LemonSlice

LemonSlice provides real-time interactive AI avatars with synchronized lip-sync. Add a self-managed video avatar to your agent that speaks with natural movements and expressions.

Vision Agents uses Stream Video for real-time WebRTC transport by default. External WebRTC transports are supported as well. Most AI providers offer free tiers to get started.

Installation

uv add "vision-agents[lemonslice]"

Quick start

from vision_agents.core import Agent, User
from vision_agents.plugins import cartesia, deepgram, getstream, gemini, lemonslice

agent = Agent(
    edge=getstream.Edge(),
    agent_user=User(name="Assistant", id="agent"),
    instructions="You're a friendly AI assistant.",
    llm=gemini.LLM(),
    tts=cartesia.TTS(),
    stt=deepgram.STT(),
    avatar=lemonslice.Avatar(agent_id="your-avatar-id"),
)

Set the following environment variables:

LEMONSLICE_API_KEY - Your LemonSlice API key
LIVEKIT_URL - Your LiveKit server URL (e.g., wss://your-server.livekit.cloud)
LIVEKIT_API_KEY - Your LiveKit API key
LIVEKIT_API_SECRET - Your LiveKit API secret

Parameters

Name	Type	Default	Description
`agent_id`	`str`	`None`	LemonSlice agent ID (from dashboard)
`agent_image_url`	`str`	`None`	Custom avatar image URL (368x560px) - alternative to agent_id
`agent_prompt`	`str`	`None`	Prompt to influence avatar expressions and movements
`idle_timeout`	`int`	`None`	Seconds before an idle session is closed
`api_key`	`str`	`None`	API key (defaults to `LEMONSLICE_API_KEY` env var)
`base_url`	`str`	`None`	Override the LemonSlice API base URL
`livekit_url`	`str`	`None`	LiveKit server URL (defaults to `LIVEKIT_URL` env var)
`livekit_api_key`	`str`	`None`	LiveKit API key (defaults to `LIVEKIT_API_KEY` env var)
`livekit_api_secret`	`str`	`None`	LiveKit API secret (defaults to `LIVEKIT_API_SECRET` env var)
`width`	`int`	`1280`	Output video width in pixels
`height`	`int`	`720`	Output video height in pixels
`fps`	`int`	`30`	Output video frame rate. Must be `> 0`.
`buffer_seconds`	`float`	`1.0`	Max video buffer depth in seconds ahead of audio playback. Must be `> 0`.

How it works

The avatar works differently depending on your LLM type: With standard LLMs

LLM generates text → TTS converts to audio → Audio sent to LemonSlice → LemonSlice generates synchronized avatar video and audio

With Realtime LLMs

Realtime LLM generates audio → Audio sent to LemonSlice → LemonSlice generates video only (audio from LLM)

# With Gemini Realtime
agent = Agent(
    llm=gemini.Realtime(),
    avatar=lemonslice.Avatar(agent_id="your-avatar-id"),
)

Custom avatar image

Instead of using a pre-configured agent ID, you can provide a custom avatar image:

lemonslice.Avatar(
    agent_image_url="https://example.com/avatar.png",  # 368x560px recommended
    agent_prompt="A friendly customer service representative",
)

Next steps

Build a voice agent

Get started with voice

Build a video agent

Add video processing

Build your own avatar

Subclass the Avatar base class

Overview

Language Models

Realtime

Speech-to-Text

Text-to-Speech

Vision & Video

Avatars

Turn Detection

Infrastructure

Edge Transport

Telephony

Custom Integrations

Installation

Quick start

Parameters

How it works

Custom avatar image

Next steps

Build a voice agent

Build a video agent

Build your own avatar

​Installation

​Quick start

​Parameters

​How it works

​Custom avatar image

​Next steps

Build a voice agent

Build a video agent

Build your own avatar

Installation

Quick start

Parameters

How it works

Custom avatar image

Next steps