Engines

End-to-end speech-to-speech runtimes (OpenAI Realtime, ElevenLabs ConvAI).

Engines

An engine is an end-to-end speech-to-speech runtime. Pass an engine instance to phone.agent({ engine }) and Patter wires the audio stream straight through to the provider — no separate STT or TTS is needed.

Patter ships with two engine classes today:

• OpenAIRealtime — OpenAI’s Realtime API
• ElevenLabsConvAI — ElevenLabs Conversational AI

Both classes are imported by name from the package barrel: import { OpenAIRealtime, ElevenLabsConvAI } from "getpatter".

If you need full control over STT, LLM, and TTS independently, use pipeline mode instead and omit engine.

OpenAIRealtime

OpenAI’s Realtime API — the lowest-latency option.

// npx tsx example.ts
import { Patter, Twilio, OpenAIRealtime } from "getpatter";

const phone = new Patter({ carrier: new Twilio(), phoneNumber: "[phone]" });

const agent = phone.agent({
  engine: new OpenAIRealtime({ voice: "alloy" }),           // OPENAI_API_KEY from env
  systemPrompt: "You are a helpful assistant.",
  firstMessage: "Hello!",
});

await phone.serve({ agent });

Parameter	Type	Default	Description
apiKey	string	—	OpenAI API key. Reads from OPENAI_API_KEY when omitted.
voice	string	"alloy"	One of "alloy", "ash", "ballad", "coral", "echo", "sage", "shimmer", "verse".
model	string	"gpt-4o-mini-realtime-preview"	OpenAI Realtime model ID. See supported models.

Supported model identifiers

The model option accepts any OpenAI Realtime model ID. Common values:

Model	Notes
"gpt-realtime-mini"	Default. Lowest latency / lowest cost.
"gpt-realtime"	GA realtime model (Aug 2025).
"gpt-realtime-2"	Most-capable: stronger instruction following, configurable reasoningEffort, 128K context.
"gpt-4o-realtime-preview"	Earlier preview line; ~10x the per-token cost of mini.
"gpt-4o-mini-realtime-preview"	Earlier preview line.

Pricing is auto-resolved per model — see Metrics. For reasoningEffort, transcription model, and the full configuration surface, see OpenAI Realtime — full reference.

ElevenLabsConvAI

ElevenLabs Conversational AI — premium voice quality using a managed agent configured in the ElevenLabs dashboard.

// npx tsx example.ts
import { Patter, Twilio, ElevenLabsConvAI } from "getpatter";

const phone = new Patter({ carrier: new Twilio(), phoneNumber: "[phone]" });

const agent = phone.agent({
  engine: new ElevenLabsConvAI({ agentId: "agent_abc123" }),   // ELEVENLABS_API_KEY from env
  systemPrompt: "You are a warm and friendly concierge.",
});

await phone.serve({ agent });

Parameter	Type	Default	Description
apiKey	string	—	ElevenLabs API key. Reads from ELEVENLABS_API_KEY when omitted.
agentId	string	—	ElevenLabs agent ID (from the ConvAI dashboard). Reads from ELEVENLABS_AGENT_ID when omitted.
voice	string	—	Optional override for the agent’s default voice ID.

What’s Next

LLM

Compare engine mode with pipeline mode.

STT

STT for pipeline mode.

TTS

TTS for pipeline mode.