Patter is an open-source voice-AI SDK that handles the complexity between an AI agent and the phone network. It provides unified Python and TypeScript APIs that manage the real-time voice agent loop, language model calls, speech-to-text and text-to-speech processing, audio handling, and integrations with telephony carriers like Twilio, Telnyx, and Plivo. Developers can deploy a voice AI agent with a phone number in roughly four lines of code while maintaining full control over the stack.