Can Action speed spells be played during the attack/defend trigger chain, or only after those triggers resolve?

Ruling: Action speed spells cannot be played during the initial attack/defend trigger chain. Only Reactions can be played in response to attack/defend triggers. Actions can only be played after all attack/defend triggers have resolved.

Sequence:

• When a unit moves to a battlefield with an opposing unit, resolve "When I defend" triggers first
• Then resolve "When I attack" triggers
• During these trigger chains, only Reactions can be played in response
• After all triggers resolve, a new window opens where the attacking player can play Actions or Reactions
• Then players alternate playing Actions or Reactions until both pass

Nuances:

• Attack/defend triggers create their own chain separate from the main showdown action window
• The attacker gets priority to play Actions first after triggers resolve