When an opponent taps a seal, can you respond with a reaction speed spell, or can you only play an action speed spell after it resolves?

Ruling: Abilities that add resources finalize immediately and cannot be reacted to. After a seal resolves, you can play an action speed spell, but you cannot respond with a reaction speed spell because there is no chain to continue.

Nuances:

• While technically the question of "does tapping a seal start a chain" could be answered "yes," practically speaking you cannot react to it because it finalizes immediately.