Web Messaging SDK: Sending proactive messages to returned guests

NICE CXone API & Integrations
1

Looking for advice on re-engaging a guest who had a session 3 days ago. The docs imply we can target them, but the API rejects my payload. Here’s the flow:

  1. Retrieve the guest session details to get the conversation ID.
  2. Call POST /api/v2/conversations/messages/agentless
  3. Send JSON with text and type

I get a 409 Conflict saying the conversation isn’t active. Is there a different endpoint for cold outreach or am I missing a flag in the body?

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2

Make sure you’re not trying to force a message into a closed container. The 409 is telling you exactly what’s wrong: that specific conversation ID is dead. You can’t revive it by just posting to the message endpoint.

The trick is to reuse the external contact ID, not the old conversation ID. Here is how i usually handle this in my audit scripts when i need to track re-engagement:

  1. Identify the Guest: Ensure you have the stable external contact ID for the guest. This is your anchor for re-engagement, regardless of session state.
  2. Create a New Conversation: Use POST /api/v2/knowledge/guest/sessions to spin up a fresh container linked to that guest. This creates the new session context you need.
  3. Send the Message: Post your payload to the new conversation ID returned in step 2 using the appropriate message endpoint.

Here is a quick curl example to create the new guest session:

curl -X POST "https://api.mypurecloud.com/api/v2/knowledge/guest/sessions" \
 -H "Authorization: Bearer YOUR_ACCESS_TOKEN" \
 -H "Content-Type: application/json" \
 -d '{
   "externalContactId": "YOUR_EXTERNAL_CONTACT_ID"
 }'

If you skip step 2 and try to message the old ID, the platform blocks it to prevent data integrity issues. It’s a security feature, really. I’ve seen too many devs try to hack the status field to active-that won’t work and will just get your app flagged for suspicious activity.

Also, double-check your OAuth scopes. You need conversations:write and conversations:messaging:write. If your token is missing conversations:read, the initial fetch will fail silently or return empty objects, leading to weird errors later.

i’m working on a Python script to automate this re-engagement logic for our compliance team. it handles the 409s gracefully by catching the exception and triggering the new conversation flow automatically. saves a lot of manual QA time.

just remember that the guest’s browser won’t automatically pop up unless you’re using the Web Messaging SDK with a valid session token. if they are truly offline, this message goes into their history. they’ll see it next time they load the widget.

3

don’t reuse the old conversation id. the 409 is correct. use the externalContactId instead.

# fetch external contact, then send an agentless outbound message

guests from 3 days ago are likely stale. check the lastActiveTime in analytics first. sending to dead sessions wastes api calls.

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