Implementation:Openai Openai node Realtime Send Session Update

Knowledge Sources	openai-node OpenAI Realtime API
Domains	Realtime, Configuration
Last Updated	2026-02-15 00:00 GMT

Overview

Concrete pattern for configuring Realtime API sessions via session.update events provided by the openai-node SDK.

Description

The rt.send() method with type: 'session.update' configures the active session. The session payload accepts modalities, instructions, voice, audio formats, turn detection settings, and tool definitions. This is a Pattern Doc — the send() method accepts any RealtimeClientEvent; the session.update usage is a specific pattern.

Usage

Call rt.send({ type: 'session.update', session: {...} }) after connection to configure the session. Listen for session.updated to confirm.

Code Reference

Source Location

• Repository: openai-node
• File: src/realtime/ws.ts (send implementation), src/resources/realtime/realtime.ts (SessionUpdateEvent type)
• Lines: ws.ts:L98-104, realtime.ts:L4446-4465

Signature

// send method (on OpenAIRealtimeWS / OpenAIRealtimeWebSocket)
send(event: RealtimeClientEvent): void;

// SessionUpdateEvent type
interface SessionUpdateEvent {
  type: 'session.update';
  event_id?: string;
  session: {
    modalities?: Array<'text' | 'audio'>;
    instructions?: string;
    voice?: string;  // 'alloy', 'ash', 'coral', 'echo', 'sage', 'shimmer', ...
    input_audio_format?: 'pcm16' | 'g711_ulaw' | 'g711_alaw';
    output_audio_format?: 'pcm16' | 'g711_ulaw' | 'g711_alaw';
    turn_detection?: { type: 'server_vad' | 'semantic_vad'; ... } | null;
    tools?: Array<{ type: 'function'; name: string; description?: string; parameters?: object }>;
  };
}

Import

// No separate import needed — use rt.send() on the connection instance

I/O Contract

Inputs

Name	Type	Required	Description
type	'session.update'	Yes	Event type discriminator
session.modalities	'audio'>	No	Supported modalities
session.instructions	string	No	System prompt for the session
session.voice	string	No	Voice selection for audio output
session.input_audio_format	string	No	Input audio encoding format
session.output_audio_format	string	No	Output audio encoding format
session.turn_detection	null	No	VAD/turn detection configuration
session.tools	Array	No	Tool definitions for function calling

Outputs

Name	Type	Description
(event)	session.updated	Server acknowledgment with updated session config

Usage Examples

import { OpenAIRealtimeWS } from 'openai/realtime/ws';

const rt = await OpenAIRealtimeWS.create(client, {
  model: 'gpt-4o-realtime-preview',
});

// Configure session after connection
rt.on('session.created', () => {
  rt.send({
    type: 'session.update',
    session: {
      modalities: ['text', 'audio'],
      instructions: 'You are a friendly voice assistant.',
      voice: 'shimmer',
      input_audio_format: 'pcm16',
      output_audio_format: 'pcm16',
      turn_detection: { type: 'server_vad' },
    },
  });
});

rt.on('session.updated', (event) => {
  console.log('Session configured:', event.session);
});

Related Pages

Implements Principle

• Principle:Openai_Openai_node_Realtime_Session_Configuration