Guest API: Sending proactive notification to closed web session returns 409

NICE CXone API & Integrations
1

I’ve been working on a custom agent desktop extension that needs to notify customers via web messaging after their initial session has ended. The goal is to send a proactive message to a guest who previously connected via the Web Messaging SDK. I’m using the Genesys Cloud Guest API to create a new message for an existing conversation.

Here’s the flow I’m implementing:

  1. Retrieve the conversation ID from our internal DB (it’s a closed web messaging conversation).
  2. Call POST /api/v2/conversations/messaging/messages with the conversation ID and the new message payload.
  3. Expect the message to be delivered to the guest’s browser if they still have the tab open, or stored for later.

The issue is that I keep getting a 409 Conflict error with the message: Conversation is not in a state that allows adding messages. The conversation status is closed. I assumed that since the guest might still have the widget open, we could inject a message. But it seems the API is strict about the conversation state.

Here’s the JSON payload I’m sending:

{
 "from": {
 "name": "Support Bot",
 "id": "bot-id-123"
 },
 "text": "Is there anything else we can help you with?",
 "conversationId": "existing-closed-conversation-id"
}

I’ve checked the docs and it mentions that proactive messages are supported, but it’s unclear if that applies to closed conversations or only open ones. I tried changing the conversation status to open first using PATCH /api/v2/conversations/messaging/conversations/{id}, but that fails with a 400 Bad Request saying the status change is invalid for a closed conversation.

Is there a way to reopen a conversation programmatically to send a notification? Or should I be using a different endpoint, like the Guest API’s sendProactiveMessage? I haven’t found clear examples of that in the SDK docs. Any pointers would be appreciated.

2

Docs state: “A conversation must be active to receive new messages.” You can’t inject messages into a closed session. Re-open the conversation first via POST /api/v2/conversations/{id}/participants with an active participant, then send the message.

3

you’re trying to push to a dead session? that’s a hard no. re-open the conversation first with POST /api/v2/conversations/web/{conversationId}/participants to add the guest back, then your message will go through.