Verdict on AC Bonus stacking?

[Elves]

There are several classes that have an AC Bonus class feature that lets them add an ability bonus as an untyped bonus to AC while in no or light armor. I'm aware of monk, swordsage, ninja and some PRCs (Wis), battledancer from Dragon Compendium (Cha), and Fist of the Forest (Con).

Bonuses from the same feature don’t stack. My question is whether using a different ability score, as Fist and battledancer do, qualifies it as a different feature. The fact that all these features have the same name isn’t decisive, since to be redundant a feature also has to have the same effect.

Other things, notable or not:
-Fist of the Forest's feature includes a callout to the monk feature; battledancer's doesn't.
-The scaling bonus offered by battledancer's feature is a dodge bonus, while for everyone else it's untyped.
-Fist of the Forest sample NPC shows both features stacking. But to be fair, NPC statblocks are unreliable.


While the FAQ has no rules weight, people who are conservative about rulings often put RAI weight on it, so I'll quote its ruling on why swordsage and monk AC bonus don't stack:

"The swordsage’s AC bonus, allowing the swordsage to apply her Wisdom bonus to her armor class, mimics the ability of the monk’s AC bonus. Since these abilities share the same name and have the same effect, they will not stack."

This ruling bases itself on both features letting the character apply “her Wisdom bonus”. If it were a different ability it wouldn’t “have the same effect”. That implies stacking if the stat were different.

I don't know what the verdict should be here.

[Anthrowhale]

The stacking rules (https://www.d20srd.org/srd/theBasics.htm#stacking) say that things don't stack if they have either the same type or the same source. Ability modifer (https://www.d20srd.org/srd/theBasics.htm#abilityModifier) is a type, so you should not apply the same ability modifier twice, even if it comes from different sources.

The 'source' part is what you are asking about. I don't know a canonical definition of source, so it could be interpreted as "same name" (which seems simplest) or in some other way.

[Biffoniacus_Furiou]

RAW, we have:

DMG p21, under Bonus Types, third paragraph:
"Different named bonus types all stack, but usually a named bonus does not stack with another bonus of the same name, except for dodge bonuses and some circumstance bonuses."

Rules Compendium p21, under Stacking:
"Untyped bonuses stack unless the bonuses come from the same effect."

In either case, "same effect" or "same name" is not the same as "same ability score" any way you try to look at it. A Wis bonus is not a bonus type, so adding that to the same thing from multiple different effects or using different actual bonus types will stack.

Due to the RAW on "same name" we can't stack the Swordsage, Monk, or Ninja "AC Bonus" features because they're identically named. A Paladin of Tyranny or Slaughter who takes Blackguard has Divine Grace and Dark Blessing, and even though they're identical and both use the character's Cha bonus, they have different names and thus are not excluded from stacking by RAW. The Knight of the Unseelie Court (https://forums.giantitp.com/showsinglepost.php?p=17324416&postcount=6) adds its Cha bonus to its AC and saving throws multiple times via different sources and bonus types.

[Elves]

Ability modifer (https://www.d20srd.org/srd/theBasics.htm#abilityModifier) is a type
I'm not sure where the SRD is getting that. It's not listed as a type in DMG, PHB or RC.

Another difference is the SRD rule is for "modifiers to a given check or roll", which wouldn't even affect AC. The published books don't have that quirk.


"Same name" seems iffy as the only criterion for sameness given it has no mechanical import -- you could and likely do have things with the same name but different effects. FAQ seems to think it has to be same name AND same effect, hence the question -- does being based off a different stat qualify it as a different effect.

[Biffoniacus_Furiou]

Whether it's the same or a different ability score being added as a bonus is irrelevant.

A Gloura gets their Cha bonus to AC as a deflection bonus.
Arcane Duelist adds your Cha bonus to AC as a dodge bonus.
Mystic Wanderer adds your Cha bonus to AC as a sacred or profane bonus.
Ascetic Mage feat makes your Monk AC bonus use Cha instead of Wis.

All of those use your Cha bonus, but Cha bonus is not and cannot be the bonus type for anything. Each has a defined bonus type except Monk, which is an untyped bonus.

[Elves]

I'm talking about the AC Bonus features only. My point is:


Due to the RAW on "same name" we can't stack the Swordsage, Monk, or Ninja "AC Bonus" features because they're identically named.

Same name alone doesn't necessarily make them the same source. For example, FAQ takes same source to mean same name + same effect. Wis to AC and Cha to AC/Con to AC aren't necessarily the same effect.

FAQ is not RAW, but in this case I find its interpretation reasonable -- name alone doesn't work as the criterion since you can easily have abilities with the same name but different effects.

For example, say you had another class with a feature called AC Bonus that grants a +1 bonus to AC for 1 round when you cast a spell. Is it desirable to conclude that it wouldn't stack with the monk's AC Bonus? They have the same name, but work very differently. Their name is irrelevant to their mechanics, so why should it alone mean they don't stack? Name+effect is the only reasonable reading.

Question then is whether basing off a different ability score is enough to qualify as a different effect.

[rrwoods]

RAW is definitively unclear, period. All arguments one way or the other (including mine, presented here) are, necessarily, interpretations. The rules do not define “source”, and they certainly don’t specify what “same” means in reference to whatever a “source” is.

My interpretation is that the “same source” rule doesn’t apply to class features that happen to have the same name but are from different classes. Even if they work identically. What it does apply to is, for example, multiple castings of the same spell (or power, or maneuver, or ...).

[Elves]

Coming back to this, I am on the side of them stacking. I don't see how "Charisma bonus to AC" and "Wisdom bonus to AC" can be defined as the same effect. And per my post above it doesn't seem functional for name alone to be decisive. Add that the circumstantial evidence (NPC statblock) leans this way, and the burden of proof is on the other position.

[Kelb_Panthera]

I'm not sure where the SRD is getting that. It's not listed as a type in DMG, PHB or RC.


PHB 304, in the glossary.

[Anthrowhale]

DMG p21, under Bonus Types, third paragraph:
"Different named bonus types all stack, but usually a named bonus does not stack with another bonus of the same name, except for dodge bonuses and some circumstance bonuses."

Rules Compendium p21, under Stacking:
"Untyped bonuses stack unless the bonuses come from the same effect."


PHB 304, in the glossary.
Interesting, so the rules also are not consistent on what constitutes a modifier/type.

More conservative readings (less stacking) are more universally accepted, but the degree of ambiguity here seems sufficient for many different choices depending on the DM.

[Biggus]

FAQ is not RAW, but in this case I find its interpretation reasonable -- name alone doesn't work as the criterion since you can easily have abilities with the same name but different effects.

For example, say you had another class with a feature called AC Bonus that grants a +1 bonus to AC for 1 round when you cast a spell. Is it desirable to conclude that it wouldn't stack with the monk's AC Bonus? They have the same name, but work very differently. Their name is irrelevant to their mechanics, so why should it alone mean they don't stack? Name+effect is the only reasonable reading.

Question then is whether basing off a different ability score is enough to qualify as a different effect.

I agree that different ability score bonuses should stack but same ability score bonuses shouldn't, partly because it makes sense in terms of the former being the same bonus type and the latter not being, but also in terms of game balance. It would make it too easy to boost a single ability score into the stratosphere and get an unbeatable AC from it.

If there's any ambiguity about a rule, "choose the interpretation that doesn't help to break the game" is good DMing practice in my opinion. I'm sure some people will disagree.

[Max Caysey]

There are several classes that have an AC Bonus class feature that lets them add an ability bonus as an untyped bonus to AC while in no or light armor. I'm aware of monk, swordsage, ninja and some PRCs (Wis), battledancer from Dragon Compendium (Cha), and Fist of the Forest (Con).

Bonuses from the same feature don’t stack. My question is whether using a different ability score, as Fist and battledancer do, qualifies it as a different feature. The fact that all these features have the same name isn’t decisive, since to be redundant a feature also has to have the same effect.

Other things, notable or not:
-Fist of the Forest's feature includes a callout to the monk feature; battledancer's doesn't.
-The scaling bonus offered by battledancer's feature is a dodge bonus, while for everyone else it's untyped.
-Fist of the Forest sample NPC shows both features stacking. But to be fair, NPC statblocks are unreliable.


While the FAQ has no rules weight, people who are conservative about rulings often put RAI weight on it, so I'll quote its ruling on why swordsage and monk AC bonus don't stack:

"The swordsage’s AC bonus, allowing the swordsage to apply her Wisdom bonus to her armor class, mimics the ability of the monk’s AC bonus. Since these abilities share the same name and have the same effect, they will not stack."

This ruling bases itself on both features letting the character apply “her Wisdom bonus”. If it were a different ability it wouldn’t “have the same effect”. That implies stacking if the stat were different.

I don't know what the verdict should be here.

AFAICT it stacks fine... i.e. the battledancer and fist of the forest that is!

[Elves]

PHB 304, in the glossary.
I see "ability modifier". It doesn't call it a bonus type.


Interesting, so the rules also are not consistent on what constitutes a modifier/type.

More conservative readings (less stacking) are more universally accepted, but the degree of ambiguity here seems sufficient for many different choices depending on the DM.
It not being included in the presumably comprehensive RC "Bonus Type" list seems telling.

[Kelb_Panthera]

I see "ability modifier". It doesn't call it a bonus type.

"Modifier" includes both bonuses and penalties. You wouldn't expect it to say bonus when some characters/ creatures have ability scores of <10.



It not being included in the presumably comprehensive RC "Bonus Type" list seems telling.

The rules compendium was a mistake. It doesn't do an adequate job of clarifying some issues and "clarifies" (read; nerfs) a number of things that were already quite clear. I also don't know why you'd presume that was comprehensive rather than simply illustratory using a number of the most common bonuses.

[Elves]

"Bonuses are classified by type, as described here." Not here are a list of the most common types. Sounds authoritative.

Add to it their exclusion from the stacking rules elsewhere...


Do we have examples where being able to stack the same ability bonus would be genuinely problematic, rather than simply powerful?

[Kelb_Panthera]

"Bonuses are classified by type, as described here." Not here are a list of the most common types. Sounds authoritative.

It's also not "this list is complete/exhaustive/comprehensive/<synonym>." You're adding that yourself.


Do we have examples where being able to stack the same ability bonus would be genuinely problematic, rather than simply powerful?

Probably not. You've got to go aways out of the way to grab multiple instances of getting an ability mod to a given statistic for the most part and its virtually never a primary stat or associated with a SAD class.

[Anthrowhale]

It not being included in the presumably comprehensive RC "Bonus Type" list seems telling.


The rules compendium was a mistake.
I like to aim for builds that are legal under both sets of rules since controversy about legality is not fun. In terms of contents, some of the RCs quiet nerfs seem fairly reasonable. However, I'd have to agree that the RC sets up an inherent rule confusion as a book that few people have which overrules other books which claim they are authoritative.

[Elves]

It's also not "this list is complete/exhaustive/comprehensive/<synonym>." You're adding that yourself.
"classified by type, as described here". Seems clear. DMG, in its list which also doesn't include ability bonuses, says "each type is briefly described below." Even more explicit than RC. Nor are they mentioned in the PHB's section on stacking, nor is bonus type used in FAQ as the rationale for monk + ss AC not stacking.

It seems that while it may be a bonus it's not considered a type for the purpose of stacking.

I hadn't realized that, but it's interesting because it could allow significant expansion to the type of Cha to X build biffoniacus_furiou linked.


Now if you add your ability mod twice to something, can you still only add the part of it resulting from an enhancement bonus to that ability once? No, I guess you could add its benefit multiple times, because it's affecting your ability, not the roll directly.

[Darg]

Ability modifiers do not stack with themselves. At least, I've never encountered a situation where an ability bonus is stacking with itself. You usually get abilities that use the ability modifier to calculate it's own bonus or replace a modifier such as the deepwarden's stone warden ability. The prior stack as the ability modifiers are not the benefit. The latter would overwrite with other similar abilities because they are replacing, not adding a benefit.

Seriously, anybody have a source that says "You gain a +4 bonus to your strength modifier"? All I have ever seen is bonuses to ability scores. The only thing I can think of are feats like improved trip, but obviously it stacks because then the maneuver description wouldn't make sense with the size bonuses and things. Colossal creatures with only a +4 bonus would be fun.

[Elves]

The example I was thinking of is Moonwarded Ranger's "Armor of the Senses". Like monk's AC Bonus, it adds Wisdom bonus to AC.

[Darg]

The example I was thinking of is Moonwarded Ranger's "Armor of the Senses". Like monk's AC Bonus, it adds Wisdom bonus to AC.

The question is whether it is the wisdom modifier or the ability providing a modifier equal to the wisdom modifier. I say it is the second. Duelists canny defense ability adds the dex and Int modifiers together. If they didn't stack, then the ability could not function.

On another note, wow I never realized moon-warded ranger could stack x/- damage reduction from any source by 6th level.

[Elves]

Looks to me like Wis modifier, which the feature merely allows you to add, but that may not rule out stacking, see my posts above -- DMG and RC provide comprehensive lists of bonus types for stacking purposes and ability bonus isn't included.

Stacking ability modifiers of different types is uncontroversial as PHB calls ability modifier "The bonus or penalty associated with a par-ticular ability score".

[Zanos]

While the FAQ has no rules weight, people who are conservative about rulings often put RAI weight on it, so I'll quote its ruling on why swordsage and monk AC bonus don't stack:

"The swordsage’s AC bonus, allowing the swordsage to apply her Wisdom bonus to her armor class, mimics the ability of the monk’s AC bonus. Since these abilities share the same name and have the same effect, they will not stack."
Based on this I'd say that if two abilities are both named AC Bonus, and one adds Wisdom and another adds Charisma, they would stack. If they are both named AC bonus and both add Wisdom, they would not stack. Adding Charisma to AC and adding Wisdom to AC are different effects. If they have different names you can stack them as much as you like.

Even without the FAQ ruling this looks like an Untyped bonus to me, and that fits the general rule of Untyped bonuses from the same source not stacking. That's my two copper, anyway.

[Zaile]

Based on this I'd say that if two abilities are both named AC Bonus, and one adds Wisdom and another adds Charisma, they would stack. If they are both named AC bonus and both add Wisdom, they would not stack. Adding Charisma to AC and adding Wisdom to AC are different effects. If they have different names you can stack them as much as you like.

Even without the FAQ ruling this looks like an Untyped bonus to me, and that fits the general rule of Untyped bonuses from the same source not stacking. That's my two copper, anyway.

Totally agree and that's how most of my DMs interpreted it. The AC bonus wording morphed as 3e went along.

The AC Bonus features of the same name don't stack unless: It specifically says so, OR they operate off different stats(Fist of Forest), OR provide different typed bonuses (enhancement, insight, etc.)

It is worth noting the differences. For example:

"Add your wisdom modifier as a insight/competence/dodge/enhancement/etc. as a bonus" is easy and is a named bonus of that type.

"Add your wisdom modifier as a bonus to your AC" (and similar wording) is not untyped, but is a "wisdom bonus" as pointed out above. The same goes for each stat.

"Add your wisdom modifier and an untyped bonus to your AC" OR "Add your wisdom modifier to your AC" (specifically without the word "bonus"). These wordings should be the only one ever treated as an untyped bonus.

Edit: Added untyped.

[Elves]

"Add your wisdom modifier and an untyped bonus to your AC" This wording should be the only one ever treated as an untyped bonus.

Very rarely is the "untyped" wording actually used in the rulebooks though. What often comes up is that you're not applying the statmod directly, but rather gaining a bonus equal to your ability mod (eg paladin's Divine Grace), which is therefore untyped. Moot point however if as it seems ability bonuses do stack.

[Zaile]

Very rarely is the "untyped" wording actually used in the rulebooks though. What often comes up is that you're not applying the statmod directly, but rather gaining a bonus equal to your ability mod (eg paladin's Divine Grace), which is therefore untyped. Moot point however if as it seems ability bonuses do stack.

That's true! I knew I forgot something.

"A bonus equal to your X modifier" is indeed untyped unless it states it is a enhancement, insight, etc.