Does Aid Another Break Invisibility?

Question

When using the Aid Another action, does it break invisibility? I'm inclined to say no, because you're not actually attacking a creature, you're making an attack roll against a flat AC of 10.

Aid Another

In melee combat, you can help a friend attack or defend by distracting or interfering with an opponent. If you're in position to make a melee attack on an opponent that is engaging a friend in melee combat, you can attempt to aid your friend as a standard action. You make an attack roll against AC 10. If you succeed, your friend gains either a +2 bonus on his next attack roll against that opponent or a +2 bonus to AC against that opponent's next attack (your choice), as long as that attack comes before the beginning of your next turn. Multiple characters can aid the same friend, and similar bonuses stack.

You can also use this standard action to help a friend in other ways, such as when he is affected by a spell, or to assist another character's skill check.

Answer 1

Yes, it does end. The general rules for magic state:

Some spell descriptions refer to attacking. All offensive combat actions, even those that don't damage opponents, are considered attacks.

Aiding Another, because it either makes an opponent more vulnerable to attack or less able to attack back, is an offensive combat action. Here are the rules again, appropriately emphasized:

In melee combat, you can help a friend attack or defend by distracting or interfering with an opponent. If you’re in position to make a melee attack on an opponent that is engaging a friend in melee combat, you can attempt to aid your friend as a standard action. You make an attack roll against AC 10. If you succeed, your friend gains either a +2 bonus on his next attack roll against that opponent or a +2 bonus to AC against that opponent’s next attack (your choice)

It's clear that this is directed specifically against a particular foe, and that you must be able to attack that foe in melee, and that your actions are directed against that foe. That's a textbook non-damaging offensive combat action.

Answer 2

I'd say yes, aid another does break invisibility.

Strictly going by the RAW we have from the Invisibility spell:

The spell ends if the subject attacks any creature. For purposes of this spell, an attack includes any spell targeting a foe or whose area or effect includes a foe.

From the aid another action, which you quote:

If you're in position to make a melee attack on an opponent that is engaging a friend in melee combat, you can attempt to aid your friend as a standard action. You make an attack roll against AC 10.

Short story: You make an attack and the spell ends.

Longer story, based on the comments: Granted, the description of the aid another action does not explicitly say that the attack roll is directed at the opponent. However, an attack roll presupposes an opponent. Thus the attack roll is targeted at the opponent.

Answer 3

To break invisibility: Attack another creature.

To aid another: Attack AC 10.

AC 10 is not a creature.

Another poster interprets "all offensive combat actions are considered attacks" to mean anything that "either makes an opponent more vulnerable to attack or less able to attack back, is an offensive combat action". Under that kind of interpretation, buffing yourself for combat is an attack if it improves your attack bonus.

Under that interpretation, becoming invisible would be an offensive action and immediately make you not invisible again, since it does both of those things. So would casting Expeditious Retreat. Or using a single move action to move your speed. Tripping an opponent for no damage is offensive. Disarming an opponent for no damage is offensive. Aiding your friend is not offensive any more than casting the Haste spell is.