Problem with Slack Modal and views.open: invalid_trigger_id

[guenodev]

Hi everyone

I’m trying to open a Slack modal using the views.open method triggered by a Slash Command (/enviar-credenciales) in an n8n workflow. The flow works perfectly when tested via cURL, but fails when triggered via n8n.

Workflow Setup

1. Webhook Node

• Method: POST

• Receives the Slack Slash Command.

2. Code Node

• Extracts trigger_id from body.trigger_id

• Builds the modal view with multiple inputs (language, email list, credentials, etc.).

3. HTTP Request Node

• URL: https://slack.com/api/views.open

• Method: POST

• Headers:

{
  "Authorization": "Bearer xoxb-...",
  "Content-Type": "application/json"
}

• Body (as JSON with expressions):

{
  "trigger_id": "={{ $json.trigger_id }}",
  "view": {{ JSON.stringify($json.view) }}
}

4. Respond to Webhook Node

• Sends a basic response like:

{
  "text": "📤 Sending modal..."
}

Result

The HTTP Request node returns the following error:

{
  "ok": false,
  "error": "invalid_trigger_id"
}

Here’s the incoming trigger_id from the webhook payload:

"trigger_id": "8653186027153.716539322848.603f5d38c28b11be04d745b93a79edb4"

When using the exact same payload via cURL, the modal opens successfully.

My Question

Is there something in how n8n handles Slack webhook data that could cause the trigger_id to become invalid by the time the HTTP request is made?

Any examples of working Slack + views.open workflows in n8n that I can look at would be super helpful

Thanks in advance!

[ThinkBot]

Hey, could you ctl a, ctl c on your entire workflow, and click the ‘</>’ button in the forums response and paste the workflow between the backticks that appear?

That would help give some more context on what is happening.