#sip

Notes

Writing

AUG 2026 · DEEP DIVE

Giving AI agents a real phone line

50 concurrent phone calls in userspace Go: p50 held at 20.00 ms at every load level — measured, not claimed. The tail is where it gets interesting.

Workshop

Projects

xPhone (Go version)

The embedded telephony data plane for Go. Place and answer calls on any SIP trunk — or be the trunk — with carrier failover, full SIP-signaling visibility, and call audio delivered as PCM frames on a channel, ready for STT or a voice agent. Battle-tested across 500,000+ production calls.

xbridge

Phone calls for every other language: one self-hosted binary turns SIP calls into WebSocket audio + REST call control. Twilio-compatible framing, so existing voice apps port over with the URL swapped.

Rust

xPhone (Rust version)

The same phone line for Rust — SIP and RTP implemented from scratch, zero telephony crate dependencies. Call audio as crossbeam channels of PCM frames; powers xbridge in production.

Rust