Native streaming STT (WebSocket)

Opens a WebSocket and emits normalized streaming speech-to-text events. The request must include Upgrade: websocket.

Stream binary audio and use stt.audio.commit, stt.audio.clear, and stt.session.close controls. Server events share a sequenced stt.* envelope. Transcript updates remain separate from a unified flat stt.signal event whose state is started, end_candidate, resumed, or end. Optional turn_scope preserves utterance-versus-turn meaning; it is distinct from transcript-final scope. Only signals explicitly supplied by the selected provider are surfaced.

Use event_format=provider for provider-native passthrough in both directions. Provider-mode server frames are forwarded without signal mapping, timestamp rewriting, deduplication, or router-generated JSON events. This mode requires a direct upstream realtime WebSocket.

audio_format is required and describes the unchanged raw bytes. No resampling, transcoding, or FFmpeg occurs in the streaming path. Portable flat parameters control commits, turn detection, VAD thresholds, partials, timestamps, language detection, keyterms/context, diarization, formatting, and filler words. Unknown bare parameters are rejected. Put provider-native names under provider_options[<name>]; native overrides win except that conflicting encoding/sample-rate/channel declarations return conflicting_audio_format.

Portable input mapping:

Router VAD supplies turn_detection=acoustic only for OpenAI realtime Whisper and Cartesia ink-whisper. Deepgram Flux has no router-VAD path — its client grammar carries no commit frame — so it serves semantic turn detection only and rejects turn_detection=acoustic with unsupported_stt_option.

Each model family advertises only the portable options it can translate to a native parameter; an explicit option outside that set fails before audio with unsupported_stt_option rather than riding along as a silent no-op. Omitted options fall back to the family's own behavior — interim_results, for example, has no global default. Router VAD can create transcript commits but never manufactures provider-originated stt.signal events, and the signals a session may emit are fixed by the capabilities object echoed in stt.session.started.

Authentication failures close the connection with code 4401 or 4403.

The message-level protocol is documented at the realtime WebSocket reference (AsyncAPI spec: /asyncapi.yaml).

Query Parameters

Header Parameters

Response Body

import { readFile } from "node:fs/promises";import WebSocket from "ws";const audioChunk = await readFile("chunk.pcm");const ws = new WebSocket("wss://api.allmodels.io/v1/stt?provider=deepgram&model=deepgram/nova-3&audio_format=pcm_16000&event_format=normalized", {  headers: { Authorization: `Bearer ${process.env.ALLMODELS_API_KEY}` }});ws.on("open", () => {  ws.send(audioChunk);  ws.send(JSON.stringify({ type: "stt.audio.commit" }));});ws.on("message", (data, isBinary) => {  if (isBinary) process.stdout.write(data);  else console.log(JSON.parse(data.toString()));});ws.on("error", console.error);

import asyncioimport base64import jsonimport osfrom pathlib import Pathimport websocketsasync def main():    async with websockets.connect(        "wss://api.allmodels.io/v1/stt?provider=deepgram&model=deepgram/nova-3&audio_format=pcm_16000&event_format=normalized",        additional_headers={"Authorization": f"Bearer {os.environ['ALLMODELS_API_KEY']}"},    ) as socket:        await socket.send(Path("chunk.pcm").read_bytes())        await socket.send(json.dumps({"type": "stt.audio.commit"}))        async for message in socket:            print(message if isinstance(message, str) else f"{len(message)} audio bytes")asyncio.run(main())

curl --http1.1 -i "https://api.allmodels.io/v1/stt?provider=deepgram&model=deepgram/nova-3&audio_format=pcm_16000&event_format=normalized" \  -H "Authorization: Bearer $ALLMODELS_API_KEY" \  -H "Connection: Upgrade" \  -H "Upgrade: websocket" \  -H "Sec-WebSocket-Version: 13" \  -H "Sec-WebSocket-Key: SGVsbG9BbGxNb2RlbHMhIQ=="

{  "error": "invalid_model",  "provider": "soniox",  "model": "bogus",  "supported": [    "stt-rt-v5"  ]}

{  "error": "missing_api_key"}

{  "error": "provider_not_allowed",  "tried": [    "deepgram",    "soniox",    "assemblyai"  ]}

{  "error": "model_not_priced",  "provider": "deepgram",  "model": "flux-general-en"}

{  "error": "websocket_upgrade_required"}

{  "error": "auth_not_initialized"}