Icon_url for Retool Workflows is not being set correctly

💬 Workflows
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1
  1. My goal:
  • I want to update the icon_url for my Slack message that is being triggered via a Retool workflow.
  1. Issue:
  • For some reason, the icon being used is an old image. I have updated the icon to use a new URL but for some reason its still using the old URL as is seen by the response JSON object.
  • The tool tip says I need to set "as_user" to false, but I cannot find that parameter.
  1. Steps I've taken to troubleshoot:
  • Tried to edit URL
  • Ran multiple times to test
  • Viewed response JSON object and seen that icons/image_48 is using the OLD URL.
  1. Additional info: (Cloud or Self-hosted, Screenshots)
    Screenshot 2025-08-08 at 15.40.36 (2)
    Screenshot 2025-08-08 at 15.40.36 (2)1920×1080 363 KB
3

Hi @michael_burton, after checking out the slack api docs, you may have to make sure your app has this additional scope: chat:write.customize. The as_user parameter seems to be specific to legacy apps, and setting it to false indicates that it is a bot message.

You could also try setting the icon_emoji? since it overrides icon_url.

Let me know if this was helpful!

4

Hi @Mike_M - thanks for the reply!

I have tried all of your suggested approaches and am still having no luck...

  • The Retool to Slack connection I have authorised has: chat:write.customize permitted.
  • The as_user parameter as you say is legacy and no longer available
  • I have tried using the icon_emoji as apposed to icon_url and still have no have not had any success.

What I really don't understand is where the image URL that is being used is being set...(this can be seen in screenshot in original message)

5

I just tested this out, and I sent a message with an icon_url set to a url from a random icon from google images. The response I got was similar, as it was turned into a url linking to a slack aws bucket, but for me it was the same image I sent and it was successful. I'm personally having trouble reproducing this specific bug. Here are my scopes if it is helpful:

Screenshot 2025-08-22 at 3.53.34 PM
Screenshot 2025-08-22 at 3.53.34 PM1312×532 30.9 KB

What I really don't understand is where the image URL that is being used is being set...(this can be seen in screenshot in original message)

When I check the urls in your screenshot, I see that the old image being sent back in the response is an orange triangle logo, which is not a default slack image and must have been set at some point.

Is it possible that your slack organization has a setting turned on to override icon_url? This could be a setting called "Always Show My Bot as the App" in your App Home, or "Always use this icon and name" within your "Incoming Webhooks" configuration.

6

Hi @michael_burton, just checking back in to see if you were able to solve this.