MCP: Chat-trigger workflow returns ‘Unknown execution mode’

Questions
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1

Hello everyone,

I’m testing the new MCP integration. I have a simple workflow that uses the chatTrigger node (connected to an AI Agent). It runs correctly when I test it directly inside n8n.

However, when I trigger it through MCP using the official /execute_workflow tool in chatgpt, n8n returns an error and the execution never runs.

Payload sent to n8n (as required by the MCP tool schema):

{

“workflowId”: “grn28ew0JQ0x7J7”,

“inputs”: {

"type": "chat",

“chatInput”: “What is the best pecan pie recipe?”

}

}

Error returned by n8n:

{“success”: false, “executionId”: null, “error”: “Unknown execution mode”}

Each attempt appears in Executions as “Queued – starting soon”.

Looking for guidance on why MCP-triggered executions for chatTrigger workflows return “Unknown execution mode”.

Thanks in advance!

2

Hey! The “Unknown execution mode” error suggests the MCP tool is sending an execution format that N8n does not recognize for chatTrigger workflows. ChatTrigger nodes expect a different execution context than standard webhook triggers. Try using a Webhook node instead of chatTrigger for MCP integrations, or check if your N8n version fully supports MCP-initiated chat workflows. Also verify your MCP server configuration matches what N8n expects—this feature is still pretty new and might need specific setup adjustments.

3

Hi,

Thanks. Yes, chatgpt and Gemini recommended to use a webhook. I was just trying to make it work with the chat trigger. I will check also the other things you mentioned.