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Cowork VM marked unsupported on Windows 11 25H2 Build 26200 (stable release) #29322

Closed as not planned
Closed as not planned
Cowork VM marked unsupported on Windows 11 25H2 Build 26200 (stable release)#29322
Labels
area:coworkbugSomething isn't workingplatform:windowsIssue specifically occurs on WindowsstaleIssue is inactive

Description

@pytheorem
pytheorem
opened on Feb 27, 2026

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

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.

Activity

  1. github-actions
    added
    bugSomething isn't working
    area:cowork
    platform:windowsIssue specifically occurs on Windows
    on Feb 27, 2026

  2. github-actions commented on Feb 27, 2026

    @github-actions
    github-actionsbot
    on Feb 27, 2026 – with GitHub Actions

    Found 3 possible duplicate issues:

    1. [BUG] Cowork tab shows "requires a newer installation" on Windows 11 Build 26200 — yukonSilver marked unsupported #28238
    2. [BUG] Windows 11 28020.1611.br - with hyperV installed - cowork not appaer #26589
    3. [BUG] #27248

    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. pytheorem commented on Feb 27, 2026

    @pytheorem
    pytheorem
    on Feb 27, 2026
    Author

    This is not a duplicate. The linked issues are all the same underlying problem — yukonSilver is marked unsupported via what appears to be a server-side feature flag — but none of them have received any response from Anthropic staff.

    This report specifically clarifies that Build 26200 is the stable GA release of Windows 11 25H2 (generally available since September 2025), not a preview/insider build. The machine is not enrolled in Windows Insider, yet the VM is never provisioned.

    The yukonSilver detection issue remains unresolved across multiple Claude Desktop versions (v1.1.3918 through v1.1.4498) and affects Windows 10 Pro, Windows 11 Home, and Windows 11 Pro users alike. Could an Anthropic engineer please triage this?

  4. rodrigodagama commented on Mar 4, 2026

    @rodrigodagama
    rodrigodagama
    on Mar 4, 2026

    Same issue here.

    Environment:

    • Claude Desktop: v1.1.4498 (24f768)
    • OS: Windows 11 Pro 25H2 (Build 26200.7922)
    • Hyper-V: enabled

    Symptoms:

    • Cowork tab does not appear in the UI
    • sc query CoworkVMService returns empty (service not installed)
    • Clean reinstall did not help

    Build 26200.7922 is the current stable GA release of Windows 11 25H2. Please fix the platform detection so yukonSilver is recognized as supported on this build.

  5. GodThew commented on Mar 4, 2026

    @GodThew
    GodThew
    on Mar 4, 2026

    Same issue here.

    Environment:

    • Claude Desktop: 1.1.4498 (24f768)
    • OS: Windows 11 Enterprise x64 (Build 26100)
    • Hyper-V: Active ("A hypervisor has been detected")
    • vmcompute service: Running
    • CoworkVMService: Running
    • Network: api.anthropic.com reachable on port 443
    • VM bundle: Empty (never downloaded)

    Logs (cowork_vm_node.log):

    [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

    UI behavior:

    • Cowork tab is visible but shows "Cowork requires a newer installation"
    • Reinstall button does nothing
    • Reinstalled Claude Desktop multiple times — no change

    All infrastructure is ready but the app refuses to provision the VM. This is on a corporate-managed machine (no local admin rights), so the MSIX elevation detection issue (#25325) likely applies here as well.`

  6. github-actions
    added
    staleIssue is inactive
    on Mar 18, 2026

  7. hamzsait commented on Mar 27, 2026

    @hamzsait
    hamzsait
    on Mar 27, 2026

    Environment:

    • Claude Desktop: v1.1.9134
    • OS: Windows 11 Home x64 (Build 26200.8037)
    • Hyper-V: Not available — Home edition does not include Hyper-V
    • WSL: Installed WSL 2.6.3 + VirtualMachinePlatform, virtualization enabled in BIOS

    Symptoms:

    • Dispatch chat window opens but messages load indefinitely, never receiving a response
    • cowork_vm_node.log repeatedly shows yukonSilver not supported (status=unsupported) and [startVM] VM not supported (win32/x64), skipping

    Notes:

    • Issue persists after clean reinstall of Claude Desktop
    • Dispatch connects (QR code scan works, phone links successfully) but the VM never initializes so messages hang
    • Windows 11 Home does not support Hyper-V — unclear if this is a hard requirement or if an alternative path (e.g. WSL2 only) could be supported
  8. github-actions
    removed
    staleIssue is inactive
    on Mar 27, 2026

  9. shokomon commented on Apr 1, 2026

    @shokomon
    shokomon
    on Apr 1, 2026

    Additional case: Intel i7-7800X, Windows 11 Pro, Claude Desktop 1.2.234

    Adding another affected system to help broaden the hardware data for Anthropic.

    Environment:

    • OS: Windows 11 Pro (fully updated)
    • CPU: Intel Core i7-7800X @ 3.50GHz (x64)
    • Claude Desktop: v1.2.234 (2d1855), fresh MSIX install with administrator privileges
    • Subscription: Pro plan
    • Install type: ClaudeSetup.exe from claude.com/download, run as administrator

    Virtualization status (all confirmed enabled):

    • VirtualMachinePlatform: EnabledAdditional case: Intel i7-7800X, Windows 11 Pro, Claude Desktop 1.2.234
      Adding another affected system to help broaden the hardware data for Anthropic.

    Environment:

    • OS: Windows 11 Pro (fully updated)
      • CPU: Intel Core i7-7800X @ 3.50GHz (x64)
        • Claude Desktop: v1.2.234 (2d1855), fresh MSIX install with administrator privileges
          • Subscription: Pro plan
            • Install type: ClaudeSetup.exe from claude.com/download, run as administrator
              Virtualization status (all confirmed enabled):
    • VirtualMachinePlatform: Enabled
      • HypervisorPlatform: Enabled
        • HyperVisorPresent: True (confirmed via Get-ComputerInfo)
          • bcdedit hypervisorlaunchtype: auto
            Symptoms:
    • Cowork tab visible but greyed out with "requires newer installation" tooltip
      • Brief "Validation failed!" flash visible on app startup before disappearing
        • Regular Chat works perfectly
          • cowork_vm_node.log shows repeated yukonSilver not supported (status=unsupported) entries
            Issue persists across multiple app versions up to and including 1.2.234. This system's Hyper-V configuration is correct — the platform detection is rejecting a fully capable machine.
    • HypervisorPlatform: Enabled
    • HyperVisorPresent: True (confirmed via Get-ComputerInfo)
    • bcdedit hypervisorlaunchtype: auto

    Symptoms:

    • Cowork tab visible but greyed out with "requires newer installation" tooltip
    • Brief "Validation failed!" flash visible on app startup before disappearing
    • Regular Chat works perfectly
    • cowork_vm_node.log shows repeated yukonSilver not supported (status=unsupported) entries

    Issue persists across multiple app versions up to and including 1.2.234. This system's Hyper-V configuration is correct — the platform detection is rejecting a fully capable machine.

  10. github-actions
    added
    staleIssue is inactive
    on Apr 25, 2026

  11. github-actions commented on May 9, 2026

    @github-actions
    github-actionsbot
    on May 9, 2026 – with GitHub Actions

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

  12. github-actions
    closed this as not plannedon May 9, 2026

  13. github-actions commented on Jun 29, 2026

    @github-actions
    github-actionsbot
    on Jun 29, 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.

  14. github-actions
    locked as resolved and limited conversation to collaborators on Jun 29, 2026
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