Can Vi's buffing ability be used on an opponent's turn?

Ruling: No, Vi's ability cannot be used on an opponent's turn. It is an activated ability at base speed, which can only be used during your own turn with no existing chain.

Nuances:

• Vi's ability is not technically a "buff" - buffs are a protected term in Riftbound. Vi's ability increases her might.
• The ability is an activated ability, not a trigger.