multi-classing and "known spells" question

[tchntm43]

So I am working on building a random character generator that can do any level from 1-20, and with each level it will somewhat intelligently make decisions based on what has been decided for previous levels, as well as getting randomized gear that is based on versions of Magic Tables A-I that have been adjusted to only give stuff that fits the character class. Originally I was like a big hell naw to the idea of having it able to generate multi-class characters just because of the complexity involved, but I caved in this morning and started rewriting a lot of code to make it happen.

The rules governing spellcasting (determining spell slots and known/prepared spells) for multi-class characters are horrendous to code. Especially so if the character has levels in two or more spellcasting classes. I just want to make sure I am doing this correctly, though. Am I correct that the spells a multi-class character knows have to be linked to the class they're known to? For example a character with both Bard and Cleric levels who knows Dissonant Whispers as a Bard would not include Dissonant Whispers as a possible prepared spell for the list the Cleric side prepares, right? So basically a character like this has to maintain separate lists of known spells for each spellcaster class they have, right? And any prepared lists have to be separate as well? But despite keeping separate lists of known/prepared spells, this character should just have a single set of spell slots to use for either class' spells?

But there's no reason to keep separate lists of cantrips, right? I'm trying to think of a reason and I can't (plus the Minor Illusion cantrip that Forest Gnomes get doesn't even identify as belonging to a class).

Let me know if there is any aspect of this that I'm off about. Thanks.

[Darc_Vader]

That looks mostly correct to me. Spells known/prepared are completely separate for each class you have, so the hypothetical Bard/Cleric would have the spells known of a level x Bard from the Bard list, and be able to prepare spells from the Cleric list as if they were just a level y Cleric. The two have no interaction whatsoever, you could even hypothetically learn say Healing Word as a Bard, and then also prepare it as a Cleric simultaneously, taking up one available spell from each class. You are also correct that there is no spell list merging; the two (or more) lists remain distinct.

As for Cantrips, the only thing that matters about which class they come from is what stat modifier they use: a Wizard/Sorcerer multiclass will add their Int modifier to the attack roll of a Firebolt if they learned it from the Wizard list, and Cha if it's learned from the Sorcerer list instead. There are also some class features like the Cleric's Potent Spellcasting feature that only apply to cantrips(/spells) from their own class.

[WaroftheCrans]

You have an entirely separate spell list for each class you are in. This matters for cantrips as well, maybe it even matters especially for cantrips, as a number of features only work for cantrips that are of that class.

Artillerist artificer, nearly any cleric, evoker wizard, warlocks all come to mind for this.

The only thing shared is spell slots, I'd recommend treating spell slots as an entirely different animal than spells known.

[tchntm43]

you could even hypothetically learn say Healing Word as a Bard, and then also prepare it as a Cleric simultaneously, taking up one available spell from each class.
But that would be wasteful, right? Like, if I were a person making smart choices, I would never want my Cleric side to prepare a spell that my Bard side already knows and has permanent access to. So I would want to make sure that if a spell is known by any classes that don't have to prepare spells, the classes that do have to prepare spells don't waste a prepared spell on that.

As for Cantrips, the only thing that matters about which class they come from is what stat modifier they use: a Wizard/Sorcerer multiclass will add their Int modifier to the attack roll of a Firebolt if they learned it from the Wizard list, and Cha if it's learned from the Sorcerer list instead. There are also some class features like the Cleric's Potent Spellcasting feature that only apply to cantrips(/spells) from their own class.
Ah, I forgot about the ability score modifiers on spells. Darn, will have to have separate Cantrip lists, too, then.

[tchntm43]

Oh, one other question. Suppose a non-spellcaster takes the Magic Initiate or Ritual Caster feat, each of which grants at least one spell of at least level 1. Later they multi-class in a spellcaster class and gain spell slots. Can they use the spell slots to cast the spells gained from the feats, or do they have to separately learn those spells for the spellcaster class?

[Darc_Vader]

But that would be wasteful, right? Like, if I were a person making smart choices, I would never want my Cleric side to prepare a spell that my Bard side already knows and has permanent access to. So I would want to make sure that if a spell is known by any classes that don't have to prepare spells, the classes that do have to prepare spells don't waste a prepared spell on that.
Correct, it would do nothing but waste a spell known/prepared unless you for some reason had class features that applied to spells of just that class that you wanted the ability to use either.

Oh, one other question. Suppose a non-spellcaster takes the Magic Initiate or Ritual Caster feat, each of which grants at least one spell of at least level 1. Later they multi-class in a spellcaster class and gain spell slots. Can they use the spell slots to cast the spells gained from the feats, or do they have to separately learn those spells for the spellcaster class?
Ritual Caster doesn’t say you learn the spells, so I would think that you can’t cast them with spell slots regardless of single-class or multiclass. Magic initiate does say you learn the spell, and I think technically by RaW a single classed caster can only use slots on that spell if you choose it from the same list because of the wording here:

The Bard table shows how many spell slots you have to cast your bard spells of 1st level and higher.
But the multiclass rules allow for using spell slots to cast any spells you know/prepare so I believe a multiclass caster can use slots for the feat-granted spell freely.

Edit: missed part of your question: if a non-caster multiclasses into a caster, they are not considered a multiclass caster and use solely the spellcasting rules from their own class. The Magic Initiate spell would only be castable with slots if a) it’s from the same class as your spellcasting, or b) you have levels in at least 2 classes with the spellcasting feature and thus are using the multiclass spellcasting section.

[WaroftheCrans]

Oh, one other question. Suppose a non-spellcaster takes the Magic Initiate or Ritual Caster feat, each of which grants at least one spell of at least level 1. Later they multi-class in a spellcaster class and gain spell slots. Can they use the spell slots to cast the spells gained from the feats, or do they have to separately learn those spells for the spellcaster class?

Ritual Caster is a flat No. Magic Initiate there is a long long debate over, that's been exacerbated by Tasha's, and I'd recommend going with whatever is easiest to code.

[bid]

The rules governing spellcasting (determining spell slots and known/prepared spells) for multi-class characters are horrendous to code.
It's not that bad, just make MC characters composite of single-classed ones. Define an actual character as a list of class characters.

All cleric 5 prepare spells the same way whether they are pure level 5 or character level 10 with cleric 5 / druid 5. Therefore MC has no impact on that.

You'll only have to handle MC spell slots if you want to upcast spells, which is beyond your goal.

[Verble]

But there's no reason to keep separate lists of cantrips, right? I'm trying to think of a reason and I can't (plus the Minor Illusion cantrip that Forest Gnomes get doesn't even identify as belonging to a class).

Let me know if there is any aspect of this that I'm off about. Thanks.

Just keep in mind that different classes have different ability stats that those cantrips key off of. This also varies for spells and cantrips granted by race or feat.