Spline offers an AI Voice Assistant feature that lets designers embed a real-time voice-enabled AI character into their 3D scenes, powered by the user's own OpenAI API key. End users of the published 3D experience can then speak to the AI and receive spoken responses.

The feature integrates with OpenAI's Realtime API to deliver low-latency conversational voice responses within a Spline scene. Designers configure the AI's personality, instructions, and trigger events inside the Spline editor; when the published scene is loaded by end users, microphone access is requested and voice interaction begins. The AI's audio spectrum output can be linked to variables that animate 3D objects in the scene. Users must supply their own paid OpenAI developer API key to use this feature.