> ## Documentation Index
> Fetch the complete documentation index at: https://docs.51ultron.com/llms.txt
> Use this file to discover all available pages before exploring further.

# Sentinel

> Infrastructure monitoring, health checks, uptime tracking, and self-improvement logging.

Sentinel watches your systems. It catches problems before they become failures, logs every error as a lesson, and attempts self-healing before escalating. It's the agent that runs in the background so every other agent can run cleanly.

## What Sentinel monitors

```text theme={null}
Sentinel health check run
├── API connectivity
│   ├── Ultron platform endpoints
│   ├── Connected integrations (Gmail, HubSpot, Stripe, etc.)
│   └── MCP server availability
├── Auth status
│   ├── OAuth token expiry checks
│   └── API key validity
├── Performance
│   ├── Response time baselines
│   └── Error rate trends
└── Self-checks
    ├── Memory store integrity
    └── Lessons database review
```

## Error handling

When Sentinel detects a problem:

1. **Attempt self-healing** — retry with backoff, re-auth, clear cache
2. **Log the lesson** — store what broke and how to prevent it next time
3. **Alert if unresolved** — Slack message or email to the configured recipient

Sentinel never escalates without first attempting a fix.

## Lessons logging

Every error Sentinel catches becomes a lessons-system entry:

```json theme={null}
{
  "type": "feedback",
  "tags": ["lesson", "sentinel", "auth"],
  "text": "LESSON: Gmail OAuth token expired mid-session without warning. PREVENTION: Check token expiry at session start, refresh if within 24 hours of expiry."
}
```

Next run, Sentinel checks for its own lessons first and applies them before starting any task.

## Alerting

Sentinel sends alerts via connected channels when critical thresholds are hit:

* **Slack** — message to your configured #alerts channel
* **Email** — via Gmail or Brevo to your notification address
* **Threshold examples** — API error rate > 10%, auth token expired, uptime \< 99.5%

## Self-improvement over time

Sentinel is the primary contributor to the lessons system. Over weeks of operation, the lessons database accumulates a complete picture of every failure mode in your configuration — and the fix for each one. The entire Ultron agent team benefits from what Sentinel learns.