### CHELSTY Stability Agent

The stability-agent on CHELSTY provides local observability and health monitoring for the node's services and infrastructure.

#### Purpose

It acts as a filesystem-first watchdog that detects anomalies in the local runtime environment without taking autonomous destructive actions (like restarts). It serves as the primary data source for node-level stability metrics.

#### Monitoring Scope

*   **Docker Containers**: Monitors all local containers. If a container is not in the `running` state, a `containers_not_running` event is generated.
*   **Disk Usage**: Monitors the root filesystem. Generates `disk_usage_high` events if usage exceeds the configured threshold.
*   **Connectivity**: 
    *   Checks if the Tailscale socket or interface is available.
    *   Checks reachability of the local Mosquitto MQTT broker.
*   **Zigbee2MQTT**: Specifically tracks the presence and status of the Zigbee2MQTT service.

#### Storage and Integration

*   **Heartbeat**: Updated every cycle at `/opt/homelab/state/stability-agent.heartbeat`.
*   **State Summary**: A JSON summary of all latest checks at `/opt/homelab/state/stability-agent.json`.
*   **Events**: Append-only JSON lines at `/opt/homelab/events/YYYY-MM-DD/chelsty-infra/events.jsonl`.

#### Deployment

The service is deployed via Docker Compose on CHELSTY.

```bash
cd services/stability-agent
docker compose up -d
```

#### Configuration

Configuration is managed via environment variables in `docker-compose.override.yml` on the host.

| Variable | Description | Default |
|----------|-------------|---------|
| `STABILITY_CHECK_INTERVAL` | Seconds between checks | `60` |
| `DISK_THRESHOLD_PCT` | Disk usage alert threshold | `90` |
| `MQTT_HOST` | MQTT broker hostname | `mosquitto` |
| `MQTT_PORT` | MQTT broker port | `1883` |
