[BUG] Cowork tab shows "requires modern installer" on Windows 11 Build 26200 (25H2) despite correct virtualization setup

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?

Aquí tienes el reporte listo para pegar (cópialo tal cual en el formulario que se abra después de elegir "Bug Report"):

Título:

Cowork tab shows "requires modern installer" on Windows 11 Build 26200 (25H2) despite correct virtualization setup

Descripción / What's Wrong:

Claude Desktop shows "Cowork requires that Claude Desktop be installed with our modern installer" and the message persists no matter what is tried.

Environment:

• Windows 11 Pro, version 25H2, build 26200.8894
• CPU: AMD Ryzen 9 7900
• Hardware virtualization (SVM/AMD-V): enabled in BIOS
• Virtual Machine Platform (Windows feature): Enabled
• Windows Hypervisor Platform (Windows feature): Enabled
• Services hns and vmcompute: both Running

Steps already taken (in order):

1. Confirmed Claude was previously installed per-user only (PackageUserInformation showed a single user, not AllUsers)
2. Fully removed Claude via Get-AppxPackage -AllUsers Claude | Remove-AppxPackage -AllUsers
3. Downloaded the official MSIX from https://claude.ai/api/desktop/win32/x64/msix/latest/redirect
4. Reinstalled machine-wide via Add-AppxProvisionedPackage -Online -PackagePath "Claude.msix" -SkipLicense -Regions "all" (completed successfully, no errors)
5. Enabled VirtualMachinePlatform via PowerShell, restarted
6. Enabled HypervisorPlatform via PowerShell, restarted
7. Verified both features show State: Enabled after restart
8. Verified hns and vmcompute services are Running
9. Signed out and back into Claude Desktop

Expected behavior:
Cowork tab should become available given that Hyper-V, Virtual Machine Platform, and Windows Hypervisor Platform are all enabled and running, and Claude is installed at machine level.

Actual behavior:
The "Cowork requires modern installer" message persists regardless of the steps above.

This appears related to closed issue #28238 (yukonSilver marked unsupported on Build 26200), suggesting the VM compatibility check may still be misclassifying this Windows build as unsupported even when all requirements are met.

What Should Happen?

The Cowork tab should become available and functional, since Hyper-V, Virtual Machine Platform, and Windows Hypervisor Platform are all enabled and running, hardware virtualization (AMD SVM) is enabled in BIOS, and Claude Desktop is installed machine-wide via Add-AppxProvisionedPackage.

Error Messages/Logs

Steps to Reproduce

1. Install Claude Desktop for Windows using the official installer or MSIX package
2. Sign in and attempt to open the Cowork tab
3. Observe the message: "Cowork requires that Claude Desktop be installed with our modern installer"
4. Fully uninstall Claude: Get-AppxPackage -AllUsers Claude | Remove-AppxPackage -AllUsers
5. Download the official MSIX from https://claude.ai/api/desktop/win32/x64/msix/latest/redirect
6. Reinstall machine-wide: Add-AppxProvisionedPackage -Online -PackagePath "Claude.msix" -SkipLicense -Regions "all"
7. Enable required Windows features:

Enable-WindowsOptionalFeature -Online -FeatureName VirtualMachinePlatform -All -NoRestart
Enable-WindowsOptionalFeature -Online -FeatureName HypervisorPlatform -All -NoRestart

1. Restart the machine
2. Verify both features show State: Enabled
3. Verify services hns and vmcompute are Running
4. Open Claude Desktop and attempt Cowork again
5. The same "requires modern installer" message still appears

Claude Model

None

Is this a regression?

Yes, this worked in a previous version

Last Working Version

_No response_

Claude Code Version

N/A - using Claude Desktop app version 1.24012.9.0, not the Claude Code CLI

Platform

Anthropic API

Operating System

macOS

Terminal/Shell

Terminal.app (macOS)

Additional Information

_No response_