Log In with Google creates extra account

I added my gmail address as a secondary address, and tried to log in using the "Log In With Google" button, but it logged me in to a separate account, with the primary address being my gmail address, instead of associating me with the existing account.

There should be a way to merge accounts if the primary address on one matches the secondary address on another, and logging in with the secondary Google address, should log you in to the primary account.

The issue names no files, tests, or entry points. Begin by locating the Google login and account-address association flows, then document the existing behavior and the security implications of matching primary and secondary addresses before defining tests for login association and account merging.

Written by the indexing model from the issue text.