Mistral

OverviewCopy Anchor Link

• MistralSTTService: streams audio to Mistral's Voxtral realtime transcription over a WebSocket, pushes the text deltas as interim transcriptions, and the final transcript when the user stops speaking.

InstallationCopy Anchor Link

bun add @pipedog/mistral

import { MistralSTTService } from "@pipedog/mistral/stt";

PrerequisitesCopy Anchor Link

• A Mistral account and an API key from Mistral.
• Pass the key as apiKey. The examples read it from MISTRAL_API_KEY.
• A VAD in the pipeline: the end of the user's speech flushes the audio buffer.

MistralSTTServiceCopy Anchor Link

Connects to wss://api.mistral.ai/v1/audio/transcriptions/realtime.

ConfigurationCopy Anchor Link

SettingsCopy Anchor Link

Runtime-updatable settings, passed as settings: new MistralSTTService.Settings({...}) (MistralSTTSettings). Any setting you leave out keeps the default below.

UsageCopy Anchor Link

import { STTUpdateSettingsFrame } from "@pipedog/core/frames/frames";
import { MistralSTTService } from "@pipedog/mistral/stt";

const stt = new MistralSTTService({
  apiKey: process.env.MISTRAL_API_KEY ?? "",
});

Change settings mid-call with an STTUpdateSettingsFrame:

// Queue it on the worker, or push it from a processor upstream of the service.
const update = new STTUpdateSettingsFrame({
  delta: new MistralSTTService.Settings({ model: "voxtral-mini-transcribe-realtime-2602" }),
});

Event handlersCopy Anchor Link

NotesCopy Anchor Link

• targetStreamingDelayMs trades latency for accuracy, when set. It is sent in the session.update message (target_streaming_delay_ms); Mistral accepts 80 to 1200, or 2400, and recommends 480.
• The service waits for session.created before it sends the session settings, as Mistral's SDK does.
• Any settings change reconnects.

Runtime notesCopy Anchor Link

Generated from pipecat.runtimes and pipecat.compat in packages/mistral/package.json: ✅ means the compat smoke test passes on that runtime.

• The WebSocket goes through the core websocketConnect (upstream uses the mistralai SDK's realtime connection). It works on Bun, Node, Deno and Cloudflare Workers.
• The protocol follows Mistral's SDK (mistralai 3.3.0 and @mistralai/mistralai 3.1.0, extra/realtime) and the realtime transcription docs. input_audio.flush and transcription.language are in the SDK but not in the docs.
• Tested against a local fake that follows that protocol, not against Mistral itself.