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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.

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Cartesia TTS

CartesiaTTS is a Patter TTSProvider backed by Cartesia’s /tts/bytes HTTP endpoint. It streams raw PCM_S16LE chunks that drop directly into Patter’s pipeline with no transcoding. Pure aiohttp transport, no vendor SDK required. The default model is sonic-3 (current GA snapshot, ~90 ms TTFB target).
This page covers Cartesia TTS. For Cartesia’s ink-whisper STT see the Cartesia STT page.

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Install

pip install "getpatter[cartesia]"

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Usage

Use the namespaced import (getpatter.tts.cartesia) or the flat alias (getpatter.CartesiaTTS). Both auto-resolve CARTESIA_API_KEY from the environment when api_key= is omitted.
# Namespaced import
from getpatter.tts import cartesia

tts = cartesia.TTS()                                      # reads CARTESIA_API_KEY
tts = cartesia.TTS(voice="f786b574-daa5-4673-aa0c-cbe3e8534c02")  # Katie

# Flat alias (equivalent)
from getpatter import CartesiaTTS

tts = CartesiaTTS(voice="f786b574-daa5-4673-aa0c-cbe3e8534c02")
In an agent: 
import asyncio
from getpatter import Patter, Twilio, DeepgramSTT, CartesiaTTS

phone = Patter(carrier=Twilio(), phone_number="+15550001234")

agent = phone.agent(
    stt=DeepgramSTT(),                                    # DEEPGRAM_API_KEY from env
    tts=CartesiaTTS(voice="f786b574-daa5-4673-aa0c-cbe3e8534c02"),
    system_prompt="You are a helpful assistant.",
)

asyncio.run(phone.serve(agent))

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Models and rates

Cartesia TTS bills per 1,000 characters synthesized. Per-model rates (defaults from getpatter.pricing):
ModelRate / 1k charsNotes
sonic-3 (default)$0.030GA, ~90 ms TTFB. Drop-in compatible with sonic-2 voice IDs.
sonic-2$0.030Previous flagship.
sonic-1 / sonic-english$0.030Legacy English.
sonic-multilingual$0.030Multilingual variant.
Override per-call via Patter(pricing={"cartesia_tts": {"models": {"sonic-3": {"price": ...}}}}).

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Languages

language="en" by default. Sonic-3 supports 30+ languages — pass any Cartesia-supported BCP-47 code ("es", "fr", "de", "it", "pt", "ja", "zh", …). Voice cloning works across all of them — the same voice ID will speak whichever language you target.

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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: 
from getpatter.tts import cartesia

# Twilio: PCM @ 8 kHz directly (skips the 16k→8k resample before mulaw transcode).
tts = cartesia.TTS.for_twilio()

# Telnyx: PCM @ 16 kHz (matches Telnyx's L16/16000 default — zero transcoding).
tts = cartesia.TTS.for_telnyx()

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Options

OptionDefaultNotes
api_keyNoneReads 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.
sample_rate160008000, 16000, 22050, 24000, 44100 Hz.
speedNone"fastest" ... "slowest" or float in [0.6, 2.0].
emotionNoneCartesia emotion preset.
volumeNoneFloat in [0.5, 2.0] (sonic-3 only).
base_urlCartesia APIOverride for proxying.
api_version"2025-04-16"Cartesia API version pin.

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Low-level usage

from getpatter.providers.cartesia_tts import CartesiaTTS

tts = CartesiaTTS(api_key="...", voice="f786b574-...", language="en")
async for chunk in tts.synthesize("Hello from the Patter pipeline."):
    ...
await tts.close()