ZRT: Zero Runtime Python SDK

Serverless voice AI agents for Python. Write the agent in real Python with your own STT, LLM, and TTS providers. Zero Runtime runs the live speech‑to‑speech pipeline (turn detection, denoising, interruptions) at low latency in the cloud.

You write the agent. We run the runtime. No media servers, no GPUs, no autoscaling.

Install

pip install zrt

Requires Python 3.10+.

Quickstart

Get your auth token from app.zeroruntime.ai.

export ZRT_AUTH_TOKEN=<your-token>
export DEEPGRAM_API_KEY=<key>    # speech-to-text
export GOOGLE_API_KEY=<key>      # LLM (Gemini)
export CARTESIA_API_KEY=<key>    # text-to-speech

# agent.py
from zrt import serve, invoke, Room
from zrt.agents import Agent, Pipeline, function_tool
from zrt.plugins.deepgram import DeepgramSTT
from zrt.plugins.google import GoogleLLM
from zrt.plugins.cartesia import CartesiaTTS

AGENT_ID = "assistant"


class Assistant(Agent):
    def __init__(self):
        super().__init__(
            instructions="You are a friendly voice assistant. Keep replies short.",
            agent_id=AGENT_ID,
            pipeline=Pipeline(
                stt=DeepgramSTT(),
                llm=GoogleLLM(model="gemini-2.5-flash"),
                tts=CartesiaTTS(),
            ),
        )

    async def on_enter(self):
        await self.session.say("Hi! How can I help?")

    @function_tool
    async def get_weather(self, city: str) -> dict:
        """Get the current weather for a city.

        Args:
            city: City name
        """
        return {"city": city, "temp_c": 22}


def on_ready() -> None:
    # Registration confirmed; start a playground session and print a join link.
    info = invoke(AGENT_ID, room=Room(playground=True))
    if info.get("playground_url"):
        print(f"Join the playground: {info['playground_url']}")


if __name__ == "__main__":
    serve(Assistant(), on_ready=on_ready)

python agent.py

serve() registers the agent; once it's ready, on_ready fires invoke() to start a playground session and print a link you can open to talk to it.

Concepts

Add a @function_tool method to your agent and the LLM calls it (with your typed args) whenever it needs to. Methods are auto-registered; for tools defined outside the agent, pass them via tools=[...].

Providers

Mix and match. Swap any stage in a line:

• STT: Deepgram, AssemblyAI, Google, Azure, Sarvam, and more.
• LLM: OpenAI, Google Gemini, Anthropic Claude, Groq, Cerebras, xAI Grok, Sarvam, and more.
• TTS: Cartesia, ElevenLabs, Google, Azure, Deepgram, and more.
• Realtime (speech‑to‑speech): OpenAI Realtime, Gemini Live, and more.
• Turn detection: Namo · VAD: Silero · Denoise: RNNoise

Resources

• Docs: https://docs.zeroruntime.ai/
• Examples: https://github.com/ZeroRuntimeAI/zrt-python-sdk-examples
• Dashboard & tokens: https://app.zeroruntime.ai
• Support: support@zeroruntime.ai

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