Guest API: Sending messages without the widget keeps failing with 403

Hey folks,

Trying to bypass the standard Genesys Messenger widget for a client who wants a fully custom UI. We’re building a simple React frontend that talks directly to the Guest API endpoints. The goal is to let users start a conversation and send messages without ever loading the heavy widget script.

Getting the initial token via POST /api/v2/webmessaging/guests/token works fine. We get a valid guestId and token back. The real trouble starts when we try to actually send a message using POST /api/v2/webmessaging/guests/{guestId}/messages.

Here’s the payload we’re sending:

{
 "content": "Hi there, need help with my order",
 "type": "text"
}

And the headers:

Authorization: Bearer <guest_token>
Content-Type: application/json

We keep hitting a 403 Forbidden. The error body just says "message": "Forbidden". No extra details. I’ve checked the token expiration, it’s fresh. I’ve also verified that the web messaging channel is enabled in the org settings and that the brand is active.

I noticed in the docs that you need to associate the guest with a specific brand or deployment. We’re passing the brandId in the initial token request, but maybe we need to do something else before sending messages? Or is there a specific permission missing on the guest profile?

Also, how are you all handling the polling for incoming messages? We’re just hitting GET /api/v2/webmessaging/guests/{guestId}/messages every 3 seconds, which feels clunky. Is there a websocket endpoint for the Guest API that we’re missing?

Any pointers would be great. Feels like we’re missing one small config step.