Studio REST Proxy POST to /api/v2/conversations/messaging/{conversationId}/messages returns 403

We are trying to automate sending a canned response during an active chat session using a script. The goal is to inject a standard greeting without agent intervention when specific IVR criteria are met.

I’ve set up a REST Proxy action in . It constructs the JSON payload and hits the endpoint. The token generation works fine; I can see the valid bearer token in the debug log. The conversation ID is pulled from the current interaction context.

Here is the payload I’m sending:

{
 "text": "Thank you for contacting support. An agent will be with you shortly.",
 "type": "text"
}

The request fails with a 403 Forbidden error. The response body is empty.

Steps tried:

  • Verified the OAuth token has the conversations:messaging:write scope. It does.
  • Checked the conversation status. It is ACTIVE.
  • Tried sending a plain string instead of the JSON object. Same result.
  • Confirmed the user associated with the token has the necessary permissions in the admin console.
  • Tested the same endpoint via Postman using the same token. It works there.

The script seems to be the bottleneck. Is there a specific header missing in the REST Proxy configuration? Or is the runtime sandbox blocking outbound writes to the messaging channel?

The script runs without throwing a error, just returns the 403 from the API call.