Cartesia TTS

Overview

Cartesia text-to-speech is available in LiveKit Agents through LiveKit Inference and the Cartesia plugin. With LiveKit Inference, your agent runs on LiveKit's infrastructure to minimize latency. No separate provider API key is required, and usage and rate limits are managed through LiveKit Cloud. Use the plugin instead if you want to manage your own billing and rate limits. Pricing for LiveKit Inference is available on the pricing page.

LiveKit Inference

Use LiveKit Inference to access Cartesia TTS without a separate Cartesia API key.

Usage

To use Cartesia, use the TTS class from the inference module:

from livekit.agents import AgentSession, inference

session = AgentSession(
    tts=inference.TTS(
        model="cartesia/sonic-3", 
        voice="9626c31c-bec5-4cca-baa8-f8ba9e84c8bc", 
        language="en",
        extra_kwargs={
            "speed": 1.5,
            "volume": 1.2,
            "emotion": "excited"
        }
    ),
    # ... tts, stt, vad, turn_handling, etc.
)

import { AgentSession, inference } from '@livekit/agents';

session = new AgentSession({
    tts: new inference.TTS({
        model: "cartesia/sonic-3", 
        voice: "9626c31c-bec5-4cca-baa8-f8ba9e84c8bc", 
        language: "en",
        modelOptions: {
            speed: 1.5,
            volume: 1.2,
            emotion: "excited"
        }
    }),
    // ... tts, stt, vad, turnHandling, etc.
});

Parameters

Model parameters

Pass the following parameters inside extra_kwargs (Python) or modelOptions (Node.js):

Voices

LiveKit Inference supports all of the default "Cartesia Voices" available in the Cartesia API. You can explore the available voices in the Cartesia voice library (free account required), and use the voice by copying its ID into your LiveKit agent session.

The following is a small sample of the Cartesia voices available in LiveKit Inference.

String descriptors

As a shortcut, you can also pass a descriptor with the model ID and voice directly to the tts argument in your AgentSession:

from livekit.agents import AgentSession

session = AgentSession(
    tts="cartesia/sonic-3:9626c31c-bec5-4cca-baa8-f8ba9e84c8bc",
    # ... llm, stt, vad, turn_handling, etc.
)

import { AgentSession } from '@livekit/agents';

session = new AgentSession({
    tts: "cartesia/sonic-3:9626c31c-bec5-4cca-baa8-f8ba9e84c8bc",
    // ... llm, stt, vad, turnHandling, etc.
});

Plugin

LiveKit's plugin support for Cartesia lets you connect directly to Cartesia's TTS API with your own API key.

Installation

Install the plugin from PyPI:

uv add "livekit-agents[cartesia]~=1.4"

pnpm add @livekit/agents-plugin-cartesia@1.x

Authentication

The Cartesia plugin requires a Cartesia API key.

Set CARTESIA_API_KEY in your .env file.

Usage

Use Cartesia TTS within an AgentSession or as a standalone speech generator. For example, you can use this TTS in the Voice AI quickstart.

from livekit.plugins import cartesia

session = AgentSession(
   tts=cartesia.TTS(
      model="sonic-3",
      voice="f786b574-daa5-4673-aa0c-cbe3e8534c02",
   )
   # ... llm, stt, etc.
)

import * as cartesia from '@livekit/agents-plugin-cartesia';

const session = new voice.AgentSession({
    tts: cartesia.TTS(
        model: "sonic-3",
        voice: "f786b574-daa5-4673-aa0c-cbe3e8534c02",
    ),
    // ... llm, stt, etc.
});

Parameters

This section describes some of the available parameters. See the plugin reference links in the Additional resources section for a complete list of all available parameters.

Customizing pronunciation

Cartesia TTS allows you to customize pronunciation using Speech Synthesis Markup Language (SSML). To learn more, see Specify Custom Pronunciations.

Transcription timing

Cartesia TTS supports aligned transcription forwarding, which improves transcription synchronization in your frontend. Set use_tts_aligned_transcript=True in your AgentSession configuration to enable this feature. To learn more, see the docs.

Additional resources

The following resources provide more information about using Cartesia with LiveKit Agents.

Python plugin

ReferenceGitHubPyPI

Node.js plugin

ReferenceGitHubNPM

Cartesia docs

Cartesia TTS docs.

Voice AI quickstart

Get started with LiveKit Agents and Cartesia TTS.

Cartesia STT

Guide to the Cartesia STT plugin with LiveKit Agents.