[BUG]

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?

Environment

| Field | Value |
|-------|-------|
| Claude Desktop Version | 1.1.3830 (d2af56), 2026-02-20T15:45:56.000Z |
| OS | Windows 11 Pro x64 |
| Subscription | Pro |
| Hyper-V | Enabled |
| Virtual Machine Platform | Enabled |
| Windows Hypervisor Platform | Enabled |
| vmcompute | Running |
| vmms | Running |
| WSL2 | Not installed |
| Docker | Not installed |
| NetNat | Empty (no NAT conflicts) |

What's Wrong

The Cowork tab does not appear in the main UI (next to "Chat"), even though:

• Cowork settings are visible in Settings → Cowork
• All Hyper-V / virtualization features are enabled
• vmcompute and vmms services are both running
• App is on the latest version (v1.1.3830)
• No WSL2, no Docker, no NAT conflicts — ruled out per #26450
• %APPDATA%\Claude\vm_bundles\ directory does not exist (VM bundle was never downloaded)

Critical observation: Cowork works perfectly on a different Windows 11 PC with the same Pro account. This proves:

1. It's not an account-level issue
2. It's not a subscription issue
3. It's a machine-specific feature flag assignment via GrowthBook

What I've Tried (nothing resolved the issue)

• Verified all Hyper-V features are enabled
• Confirmed vmcompute and vmms services are running
• Logged out and back in
• Full app reinstall (uninstall, delete %APPDATA%\Claude and %LOCALAPPDATA%\Claude, reboot, fresh install)
• Updated through v1.1.3189 → v1.1.3541 → v1.1.3770 → v1.1.3830 — no change across 4 versions
• Confirmed no WSL2/Docker/NAT conflicts

What Should Happen?

Expected Behavior

Cowork tab should appear next to "Chat" in the mode selector, and the VM should boot successfully on win32/x64 with Hyper-V enabled.

Error Messages/Logs

### Log Output

`%APPDATA%\Claude\logs\cowork_vm_node.log` shows:


2026-02-17 11:58:40 [info] [cleanupVMBundleIfUnsupported] yukonSilver not supported (status=unsupported), checking for stale bundle...
2026-02-17 11:58:43 [warn] [startVM] VM not supported (win32/x64), skipping
2026-02-17 11:58:43 [info] [Callbacks] Initializing VM event callbacks...
2026-02-17 11:58:43 [info] [VM] Loading vmClient (TypeScript) module...
2026-02-17 11:58:43 [info] [VM] Module loaded successfully
2026-02-17 11:58:43 [info] [Callbacks] VM event callbacks initialized
2026-02-17 11:59:00 [warn] [startVM] VM not supported (win32/x64), skipping
2026-02-17 11:59:02 [warn] [startVM] VM not supported (win32/x64), skipping


The VM module loads successfully, but the platform check (`win32/x64`) causes it to skip startup every time. `yukonSilver` is marked as `status=unsupported`, preventing the VM bundle download and hiding the Cowork tab.

### Hyper-V Services


PS> Get-Service vmcompute, vmms | Format-Table Name, Status

Name       Status
----       ------
vmcompute  Running
vmms       Running

PS> Get-WindowsOptionalFeature -Online -FeatureName Microsoft-Hyper-V | Select State

State
-----
Enabled

PS> wsl --status
# "Der Windows-Subsystem für Linux ist nicht installiert."

PS> Get-Service com.docker* 2>$null
# (empty — Docker not installed)

PS> Get-NetNat
# (empty — no NAT conflicts)

Steps to Reproduce

Steps to Reproduce

1. Install Claude Desktop v1.1.3830 on Windows 11 Pro x64
2. Ensure Hyper-V, Virtual Machine Platform, and Windows Hypervisor Platform are enabled
3. Log in with a Pro subscription
4. Observe: only "Chat" tab is visible — no "Cowork" tab
5. Check %APPDATA%\Claude\logs\cowork_vm_node.log — shows yukonSilver not supported (status=unsupported)

Claude Model

None

Is this a regression?

No, this never worked

Last Working Version

_No response_

Claude Code Version

1.1.3830

Platform

Anthropic API

Operating System

Windows

Terminal/Shell

PowerShell

Additional Information

Root Cause Analysis

The yukonSilver feature flag is controlled server-side via GrowthBook and is set to unsupported for this specific machine, despite meeting all hardware and software requirements. The same account on a different Windows 11 PC receives supported status and Cowork works fine. This is a machine-specific rollout issue, not a platform capability issue.

Notes

• Issues #25136 and #25142 were reportedly resolved, but the fix has not reached this machine across 4 version updates (v1.1.3189 → v1.1.3541 → v1.1.3770 → v1.1.3830).
• Issue #25505 reports that yukonSilver switched from "unsupported" to working after weeks without user action — suggesting the flag is being expanded server-side in waves.
• The Cowork section is visible in Settings, confirming the UI feature flag is active — only the VM/platform detection blocks it.
• Support ticket submitted to Anthropic on 2026-02-19, no response yet.