Patter
Open-source voice-AI SDK. The Vapi/Retell alternative for builders who want to own the stack.
Owning the whole voice stack between your agent and the phone network — agent loop, speech to text, text to speech, real-time audio and carrier — with the provider chosen per layer.
You want a managed voice platform; it is an SDK you run, and you still contract the model, speech and telephony providers behind it.
About Patter
Patter is the open-source SDK that gives your AI agent a phone number. You build the agent; Patter handles everything between it and the phone network — the agent loop, the language model, speech-to-text, text-to-speech, real-time voice, audio processing, and the telephony carrier.
Patter is the full voice stack between your application and the phone network — not just glue between an LLM and a carrier. It runs the agent loop and owns every layer of the call, and you pick the provider for each one. Compose them in Realtime, Pipeline, or Hybrid mode.
On top of the stack: an automatic LLM fallback chain (provider failover mid-call), built-in tools / call transfer / guardrails that behave identically on every carrier, and a vendor-neutral OpenTelemetry trace of each call.
Patter is an open-source project written primarily in Python, with 1.1k stars on GitHub. It was last updated in August 2026.
npx skills add patterai/skillsPatter vs. the alternatives
All 32 alternatives →| Record | Stars | Pricing | ||
|---|---|---|---|---|
| Patterthis listing | 1.1k | Python | MIT | Open source |
| Pipecat | 16k | Python | BSD-2-Clause | Open source |
| LiveKit Agents | 14k | Python | Apache-2.0 | Open source |
| xiaozhi-esp32-server | 11k | JavaScript | MIT | Open source |
| ten-vad | 2.3k | C | — | Open source |
| bailing | 1.8k | Python | MIT | Open source |
