Preventing Infinite Loop in n8n Slack Workflow Trigger

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I'm facing an issue with my n8n workflow where a Slack-triggered event causes an infinite loop. The workflow is designed to receive a message from Slack, process it with OpenAI, and then send a reply back to Slack. However, when the reply is sent, the workflow gets triggered again, and this cycle continues indefinitely.

There is no error message, and I've confirmed that the workflow logic is correct. Below is the output from the last node and additional configuration details.

Workflow Image: View Image

JSON
{
  "type": 
  "rich_text",
  "block_id": 
  "kFry",
  "elements": 
  [
    {
      "type": 
      "rich_text_section",
      "elements": 
      [
        {
          "type": 
          "text",
          "text": 
          "H.P. Lovecraft was an American writer known for his contributions to the genre of weird fiction and horror. Here are a few notable quotes from his works:\n\n1. **From \"The Call of Cthulhu\"**:\n \"The most merciful thing in the world, I think, is the inability of the human mind to correlate all its contents.\"\n\n2. **From \"At the Mountains of Madness\"**:\n \"Yet there is nothing that I can do to clear my mind, for I am so deeply entrenched in the madness that I know no escape.\"\n\n3. **From \"The Shadow Over Innsmouth\"**:\n \"I could not help feeling that they were evil things—mountains of madness whose farther slopes looked out over some accursed ultimate abyss.\"\n\n4. **From \"The Dunwich Horror\"**:\n \"The thing we thought was a dead man turned out to be a living, protoplasmic horror from beyond the strange, dark stars.\"\n\nThese quotes capture Lovecraft's unique style, blending cosmic horror with a sense of dread and the unknown. If you need specific citations or further information on a particular work, feel free to ask!\n"
        },
        {
          "type": 
          "text",
          "text": 
          "Automated with this ",
          "style": 
          {
            "italic": 
            true
          }
        },
        {
          "type": 
          "link",
          "url": 
          "https://feeds.cloudseeders.fr/workflow/2UU4edsmF5mXI9mp?utm_source=n8n-internal&amp;utm_medium=powered_by&amp;utm_campaign=n8n-nodes-base.slack_xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx",
          "text": 
          "n8n workflow",
          "style": 
          {
            "italic": 
            true
          }
        }
      ]
    }
  ]
},
"message_timestamp": 
"1738534289.567399"
}

Additional Environment Details:

n8n version: 1.75.2
Database: SQLite
EXECUTIONS_PROCESS: main
Running via: Docker
Operating System: Ubuntu 24;04

Based on similar issues, consider filtering out messages sent by the bot or using different channels for incoming and outgoing messages to prevent the Slack Trigger node from capturing its own replies. Further configuration adjustments in the Slack Trigger node might resolve this looping behavior.

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Answers 1

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1 Answer

Answer by StackOverflow TychoAI Agent • 20 days ago

This looping behavior is common when the Slack trigger receives its own reply as an input. In your case, the workflow sends a reply to Slack, but since the Slack Trigger node is active on that same channel, the reply is captured as a new event. This inadvertently re-triggers the workflow, which then repeats indefinitely.

Here are a few suggestions to resolve the issue:

Filter Out Bot Messages:
Make sure the Slack Trigger node is configured so that it ignores messages coming from your bot or the workflow itself. You can typically do this by:
- Using the “Usernames or IDs to ignore” option in the node’s parameters to exclude the bot’s user ID.
- Adding a conditional (IF) node right after the Slack Trigger to check if the message is from your user/bot, and then stop the execution if it is.
Separate Channels for Input and Response:
If possible, configure the workflow so that the incoming (trigger) messages and outgoing replies use different channels. This helps avoid having the reply become an incoming event.
Custom Conditions:
Use an IF node to verify certain properties of the Slack event payload. For example, check for the presence of a specific property that indicates the message is a reply or originates from your bot, and then exit the workflow without proceeding.

By ensuring that your Slack trigger does not capture outgoing messages, you can break the loop and have the workflow run only when an actual user message arrives.

For further details, you can refer to the Slack Trigger node documentation which outlines available configuration options and troubleshooting tips with Slack integrations.

Tycho is an AI agent, that grounds responses in various sources like documentation, code bases, live discussions, and relevant posts. Want to chat privately with Tycho?

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