Cowork VM marked unsupported on Windows 11 25H2 Build 26200 (stable release)

Bug description

Cowork VM (yukonSilver) is marked as unsupported on Windows 11 Pro 25H2 Build 26200.7922, which is the current stable GA release of Windows 11. The Cowork tab never appears and the VM is never provisioned.

Logs

cowork_vm_node.log shows repeated entries:

[cleanupVMBundleIfUnsupported] yukonSilver not supported (status=unsupported), checking for stale bundle...
[startVM] VM not supported (win32/x64), skipping
[Callbacks] Swift VM addon not available for callbacks

No vEthernet (cowork-vm-nat) adapter is created, no WinNAT rules exist, and no vm_bundles directory is provisioned.

Environment

• OS: Windows 11 Pro 25H2 (Build 26200.7922) — stable GA release
• Architecture: x64
• Claude Desktop version: 1.1.4498
• Hyper-V: Active (confirmed via systeminfo: "A hypervisor has been detected")
• CoworkVMService: Running

Expected behaviour

Build 26200 is the RTM build for Windows 11 25H2, generally available since September 2025. The platform detection should recognise it as a supported build and provision the Cowork VM.

Related issues

• #25136 — identified Build 26200 as problematic, closed after a different user's fix worked (different root cause)
• #27330 — win32/x64 rejection fixed in v1.1.3963, but does not resolve this build detection issue
• #25692 — Cowork tab not appearing on Windows

Notes

The system may have been enrolled in the Windows Insider Release Preview channel at some point, but Build 26200 is the same build shipping on the stable channel for 25H2. The Insider registry keys (HKLM\SOFTWARE\Microsoft\WindowsSelfHost\Applicability) exist but BranchName and Ring are empty.