Channel protocol

Each session owns a single WebSocket. Every message in either direction is wrapped in a ChannelMessage envelope. The envelope shape is stable; the variant payloads evolve with new capabilities.

Envelope

interface ChannelMessage {
  type: ChannelMessageType;
  // 'chat' | 'browser_action' | 'action' | 'audio' | 'status' | 'control' | 'reconnect' | 'error'

  sessionId: string;
  messageId: string;

  /** Redis Stream entry id for replayable streams (interpretation, etc.). */
  streamId?: string;

  timestamp: number;

  /** Routing direction. */
  direction: 'to_browser' | 'to_ari';

  // One of (depending on `type`):
  chat?: ChatPayload;
  browserAction?: BrowserActionPayload;
  action?: ActionPayload;
  actionResult?: ActionResultPayload;
  audio?: AudioPayload;
  status?: StatusPayload;
  control?: ControlPayload;
  reconnect?: ReconnectPayload;
  error?: ErrorPayload;
}

Direction

direction makes routing explicit and is set by the SDK on the way out:

• to_browser — server → SDK (chat, audio, browser-action requests, status).
• to_ari — SDK → server (chat, action results, control, raw send).

Payload variants

type	Field	Purpose
chat	chat	User → AI text, AI → user text. Carries content, responseMode, mediaType.
browser_action	browserAction	SDK → server BOA invocation. Carries messageType, params, metadata.
action	action	Server → SDK browser-action request (the AI wants the browser to do something). Carries name, actionId, params.
actionResult	actionResult	SDK → server result of an action. Carries actionId, success, data?, error?.
audio	audio	Server → SDK TTS audio chunk or assembled buffer.
status	status	Bi-directional status updates (idle, in-progress, response started/ended).
control	control	Session-level controls (response mode, text-chat enable, manual touch).
reconnect	reconnect	Server-initiated reconnect hints.
error	error	Typed error from the server. Mapped to SDK error classes on receive.

Builders

For tests and custom integrations, message builders are exported from the package root:

import {
  createChatMessage,
  createBrowserActionMessage,
  createActionResultMessage,
  createControlMessage,
  // ...
} from '@ki-kombinat/delphi-client-js-sdk';

const msg = createChatMessage({
  sessionId,
  content: 'Hello',
  responseMode: 'voice',
});

session.sendMessage(msg);

The high-level SessionClient methods (sendChat, sendTextChat, sendReadAloud, sendBrowserAction, etc.) all internally use these builders.

Stream replay

Messages that carry a streamId are replayable through Redis Streams. The most common consumer is the interpretation listener, which can pass sinceStreamId to listen() to replay from a specific point. See Interpretation.

Going lower level

SessionClient can be constructed directly when you have a sessionId + wsToken from elsewhere (e.g. a server-issued session forwarded over WebSocket from a separate channel). The orchestrator-level DelphiClient is optional — it adds capability discovery, the session map, the WebRTC stack for voice, and React-friendly aggregated state.