Client error for command Streamable HTTP error: Failed to open SSE stream: Not Acceptable

Support Bug Reports
1

Where does the bug appear (feature/product)?

Cursor IDE

Describe the Bug

Client error for command Streamable HTTP error: Failed to open SSE stream: Not Acceptable

Steps to Reproduce

{
“mcpServers”: {
“Snowflake MCP Server”: {
“url”: “mcp_server”,
“transport”: {
“type”: “sse”
},
“headers”: {
“Authorization”: “Bearer <JWT_TOKEN>”,
“Accept”: “text/event-stream, application/json”,
“Cache-Control”: “no-cache”,
“Connection”: “keep-alive”
}
}
}
}

Expected Behavior

The MCP server should turn green. It shows the error
Client error for command Streamable HTTP error: Failed to open SSE stream: Not Acceptable

Operating System

Windows 10/11

Current Cursor Version (Menu → About Cursor → Copy)

Version: 2.2.44 (system setup)
VSCode Version: 1.105.1
Commit: 20adc1003928b0f1b99305dbaf845656ff81f5d0
Date: 2025-12-24T21:41:47.598Z
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 10.0.26100

Does this stop you from using Cursor

Yes - Cursor is unusable

2

Hey there!

Can you give Cursor 2.3 a try? If it hasn’t rolled out to you automatically yet, you can download it from Download · Cursor. There have been several improvements around MCP since 2.2.

3

Hi Colin,

Tried 2.3 as well. Still the same error.

Thanks,

Sameer

4

Thanks!

In the meantime, I found another case of a user dealing with this and the Snowflake MCP server.

Good news: The MCP server should still work just fine. Can you confirm that?

There’s an open PR to change this from an error to a warning. I’ll check on its status!

5

Hi Colin,

Yes you are right. The MCP setup still works.

Thank you so much. Hopefully the error will be fixed shortly.

Thanks,
Sameer

6

The fix has been pushed to 2.3 (moving the error to a warning) so in your next auto-update, you should no longer see the error!