How much of a damage bonus does jousting grant?

[Ravingdork]

Jousting trait: The weapon is suited for mounted combat with a harness or similar means. When mounted, if you moved at least 10 feet on the action before your attack, add a circumstance bonus to damage for that attack equal to the number of damage dice for the weapon. In addition, while mounted, you can wield the weapon in one hand, changing the damage die to the listed value.

One of my players just asked me the following: How do you think the rules for the jousting trait interact with things like deadly, striking runes, and Power Attack? Is it +1 damage for each damage die? or just for the base weapon?

I responded with the following: The jousting trait specifically calls out "damage dice for the weapon." This leads me to believe that it's just the weapon dice (this is, those from the base weapon, and striking, greater striking, and major striking runes). We'll be going with that interpretation until someone finds some compelling evidence otherwise.

I'm now looking for second opinions on the matter, as a matter of being thorough. Does anyone have any compelling evidence that it should be different than what I've thus far ruled?

[Elicoor]

That was a logical ruling on the fly, however things are a bit more complex. There are multiple different cases here.

Striking runes: They increase the number of weapon damage dice. So every rank of striking rune increases the circumstance bonus by +1.

Deadly adds a weapon damage dice on a critical hit. As a critical hit-conditional effect, it's not doubled. And the +1 from jousting should follow the same rule.

Power attack: "You unleash a particularly powerful attack that clobbers your foe but leaves you a bit unsteady. Make a melee Strike. This counts as two attacks when calculating your multiple attack penalty. If this Strike hits, you deal an extra die of weapon damage. If you’re at least 10th level, increase this to two extra dice, and if you’re at least 18th level, increase it to three extra dice."
As such, jousting should apply to these dice too.

There's no clear difference between "damage dice for the weapon", "weapon damage dice", "extra die of weapon damage". But if we try to consider only the logical aspect, you always add weapon damage dice, and jousting should apply every time (except for doubling the +1 from deadly in case of a critical).

[Blave]

Ravingdork wrote:

I responded with the following: The jousting trait specifically calls out "damage dice for the weapon." This leads me to believe that it's just the weapon dice (this is, those from the base weapon, and striking, greater striking, and major striking runes). We'll be going with that interpretation until someone finds some compelling evidence otherwise.

This is absolutely correct by RAW.

Counting Damage Dice, CRB pg. 279 wrote:

Effects based on a weapon’s number of damage dice include only the weapon’s damage die plus any extra dice from a striking rune. They don’t count extra dice from abilities, critical specialization effects, property runes, weapon traits, or the like.

Source.

[Squiggit]

Blave is correct... although I think it's needlessly confusing that Paizo specifically called out these abilities as adding "weapon damage die" and then putting a clarification in somewhere that they aren't real weapon damage die.