Participant attributes not persisting via PATCH during live voice call

We are building a custom agent desktop extension using the Embeddable Client App SDK. The goal is to sync data from our internal CRM back into Genesys Cloud during an active voice interaction. We need the participant attributes to update in real-time so other systems can react.

The weird symptom is that the API call succeeds, but the data doesn’t show up immediately in the UI or subsequent webhook events. It feels like the change is queued or ignored until the call ends.

Here is the C# code we are using to update the attributes. We fetch the current participant ID from the SDK context, then make a direct HTTP request to the REST API because the SDK doesn’t expose a simple method for this.

var client = new HttpClient();
client.DefaultRequestHeaders.Authorization = new AuthenticationHeaderValue("Bearer", token);

var payload = new
{
 attributes = new
 {
 orderId = "12345",
 customerTier = "Gold"
 }
};

var json = JsonSerializer.Serialize(payload);
var content = new StringContent(json, Encoding.UTF8, "application/json");

var response = await client.PatchAsync($"/api/v2/interactions/{interactionId}/participants/{participantId}", content);
Console.WriteLine(response.StatusCode); // Returns 200 OK

The response is always 200 OK. No error in the body. But if we call GET on that same participant endpoint immediately after, the attributes are empty. If we wait 5 minutes, they appear.

Is there a specific cache timeout we need to bypass? Or are we missing a flag in the PATCH body to force immediate persistence? We tried adding forceUpdate: true but that caused a 400 Bad Request.

The documentation says participant attributes are updated in real-time, but our experience suggests otherwise. We are in US/Pacific timezone, maybe there is some regional latency issue? We have tried different interaction types (voice vs chat) and voice seems to be the problem.

Also, we noticed that if we update the interaction metadata instead of the participant, it works instantly. Why is participant data treated differently? We need this for screen pop logic that triggers on attribute change.

Any ideas on how to force the update to stick immediately? We don’t want to rely on polling. The SDK event listener for participant updates doesn’t fire either. It’s very strange.