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# invalidate()

Stops the session.

```
func invalidate()
```

## Discussion

This method stops a running session. If you’ve scheduled a session, it cancels the session. If the session isn’t yet running or scheduled, this method triggers a [`WKExtendedRuntimeSessionErrorCode.notYetStarted`](/documentation/WatchKit/WKExtendedRuntimeSessionErrorCode/notYetStarted) error.

For sessions started with [`start(at:)`](/documentation/WatchKit/WKExtendedRuntimeSession/start(at:)), you can only call [`invalidate()`](/documentation/WatchKit/WKExtendedRuntimeSession/invalidate()) when the app is active. For all other sessions, you can call [`invalidate()`](/documentation/WatchKit/WKExtendedRuntimeSession/invalidate()) to end a session at any time.

After calling [`invalidate()`](/documentation/WatchKit/WKExtendedRuntimeSession/invalidate()), you can no longer run the session. Create and start a new session instead.

---

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