Bug:

There is a bug where a Warforged using the darkwood core will add their proficiency bonus to their AC without satisfying the requirement to be proficient in light armour. This has occurred on my shadow monk skirmisher warforged at level 5. 

Extra details:

Their unarmoured defense score would be lower than the darkwood core calculation with light armorial proficienies. I am not receiving light armour proficiency from any source, having checked my character sheet view in Dndbeyond, it does not list that I have light armour proficienies just to be sure.

I've been playing with D&D Beyond for a short while now and noticed something as my character leveled up. Going from Level 4 to 5, as my proficiency increased, my armor class rose by one level.

This shouldn't have happened because as far as I can tell, Sorcerers have no armor proficiency and the natural armor of the warforged is 11 plus dexterity modifier. My AC was currently at 15 with a 0 dex modifier and a +1 AC ring of protection.

Did I happen to miss something about my character that would give me this effect or is there a mistake with D&D Beyond? Below is a link to the character if anyone would be willing to take a more in depth look.

https://www.dndbeyond.com/profile/Samurak/characters/6456356

https://www.dndbeyond.com/profile/Tdilly/characters/7917496

I’m playing a warforged wizard with no proficiency in light armor, but integrated protection is adding my proficiency bonus to my armor class when it shouldn’t. I can only add my proficiency bonus if I am proficient in light armor. 

I am also experiencing this bug. I created a Warforged Wizard with no armor proficiency. I have a dex bonus of +3. My AC should be 11 + Dex (3) for a total of 14 AC. However the calculation is using the normal rules for AC which is 10 + Dex and then adding dex again for the integrated core feature of the Warforged, giving me a total of 16 AC. So it appears the calculator is not picking up the Warforged base AC like it should.

https://www.dndbeyond.com/profile/DragonRiderDale/characters/9484494

Adding to this thread after thinking that posting in the character forum was the same as reporting a bug :/

I have a warforged monk that is experiencing this bug as well with a Dex of 18 and a Wis of 14.

Beyond says that my monk's AC is 10 + my Dex bonus (4) + "unarmored bonus (integrated protection)" (5), for a total of 19.

However, a monk's Unarmored Defense says that AC should be 10 + Dex (4) + Wis (2) to make AC 16.

If I go with the warforged Darkwood Core for integrated protection ('unarmored' so as to get access to monk class features), it would be 11 + Dex (4) for a total of AC 15, since monks don't have armor proficiency and I haven't taken a feat for proficiency (yet). 

I'm guessing that it's the inclusion of proficiency that's throwing the calculation off.