Step one: the external fraud service needs to push a risk score back to the participant object while the voice leg is active, so we’re hitting PATCH /api/v2/conversations/voice/{conversationId}/participants/{participantId} with {"custom_attributes": {"fraud_risk": 0.92}}. Endpoint spits back a 200 OK but the key just disappears on the next GET request. REST Proxy isn’t timing out, so CXone isn’t rejecting the payload. It’s just dropping the key mid-stream.