[BUG] [BUG] Cowork Windows 11 Pro: ECONNRESET - NAT rule creation fails with "duplicate name" error despite no existing NAT rules

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

• OS: Windows 11 Pro
• Claude Desktop version: latest (auto-updated February 18, 2026)
• Hyper-V: enabled
• VPN: not active
• Kaspersky: removed/disabled for testing

Issue
Cowork fails with "Failed to start Claude's workspace / Can't reach the Claude API from Claude's workspace" and API Error: ECONNRESET.

Troubleshooting performed

vEthernet (cowork-vm-nat) interface exists and is UP:

• IP: 172.16.0.1
• Status: Up / 10 Gbps

Get-NetNat returns empty (no NAT rules visible).

Attempting to create NAT manually fails:

New-NetNat -Name "cowork-vm-nat" -InternalIPInterfaceAddressPrefix "172.16.0.0/24"
Error: "You were not connected because a duplicate name exists on the network" (Windows System Error 52)

Remove-NetNat fails: "No MSFT_NetNat objects found"

Get-WmiObject MSFT_NetNat shows no cowork-vm-nat entry (only a test entry cowork-nat-fix with different subnet).

HNS service restart did not resolve the issue.
HNS Policy folder does not exist at C:\ProgramData\Microsoft\Windows\HNS\Policy

Route table shows 172.16.0.0/24 correctly on-link via 172.16.0.1.

Expected behavior
Cowork should be able to connect to the Claude API from its workspace VM.

Actual behavior
VM starts but cannot reach the internet. NAT rule cannot be created or removed via PowerShell. State appears stuck in kernel memory and persists across HNS service restarts.

Note
Chat mode works perfectly. Issue is isolated to Cowork VM network connectivity.

What Should Happen?

Cowork should start its workspace VM and connect successfully to the Claude API, allowing multi-step task execution.

Error Messages/Logs

API Error: Unable to connect to API (ECONNRESET)
"Failed to start Claude's workspace. Can't reach the Claude API from Claude's workspace."

PowerShell diagnostic:
New-NetNat : You were not connected because a duplicate name exists on the network. (Windows System Error 52)
Remove-NetNat : No MSFT_NetNat objects found with property 'Name' equal to 'cowork-vm-nat'.
Get-NetNat returns empty output despite the error above.

Steps to Reproduce

1. Install Claude Desktop on Windows 11 Pro (latest version, auto-updated Feb 18 2026)
2. Open Claude Desktop
3. Switch to Cowork mode
4. Assign a folder
5. Give any task
6. Cowork starts VM but immediately fails with ECONNRESET

Claude Model

None

Is this a regression?

No, this never worked

Last Working Version

_No response_

Claude Code Version

n/a Claude Desktop app

Platform

Anthropic API

Operating System

Windows

Terminal/Shell

PowerShell

Additional Information

• Hyper-V enabled and active
• vEthernet (cowork-vm-nat) interface exists, Status: Up, IP: 172.16.0.1/24
• No VPN active
• Kaspersky removed for testing
• Issue persists after full PC restart
• Issue persists after HNS service restart
• Chat mode works perfectly