> ## Documentation Index
> Fetch the complete documentation index at: https://docs.getpatter.com/llms.txt
> Use this file to discover all available pages before exploring further.

# Cartesia TTS

> Sonic-1, Sonic-2, and Sonic-3 voice synthesis via Cartesia's HTTP bytes endpoint.

# Cartesia TTS

`CartesiaTTS` is a Patter `TTSProvider` backed by Cartesia's [`/tts/bytes` HTTP endpoint](https://docs.cartesia.ai/api-reference/tts/bytes). It streams raw PCM\_S16LE chunks that drop directly into Patter's pipeline with no transcoding. Uses the platform `fetch` — no vendor SDK required, works on Node 18+. The default model is `sonic-3` (current GA snapshot, \~90 ms TTFB target).

<Note>
  This page covers Cartesia **TTS**. For Cartesia's `ink-whisper` STT see
  [the Cartesia STT page](/typescript-sdk/providers/cartesia).
</Note>

## Install

```bash theme={null}
npm install getpatter
```

## Usage

<Note>
  Use the namespaced import (`getpatter/tts/cartesia`) or the flat
  re-export (`CartesiaTTS`). Both auto-resolve `CARTESIA_API_KEY` from the
  environment when `apiKey` is omitted.
</Note>

<CodeGroup>
  ```typescript TypeScript theme={null}
  // Namespaced import
  import * as cartesia from "getpatter/tts/cartesia";

  const tts = new cartesia.TTS();                                  // reads CARTESIA_API_KEY
  const tts2 = new cartesia.TTS({ voice: "f786b574-daa5-4673-aa0c-cbe3e8534c02" });

  // Flat alias (equivalent)
  import { CartesiaTTS } from "getpatter";

  const tts3 = new CartesiaTTS({ voice: "f786b574-daa5-4673-aa0c-cbe3e8534c02" });
  ```

  ```python Python theme={null}
  # See python-sdk/providers/cartesia-tts for the Python twin.
  ```
</CodeGroup>

In an agent:

```typescript theme={null}
// npx tsx example.ts
import { Patter, Twilio, DeepgramSTT, CartesiaTTS } from "getpatter";

const phone = new Patter({ carrier: new Twilio(), phoneNumber: "+15550001234" });

const agent = phone.agent({
  stt: new DeepgramSTT(),                             // DEEPGRAM_API_KEY from env
  tts: new CartesiaTTS({ voice: "f786b574-daa5-4673-aa0c-cbe3e8534c02" }),
  systemPrompt: "You are a helpful assistant.",
});

await phone.serve({ agent });
```

## Models and rates

Cartesia TTS bills per 1,000 characters synthesized. Per-model rates (defaults from `getpatter/pricing`):

| Model                       | Rate / 1k chars | Notes                                                        |
| --------------------------- | --------------- | ------------------------------------------------------------ |
| `sonic-3` (default)         | \$0.030         | GA, \~90 ms TTFB. Drop-in compatible with sonic-2 voice IDs. |
| `sonic-2`                   | \$0.030         | Previous flagship.                                           |
| `sonic-1` / `sonic-english` | \$0.030         | Legacy English.                                              |
| `sonic-multilingual`        | \$0.030         | Multilingual variant.                                        |

Override via `new Patter({ pricing: { cartesia_tts: { models: { "sonic-3": { price: ... } } } } })`.

## Languages

`language: "en"` by default. Sonic-3 supports 30+ languages — pass any [Cartesia-supported BCP-47 code](https://docs.cartesia.ai/api-reference/tts/text-to-speech) (`"es"`, `"fr"`, `"de"`, `"it"`, `"pt"`, `"ja"`, `"zh"`, …). Voice cloning works across all of them — the same voice ID will speak whichever language you target.

## Telephony optimization

Use the carrier-aware factories so audio reaches Patter's telephony adapter at the carrier's native sample rate, skipping a resample step:

```typescript theme={null}
import { CartesiaTTS } from "getpatter";

// Twilio: PCM @ 8 kHz directly (skips the 16k→8k resample before mulaw transcode).
const twilioTts = CartesiaTTS.forTwilio();

// Telnyx: PCM @ 16 kHz (matches Telnyx's L16/16000 default — zero transcoding).
const telnyxTts = CartesiaTTS.forTelnyx();
```

## Options

| Option       | Default                  | Notes                                               |
| ------------ | ------------------------ | --------------------------------------------------- |
| `apiKey`     | —                        | Reads from `CARTESIA_API_KEY` when omitted.         |
| `model`      | `"sonic-3"`              | Any Cartesia TTS model id.                          |
| `voice`      | `"f786b574-..."` (Katie) | Cartesia voice id.                                  |
| `language`   | `"en"`                   | BCP-47 code.                                        |
| `sampleRate` | `16000`                  | 8000, 16000, 22050, 24000, 44100 Hz.                |
| `speed`      | —                        | `"fastest" ... "slowest"` or float in `[0.6, 2.0]`. |
| `emotion`    | —                        | Cartesia emotion preset.                            |
| `volume`     | —                        | Float in `[0.5, 2.0]` (sonic-3 only).               |
| `baseUrl`    | Cartesia API             | Override for proxying.                              |
| `apiVersion` | `"2025-04-16"`           | Cartesia API version pin.                           |