PATCH /conversations/webMessaging/participants/{id} returns 400 Bad Request for attributes

NICE CXone API & Integrations
1

I’m trying to update participant attributes mid-conversation using the Genesys Cloud Conversations API. We need to tag a user with a priority_level attribute while the chat is active. The endpoint is PATCH /api/v2/conversations/webMessaging/participants/{participantId}.

Here’s the JSON payload I’m sending:

{
 "attributes": {
 "priority_level": "high"
 }
}

The request returns 400 Bad Request with the error code invalid_request. The error message says attributes is not a valid field for this resource type. I checked the Swagger definition for Participant in the webMessaging context, and it doesn’t seem to expose an attributes object like the User resource does.

Is there a different endpoint for setting custom data on a web messaging participant? Or do I need to use a specific header? I’ve tried including Content-Type: application/json and the standard OAuth bearer token, but the response is the same. I’m using Kotlin with the genesys-cloud-kotlin SDK v2.18.0, but the issue persists when hitting the REST endpoint directly via curl too.