Where does the bug appear (feature/product)?
Cursor IDE
Describe the Bug
In native HTTP/2 mode, Settings > Network > Run Diagnostic reports every
check as Success except Chat, which fails with [unknown] HTTP 464
on every run (15/15 across two regional proxies). Agent — which also
uses HTTP/2 streaming to the same host — passes in the same run.
Steps to Reproduce
Steps to Reproduce
Environment
Cursor 3.11.25, Windows 11
Behind an explicit corporate HTTP proxy currently in passthrough
(api2.cursor.sh presents the genuine Amazon RSA 2048 M01
certificate, no SSL re-signing, no HTTP 403)
settings.json in native HTTP/2 mode (no disableHttp2, no
disableHttp1SSE):
{
“http.systemCertificates”: true,
“http.experimental.systemCertificatesV2”: true,
“http.proxy”: “http://:8080”,
“http.proxySupport”: “override”
}
Steps
Fully quit and relaunch Cursor (not just Reload Window).
Open Settings > Network and set HTTP Compatibility Mode to HTTP/2.
Click Run Diagnostic.
Observe the results.
Click Run Diagnostic several more times.
Expected: Chat = Success (five streamed responses, about one second
apart), like the Agent check.
Actual: Every run reports HTTP/2, SSL, API, Ping, Agent and
Authentication as Success, but Chat fails with [unknown] HTTP 464.
Reproduced 15/15 consecutive runs across two separate regional proxies.
Agent, which also uses HTTP/2 streaming to the same host, passes in the
same run.
Note: the command-line step below proves that an HTTP/1.1 request to
this endpoint yields 464. It does not by itself prove Cursor’s Chat
client sends HTTP/1.1; that is an inference from the 464 plus the fact
that Agent’s HTTP/2 stream and independent HTTP/2 streams to the same
endpoint succeed.
Expected Behavior
Expected Behavior
The Chat check should report Success, returning five streamed
responses about one second apart, exactly as the Agent check does. Both
use HTTP/2 streaming to the same host (api2.cursor.sh) through the
same proxy, so if Agent passes, Chat should pass in the same run.
Actual Behavior
Every run reports HTTP/2, SSL, API, Ping, Agent and Authentication as
Success, but Chat fails with [unknown] HTTP 464. Reproduced 15/15
consecutive runs across two separate regional proxies. Agent, which
also uses HTTP/2 streaming to the same host, passes in the same run.
Note: the command-line step below proves that an HTTP/1.1 request to
this endpoint yields 464. It does not by itself prove Cursor’s Chat
client sends HTTP/1.1; that is an inference from the 464 plus the fact
that Agent’s HTTP/2 stream and independent HTTP/2 streams to the same
endpoint succeed.
Screenshots / Screen Recordings
cursor_chat_http464_report.txt (4.19 KB)
Operating System
Windows 10/11
Version Information
Cursor version: 3.11.25
OS: Windows 11
Network: Corporate proxy (explicit HTTP proxy, identifies as
Fortinet-Proxy/1.0), currently passthrough — genuine Amazon
certificate on api2.cursor.sh, no SSL re-signing.
Version: 3.11.25 (user setup)
VS Code Extension API: 1.125.0
Commit: fc2563ec93d793fc275eef734405a4fdf8b47b20
Date: 2026-07-15T01:27:41.754Z
Layout: IDE
Build Type: Stable
Release Track: Default
Electron: 40.10.3
Chromium: 144.0.7559.236
Node.js: 24.15.0
V8: 14.4.258.32-electron.0
xterm.js: 6.1.0-beta.256
OS: Windows_NT x64 10.0.22631
Does this stop you from using Cursor
No - Cursor works, but with this issue