Is an artificer's homunculus servant's passive Perception affected by its Might of the Master trait?

Question

An Artificer's homunculus servant has the following ability:

Might of the Master. The following numbers increase by 1 when your proficiency bonus increases by 1: the homunculus's skill and saving throw bonuses (above) and the bonuses to hit and damage of its attack (below).

One of the the listed skill bonuses is +4 to perception. In addition, the homunculus also starts with a passive perception score of 14, consistent with that perception bonus. Does this passive perception score increase along with the homunculus' perception bonus when the Artificer's proficiency bonus increases? For example, what is the passive perception score for a homunculus controlled by a level 5 artificer (whose proficiency bonus is +3)?

Answer 1

Yes. Passive Perception is based on Perception modifier.

The rules on passive checks state:

Here's how to determine a character's total for a passive check:

10 + all modifiers that normally apply to the check

If the character has advantage on the check, add 5. For disadvantage, subtract 5. The game refers to a passive check total as a score.

For example, if a 1st-level character has a Wisdom of 15 and proficiency in Perception, he or she has a passive Wisdom (Perception) score of 14.

Thus, anything that increases a creature's Perception modifier will also increase its passive Perception score.

As quoted in the question, the Homunculus Servant from the artificer's Homunculus Servant infusion has the Might of the Master trait, which increases its "skill bonuses" when the artificer's proficiency bonus increases.

(Note: since your proficiency bonus is based on character level and not class level, this means that for multiclassed character, this continues to gradually go up when you level up in any class, not just in the artificer class.)

As a result, when your proficiency bonus goes up, both your homunculus servant's Perception bonus and passive Perception score will increase with it (along with its Stealth bonus, Dexterity saving throw bonus, and its to-hit and damage rolls as well).