# Hold Slayer 🔥

**An AI-powered telephony gateway that calls companies, navigates IVR menus, waits on hold, and transfers you when a human picks up.**

You give it a phone number and an intent ("dispute a charge on my December statement"). It dials the number through your SIP trunk, navigates the phone tree, sits through the hold music, and rings your desk phone the instant a live person answers. You never hear Vivaldi again.

> [!CAUTION]
> **Emergency calling — 911**
> Hold Slayer passes `911` and `9911` directly to the PSTN trunk.
> **Your SIP trunk provider must support E911 on your DID and have your
> correct registered location on file before this system is put into
> service.** VoIP emergency calls are location-dependent — verify
> with your provider. Do not rely on this system as your only means
> of reaching emergency services.

## Architecture

```
┌─────────────────────────────────────────────────────────────────┐
│                        FastAPI Server                           │
│                                                                 │
│  ┌──────────┐  ┌──────────┐  ┌───────────┐  ┌──────────────┐  │
│  │ REST API │  │WebSocket │  │MCP Server │  │  Dashboard   │  │
│  │ /api/*   │  │ /ws/*    │  │ (SSE)     │  │  /dashboard  │  │
│  └────┬─────┘  └────┬─────┘  └─────┬─────┘  └──────────────┘  │
│       │              │              │                            │
│  ┌────┴──────────────┴──────────────┴────┐                     │
│  │             Event Bus                  │                     │
│  │   (asyncio Queue pub/sub per client)   │                     │
│  └────┬──────────────┬──────────────┬────┘                     │
│       │              │              │                            │
│  ┌────┴─────┐  ┌─────┴─────┐  ┌────┴──────────┐               │
│  │   Call   │  │   Hold    │  │   Services    │               │
│  │ Manager  │  │  Slayer   │  │ (LLM, STT,   │               │
│  │          │  │           │  │  Recording,   │               │
│  │          │  │           │  │  Analytics,   │               │
│  │          │  │           │  │  Notify)      │               │
│  └────┬─────┘  └─────┬─────┘  └──────────────┘               │
│       │              │                                          │
│  ┌────┴──────────────┴───────────────────┐                     │
│  │         Sippy B2BUA Engine            │                     │
│  │  (SIP calls, DTMF, conference bridge) │                     │
│  └────┬──────────────────────────────────┘                     │
│       │                                                         │
└───────┼─────────────────────────────────────────────────────────┘
        │
   ┌────┴────┐
   │SIP Trunk│ ──→ PSTN
   └─────────┘
```

## What's Implemented

### Core Engine
- **Sippy B2BUA Engine** (`core/sippy_engine.py`) — SIP call control, DTMF, bridging, conference, trunk registration
- **PJSUA2 Media Pipeline** (`core/media_pipeline.py`) — Audio routing, recording ports, conference bridge, WAV playback
- **Call Manager** (`core/call_manager.py`) — Active call state tracking, lifecycle management
- **Event Bus** (`core/event_bus.py`) — Async pub/sub with per-subscriber queues, type filtering, history

### Hold Slayer
- **IVR Navigation** (`services/hold_slayer.py`) — Follows stored call flows step-by-step through phone menus
- **Audio Classifier** (`services/audio_classifier.py`) — Real-time waveform analysis: silence, tones, DTMF, music, speech detection
- **Call Flow Learner** (`services/call_flow_learner.py`) — Builds reusable call flows from exploration data, merges new discoveries
- **LLM Fallback** — When a LISTEN step has no hardcoded DTMF, the LLM analyzes the transcript and picks the right menu option

### Intelligence Layer
- **LLM Client** (`services/llm_client.py`) — OpenAI-compatible API client (Ollama, vLLM, LM Studio, OpenAI) with JSON parsing, retry, stats
- **Transcription** (`services/transcription.py`) — Speaches/Whisper STT integration for live call transcription
- **Recording** (`services/recording.py`) — WAV recording with date-organized storage, dual-channel support
- **Call Analytics** (`services/call_analytics.py`) — Hold time stats, success rates, per-company patterns, time-of-day trends
- **Notifications** (`services/notification.py`) — WebSocket + SMS alerts for human detection, call failures, hold status

### API Surface
- **REST API** — Call management, device registration, call flow CRUD, service configuration
- **WebSocket** — Real-time call events, transcripts, classification updates
- **MCP Server** — 10 tools for AI assistant integration (make calls, send DTMF, get transcripts, manage flows)

### Data Models
- **Call** — Active call state with classification history, transcript chunks, hold time tracking
- **Call Flow** — Stored IVR trees with steps (DTMF, LISTEN, HOLD, TRANSFER, SPEAK)
- **Events** — 20+ typed events (call lifecycle, hold slayer, audio, device, system)
- **Device** — SIP phone/softphone registration and routing
- **Contact** — Phone number management with routing preferences

## Project Structure

```
hold-slayer/
├── main.py                      # FastAPI app + lifespan (service wiring)
├── config.py                    # Pydantic settings from .env
├── core/
│   ├── gateway.py               # Top-level gateway orchestrator
│   ├── sippy_engine.py          # Sippy B2BUA SIP engine
│   ├── media_pipeline.py        # PJSUA2 audio routing
│   ├── call_manager.py          # Active call state management
│   └── event_bus.py             # Async pub/sub event bus
├── services/
│   ├── hold_slayer.py           # IVR navigation + hold detection
│   ├── audio_classifier.py      # Waveform analysis (music/speech/DTMF)
│   ├── call_flow_learner.py     # Auto-learns IVR trees from calls
│   ├── llm_client.py            # OpenAI-compatible LLM client
│   ├── transcription.py         # Speaches/Whisper STT
│   ├── recording.py             # Call recording management
│   ├── call_analytics.py        # Call metrics and insights
│   └── notification.py          # WebSocket + SMS notifications
├── api/
│   ├── calls.py                 # Call management endpoints
│   ├── call_flows.py            # Call flow CRUD
│   ├── devices.py               # Device registration
│   ├── websocket.py             # Real-time event stream
│   └── deps.py                  # FastAPI dependency injection
├── mcp_server/
│   └── server.py                # MCP tools + resources (10 tools)
├── models/
│   ├── call.py                  # Call state models
│   ├── call_flow.py             # IVR tree models
│   ├── events.py                # Event type definitions
│   ├── device.py                # Device models
│   └── contact.py               # Contact models
├── db/
│   └── database.py              # SQLAlchemy async (PostgreSQL/SQLite)
└── tests/
    ├── test_audio_classifier.py # 18 tests — waveform analysis
    ├── test_call_flows.py       # 10 tests — call flow models
    ├── test_hold_slayer.py      # 20 tests — IVR nav, EventBus, CallManager
    └── test_services.py         # 27 tests — LLM, notifications, recording,
                                 #             analytics, learner, EventBus
```

## Quick Start

### 1. Install

```bash
python -m venv .venv
source .venv/bin/activate
pip install -e ".[dev]"
```

### 2. Configure

```bash
cp .env.example .env
# Edit .env with your SIP trunk credentials, LLM endpoint, etc.
```

### 3. Run

```bash
uvicorn main:app --host 0.0.0.0 --port 8100
```

### 4. Test

```bash
pytest tests/ -v
```

## Usage

### REST API

**Launch Hold Slayer on a number:**

```bash
curl -X POST http://localhost:8000/api/calls/hold-slayer \
  -H "Content-Type: application/json" \
  -d '{
    "number": "+18005551234",
    "intent": "dispute Amazon charge from December 15th",
    "call_flow_id": "chase_bank_main",
    "transfer_to": "sip_phone"
  }'
```

**Check call status:**

```bash
curl http://localhost:8000/api/calls/call_abc123
```

### WebSocket — Real-Time Events

```javascript
const ws = new WebSocket("ws://localhost:8000/ws/events");
ws.onmessage = (msg) => {
  const event = JSON.parse(msg.data);
  // event.type: "human_detected", "hold_detected", "ivr_step", etc.
  // event.call_id: which call this is about
  // event.data: type-specific payload
};
```

### MCP — AI Assistant Integration

The MCP server exposes 10 tools that any MCP-compatible assistant can use:

| Tool | Description |
|------|-------------|
| `make_call` | Dial a number through the SIP trunk |
| `end_call` | Hang up an active call |
| `send_dtmf` | Send touch-tone digits to navigate menus |
| `get_call_status` | Check current state of a call |
| `get_call_transcript` | Get live transcript of a call |
| `get_call_recording` | Get recording metadata and file path |
| `list_active_calls` | List all calls in progress |
| `get_call_summary` | Analytics summary (hold times, success rates) |
| `search_call_history` | Search past calls by number or company |
| `learn_call_flow` | Build a reusable call flow from exploration data |

## How It Works

1. **You request a call** — via REST API, MCP tool, or dashboard
2. **Gateway dials out** — Sippy B2BUA places the call through your SIP trunk
3. **Audio classifier listens** — Real-time waveform analysis detects IVR prompts, hold music, ringing, silence, and live speech
4. **Transcription runs** — Speaches/Whisper converts audio to text in real-time
5. **IVR navigator decides** — If a stored call flow exists, it follows the steps. If not, the LLM analyzes the transcript and picks the right menu option
6. **Hold detection** — When hold music is detected, the system waits patiently and monitors for transitions
7. **Human detection** — The classifier detects the transition from music/silence to live speech
8. **Transfer** — Your desk phone rings. Pick up and you're talking to the agent. Zero hold time.

## Configuration

All configuration is via environment variables (see `.env.example`):

| Variable | Description | Default |
|----------|-------------|---------|
| `SIP_TRUNK_HOST` | Your SIP provider hostname | — |
| `SIP_TRUNK_USERNAME` | SIP auth username | — |
| `SIP_TRUNK_PASSWORD` | SIP auth password | — |
| `SIP_TRUNK_DID` | Your phone number (E.164) | — |
| `GATEWAY_SIP_PORT` | Port for device registration | `5080` |
| `SPEACHES_URL` | Speaches/Whisper STT endpoint | `http://localhost:22070` |
| `LLM_BASE_URL` | OpenAI-compatible LLM endpoint | `http://localhost:11434/v1` |
| `LLM_MODEL` | Model name for IVR analysis | `llama3` |
| `DATABASE_URL` | PostgreSQL or SQLite connection | SQLite fallback |

## Tech Stack

- **Python 3.13** + **asyncio** — Single-process async architecture
- **FastAPI** — REST API + WebSocket server
- **Sippy B2BUA** — SIP call control and DTMF
- **PJSUA2** — Media pipeline, conference bridge, recording
- **Speaches** (Whisper) — Speech-to-text
- **Ollama / vLLM / OpenAI** — LLM for IVR menu analysis
- **SQLAlchemy** — Async database (PostgreSQL or SQLite)
- **MCP (Model Context Protocol)** — AI assistant integration

## Documentation

Full documentation is in [`/docs`](docs/README.md):

- [Architecture](docs/architecture.md) — System design, data flow, threading model
- [Core Engine](docs/core-engine.md) — SIP engine, media pipeline, call manager, event bus
- [Hold Slayer Service](docs/hold-slayer-service.md) — IVR navigation, hold detection, human detection
- [Audio Classifier](docs/audio-classifier.md) — Waveform analysis, feature extraction, classification
- [Services](docs/services.md) — LLM client, transcription, recording, analytics, notifications
- [Call Flows](docs/call-flows.md) — Call flow model, step types, auto-learner
- [API Reference](docs/api-reference.md) — REST endpoints, WebSocket, request/response schemas
- [MCP Server](docs/mcp-server.md) — MCP tools and resources for AI assistants
- [Configuration](docs/configuration.md) — All environment variables, deployment options
- [Development](docs/development.md) — Setup, testing, contributing

## Build Phases

### Phase 1: Core Engine ✅

- [x] Extract EventBus to dedicated module with typed filtering
- [x] Implement Sippy B2BUA SIP engine (signaling, DTMF, bridging)
- [x] Implement PJSUA2 media pipeline (conference bridge, audio tapping, recording)
- [x] Call manager with active call state tracking
- [x] Gateway orchestrator wiring all components

### Phase 2: Intelligence Layer ✅

- [x] LLM client (OpenAI-compatible — Ollama, vLLM, LM Studio, OpenAI)
- [x] Hold Slayer IVR navigation with LLM fallback for LISTEN steps
- [x] Call Flow Learner — auto-builds reusable IVR trees from exploration
- [x] Recording service with date-organized WAV storage
- [x] Call analytics with hold time stats, per-company patterns
- [x] Audio classifier with spectral analysis, DTMF detection, hold-to-human transition

### Phase 3: API & Integration ✅

- [x] REST API — calls, call flows, devices, DTMF
- [x] WebSocket real-time event streaming
- [x] MCP server with 16 tools + 3 resources
- [x] Notification service (WebSocket + SMS)
- [x] Service wiring in main.py lifespan
- [x] 75 passing tests across 4 test files

### Phase 4: Production Hardening 🔜

- [ ] Alembic database migrations
- [ ] API authentication (API keys / JWT)
- [ ] Rate limiting on API endpoints
- [ ] Structured JSON logging
- [ ] Health check endpoints for all dependencies
- [ ] Graceful degradation (classifier works without STT, etc.)
- [ ] Docker Compose (Hold Slayer + PostgreSQL + Speaches + Ollama)

### Phase 5: Additional Services 🔮

- [ ] AI Receptionist — answer inbound calls, screen callers, take messages
- [ ] Spam Filter — detect robocalls using caller ID + audio patterns
- [ ] Smart Routing — time-of-day rules, device priority, DND
- [ ] Noise Cancellation — RNNoise integration in media pipeline
- [ ] TTS/Speech — play prompts into calls (SPEAK step support)

### Phase 6: Dashboard & UX 🔮

- [ ] Web dashboard with real-time call monitor
- [ ] Call flow visual editor (drag-and-drop IVR tree builder)
- [ ] Call history with transcript playback
- [ ] Analytics dashboard with hold time graphs
- [ ] Mobile app (or PWA) for on-the-go control

## License

MIT