Backend Mode Server SDK - Spatius

The Server SDK is the required backend side of Backend Mode Integration. It authenticates with your Spatius API Key, opens the Motion Server connection, sends avatar speech audio, and receives encoded audio payloads and motion data payloads.

Responsibilities

Server SDK responsibility	Description
Authenticate	Use the backend-only API Key to create and start an avatar session.
Connect to Motion Server	Own the WebSocket connection to Spatius.
Send avatar speech audio	Send the TTS output or other avatar speech audio to Motion Server. See Audio.
Receive encoded payloads	Receive the encoded audio payloads and motion data payloads your clients will render.
Hand off to transport	Deliver those encoded payloads to clients over your own WebSocket, LiveKit Room, or another transport.

Client apps do not use your API Key. In Backend Mode Integration, your backend owns the Spatius credentials and Motion Server connection.

Next steps

Python Server SDK

Session lifecycle, audio input, callbacks, and egress options.

Go Server SDK

Go backend SDK reference and lifecycle.

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