> US person here who has participated in a lot of online advice/mentoring forums. I've never once seen a tech company immediately "fire" someone who says they're resigning like the parent comment claims.

I've seen it happen multiple times. Microsoft has a list of competitors that if you say you are going to work for them, your access to everything is immediately revoked.

Managers at MS ask their employees to NOT SAY where they are going, so a proper off-boarding can take place.