How is Sneak supposed to interact with reactions?

[Roadie]

When you Sneak, you roll Stealth at the end of your movement, but the hidden or undetetected condition granted by it applies "during" your movement, e.g., retroactively.

Consider the following time paradox:

- You're in concealment and hidden, and Sneak through the melee reach of a enemy with Attack of Opportunity, towards a square where there's an effect that (unknown to you) gives you a penalty to Stealth.

- The Attack of Opportunity enemy attacks you, succeeds on the flat check against hidden, and hits you for X damage. He uses a secondary ability with AoO to make you stop your movement in that square.

- The Stealth roll for Sneak is successful, making you undetected—"during" your movement. Which means that the Attack of Opportunity guy can't have hit you and made you stop, because he wouldn't have been able to trigger Attack of Opportunity in the first place.

- This means you take your full movement, ending in the square with the Stealth penalty. You fail on your Sneak attempt, making you only hidden again—"throughout" your movement.

- This means that during your movement, the Attack of Opportunity attacks you, succeeds on the flat check against hidden, and hits you for X damage. He uses a secondary ability with AoO to make you stop your movement in that square.

- Without the Stealth penalty, the Stealth roll for Sneak is successful, making you undetected—"during" your movement...

Maybe Golarion blows up from the feedback loop? Groetus is probably pretty annoyed that somebody's stolen his job.

Is there an intended resolution for this kind of thing that was never printed? Did the designers just forget about reactions when writing up the Sneak action?

[Jared Walter 356]

This is an prime example of why GMs have some leeway. Couple of points to remember though:

1) The stealth check is a secret check, meaning the Gm should be making this check.
2) if you are undetected to a creature, it cannot target you with reactions involving your movement unless you before hidden or observed.
3) There is a guideline for ambiguous or non-sensical rules:
Ambiguous Rules
Sometimes a rule could be interpreted multiple ways. If one version is too good to be true, it probably is. If a rule seems to have wording with problematic repercussions or doesn’t work as intended, work with your group to find a good solution, rather than just playing with the rule as printed.

So work with GM & players to provide a reasonable resolution.

I would resolve it this way:
1) Player declares intention to sneak, his path, and final intended location.
2) GM makes secret sneak check (including any terrain penalties for any square moved through)
3a) If Player succeeds, no AOA.
3b) If player fails, AOA (against hidden)and any applicable riders.
3c) If player critically fails AOA without hidden and any applicable riders.

In my mind, the check is not retroactive, but is rolled only once for convenience after the actin is declared.

[Szadek]

The GM does not have to roll secret checks if the group would rather roll the bones. Even states it in the rules regarding secret rolls.