Magus Arcane Enhanced Weapon VS Sunder?

[Matt2VK]

Magus has a +2 weapon and uses his arcana pool to enhance the weapon to a +4 keen weapon.

Opponent Magus is fighting tries to sunder that weapon.

Question -
Is the weapon treated as a +2 weapon or as a +4 keen weapon for figuring out the sunder attempt?

[Nefreet]

It's treated as +4. The Keen has no effect on Hardness or HP calculations. So you'd get an extra +4 Hardness on top of what your +2 weapon already has, and an extra +20 HP.

Unfortunately, I've never gotten an answer on what happens to those "temporary" hit points after the extra enhancement goes away. It's kind of like when an Enlarged character's weapon shrinks. Whatever damage your weapon sustained is still there, so its possible for a weapon to only be broken, and the moment it returns to normal become destroyed.

(My sundering Magus deals with this a lot...)