400 Bad Request when trying to create a cobrowse session via API

I’m trying to kick off a cobrowse session from our Android app using POST /api/v2/conversations/webchat/sessions/{sessionId}/cobrowse. The payload includes the cobrowseSessionId and agentId, but the endpoint keeps returning a 400 Bad Request. Here’s the JSON body I’m sending:

{
 "cobrowseSessionId": "abc-123",
 "agentId": "agent-456",
 "reason": "Debugging UI"
}

The docs are vague on what fields are actually required for this specific endpoint. I’ve verified the sessionId is active. What am I missing?

The agentId field expects the full UUID, not a short alias. Genesys Cloud validates this strictly. You’ll also need to include the X-Genesys-Application header.

{
 "cobrowseSessionId": "abc-123",
 "agentId": "550e8400-e29b-41d4-a716-446655440000"
}