Does a showdown end immediately when all attacking units are removed from the battlefield, or does it continue until both players pass without starting a chain?

Ruling: Showdowns only end when both players pass focus without starting a chain. It does not matter if no units are currently attacking.

Nuances:

• Even if all attacking units are removed from the battlefield during a showdown (such as being pushed back), the showdown phase continues until both players consecutively pass
• Units can still heal from combat damage during the showdown even after attackers are removed, as long as the showdown phase hasn't ended