Open for Twilio

The mental model is simple: your Twilio account stays the source of truth for numbers, billing, and call routing. Open registers as a SIP trunk that lives next to it. When you decide a call should be handled by an AI, Twilio forwards the SIP INVITE to Open's endpoint, the AI picks up in under 200ms, and the conversation runs over the same SIP/RTP session Twilio already speaks. There's no proxy, no minute markup, and no separate number pool to manage.

For inbound calls, you have two equally valid paths. The straight-through path is Twilio Elastic SIP Trunking — you create a trunk, point its Origination URI at the Open SIP endpoint, and add your DIDs. Calls land on a Twilio number, Twilio sends them to Open, the AI answers. The other path keeps your existing TwiML or Studio flows in front: at the point you'd normally hand off to an agent, you <Dial><Sip> the Open URI and the AI takes over from there. Either way, the IVR, business hours, recording rules, and analytics you've already built in Twilio stay intact.

For outbound, Open opens a SIP session against your Twilio termination URI (typically your-trunk.pstn.twilio.com) using the digest credentials in your Twilio trunk's credential list. The calls show up in Twilio's call logs the same way human-dialed calls do, with whatever caller ID Twilio has approved on the trunk. You can run AI-driven outreach — lead callbacks, payment reminders, cancellation saves, post-purchase surveys — and still see every leg in Twilio Insights.

What the AI actually does on the call is where Open earns its keep. It doesn't read scripts. It listens, reasons over your knowledge base and tools, and acts: looking up an order in Shopify, creating a Zendesk ticket, scheduling a callback in Google Calendar, sending a payment link, charging a card, or warm-transferring to a human via SIP REFER or PSTN bridge with the full transcript and detected intent attached. Every call is recorded, transcribed, and trace-logged, so when something goes sideways you can replay why the AI made a decision — not just what it said.

Billing stays predictable. Twilio bills you at-cost for carrier minutes, exactly like today; Open never marks them up. Open itself charges per resolved conversation, not per agent or per seat, so spinning up ten AI agents on ten Twilio numbers costs the same baseline as spinning up one. If you're already on Twilio Flex or have a custom contact-center stack, Open slots in as another routing destination — it doesn't ask you to migrate.