If a spell must be maintained with Concentration, that fact appears in its Duration entry, and the spell specifies how long you can concentrate on it. You can end Concentration at any time (no action required).
Since "you can end concentration at any time" you should be able to spend exactly zero time concentrating on a spell. Right? By choosing the exact moment you would start concentrating to be the exact same moment you stop, you don't actual concentrate on it. By doing so, you would simply not maintain the spell. As this says to a spell must be maintained with concentration. No concentration = no maintaining. Right?
But you are still casting the spell. So any effect that isn't maintained would transpire, but no ongoing effects would be maintained.
So, if a person was not capable of maintaining concentration, could they still cast a spell that required concentration to maintain? And, if so, it would only be the instantaneous effects, right?
(this isn't about 2 spells at once, but something preventing concentration)
Rollback Post to RevisionRollBack
I'm probably laughing.
It is apparently so hard to program Aberrant Mind and Clockwork Soul spell-swapping into dndbeyond they had to remake the game without it rather than implement it.
I think your interpretation is correct. If you had some sort of special condition that only prevented you from concentrating on spells, I don't think there is anything that would prevent you from casting a spell with concentration. The spell would simply have no duration, as though it were instantaneous. For some spells, you might be able to squeeze value out of it. Immolation, for example, would still deal its initial damage, which is independent of the spell's duration.
Just treat the duration as if it were 0. Any effect that references the duration is then rendered useless. For example, Hideous Laughter could still knock a target prone, but wouldn't incapacitate, not even for an instant.
If you’re incapable of concentrating on a spell for whatever reason, you cannot cast a spell that requires concentration. You must concentrate to begin any part of the effect. Sure, you could immediately end your concentration, but unless you’ve started concentrating, there’s nothing to end.
Likewise, even if you could cast spells in this way, they wouldn’t have any effect. Concentration spells are not instantaneous spells; they may have immediate or initial effects, but they do not have instantaneous effects. A duration of exactly zero means there’s no time for any effect to exist.
tl;dr, you can’t do it, and even if you could, you couldn’t produce an effect.
I'm with Saga. The effect begins by concentrating. You can end as soon as you begin, but if you can't concentrate at all, you can't even begin.
That is interesting. What leads you to believe the effects begins by concentrating? I might have missed it. I only see text in the concentration rules which says you maintain the effect by concentrating. And, well, you can't maintain something that hasn't started. So, if concentration leads to maintaining, there necessarily needs to be something already for it to maintain, no? Anywho, I might have missed what you're referring it.
Rollback Post to RevisionRollBack
I'm probably laughing.
It is apparently so hard to program Aberrant Mind and Clockwork Soul spell-swapping into dndbeyond they had to remake the game without it rather than implement it.
If you’re incapable of concentrating on a spell for whatever reason, you cannot cast a spell that requires concentration. You must concentrate to begin any part of the effect. Sure, you could immediately end your concentration, but unless you’ve started concentrating, there’s nothing to end.
Likewise, even if you could cast spells in this way, they wouldn’t have any effect. Concentration spells are not instantaneous spells; they may have immediate or initial effects, but they do not have instantaneous effects. A duration of exactly zero means there’s no time for any effect to exist.
tl;dr, you can’t do it, and even if you could, you couldn’t produce an effect.
Is this a null vs zero distinction you're making? Start/stop = 0. Can't start = null. And it must return a valid integer? I suppose I can see that. That might be an important insight in this, for sure.
Rollback Post to RevisionRollBack
I'm probably laughing.
It is apparently so hard to program Aberrant Mind and Clockwork Soul spell-swapping into dndbeyond they had to remake the game without it rather than implement it.
I'm with Saga. The effect begins by concentrating. You can end as soon as you begin, but if you can't concentrate at all, you can't even begin.
That is interesting. What leads you to believe the effects begins by concentrating? I might have missed it. I only see text in the concentration rules which says you maintain the effect by concentrating. And, well, you can't maintain something that hasn't started. So, if concentration leads to maintaining, there necessarily needs to be something already for it to maintain, no? Anywho, I might have missed what you're referring it.
They didn't explain it, it is one of those plain language things that are the bane of 5e rules lawyering.
When does the spell effect take place? During the duration. Concentration is the duration. So if you never concentrate, there is no time span (not even instantaneous) for the effect to occur.
I'd say that it's a case of the DM's choice. Personally I'm leaning more towards the camp of if you concentrate on the effects for a zero amount of time there is a zero amount of time that the spell can take effect which leads to zero effect.
Since casting can be interrupted, it stands to reason that there is some element of concentrating going on during the actual casting (but again, we do have the 'plain language' issue). This is also in line with 5E's held casting. If you hold your action to cast a spell you still spend a slot and are concentrating. Anyone who has ever played Baldur's gate knows how satisfying it is to cast magic missile as soon as you see the baddy starting to cast som terrible spell. The 5E equivalent would be, for example, someone holding an attack "for when the spellcaster *starts* casting a spell". It's perfectly reasonable to call for a concentration roll if the held attack hits.
You know what, I'm not going to keep arguing whether concentration spells can be cast without concentration. Or whether or not an effect can occur without a time in which it exists. Or how you could possibly stop concentrating at anytime without being required to start.
Some spells require you to maintain concentration in order to keep their magic active. If you lose concentration, such a spell ends.
By this, I'm with Lyxen. If you need to "maintain concentration in order to keep their magic active", the magic must necessarily already be active for concentration to keep it so. Therefore, you must be able to cast it without concentration. If you cannot maintain concentration, you cannot keep the magic active and it would dissipate immediately after the initial effect.
However, it isn't clearly defined and I could see a DM ruling the other way. I am unaware of any effect which would stop concentration without stopping the ability to cast spells, so I cannot think this would be a very common situation and may not have been considered by the designers.
You know what, I'm not going to keep arguing whether concentration spells can be cast without concentration.
Is this not the place for rules discussions?
Or whether or not an effect can occur without a time in which it exists. Or how you could possibly stop concentrating at anytime without being required to start.
Yeah this is a null vs zero distinction you're making here, which might very well be a valid one. And I would love if you could point to what you're referencing in the rules, it would be great insight into your rationale to know what rules you're talking about. It can be hard to follow someone's rules rationale when they don't tell you what they're referencing. That's a large body of work, just "the rules".
I think Lyxen makes a good point about concentration not being required to cast a spell, only to maintain it once it has been cast. But if your rationale counters that, I'd love to understand it better. Anything whatsoever, in the rules, which states that the concentration is required for the casting of the spell, and not the maintaining of the spell. I've looked a few times now and I'm not seeing what you seem to be seeing.
Again, and I can't stress this enough, this is not seeking some loophole about concentration spells while already concentrating, that is worded very specifically that if you even cast the second spell the first concentration ends. This is instead asking about a situation in which someone simply is unable to concentrate whatsoever.
Rollback Post to RevisionRollBack
I'm probably laughing.
It is apparently so hard to program Aberrant Mind and Clockwork Soul spell-swapping into dndbeyond they had to remake the game without it rather than implement it.
I'd say that it's a case of the DM's choice. Personally I'm leaning more towards the camp of if you concentrate on the effects for a zero amount of time there is a zero amount of time that the spell can take effect which leads to zero effect.
Since casting can be interrupted, it stands to reason that there is some element of concentrating going on during the actual casting (but again, we do have the 'plain language' issue). This is also in line with 5E's held casting. If you hold your action to cast a spell you still spend a slot and are concentrating. Anyone who has ever played Baldur's gate knows how satisfying it is to cast magic missile as soon as you see the baddy starting to cast som terrible spell. The 5E equivalent would be, for example, someone holding an attack "for when the spellcaster *starts* casting a spell". It's perfectly reasonable to call for a concentration roll if the held attack hits.
I love where you're going with this and I might even add something like that in my homebrew. The idea of spells always being at risk if enemies use their actions to try to interrupt them is just fantastic in my opinion. I think where it breaks down in rules as written is because if casting any and all spells used concentration then even non-concentration spell casts would interrupt ongoing concentration spells. So if you were maintaining a spell, you'd simply be unable to cast any other spell without losing your ongoing one. That'd be a pretty devastating nerf to spellcasters, across the board. Better carry a crossbow! Hahaha.
Edit:
Your post made me realize I had been neglecting gleaning any insight from that readied action text though, so I pulled it up:
When you ready a spell, you cast it as normal but hold its energy, which you release with your reaction when the trigger occurs. To be readied, a spell must have a casting time of 1 action, and holding onto the spell's magic requires concentration. If your concentration is broken, the spell dissipates without taking effect.
And it turns out there is some interesting stuff going on here!
1. What is immediately clear is if you can't concentrate then for sure you cannot hold a spell. You'd cast it but the energy would immediately dissipate while you where trying to hold it back, since holding it back requires concentration.
2. As for our question: Whenever you ready a spell, you cast it with your action. So it is for sure cast normally.
3. Holding that energy back, keeping it from going off, that is what requires your concentration. But, keep in mind... we've cast the spell at this point.
4. So if being able to cast a concentration spell required concentration to cast it, you'd be unable to hold it, because you can't concentrate on the spell and on holding the spell back at the same time. So the concentration on the spell must be when it goes into effect, allowing you to seamlessly transition from concentrating on holding it back to concentrating on maintaining its effect.
It is apparently so hard to program Aberrant Mind and Clockwork Soul spell-swapping into dndbeyond they had to remake the game without it rather than implement it.
Personally I'm leaning more towards the camp of if you concentrate on the effects for a zero amount of time there is a zero amount of time that the spell can take effect which leads to zero effect.
And then zero time does not mean zero effect, see instantaneous spells.
Zero time is not the same as instantaneous, so that's irrelevant.
Since casting can be interrupted, it stands to reason that there is some element of concentrating going on during the actual casting (but again, we do have the 'plain language' issue).
"A spell's duration is the length of time the spell persists." A spell cannot be said to persist if it has not been cast yet, so the duration starts only after the spell has been cast, and concentration is required only during the duration.
And if a spell persists for zero time it has zero time to persist.
This is also in line with 5E's held casting. If you hold your action to cast a spell you still spend a slot and are concentrating.
You have already cast the spell, actually : "When you ready a spell, you cast it as normal", it's just the release which is held, and this is the part that requires concentration: "holding onto the spell's magic requires concentration".
You still need to concentrate.
Anyone who has ever played Baldur's gate knows how satisfying it is to cast magic missile as soon as you see the baddy starting to cast som terrible spell. The 5E equivalent would be, for example, someone holding an attack "for when the spellcaster *starts* casting a spell". It's perfectly reasonable to call for a concentration roll if the held attack hits.
This is not in the rules, as pointed out above, the duration starts at the end of the casting, not at the start (see above, but also see spells with casting time greater than 1 action: In that case, you need concentration to maintain the casting, but the duration still starts after the actual casting). I'm not saying it's not a nice rule with BG and all, but for me it's not RAW.
I never claimed it was RAW but good for you. Also, if we go by your interpretation of RAW, if the effect only takes place during the duration of the spell and the duration of the spell is zero, there is no time for the effect to take place.
I think Lyxen makes a good point about concentration not being required to cast a spell, only to maintain it once it has been cast. But if your rationale counters that, I'd love to understand it better. Anything whatsoever, in the rules, which states that the concentration is required for the casting of the spell, and not the maintaining of the spell. I've looked a few times now and I'm not seeing what you seem to be seeing.
Sure. The rules for readying spells (PHB p. 193) implies that casting a spell holds some form of concentration. But as been mentioned, there isn't really a clear answer in the rules so one would have to go with "plain language" solution. If there is no time for the spell to take effect, there is possibility for it to take effect.
Since casting can be interrupted, it stands to reason that there is some element of concentrating going on during the actual casting (but again, we do have the 'plain language' issue). This is also in line with 5E's held casting.
I think you are taking the "plain language" thing a bit far here. Yes there is some sort of mental effort taking place when casting a spell but I see no reason that that would equate to "concentration" in the meaning that "concentration" is used within the rules.
This is also in line with 5E's held casting. If you hold your action to cast a spell you still spend a slot and are concentrating. Anyone who has ever played Baldur's gate knows how satisfying it is to cast magic missile as soon as you see the baddy starting to cast som terrible spell. The 5E equivalent would be, for example, someone holding an attack "for when the spellcaster *starts* casting a spell". It's perfectly reasonable to call for a concentration roll if the held attack hits.
That's because holding a spell doesn't work that way. When you hold a spell the rules say that you cast the spell as normal but hold its effects until the trigger happens. And that makes it fully logical that you require concentration while holding it and lose the spell slot even if your concentration is broken before the trigger takes place.
And I think that this clinches it for me actually, I see no reason why any instant effects of a spell wouldn't take place even if you are stopped from concentrating on spells. For most spells that use concentration it means that nothing happens but for some (like most wall spells) you'd still get some benefits.
Zero time is not the same as instantaneous, so that's irrelevant.
I would very much disagree. Instantaneous means occurring in an instant, and an instant is one specific point in time with no duration, which is the same as zero duration.
And I think that this clinches it for me actually, I see no reason why any instant effects of a spell wouldn't take place even if you are stopped from concentrating on spells. For most spells that use concentration it means that nothing happens but for some (like most wall spells) you'd still get some benefits.
We aren't talking about spells that have instant effects, we are talking about spells that have durations.
Sure. The rules for readying spells (PHB p. 193) implies that casting a spell holds some form of concentration. But as been mentioned, there isn't really a clear answer in the rules so one would have to go with "plain language" solution. If there is no time for the spell to take effect, there is possibility for it to take effect.
No no. Casting it doesn't, holding it does. That's the crux of the distinction we're drawing here. The rules for holding it tells you that you cast the spell upfront, straight away, right when you take your action to hold on your own turn, it is the holding the energy that takes the concentration until you release that spell energy with your reaction.
What is of interesting note here is that this indirectly shows us the answer.
See, if you hold an action to cast a Bless spell (or anything with concentration), holding that spell energy back requires concentration. And you must maintain that concentration until you release the spell effect with your reaction. BUT, if the cast-requires-concentration rationale was applied here, then casting bless also requires concentration. You'd be unable to concentrate on both holding the spell energy back and also on maintaining the spell.
So that can't be how it works. It has to be that the spell effect must be in effect for it to be maintained by concentration. I think this is the smoking gun.
Rollback Post to RevisionRollBack
I'm probably laughing.
It is apparently so hard to program Aberrant Mind and Clockwork Soul spell-swapping into dndbeyond they had to remake the game without it rather than implement it.
Zero time is not the same as instantaneous, so that's irrelevant.
I would very much disagree. Instantaneous means occurring in an instant, and an instant is one specific point in time with no duration, which is the same as zero duration.
Both by RAW and grammatically you are wrong. An "instant" is still an amount of time which is not the same as "zero time". That part is irrelevant though since, as Lyxen pointed out, "A spell's duration is the length of time the spell persists." If that amount of time is zero, it persists for zero time. There is nothing in the RAW that says that changing the duration of a spell's time to zero changes the duration from "Concentration" to "Instantenous" as far as I know.
Zero time is not the same as instantaneous, so that's irrelevant.
I would very much disagree. Instantaneous means occurring in an instant, and an instant is one specific point in time with no duration, which is the same as zero duration.
Both by RAW and grammatically you are wrong. An "instant" is still an amount of time which is not the same as "zero time". That part is irrelevant though since, as Lyxen pointed out, "A spell's duration is the length of time the spell persists." If that amount of time is zero, it persists for zero time. There is nothing in the RAW that says that changing the duration of a spell's time to zero changes the duration from "Concentration" to "Instantenous" as far as I know.
This is a 'lost in the weeds' tangent but what you're looking for is the distinction between zero and null.
Zero is an instant. Null is not one.
They're very similar concepts and knowing the difference take some mental effort, the idea of null always makes my head feel fuzzy for some reason. Essentially, Zero is a number. Just like any other number. It is a point. A coordinate in time, so to speak. But Null is the absence of a coordinate. The absence of a point.
Like if you had a test and the question was
1-1=
If you write 0 you get marked correct. If you leave it blank you get marked incorrect.
Blank is null. Null is not zero.
So. If something exists for 0 seconds, it is 'instantaneous'. But if it exists for null seconds it doesn't exist.
Rollback Post to RevisionRollBack
I'm probably laughing.
It is apparently so hard to program Aberrant Mind and Clockwork Soul spell-swapping into dndbeyond they had to remake the game without it rather than implement it.
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Since "you can end concentration at any time" you should be able to spend exactly zero time concentrating on a spell. Right? By choosing the exact moment you would start concentrating to be the exact same moment you stop, you don't actual concentrate on it. By doing so, you would simply not maintain the spell. As this says to a spell must be maintained with concentration. No concentration = no maintaining. Right?
But you are still casting the spell. So any effect that isn't maintained would transpire, but no ongoing effects would be maintained.
So, if a person was not capable of maintaining concentration, could they still cast a spell that required concentration to maintain? And, if so, it would only be the instantaneous effects, right?
(this isn't about 2 spells at once, but something preventing concentration)
I'm probably laughing.
It is apparently so hard to program Aberrant Mind and Clockwork Soul spell-swapping into dndbeyond they had to remake the game without it rather than implement it.
The spell only lasts as long as you concentrate on it. After that, it dissipates. And you can only concentrate on one spell at a time.
I live with several severe autoimmune conditions. If I don’t get back to you right away, it’s probably because I’m not feeling well.
I think your interpretation is correct. If you had some sort of special condition that only prevented you from concentrating on spells, I don't think there is anything that would prevent you from casting a spell with concentration. The spell would simply have no duration, as though it were instantaneous. For some spells, you might be able to squeeze value out of it. Immolation, for example, would still deal its initial damage, which is independent of the spell's duration.
Just treat the duration as if it were 0. Any effect that references the duration is then rendered useless. For example, Hideous Laughter could still knock a target prone, but wouldn't incapacitate, not even for an instant.
If you’re incapable of concentrating on a spell for whatever reason, you cannot cast a spell that requires concentration. You must concentrate to begin any part of the effect. Sure, you could immediately end your concentration, but unless you’ve started concentrating, there’s nothing to end.
Likewise, even if you could cast spells in this way, they wouldn’t have any effect. Concentration spells are not instantaneous spells; they may have immediate or initial effects, but they do not have instantaneous effects. A duration of exactly zero means there’s no time for any effect to exist.
tl;dr, you can’t do it, and even if you could, you couldn’t produce an effect.
I'm with Saga. The effect begins by concentrating. You can end as soon as you begin, but if you can't concentrate at all, you can't even begin.
That is interesting. What leads you to believe the effects begins by concentrating? I might have missed it. I only see text in the concentration rules which says you maintain the effect by concentrating. And, well, you can't maintain something that hasn't started. So, if concentration leads to maintaining, there necessarily needs to be something already for it to maintain, no? Anywho, I might have missed what you're referring it.
I'm probably laughing.
It is apparently so hard to program Aberrant Mind and Clockwork Soul spell-swapping into dndbeyond they had to remake the game without it rather than implement it.
Is this a null vs zero distinction you're making? Start/stop = 0. Can't start = null. And it must return a valid integer? I suppose I can see that. That might be an important insight in this, for sure.
I'm probably laughing.
It is apparently so hard to program Aberrant Mind and Clockwork Soul spell-swapping into dndbeyond they had to remake the game without it rather than implement it.
They didn't explain it, it is one of those plain language things that are the bane of 5e rules lawyering.
When does the spell effect take place? During the duration. Concentration is the duration. So if you never concentrate, there is no time span (not even instantaneous) for the effect to occur.
I'd say that it's a case of the DM's choice. Personally I'm leaning more towards the camp of if you concentrate on the effects for a zero amount of time there is a zero amount of time that the spell can take effect which leads to zero effect.
Since casting can be interrupted, it stands to reason that there is some element of concentrating going on during the actual casting (but again, we do have the 'plain language' issue). This is also in line with 5E's held casting. If you hold your action to cast a spell you still spend a slot and are concentrating.
Anyone who has ever played Baldur's gate knows how satisfying it is to cast magic missile as soon as you see the baddy starting to cast som terrible spell. The 5E equivalent would be, for example, someone holding an attack "for when the spellcaster *starts* casting a spell". It's perfectly reasonable to call for a concentration roll if the held attack hits.
You know what, I'm not going to keep arguing whether concentration spells can be cast without concentration. Or whether or not an effect can occur without a time in which it exists. Or how you could possibly stop concentrating at anytime without being required to start.
By this, I'm with Lyxen. If you need to "maintain concentration in order to keep their magic active", the magic must necessarily already be active for concentration to keep it so. Therefore, you must be able to cast it without concentration. If you cannot maintain concentration, you cannot keep the magic active and it would dissipate immediately after the initial effect.
However, it isn't clearly defined and I could see a DM ruling the other way. I am unaware of any effect which would stop concentration without stopping the ability to cast spells, so I cannot think this would be a very common situation and may not have been considered by the designers.
Is this not the place for rules discussions?
Yeah this is a null vs zero distinction you're making here, which might very well be a valid one. And I would love if you could point to what you're referencing in the rules, it would be great insight into your rationale to know what rules you're talking about. It can be hard to follow someone's rules rationale when they don't tell you what they're referencing. That's a large body of work, just "the rules".
I think Lyxen makes a good point about concentration not being required to cast a spell, only to maintain it once it has been cast. But if your rationale counters that, I'd love to understand it better. Anything whatsoever, in the rules, which states that the concentration is required for the casting of the spell, and not the maintaining of the spell. I've looked a few times now and I'm not seeing what you seem to be seeing.
Again, and I can't stress this enough, this is not seeking some loophole about concentration spells while already concentrating, that is worded very specifically that if you even cast the second spell the first concentration ends. This is instead asking about a situation in which someone simply is unable to concentrate whatsoever.
I'm probably laughing.
It is apparently so hard to program Aberrant Mind and Clockwork Soul spell-swapping into dndbeyond they had to remake the game without it rather than implement it.
I love where you're going with this and I might even add something like that in my homebrew. The idea of spells always being at risk if enemies use their actions to try to interrupt them is just fantastic in my opinion. I think where it breaks down in rules as written is because if casting any and all spells used concentration then even non-concentration spell casts would interrupt ongoing concentration spells. So if you were maintaining a spell, you'd simply be unable to cast any other spell without losing your ongoing one. That'd be a pretty devastating nerf to spellcasters, across the board. Better carry a crossbow! Hahaha.
Edit:
Your post made me realize I had been neglecting gleaning any insight from that readied action text though, so I pulled it up:
And it turns out there is some interesting stuff going on here!
1. What is immediately clear is if you can't concentrate then for sure you cannot hold a spell. You'd cast it but the energy would immediately dissipate while you where trying to hold it back, since holding it back requires concentration.
2. As for our question: Whenever you ready a spell, you cast it with your action. So it is for sure cast normally.
3. Holding that energy back, keeping it from going off, that is what requires your concentration. But, keep in mind... we've cast the spell at this point.
4. So if being able to cast a concentration spell required concentration to cast it, you'd be unable to hold it, because you can't concentrate on the spell and on holding the spell back at the same time. So the concentration on the spell must be when it goes into effect, allowing you to seamlessly transition from concentrating on holding it back to concentrating on maintaining its effect.
I'm probably laughing.
It is apparently so hard to program Aberrant Mind and Clockwork Soul spell-swapping into dndbeyond they had to remake the game without it rather than implement it.
Zero time is not the same as instantaneous, so that's irrelevant.
And if a spell persists for zero time it has zero time to persist.
You still need to concentrate.
I never claimed it was RAW but good for you. Also, if we go by your interpretation of RAW, if the effect only takes place during the duration of the spell and the duration of the spell is zero, there is no time for the effect to take place.
Sure. The rules for readying spells (PHB p. 193) implies that casting a spell holds some form of concentration. But as been mentioned, there isn't really a clear answer in the rules so one would have to go with "plain language" solution. If there is no time for the spell to take effect, there is possibility for it to take effect.
I think you are taking the "plain language" thing a bit far here. Yes there is some sort of mental effort taking place when casting a spell but I see no reason that that would equate to "concentration" in the meaning that "concentration" is used within the rules.
That's because holding a spell doesn't work that way. When you hold a spell the rules say that you cast the spell as normal but hold its effects until the trigger happens. And that makes it fully logical that you require concentration while holding it and lose the spell slot even if your concentration is broken before the trigger takes place.
And I think that this clinches it for me actually, I see no reason why any instant effects of a spell wouldn't take place even if you are stopped from concentrating on spells. For most spells that use concentration it means that nothing happens but for some (like most wall spells) you'd still get some benefits.
I would very much disagree. Instantaneous means occurring in an instant, and an instant is one specific point in time with no duration, which is the same as zero duration.
We aren't talking about spells that have instant effects, we are talking about spells that have durations.
No no. Casting it doesn't, holding it does. That's the crux of the distinction we're drawing here. The rules for holding it tells you that you cast the spell upfront, straight away, right when you take your action to hold on your own turn, it is the holding the energy that takes the concentration until you release that spell energy with your reaction.
What is of interesting note here is that this indirectly shows us the answer.
See, if you hold an action to cast a Bless spell (or anything with concentration), holding that spell energy back requires concentration. And you must maintain that concentration until you release the spell effect with your reaction. BUT, if the cast-requires-concentration rationale was applied here, then casting bless also requires concentration. You'd be unable to concentrate on both holding the spell energy back and also on maintaining the spell.
So that can't be how it works. It has to be that the spell effect must be in effect for it to be maintained by concentration. I think this is the smoking gun.
I'm probably laughing.
It is apparently so hard to program Aberrant Mind and Clockwork Soul spell-swapping into dndbeyond they had to remake the game without it rather than implement it.
Both by RAW and grammatically you are wrong. An "instant" is still an amount of time which is not the same as "zero time". That part is irrelevant though since, as Lyxen pointed out, "A spell's duration is the length of time the spell persists." If that amount of time is zero, it persists for zero time. There is nothing in the RAW that says that changing the duration of a spell's time to zero changes the duration from "Concentration" to "Instantenous" as far as I know.
This is a 'lost in the weeds' tangent but what you're looking for is the distinction between zero and null.
Zero is an instant. Null is not one.
They're very similar concepts and knowing the difference take some mental effort, the idea of null always makes my head feel fuzzy for some reason. Essentially, Zero is a number. Just like any other number. It is a point. A coordinate in time, so to speak. But Null is the absence of a coordinate. The absence of a point.
Like if you had a test and the question was
1-1=
If you write 0 you get marked correct. If you leave it blank you get marked incorrect.
Blank is null. Null is not zero.
So. If something exists for 0 seconds, it is 'instantaneous'. But if it exists for null seconds it doesn't exist.
I'm probably laughing.
It is apparently so hard to program Aberrant Mind and Clockwork Soul spell-swapping into dndbeyond they had to remake the game without it rather than implement it.