[BUG] Cowork VM uses DNS from disconnected adapter on Windows, causing API unreachable

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?

Cowork workspace fails to start on Windows because the HNS NAT network/endpoint is assigned DNS from a disconnected USB Ethernet adapter instead of the active Wi-Fi adapter, api.anthropic.com fails through those stale servers.

• OS: Windows 11 Pro
• Claude Desktop: 1.1.2685.0
• Active DNS (Wi-Fi): 75.75.75.75, 75.75.76.76
• Incorrect DNS selected for cowork endpoint (from disconnected Ethernet adapter)

What Should Happen?

Cowork should use DNS from the active network path (Wi-Fi in this case), resolve api.anthropic.com, and complete workspace startup successfully.

Error Messages/Logs

1. Failed to start Claude's workspace - VM service not running. The service failed to start.
  2. Failed to start Claude's workspace - Can't reach the Claude API from Claude's workspace.

  [VM:start] Startup complete
  [VM] API reachability: PROBABLY_UNREACHABLE
  [VM] API reachability: UNREACHABLE
  [VM:network] API is unreachable

Steps to Reproduce

1. Windows machine has Wi-Fi active and a disconnected Ethernet/USB adapter with stale DNS configured.
2. Observe workspace fails with API unreachable.
3. Inspect HNS endpoint/network DNS for cowork-vm-* and see DNS inherited from disconnected adapter.

Claude Model

Other

Is this a regression?

I don't know

Last Working Version

_No response_

Claude Code Version

Claude Desktop 1.1.2685.0 (Cowork workspace feature).

Platform

Anthropic API

Operating System

Windows

Terminal/Shell

PowerShell

Additional Information

A host-side workaround succeeded:

• force correct DNS on cowork-vm-nat HNS network (75.75.75.75, 75.75.76.76)
• recreate cowork endpoint
• then Cowork starts successfully

Post-fix validation:

Network DNS: 75.75.75.75, 75.75.76.76
Resolve test: PASS

Request: please fix DNS source selection during cowork HNS network creation so disconnected adapters are ignored.