Do resistances from class and Ancestry stack?

Question

The Kobold ancestry can lead to you gaining a resistance vs. fire while the dragon disciple archetype dedication can do the same. If you have both do these stack or does only one of them count?

Answer 1

Probably not

It's a little ambiguous.

From the rules about Resistances:

If you have more than one type of resistance that would apply to the same instance of damage, use only the highest applicable resistance value.

(emphasis mine)

Resistances don't normally have types (e.g. status, circumstance, item), so "type of resistance" most likely doesn't refer to that. Therefore it could refer to the damage type being resisted (previously referred to in that section as "resistance to a type of damage"), or the source of the resistance (i.e. type meaning resistance from an item, from a feat, from an ancestry). I'd lean toward the second interpretation, given that there is already verbiage for the first and this wording is different. Additionally, such an interpretation seems implied by the Energy-Resistant Armor Rune:

Multiple energy-resistant runes can be etched onto a suit of armor; rather than using only the highest-level effect, each must provide resistance to a different damage type. For instance, a +2 acid-resistant greater fire-resistant breastplate would give you acid resistance 5 and fire resistance 10.

Again, not exactly unambiguous, but given these examples it is best to interpret resistances as not stacking. If it was okay for resistances to stack, then it seems odd to prohibit that from happening on magical armor runes.