Cursor services network issues since 3.9

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7

Thanks for coming back with the nslookup results and checking the DNS change. These details really change the picture. Since api2.cursor.sh resolves through your DNS, the hosts open in your browser, and rolling back to 3.8 consistently fixes everything, this isn’t a DNS issue on your side. You’re right about 3.9.

This is something else. In 3.9.x, Cursor’s AI traffic moved to a new transport that no longer goes through the system proxy. Your browser uses the system or automatic proxy (like PAC/WPAD), so it works, but Cursor starting in 3.9 goes direct and gets blocked by the corporate network.

In 3.11.13 we fixed part of this. It now honors http.proxy in settings.json and the HTTP_PROXY and HTTPS_PROXY environment variables. But automatic or system proxy is still being ignored, and that’s likely what’s affecting you.

What to try is setting the proxy explicitly instead of relying on the system one:

  1. Find your corporate proxy address (URL and port). If you use auto config (PAC/WPAD), you’ll need the specific proxy host it points to.
  2. Add this to settings.json:
    "http.proxy": "http://YOUR_PROXY:PORT",
"http.proxySupport": "override",
"cursor.general.disableHttp2": true
    Or launch Cursor with HTTP_PROXY and HTTPS_PROXY set to the same address.
  3. Enable HTTP/1.1: Settings > Network > HTTP Compatibility Mode > HTTP/1.1.
  4. Fully quit Cursor (not Reload Window, actually exit the process) and start it again, then run Run Diagnostics.

Can you confirm if you’re behind a corporate proxy? And is it configured automatically (PAC/WPAD/system settings) or set explicitly? If you can share the proxy address, I can help with the exact config. This will help confirm if this is the known remaining case where system proxy still isn’t honored.