When can an opponent play action cards in relation to Yasuo and Mask triggers?

Ruling: Action cards and effects cannot be played while there is a chain open. Opponents must wait until the chain closes (the game reaches an open state) before they can play action cards, meaning Yasuo and Mask always trigger first.

Sequence:

• Yasuo and Mask trigger at the start of combat
• These triggers go on the chain
• The chain must fully resolve
• Only after the chain closes and the game reaches an open state can the opponent play action cards

Nuances:

• This applies even when Ride the Wind is used on the opponent's turn with Yasuo - the opponent still cannot respond with an action card until the chain resolves and closes