A bug with Cowork

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 macOS M1 Pro. The VM boots and mounts all directories successfully, but the internal proxy connection to api.anthropic.com is reset at the TCP level. The host machine can reach the API fine (curl -I returns HTTP/2 404 from Cloudflare), confirming the issue is inside the Cowork VM proxy layer. Error persists after full uninstall/reinstall, clearing all caches, VM bundles, and session files, restarting Mac, and trying different networks. Key log line: [proxy] upstream POST api.anthropic.com failed (connection_reset): read tcp 172.16.10.3:33890->160.79.104.10:443: read: connection reset by peer

<img width="4032" height="3024" alt="Image" src="https://github.com/user-attachments/assets/9c2e9f99-7863-4fdb-8e10-dd90d2110ce4" />

What Should Happen?

Cowork workspace should download the VM bundle successfully, start the workspace, and connect to the Claude API without errors — allowing normal Cowork usage.

Error Messages/Logs

[proxy] upstream POST api.anthropic.com failed (connection_reset): read tcp 172.16.10.3:33890->160.79.104.10:443: read: connection reset by peer


UI error:
“Failed to start Claude’s workspace. Download failed. Check your internet connection and try again. Restarting Claude or your computer sometimes resolves this. If it persists, you can reinstall the workspace.”
Host verification:
	•	dns-sd -G v4 api.anthropic.com → resolves to 160.79.104.10 ✅
	•	curl -I https://api.anthropic.com → HTTP/2 404 via Cloudflare ✅
	•	Connection only fails inside the VM proxy layer​​​​​​​​​​​​​​​​

Steps to Reproduce

1. Install Claude Desktop (latest) on macOS with Apple M1 Pro
2. Open Claude Desktop and switch to the Cowork tab
3. Send any message (e.g. "hi")
4. Cowork shows "Setting up Claude's workspace..." then "Starting Claude's workspace..."
5. After ~15 seconds, error appears: "Failed to start Claude's workspace. Download failed."
6. Clicking "Try again" produces the same result every time

Troubleshooting already attempted (all failed):

• Full uninstall and reinstall of Claude Desktop (multiple times)
• Cleared ~/Library/Application Support/Claude/ (all session data, VM bundles, caches)
• Cleared ~/Library/Caches/ (claude-cli-nodejs, com.anthropic.claudefordesktop.ShipIt, com.anthropic.claudefordesktop)
• Restarted Mac
• Ran sudo purge
• Tried Wi-Fi and phone hotspot
• Verified API reachable from host via curl and dns-sd

Claude Model

None

Is this a regression?

Yes, this worked in a previous version

Last Working Version

_No response_

Claude Code Version

Claude 1.3109.0 (35cbf6)

Platform

Anthropic API

Operating System

macOS

Terminal/Shell

Terminal.app (macOS)

Additional Information

_No response_