Where does the bug appear (feature/product)?
Cursor IDE
Describe the Bug
Cursor IDE Agent consistently fails with “[internal] internal error” on Cursor 3.20.21 (Windows 11).
The error occurs even when sending very simple messages such as “hello” or “test”.
The issue persists across different models, including Claude and Grok.
Steps to Reproduce
- Open Cursor 3.20.21 on Windows 11.
- Open any project.
- Open the Agent panel.
- Select an Agent model such as Claude or Grok.
- Send a simple message such as “hello” or “test”.
- The request fails with “[internal] internal error”.
- The same issue occurs after changing HTTP compatibility modes, reinstalling Cursor, and switching from Wi-Fi to a phone hotspot.
Expected Behavior
The Agent should process the request and return a response normally.
Network Diagnostics shows that the Agent and Agent Endpoint tests pass, so the actual IDE Agent request should also work.
Operating System
Windows 10/11
Version Information
IDE: Cursor
Version: 3.20.21 (User Setup)
OS: Windows 11
For AI issues: which model did you use?
Claude and Grok
For AI issues: add Request ID with privacy disabled
Request ID: 2ba42389-6e57-4547-a3e3-130ce8d7632e
Additional Information
The issue persists after reinstalling Cursor and after testing both Wi-Fi and a phone hotspot.
I also tested HTTP/2, HTTP/1.1 and HTTP/1.0.
With HTTP/1.0, Network Diagnostics shows Agent: PASS and Agent Endpoint: PASS, while Ping fails with 1061 ms. Despite the Agent diagnostics passing, the actual IDE Agent still returns “[internal] internal error”.
Other Network Diagnostics checks are also passing.
This issue makes the Agent unusable for me.
Does this stop you from using Cursor
Yes - Cursor is unusable