Consistent "Connection failed"

Bug Reports
1

Where does the bug appear (feature/product)?

Cursor IDE

Describe the Bug

Since approx 12:30pm 30th October UTC up to now (approx 14 hours later), I have consistently been getting the message:

“Connection failed. If the problem persists, please check your internet connection or VPN”.

I had started testing with Composed model about 30 minutes prior to the first instance of the connection error, and thought that might be the issue, so I started a new chat with Auto (which I use 99% of the time), and the issue persists.

I do not have a VPN and there are no issues with my Internet connection or network.

I am able to successfully complete all other network activity on the same PC. I have been using the PC for other business activities for the past 3 hours without any issues other than with Cursor.

I have been unable to complete any work using Cursor.

My usage has increased from 12% to 22% of the allowed limit, and I have achieved nothing with the 10% that has been used.

Steps to Reproduce

Execute any prompt in the Cursor IDE.

Sometimes it fails immediately, and sometimes the agent starts to work and then fails within 3-4 minutes.

Expected Behavior

Agent should complete response without connectivity errors.

Screenshots / Screen Recordings

cursor-connection-error.png
cursor-connection-error.png628×100 4.07 KB

Operating System

Windows 10/11

Current Cursor Version (Menu → About Cursor → Copy)

Version: 2.0.38 (system setup)
VSCode Version: 1.99.3
Commit: 3fa438a81d579067162dd8767025b788454e6f90
Date: 2025-10-29T20:45:40.883Z
Electron: 34.5.8
Chromium: 132.0.6834.210
Node.js: 20.19.1
V8: 13.2.152.41-electron.0
OS: Windows_NT x64 10.0.26100

For AI issues: which model did you use?

Composer, Auto

For AI issues: add Request ID with privacy disabled

Request ID: bbaefe1e-ba52-4c82-8f03-a5eb41b02fe7
ConnectError: [internal] Serialization error in aiserver.v1.StreamUnifiedChatRequestWithTools
at vscode-file://vscode-app/c:/Program%20Files/cursor/resources/app/out/vs/workbench/workbench.desktop.main.js:7337:396432

Does this stop you from using Cursor

Yes - Cursor is unusable

2

Thanks for reporting this! Can you please try these steps:

  1. Run network diagnostics and share:
  • Cursor Settings → Network → Run Diagnostics
  1. Disable HTTP/2:
  • Open Cursor Settings (Ctrl + ,)
  • Search for “HTTP/2”
  • Enable “Disable HTTP/2”
  • Restart Cursor
  1. Check firewall/antivirus issues on Windows

Let me know if any of these help