Constant Connection Error with any model

Support Bug Reports
1

Where does the bug appear (feature/product)?

Cursor IDE

Describe the Bug

When I send any message to the agent it instantly throws Connection Error. It throws an error on any retry attempt.
We use Claudeflare WARP in or organization, but it doesn’t matter if it’s enabled or disabled.
My home network doesn’t have any constraints.
I also have Sentinel One on my machine, I’m not sure if it can cause this because everything was fine before, I’ve been working like this for many months. The issue occurred 5th December at the first time. I thought it was some temporarily server issue, but it persists.
If I disable HTTP/2 it starts working, but it works worse.

Steps to Reproduce

Send any message to the agent.

Expected Behavior

No connection error.

Operating System

Windows 10/11

Current Cursor Version (Menu → About Cursor → Copy)

Version: 2.1.50 (user setup)
VSCode Version: 1.105.1
Commit: 56f0a83df8e9eb48585fcc4858a9440db4cc7770
Date: 2025-12-06T23:39:52.834Z
Electron: 37.7.0
Chromium: 138.0.7204.251
Node.js: 22.20.0
V8: 13.8.258.32-electron.0
OS: Windows_NT x64 10.0.26200

For AI issues: which model did you use?

Any model.

For AI issues: add Request ID with privacy disabled

Maybe this can be useful. I get this each time I try.

Request ID: e920a0ed-7029-43e8-af35-4870d8e37b6f
ConnectError: [internal] 314368:error:10000410:SSL routines:OPENSSL_internal:SSLV3_ALERT_HANDSHAKE_FAILURE:..\..\third_party\boringssl\src\ssl\tls_record.cc:486:SSL alert number 40

    at nsu.$streamAiConnect (vscode-file://vscode-app/c:/Users/username/AppData/Local/Programs/cursor/resources/app/out/vs/workbench/workbench.desktop.main.js:6409:406134)
    at async vscode-file://vscode-app/c:/Users/username/AppData/Local/Programs/cursor/resources/app/out/vs/workbench/workbench.desktop.main.js:565:80832
    at async Object.run (vscode-file://vscode-app/c:/Users/username/AppData/Local/Programs/cursor/resources/app/out/vs/workbench/workbench.desktop.main.js:6477:42602)
    at async o (vscode-file://vscode-app/c:/Users/username/AppData/Local/Programs/cursor/resources/app/out/vs/workbench/workbench.desktop.main.js:2815:1269)
    at async Promise.allSettled (index 0)
    at async fHr.run (vscode-file://vscode-app/c:/Users/username/AppData/Local/Programs/cursor/resources/app/out/vs/workbench/workbench.desktop.main.js:2815:6519)

Request ID: 9606acdf-0d3d-4605-8d0e-0edc2dcf2deb
ConnectError: [internal] 314368:error:10000410:SSL routines:OPENSSL_internal:SSLV3_ALERT_HANDSHAKE_FAILURE:..\..\third_party\boringssl\src\ssl\tls_record.cc:486:SSL alert number 40

    at nsu.$streamAiConnect (vscode-file://vscode-app/c:/Users/username/AppData/Local/Programs/cursor/resources/app/out/vs/workbench/workbench.desktop.main.js:6409:406134)
    at async vscode-file://vscode-app/c:/Users/username/AppData/Local/Programs/cursor/resources/app/out/vs/workbench/workbench.desktop.main.js:565:80832
    at async Object.run (vscode-file://vscode-app/c:/Users/username/AppData/Local/Programs/cursor/resources/app/out/vs/workbench/workbench.desktop.main.js:6477:42602)
    at async o (vscode-file://vscode-app/c:/Users/username/AppData/Local/Programs/cursor/resources/app/out/vs/workbench/workbench.desktop.main.js:2815:1269)
    at async Promise.allSettled (index 0)
    at async fHr.run (vscode-file://vscode-app/c:/Users/username/AppData/Local/Programs/cursor/resources/app/out/vs/workbench/workbench.desktop.main.js:2815:6519)

Additional Information

Network Diagnostics with HTTP/2 enabled is fine.
DNS:

[2025-12-08T14:46:06.941Z] Host: api2.cursor.sh
[2025-12-08T14:46:06.943Z] Servers: ::ffff:127.0.2.2,::ffff:127.0.2.3,127.0.2.2,127.0.2.3
[2025-12-08T14:46:06.943Z] Resolved to 104.18.18.125 in 29ms
[2025-12-08T14:46:06.958Z] Resolved to 104.18.18.125 in 1ms
[2025-12-08T14:46:07.001Z] Resolved to 104.18.18.125 in 2ms
[2025-12-08T14:46:07.027Z] Resolved to 104.18.18.125 in 0ms
[2025-12-08T14:46:07.050Z] Host: api2.cursor.sh
[2025-12-08T14:46:07.050Z] Servers: system
[2025-12-08T14:46:07.050Z] Resolved to 2606:4700::6812:127d, 2606:4700::6812:137d, 104.18.18.125, 104.18.19.125 in 1ms
[2025-12-08T14:46:07.073Z] Resolved to 2606:4700::6812:127d, 2606:4700::6812:137d, 104.18.18.125, 104.18.19.125 in 0ms
[2025-12-08T14:46:07.097Z] Resolved to 2606:4700::6812:127d, 2606:4700::6812:137d, 104.18.18.125, 104.18.19.125 in 0ms
[2025-12-08T14:46:07.124Z] Resolved to 2606:4700::6812:127d, 2606:4700::6812:137d, 104.18.18.125, 104.18.19.125 in 0ms
[2025-12-08T14:46:07.124Z] Result: true

HTTP/2:

[2025-12-08T14:46:06.871Z] Start
[2025-12-08T14:46:06.987Z] Host: api2.cursor.sh
[2025-12-08T14:46:06.987Z] Protocol: h2
[2025-12-08T14:46:06.987Z] Result: true in 116ms

SSL:

[2025-12-08T14:46:06.872Z] Start
[2025-12-08T14:46:07.138Z] URL: https://api2.cursor.sh/
[2025-12-08T14:46:07.138Z] Status: 200
[2025-12-08T14:46:07.138Z] IP: 104.18.18.125
[2025-12-08T14:46:07.138Z] Issuer: C=US; O=Google Trust Services; CN=WE1
[2025-12-08T14:46:07.138Z] Name: api2.cursor.sh
[2025-12-08T14:46:07.138Z] AltName: DNS:api2.cursor.sh, DNS:*.api2.cursor.sh, DNS:prod.authentication.cursor.sh
[2025-12-08T14:46:07.138Z] DNS Time: 5ms
[2025-12-08T14:46:07.138Z] Connect Time: 44ms
[2025-12-08T14:46:07.138Z] TLS Time: 21ms
[2025-12-08T14:46:07.138Z] Result: true in 266ms

API: nothing there.

PING:

[2025-12-08T14:46:06.890Z] Sending ping 1
[2025-12-08T14:46:07.255Z] Response: 'ping' in 365ms
[2025-12-08T14:46:07.255Z] Sending ping 2
[2025-12-08T14:46:07.542Z] Response: 'ping' in 287ms
[2025-12-08T14:46:07.542Z] Sending ping 3
[2025-12-08T14:46:07.769Z] Response: 'ping' in 227ms
[2025-12-08T14:46:07.769Z] Sending ping 4
[2025-12-08T14:46:08.059Z] Response: 'ping' in 290ms
[2025-12-08T14:46:08.059Z] Sending ping 5
[2025-12-08T14:46:08.313Z] Response: 'ping' in 254ms
[2025-12-08T14:46:08.313Z] Result: true

CHAT:

[2025-12-08T14:46:06.900Z] Starting stream
[2025-12-08T14:46:07.494Z] Response: 'foo' in 580ms
[2025-12-08T14:46:08.471Z] Response: 'foo' in 977ms
[2025-12-08T14:46:09.483Z] Response: 'foo' in 1012ms
[2025-12-08T14:46:10.498Z] Response: 'foo' in 1015ms
[2025-12-08T14:46:11.460Z] Response: 'foo' in 961ms
[2025-12-08T14:46:12.552Z] Result: true

AGENT:

[2025-12-08T14:46:06.912Z] Starting stream
[2025-12-08T14:46:06.914Z] Pushing first message
[2025-12-08T14:46:07.479Z] Response: 'foo' in 565ms
[2025-12-08T14:46:08.021Z] Pushing next message
[2025-12-08T14:46:08.210Z] Response: 'foo' in 731ms
[2025-12-08T14:46:08.726Z] Pushing next message
[2025-12-08T14:46:08.919Z] Response: 'foo' in 709ms
[2025-12-08T14:46:09.457Z] Pushing next message
[2025-12-08T14:46:09.601Z] Response: 'foo' in 682ms
[2025-12-08T14:46:10.124Z] Pushing next message
[2025-12-08T14:46:10.424Z] Response: 'foo' in 823ms
[2025-12-08T14:46:10.425Z] Result: true

MARKETPLACE:

[2025-12-08T14:46:06.866Z] Host: marketplace.cursorapi.com
[2025-12-08T14:46:07.868Z] Response in 1002ms
[2025-12-08T14:46:07.868Z] Response: 200 
[2025-12-08T14:46:07.868Z] Response Type: cors
[2025-12-08T14:46:07.868Z] Server: null
[2025-12-08T14:46:07.868Z] Result: OK in 1002ms

Does this stop you from using Cursor

Sometimes - I can sometimes use Cursor

1 Like
2

Hey, thanks for the detailed report.

This is a known HTTP/2/TLS bug that started affecting many users since December 5, and the team is working on a fix. You’ve already found the right workaround - disable HTTP/2.

About the degraded experience with HTTP/2 disabled - could you clarify what exactly is worse? Response speed, latency, or something else? This will help engineers set priorities.

I’ll pass this to the team since it affects many users. For now, I recommend continuing with HTTP/2 disabled.

3

Thanks for the response. Hope everything will be fixed.

Regarding quality I can’t tell for sure. It’s just seemed to me that Auto mode gave me worse output. But it’s hard to measure because each task is different.)

1 Like
4

@deanrie
I’m having the same issue.

Disabling HTTP/2 helps, but I’ve noticed a slower work of Auto mode too.

Also, the quality of the results is worse.

For example, I have a Figma design for an iOS app that I am developing, and I am using Figma MCP. The Agent is really bad at understanding fonts and colors. It’s not able to export images from the Figma design (though claude-sonnet-4.5 was able to do it). It all worked well before.

Even when I asked Claude Sonnet about the exact instruction on how to export images and then provided it to Auto mode, it was not able to do it. It just opened the browser in Cursor with Figma.

1 Like
5

Now it works for me with HTTP/2. I’ve noticed that Auto model has been changed to something else. It’s very fast but it doesn’t think much. Maybe it’s Composer 1 instead of GPT.
So, we need to be more careful.

6

Yet again.
But there is something new.

image
image710×877 40.2 KB

Strange that I had one chat today where everything was working perfectly fine but when I created a new chat there were connection errors. If I send something in previous chat it still was fine. So that’s really strange.

7

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