[BUG] Cowork - Unable to connect to Claude API on Windows (ECONNRESET / Request timed out)

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?

The Cowork feature fails to connect to the Claude API on Windows. The workspace VM starts successfully, but the API connection always fails.

Errors observed (in order):

• "Failed to start Claude's workspace - Can't reach the Claude API from Claude's workspace"
• API Error: Unable to connect to API (ECONNRESET)
• After adding a firewall rule: Request timed out

Troubleshooting steps already attempted:

• Restarted Claude Desktop and computer
• Clean reinstall (deleted %AppData%\Claude and %LocalAppData%\AnthropicClaude)
• Disabled Windows Defender real-time protection
• No VPN or proxy active
• Added outbound firewall rule for claude.exe
• Confirmed host can reach the API: Test-NetConnection api.anthropic.com -Port 443 → TcpTestSucceeded: True
• CoworkVMService was not present before reinstall, appeared after clean reinstall
• Regular Claude chat works perfectly

Possibly related issues: #18006, #25024, #25308

What Should Happen?

The Cowork workspace should start successfully and connect to the Claude API, allowing task execution — the same way regular Chat mode works without issues.

Error Messages/Logs

The Cowork workspace should start successfully and connect to the Claude API, allowing task execution — the same way regular Chat mode works without issues.

Steps to Reproduce

1. Install Claude Desktop on Windows 11 (latest version)
2. Sign in with a paid subscription
3. Click on the Cowork tab
4. Workspace fails to start with "Can't reach the Claude API from Claude's workspace"

Claude Model

None

Is this a regression?

No, this never worked

Last Working Version

_No response_

Claude Code Version

N/A (Claude Desktop Cowork, not Claude Code CLI)

Platform

Anthropic API

Operating System

Windows

Terminal/Shell

PowerShell

Additional Information

Hyper-V is enabled (Hyper-V Virtual Switch Extension Adapter present).
CoworkVMService was missing before clean reinstall.
Test-NetConnection api.anthropic.com -Port 443 → TcpTestSucceeded: True
Regular Claude chat works perfectly. Only Cowork fails.