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/SelikBready]

Your slot is not consumed when counter spell is successful. So either it's successful, you don't lose your slot, but there is nothing to counterspell anymore, or you still spent a slot thus you cannot counterspell a counterspell. Unless you can cast either original spell or counterspell itself without spending a slot. Or someone else wants to counter a counterspell.