[BUG] Windows Server 2025: cumulative update KB5094125 (OS build 26100.32995) breaks MSIX registration — package lands "Modified, NeedsRemediation" despite deployment reporting success; removing the LCU fixes it

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 (MSIX, package family Claude_pzs8sxrjxfjjc) ran fine for months on Windows Server 2025. It broke immediately after a Windows Update + reboot on 2026-06-19. Only Windows changed — Claude itself was not updated.

After the update, every install either fails with AddPackage failed: AddPackage failed with HRESULT 0x80073CF6, or "completes" and the package immediately shows Status: Modified, NeedsRemediation with PackageUserInformation : {} (registered for no user) — even though the AppX deployment operational log reports the Register operation finished successfully (Event ID 400, 0x0).

Verified cause: the June 9, 2026 OS cumulative update KB5094125 (OS build 26100.32995). The three packages installed on 2026-06-19 map to:

• Package_for_RollupFix~31bf3856ad364e35~amd64~~26100.32995.1.21 → KB5094125 (the OS LCU) ← the one that needed removal
• Package_for_ServicingStack_32985~...~26100.32985.1.4 → KB5094137 (SSU) — left intact
• Package_for_DotNetRollup_481~...~10.0.9335.3 → KB5087051 (.NET, May 2026) — left intact, NOT the cause

Environment: Windows Server 2025 (Evaluation), build 10.0.26100.32995, x64, KVM guest (netcup VPS). Standard user with UAC elevation; built-in Administrator disabled. Microsoft Store present; non-MSIX .exe apps install fine, so the failure is specific to MSIX registration.

What did NOT durably fix it: Remove-AppxPackage + fresh install, Add-AppxPackage -Register, Reset-AppxPackage, DISM /RestoreHealth + sfc /scannow (helped once then the failure returned after reboot, SFC then clean), disabling CoworkVMService (Set-Service "Access is denied"; registry Start=4 reverts to 2 on boot; IFEO on cowork-svc.exe). Orphan MSIX folders, EFS and AV all excluded.

What fixed it (durable across reboots):
Get-AppxPackage Claude | Remove-AppxPackage
Remove-WindowsPackage -Online -PackageName "Package_for_RollupFix~31bf3856ad364e35~amd64~~26100.32995.1.21" -NoRestart
Restart-Computer -Force
(then reinstall Claude with a fresh installer → Status: Ok, survives reboot)

Related: #68792 (same 0x80073CF6 "worked days ago", no cause identified), #37443 (Windows Update flipped a working MSIX install, DISM/SFC not durable), #49655 / #48003 / #49917 (CoworkVMService lock cluster — distinct here, since deployment succeeds yet package is NeedsRemediation and stopping Cowork didn't help).

What Should Happen?

A Windows cumulative update should not break MSIX registration for a previously-working app. The installer should also detect the post-install "Modified, NeedsRemediation" / "PackageUserInformation : {}" state and surface it instead of treating deployment 0x0 as success. Please test the MSIX deployment path against Windows Server 2025 at build 26100.32995 (KB5094125).

Error Messages/Logs

AddPackage failed: AddPackage failed with HRESULT 0x80073CF6
Get-AppxPackage *Claude*  →  Status: Modified, NeedsRemediation
PackageUserInformation : {}
AppXDeploymentServer/Operational Event ID 400: Deployment Register operation ... finished successfully (0x0)

Steps to Reproduce

1. Windows Server 2025 with a working Claude Desktop MSIX install (Claude_pzs8sxrjxfjjc)
2. Install the June 9, 2026 cumulative update KB5094125 (OS build 26100.32995) + reboot
3. Launch Claude Desktop → "go to advanced options ... select Repair ... reinstall ... contact administrator"
4. Uninstall and reinstall with a fresh installer → install reports success but the package is immediately Modified, NeedsRemediation, or AddPackage fails with 0x80073CF6

Claude Model

None

Is this a regression?

Yes, this worked in a previous version

Last Working Version

Worked for months until KB5094125 (2026-06-19)

Claude Code Version

N/A — this is a Claude Desktop (MSIX) issue, not Claude Code CLI. claude --version is not applicable (Claude Code is not installed). Affected package: Claude_pzs8sxrjxfjjc (Claude Desktop), build/version unknown because install/registration fails before the app launches reliably.

Platform

Anthropic API

Operating System

Windows

Terminal/Shell

PowerShell

Additional Information

Server 2025 Release Health does not list a known MSIX-registration issue for KB5094125. The fix here is removing the LCU (Remove-WindowsPackage) + reboot + fresh install; Windows Update was then paused to stop the KB returning. Caveat: removing the LCU reliably restores registration, but this may be an interaction between the new June servicing baseline and the MSIX deployment of a package that declares a packaged Windows service (CoworkVMService), rather than a bug in the KB alone.