We are trying to bypass the standard Messenger widget to build a fully custom chat UI for our agent desktop using the Embeddable Client App SDK. The goal is to send messages directly via the Guest API without rendering the Genesys provided widget.
I have successfully generated a guest token using the /api/v2/conversations/messaging/external/guests endpoint with a valid application/json body containing the name and email. The response returns a 201 Created with a valid guestId and accessToken.
However, when I attempt to post a message to /api/v2/conversations/messaging/external/guests/{guestId}/messages using that accessToken in the Authorization: Bearer <token> header, I get a 403 Forbidden response. The error payload is empty.
Here is the curl equivalent I am testing with:
curl -X POST “https://api.mypurecloud.com/api/v2/conversations/messaging/external/guests/abc-123/messages”
-H “Authorization: Bearer <guest_access_token>”
-H “Content-Type: application/json”
-d ‘{“text”: “Hello from custom UI”}’
I have verified that the OAuth client associated with the guest creation has the messaging:guest:write scope. The token looks valid when decoded. Is there a specific permission required on the messaging channel or the external messaging application configuration that allows direct API access for guests? The documentation is sparse on this specific flow.
Are you using the guest token in the Authorization header or just passing it as a query param? That’s usually where people trip up.
The Guest API is weirdly specific about how it wants the token. You can’t just slap it in the standard Bearer scheme like you would with a normal OAuth token. The docs say: “Include the guest token in the Authorization header with the prefix ‘Guest’”. If you’re sending Authorization: Bearer <guest_token>, the API returns 403 because it doesn’t recognize the scheme for that specific endpoint.
Here’s how it should look in C# using HttpClient. Notice the custom header format.
var client = new HttpClient();
client.BaseAddress = new Uri("https://api.mypurecloud.com");
// Don't use AddBearerToken or standard OAuth helpers here
client.DefaultRequestHeaders.Authorization =
new AuthenticationHeaderValue("Guest", guestTokenResponse.GuestToken);
var message = new {
text = "Hello from custom UI",
type = "text"
};
var content = new StringContent(
JsonConvert.SerializeObject(message),
Encoding.UTF8,
"application/json");
var response = await client.PostAsync(
$"/api/v2/conversations/messaging/external/guests/{guestId}/messages",
content);
Also double-check the guestId in the URL. It comes from the initial response body, not the token itself. I’ve seen folks mix those up. The token authenticates the session, but the ID targets the specific guest entity created in that first call. If you get the ID wrong, it’s a 404, but if the header scheme is wrong, it’s a 403. Make sure your HttpClient isn’t automatically appending Bearer from some global handler.