Patter

Patter is an open-source voice AI software development kit that connects AI agents to real phone calls.

Patter is an open-source voice AI software development kit designed for builders who want to own their stack. It connects any AI agent to phone calls in four lines of code using Python or TypeScript. The platform offers end-to-end engines like OpenAI Realtime and ElevenLabs ConvAI, plus a pluggable pipeline supporting multiple speech-to-text, large language models, and text-to-speech providers. It includes built-in features such as call recording, warm and cold transfers, voicemail detection, dual-tone multi-frequency signaling, and real-time monitoring dashboards. The software is MIT licensed, self-hosted, and provider-agnostic to prevent vendor lock-in.

Patter at a glance

Best for: Software engineer, Support, Sales
Runs on: Web, API, CLI, self-hosted, open source
Pricing: Free under the MIT license; self-hosted with own provider keys.
Released: April 2026
Category: AI audio tool
Website: getpatter.com

Key features

Inbound and outbound call handling with a single handler
Sub-500ms time-to-first-audio latency
OpenAI Realtime and ElevenLabs ConvAI integration
Pluggable pipeline supporting multiple speech and language models
Function calls for database searches, API hits, and human transfers
Barge-in support, call recording, and voicemail detection
Built-in Cloudflare tunnel and terminal test mode
Real-time monitoring dashboard with CSV and JSON export

Use it for

24/7 customer support with human transfer capabilities
Automated appointment reminders and scheduling
Lead qualification and CRM synchronization
Customer surveys and feedback collection at scale

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Cald.ai — It uses advanced LLMs and speech models to deliver human-like, low-latency phone interactions.
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GPT AI Assistant — Connects OpenAI models directly to the LINE mobile messaging app.
Retell AI — It handles phone calls with low-latency responsiveness and high workflow accuracy.
Peon Ping — It notifies users of AI agent status via customizable character sound packs.
VoiceGremlin — Validate AI voice agents with real phone calls and plain English test cases.

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