Access tokens are automatically invalidated when a non-Yggdrasil launcher (such as FTB) authenticates with Mojang

A launcher such as FTB that uses the old method of logging in seems to invalidate all of the new launcher's access tokens, requiring us to re-login when switching between the two launchers. This is a pain for me especially because my kid brother plays both FTB and vanilla and thus I have to re-login for him every time he switches. While I know you guys won't do this, I would love an option to bring back the old "store credentials locally" feature. Either way, this really needs a fix.