[BUG] Cowork tab hidden on Windows 11 after update to 1.17377.2.0 - flashes on Ctrl+R then disappears

## Environment

• App: Claude Desktop 1.17377.2.0 (MSIX / Microsoft Store install)
• OS: Windows 11 Pro, build 10.0.26200, x64
• Plan: Max
• Previously working: Yes — Cowork worked on version 1.15962.1.0

Summary

After the app auto-updated (1.15962.1.0 → 1.17377.1.0 on 2026-07-01, → 1.17377.2.0 on 2026-07-02), the Cowork tab disappeared entirely. Only Chat/Code remain. Pressing Ctrl+R makes the Cowork tab appear for a split second, then it hides — so the UI still contains it, but something evaluates to "hide" right after load.

Diagnostics already performed

1. CoworkVMService is installed, StartType=Automatic, Status=Running; cowork-svc.exe (signed Anthropic, PBC) runs normally. No AV/quarantine interference (verified via AppControl — zero block events).
2. Initially, cowork_vm_node.log showed:

``
[cleanupVMBundleIfUnsupported] yukonSilver not supported (status=unsupported), checking for stale bundle...
[startVM] VM not supported (win32/x64), skipping
``
Root cause of that part: all Windows virtualization features were disabled.

1. Enabled VirtualMachinePlatform + rebooted. The unsupported error is now gone; log now shows the platform check passing and only the bundle missing:

``
[Bundle:status] rootfs.vhdx missing
[Bundle:status] vmlinuz missing
[Bundle:status] initrd missing
``
No VM bundle download is ever attempted, and the tab is still hidden.

1. Tried: full quit/relaunch, sign out/in, Ctrl+R reloads — no change. main.log shows GrowthBook loading 200 features consistently ("0 changed") and "refreshing for account change" events after the update.
2. The renderer cache (claude.ai IndexedDB) contains a server-side flag whose name starts with hideCoworkD… — suggesting the tab is being hidden by a server-side gate rather than a client error.

Expected

Either the Cowork tab shows (machine now meets all requirements in the yukonSilver support check: win32/x64, MSIX, build ≥ 19041, HCS available), or the app shows why it's unavailable instead of silently hiding the tab.

Ask

• Is Windows Cowork currently gated server-side (rollout/flag)? If so, please surface an "unavailable because…" message instead of hiding the tab with no explanation.
• If not gated, the hide logic appears to mis-evaluate on this configuration — logs available on request (main.log, cowork_vm_node.log).

Related issues

• #25136 (same yukonSilver unsupported log line, Win11 Pro)
• #50895, #50764, #51208 (Cowork tab missing on Windows)