Discovered recently that one of my warforged players had an AC of 27. Part of the problem was my own lack of paying attention to magic item use, but the biggest issue is that AC calculation is not taking into account that when a class or racial feature gives a player two different options to calculate AC (i.e, 10 + Dexterity Modifier + etc.) it is not forcing the choice, at least in this case of a Warforged Barbarian.

The armor class, based on the guidance on page 2 of the official WotC Sage Advice Compendium document should be either the player chooses one type of Integrated Protection (Warforged racial feature) OR the barbarian Unarmored Defense feature. They are not supposed to stack. From the document:

”These methods—along with any others that give you a formula for calculating your AC—are mutually exclusive; you can benefit from only one at a time.”

In my case, because the player is using the Darkwood Core option which is listed as “unarmored,” the base AC for calculation is starting at 11, and thus the barbarian Unarmored Defense feature is stacking.

I have not tested this on the Tortle (the only other race with an AC calculation option) but with WGtE heading towards final release it may be something to look at.

If you click on their AC in their character sheet you will see how the AC is being calculated and what bonuses come from where.

It's quite possible that the player gave themselves a static override value or a miscellaneous bonus in error.

My apologies. I had emailed the player about this prior to posting, and it seems they've made requested changes and their AC is calculating normally.