Does Assault (like on Cleave ACTION) work when played during combat after the initial attack designation, and how do attack triggers like Yasuo's work when units enter combat late?

Ruling: Assault is a passive ability that functions as "While I am an attacker, I have +X Might" and applies whenever the unit has the Attacker designation. Attack triggers ("When I attack...") can only trigger once per combat per unit, but they will trigger the first time a unit gains the Attacker designation even if it enters combat late.

Sequence:

• Attacker designations are checked at the start of combat
• Attacker designations are also checked during every cleanup step
• When a unit gains the Attacker designation for the first time in a combat, attack triggers go on the chain
• Assault bonuses apply continuously while a unit is an attacker

Nuances:

• Attack triggers can only become fulfilled once per combat, even if a unit gains and loses the Attacker designation multiple times
• Units that enter combat late (after initial attack designation) will have their attack triggers fire during the cleanup step when they first gain the Attacker designation