Genesys Cloud Guest WebSocket API: Handling message persistence and state on reconnection

NICE CXone API & Integrations
1

We’re building a custom chat UI using the raw WebSocket-based Guest API instead of the default widget to match our brand’s design system. The initial connection works fine, but we’re hitting a wall with state management when the connection drops or the page reloads.

Here’s the flow we’ve implemented:

  1. Initialize the guest session via POST /api/v2/webmessaging/guests
  2. Connect to the WebSocket endpoint returned in the response
  3. Subscribe to webmessaging:guest:message events

The issue is that when the WebSocket reconnects, we lose the message history. We’re currently trying to fetch the history using GET /api/v2/webmessaging/guests/sessions/{sessionId}/messages after reconnection, but the response seems to be paginated and sometimes misses messages sent during the brief disconnect window.

const fetchMessageHistory = async (sessionId) => {
 try {
 const response = await fetch(`https://api.mypurecloud.com/api/v2/webmessaging/guests/sessions/${sessionId}/messages?pageSize=50`, {
 headers: {
 'Authorization': `Bearer ${accessToken}`
 }
 });
 return await response.json();
 } catch (error) {
 console.error('Failed to fetch message history:', error);
 }
};

We’ve noticed that the messages array in the response doesn’t always include messages that were sent just before the disconnect. We’re wondering if there’s a timestamp-based query parameter we can use to fetch only messages after a certain point, or if we need to implement our own message queue on the client side to handle this.

Also, is there a recommended way to handle message deduplication? We’re seeing duplicate messages appear in the UI when the WebSocket reconnects and we fetch the history.

Any insights on best practices for handling message persistence and state in a custom chat UI using the Guest API would be greatly appreciated.