If a unit gains deflect after a spell targeting it is already on the chain, does the caster have to pay the deflect cost?

Ruling: No, the caster does not have to pay for deflect retroactively. Deflect is an additional cost that must be paid when declaring targets; if a spell is already on the chain, adding deflect to the targeted unit does not affect that spell.

Sequence:

• Player A casts a spell targeting unit B (spell goes on chain)
• Player B gives unit B deflect
• Player A's spell resolves without needing to pay deflect cost

Nuances:

• Deflect only applies at the moment targets are declared, not after a spell/ability is already on the chain