Do unfettered defense and canny defense stack?

Question

I would like your opinion on basically what I've asked in the title. The rules presented are as follows:

Duelist: Canny Defense (DMG 185):

When not wearing armor or using a shield, a duelist adds 1 point of Intelligence bonus (if any) per duelist class level to her Dexterity bonus to modify Armor Class while wielding a melee weapon. (...) If a duelist is caught flat-footed or otherwise denied her Dexterity bonus, she also loses this bonus.

Invisible Blade: Unfettered Defense (CW 46):

An invisible blade benefits from an increased survival instinct during combat. Because of this sixth sense, he adds 1 point of Intelligence bonus (if any) per invisible blade class level to his Armor Class in addition to any other modifiers he would normally receive. If the invisible blade is caught flat-footed or is otherwise denied his Dexterity modifier to Armor Class, he also loses this bonus. Unfettered defense functions only when an invisible blade is not wearing armor and is armed with one or more daggers, kukris, or punching daggers as his only weapons.

Both add the Intelligence modifier to AC, which would speak against stacking.

However, if we go into more details, Canny Defense adds INT to the DEX bonus to AC while Unfettered Defense adds INT directly to AC. In addition, neither state the type of bonus. So it seems they are untyped (or not of the same type) and do not have the same source, which means they could stack.

Also both seem to follow the rules of the dodge bonus (as in "not working if flat-footed or denied the DEX bonus to AC"), so if they are dodge bonus, they could also stack.

Answer 1

Yes, they “stack.” As you note, they are not even actually bonuses to the same thing, so they don't even “see” one another, no way for them to interact.

But more importantly, these are two untyped bonuses from separate sources. Even if they both added directly to AC, they would still stack. “Intelligence” is not a type of bonus—that just tells you the value of the bonus (equal to your Intelligence bonus). The reuse of words here can be confusing, but ultimately the rules are unambiguous on this.

You may also be thinking of a rule added in Pathfinder, which says that you cannot add the same ability modifier to a given thing more than once. There, the fact that these abilities technically add to different things would be important.

Finally, note that both of these classes is very, very underpowered. The invisible blade had some decent things but has absurdly expensive prerequisites—many of which are useless to the class because of poor editing (it was originally a 10-level class with more throwing features, and the requirements were never adjusted after it lost those levels and features). The duelist is just... abysmal, one of the weakest classes in the game. Please be very careful when considering either class.