Use case
The run gets to the login and stops there.
Every useful page sits behind an account, and that is where most runs end: a password nobody wants to hand over, a code in an inbox the agent does not have, six digits that change every thirty seconds. Here the browser signs in by itself, keeps the session, and goes on to the task you actually asked for.
Sign in
Use your Microsoft account.
The password is typed, never passed
It lives encrypted on your disk. The agent names the field, the layer below fills it in, and the value appears in no argument and no log.
Codes arrive where the work happens
Every profile has its own address and its own number. Confirmation codes and magic links are read outside the browser, so no second login opens in the session.
The session survives the run
Cookies and passkeys live in the profile and outlive a crash, an update and the window closing. The next run starts signed in.