MCP Trigger server could not connect: Supergateway client times out due to missing /messages POST

[Ignasi_Baste]

Technical report for n8n support forum

Describe the problem/error/question

I’m using the MCP Trigger node in n8n to receive connections via SSE from an external MCP client (supergateway). The workflow is active and includes a Function node to return a JSON response. However, the client times out after sending initialize.

What is the error message (if any)?

Error: MCP error -32001: Request timed out

Please share your workflow

[{
  "nodes": [
    {
      "parameters": {
        "model": "test-model"
      },
      "id": "MCP Trigger Node"
    },
    {
      "parameters": {
        "functionCode": "return [{ json: { result: 'OK - Workflow MCP response' } }];"
      },
      "id": "Function Node"
    }
  ],
  "connections": {
    "MCP Trigger Node": {
      "main": [ [ { "node": "Function Node", "type": "main", "index": 0 } ] ]
    }
  }
}]

Share the output returned by the last node

{
  "result": "OK - Workflow MCP response"
}

Information on your n8n setup

n8n version: 1.94.1
Database: SQLite
n8n EXECUTIONS_PROCESS setting: default (own, main)
Running n8n via: Docker
Operating system: Ubuntu

---

Additional context and analysis

• The SSE connection is established successfully.
• The event with /messages?sessionId=... is received.
• Workflow explicitly returns a response.
• However, the client (supergateway) does not handle posting to /messages and closes with a timeout.

Questions for n8n team

• Can n8n be configured to respond directly via SSE without requiring a POST to /messages?
• Or is it mandatory for clients to handle posting to /messages themselves?
• Is there an officially supported MCP client for n8n that correctly handles this flow?

Thank you for your help!

[cutecatcode]

Hi there!
Try to update the n8n first to latest version (1.100.1), maybe it’ll helps

[Ignasi_Baste]

Yes great I updated and I saw that in the new nodes they removed the SSE from the url and now it works for me.

Sorry for the inconvenience, thanks

[cutecatcode]

You’re welcome!