When attacking with 6c green Yasuo's ability before showdown, if the opponent reacts with Shen, does Yasuo's ability target the original enemy or does Shen become the new target?

Ruling: Yasuo's ability targets the original enemy unit and cannot be changed once on the chain. Shen's Tank ability does not affect Yasuo's "When I attack" effect because it is not combat damage, but Shen will require damage assignment during the Combat Damage Step.

Sequence:

• Yasuo moves to an enemy-controlled battlefield and a Showdown starts
• Yasuo's "When I attack" effect triggers and goes on the chain, targeting the enemy unit at the battlefield
• The opponent reacts by flipping Shen
• Yasuo's effect resolves with the original target (targets cannot change once on the chain)
• The original target dies to Yasuo's effect
• Both players pass, Showdown ends, Combat Damage Step starts
• Yasuo deals 6 combat damage, some must be assigned to Shen due to Tank (Shen also deals damage to Yasuo)

Nuances:

• Yasuo's "When I attack" effect is not considered combat damage, so Tank does not redirect it
• Tank only applies during the Combat Damage Step