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

# Container events

> observe, ContainerEvent types, and integration with monitor.

Containers emit events when observers are registered via `observe()`. This powers `@brushy/di-monitor` and custom telemetry.

## Subscribe

```typescript theme={null}
const unsubscribe = container.observe((event) => {
  console.log(event.type, event.token, event.details);
});

// Later
unsubscribe();
```

<Note>
  Event emission is optimized away until the first `observe()` call. Attaching a monitor or observer enables the event path for subsequent operations.
</Note>

## Event types

```typescript theme={null}
interface ContainerEvent {
  type: "register" | "resolve" | "error" | "import" | "clear";
  token?: Token;
  timestamp: number;
  details?: unknown;
}
```

| Type       | When                                                     | Typical `details`                                               |
| ---------- | -------------------------------------------------------- | --------------------------------------------------------------- |
| `register` | `register` / `registerMany`                              | `{ config }`                                                    |
| `resolve`  | Successful `resolve` / `resolveAsync` / `resolveInScope` | `{ success: true, source, async?, scoped? }`                    |
| `error`    | Failed resolve                                           | `{ error, message, async? }`                                    |
| `import`   | `container.import()`                                     | `{ sourceContainer, targetContainer, providersCount, options }` |
| `clear`    | `clearRequestScope` / `clearScopedInstances`             | `{ scope }`                                                     |

## Performance note

When **no** observers are attached, `resolve` uses a fast path with a monomorphic last-token micro-cache. After `observe()` is called, every resolve goes through the event bus.

For production monitoring, prefer [@brushy/di-monitor](/di/monitor/overview) with filtered `eventTypes` instead of ad-hoc `observe` handlers on hot paths.

## Custom observers

```typescript theme={null}
container.observe((event) => {
  if (event.type === "error") {
    metrics.increment("di.resolve.error");
  }
});
```

## Related

* [Container monitor](/di/monitor/api-reference): buffered history and stats
* [Debug API](/di/di-core/debug): `exportProviders` for introspection