So as many of you may have heard, Booming Blade will be getting errata'd in Tasha's to provide a range of "Self" instead of "5 feet." The consequences of this include:

• Will no longer be eligible for Distant Spell from Sorcerer or Spell Sniper feat, which were necessary to enable it for Reach weapon attacks (but possibly won't be going forward, depending on how the spell description reads).
• Will no longer be eligible for Twinned Spell from Sorcerer, which had allowed two attacks to be made with one action. 
• Will maybe no longer be eligible for Warcaster feat, depending on how you understand the word "target" in 5E (general consensus is that a spell with range of self must have a target of self, per Chapter 10)
• But now will be eligible for extending to your Find Steed mount, meaning a mounted Paladin makes two attacks (one for themself, one for their steed) when casting. 
• But now will be eligible for extending to your Beast Master Animal Companion via Share Spells, meaning a Ranger within 30 feet makes two attacks when casting.

It's odd to me that Booming Blade is getting singled out with the apparent attempt to nerf it out of the Reach-using Eldritch Knight's toolkit, and taking it off the menu for Warcaster opportunity attacks (which really seem like the main context that the spell was originally designed for), but while also adding it to other toolkits that it wasn't part of before. Even odder that (it sounds like) this is only happening to BB, and not also to Green-Flame Blade? 

What are your thoughts? Any other interactions that I'm overlooking? Does this strike you as a good, or even justifiable, errata? 

If it has a range of Self instead of 5 ft., wouldn’t that mean it is always eligible for use with reach weapons without needing any shenanigans to pull it off?

Depending on how/whether they reword the spell description in addition to its header, I'm not sure it will be able to target anyone:

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...

I suppose it will remain to be seen whether that changes to "within 5 feet" or "within the weapon's range reach" or what.

My bet is “wishing range of the weapon” (or similar) will be the wording. And I bet GFB will get the same treatment, but the range of the spurt will still be 5 ft. from the attacked creature.

Quote from IamSposta >>

If it has a range of Self instead of 5 ft., wouldn’t that mean it is always eligible for use with reach weapons without needing any shenanigans to pull it off?

 Seems reasonable to me. GFB was already off the Warcaster list so maybe this just takes BB off that list and ensures that taking Spell Sniper isn't necessary with the reach weapons. Now it's making the BB closer to the Smite spells like Wrathful Smite. Interesting. 

The fact that it will be ineligible for Warcaster I think is the larger issue here. This is not just a simple fix to remove the Spell Sniper feat requirement but otherwise leave the spell as-is, that would have been accomplished by changing the range to "Melee Reach"

Quote from Chicken_Champ >>

The fact that it will be ineligible for Warcaster I think is the larger issue here. This is not just a simple fix to remove the Spell Sniper feat requirement but otherwise leave the spell as-is, that would have been accomplished by changing the range to "Melee Reach"

 If so, I wonder what the trigger was for it. I know there have been some heavy debates about whether the extra damage triggers automatically on OAs and I've heard some complaints about power level variance between Rangers and Paladins versus EKs as far as cantrips go with the SCAG trips as the obvious combat targets for EKs (for use on OAs). I'm not sure that any of that matters, though. It could be interesting if they developed additional "SCAGtrips" and decided to tweak them before adding them all in. 

I would love some more new Cantrips.

Quote from IamSposta >>

I would love some more new Cantrips.

 I want more spells in general. 

As to the original topic, I like the changes.    

Yeah, I would heartily support an expanded spell list of both cantrips and leveled spells that work in similar ways without being concentration "Smite"-type spells. The melee wizard/sorcerer/hexblade is a tantalizing concept, but there's really not much for it to do or build for apart from boosting its AC up and then running around casting a SCAGtrip once per turn, since the small selection of Smite-type spells all compete with the same defensive/mobility buffs that enable you to be there in combat in the first place. 

Quote from Chicken_Champ >>

Yeah, I would heartily support an expanded spell list of both cantrips and leveled spells that work in similar ways without being concentration "Smite"-type spells. The melee wizard/sorcerer/hexblade is a tantalizing concept, but there's really not much for it to do or build for apart from boosting its AC up and then running around casting a SCAGtrip once per turn, since the small selection of Smite-type spells all compete with the same defensive/mobility buffs that enable you to be there in combat in the first place. 

 Yeah, a Smite spell isn't likely to last more than one round unless you miss so it is possible to use one on a first round strike. The problem is that you would have to also use your action to then attack and some kind of reaction for defense (Shield or Absorb Elements come to mind). It's not a bad plan, but being able to get a longer term concentration buff is better for your slot economy and that would prevent future smites from being useful without having someone else using their concentration on your defensive/ mobility buff (which you would usually want to have happen in addition to your self buff).

It seems like some of the Smite spells do have lasting effects that extend their hold on your concentration as well. It'll be interesting to see what they've got in mind. 

Wow, it seems like WotC is crapping on the SCAG even more, now. I personally liked the combinations that were made possible with this spell (Warcaster, Twinned Spell, Spell Sniper), and am sad to see them go. Fingers are crossed that it says "within the weapon's reach," and not "within 5 feet of you," as that would suck. 

So Booming Blade/Green Flame Blade to me, were always overpowered Cantrips.  Booming Blade more so.

A cantrip at max does 4d12(toll the dead if injured) damage at level 20.  I understand some cantrips are d6/d8/d10, but lets talk about this against a 4d12 scale. Cantrips also go off your spellcasting modifier.  Booming Blade/Green Flame Blade specifically did not since we’re making Melee Weapon attacks.  Most Spell Casters aren’t rocking Wand of the War Mages +2 or +3, but most Melee Fighters at high levels are rocking +2 or +3 weapons.

So assuming max powered cantrips, Booming Blade is now doing 1d12+Modifier+Magic Weapon Bonus, + 3d8 + 4d8 if it moves willingly.  Thunder is also a damage type that is not commonly resisted either.  This damage can of course be combined with Great Weapon Master to get another +10 on the hit, which is fine.  But with War Caster, now as a reaction you are able to do 1d12+8+3d8?  No resource being spent?  Again, more if it keeps moving?

I don’t think the intent was to ever allow this, and I’m personally happy to see the full errata being put into place.  I think the changes will allow it to be used with reach weapons, which is fine, but not to be twinned which was always broken as hell.  

ok so first off, it never worked for distant spell because distant spell only worked on the spells range (witch for some reason is 5) not your weapon attack range, I guess too many DMs/players were getting this wrong
booming blade never worked with twin because you need to make a melee weapon attack as part of the spell meaning the spell doesn't actually target a creature, so once more DMs/players getting this wrong
this doesn't work for casting though your find steed because the steed does not have a weapon, the material component for booming blade is a weapon that you need to make the attack with.
same deal as the steed, if it doesn't have a weapon it can't use booming blade because you need to make a attack with said weapon.

so NOTHING about this spell has changed

No, proxy, no. That's just all wrong. I'm not even going to argue on those points, I will just point out how wrong that is. 

If nothing changes, why would they bother changing it?

Quote from Third_Sundering >>

No, proxy, no. That's just all wrong. I'm not even going to argue on those points, I will just point out how wrong that is. 

If nothing changes, why would they bother changing it?

 as I said, people keep getting the rule wrong or misunderstanding it or trying to twist it to use it in unintended ways.
but like I said
1. doesn't target a creature so can't be used with twin
2. you can use distant spell but it does distant spell doesn't effect your melee weapons range so it makes 0 difference (to double clarify while the spell does have range it requires you to do a MELEE weapon attack, not a SPELL weapon attack, distant spell doubles the range of the SPELL witch has nothing to do with the weapon attack the spell makes you do) 
3/4. you need a melee weapon to actually do the spell it does not work with unarmed/natural weapons

1. It does target a creature, as any spell with a range that says you attack a creature within the spells range obviously targets a creature, even if not directly stated in the text. 
2. If the spell says that you attack a creature within range, you attack a creature within range. The general reach of the weapon is overridden by the specific instructions of the spell. 
3/4. I never said that you can attack using unarmed or natural weapons, but you certainly can channel it through Find Steed or your beastmaster companion, RAW. 

Quote from Third_Sundering >>

1. It does target a creature, as any spell with a range that says you attack a creature within the spells range obviously targets a creature, even if not directly stated in the text. 
2. If the spell says that you attack a creature within range, you attack a creature within range. The general reach of the weapon is overridden by the specific instructions of the spell. 
3/4. I never said that you can attack using unarmed or natural weapons, but you certainly can channel it through Find Steed or your beastmaster companion, RAW. 

 1&2."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." this is the text from the spell text, this means you need to make a weapon attack within the range of the spell, so this actually means by doubling the range it allows you to move 5 feet without the spell failing, otherwise DOES NOT EFFECT THE RANGE OF YOUR MELEE WEAPON AND DOES NOT TARGET A CREATURE
3/4. I mean you can but the spell will fail so its a can't/shouldn't kind of thing

....weird take Proxy, and disagree with literally everything you said! :D

Quote from Chicken_Champ >>

....weird take Proxy, and disagree with literally everything you said! :D

 its not a weird take it is how it reads, it does not say "make a melee spell attack ageist a target" like shocking grasp it says " you must make a melee attack with a weapon against one creature within the spell's range" it doesn't say the weapon attack is part of the spell nor does it actually target a creature because the weapon attack targets said creature, and distant spell only effects the spells range not your melee weapons range, I was very clear and used quotes from the actually spell, I explained its interaction with distant spell and to be eligible for twined spell meta magic it must 1. target a creature (witch it does not) 2. only target ONE creature and 3. not have a range of self, I mean you can disagree if you want, you would be wrong but you can if you like.