Do riders provoke Attack of Opportunity?

Question

Attack of Opportunity has this trigger:

A creature within your reach uses a manipulate action or a move action, makes a ranged attack, or leaves a square during a move action it’s using.

If you are riding, none of this applies:

• uses a manipulate action: Command an Animal does not have the manipulate trait
• uses a move action: Command an Animal does not have the move trait
• leaves a square during a move action it’s using: the rider leaves a square, but it is during a move action someone else (the mount) is using
• it is obviously not a ranged attack

Am I correct you cannot make an AoO against the rider, only the mount?

Answer 1

Attack of Opportunity Targets the Mount

Here's from the effect of Attack of Opportunity:

Make a melee Strike against the triggering creature. If your attack is a critical hit and the trigger was a manipulate action, you disrupt that action.

As you've pointed out, the rider never triggers an Attack of Opportunity. Only the mount that's been commanded to take a provoking action would trigger the reaction and be targeted by the Strike.

There is a line under Mounted Combat about how attackers can target either rider or mount, but that doesn't change how Attack of Opportunity only targets the character that triggers the reaction.

Answer 2

Technically, no, they do not provoke attacks of opportunity... probably

You've spelled out all the reasons for this quite nicely already: Commanding and Animal is not a manipulate action nor a move action and the one who is actually moving is the mount. Thus, the attack of opportunity can only target the mount.

Of course, this is a strict reading of the rules and a GM is free to say otherwise and rule that the rider in fact can be targeted. That all said...

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Maybe attackers can target the rider

This case would probably rely on interpreting this specific line:

When you’re mounted, attackers can target either you or your mount. [...]

Is this just helper text mentioning something that probably didn't need to be stated? Is this saying that when any attack specifically targets one of you, the attacker can opt to target the other? It's unclear to me exactly what function or purpose this text serves and it'll be up to the GM to decide whether this means attacks of opportunity targeting a mount can be redirected to target its rider.