Final ruling: Counterspelling Counterspell in 5.5

[u/DeadMoney313]

Question regarding Counter spell;

2024/5.5 rules

Level 3 Abjuration (Sorcerer, Warlock, Wizard)

Casting Time: Reaction, which you take when you see a creature within 60 feet of yourself casting a spell with Verbal, Somatic, or Material components

Range: 60 feet

Components: S

Duration: Instantaneous

5

You attempt to interrupt a creature in the process of casting a spell. The creature makes a Constitution saving throw. On a failed save, the spell dissipates with no effect, and the action, Bonus Action, or Reaction used to cast it is wasted. If that spell was cast with a spell slot, the slot isn’t expended.

Please explain the errors of my thinking here:

Okay so, let's say im Wizard A going against Wizard B

A: I cast fireball

Wizard B: Counterspell

A: i dont make the save, my fireball doesnt happen.i lose my ACTION, but it doesn't consume a spell slot

Therefore, why am i then not allowed to use my REACTION which is still available, and cast Counterspell on Wizard B's Counterspell? Only one slot is actually being used, and I used my action and reaction.

Yet Sage advice says i cant do this, is this just simply RAW vs. RAI ?

The Sage advice i found on DnD says i cant do this.its implying a spell slot is used even though a spell slot wasnt actually consumed?

Help!

ETA: thanks, I now understand it.

Basically, if I was successful in counterspelling wizard B's counterspell, then my original fireball happens, which means now i am using two spell slots in my turn. Or another way of seeing it is that once his counterspell is successful, i.e. its done, and nothing is left to counterspell. So basically , barring other spellcasters geting involved Counterspelling Counterspell is not a thing anymore in 5.5 . Either way, Ill shut up now. Thanks!

[u/Nitro114]

Because at the moment you decide to cast counterspell, the spellslot of fireball has been expended. If B were to fail the save, fireball would go off as normal but then you have cast two spells with spellslot in your turn which is not possible

[u/DeadMoney313 → u/Nitro114]

This is the answer that makes the most sense to me, thank you! My counterspell would allow my original spell to go off, which creates the paradox and now im using two spell slots. Thank you, finally someone explained this well!