A wizard bladesinger can duel wield.

[Sir cryosin]

I was reading my book. And as the requirements for the blade song States and this is word for word out of the book. Starting at 2nd level you can invoke a secret Elven magic call the bloodsong provided that you aren't wearing medium or heavy armor or using a shield at Grace's you with Supernatural speed agility and focus you can use a bonus action to start the blade song which lasts for 1 minute it ends early if you are incapacitated if you gone medium or heavy armor or a shield OR IF YOU USE TWO HANDS TO MAKE AN ATTACK WITH A WEAPON. with that reading it say if you make a attack with two hands aka greatsword versatile weapons. Or am I just reading this wrong if so please tell me were I went wrong.

[Goodberry]

That's absolutely correct. Dual-wielding fits perfectly with the Bladesinger's theme.

[Quintessence]

You are correct, Bladesingers can dual wield however it still has all the dual wield problems :(

[Grod_The_Giant]

You are correct, Bladesingers can dual wield however it still has all the dual wield problems :(
Although they're not as bad off as most, since they can get +Int to damage and can use spells like Enlarge or Magic Weapon to further increase damage-per-hit.

[Easy_Lee]

Seems to me that you're reading it right; duel-wielding dual-wielding two-weapon fighting doesn't prevent the bladesong feature from working.

You'd probably need Warcaster to make it viable.

[Mandragola]

As I see it the main reason not to dual wield is that it means both your hands are full, so you can't counterspell. There are obviously plenty of times when this isn't an issue though.

One thing you can't do while bladesinging is fire a longbow, annoyingly. That does come under the heading of using two hands to attack with a weapon. You can still fire a longbow twice when not using a weapon though, and it might well be a better option than casting firebolts - though not by much. It's cool if you happen to find a nice magic bow that nobody else wants.

[Grod_The_Giant]

As I see it the main reason not to dual wield is that it means both your hands are full, so you can't counterspell. There are obviously plenty of times when this isn't an issue though.

One thing you can't do while bladesinging is fire a longbow, annoyingly. That does come under the heading of using two hands to attack with a weapon. You can still fire a longbow twice when not using a weapon though, and it might well be a better option than casting firebolts - though not by much. It's cool if you happen to find a nice magic bow that nobody else wants.
That's what Crossbow Expert is for! Combine with Flame Arrows for added fun.

[Mandragola]

That's what Crossbow Expert is for! Combine with Flame Arrows for added fun.

Well ok, though as far as I can tell only drow bladesingers would be proficient with hand crossbows for this purpose - unless you MC of course. And the damage you'd do would barely beat firebolt at this point.

[Fflewddur Fflam]

I'm right in thinking you can't Booming Blade or Green-Flame Blade and then do an off-hand attack as a bonus action, right? I'm pretty sure that requires taking an attack action first, and of course doing BB or GFB is casting a spell, not taking an attack action.

[Quintessence]

Although they're not as bad off as most, since they can get +Int to damage and can use spells like Enlarge or Magic Weapon to further increase damage-per-hit.

Very true, oddly enough they might be one of the best at dual wielding.

[Foxhound438]

I'm right in thinking you can't Booming Blade or Green-Flame Blade and then do an off-hand attack as a bonus action, right? I'm pretty sure that requires taking an attack action first, and of course doing BB or GFB is casting a spell, not taking an attack action.

Correct.

And for the OP, Dual Weilding is pretty much the way to go for bladesingers; similar to PAM being the way to go for bladelocks. Get yourself a 1 level dip in fighter for the fighting style and possibly armor proficiency, and you're set. A bonus action attack with 2 mods to damage and possibly an extra die from enlarge at earlier levels is a decent plan in my eyes.

Feats you would want are Dual Wielder and War Caster. This way you can use two d8 weapons and cast V,S spells without having to juggle objects.

[Dalebert]

Although they're not as bad off as most, since they can get +Int to damage and can use spells like Enlarge or Magic Weapon to further increase damage-per-hit.

They don't get to add Int to damage.

[DivisibleByZero]

They don't get to add Int to damage.

They do at level 14

[Dalebert]

They do at level 14

My bad. I guess I never expected to get there with mine. :smallconfused:

[the secret fire]

My bad. I guess I never expected to get there with mine. :smallconfused:

It's more or less a drop in the bucket when you finally get it, though it at least gives you a clear reason to use your extra attack rather than just automatically going with an SCAG cantrip.

This is something that has always mystified me about the bladesinger. The class came out in the same book as the SCAG cantrips...and yet the developers don't seem to have understood that their new cantrips rendered the class' extra attack at 6th level (which I'm sure they thought was a sh-t hot ability when they put it in there) largely irrelevant because it is not clearly better (and from 11 -> 13, pretty much strictly worse) than using a cantrip with a single attack. Just a sort of weird disconnect in the development of the class.

[Dalebert]

I wouldn't say the cantrips are clearly better necessarily. It's all-or-nothing with one hit versus an extra chance to hit and do some damage. If you're a BS combined with rogue, an effective combo IMHO, the extra attack is another chance to land sneak attack.

[Mandragola]

I agree that the level 14 +int to damage thing isn't that significant. By all means dual wield at that point if you like. The issue is that at level 14 you're probably casting a proper spell, of up to 7th level, as your action. Casting a cantrip or doing a melee attack just isn't that significant compared. It's what you'll be doing on turns when you're not really under pressure as a party, so it's a nice to have ability but not something that significant.

The significant things for me about the bladesinger are having a great AC and concentration save. If you cap your int at lvl 8 and get resilient constitution at 12, you should very rarely fail concentration while bladesinging. Remaining ASIs in dex or con should help even more.

I guess this does open up the option for you to cast improved invisibility on yourself and chop things up. But don't expect to ever do comparable melee damage to a paladin or something like that. The cool thing is being a wizard who can cast wish, but isn't crunchy and helpless if the bad guys get to him. Plus maybe some rapier work at low levels.

It's for this reason that I'd never multiclass as a fighter/bladesinger, even for stuff like the dual wield fighting style. You're delaying your spells for a nice to have ability - not something that improves your ability at your main job. And of course if you're MCd as a fighter you don't need half the features of bladesinging any more. You can jus wear armour and a shield and have proficiency with con saves.

[DivisibleByZero]

War Caster to dual wield, Mobility to become a skirmisher, and Tough to get Fighter HP are all more valuable to a Bladesinger than either the Dual Wielder or Resilient feats.
Just my not so humble opinion.
Resilient is truly a waste here. You already get Int to that save when you need it, which is about equivalent to proficiency, and War Caster helps even more by granting advantage. Because it has even more going for it than that, including not needing an hand free which allows dual wielding, and being able to exchange an OA for a spell instead, War Caster is inarguably better than Resilient for a Bladesinger.
If you take Resilient on your BS, you are doing it wrong.

[Grod_The_Giant]

It's more or less a drop in the bucket when you finally get it, though it at least gives you a clear reason to use your extra attack rather than just automatically going with an SCAG cantrip.

This is something that has always mystified me about the bladesinger. The class came out in the same book as the SCAG cantrips...and yet the developers don't seem to have understood that their new cantrips rendered the class' extra attack at 6th level (which I'm sure they thought was a sh-t hot ability when they put it in there) largely irrelevant because it is not clearly better (and from 11 -> 13, pretty much strictly worse) than using a cantrip with a single attack. Just a sort of weird disconnect in the development of the class.
It's just a poorly designed subclass-- a mishmash of abilities that aren't really on-point for a mage-warrior. You're basically just a Wizard who gets massive AC twice/short rest.

[the secret fire]

I wouldn't say the cantrips are clearly better necessarily. It's all-or-nothing with one hit versus an extra chance to hit and do some damage. If you're a BS combined with rogue, an effective combo IMHO, the extra attack is another chance to land sneak attack.

The problem is that if you're advancing to level six as a wizard (presumably pretty early in your career), your sneak attack isn't going to be that great, either. I prefer only a two level dip in bladesinger for a rogue (generally AT), but a two level dip can be really good.

[Quintessence]

It's just a poorly designed subclass-- a mishmash of abilities that aren't really on-point for a mage-warrior. You're basically just a Wizard who gets massive AC twice/short rest.

True story, better off being a dragon sorcerer in melee getting +cha to greenflame blade.

[MaxWilson]

I wouldn't say the cantrips are clearly better necessarily. It's all-or-nothing with one hit versus an extra chance to hit and do some damage. If you're a BS combined with rogue, an effective combo IMHO, the extra attack is another chance to land sneak attack.

Also, the extra attack (combined with Athletics Expertise from Rogue) lets you do some nifty control. Push Prone + Grapple is probably better at protecting the squishies than Booming Blade is, and the extra damage from dual wielding is convenient. On subsequent rounds you can kill it with advantage using Greenflame Blade or regular attacks, as you prefer.

Yes, I know it feels odd to have a wizard protecting "the squishies", but a Bladesinger really isn't squishy.

P.S. Compare this to a Fighter 1/Wizard X (e.g. Illusionist). He's not squishy, but unlike the Rogue/Bladesinger he's not that great at physical control via Grapple/Prone. The Bladesinger's edge is due to Expertise + Extra Attack.

[Quintessence]

Also, the extra attack (combined with Athletics Expertise from Rogue) lets you do some nifty control. Push Prone + Grapple is probably better at protecting the squishies than Booming Blade is, and the extra damage from dual wielding is convenient. On subsequent rounds you can kill it with advantage using Greenflame Blade or regular attacks, as you prefer.

Yes, I know it feels odd to have a wizard protecting "the squishies", but a Bladesinger really isn't squishy.

It still has the awful hit die of the wizard..

[RickAllison]

Also, the extra attack (combined with Athletics Expertise from Rogue) lets you do some nifty control. Push Prone + Grapple is probably better at protecting the squishies than Booming Blade is, and the extra damage from dual wielding is convenient. On subsequent rounds you can kill it with advantage using Greenflame Blade or regular attacks, as you prefer.

Yes, I know it feels odd to have a wizard protecting "the squishies", but a Bladesinger really isn't squishy.

Also, DMs that allow the alternative actions from the DMG allow for great synergy with the Disarm feature. Might not be w great strategy for a fighter with his hands full, but the wizard can combine it with Darkness or the like to more permanently remove the weapon from combat. My wizard only has one attack, but loves to combine it with Watery Sphere. Yes, go get your sword in the swirling vortex of water...

[Klorox]

Yes, a bladesinger can dual wield.

As mentioned above, using one weapon leaves open the option to counter spell, as well as the unmentioned option to cast shield, or misty step.

Unless you have warcaster, but that is a hard investment to make.

The bladesinger needs INT and DEX as high as possible (and it's virtually unplayable with a non-versatile weapon), as quickly as possible. If you're using point buy, that means your ASI's are spoken for until level 16.

[MaxWilson]

It still has the awful hit die of the wizard..

Generally shouldn't matter though, since healing is so prevalent in 5E. A Cure Wounds that restores 20 HP of damage, restores 20 HP of damage, regardless of whether those 20 HP are coming off of d12 HD or d6 HD.

If your whole group is relying on HD healing it will matter a bit, and if you get in a really tough fight where you get down to near-zero HP it may matter a fair bit (especially since going unconscious disables your Bladesong). Scenarios like these are where Inspiring Leader and the Aid spell are nice, but if your DM isn't a killer DM they also ought to be rare for a Bladesinger (especially post-Song of Defense).

In the more common, attrition-grind scenarios, the Lore Bard will have an easier time healing the 20 HP of damage the Bladesinger took than the 30 HP of damage the Barbarian took. Remember that Aura of Vitality heals about 70 HP of damage per casting.

TL;DR: HP are mostly fungible.

[the secret fire]

Generally shouldn't matter though, since healing is so prevalent in 5E. A Cure Wounds that restores 20 HP of damage, restores 20 HP of damage, regardless of whether those 20 HP are coming off of d12 HD or d6 HD.

If your whole group is relying on HD healing it will matter a bit, and if you get in a really tough fight where you get down to near-zero HP it may matter a fair bit (especially since going unconscious disables your Bladesong). Scenarios like these are where Inspiring Leader and the Aid spell are nice, but if your DM isn't a killer DM they also ought to be rare for a Bladesinger (especially post-Song of Defense).

In the more common, attrition-grind scenarios, the Lore Bard will have an easier time healing the 20 HP of damage the Bladesinger took than the 30 HP of damage the Barbarian took. Remember that Aura of Vitality heals about 70 HP of damage per casting.

TL;DR: HP are mostly fungible.

This is true, and I agree with you that the bladesinger can still be an effective melee combatant without a ton of hit points. I find that the two level bladesinger dip on a rogue works so well at least in part because the class is so easily able to control when and how much damage it takes once it has uncanny dodge, evasion, and the ability to spam shield. This combination makes it really unlikely that you're going to get surprised by some massive spike of HP damage that just knocks you the f- out, and you're virtually immune to shoving and grappling oopsies while bladesinging if you take expertise in acrobatics (which I think is a really good idea at 6th level Rogue). So you can stay on the front lines and push the edges of what a low-HP melee character can usually handle more than with many other combinations/classes.

[MaxWilson]

I'm skeptical of Bladesinger 2/Rogue X mainly because your Int is going almost entirely to "waste". Unless you're thinking of an Arcane Trickster? I suppose I could see some point to that, though you're still stuck with low-level spells.

Bladesinger 10/Rogue 10 or something similar is a lot more plausible in my eyes. Rogues are front-loaded anyway.

[the secret fire]

I'm skeptical of Bladesinger 2/Rogue X mainly because your Int is going almost entirely to "waste". Unless you're thinking of an Arcane Trickster? I suppose I could see some point to that, though you're still stuck with low-level spells.

Bladesinger 10/Rogue 10 or something similar is a lot more plausible in my eyes. Rogues are front-loaded anyway.

Yes, I was thinking of an arcane trickster. Rogues aren't all that front-loaded, imo. They don't get their spike of ASIs until 8->10->12, and Reliable Talent is really good, as is Magical Ambush at AT 9. Going AT 1->12, basically every level is strong except level 6. Getting loads of spells is not really the point. It's primarily a Rogue, on which you throw Sentinel at Rogue 4, and then just pimp out the stats (starting as a wizard and taking Resilient: Dex on a 17 starting Dex at Rogue 8 - you're an elf). It's an impossible-to-hit dervish in melee that you can't not target without risking AoO sneak attacks. Dependent on having a buddy to use Sentinel to its fullest potential, but also well capable in one-on-one combat with owl familiar/booming blade/cunning action shenanigans, at least until the owl gets vaporized. Also quite good at kiting, with the extra 10' movement during bladesong, the ability to cast Longstrider and the ability to gain advantage at range through the owl or Versatile Trickster.

Once you've gotten to BS 2/AT 12, I kinda feel like just continuing on as a Rogue is your best bet for the 3rd level spells that come online at 13th (Hypnotic Pattern) and 14th level (Counterspell), Blindsight, and the continued SA progression mostly (admittedly, the AT's high-level features aren't all that and Slippery Mind is wasted), but I could be persuaded otherwise on that point.

edit: I should add that in order to properly "utilize" this set-up, you likely need to defense-stack with Blur (making you basically immune to crits and damned near immune to hits, unless the enemy gains advantage), and make judicious, but regular use of Shield. Rather than a bladesinger who takes the best parts of Rogue, it's the other side of the coin: a gishy Rogue, not really much of a wizard.

[Grod_The_Giant]

I'm skeptical of Bladesinger 2/Rogue X mainly because your Int is going almost entirely to "waste". Unless you're thinking of an Arcane Trickster? I suppose I could see some point to that, though you're still stuck with low-level spells.

Bladesinger 10/Rogue 10 or something similar is a lot more plausible in my eyes. Rogues are front-loaded anyway.
Yeah, I think I might go Rogue 3 (Swashbuckler)/Bladesinger instead. Get the best of the Rogue's skills and mobility, then start ratcheting up the power. Get those nasty, sneak attack laden Booming Blades in and then run away.

[Zman]

It's more or less a drop in the bucket when you finally get it, though it at least gives you a clear reason to use your extra attack rather than just automatically going with an SCAG cantrip.

This is something that has always mystified me about the bladesinger. The class came out in the same book as the SCAG cantrips...and yet the developers don't seem to have understood that their new cantrips rendered the class' extra attack at 6th level (which I'm sure they thought was a sh-t hot ability when they put it in there) largely irrelevant because it is not clearly better (and from 11 -> 13, pretty much strictly worse) than using a cantrip with a single attack. Just a sort of weird disconnect in the development of the class.

Firstly, it is consistant with Valor Bard and Bladelock, even though the Cantrips are there the Extra attacks have times where they are the better option. I broke them down in the other thread, and often against a single enemy where you can't expect to get your rider, your damage is better. Also, any magic weapon with a static modifier or bonus damage dice heavily benefits the use of extra attack over a melee Cantrip.

[Mandragola]

Bladesinger mixed with rogue does look like a good multiclass. Bladesinging adds a lot to a rogue, and 2 levels isn't a huge cost for them. Access to all those spells, and a spellbook, is a big help to an arcane trickster anyway.

[DivisibleByZero]

No doubt there.
In 2e, elves could be dual class fighter/mage/thief.
In 5e, the equivalent build would be Eldritch Knight 7 / Bladesinger 2 / Arcane Trickster 11, gaining seven caster levels (or 9/2/9 gaining cl8).

[gkathellar]

Yeah, I think I might go Rogue 3 (Swashbuckler)/Bladesinger instead. Get the best of the Rogue's skills and mobility, then start ratcheting up the power. Get those nasty, sneak attack laden Booming Blades in and then run away.

Return of the Swashbuckler 3 dip? :P

Paladin 2 is also quite nice for a bladesinger who intends to melee, as it fixes their damage problems decisively.

But really, I think the people who have said it's best for a pure caster are right - it gives you good defenses 2/short rest, and the other abilities are pretty forgettable since you have high level spells to toss around by that point.

[MaxWilson]

Swashbuckler 3/Bladesinger X would only be fun in my eyes if your DM allows some kind of way for you to still eventually hit Bladesinger 18. Being stuck as a Swashbuckler 3/Bladesinger 17 for all of eternity would be torment. Even the potential of being dead-ended for eternity would be enough to kill the fun for me--I'd rather just be Rogue 2/Bladesinger 8 with Mobile feat than Swashbuckler 3/Bladesinger 7 and +2 Int, in that case.

Besides, a Rogue 2/Bladesinger 6 already has plenty of ways to be mobile in combat. You could, for example, attack an enemy once, then again with your bonus action as an off-hand attack, then Push him 5' away (to avoid his opportunity attack) and back off 40' feet (due to Bladesong mobility boost). As long as your Push doesn't fail that's as good as a Swashbuckler's ability. Alternately, push him prone instead of away, make your other two attacks at advantage, and just rely on your AC to keep you safe from his opportunity attack-at-disadvantage.

[Mandragola]

I basically think that swashbuckler is pointless because dual wielding, despite being the point of this thread, is just a bad plan as a wizard. If you do something that makes it very difficult to cast spells, you're not really doing your job as a caster. This most especially applies to counterspell of course, since you don't even get the opportunity to put a weapon away. So just use cunning action to get out of the way instead.

Ultimately there are easier ways to play a dual wielder, or get the same benefits as one. A dual wield bladesinger is just a lot of effort to go through to do something that a fighter can do from level 1.

[DracoKnight]

It's more or less a drop in the bucket when you finally get it, though it at least gives you a clear reason to use your extra attack rather than just automatically going with an SCAG cantrip.

This is something that has always mystified me about the bladesinger. The class came out in the same book as the SCAG cantrips...and yet the developers don't seem to have understood that their new cantrips rendered the class' extra attack at 6th level (which I'm sure they thought was a sh-t hot ability when they put it in there) largely irrelevant because it is not clearly better (and from 11 -> 13, pretty much strictly worse) than using a cantrip with a single attack. Just a sort of weird disconnect in the development of the class.


It's just a poorly designed subclass-- a mishmash of abilities that aren't really on-point for a mage-warrior. You're basically just a Wizard who gets massive AC twice/short rest.

This is why my group swaps out Extra Attack for War Magic.

[nolenja]

Correct.

And for the OP, Dual Weilding is pretty much the way to go for bladesingers; similar to PAM being the way to go for bladelocks. Get yourself a 1 level dip in fighter for the fighting style and possibly armor proficiency, and you're set. A bonus action attack with 2 mods to damage and possibly an extra die from enlarge at earlier levels is a decent plan in my eyes.

Feats you would want are Dual Wielder and War Caster. This way you can use two d8 weapons and cast V,S spells without having to juggle objects.

Somewhat in the same vein, If I have a bladesinger with warcaster, and an ally is playing a battlemaster. Does his commander's trike grant me a GFB/BB cantrips. As written his power let's me make an attack with my reaction. But warcaster must be an opportunity attack.

I have 2 DM's in 2 campaigns right now and this is one of the only things they disagree on.

[the secret fire]

Somewhat in the same vein, If I have a bladesinger with warcaster, and an ally is playing a battlemaster. Does his commander's trike grant me a GFB/BB cantrips. As written his power let's me make an attack with my reaction. But warcaster must be an opportunity attack.

I have 2 DM's in 2 campaigns right now and this is one of the only things they disagree on.

I think RAI, it should, but RAW, it pretty clearly does not. The attack action, alone, would not allow the casting of a cantrip.

[DivisibleByZero]

Somewhat in the same vein, If I have a bladesinger with warcaster, and an ally is playing a battlemaster. Does his commander's trike grant me a GFB/BB cantrips. As written his power let's me make an attack with my reaction. But warcaster must be an opportunity attack.

I have 2 DM's in 2 campaigns right now and this is one of the only things they disagree on.

Commander's Strike allows an attack.
GFB and BB are spells.
WC allows a spell in place of an OA, but CS doesn't give you an OA, it gives you a reaction attack.
All OAs are reaction attacks, but not all reaction attacks are OAs.
By both RAW and RAI the answer is no.
One of your DMs is being lenient.

[Arial Black]

According to 5E, 'attack' is simply something where you make an 'attack roll'.

Therefore 'attack' could be a 'weapon attack' OR a 'spell attack'.

If the 'attack' in question is required to be a 'weapon attack', then since both booming blade and green-flame blade are 'weapon attacks' generated by taking the Cast A Spell action, then they are valid choices for that 'weapon attack'.

Commander's Strike does not define what kind of action (Attack, Cast A Spell) can be taken; it only specifies 'weapon attack'. Both spells require a "melee attack with a weapon", so both spells ARE eligible for use with Commander's Strike.

[RickAllison]

According to 5E, 'attack' is simply something where you make an 'attack roll'.

Therefore 'attack' could be a 'weapon attack' OR a 'spell attack'.

If the 'attack' in question is required to be a 'weapon attack', then since both booming blade and green-flame blade are 'weapon attacks' generated by taking the Cast A Spell action, then they are valid choices for that 'weapon attack'.

Commander's Strike does not define what kind of action (Attack, Cast A Spell) can be taken; it only specifies 'weapon attack'. Both spells require a "melee attack with a weapon", so both spells ARE eligible for use with Commander's Strike.

Nope.

Commander's Strike doesn't define what action you take because you aren't taking a standard action! These sorts of actions are ad-hoc capabilities, unique and defined by the ability. You aren't taking the Attack action, you aren't taking the Cast a Spell action, you are making an attack per the rules in the ability. You can't grapple, shove, Mark, or disarm. You make an attack per the rules in the ability text. That's all.

[Arial Black]

Nope.

Commander's Strike doesn't define what action you take because you aren't taking a standard action! These sorts of actions are ad-hoc capabilities, unique and defined by the ability. You aren't taking the Attack action, you aren't taking the Cast a Spell action, you are making an attack per the rules in the ability. You can't grapple, shove, Mark, or disarm. You make an attack per the rules in the ability text. That's all.

Nope.

I never claimed to be taking any kind of Action In Combat at all, whether the Attack action or the Cast A Spell action.

Commander's Strike allows you to make a weapon attack. BB and G-FB are weapon attacks.

Outside combat and initiative, you cannot take any Action In Combat....nor do you need to. Outside combat, if you want to cast a spell then you do not and cannot take the Cast A Spell action, you just...cast it.

All of the things you can do in combat have an Action In Combat that lets you do that thing, but that thing does not require an Action In Combat to do unless you are in combat/initiative.

Furthermore, the type of game action (in terms of action economy) that it takes is not set in stone. For example, Disengage might well take your actual Action to do, but you may very well be able to Disengage by using your Bonus Action (using Cunning Action as a rogue) or part of another action (like the Mobile feat letting you get the benefit of a Disengage type effect if you attack the target you want to deny an OA).

Commander's Strike is another way to attack with a weapon. You use your Reaction. The actual thing you do (Attack, Cast A Spell) is not limited beyond having to be an attack with a weapon, and the type of Action it would normally use (Action, Bonus Action, Reaction, free action) is replaced by your Reaction.

Your ally uses Commander's Strike and chooses you. As long as what you do is an attack with a weapon, you can use any ability you have at your disposal, and instead of the type of game action it would normally use, it uses your reaction.

Player: I'll use booming blade.
DM: Is that a weapon attack?
Player: Yes.
DM: Then you haven't broken any rule. Roll your attack.

[RickAllison]

Nope.

I never claimed to be taking any kind of Action In Combat at all, whether the Attack action or the Cast A Spell action.

Commander's Strike allows you to make a weapon attack. BB and G-FB are weapon attacks.

Outside combat and initiative, you cannot take any Action In Combat....nor do you need to. Outside combat, if you want to cast a spell then you do not and cannot take the Cast A Spell action, you just...cast it.

All of the things you can do in combat have an Action In Combat that lets you do that thing, but that thing does not require an Action In Combat to do unless you are in combat/initiative.

Furthermore, the type of game action (in terms of action economy) that it takes is not set in stone. For example, Disengage might well take your actual Action to do, but you may very well be able to Disengage by using your Bonus Action (using Cunning Action as a rogue) or part of another action (like the Mobile feat letting you get the benefit of a Disengage type effect if you attack the target you want to deny an OA).

Commander's Strike is another way to attack with a weapon. You use your Reaction. The actual thing you do (Attack, Cast A Spell) is not limited beyond having to be an attack with a weapon, and the type of Action it would normally use (Action, Bonus Action, Reaction, free action) is replaced by your Reaction.

Your ally uses Commander's Strike and chooses you. As long as what you do is an attack with a weapon, you can use any ability you have at your disposal, and instead of the type of game action it would normally use, it uses your reaction.

Player: I'll use booming blade.
DM: Is that a weapon attack?
Player: Yes.
DM: Then you haven't broken any rule. Roll your attack.

No.

Booming Blade:


As part of the action used to cast this spell, you must
make a melee attack with a weapon against one creature
within the spell's range, otherwise the spell fails.

So BB and GFB are banned long before we consider weapon attacks and the like. Making a weapon attack is part of casting the spell, not the spell itself. Using either with Commander's Strike is not just questionable, it is utterly opposed to the RAW. So yes, the player in question did break the rules.

You might come up with some other examples that I would have to look closer at, but there is no way by the rules that either BB or GFB could be used with Commander's Strike. The spell isn't making a melee weapon attack, it just requires that as part of the casting. As DM, you can houserule it to be allowed, but that does not make it usable by RAW in any way.

[Arial Black]

No.

So BB and GFB are banned long before we consider weapon attacks and the like. Making a weapon attack is part of casting the spell, not the spell itself. Using either with Commander's Strike is not just questionable, it is utterly opposed to the RAW. So yes, the player in question did break the rules.

No.

No part of Commander's Strike tells you what abilities, spells, whatever that you can or cannot use, apart from requiring a weapon attack.

No part of Commander's Strike suggests that you deliver a weapon attack unless that attack was part of spellcasting.

I could deliver my weapon attack as part of casting booming blade or as part of a Whirlwind Strike, I could use the weapon attack to trigger my Divine Smite or Sneak Attack (whether or not the weapon attack was a result of booming blade or Whirlwind Strike).

There are no limits apart from being an attack with a weapon and that you use your Reaction.

[RickAllison]

No.

No part of Commander's Strike tells you what abilities, spells, whatever that you can or cannot use, apart from requiring a weapon attack.

No part of Commander's Strike suggests that you deliver a weapon attack unless that attack was part of spellcasting.

I could deliver my weapon attack as part of casting booming blade or as part of a Whirlwind Strike, I could use the weapon attack to trigger my Divine Smite or Sneak Attack (whether or not the weapon attack was a result of booming blade or Whirlwind Strike).

There are no limits apart from being an attack with a weapon and that you use your Reaction.

I... I really don't know where to go from here. You have read so much more into this ability than exists.

When something lets you make a weapon attack, it is directly attacking and not fiddling with any abilities. You cannot Whirlwind, you cannot BB, you can only make a weapon attack. You do not use an ability that includes a weapon attack, you make a weapon attack! You attack with a weapon, nothing more. Abilities like Divine Smite and Sneak Attack work because they trigger off a weapon attack without caring where it came from.

Let me re-iterate: Commander's Strike lets an ally make a weapon attack, not an ability that includes the same. Attack with your bow, attack with your sword, attack with your fists (since attacks with them are considered weapon attacks despite fists not being a weapon). Using any ability with it is a violation of the rules.

Weapon attack, not ability that includes an attack. Just to restate it one more time.

[the secret fire]

What Rick is saying, which I am fairly certain is a correct reading of the rules, is also related to the reason that cantrip attacks do not work with any bonus action attacks, such as those from two-weapon fighting or PAM. The game is quite specific in delineating what can be accomplished with a given action. Casting an attack cantrip is a standard action which happens to involve a weapon attack. It is not the attack action, and it is also not a "one weapon attack", as described in the text of Commander's Strike.

Again...using an attack cantrip is a standard action. You actually need the same action economy to cast an attack cantrip as you need to cast any other type of spell because you are casting a spell. If the developers had meant to allow spellcasting through Commander's Strike, which they clearly didn't because that would be stupidly OP in certain situations, they would have said that it grants the target "one standard action". They didn't say that. They said "one weapon attack", period.

Honestly, I don't have a problem with doing it AB's way at my table (though not including other spells) because I think Commander's Strike is of questionable value, anyway, and I like to encourage players to use less cookie-cutter builds by being generous in how I rule the use of options considered sub-optimal by the majority.

[gkathellar]

@ArialBlack: RickAllison is 100% right about this. When ability tells you to make an attack, it wants you to make an attack. It's not asking you to use the attack action, or to use some other ability that involves an attack. It just wants you make an attack.


I basically think that swashbuckler is pointless because dual wielding, despite being the point of this thread, is just a bad plan as a wizard.

It's also a bad plan as anyone else, to be fair.

[Arial Black]

What Rick is saying, which I am fairly certain is a correct reading of the rules, is also related to the reason that cantrip attacks do not work with any bonus action attacks, such as those from two-weapon fighting or PAM. The game is quite specific in delineating what can be accomplished with a given action. Casting an attack cantrip is a standard action which happens to involve a weapon attack. It is not the attack action, and it is also not a "one weapon attack", as described in the text of Commander's Strike.

Again...using an attack cantrip is a standard action. You actually need the same action economy to cast an attack cantrip as you need to cast any other type of spell because you are casting a spell. If the developers had meant to allow spellcasting through Commander's Strike, which they clearly didn't because that would be stupidly OP in certain situations, they would have said that it grants the target "one standard action". They didn't say that. They said "one weapon attack", period.

Your laying out of the rules should lead you to the opposite conclusion.

The reason these cantrips don't work with 'bonus action attacks' is not because these bonus actions deny the use of cantrips but because these particular bonus actions do not exist until they are generated, and they happen to be generated by taking the Attack Action as your action, and since you took the Attack Action then you obviously did not take the Cast A Spell Action.

But none of that even comes up with Commander's Strike.

Types of 'actions' (i.e.'stuff you do'), like 'attack with a weapon', 'cast a spell', 'disengage' etc are not inextricably tied to certain action types (Action, Bonus Action, Free Action, Not An Action). They all have a default (like Disengage being a full action) but you may very well have a way to do that thing (like attack, cast a spell, disengage) using a different action type (like Cunning Action allowing you to Disengage, Dash or Hide as a bonus action rather than a full action).

Commander's Strike is that way in this case. CS does not, as pointed out, give you a specific action (like the Disengage action or the Attack action or the Cast A Spell action). If CS gave you the Attack action then you would not be able to use one of these cantrips because they need the Cast A Spell action (no matter if you can use the Cast A Spell action as a bonus action or a reaction or whatever).

The very reason that you can use these cantrips is that CS does not define the Action you must take at all! Therefore you can take any kind of action (Attack, Cast A Spell, Hide, Disengage, whatever) as long as you abide by the restriction that CS does have, which is that it must be a 'weapon attack'. Each of these cantrips is a weapon attack.

[RickAllison]

ArialBlack, I have officially decided to stop correcting you. You don't understand the basic rules of the system. Trying to explain this is like trying to explain advanced Dominion combos with someone who doesn't grasp how the individual cards work alone.

If you don't understand that calling for a weapon attack is different than calling for an ability that includes a weapon attack, then you need to be taught the system again. This is not an insult, this is a frank analysis of your arguments and how they do not fit with the rules of the system at all.

[Arial Black]

ArialBlack, I have officially decided to stop correcting you. You don't understand the basic rules of the system. Trying to explain this is like trying to explain advanced Dominion combos with someone who doesn't grasp how the individual cards work alone.

If you don't understand that calling for a weapon attack is different than calling for an ability that includes a weapon attack, then you need to be taught the system again. This is not an insult, this is a frank analysis of your arguments and how they do not fit with the rules of the system at all.

RickAllison, I have officially decided to stop correcting you. You don't understand the basic rules of the system. Trying to explain this is like trying to explain advanced Dominion combos with someone who doesn't grasp how the individual cards work alone.

If you don't understand that calling for a weapon attack includes calling for an ability that includes a weapon attack, then you need to be taught the system again. This is not an insult, this is a frank analysis of your arguments and how they do not fit with the rules of the system at all.

[JackPhoenix]

No.

No part of Commander's Strike tells you what abilities, spells, whatever that you can or cannot use, apart from requiring a weapon attack.

No part of Commander's Strike suggests that you deliver a weapon attack unless that attack was part of spellcasting.

I could deliver my weapon attack as part of casting booming blade or as part of a Whirlwind Strike, I could use the weapon attack to trigger my Divine Smite or Sneak Attack (whether or not the weapon attack was a result of booming blade or Whirlwind Strike).

There are no limits apart from being an attack with a weapon and that you use your Reaction.

Yes, you make a melee weapon attack with Commander's Strike. But you don't do that part that makes BB/GFB more just smacking the enemy with your weapon... Commander's Strike doesn't allow you to cast a spell.

[Arial Black]

Yes, you make a melee weapon attack with Commander's Strike. But you don't do that part that makes BB/GFB more just smacking the enemy with your weapon... Commander's Strike doesn't allow you to cast a spell.

Commander's Strike is silent on the issue of casting a spell, it just requires a weapon attack. These cantrips are both weapon attacks AND spells.

[Arial Black]

Yes, you make a melee weapon attack with Commander's Strike. But you don't do that part that makes BB/GFB more just smacking the enemy with your weapon... Commander's Strike doesn't allow you to cast a spell.

Commander's Strike is silent on the issue of casting a spell, it just requires a weapon attack. These cantrips are both weapon attacks AND spells.

CS doesn't limit what you can do, it just requires a weapon attack.

If this were not the case then CS would disallow Sneak Attacks and Divine Smites.

[MeeposFire]

Commander's Strike is silent on the issue of casting a spell, it just requires a weapon attack. These cantrips are both weapon attacks AND spells.

CS doesn't limit what you can do, it just requires a weapon attack.

If this were not the case then CS would disallow Sneak Attacks and Divine Smites.

That is fundamentally incorrect. Sneak attack and smites are not actually attacks. They are things that happen on a hit from an attack. They are things you apply to any attack. That is very different from say booming blade which is a spell that makes an attack as part of it or even just a standard attack.

What you are trying to do is saying that CS allows you to replace a standard attack with anything that includes an attack roll and a weapon. That is very different than smites and SA which are not special attacks and are applied on a hit.

[DarkSoul]

Commander's Strike is silent on the issue of casting a spell, it just requires a weapon attack. These cantrips are both weapon attacks AND spells.

CS doesn't limit what you can do, it just requires a weapon attack.

If this were not the case then CS would disallow Sneak Attacks and Divine Smites.Commander's Strike absolutely does limit what you can do. It says "...creature can immediately use its reaction to make one weapon attack..." That's it. If it doesn't say you CAN do something, then you can't. Commander's Strike allows an ally to make a weapon attack. Booming Blade is a spell. Part of the resolution of that spell is making a weapon attack. Commander's Strike does not allow you to cast a spell, therefore you can't use Booming Blade or any other weapon attack cantrip. I don't see why this is so hard to grasp.

Regarding smite and sneak attack, those are both effects that trigger as a result of a weapon attack, so there's no reason for Commander's Strike to prevent them from working. Booming Blade is the reverse. The weapon attack triggers as a result of casting the spell. CS doesn't allow you to cast a spell, so you don't get to use Booming Blade. If Booming Blade said "When you hit with a weapon attack, you can cast this spell to..." then you'd be correct in your interpretation, but it doesn't so you aren't.

I'm playing a bladesinger right now and even I find your interpretation absurd, because there's nothing to support it in the rules. It would be undeniably powerful, and a great benefit for the Booming Blade caster, but it's simply not allowed.

[Arial Black]

Regarding smite and sneak attack, those are both effects that trigger as a result of a weapon attack, so there's no reason for Commander's Strike to prevent them from working. Booming Blade is the reverse. The weapon attack triggers as a result of casting the spell. CS doesn't allow you to cast a spell, so you don't get to use Booming Blade.

While I understand the case you are putting forward, I don't agree with your conclusion.

With both BB and G-FB, in terms of game mechanics, the first thing you do is roll a weapon attack. If that attack misses, nothing else happens. If it hits, then the extra stuff happens.

Which is exactly what happens with Sneak Attack and Divine Smite! First, roll a weapon attack. If it misses, nothing else happens. If it hits, then extra stuff happens.

CS does not, we agree, give you a Cast A Spell action. But neither does it give you an Attack action. CS is not tied to either of these Actions. All it requires is that you roll an attack with a weapon; it doesn't care what Action (Attack, Cast A Spell) that it would usually take, nor does it care what type of action (in the action economy) it would usually take because CS uses your reaction.

[RickAllison]

While I understand the case you are putting forward, I don't agree with your conclusion.

With both BB and G-FB, in terms of game mechanics, the first thing you do is roll a weapon attack. If that attack misses, nothing else happens. If it hits, then the extra stuff happens.

Which is exactly what happens with Sneak Attack and Divine Smite! First, roll a weapon attack. If it misses, nothing else happens. If it hits, then extra stuff happens.

CS does not, we agree, give you a Cast A Spell action. But neither does it give you an Attack action. CS is not tied to either of these Actions. All it requires is that you roll an attack with a weapon; it doesn't care what Action (Attack, Cast A Spell) that it would usually take, nor does it care what type of action (in the action economy) it would usually take because CS uses your reaction.

To make an attack with GFB/BB, you need to have cast the spell. If you don't cast the spell, you don't have the weapon attack with the rider. The process would go like this:

"Make a weapon attack."
"I swing with Booming Blade. [rolls a 19]. Hit."
"You can't cast the magic to infuse the blade because that is not permitted by Commander's Strike, so the attack just hits with the blade. Roll for your weapon's damage."

[Arial Black]

To make an attack with GFB/BB, you need to have cast the spell. If you don't cast the spell, you don't have the weapon attack with the rider.

It's the other way round: if you haven't made the weapon attack, and hit with that attack, then you cannot cast the spell. Hitting with the attack is a pre-req for the spell, just like hitting with an attack is a pre-req for Sneak Attack/Divine Smite. Therefore, the weapon attack comes before the spell.

This is entirely consistent with the relationship between casting a spell (the VSM components) and the effect of the spell in D&D. You must perform and successfully complete the components before the spell effect even begins (any spell, not just these two). If the components are not completed successfully for any reason the the spell itself never comes into existence.

Since the description of the spells states that the weapon attack is part of the casting process, this weapon attack must occur before the spell effect begins. In a way, the (successful) weapon attack causes the spell effect, just like it would cause the Sneak Attack/Divine Smite effects. That weapon attack is enabled by Commander's Strike, that weapon attack is just like the ones that can cause Sneak Attack/Divine Smite, and Commander's Strike doesn't care to differentiate between the weapon attack which enables SA/DS and the weapon attack which enables BB/G-FB.

[RickAllison]

It's the other way round: if you haven't made the weapon attack, and hit with that attack, then you cannot cast the spell. Hitting with the attack is a pre-req for the spell, just like hitting with an attack is a pre-req for Sneak Attack/Divine Smite. Therefore, the weapon attack comes before the spell.

This is entirely consistent with the relationship between casting a spell (the VSM components) and the effect of the spell in D&D. You must perform and successfully complete the components before the spell effect even begins (any spell, not just these two). If the components are not completed successfully for any reason the the spell itself never comes into existence.

Since the description of the spells states that the weapon attack is part of the casting process, this weapon attack must occur before the spell effect begins. In a way, the (successful) weapon attack causes the spell effect, just like it would cause the Sneak Attack/Divine Smite effects. That weapon attack is enabled by Commander's Strike, that weapon attack is just like the ones that can cause Sneak Attack/Divine Smite, and Commander's Strike doesn't care to differentiate between the weapon attack which enables SA/DS and the weapon attack which enables BB/G-FB.

But the other components are not. You also need to have permission to do the verbal components. Even without the inhibition of violating the rules, you still don't have the requirements met for the spell.

[DarkSoul]

While I understand the case you are putting forward, I don't agree with your conclusion.

With both BB and G-FB, in terms of game mechanics, the first thing you do is roll a weapon attack. If that attack misses, nothing else happens. If it hits, then the extra stuff happens.

Which is exactly what happens with Sneak Attack and Divine Smite! First, roll a weapon attack. If it misses, nothing else happens. If it hits, then extra stuff happens.

CS does not, we agree, give you a Cast A Spell action. But neither does it give you an Attack action. CS is not tied to either of these Actions. All it requires is that you roll an attack with a weapon; it doesn't care what Action (Attack, Cast A Spell) that it would usually take, nor does it care what type of action (in the action economy) it would usually take because CS uses your reaction.
No, when using Booming Blade and Greenflame Blade, the first thing you do is cast a spell. Both spells explicitly state that "As part of the action used to cast this spell, you must make a melee attack with a weapon against one creature within the spell's range, otherwise the spell fails." (emphasis mine). In fact, it's the very first sentence of each spell's description. You spend an action to cast the spells, and as part of the casting, you make your weapon attack. You don't declare that you're attacking and if it hits, your spell is somehow cast and takes effect. You have to cast the spell first, which you agree is explicitly not allowed by Commander's Strike.


It's the other way round: if you haven't made the weapon attack, and hit with that attack, then you cannot cast the spell. Hitting with the attack is a pre-req for the spell, just like hitting with an attack is a pre-req for Sneak Attack/Divine Smite. Therefore, the weapon attack comes before the spell.

This is entirely consistent with the relationship between casting a spell (the VSM components) and the effect of the spell in D&D. You must perform and successfully complete the components before the spell effect even begins (any spell, not just these two). If the components are not completed successfully for any reason the the spell itself never comes into existence.

Since the description of the spells states that the weapon attack is part of the casting process, this weapon attack must occur before the spell effect begins. In a way, the (successful) weapon attack causes the spell effect, just like it would cause the Sneak Attack/Divine Smite effects. That weapon attack is enabled by Commander's Strike, that weapon attack is just like the ones that can cause Sneak Attack/Divine Smite, and Commander's Strike doesn't care to differentiate between the weapon attack which enables SA/DS and the weapon attack which enables BB/G-FB.No, no, so very much no. Hitting with the attack is not a pre-requisite for casting these spells, it's essentially part of the somatic component because you make the attack as you cast the spell, and making the attack is an integral part of the spell's casting. If you don't make the attack, the spell fails. You don't get to say you're attacking and if it hits, casting Booming Blade. You cast the spell, make the attack, and if it misses, try again next round if you'd like. That's why it's a cantrip.

The weapon attack cannot occur before casting the spell. If it does, you used your action to attack, not to cast. Casting the spell imbues your weapon with whatever magic you chose to use for one round, and then it fades. This happens at the same time (during the same action) that you make your attack. One doesn't take place before the other.

You're correct that the attack is part of the casting process, thus you agree that making the attack with these cantrips is part of the spell's casting, correct? Before you say no, keep in mind that you just said yes. Because the attack for these spells is part of the casting process, it follows that if you can't cast the spell before (or "as", if you prefer) you make the attack, then there's no way the spell can take effect, correct? Thus Commander's Strike doesn't allow the attack cantrips to be cast, but smite and sneak attack still work because their effects are dependent on hitting with an attack, not casting a spell.

The short version: BB/GFB are spells that give you an attack. Smite/SA are effects that trigger upon hitting with an attack. CS lets you attack, not cast spells. Smite/SA work, cantrips don't, your interpretation is incorrect and has been proven so, partially by your own arguments.

Furthermore, BB/GFB both take 1 action to cast, according to their spell entries in SCAG. CS lets you make a weapon attack as a reaction. Reactions are not actions, therefore STILL no cantrips during a CS attack. Attack with your weapon.

[Arial Black]

No, when using Booming Blade and Greenflame Blade, the first thing you do is cast a spell. Both spells explicitly state that "As part of the action used to cast this spell, you must make a melee attack with a weapon against one creature within the spell's range, otherwise the spell fails." (emphasis mine). In fact, it's the very first sentence of each spell's description. You spend an action to cast the spells, and as part of the casting, you make your weapon attack. You don't declare that you're attacking and if it hits, your spell is somehow cast and takes effect. You have to cast the spell first, which you agree is explicitly not allowed by Commander's Strike.

Casting a spell is certainly not "explicitly not allowed" by Commander's Strike!


No, no, so very much no. Hitting with the attack is not a pre-requisite for casting these spells, it's essentially part of the somatic component because you make the attack as you cast the spell, and making the attack is an integral part of the spell's casting. If you don't make the attack, the spell fails. You don't get to say you're attacking and if it hits, casting Booming Blade. You cast the spell, make the attack, and if it misses, try again next round if you'd like. That's why it's a cantrip.

It should be noted that 'attacking' (as part of the casting process) is not enough; that attack must hit, and if it misses then the spell fails.


The weapon attack cannot occur before casting the spell. If it does, you used your action to attack, not to cast. Casting the spell imbues your weapon with whatever magic you chose to use for one round, and then it fades. This happens at the same time (during the same action) that you make your attack. One doesn't take place before the other.

The casting process (the VSM components: saying the magic words, making the mystic gestures, having the correct materials in hand) is a separate thing to the spell effect (the ball of fire, the missiles streaking toward the target, etc). The casting process definitely precedes the effect. The cart cannot come before the horse here; cause must come before effect.


You're correct that the attack is part of the casting process, thus you agree that making the attack with these cantrips is part of the spell's casting, correct? Before you say no, keep in mind that you just said yes. Because the attack for these spells is part of the casting process, it follows that if you can't cast the spell before (or "as", if you prefer) you make the attack, then there's no way the spell can take effect, correct? Thus Commander's Strike doesn't allow the attack cantrips to be cast, but smite and sneak attack still work because their effects are dependent on hitting with an attack, not casting a spell.

The short version: BB/GFB are spells that give you an attack. Smite/SA are effects that trigger upon hitting with an attack. CS lets you attack, not cast spells. Smite/SA work, cantrips don't, your interpretation is incorrect and has been proven so, partially by your own arguments.

CS lets you attack; it does not prohibit the casting of spells.


Furthermore, BB/GFB both take 1 action to cast, according to their spell entries in SCAG. CS lets you make a weapon attack as a reaction. Reactions are not actions, therefore STILL no cantrips during a CS attack. Attack with your weapon.

This is provably incorrect.

The casting time of spells, listed in their stat block, is a default. Other abilities may change that.

For example, both BB and G-FB have a casting time of 'one action'. However, if you have the Warcaster feat then instead of making an Attack of Opportunity you may cast either cantrip at the provoking creature...using your reaction, not your action.

Commander's Strike lets you do what you do as a reaction, no matter the usual action cost associated with that thing.

Furthermore, in order to make a weapon attack in combat it usually requires the Attack action. But not always. CS itself demonstrates that.

In order to cast a spell it usually requires the Cast A Spell action. But not always. Warcaster demonstrates that.

Commander's Strike does not give you an Attack action; it just allows you to make a weapon attack using your reaction and the Commander's Strike action itself.

Does CS allow you to talk? Yes, creatures can speak short phrases whether it's their turn or not.

Does CS allow you to hold a weapon? Yes, obviously; it allows a weapon attack after all.

Does CS allow you to make a weapon attack? Yes, it says it does.

In order to cast BB or G-FB, what do you need to do?

Speak a short phrase (the Verbal component). We know that the phrase is brief enough to be said as part of a reaction.

Hold a weapon (the Material component).

Although neither BB nor G-FB has a somatic component, they each require a successful weapon attack.

So, Commander's Strike allows everything needed to cast these cantrips. At no time does CS forbid anything needed to do so. Ergo, CS allows the casting of these cantrips.

Q, E, and indeed, D.

[Klorox]

I'm just curious as to who would dual wield at the cost of not being able to cast a reaction spell, like shield.

Warcaster, if taken at all, should be taken at 19th level.

Let's say you start with a 16 in INT and DEX. Assuming you're using a finesse weapon (and you should be), your first 4 ASI should be boosting DEX and INT to 20.

So yes, a bladesinger could dual wield, but they shouldn't.

[Blit_Wizbok]

The bladesinger is a class I'm well versed in. Dual-wielding is great fun, and looks awesome to boot. However, I often run into issues with action economy, well, more like bonus action economy. The way I typically play is by using Flaming Sphere to force targets to move, triggering Booming Blade. Moving the Sphere is a bonus action, so you wouldn't be able to get your offhand attack.

That's just my playstyle, but many other spells consume your bonus action: Misty Step, Melf's Minute Meteors, and Animate Objects, just to name a few; not to mention activating Bladesong.

Now, I'm a firm believer in doing what looks most badass, and twirling ballerina of death, spinning and hacking through enemies, is pretty badass. I just want to make you aware that there will be times when you won't have the option to use your offhand attack, because your bonus action was spent on other, more beneficial, spells.

(Also the fighting style isn't available to the Wizard, so unless you multiclass, you won't have your DEX/STR mod to add to the damage of your offhand attack)