WebRTC vs SIP for Voice AI: what I've learned from production deployments

I manage enterprise Voice AI deployments and recently wrote a detailed breakdown of this decision: https://www.voiceaipm.com/2026/04/webrtc-vs-sip-which-protocol-for-your.html The short version of what I've found in production: If users call from a real phone number (mobile/landline): you need SIP. No way around it - the PSTN speaks SIP. If the voice interface lives in a browser (click-to-call, web widget): WebRTC. Opus codec, no carrier cost, NAT traversal handled automatically. Enterprise deployments almost always end up needing both, bridged via an SBC. This is where most teams underestimate the complexity. The mistake I made on one project: chose WebRTC because the demo worked great in a browser, then discovered the client's contact centre platform only accepted SIP. Spent 6 weeks building a gateway that wasn't in the scope or budget. A few things I'm genuinely curious about from people building in this space: Are you using a managed Voice AI platform (Vapi, Retell AI, Bland AI) or