Casting a Bonus Action and Reaction Spell on Your Turn

I recently ran a session where I had a weird spellcasting interaction. A player character (PC) provoked an opportunity attack and used the Shield spell to block it. Then, they couldn’t cast a bonus action spell because they had already cast a non-cantrip. This struck the entire table as odd, so I started looking for a way to fix it.

The Rule

The bonus action spellcasting restriction in 5th Edition D&D provides that when you cast a spell on your turn using a bonus action, you can’t cast any spell other than a cantrip other than a cantrip with a casting time of 1 action:

The reason this struck me as odd is because the restriction seems intended to impose a limit on the PC’s ability to cast a leveled spell with their action. It does not seem intended to impose a restriction on the PC’s ability to cast a reaction spell. After all, what’s the practical difference between casting a reaction spell on or off your turn?

Yet, an examination of the 2019 Sage Advice Compendium reveals that indeed the bonus action spell restriction locks down your ability to cast other non-cantrip spells on your turn:

Further, casting a reaction spell on your turn doesn’t mean that the reaction occurs outside your turn. In fact, a reaction spell can be cast during your turn:

Examining D&D Lead Rules Designer Jeremy Crawford’s tweets on the subject suggests that this rule is indeed the Rules as Intended (RAI), matching the explicit language of the Rules as Written (RAW):

While not explicit, the fact that the unstated reaction limitation is not addressed leads me to believe that the RAW matches the RAI on this matter. Yet, it’s not an interaction that I feel necessary to impose in my game. Splitting hairs on whether the reaction occurs on your turn doesn’t really jive with me, especially since the 6 seconds of each round technically happens simultaneously—notwithstanding the fact that you could never make simultaneous rounds narratively jive with the turn mechanics, especially when you consider movement.

Now, one nefarious workaround would be to use a Ready action to prepare a leveled spell that triggers on the resolution of your bonus action spell. Jeremy seems to have anticipated this workaround, as evidenced by this tweet later in the chain:

Since a readied action consumes your reaction when it goes off, we can see where the broad language originated. With a little creativity, we can still enforce this limitation while permitting reaction spells.

The Solution

Instead of imposing a limitation on any other spell you cast during your turn, it makes more sense to me to limit the power of spells you can cast with your action. This would free up your reaction spell to be cast at any time, whether it’s on your turn or not. As such, I suggest using language that says “the only spell you can cast with your action is a cantrip.” I would rewrite the rule as follows:

With this simple change, we open up the possibility of using a reaction spell on or off your turn, regardless of whether you cast a bonus action spell. We don’t need additional language to stop the readied spell workaround, since other mechanics already have that covered:

First, the reaction limitation already stops that from happening. Specifically, when you use a reaction, you can’t use a new reaction until the start of your next turn (see Player’s Handbook, p. 190). So even if you wanted to use your Ready action to prepare a spell, it could never go off until after it expired.

Second, when you use a Ready action to start preparing a spell, the casting begins when you take the Ready action:

What do you think about the reworked rule? Do you like it? Can you break it? Let us know in the comments below!