[BUG] MCP SSE SessionID must be provided

Preflight Checklist

• [x] I have searched existing issues and this hasn't been reported yet
• [x] This is a single bug report (please file separate reports for different bugs)
• [x] I am using the latest version of Claude Code

What's Wrong?

I'm trying to make use of https://go.dev/gopls/features/mcp with a mcp server using Claude Code.

"mcpServers": {
    "gopls": {
      "type": "http",
      "url": "http://localhost:8092"
    }
  }

But the MCP fails to connect.

Running MCP inspector allows me to properly connect and list tools etc.

What Should Happen?

I should be able to use the MCP server as advised. Session management seems to say that sessionID can be enforced my MCP server

https://modelcontextprotocol.io/specification/2025-03-26/basic/transports#session-management

Error Messages/Logs

MCP Debug logs

{ "error": "Connection failed: Error POSTing to endpoint (HTTP 400): sessionid must be provided\n", "timestamp": "2025-10-06T14:30:04.645Z", "sessionId": "eac86082-5851-4654-82a4-a9e5b3404529", "cwd": "/Users/path" },
  {
    "error": "Error: Error POSTing to endpoint (HTTP 400): sessionid must be provided\n\n    at send (/$bunfs/root/claude:846:32606)\n    at processTicksAndRejections (native:7:39)",
    "timestamp": "2025-10-06T14:30:04.645Z",
    "sessionId": "eac86082-5851-4654-82a4-a9e5b3404529",
    "cwd": "/Users/path"
  },

Steps to Reproduce

1. run gopls serve -mcp.listen=localhost:8092
2. Add MCP server as above
3. Start claude code
4. /mcp <- connection will fail

Claude Model

None

Is this a regression?

I don't know

Last Working Version

_No response_

Claude Code Version

2.0.8 (Claude Code)

Platform

Other

Operating System

macOS

Terminal/Shell

Terminal.app (macOS)

Additional Information

_No response_