What does the Sage Advice Compendium mean in this example about casting multiple spells in a turn using Action Surge?

Question

The Sage Advice Compendium has this text:

If you cast a spell, such as healing word, 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.

From this tweet by rules designer Jeremy Crawford, I understand that if you cast a spell using a bonus action, then cast a cantrip as an action, and then use Action Surge, you can only cast another cantrip with that additional action. However, I don't understand the example they wrote. It seems to be misplaced.

Can anyone elaborate on what is the meaning of their example? Do they mean "If you cast a spell as a normal action (not as a bonus action), and then Action Surge, you can cast another spell on your second action."?

Answer 1

Action Surge allows you to cast more than 1 Action Spell in a turn.

However, it only works if you are casting two Action cost spells. In order to cast a Bonus Action spell, the general spellcasting rules dictate what you can do.

They were trying to provide further direction on Action/Bonus Action casting with regard to spellcasting limitations but also state that the exception to that rule is casting two Action cost spells with an Action Surge.

Answer 2

If you don't cast a spell as a bonus action, you are not limited in what spells you can cast (including using Action Surge).

The segment you quoted deals with the number of spells a character can cast in one round.

Previously it explains that there is no hard limit but your character's number of available actions impose a practical limit. It goes on to explain about the interaction of Bonus Action casting time spells and 1 Action casting time spells (because that is the most likely way a character will cast more than 1 spell on a turn), then clarifies that the restriction to cantrips is only imposed when using a Bonus Action spell, not a general restriction on casting 2 or more spells in a turn.

Action Surge is presented as an example of a way to cast 2 spells without invoking the "cantrip only" restriction.

Answer 3

This is a quirk that results from how they restricted casting with bonus actions.

Part of your confusion probably arises from the nonsense that this implies. (NautArch and GreySage are both completely right - and I upvoted them - but I wanted to offer some additional explanation without answering in comments.)

Let's say you have an action surge (2nd action). If you want to cast as much as possible with the highest level spells, this is the best you can do:

• use both of your actions to cast non-cantrips; the bonus action can't be used to cast a spell
• use your bonus action to cast any spell; you may only cast cantrips with your 2 actions

It always feels odd to me due to the way that they worded it, that a high-level eldritch fighter can use their highest 2 spell slots and make a melee attack (as a bonus action), but they can't cast a bonus action cantrip and use just 1 of their 2 actions to cast a non-cantrip. But those are the rules.

Also, a sorcerer can cast a cantrip as an action and quicken a non-cantrip, but can't cast the non-spell as an action and quicken the cantrip. These are essentially the same, but one is allowed and the other is not. I think this is the best illustration of how the rule is poorly written.

<-- rules / how I'll play -->

To complete my thought, I wish they had worded the rule like this (and it's how I'll probably play it as DM): When you cast a spell that is not a cantrip as a bonus action, your original action may not be used to cast a spell that is not a cantrip.