TrueFoundry + Cartesia

Last verified: 2026-06-10

Overview

TrueFoundry AI Gateway is the proxy layer that sits between your applications and the LLM providers and MCP Servers. It provides a unified OpenAI-compatible API to route requests across 1000+ LLMs while handling observability, governance, and access control at the gateway level. Cartesia is available as a first-party provider in TrueFoundry’s AI Gateway for TTS and STT. Register Cartesia models in the gateway, then call them with the Cartesia Python SDK and your TrueFoundry API key.

Prerequisites

Sign up for a TrueFoundry account
Get a TrueFoundry API key (TFY_API_KEY) from making requests via the gateway
Get a Cartesia API key from Cartesia keys
Python 3.10+

Follow these steps to connect Cartesia in AI Gateway:

Navigate to Cartesia Models in AI Gateway

In the TrueFoundry dashboard, go to AI Gateway → Models and select Cartesia. See TrueFoundry Cartesia setup for the full navigation path.

Add Cartesia Account Details

Click Add Cartesia Account. Enter a unique account name and your Cartesia API Key. Optionally add collaborators so other users or teams can use this account — see gateway access control.

Cartesia account configuration form with fields for API key and collaborators

Add Models

Click + Add Model and set Display name, Model ID, and Model type.

Add Cartesia model form with display name, model ID, and model type

For Cartesia, Model ID and Display name must be identical.

Installation

pip install cartesia httpx

Quick start

TTS

Point AsyncCartesia at your gateway TTS route. Replace GATEWAY_BASE_URL, cartesiaProviderAccountName, TFY_API_KEY, and model_id with values from your TrueFoundry workspace.

import asyncio
import httpx
from cartesia import AsyncCartesia

TFY_API_KEY = "your-tfy-api-key"
BASE_URL = "{GATEWAY_BASE_URL}/tts/{cartesiaProviderAccountName}"
OUTPUT_FILE = "/path/to/output.wav"

client = AsyncCartesia(
    api_key="dummy",  # gateway auth uses x-tfy-api-key, not Cartesia api_key
    base_url=BASE_URL,
    http_client=httpx.AsyncClient(
        headers={"x-tfy-api-key": TFY_API_KEY},
    ),
)


async def main():
    response = await client.tts.generate(
        model_id="sonic-3.5",  # must match a model ID registered in AI Gateway
        transcript="Welcome to Cartesia Sonic!",
        voice={"mode": "id", "id": "a0e99841-438c-4a64-b679-ae501e7d6091"},
        language="en",
        output_format={
            "container": "wav",
            "sample_rate": 44100,
            "encoding": "pcm_s16le",
        },
    )
    with open(OUTPUT_FILE, "wb") as f:
        f.write(await response.read())
    print(OUTPUT_FILE)


asyncio.run(main())

Parameter	Type	Description
`GATEWAY_BASE_URL`	`string`	Gateway base URL from TrueFoundry (no trailing slash)
`cartesiaProviderAccountName`	`string`	Cartesia provider account name under AI Gateway → Models → Cartesia
`TFY_API_KEY`	`string`	TrueFoundry API key sent as the `x-tfy-api-key` header
`model_id`	`string`	Cartesia model ID; must match Model ID and Display name in the gateway

STT

Register an STT model type in the gateway, then point AsyncCartesia at your gateway STT route. Replace GATEWAY_BASE_URL, cartesiaProviderAccountName, TFY_API_KEY, and model with values from your TrueFoundry workspace.

import asyncio
import httpx
from cartesia import AsyncCartesia

TFY_API_KEY = "your-tfy-api-key"
BASE_URL = "{GATEWAY_BASE_URL}/stt/{cartesiaProviderAccountName}"
AUDIO_FILE = "/path/to/audio.wav"

client = AsyncCartesia(
    api_key="dummy",  # gateway auth uses x-tfy-api-key, not Cartesia api_key
    base_url=BASE_URL,
    http_client=httpx.AsyncClient(
        headers={"x-tfy-api-key": TFY_API_KEY},
    ),
)


async def main():
    with open(AUDIO_FILE, "rb") as f:
        response = await client.stt.transcribe(
            file=f,
            model="ink-2",  # must match a model ID registered in AI Gateway
            language="en",
        )
    print(response.text)


asyncio.run(main())

Parameter	Type	Description
`GATEWAY_BASE_URL`	`string`	Gateway base URL from TrueFoundry (no trailing slash)
`cartesiaProviderAccountName`	`string`	Cartesia provider account name under AI Gateway → Models → Cartesia
`TFY_API_KEY`	`string`	TrueFoundry API key sent as the `x-tfy-api-key` header
`model`	`string`	Cartesia STT model ID; must match Model ID and Display name in the gateway
`AUDIO_FILE`	`string`	Path to a local audio file (WAV, MP3, and other common formats)

After models are registered, open any Cartesia model in the TrueFoundry dashboard and use Code Snippet or Try in Playground to test TTS and STT requests before wiring them into your app.

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