PrC Stacking Question

[ekarney]

From 2nd level on, when a new eldritch knight level is gained, the character gains new spells per day as if she had also gained a level in whatever arcane spellcasting class she belonged to before she added the prestige class.
...
If a character had more than one arcane spellcasting class before she became an eldritch knight, she must decide to which class she adds each level of eldritch knight for the purpose of determining spells per day.

What I'm asking is would the "+1 level of existing arcane spellcasting class" stack with say, Archmage if you designated the Archmage as your "Existing Spellcasting Class".

Personally I'm fairly sure this doesn't work, but I do want to actually confirm this.

[torrasque666]

Archmage is not a Spellcasting Class. It progresses a different​ spellcasting class, but gives no casting of its own.

[ezekielraiden]

What I'm asking is would the "+1 level of existing arcane spellcasting class" stack with say, Archmage if you designated the Archmage as your "Existing Spellcasting Class".

Personally I'm fairly sure this doesn't work, but I do want to actually confirm this.

You can only advance another class if that class, on its own, has a defined spellcasting progression. Archmage does not, so you cannot gain "+1 level of Archmage spellcasting." However, some PrCs do have their own spell progression, and you can advance that. Sublime Chord is a common example, particularly because after the second level, most of its class features are fairly lackluster. A common pattern is Bard 8/Virtuoso 2/Sublime Chord 2/Virtuoso +8.

But in general the vast majority of prestige classes don't have their own spellcasting progression, so you can't advance them with a second PrC's "+1 level of spellcasting class" features. The only PrCs I know of that can do that are Legacy Champion and Uncanny Trickster (and Evangelist in Pathfinder) because those advance all class features, not just "+1 level of spellcasting."

[KillianHawkeye]

Even if you COULD advance an archmage's casting with the +1, you wouldn't continue to gain archmage class features. The +1 spellcasting advancement improves spellcasting and nothing else.

[ekarney]

Thanks everyone, I had a suspicion it wouldn't work but couldn't exactly clarify how so I really appreciate it.

[PoeticallyPsyco]

There actually are two classes that can pull off this prestige stacking trick. Uncanny Trickster and Legacy Champion both advance all the features of another class, which can include the +1 spellcasting of a prestige class. (Funnily, they can also advance each other, but that's a discussion for a different thread).