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

# Lifecycle hooks

> React to .NET run, model, step, tool, and checkpoint events.

Pass `RunOptions.OnEvent` to update a product timeline, audit log, or telemetry pipeline.

Event families cover run start/resume/terminal states, model requests, step checkpoints, tool execution and progress, human waits, cancellation, and failures.

Keep the callback fast. Queue slow storage or network work outside the agent loop.

```csharp theme={null}
OnEvent = value => logger.LogInformation(
    "{EventType} {RunId}", value.Type, value.RunId
);
```

## Related

* [Streaming](./agent-sdk-streaming)
* [DevTools](./agent-sdk-devtools)