@Polina Zubova
The session details are saved in the cookie in the browser once the user logs in
Is your use case where multiple users can log in from the same browser on the same machine?
If that is not the case, any other user trying your app will still see a login screen since their browser cookie will not be set

When you log in using OAuth, the session cookies are stored in the browser when you are redirected to the RingCentral auth page and successfully log in.
There is also your use case where multiple users might be using the same machine and browser instance to log into the app where the cookies will not be deleted by default.
From what I know, the SDK does not have such an option to force deleting the cookies.

There are 2 things you can do that I can think of right now

1. Make sure the logged-in user closes the browser after login. Closing the browser instance after they are done working should (from what I know) clear the cookies. That being said, this is a manual task

2. You might want to implement your own loginWindow This function will be exactly what the SDK does with the addition of clearing the cookies before closing the browser.
What that means is that your loginWindow method should be exactly like https://github.com/ringcentral/ringcentral-js/blob/3f0fbee8e5a31bca9e43a9f6fa7470fbfaf92b49/sdk/src/platform/Platform.ts#L348 with the addition of clear cookie at line 394

These are the 2 suggestions that I have right now. Maybe anyone else reading this could add more to it if they are aware of it

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