Can you float mana from runes in response to Sona's end-of-turn trigger, let her ready them, then use the floating mana plus newly tapped runes to cast an action spell before the turn ends?

Question

Accepted Answer

Ruling: No, you cannot cast an action spell in this scenario. After end-of-turn abilities resolve, the turn ends immediately, so action spells cannot be played at this timing.

Nuances:
- You can float mana in response to Sona's trigger and have her ready the runes, giving you both floating mana and ready runes
- If you have multiple end-of-turn triggers (like two Sonas), you can use this floating mana plus newly tapped runes to cast a reaction spell (not an action spell)
- Action spells can never be played during end-of-turn trigger timing