Sharing a project I help maintain — Flowcat, an Apache-2.0 native-Rust runtime for real-time voice AI agents (phone + WebRTC). It runs the whole voice pipeline (STT → LLM → TTS, or a single speech-to-speech model) as one self-contained binary you host yourself — in your own VPC or fully air-gapped. No hosted control plane, bring your own keys, and a call’s audio never leaves your infra.

It’s a clean-room counterpart to pipecat’s architecture, but native Rust:

• each pipeline stage is its own tokio task behind a bounded mpsc channel (natural backpressure)
• the hot audio frame is an Arc<AudioFrame>, so each hop moves a pointer, not a PCM copy
• no GIL, so one process uses all cores and holds a flat tail under load (measured: flat ~0.6ms p99 framework overhead from 10 to 2,000 concurrent calls on one box)
• native SIP/RTP, so a single binary can terminate phone calls with no FreeSWITCH

The linked writeup has the full Rust design + a reproducible benchmark vs pipecat (with the honest caveat that it’s framework overhead, not end-to-end voice latency — that’s provider-bound).

Repo: https://github.com/AreevAI/flowcat

Apache-2.0, pre-1.0, built in the open. Disclosure: I help maintain it — happy to talk architecture or the SIP stack.