What ways are there to disrupt spellcasting in 5e?

[Rukelnikov]

Is that the same PHB that says a readied action happens after the trigger finishes?

Yup, we all agree on that

[JoeJ]

Yup, we all agree on that

But you seem to think that perceiving somebody (who wasn't previously doing so) cast a spell and perceiving them start to cast a spell are different in some meaningful way. I don't, nor is there any rules support for that interpretation. So it remains: You ready an action for when somebody starts to cast a spell. They cast a spell and then you take your readied action.

[Rukelnikov]

But you seem to think that perceiving somebody (who wasn't previously doing so) cast a spell and perceiving them start to cast a spell are different in some meaningful way. I don't, nor is there any rules support for that interpretation. So it remains: You ready an action for when somebody starts to cast a spell. They cast a spell and then you take your readied action.

I can ready for any perceivable trigger.

I ready an action for when someone starts talking. According to you I have to wait till they finish talking to shoot them?

If you say yes, well thats some free speech in your tables!

If you say no, then I can do the same for verbal components

[JoeJ]

I can ready for any perceivable trigger.

I ready an action for when someone starts talking. According to you I have to wait till they finish talking to shoot them?

Of course. Unless they speak long enough to use more than just their action, you shoot when they finish. Why is this hard to understand?

[Max_Killjoy]

It should be fairly obvious that those posters were talking about 1 Action (or less) casting time spells, as the rules for longer casting times are completely different, and quite interruptible. If any of us were talking about interrupting spells with a longer casting time, the debate would have been over with the first post that cited the "Longer Casting Times" text from the PHB.

So assuming you were just asking a totally innocent question, I did give a straightforward answer regarding the Longer Casting Time rules and how it would function as RAW...but that it is not even remotely the same situation. You then replied:



Given from your carefully worded posts you are clearly not an idiot, I find it impossible to believe you are unable to understand the difference between an "exception" to a rule, and a completely different rule that acts in a completely different way.

It is a clever spin game, using Longer Casting Time to try and refute that a 1 Action casting time spell cannot be sub-divided into beginning/casting/finished...but those are completely different rules. (Not that they even divide a spell into beginning, middle, and end...they just draw the casting time out over many Actions, with Concentration needed in between.) Even if that opens up the debate about how a "the wizard casts a spell" applies towards a wizard using the Cast A Spell Action over and over to cast a Longer Casting Time spell as a Ready Action trigger, it does not affect the RAW game mechanics of a 1 Action spell. Two separate rules, two separate questions.

It may seem strange or unnatural to some, but common sense does not always apply when it comes to game rules, and that is often by design.

Regarding rules lawyering...I'm sure the reason players want to make the argument that they can interrupt a spell being cast with an attack is indeed that they don't like that this option was removed from the 5e rules (after being explicitly present in past editions). But its still rules lawyering.

Also, everyone: I am still waiting for a good answer from anyone to the following:

Please cite where it states that a specific spell description's ability should apply to a general situation, counter to 5e's PHB Introduction that states "specific beats general." (the "since Coutnerspell allows you to interrupt, it means anything should allow you to interrupt" argument)

Why they believe the ability to attack and interrupt a 1 Action or less casting time spell is meant to be included in 5e even though it was explicitly described in earlier editions but has been left out of 5e's RAW. One sentence (either under Ready Action or Casting a Spell) could have clarified how this would work. It's not a new idea. It is there for Longer Casting Time spells! Why isn't it stated in the RAW for 1 Action casting time spells?

The problem isn't that I don't understand, the problem is that I don't care what the rule does say, I care about whether the rule follows the "fiction" -- whereas much of this discussion either doesn't care about the "fiction", or expects the "fiction" to follow the rules.

And then there's the deeper problem that 5e in particular is evidently allergic to having expressed and robust "fiction" against which to compare the rules. As I noted earlier, the real solution here lies in the answer to the questions of how long it takes to cast a spell, what's actually involved, etc... and "an action" is NOT an answer to that question.

If common sense doesn't apply to an RPG rule, if the rule gleefully flips common sense the bird, then that rule is broken. This isn't an abstract board game, the rules of an RPG need to have synergy with what's going on "in fiction" or they're not doing their job.

[Rukelnikov]

Of course. Unless they speak long enough to use more than just their action, you shoot when they finish. Why is this hard to understand?

Because nothing in the PHB says it works that way, as soon as they start talking my trigger is finished.

[Unoriginal]

Because nothing in the PHB says it works that way, as soon as they start talking my trigger is finished.

When does a start finishes?

[Rukelnikov]

When does a start finishes?

As soon as it starts

[JoeJ]

Because nothing in the PHB says it works that way, as soon as they start talking my trigger is finished.

Everything in the PHB and in the DMG that talks about the Ready action at all says it works the way I described. As soon as they finish talking, whatever you did gets resolved.

[Rukelnikov]

Everything in the PHB and in the DMG that talks about the Ready action at all says it works the way I described. As soon as they finish talking, whatever you did gets resolved.

In your table maybe, mine follows RAW

[JoeJ]

In your table maybe, mine follows RAW

If your table does what you described here, then you're not following RAW. But there's nothing wrong with doing it however you want in your own game.

[Rukelnikov]

If your table does what you described here, then you're not following RAW. But there's nothing wrong with doing it however you want in your own game.

Yes we are, since we take ready after triggers have finished, not after actions have finished.

[JoeJ]

Yes we are, since we take ready after triggers have finished, not after actions have finished.

Clearly, neither of us is going to convince the other, so we might as well just agree to disagree and leave it at that.

[Rukelnikov]

Clearly, neither of us is going to convince the other, so we might as well just agree to disagree and leave it at that.

Yup, it'll be for the best, it was an interesting debate nonetheless.

[Unoriginal]

As soon as it starts

So according to you, you can use Ready to react as soon as the trigger starts?

[Rukelnikov]

So according to you, you can use Ready to react as soon as the trigger starts?

As soon as the trigger finishes, which is, for example, as soon as someone starts talking.

Anyway, as JoeJ said, this is not gonna go anywhere, so we might just agree to disagree.

[jh12]

As I noted earlier, the real solution here lies in the answer to the questions of how long it takes to cast a spell, what's actually involved, etc... and "an action" is NOT an answer to that question.

Except only one side of the debate needs an answer to all of these questions (how long it takes to cast a spell, how long it takes to cast a readied spell as a reaction, how long it takes to recognize that a spell is starting, how long it takes to react to a spell starting, whether the caster is prevented from casting a spell or just has to start over, etc.), answers that pretty clearly aren't part of the rules. That's a pretty good argument in favor of the other side.

[Unoriginal]

As soon as the trigger finishes, which is, for example, as soon as someone starts talking.

But you just said a starts finishes as soon as it starts.

So if the reaction is as soon as the trigger finishes, and the starts finishes as soon as it starts, it means that according to you, the reaction is as soon as the trigger starts.

Is that correct? If no, could you explain how it is not?

[ThePolarBear]

I can perceive the caster going for the component pouch, or speaking unintelligible words.

And those, as i already typed PAGES ago, are all fine triggers. Which might not accomplish what you are actually proposing, however (going in between the start of spellcasting and after it)

Triggers can be deductive

NO THEY CAN'T. Not for the Ready Action. That's the whole point of "perceivable occurrence". You cannot have a trigger like "when Lighty McSnuffle snuffs off the candle" and expect, if the candle no longer burns to trigger your action If you did not perceive Lighty put it out!*

"If someone hurts me I use second wind"

How is this a deduction? Either you perceive someone, or not. If you can't perceive the someone, like if there is a trap, the trigger hasn't come to pass. Unless you mean that the PAIN you feel is the trigger, then "if i feel pain" is the ACTUAL, INTENDED trigger. And someone is absolutely unnecessary, unless YOU want it to STRICTLY be a someone, and not a trap or other occurrence like a natural lightning bolt.*

a hidden rogue (attacks) me (?). I didn't see it happen, but i'm hurting I get to use second wind.

Then the trigger should have been "If i am hurt". If you don't care HOW or WHY, do not put it in. If the trigger is "I'm hit by a blue motorcycle", and the motorcycle is black, red, or invisible... you do not get to heal! (letting aside "second wind" being a bonus action, yadda yadda)*

Some posters have claimed that the if trigger for the Reaction is "that guy casts a spell", then the Reaction can't happen until the spell casting has finished.

No. Some posters have provided quotes about the Ready Action having such a wording included in the text. "Claim" is something unsupported by proof.

One of the problems is that spell casting clearly isn’t instant... there is waving of hands, manipulating material components, chanting... it isn’t ‘snap’ and done, it takes some time... and in that time is it interactable? The rules give little guidance on it, and I presume the default is ‘no’

It's way "worse" than that. Rules do not (and imho, are not even meant to) give much indication of what spellcasting even IS. It's not part of our world (afaik). It's left to each group's imagination. We only know that "casting" is perceivable, when it is (not even HOW, or WHY, mind you).

That's exactly the point, saying begins casting a spell, means it triggers once they started, since I can't perceive it beforehand (unless I have foresight I guess)

And the reaction happens after it finishes ANYWAY. And again, if you are considering "casting a spell", that's the thing that has to finish. If you are considering the perceivable occurrence "someone ruffling in the bags", that's what has to finish. Which might or might not be what you want to be. But those are different occurrences.

Let me explain with an example:

When does a 100mt race start? We can say it starts when you hear the referee shoot a blank with the gun, right? The "when the race starts" is an actual stand in for "when i hear a blank going off" if you don't care about paying attention (or can't) to the referee. Because THAT IS THE PERCEIVABLE OCCURRENCE. The rationalization on the abstract is based on a commonly established reasonable moment (well, a little bit more of that in this case) based on a perceivable occurrence. If you don't hear the blank you don't "trigger your reaction", and you are indeed surprised by the fact that everyone else is running and there was no "start"!

In reality, we are attentive to an ENOURMOUS amount of details - like the aforementioned group of people running while you are still waiting for the bang. The Ready Action is the extreme simplification of that awareness. It calls for a very simple trigger. And leaves to each DM the extent of judgement.

By the way: if i'd ever rule for interruptions, i would let the ruling fall under "improvised actions". No real limitation to discuss about there.

So if my trigger is when X starts talking, I have to wait until they finish saying their piece ?

Rulewise? Yes.*

Interesting. I've read the entire thread; those who can only see atomic actions still only see atomic actions, those that see interruptible actions still only see interruptible actions. I don't really see this changing. That said, the thread isn't really for those who already have strong opinions, its for those who don't.

Good. That's why the one strongly opinionated are producing their ideas. (With good i mean, we still haven't gone into namecalling, so something can be of use. :D)

Except readied actions don't care about actions as the trigger. They care about perceptible events. Similar to Naanomi's examples, "I shoot them with my crossbow as they begin talking" shouldn't mean that you have to wait for them to complete a paragraph? Once they begin vocalizing the trigger has occured.

And, as requirement for the reaction to take place, the trigger has to finish before the reaction can be taken. So, Yes. As long as they are still talking the trigger still hasn't finished.*

The problem here with "reacting to beginning casting a spell" seems to me that the less information you have, the less sure you are that you're reacting to the correct thing. "starts to cast a spell" probably visually reads similar to "flips the bird" or "talks with exaggerated hand gestures".

Exactly.

I can ready for any perceivable trigger.

***MAJOR NITPICK :P*** Not really. It has to be an occurrence. You cannot Ready Action with a trigger like "A green pen". There's no occurrence there, even if a green pen is by all reasonable means perceptible.

I ready an action for when someone starts talking. According to you I have to wait till they finish talking to shoot them?

Rulewise, yes*. You wait.
I ready an action for the moment before someone starts talking. I must have perceived that moment, so that's a perceivable occurrence. Do i turn back time?

If you say yes, well thats some free speech in your tables!

Understanding what the rules say and the application of said rules are two VERY different things.

I try to understand what a rule is meant to represent. The Ready Action is meant to put the ability of a person to prepare for an event and be ready to react once that particular event has happened in a way that is "absolutely" true and unmistakeable. It's meant to ease a bit of the edginess of a turn based systems providing a way to mechanically resolve those reactions that are common enough in a game, that cannot be solved during each single turn, but are so varied that require vague rules, all without overcomplicating situations.

To be able to do so, i need to try to read the rule as it is, and make a judgement on that - no matter the absurd results i get.I do not read in what i want a rule to accomplish, and try to mold what there is to my goal.

---

*This doesn't mean that i, as a DM, would not grant leeway. But that is EXACTLY one of the reasons why there is a DM. Rules aren't perfect. Just like the example of the "longer casting time spells" from Max. A DM is there because it's a human, that has a pretty impressively high chance to understand what a player MEANS with what they say, and are able to mediate between said player and how the rules work.

With Lighty, there might always have been the impossibility to see or perceive. That might have been known all along to the characters, but not have been stated clearly enough to the players. It's clear enough what a player wants, and "when the light goes out" is what i would count to be the trigger.
With talking, it seems to mer that the intention is to go "as soon as they utter a word/sound". There's no intention to wait for a possible surrender proposition.
A human is flexible, rules not so much.

[Coffee_Dragon]

(Sidetrack by now, but)

I think there was a misunderstanding in my post.

Whoever rolled highest has the first slot in initiative order. The problem is, if the faster character is a PC and the PC did not initiate combat, does the PC know who did initiate combat? does the PC know how the enemy initiated combat (ie casting a spell)

No, I understood you then, if I understand you now. You're saying the DM is refusing to represent combat as having started until the initiative count reaches that of the aggressor(s), thereby robbing the non-aggressor(s) of any meaning in winning initiative, right? Which is nonsensical, since turns aren't consecutive chunks of time that together linearly make up the round. Every turn overlaps, and initiative decides who takes effective action first. Refusing those who win initiative to act even when they're not surprised reveals a misconception of the whole combat time abstraction and initiative mechanism.

[Unoriginal]

(Sidetrack by now, but)



No, I understood you then, if I understand you now. You're saying the DM is refusing to represent combat as having started until the initiative count reaches that of the aggressor(s), thereby robbing the non-aggressor(s) of any meaning in winning initiative, right? Which is nonsensical, since turns aren't consecutive chunks of time that together linearly make up the round. Every turn overlaps, and initiative decides who takes effective action first. Refusing those who win initiative to act even when they're not surprised reveals a misconception of the whole combat time abstraction and initiative mechanism.

Amen. If the PC wins initiative but can't actually perceive a danger, they're just surprised for this one turn.

[Rukelnikov]

snip

Too long to answer each individually, plus, I have already covered most (if not all) of them on different posts.

But you just said a starts finishes as soon as it starts.

So if the reaction is as soon as the trigger finishes, and the starts finishes as soon as it starts, it means that according to you, the reaction is as soon as the trigger starts.

Is that correct? If no, could you explain how it is not?

The starting of something is instantaneous "when the chronometer starts counting", first it wasn't and then it is, thus it started.

Once it is counting, it has finished beginning to count.

[Rukelnikov]

No, I understood you then, if I understand you now. You're saying the DM is refusing to represent combat as having started until the initiative count reaches that of the aggressor(s), thereby robbing the non-aggressor(s) of any meaning in winning initiative, right? Which is nonsensical, since turns aren't consecutive chunks of time that together linearly make up the round. Every turn overlaps, and initiative decides who takes effective action first. Refusing those who win initiative to act even when they're not surprised reveals a misconception of the whole combat time abstraction and initiative mechanism.

What if they can't perceive the aggressor? A sorcerer casting subtle mind spike for instance in the middle of a street.

[Coffee_Dragon]

What if they can't perceive the aggressor? A sorcerer casting subtle mind spike for instance in the middle of a street.

Well, it seems like the victim would be surprised? Starting from the second round they would be able to act on whatever they know after the first. (Add in inability to be surprised and you get an immovable object/irresistible force problem which is its own headache.)

[NaughtyTiger]

No, I understood you then, if I understand you now. You're saying the DM is refusing to represent combat as having started until the initiative count reaches that of the aggressor(s), thereby robbing the non-aggressor(s) of any meaning in winning initiative, right? Which is nonsensical, since turns aren't consecutive chunks of time that together linearly make up the round. Every turn overlaps, and initiative decides who takes effective action first. Refusing those who win initiative to act even when they're not surprised reveals a misconception of the whole combat time abstraction and initiative mechanism.

ah, i get you. you were speaking in such absolutes it wasn't clear that you meant "efffectively" robbing them of their actions/initiative.

yeah, when a DM says roll initiative but doesn't clearly explain that the orc horde started to attack AND the party doesn't want to throw the first punch, then the DM is effectively robbing the party of their action.
When I was guilty of this as a DM, I didn't realize that is what I was doing.
It certainly didn't feel like I was robbing the players, cuz they could choose to attack. after all, in the meta game, the players knew they were being attacked.

[Rukelnikov]

ah, i get you. you were speaking in such absolutes it wasn't clear that you meant "efffectively" robbing them of their actions/initiative.

yeah, when a DM says roll initiative but doesn't clearly explain that the orc horde started to attack AND the party doesn't want to throw the first punch, then the DM is effectively robbing the party of their action.
When I was guilty of this as a DM, I didn't realize that is what I was doing.
It certainly didn't feel like I was robbing the players, cuz they could choose to attack. after all, in the meta game, the players knew they were being attacked.

But there's still many situations when this expressly turn the initiative roll into spider senses.

A couple of guards detained the PCs, they are in the town square being held at crossbow point, everyone is aware of one another, the PCs are trying to talk their way out of it.

If the GM says the guards fire roll initiative, then, either the guards haven't yet fired, and it will be the PCs starting hostilities (just because I might add, because they've been at gunpoint for a while now), or they keep trying to talk their way out until a guard has fired a shot.

[ProsecutorGodot]

But the absurdity is solely about the content - it's unrelated to the readied action, so it doesn't prove anything (except, maybe, that you've run out of valid arguments.)

(first off, apologies for dredging up a comment so far down in the thread, I haven't had the chance to reply until now)
I made the content absurd because the context allowed me to do so.

That's the problem. You didn't even argue that the DM wouldn't be allowed to do something so absurd like this, you instead argued against "why" he would do something like this. Because he can, under such an interpretation, just to be smart and obnoxious towards his players.

Just like players who would try such a thing are only being smart and obnoxious towards their DM.

You could have just as easily have said "what if the DM gives their NPCs a magic item that can instantly annihilate anyone with no save. Then the NPC takes a readied action and uses it. Isn't that ridiculous?" Yes, yes it is. But it has nothing to do with readied actions. If you want to discuss whether using multiple high-level casters with Finger of Death is fair to the PCs, start a separate thread, don't change the subject to something unrelated like that.

Again, the content of the example is irrelevant. The point was to illustrate that allowing such a trigger for reactions is absurd, looks absurd in practice and makes even players in defense of such a trigger see the extreme as absurd.

If those in defense of this practice are seeing the end result of allowing such a ruling (and this is only the most absurd end result that I could see, there is likely even more absurd scenarios that would be enabled by this) then you're advocating for the doom of your tables enjoyment on this one. People are going to be fighting about how their careful contract-like wording was more precise than the DM's and no one is going to get anything done.

Well, it's definitely not metagaming! You clearly understand the difference in outcomes. "If they reach for their spell component, I do X" is an entirely reasonable, in-universe action a player could logically take in the setting; it's also clearly supported by the rules (and is clearly intended to be supported by the rules!) You're the one who's trying to metagame up some sort of complex reason why it isn't allowed - the DM says "with a readied action, the necromancer interrupts you to..." and you're getting up in his face playing rules-lawyer to prevent it.

It certainly is metagaming to be reacting to a trigger that would start initiative before the initiative has started. It's definitely metagaming to think that your players choice of wording can influence your characters reaction speed to be infinitely fast. Your players wording should not affect your characters abilities if that wording is in direct conflict with both the rules and fiction. If adding "begins" to the trigger is enough to make you react faster in the fiction, everyone would do that to start with and the fact that you are meant to react to and not pre-empt those triggers would be pointless.

"If they reach for their spell component, I do X" is arguably the most reasonable version of this that I've seen proposed yet. You don't know the NPC is casting a spell by reaching for this however and a tricky DM could twist that wording in a way that you never see such a trigger either "they didn't reach for their spell components, they were already in hand (or the spell is only vocal, or somatic, or cast from an item with isn't a component"

Which he would be absolutely within his right to do, if you're arguing that hair-splitting semantics are necessary to achieve a result, your DM can do that as well. You're not going to be happy when he does.

It is useful in certain extremely specific situations (eg. if you're waiting to see what the enemy does, and don't want to act if they do something unexpected.) There's no reason to penalize player creativity by trying to bar it from being used in those situations, especially since first, we know from the Sage Advice answer that interrupting people with a readied action is RAI, second, you've repeatedly failed to come up with either a RAW reason to ban it (unsurprising since it's RAI), and third, you've repeatedly failed to demonstrate any problems that would emerge from allowing it.

If your DM has had you roll initiative in a situation where you aren't sure that the opposition is a threat, you shouldn't have rolled initiative to begin with. If you're attempting to use a similar strategy out of combat, you would determine whether the target was surprised, roll initiative and if they were surprised the outcome would happen exactly as you intended. If they weren't surprised and you rolled higher than them, they could react. If they weren't surprsied and they rolled higher than you, you didn't actually manage to surprise them AND they were faster than you expected. These results all make sense in the fiction.

See above for the example of problems that would arise.

Your arguments are completely incoherent - you swing wildly from "it's overpowered and if you allow it people would do it constantly if they knew they could" to "it's useless and therefore there's no reason to do it." You have to pick one of those two, you can't argue both. (And if you pick the second, as I think you're aware, you've immediately conceded the debate in any practical sense, since it's silly to bar players from doing something completely harmless when we have a Sage Advice suggesting you allow it.)

Whereas the argument to just follow RAI and allow it is extremely straightforward and obvious - it doesn't break anything, it doesn't cause any problems, and players may occasionally be able to find clever ways to use it to take advantage of specific situations where they want to delay their action. Obviously it's situational - readied actions are generally situational - but I don't see the reason to be so opposed to it.

First off, I am on record in this thread for advocating a case by case exception to be made. However, we have no evidence that Ready Action is meant the same allowance as War Magic and Shield Master. Claiming that different reactions shape the intended use of Ready Action isn't accurate.

Second, it's true that if you allow people with the knowledge to do it constantly that it becomes useless. When this has become the general rule at your table your DM is just going to change the rules in a way that doesn't end up aggravating the situation further.

It's overpowered in the sense that people seem to believe that the "cost" of an Action and Reaction is comparable to the "cost" that a spellcaster would have taken to know/use counterspell. Sorcerers sacrifice one of their few spells known, Bards must pick it up using magical secrets, Wizards have to prepare it, Paladins can only acquire it through a single subclass and Rangers can't even get counterspell naturally, they only get a similar effect at level 11 of a specific subclass (which is a deep dive into Ranger, since most campaigns don't stretch past levels 13-16)

But if a readied action Arrow is an effective method of counterspelling, why would any of those spellcasting classes bother.

It's also true that in the vast majority of situations, you could word your Readied Action in a way that doesn't require an interrupt and do the same thing - eg. the "cast when they move next to you, not when they attack" example. But if you require that then you are playing rules-lawyer and demanding metagaming from your players in the wording of their readied actions, aren't you? "I ready an action if someone moves to attack me" is straightforward, clear, and fits the rules.

Whereas "I want to react if someone seems about to attack me" vs. "I want to react after someone attacks me" is an extremely straightforward and obvious distinction that fits the rules as written.

Reacting to movement is a good trigger because movement is incremental. You can interrupt their move easily, both in the rules and in fiction. You can't, however, easily interrupt their action in the same way. There's no evidence to suggest that actions have incremental step processes that can be interrupted in a way that would prevent them from resolving. Movement resolves as soon as you reach the new space.

When you set a trigger "I ready an action if someone moves to attack me" your trigger reads to the DM as "I ready an action if someone moves within a range to attack me" your character doesn't know the difference just because you know the difference as a player.

Likewise, when you set a trigger "I want to react if someone seems about to attack me" is pointless because at this point you're in an initiative order, which should mean that if you are properly in initiative, there are several creatures that already seem like they're about to attack you. You could have taken your action instead.

Telling them "no, it has to be if the enemy moves next to you, because by my interpretation interrupting an action like that isn't allowed" adds pointless quibbling to how players have to word their readied actions.

And creating a specified difference between "begins to cast a spell" and "cast a spell" doesn't? This thread is evidence that it does. Your creative choice of wording shouldn't have an impact on the fiction beyond what a player would have if they shared the same intent but didn't choose that same wording.

You're just trading your example here for an equally infuriating one "No, you don't get to attack first as you intended. Not because the rules say so, but because you didn't word your trigger specifically enough. Tim did, however, so go ahead and take that reaction."

People are going to fight about it. People are fighting about it here.

[BoringInfoGuy]

Spot on. The game putting non-interruption as the default for reactions doesn't include an assumption that nobody's trying their best until the players split the right hairs.

Thank you

You're too late to act when they start. By the time your action is ready, they're already started. Characters in the fiction are not taking turns; they're all going at the same time. Initiative indicates who finishes a fraction of a second first.

If you want to act first (and win initiative), act on your turn. If you wait until another character's turn, your readied action takes place immediately they finish casting their spell (or whatever else you're reacting to).

This is a good point to build on. Since magic does not exist in real life, let’s use a different trigger to bypass the “magic works like x”, “no magic works like y” arguments.

A verbose enemy has been tossing insults against the party along with his attacks and orders to minions.

A couple of players have had enough of the insults.

One says:
“If he insults us again, I’m shooting him with a crossbow.”

The other says “If he starts insulting us again, I hit him with a crossbow.”

The trigger is a perceivable event.

The enemy says “All of you are fools”.

The DM ask both both players attacks if they want to use their readied actions after the insult is finished.

The second player complains that he said he was triggering off the start of the insult. So his attack should go off before the enemy finishes.

At what point did the insult start? The moment the enemy said “All...”.

But when could you TELL that it was an insult? Not at the moment when it first began. At that point, it could have been almost anything. “All of you are dead!” A threat. “All of you, take down the leader!” An order to minions. “All of this only delays the inevitable!” Villainous pontificating. “All I wanted was waffles!!!” Your villain is hungry / angry / crazy.

The start of the insult was the word “All,” but that is only recognizable in retrospect. The second player is trying to target a moment that could ONLY be identified AFTER that moment had already passed.

Now, apply that to using casting a spell as a trigger.

How do you identify the exact moment spell casting begins? Spells have a mixture of verbal, somatic, and material components. Not every spell used all three.

Is the wizard reaching for his component pouch or for a for a potion? Or maybe scratching an itch? Complicating the matter further, casters may be using a focus already in hand in place of a material focus. Is the wizard raising his staff because he is starting a spell and using it as a focus, or lifting it so it won’t drag on the ground as he prepares to move, or to point at who he wants his minion to attack, or is the he casting a spell without any material component at all?

Somatic gestures have the same problem. The wizard begins moving his hand. Is that the wizard starting the somatic gestures of a spell, reaching for a potion, flexing his fingers to loosen them up before he starts the actual somatic components, waving away a gnat, or just doing some random gesture as he chooses the target of his spell without a somatic component?

Ok, how about watching for the verbal component? Almost every spell as some verbal aspect. Still, not easy to note in real time. The wizard is starting to speak. When can you tell that the wizard is saying the words of a spell instead of preparing an insult, or giving orders to a minion, or simply talking to himself? Base it on the moment you hear a word you don’t recognize? Again, how do you know it is not a minion’s name or just a language you don’t speak? Or even if you do speak the language, if you are facing a human wizard and he says something in dwarfish, that could be enough to go “it’s not common - he’s casting!”

Casting a spell is a perceivable event. When someone begins to cast a spell is recognizable only in retrospect.

None of this is an attempt to say that you can’t perceive when someone is casting a spell. (Barring specific exceptions that we will for the moment ignore). Of course you can. So far I have not seen anyone dispute this.

And yes, an enemy casting a spell is certainly a valid trigger for a Readied Action. Again, I’ve seen no one dispute this.

But agreeing to this does not mean that we must also support the idea that you can make the trigger extra specific to override game mechanics. The beginning of something is not necessarily perceivable. Not in the moment at the time. It’s something you figure out when looking back.

Just because you add the word “begins” to your trigger does not force me to rule that your character has suddenly gained the ability to instantly recognize the exact moment the trigger started.

Something largely overlooked so far is that you DON’T have to use the Readied Action when the trigger occurs. There is a moment of decision where you can choose to not react to the trigger after all. This means that a moment exists between recognizing the trigger has happened and deciding to act on it. This works against the idea that a reaction is actually instantaneous.

There is nothing in the Rules As Written or the Rules As Intended to allow being extra specific on your wording will allow you to turn a reaction into an interruption.

“But JC tweeted he would allow a silence spell to be triggered off “Beginning to cast” and used to interrupt a spell being cast. This proves it was RAI.

Didn’t you see that Boring Info Guy?

Yes, I saw that. And I noticed some significant things about it.

1) He did not saw this was something that worked by RAW, but something he would allow as a DM

2) The tweet was from 2015.

3) Sage Advice Compendium was updated in January of 2019.

3a) A recent change in the latest Sage Advice Compendium is that not even JC’s tweets are considered official rule statements. The Sage Advice Compendium is now the ONLY source of official rulings for D&D 5e.

3b) While there are rule clarifications for the Ready action in Sage Advice, using a readied Silence to interrupt a spell and prevent it from taking effect is not included.

3c) Sage Advice talks about 3 rule viewpoints. Rules as Written, Rules as Intended, and Rules as Fun.

Having noted all this, it seems to me that the 2015 tweet was JC talking from a DM using the Rules as Fun perspective. The “I’m going to deliberately override RAW because I like the idea” approach.

Even if you disagree and want to argue that he instead meant it as a RAW / RAI statement, the fact that it is not in the current Sage Advice Compendium means it was later reconsidered and abandoned as a ruling.

[Unoriginal]

What if they can't perceive the aggressor? A sorcerer casting subtle mind spike for instance in the middle of a street.

Then the PCs are surprised.

[Rukelnikov]

Then the PCs are surprised.

Yeah, I made a different example later on (this case is the same though if one of the PCs has Alert)