[BUG] Cowork VM fails to create on Windows — HCS HRESULT 0x800707de (ERROR_DUPLICATE_TAG) at Construct stage

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?

Claude Desktop Cowork fails to start the workspace VM on Windows 11 (Build 26200.7840). The error occurs at the HCS (Host Compute Service) Construct stage with HRESULT 0x800707de (ERROR_DUPLICATE_TAG).

The VM never gets created — no virtual network (cowork-vm-nat) is established, and hcsdiag list shows no residual compute systems.

Error from cowork_vm_node.log:

[ERROR] Failed to create the VM: Creating a compute system failed: HRESULT: 0x800707de - Detail: Construct

This is NOT the commonly reported "API unreachable" or network connectivity issue. The failure happens at a much lower level — the VM itself cannot be constructed.

What Should Happen?

Cowork should successfully create the lightweight VM via HCS and boot the workspace environment, allowing the user to interact with the Cowork tab normally.

Error Messages/Logs

From cowork_vm_node.log (%APPDATA%\Claude\logs\):

[cowork_vm_node] Setting up VM...
[cowork_vm_node] VM config complete. Creating compute system...
[cowork_vm_node] [ERROR] Failed to create the VM: Creating a compute system failed: HRESULT: 0x800707de - Detail: Construct
[cowork_vm_node] VM creation failed. No virtual network was established.

Win32 error 0x800707de maps to ERROR_DUPLICATE_TAG.

Steps to Reproduce

1. Open Claude Desktop v1.1.5368.0 on Windows 11 Build 26200.7840
2. Navigate to the Cowork tab
3. Cowork attempts to start the workspace VM
4. VM creation fails immediately at the HCS Construct stage with error 0x800707de
5. Error message "Failed to start Claude's workspace" is displayed

Troubleshooting already attempted (all unsuccessful):

• Restarted Claude Desktop and the computer multiple times
• Verified WSL2 is installed and working (v2.6.3.0)
• Confirmed vmcompute and vmms services are running
• Confirmed HypervisorPresent = True
• Verified VM bundle files exist and are intact in %APPDATA%\Claude\vm_bundles\claudevm.bundle\
• hcsdiag list shows no residual compute systems
• Deleted vm_bundles folder, stopped/restarted vmcompute and vmms services, let Cowork re-download — same error
• Checked HNS networks: only WSL and Default Switch present, no cowork-vm-nat (VM fails before network creation)
• Used "reinstall the workspace" option — same result

Claude Model

Opus

Is this a regression?

No, this never worked

Last Working Version

_No response_

Claude Code Version

Claude Desktop v1.1.5368.0 (Cowork feature — not Claude Code CLI)

Platform

Anthropic API

Operating System

Windows

Terminal/Shell

PowerShell

Additional Information

Environment Details

| Component | Value |
|---|---|
| Windows Version | Windows 11 Build 26200.7840 |
| Claude Desktop | v1.1.5368.0 |
| WSL Version | 2.6.3.0 |
| Kernel Version | 6.6.87.2-1 |
| vmcompute service | Running (Manual) |
| vmms service | Running (Automatic) |
| HypervisorPresent | True |
| hcsdiag list | Empty (no residual VMs) |

VM Bundle Contents (intact)

rootfs.vhdx       — 9,453,961,216 bytes
sessiondata.vhdx  — 675,282,944 bytes
smol-bin.vhdx     — 37,748,736 bytes
initrd            — 175,549,736 bytes
vmlinuz           — 14,965,128 bytes

HNS Network State

Only WSL (Hyper-V firewall) and Default Switch networks present. No cowork-vm-nat network — confirming the VM fails before the networking stage.

Related Issues

• #24918 — Similar Cowork Windows issues, but those are mostly network-related ("API unreachable") after VM boots. This issue is different: the VM itself cannot be constructed.
• #27801 — Broader Cowork Windows bug reports

Notes

• Debug logs have been shared via the "share your debug logs" button in the Cowork error screen.
• This appears to be a compatibility issue between Cowork's HCS VM creation logic and Windows Build 26200.