Network Diagnostics: Agent fails with "HTTP/1.1 SSE responses are being buffered by a proxy", Ping also slow (3.6s)

Support Help
1

Summary
Agent mode doesn’t work properly for me. Network Diagnostics shows Ping :cross_mark:, Chat :white_check_mark:, Agent :cross_mark:. The Agent test reports:
HTTP/1.1 SSE responses are being buffered by a proxy in your network environment

Environment

  • Cursor version: latest

Diagnostics results (full screenshot attached)

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image797×1294 163 KB

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image672×761 53.8 KB

Test Result Details
Ping :cross_mark: “Response took 3653ms”. The 5 pings took 1162 / 1221 / 3556 / 5012 / 3653 ms
Chat :white_check_mark: Passed. But the last 3 chunks arrived at once (5049ms, then 0ms, 0ms), which looks like batching
Agent :cross_mark: Chunks arrived 2.4–7.4s apart (3110 / 6167 / 7356 / 3485 / 2425 ms), then it failed with the proxy-buffering error

What I’ve tried

  • Disabled HTTP/2 / enabled HTTP/1.1 compatibility mode in settings
  • Turned the VPN/proxy off, or switched network
  • Restarted Cursor / reinstalled
  • Result: no change
5

Hey @batman2333, thanks for the report and the screenshots.

The “buffered by a proxy” wording in Network Diagnostics is misleading here. That check fails whenever the first streaming response takes longer than 2 seconds, and your Ping results (1 to 12 seconds per round trip) show the connection itself is very slow. That’s also why your second run flipped, with Agent passing and Chat failing. So the real problem is latency on the route your traffic takes, not buffering.

Your screenshot also shows Cursor’s traffic still goes through a local proxy, even with the VPN switched off:

  • The SSL row shows IP: 127.0.0.1, so the connection goes to a proxy app on your Mac instead of straight to our servers.
  • The DNS row resolves api2.cursor.sh to 29.240.0.5, which isn’t one of our addresses. That usually means a proxy tool in TUN / “enhanced” / fake-IP mode is still handling DNS.

Could you try these steps and reply with a new diagnostics screenshot?

  1. Open System Settings → Network → your active connection (Wi-Fi or Ethernet) → Details → Proxies, and check whether any proxy points to 127.0.0.1.
  2. In your proxy app, check whether TUN mode (sometimes called “enhanced mode” or “virtual network interface”) is turned on.
  3. If you need the proxy to reach Cursor, switch to a different node that is closer or faster.
  4. Fully quit Cursor (Cmd+Q) and open it again.
  5. Go to Cursor Settings → Network and click Run Diagnostic.
  6. Look at the Ping row. Each ping should come back well under 1 second. If it’s still 1 to 5 seconds, the proxy node is the bottleneck.

Keep HTTP Compatibility Mode on HTTP/1.1 while you’re on this route. If you ever see “Failed to establish a socket connection to proxies: SOCKS 127.0.0.1:…”, your Mac is still pointing at the proxy app while it isn’t running. Start the app again or clear that proxy setting.

Also, when Agent “doesn’t work properly”, what exactly happens? Does it stop with an error, hang on “Taking longer than expected”, or answer very slowly? If there’s an error, please paste the message and the Request ID (chat ⋯ menu → Copy Request ID), and tell me which proxy app you use and which mode it’s in.