D&D 5E (2024) Thoughts on New Bladesinger?

[Tessarael]

That depends on if the DM allows you to buy magic items and if so, how they are determined to be for sale.

Agreed, but it is intended to be a common magic item. Highly DM dependent as you commented, as I doubt most published modules have Ruby of the Warmage as loot. One of the issues with D&D having such a variety of magic items is that you're also not that likely to have it rolled as random treasure either.

On a related note, Hat of Wizardry is another common D&D 2024 magic item that can be used as a spell casting focus by a Wizard that attunes it.

 

[Tessarael]

Booming blade lasts for the entire round. It would still be on when you Action Surge.

The only thing that lasts for the round for Booming Blade is the additional thunder damage if the target moves before your next turn. The extra damage on Booming Blade to an attack applies only to the melee attack made as part of casting the spell, "You brandish the weapon used in the spell's casting and make a melee attack with it against one creature within 5 feet of you ... At 5th level, the melee attack deals an extra 1d8 thunder damage to the target on a hit, and the damage the target takes for moving increases to 2d8."
It does not provide any additional benefits with Action Surge, as D&D 2024 Action Surge doesn't permit you to take the Magic Action again to cast Booming Blade again. D&D 2014 Action Surge would permit you to cast Booming Blade twice in a round for the additional damage again.

Now if you have an opportunity attack after your turn, e.g., from an opponent leaving your reach without Disengage, then you could cast Booming Blade again, if you have the War Caster feat to permit you to do so.

 

[ECMO3]

It does not provide any additional benefits with Action Surge, as D&D 2024 Action Surge doesn't permit you to take the Magic Action again to cast Booming Blade again. D&D 2014 Action Surge would permit you to cast Booming Blade twice in a round for the additional damage again.

A 6th level Bladesinger, 6th level Valor Bard or a 7th level Eldritch Knight can cast Booming Blade using the Attack action. So it works with Action Surge if you have one of those three subclasses (assuming you got it from somewhere else on the Bard).

 

[Tessarael]

A 6th level Bladesinger, 6th level Valor Bard or a 7th level Eldritch Knight can cast Booming Blade using the Attack action. So it works with action Surge if you have one of those three subclasses (assuming you got it from somewhere else on the Bard).

That doesn't override the D&D 2024 wording on Action Surge not being usable for a Magic Action, though I see it being argued otherwise.

 

[Zardnaar]

A 6th level Bladesinger, 6th level Valor Bard or a 7th level Eldritch Knight can cast Booming Blade using the Attack action. So it works with Action Surge if you have one of those three subclasses (assuming you got it from somewhere else on the Bard).

Yup its how you can cast 6 spells a round.

 

[ECMO3]

That doesn't override the D&D 2024 wording on Action Surge not being usable for a Magic Action, though I see it being argued otherwise.

You don't use the Magic Action at all. With those subclasses, you use the attack action and their subclass specific version of Extra Attack.

Action Surge does not prevent you from casting spells, it just prevents you from using the Magic Action.