[RPG] Which uses of Bonus-Action spellcasting are legal

actionsbonus-actionclass-featurednd-5espellcasting

Looking at other questions about casting spells as a bonus action has left me trying to keep a lot of information in my head about whether a given combination of spells is legal according to the official 5th edition spellcasting rules.

So I'd like to consolidate all these rules into a single easily accessible table, containing all the possible combinations of spells that could possibly be cast in a single turn, and hopefully create an easy reference for future use. But I'm not certain about how some of these combinations should be treated.

Based on the second question I linked, the ordering doesn't matter, so I've simplified the chart to ignore order of these actions, and only focus on what actions are being taken. But if I'm mistaken (i.e. the answer provided to that question was wrong) then this table will need adjusting.

Action Bonus Action Action Surge LEGAL?
Non-Cantrip Yes
Cantrip Yes
Non-Cantrip Yes
Cantrip Yes
Non-Cantrip Cantrip No
Cantrip Non-Cantrip Yes
Non-Cantrip Non-Cantrip No
Cantrip Cantrip Yes
Non-Cantrip Cantrip Yes
Non-Cantrip Non-Cantrip ?Yes?
Cantrip Non-Cantrip ?Yes?
Cantrip Cantrip Yes
Cantrip Non-Cantrip Non-Cantrip ?No?
Non-Cantrip Cantrip Non-Cantrip ?No?
Non-Cantrip Non-Cantrip Non-Cantrip ?No?
Non-Cantrip Non-Cantrip Cantrip ?No?
Cantrip Non-Cantrip Cantrip ?Yes?
Non-Cantrip Cantrip Cantrip ?No?
Cantrip Cantrip Non-Cantrip ?No?
Cantrip Cantrip Cantrip Yes

Is this table (Column 4 in particular) correct?

The core issue for me is that it's not clear to me how Action Surges interact with the spellcasting rules, hence the question marks listed there. It seems like an Action Surge might permit 2 leveled spells to be cast in a turn, unless a Bonus Action is used to cast a spell, in which case this is no longer permitted. If this is correct, then my table above should be correct, minus the question marks. But I need that validated.

Best Answer

The table is entirely correct

Action Surge does not interact in any way with the bonus-action spell rule (other than being limited in the same way as other spells if you use a bonus action spell). The bonus-action rule is only used for spells with a bonus-action casting time:

A spell cast with a bonus action is especially swift. You must use a bonus action on your turn to cast the spell [...] You can’t cast another spell during the same turn [that you would cast a bonus-action spell], except for a cantrip with a casting time of 1 action.

This is also further explained in one of the answers in the official rules clarification document Sage Advice Compendium (which is also here on D&D Beyond):

Is there a limit on the number of spells you can cast on your turn?

[...]

If you cast a spell [...] with a bonus action, you can cast another spell with your action, but that other spell must be a cantrip. Keep in mind that this particular limit is specific to spells that use a bonus action. For instance, if you cast a second spell using Action Surge, you aren’t limited to casting a cantrip with it.

Basically, if you cast (or will cast) a bonus-action spell (cantrip or non-cantrip) in a turn, no other non-cantrip spells (even ones using the action from Action Surge) can be cast.

Related Topic