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

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!

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.

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.

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