When I added the +1 weapon potency rune to my warhammer in Pathbuilder, it gained the magical trait. When I later added the flaming rune to see what would happen, it gained the fire trait. Is Pathbuilder correct? Do items with runes gain the traits of those runes? I could have sworn this was a rule, but I can't find it anywhere.
I did find this in Player Core, though.
You can’t cast fire spells or use actions with the fire trait underwater. As normal for how traits work, any part of the effect that’s unrelated to fire still works. For example, an attack with a flaming battleaxe could still deal its physical damage, just not its fire damage.
This implies that the flaming rune grants the fire trait not just to the weapon but to the Strike itself. I can't find the rule itself though.
This was a rule that was removed early in the game's life cycle.
There is the rule regarding Fundamental Runes:
A potency rune is what makes a weapon a magic weapon or armor magic armor.
So adding the potency rune should be adding the Magical trait to the weapon itself. Or the armor in the case of armor.
Adding the fire trait to a weapon for a flaming rune is a bit more of a question. But ultimately I don't think it makes all that much difference. The Strike action doesn't get traits added to it due to the traits of the weapon used.
So you can definitely swing the flaming battleaxe underwater. The fire damage won't work, but Strike itself doesn't have the fire trait.
So when the rule says "As normal for how traits work," is it talking about the Immunity to Complex Effects rule or something else?