LiveKit Ultravox Plugin

LiveKit plugin for Ultravox's real-time speech-to-speech AI models, providing seamless integration with the LiveKit Agents framework.

Installation

pip install livekit-plugins-ultravox

Prerequisites

You'll need an API key from Ultravox. Set it as an environment variable:

export ULTRAVOX_API_KEY="your_api_key_here"

Optional: enable debug logs for the plugin (disabled by default):

export LK_ULTRAVOX_DEBUG=true

Basic Usage

Simple Voice Assistant

import asyncio
from livekit.agents import Agent, AgentSession, JobContext, WorkerOptions, cli, inference
from livekit.plugins.ultravox.realtime import RealtimeModel

async def entrypoint(ctx: JobContext):
    await ctx.connect()
    
    session: AgentSession[None] = AgentSession(
        allow_interruptions=True,
        vad=inference.VAD(),
        llm=RealtimeModel(
            model_id="fixie-ai/ultravox",
            voice="Mark",
        ),
    )
    
    await session.start(
        agent=Agent(
            instructions="You are a helpful voice assistant.",
        ),
        room=ctx.room,
    )

if __name__ == "__main__":
    cli.run_app(WorkerOptions(entrypoint_fnc=entrypoint))

Voice Assistant with Tools

from livekit.agents import function_tool, Agent, AgentSession, JobContext, WorkerOptions, cli, inference
from livekit.plugins.ultravox.realtime import RealtimeModel

@function_tool
async def get_weather(location: str) -> str:
    """Get weather information for a location."""
    return f"The weather in {location} is sunny and 72°F"

@function_tool
async def book_appointment(date: str, time: str) -> str:
    """Book an appointment."""
    return f"Appointment booked for {date} at {time}"

async def entrypoint(ctx: JobContext):
    await ctx.connect()
    
    session: AgentSession[None] = AgentSession(
        allow_interruptions=True,
        vad=inference.VAD(),
        llm=RealtimeModel(model_id="fixie-ai/ultravox"),
    )
    
    await session.start(
        agent=Agent(
            instructions="You are a helpful assistant with access to weather and scheduling tools.",
            tools=[get_weather, book_appointment],
        ),
        room=ctx.room,
    )

if __name__ == "__main__":
    cli.run_app(WorkerOptions(entrypoint_fnc=entrypoint))

Configuration Options

Ultravox API (/api/calls) Parameters

RealtimeModel(
    model_id="fixie-ai/ultravox",         # Model to use (warn + pass-through if unknown)
    voice="Mark",                         # Voice to use (warn + pass-through if unknown)
    api_key=None,                          # API key (defaults to env var)
    base_url=None,                         # API base URL (defaults to Ultravox API)
    system_prompt="You are helpful.",      # System prompt
    input_sample_rate=16000,               # Input audio sample rate
    output_sample_rate=24000,              # Output audio sample rate
    client_buffer_size_ms=60,              # Audio buffer size (min 200ms used on WS)
    http_session=None,                     # Custom HTTP session
)

Notes:
- Unknown models/voices: the plugin logs a warning and sends them as-is; the server validates.
- Metrics: the plugin emits a single `metrics_collected` event per generation. To log them,
  add a listener in your app and call the helper:

```python
from livekit.agents import metrics

@session.on("metrics_collected")
def on_metrics_collected(ev):
    metrics.log_metrics(ev.metrics)

Project links

Data verified by PyPI on Aug 20, 2026
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Key dates

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  • Released:
Latest release

Owner

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Credits

Author: LiveKit

GitHub Statistics

Data verified by PyPI on Aug 20, 2026
The GitHub source repository was provided by the project maintainers and verified by PyPI at the time of upload. Stars, forks, and open issues/PRs are derived from that repository and have not been independently verified.

License expression

Apache-2.0
View SPDX License List

Requires

Python >=3.10.0

Tags

ai audio livekit realtime video voice webrtc

Classifiers

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