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# WKExtendedRuntimeSessionErrorDomain

The domain for errors reported by extended runtime sessions.

```
let WKExtendedRuntimeSessionErrorDomain: String
```

## Discussion

The session passes these errors to the session delegate’s [`extendedRuntimeSession(_:didInvalidateWith:error:)`](/documentation/WatchKit/WKExtendedRuntimeSessionDelegate/extendedRuntimeSession(_:didInvalidateWith:error:)) method.

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