SSE endpoint MCP does not work with CLI

Support Bug Reports
1

Where does the bug appear (feature/product)?

Cursor CLI

Describe the Bug

Cursor CLI (cursor-agent) repeatedly fails at using one of my MCP servers which uses an SSE URL. The bug exists when I use Cursor-CLI either in interactive mode or in non-interactive

Strangely, Cursor IDE chat (i.e. agent in the sidebar) does not seem to have this same issue and can access the MCP tools correctly.

This may just be a feature that’s missing in the CLI and present in the IDE chat agent, but it currently feels like a bug to me.

Steps to Reproduce

  • Set an SSE URL in your MCP servers JSON, like so:
{
    "mcpServers": {
        "my-custom-mcp-sse": {
            "url": "https://my.custom.mcp.mydomain.net/sse"
        }
    }
}
  • Make sure it’s enabled in the Cursor IDE settings (may require manual enabling for the individual MCP tools).
  • Confirm that the IDE Chat agent correctly uses the MCP when requested. In order to guide it, I sometimes suggest “Using this MCP…”.
  • In your terminal, launch cursor-agent , then make the same request that’s relevant to this MCP. Note that it fails to use it correctly.
  • Alternatively, you can make the request with the non-interactive CLI params, `cursor-agent -p “Using this MCP, do so and so.”

Observed result:

Error (unhandledRejection): Error POSTing to endpoint (HTTP 405): Method Not Allowed
Error: Error POSTing to endpoint (HTTP 405): Method Not Allowed
    at StreamableHTTPClientTransport.send (file:///Users/my.username/.local/share/cursor-agent/versions/2025.08.15-dbc8d73/index.js:144905:15)
    at process.processTicksAndRejections (node:internal/process/task_queues:105:5)

Expected Behavior

Cursor CLI is able to correctly access MCP tools even when they use SSE URLs, as is the current functional behaviour with the Cursor IDE chat agent.

Operating System

MacOS

Current Cursor Version (Menu → About Cursor → Copy)

Version: 1.4.5
VSCode Version: 1.99.3
Commit: af58d92614edb1f72bdd756615d131bf8dfa5290
Date: 2025-08-13T02:08:56.371Z
Electron: 34.5.8
Chromium: 132.0.6834.210
Node.js: 20.19.1
V8: 13.2.152.41-electron.0
OS: Darwin arm64 24.5.0

Cursor CLI Version
2025.08.15-dbc8d73

Does this stop you from using Cursor

No - Cursor works, but with this issue

2

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