Necklace of Elemental Augmentation + Potent Robe

[Metallicus]

Do these two items listed in the title stack the Charisma Bonus twice or can you only use one at a time? It isn't obvious to me even from the combat log.

[Kappa]

They do stack, and it's imo quite clear on the combat log if you hover the damage output.

You should see 3 flat damage ( Charisma, amulet and robe, plus the damage ) on a standard cantrip ( you can get one extra stack if you play a draconic sorcerer or a warlock, respectively on a specific element or eldritch blast ).