Cowork tab hidden despite VM running successfully — yukonSilver marked unsupported due to MSIX can_elevate detection bug #25325

Bug Description

The Cowork tab does not appear in Claude Desktop on Windows 11 Pro despite the Cowork VM successfully booting, connecting to the network, reaching the API, and installing the SDK. The VM works perfectly — but the UI hides the tab because yukonSilver is marked unsupported.

The root cause is that Claude Desktop's MSIX/AppX packaging runs in an AppContainer sandbox that cannot detect elevation, so can_elevate always reports false regardless of the user's actual admin rights. The GrowthBook feature flag evaluation uses this attribute and marks the platform as unsupported, hiding the Cowork tab even though the VM is fully functional.

Evidence from Logs

cowork_vm_node.log — VM starts successfully:

[VM:start] Beginning startup...
rootfs.vhdx.zst checksum validated
vmlinuz.zst checksum validated
initrd.zst checksum validated
All files ready in C:\Users\...\vm_bundles\claudevm.bundle
[VM:steps] download_and_sdk_prepare completed (226852ms)
[VM] Network status: CONNECTED
[VM] API reachability: REACHABLE
[VM:steps] sdk_install completed (7557ms)
[VM:start] Startup complete, total time: 256686ms
[Keepalive] Starting (interval=2000ms)

main.log — Plugin command runs successfully:

[VMCLIRunner] Running: claude plugin list --json --available --cowork
[VMCLIRunner] Command completed with exit code 0

But then cleanup destroys the bundle:

[cleanupVMBundleIfUnsupported] yukonSilver not supported (status=unsupported), checking for stale bundle...
[deleteVMBundle] Deleting reinstall files from C:\Users\...\vm_bundles\claudevm.bundle
[deleteVMBundle] Reinstall files deleted (sessiondata.img preserved)

main.log — Elevation detection always fails (MSIX sandbox):

desktop_windows_elevation_detected | metadata: {
  elevation_type: 'default',
  can_elevate: false
}

This reports can_elevate: false even when launched via "Run as administrator" — MSIX AppContainer sandboxing strips the elevation token.

Environment

• OS: Windows 11 Pro, Build 10.0.26100
• CPU: Intel Core i7-8700 @ 3.20GHz (x64)
• RAM: 80 GB
• Claude Desktop: v1.1.2685 (MSIX), commit f39a622
• CCD Version: 2.1.34
• Domain-joined machine (TTHLAW domain)

Windows Features (all enabled):

• Microsoft-Hyper-V-All ✅
• Microsoft-Hyper-V ✅
• Microsoft-Hyper-V-Hypervisor ✅
• Microsoft-Hyper-V-Services ✅
• Microsoft-Hyper-V-Tools-All ✅
• Microsoft-Hyper-V-Management-PowerShell ✅
• Microsoft-Hyper-V-Management-Clients ✅
• VirtualMachinePlatform ✅
• HypervisorPlatform ✅
• Containers-HNS ✅

CoworkVMService:

• Registered, starts as LocalSystem, AUTO_START
• Binary: C:\Program Files\WindowsApps\Claude_1.1.2685.0_x64__pzs8sxrjxfjjc\app\resources\cowork-svc.exe

The Bug

The yukonSilver platform check is gated on can_elevate, which MSIX apps can never satisfy due to AppContainer sandboxing. This creates a circular failure:

1. MSIX packaging strips elevation detection → can_elevate: false
2. GrowthBook feature flag uses can_elevate → evaluates yukonSilver = unsupported
3. UI checks yukonSilver status → hides Cowork tab
4. Cleanup process deletes VM bundle files (even while VM is running and connected)

The VM itself works perfectly. The tab is hidden by a feature flag that cannot be satisfied on any MSIX installation.

Expected Behavior

The Cowork tab should appear when the VM is successfully running and connected, regardless of can_elevate status. The platform detection should use actual Hyper-V capability checks rather than process elevation detection.

Possibly Related Issues

• [BUG] Cowork tab not showing on Windows 11 Pro x64 — "yukonSilver" marked as unsupported + CoworkVMService cannot be removed #25136 — yukonSilver marked unsupported on Win 11 Pro x64
• [BUG] [Window 11] Claude Cowork does not show up #25142 — Cowork does not show up on Windows 11
• [BUG] Cowork for windows: yukonSilver not supported #25034 — yukonSilver not supported