Migrating From Deepgram Flux

This guide covers migrating from Deepgram’s Turn-based Audio (Flux) API. Both Cartesia and Deepgram Flux emit turn-based events over a WebSocket, so migrating to Ink is mostly a matter of renaming fields and updating a few connection parameters.

All migration guides

This guide contains both bare API descriptions and SDK code. To install the SDK:

pip install cartesia

npm i @cartesia/cartesia-js

If you’re already using the Cartesia SDK, upgrade to version >=3.2.0

Ink 2 only supports English right now.
We expect to add more languages in the coming months.

Connection

Replace the Deepgram WebSocket URL and auth header with Cartesia’s.

- wss://api.deepgram.com/v2/listen?model=flux-general-en&encoding=linear16&sample_rate=16000
+ wss://api.cartesia.ai/stt/turns/websocket?model=ink-2&encoding=pcm_s16le&sample_rate=16000

- Authorization: Token <DEEPGRAM_API_KEY>
+ Authorization: Bearer <CARTESIA_API_KEY>
+ Cartesia-Version: 2026-03-01

In browsers, WebSockets do not support request headers. Instead, pass the API version as the cartesia_version query param and use a short-lived access token using the access_token query param instead of an API key. Connect to the turn-detection WebSocket with the Cartesia SDK:

import os
from cartesia import AsyncCartesia

client = AsyncCartesia(api_key=os.getenv("CARTESIA_API_KEY"))

async with client.stt.auto_finalize.websocket(
    model="ink-2", encoding="pcm_s16le", sample_rate=16000
) as connection:
    ...

import os
from cartesia import Cartesia

client = Cartesia(api_key=os.getenv("CARTESIA_API_KEY"))

with client.stt.auto_finalize.websocket(
    model="ink-2", encoding="pcm_s16le", sample_rate=16000
) as connection:
    ...

import Cartesia from "@cartesia/cartesia-js";

const client = new Cartesia({ apiKey: process.env.CARTESIA_API_KEY });

const connection = client.stt.autoFinalize.websocket({
  model: "ink-2",
  encoding: "pcm_s16le",
  sample_rate: 16000,
});

// Server-side: Generate access-tokens using your API key
import Cartesia from '@cartesia/cartesia-js';

const client = new Cartesia({ apiKey: process.env.CARTESIA_API_KEY });

export async function GET() {
  const { token } = await client.accessToken.create({
    grants: { stt: true, tts: false, agent: false },
    // How long the token lasts in seconds
    // Allowed values: 0–3600
    expires_in: 3600,
  });
  return Response.json({ token });
}


// Client-side
// 1. Fetch an access token from your server
// 2. Connect to Cartesia via WebSocket
import Cartesia from "@cartesia/cartesia-js";

async function getToken(): Promise<string> {
  const res = await fetch('/replace-with-your-server');
  const { token } = await res.json();
  return token;
}
const audioContext = new AudioContext();

const client = new Cartesia({ token: await getToken() });

const connection = client.stt.autoFinalize.websocket({
  model: "ink-2",
  encoding: "pcm_f32le",
  sample_rate: audioContext.sampleRate,
});

Query parameters

Deepgram Flux	Cartesia Ink	Notes
`model=flux-general-en` required	`model=ink-2` required	See STT Models for all options.
`encoding=linear16`	`encoding=pcm_s16le` required	See encoding for all options.
`sample_rate`	`sample_rate` required	No change.
`language_hint`	—	Only English is supported right now. Multi-lingual support is coming soon!
—	`cartesia_version=2026-03-01` required	See API Conventions for details.
`eager_eot_threshold`, `eot_threshold`, `eot_timeout_ms`	—	Turn detection is controlled by the model. Configuration is coming soon!
`keyterm`	—	Coming soon!
`mip_opt_out`	—	Controlled by your organization.

encoding

Deepgram	Cartesia
`linear16`	`pcm_s16le`
`linear32`	`pcm_s32le`
`mulaw`	`pcm_mulaw`
`alaw`	`pcm_alaw`
Not supported	`pcm_f16le`
Not supported	`pcm_f32le`
`opus`	Not supported
`ogg-opus`	Not supported

Sending audio

Both APIs accept raw PCM audio as binary WebSocket frames in the same way.

Cartesia does not support these encodings: opus, ogg-opus

To close the session, send a JSON encoded WebSocket text frame:

- { "type": "CloseStream" }
+ { "type": "close" }

Cartesia has no equivalent of Deepgram’s Configure control message since there’s no need to configure end-of-turn.

# Equivalent to 
# deepgram_connection.send_media(audio_chunk)
await connection.send_raw(audio_chunk)

# Equivalent to
# deepgram_connection.send_close_stream()
await connection.send({"type": "close"})

# Equivalent to 
# deepgram_connection.send_media(audio_chunk)
connection.send_raw(audio_chunk)

# Equivalent to
# deepgram_connection.send_close_stream()
connection.send({"type": "close"})

// Equivalent to deepgramConnection.sendMedia(audioChunk)
// @param {ArrayBufferLike} audioChunk - Note: Blob is not accepted
connection.sendRaw(audioChunk);

// Equivalent to
// deepgramConnection.sendCloseStream({ type: "CloseStream" })
connection.send({ type: "close" });

Event mapping

Deepgram `type`	Cartesia `type`
`Connected`	`connected`
`Error`	`error`
`TurnInfo`	See below

Deepgram wraps all turn events in a single TurnInfo message with an event discriminator. Cartesia emits one message type per event, with the type on the top-level type field.

Deepgram `TurnInfo.event`	Cartesia `type`	Carries `transcript`?
`StartOfTurn`	`turn.start`	No (Deepgram: yes)
`Update`	`turn.update`	Yes
`EagerEndOfTurn`	`turn.eager_end`	Yes
`TurnResumed`	`turn.resume`	No (Deepgram: yes)
`EndOfTurn`	`turn.end`	Yes

A Deepgram TurnInfo message:

{
  "type": "TurnInfo",
  "event": "EndOfTurn",
  "turn_index": 0,
  "transcript": "Hi I need to cancel my subscription please.",
  "words": [...],
  "end_of_turn_confidence": 0.7,
  "audio_window_start": 0.0,
  "audio_window_end": 1.7
}

Becomes a Cartesia turn.* event:

{
  "type": "turn.end",
  "transcript": "Hi I need to cancel my subscription please.",
  "request_id": "2ff8af53-4d38-479d-8287-58940f01c701"
}

Like Deepgram, the transcript is cumulative within a turn.

Event handler

The branching structure of your handler is unchanged — just the message shape.

  ws.onmessage = (message) => {
    const data = JSON.parse(message.data);
-   if (data.type !== "TurnInfo") return;
-   switch (data.event) {
-     case "StartOfTurn":    onTurnStart(); break;
-     case "Update":         onTranscriptUpdate(data.transcript); break;
-     case "EagerEndOfTurn": prepareReply(data.transcript); break;
-     case "TurnResumed":    cancelReply(); break;
-     case "EndOfTurn":      finalizeReply(data.transcript); break;
-   }
+   switch (data.type) {
+     case "turn.start":     onTurnStart(); break;
+     case "turn.update":    onTranscriptUpdate(data.transcript); break;
+     case "turn.eager_end": prepareReply(data.transcript); break;
+     case "turn.resume":    cancelReply(); break;
+     case "turn.end":       finalizeReply(data.transcript); break;
+   }
  };

import asyncio
from cartesia.types.stt import STTAutoFinalizeWebsocketResponse

def on_message(message: STTAutoFinalizeWebsocketResponse) -> None:
    if message.type == "turn.start":
        print("StartOfTurn")
    elif message.type == "turn.update":
        print(f"Update: {message.transcript}")
    elif message.type == "turn.eager_end":
        print(f"EagerEndOfTurn: {message.transcript}")
    elif message.type == "turn.resume":
        print("TurnResumed")
    elif message.type == "turn.end":
        print(f"EndOfTurn: {message.transcript}")
    elif message.type == "error":
        print(f"Error: {message.message}")

# Equivalent to
# deepgram_connection.on(EventType.MESSAGE, on_message)
connection.on("event", on_message)

# Equivalent to
# asyncio.create_task(deepgram_connection.start_listening())
recv_task = asyncio.create_task(connection.dispatch_events())

import threading
from cartesia.types.stt import STTAutoFinalizeWebsocketResponse

def on_message(message: STTAutoFinalizeWebsocketResponse) -> None:
    if message.type == "turn.start":
        print("StartOfTurn")
    elif message.type == "turn.update":
        print(f"Update: {message.transcript}")
    elif message.type == "turn.eager_end":
        print(f"EagerEndOfTurn: {message.transcript}")
    elif message.type == "turn.resume":
        print("TurnResumed")
    elif message.type == "turn.end":
        print(f"EndOfTurn: {message.transcript}")
    elif message.type == "error":
        print(f"Error: {message.message}")

# Equivalent to
# deepgram_connection.on(EventType.MESSAGE, on_message)
connection.on("event", on_message)

# Equivalent to
# threading.Thread(target=deepgram_connection.start_listening, daemon=True).start()
threading.Thread(target=connection.dispatch_events, daemon=True).start()

import Cartesia from '@cartesia/cartesia-js';

// Equivalent to
// deepgramConnection.on("message", (message) => { ... });
connection.on("event", (message: Cartesia.STT.AutoFinalize.STTAutoFinalizeWebsocketResponse) => {
  switch (message.type) {
    case "turn.start":
      console.log("StartOfTurn");
      break;
    case "turn.update":
      console.log(`Update: ${message.transcript}`);
      break;
    case "turn.eager_end":
      console.log(`EagerEndOfTurn: ${message.transcript}`);
      break;
    case "turn.resume":
      console.log("TurnResumed");
      break;
    case "turn.end":
      console.log(`EndOfTurn: ${message.transcript}`);
      break;
  }
});

// Equivalent to
// deepgramConnection.on("error", (error) => { ... });
connection.on("error", (error) => {
  if (error.error) {
    // Server sent error (may be a bad request or internal server error)
    console.error(`Server sent an error: ${error.error.message}`);
  } else {
    // Client error
    console.error(`Client had an error: ${error.message}`);
  }
});

Example Server Messages

Flux’s transcripts are joined with spaces. Ink’s are not.

Deepgram Flux	Cartesia Realtime STT (Auto)
StartOfTurn	turn.start
Update `"Flux's transcripts"`	turn.update `"Flux's transcripts"`
EagerEndOfTurn `"Flux's transcripts"`	turn.eager_end `"Flux's transcripts"`
TurnResumed	turn.resume
Update `"Flux's transcripts are joined with spaces."`	turn.update `"Flux's transcripts are joined with spaces."`
EagerEndOfTurn `"Flux's transcripts are joined with spaces."`	turn.eager_end `"Flux's transcripts are joined with spaces."`
EndOfTurn `"Flux's transcripts are joined with spaces."`	turn.end `"Flux's transcripts are joined with spaces."`
StartOfTurn	turn.start
Update `"Ink's are not."`	turn.update `" Ink's are not."`
EagerEndOfTurn `"Ink's are not."`	turn.eager_end `" Ink's are not."`
EndOfTurn `"Ink's are not."`	turn.end `" Ink's are not."`

Migrating From Deepgram Flux

All migration guides

Connection

Query parameters

Sending audio

Event mapping

Event handler

Example Server Messages

References

API Reference

Full Code Example

All migration guides

​Connection

​Query parameters

​Sending audio

​Event mapping

​Event handler

​Example Server Messages

​References

API Reference

Full Code Example

Connection

Query parameters

Sending audio

Event mapping

Event handler

Example Server Messages

References