Cometary Collision vs a Large opponent's AoO

Question

So I have this situation: Largo the Large, who is Large (and a humanoid, so he gets reach), charges Count Countercharge, who has readied his Cometary Collision feat, and is Medium-sized.

The question is: does Largo, RAW, get an AoO on the Count?

The reasons I would think not are:

1. I seem to recall that you cannot take an AoO on your own turn, but I can't find where I got that from.

2. Is an AoO during a charge possible? I think not - again, I can't source why.

Answer 1

Largo can, in fact, take the attack of opportunity. Nothing says you can only take attacks of opportunity when it is not your turn, and nothing says you cannot take an attack of opportunity while doing something else. Attacks of opportunity are not actions, so one occurring in the middle of a full-round action like charge is permissible.

It’s impossible to prove a negative, but the rules on attacks of opportunity simply mention nothing of the sort.

1. The word “turn” is only used three times, and all for explaining how attacks of opportunity interrupt a turn, and after one is resolved that turn continues. The rules do say that you can perform an attack of opportunity “even when it is not your action,” (emphasis mine), but the word “even” here indicates that this is an inclusive statement, not an exhaustive one—you can do so “even” when you might otherwise expect you couldn’t. That implies that not only you can when it is “your action,” but that this is considered by the author to be the more expected case (and indeed, for other combat happenings, it would be).

2. The word “action” is used eleven times—once in the above quote about attacking “even when it is not your action,” and then ten times to describe various sorts of actions that provoke. Note the unusual phrasing “your action” to indicate your turn—this was common early on in 3.5e, and was avoided in later books as it was confusing.

So anyway, the flow here would be that Largo begins to charge, triggering the Count’s readied action. That interrupts Largo’s charge, and begins the Count’s charge. When the Count begins to close from within 10 feet of Largo to within 5 feet, he provokes Largo. That interrupts the Count’s charge, allowing Largo to take an attack of opportunity. Once Largo has done that, the Count’s interrupted charge resumes, and the Count moves adjacent to Largo and attacks with the relevant bonuses. With that resolved, Largo’s own action resumes, allowing Largo to either hit Count or continue his charge on to his original target (providing Count is not in the way now).

If we wanted to make this more ridiculous, we could have Largo take his attack of opportunity with an unarmed strike but without Improved Unarmed Strike—causing him to provoke the Count, who would get an attack of opportunity before Largo got to complete his. The rest of the events would resolve the same.

Answer 2

You can take actions in the middle of another action, but any action other than a free action ruins the remaining portion of your initial action.

Relevant rules part here is:

Free Action
... You can perform one or more free actions while taking another action normally...

Now if it has to be pointed for free actions it means you can't generally take another action normally while you perform another action.

Some examples: you end your movement when you attack and remaining portion is wasted, if you do something while you cast a spell it fizzles, you can't continue full-attack after you move your speed in the middle of it even if you have additional move action on your turn. Some of those examples can be changed with exceptions, but an existence of exceptions only strengthen general prohibition.

So for your example Largo can take an attack of opportunity, but then he can't continue his charge. Or he can avoid using attack of opportunity and either continue his charge if path isn't now blocked or attack Count as if he charged him if Count is in the way.

Also, some people may say attacks of opportunity aren't actions. Sure they lack action type. But consider dazed creature, the only effect of the condition being: "a dazed creature can take no actions". Would you allow it to make one?

Attacks of opportunity are also listed as an exception here:

The Combat Round
... When a character’s turn comes up in the initiative sequence, that character performs his entire round’s worth of actions. (For exceptions, see Attacks of Opportunity and Special Initiative Actions.)

meaning they are also actions, but aren't performed on a character’s turn.