[BUG] Cowork never installed — MSIX stuck Claude_1.6608.2.0_x64__pzs8sxrjxfjjc, all user-side fixes exhausted (relates to #25162, #49917)

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?

Cowork has never successfully installed since day one of purchasing Claude Pro. This is not a new regression — it has never worked on this machine. The installer silently fails every time, leaving the old MSIX package stuck and unremovable.

What Should Happen?

Cowork should install successfully and appear as a tab in Claude Desktop. The new MSIX package should replace the existing stuck version (Claude_1.6608.2.0_x64__pzs8sxrjxfjjc) without error, and the Cowork virtual machine service should initialize correctly on first launch.

Error Messages/Logs

HRESULT 0x80073CF9 — AddPackage failed
HRESULT 0x80073CFA — RemovePackage failed (PreserveApplicationData flag)
"Cowork requires a newer installation"
"Administrator access is required to install Claude with full features"
Log location: C:\Users\MichaelLupino\AppData\Local\Temp\ClaudeSetup.log

Steps to Reproduce

Existing Azure AD-joined Windows 11 machine with Claude Desktop installed prior to the February 2026 MSIX transition. Run ClaudeSetup.exe as Administrator — installer completes silently, Cowork tab never appears, old package remains stuck.

Claude Model

None

Is this a regression?

No, this never worked

Last Working Version

_No response_

Claude Code Version

Claude_1.6608.2.0_x64__pzs8sxrjxfjjc (stuck package version)

Platform

Anthropic API

Operating System

Windows

Terminal/Shell

PowerShell

Additional Information

Support ticket #215474263904702 on file. References related issues #25162 and #49917.
Email: CEO@Summitenterprisesri.com