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Sayna Python Example — SIP Webhook + Gemini Voice Agent

A minimal FastAPI service demonstrating the SIP webhook flow: a phone call arrives at Sayna, Sayna forwards a signed webhook here, and a background voice agent (Deepgram STT → Gemini stream → ElevenLabs TTS) holds a conversation with the caller until they hang up.

Architecture

┌──────────┐       ┌──────────┐  signed webhook   ┌──────────────────┐
│  Caller  │──SIP─>│  Sayna   │──────────────────>│  POST /sayna/    │
└──────────┘       │  Server  │                   │     webhook      │
                   │          │                   │                  │
                   │          │<──WebSocket──┐    │   (background)   │
                   └────┬─────┘    audio     │    └────────┬─────────┘
                        │                    │             │
                        ▼                    │             ▼
                   ┌──────────┐              │       ┌──────────────┐
                   │ LiveKit  │              └───────│  SaynaClient │
                   │   room   │                      │  + Gemini    │
                   └──────────┘                      └──────────────┘

Flow:

  1. SIP call hits the Sayna server, which routes it into a LiveKit room.
  2. Sayna posts a signed webhook to POST /sayna/webhook.
  3. The route verifies the HMAC signature with WebhookReceiver and dispatches a background task.
  4. The background VoiceSession opens a WebSocket to Sayna, joins the same LiveKit room as ai-agent, and speaks the greeting.
  5. Each final STT transcript is fed to the VoiceAgent, which streams a Gemini response.
  6. The agent yields one sentence at a time; each sentence is sent to TTS immediately for low-latency speech.
  7. When the caller hangs up, participant_disconnected fires, the session disconnects, and history is cleared.

Prerequisites

  • Python 3.10+
  • A Google AI API key for Gemini
  • Docker (for the local Sayna + LiveKit + LiveKit SIP stack)

Run the Sayna stack

The bundled ../docker-compose.yml brings up Sayna (port 3002), LiveKit (7880), LiveKit SIP (5063), and Redis. From the examples/ directory:

export DEEPGRAM_API_KEY=...
export ELEVENLABS_API_KEY=...
docker compose up

The sayna service is configured with ../sayna.example.yaml, which forwards SIP webhooks to http://localhost:5002/sayna/webhook — the route exposed by this example.

Run the example

cd python-sayna-example
python -m venv .venv
source .venv/bin/activate
pip install -r requirements.txt

cp .env.example .env
# edit .env and set GOOGLE_API_KEY

python main.py

The server listens on http://0.0.0.0:5002 by default. Place a SIP call to the running LiveKit SIP gateway and the agent will answer.

Environment Variables

Variable Required Default Description
GOOGLE_API_KEY yes — Google AI API key for Gemini
SAYNA_URL no http://localhost:3001 Sayna API base URL
SAYNA_API_KEY no secret-key-1234567890 Matches auth.api_secrets[0].secret in sayna.example.yaml
SAYNA_WEBHOOK_SECRET no hook-secret-1234567890 Matches sip.hook_secret in sayna.example.yaml
ELEVENLABS_VOICE_ID no ZIlrSGI4jZqobxRKprJz ElevenLabs voice the agent speaks with
PORT no 5002 FastAPI bind port — must match sayna.example.yaml hooks[].url

Endpoints

Method Path Purpose
GET / Liveness check
POST /sayna/webhook Receives signed SIP webhooks from Sayna

Project Structure

python-sayna-example/
├── main.py            # FastAPI app + the two routes
├── config.py          # Settings (defaults from sayna.example.yaml)
├── prompts.py         # Voice assistant system prompt + fallbacks
├── voice_agent.py     # Gemini streaming + sentence extraction (no Sayna imports)
├── voice_session.py   # SaynaClient lifecycle + STT → agent → TTS glue
├── requirements.txt
├── .env.example
└── .gitignore

voice_agent.py and voice_session.py are intentionally decoupled — the agent module has no Sayna dependency, so it can be exercised against any text-in/text-out harness.

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