Users are seeing the "The provided anti-forgery token was meant for a different claims-based user" message when they are trying to log into BluSKY.
Message in Chrome browser
Message in Edge browser
This message means that the browser noticed that the user trying to log into BluSKY is different then the user that was previously identified for this browser. This can happen if the browser window is closed unexpectedly, there are different logins in different browser tabs, or simple the system did not finish logging out of BluSKY and the security token has not been cleared out.
This is very common with logins to secure servers.
If the user selects the logout button in the upper right and logs back in they should be fine. The logout button clears the token, so a new login is not seen as something suspicious.