15:14.876620 Windows rejected data-preserving removal for Claude_1.18286.0.0_x64__pzs8sxrjxfjjc (0x80073CFA, requires developer mode); relying on in-place update
> 2026/07/04 12:15:14.893868 Removing (user): Claude_1.15962.1.0_x64__pzs8sxrjxfjjc
> 2026/07/04 12:15:14.897919 Windows rejected data-preserving removal for Claude_1.15962.1.0_x64__pzs8sxrjxfjjc (0x80073CFA, requires developer mode); relying on in-place update
> 2026/07/04 12:15:14.897919 Installing MSIX: C:\Users\<user>\AppData\Local\Temp\Claude-760157024.msix
> 2026/07/04 12:15:14.897919 Standard install (not split-account), using AddPackage
> 2026/07/04 12:15:14.897919 Installing via AddPackage (current-user)...
> 2026/07/04 12:15:15.932253 MSIX installation failed: AddPackage failed: AddPackage failed with HRESULT 0x80073CF9
> 2026/07/04 12:15:15.932253 ERROR dialog (opening log): Installation failed: AddPackage failed: AddPackage failed with HRESULT 0x80073CF9
> 
> Please share this log with us.
> 2026/07/04 12:15:34.118582 Elevated process exited with code 1
> 2026/07/04 12:15:34.118582 Elevation failed: elevated installer exited with code 1
> 2026/07/04 12:15:34.118582 ERROR dialog (with log path): Administrator access is required to install Claude with full features. You can try again or install without Cowork.

Steps to Reproduce

1. Attempt to upgrade and/or run the Claude MSIX installer on a machine with the HyperV enabled and Docker Desktop installed and active and with an existing Claude desktop application installed and with the Cowork service provisioned.
2. Observe the above error messages and log entries.

Claude Model

None

Is this a regression?

Yes, this worked in a previous version

Last Working Version

_No response_

Claude Code Version

2.1.201 (Claude Code)

Platform

Anthropic API

Operating System

Windows

Terminal/Shell

Windows Terminal, Powershell 7.6.3

Additional Information

Note this is not Claude Code (CLI) issue. Claude Code works fine. This is the Claude desktop/Cowork application that is failing to upgrade/install on Windows 11 due to apparent conflicts with pre-existing installation(s) and/or CoWork service(s), and this is now the second upgrade attempt this has happened. which is why I'm reporting this.

Note also: I have 2 Claude chats private, unshared, here and here) sessions, which may shed light on this problem and how I "fixed" it on the 28th, when it originally occurred.

While I managed to eventually get the application installed, this took several hours and many reboots, and I lost some work somehow from it all out of Cowork, so I'm disinclined to immediately try to force the matter again before at least filing this report and seeing if this might be an easy fix in the installer.