Realtime API SIP inbound calls failing again before webhook dispatch

We are seeing the same issue on our production voice service as well. Our setup is also Twilio SIP → OpenAI Realtime API SIP endpoint. Current symptoms: * New SIP calls to the OpenAI Realtime SIP endpoint fail immediately. * Twilio reports SIP 400 failures. * The OpenAI webhook is not triggered. * We do not receive the realtime.call.incoming event. * Our accept flow is never reached. * We have not made any relevant changes to our application code, Twilio settings, or OpenAI configuration. On our side, the issue appears to have started around 2026-05-13 09:30 JST / 2026-05-13 00:30 UTC as well. This looks like the same regression affecting Realtime API SIP ingress before webhook dispatch. Any confirmation from the OpenAI team would be appreciated.