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[BUG] #27248

Closed as not planned
Closed as not planned
[BUG]#27248
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bugSomething isn't workingstaleIssue is inactive

Description

@ltr-star
ltr-star
opened on Feb 20, 2026

Preflight Checklist

  • I have searched existing issues and this hasn't been reported yet
  • This is a single bug report (please file separate reports for different bugs)
  • 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:

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

Activity

  1. ltr-star
    added
    bugSomething isn't working
    on Feb 20, 2026

  2. github-actions commented on Feb 20, 2026

    @github-actions
    github-actionsbot
    on Feb 20, 2026 – with GitHub Actions

    Found 3 possible duplicate issues:

    1. [BUG] Windows 11 28020.1611.br - with hyperV installed - cowork not appaer #26589
    2. [BUG] Cowork doesn't load into Claude app OS Build 26200.7840 #27188
    3. [BUG] Cowork for windows: yukonSilver not supported #25034

    This issue will be automatically closed as a duplicate in 3 days.

    • If your issue is a duplicate, please close it and 👍 the existing issue instead
    • To prevent auto-closure, add a comment or 👎 this comment

    🤖 Generated with Claude Code

  3. ltr-star commented on Feb 21, 2026

    @ltr-star
    ltr-star
    on Feb 21, 2026
    Author

    Still broken on v1.1.3918

  4. saurabhagrawal86 commented on Feb 22, 2026

    @saurabhagrawal86
    saurabhagrawal86
    on Feb 22, 2026

    Hi @claude team,

    This issue is still reproducible on Claude Desktop for Windows and has not been resolved.

    Environment

    • Product: Claude Desktop (Windows OS)
    • Version: 1.1.3963 (71a7ae)
    • Build Timestamp: 2026-02-21T16:19:56.000Z
    • Subscription: Pro / Teams (paid)

    Problem

    The Cowork feature remains unusable on Windows. Based on the logs, it appears the VM layer is failing to initialize correctly.

    Relevant Log Entries (from cowork_vm_node.log)

    2026-02-08 21:41:43 [info] [cleanupVMBundleIfUnsupported] yukonSilver not supported (status=unsupported), checking for stale bundle...

    2026-02-18 15:25:39 [error] [Callbacks] Swift VM addon not available for callbacks

    Observations

    • yukonSilver not supported suggests the VM bundle is either incorrectly packaged or not supported on Windows.
    • Swift VM addon not available for callbacks strongly indicates that the required VM addon is missing or failing to load.
    • This effectively makes Cowork non-functional on Windows.

    Impact

    This is a paid feature under Pro/Teams, and it is currently unusable on Windows. That’s a significant blocker for teams relying on Cowork workflows.

    Request

    Please:

    1. Confirm whether Cowork is officially supported on Windows in the current Desktop build.
    2. Clarify whether yukonSilver and the Swift VM addon are expected to work on Windows.
    3. Prioritize this as an urgent bug if Windows support is intended.
    4. Provide an ETA or workaround if available.

    I’ve attached the full cowork_vm_node.log for further diagnosis. cowork_vm_node.log

    This needs urgent attention, as it directly impacts paying customers.

    Thanks.

    Saurabh Agrawal

  5. jdub3420 commented on Feb 25, 2026

    @jdub3420
    jdub3420
    on Feb 25, 2026

    Cowork blocked by yukonSilver not supported on Windows 11 Home — reinstall prompt is misleading
    Environment:

    Windows 11 Home, Version 25H2 (OS Build 26200.7840)
    Claude Desktop (latest version, installed Feb 9, 2026)
    Paid subscription

    Problem:
    Cowork has never worked on this machine. The app repeatedly shows a "Cowork requires a newer installation — Reinstall" prompt, but reinstalling does nothing. The cowork_vm_node.log shows yukonSilver not supported (status=unsupported) since day one (Feb 9), with hundreds of VM not supported (win32/x64), skipping entries across 16+ days.
    No vm_bundles directory was ever created — the VM bundle was never downloaded.
    Key issue:
    The "Reinstall" prompt is actively misleading. The blocker is a server-side feature flag, not anything the user can fix locally. If Windows 11 Home isn't supported, the app should say that clearly instead of suggesting a reinstall loop.
    Request:

    Clarify whether Windows 11 Home is officially supported for Cowork
    If it's not supported, show an honest error message instead of "Reinstall"
    If it is supported, please flip the yukonSilver flag for this machine

    Log excerpt:
    2026-02-09 17:24:59 [info] [cleanupVMBundleIfUnsupported] yukonSilver not supported (status=unsupported), checking for stale bundle...
    2026-02-14 20:40:12 [warn] [startVM] VM not supported (win32/x64), skipping
    2026-02-25 15:01:14 [warn] [startVM] VM not supported (win32/x64), skipping

  6. pfaisant commented on Feb 26, 2026

    @pfaisant
    pfaisant
    on Feb 26, 2026

    still getting same issue

  7. github-actions
    added
    staleIssue is inactive
    on Mar 12, 2026

  8. github-actions commented on Mar 26, 2026

    @github-actions
    github-actionsbot
    on Mar 26, 2026 – with GitHub Actions

    Closing for now — inactive for too long. Please open a new issue if this is still relevant.

  9. github-actions
    closed this as not plannedon Mar 26, 2026

  10. github-actions commented on Apr 3, 2026

    @github-actions
    github-actionsbot
    on Apr 3, 2026 – with GitHub Actions

    This issue has been automatically locked since it was closed and has not had any activity for 7 days. If you're experiencing a similar issue, please file a new issue and reference this one if it's relevant.

  11. github-actions
    locked as resolved and limited conversation to collaborators on Apr 3, 2026
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