I’m building a custom web messaging UI using the Embeddable Client App SDK patterns, so I’m avoiding the standard Messenger widget entirely. The goal is to use the Guest API to send and receive messages directly. I’ve got the OAuth token sorted via the client credentials flow, and I can successfully fetch the conversation ID using the GET endpoint. The issue hits when I try to post a message.
I’m hitting POST /api/v2/conversations/webmessaging/messages with the following payload:
{
"fromId": "guest-token-123",
"conversationId": "conv-xyz-789",
"text": "Hello support team"
}
The response is consistently a 404 Not Found. The error body says entityNotfound. I’ve double-checked the fromId against the guest token returned by the auth endpoint, and the conversationId matches what I got from the initial create call. I’m using the UK London edge. Is there a specific header I’m missing, or does the Guest API require a different endpoint structure than the standard agent SDK? I’ve tried adding the X-Genesys-Client header but that didn’t change anything.