Every group I've been a part of has had at least one player (and it's usually just one) that is convinced that the AP doesn't account for "unexpected" character actions. This is often expressed by the player saying something along the lines of "Unexpected error; the writers did not think you would do this."
Examples would be things like a player assuming the AP doesn't account for a character learning a secret about someone, using knowledge to their advantage, sneaking into a place, getting into a building earlier than the player thinks they should be able to, etc.
Someone thinking this isn't really a problem, but when they start to sway the group actions and it feels like the group is trying to guess what the AP expects them to do/they start to treat the AP as if it's on rails... that can become a problem.
Beyond suggesting that players should read an AP (obviously not the one they're playing through) so that they can understand how they're written and trying to explain that the Paizo writers have no preconceived notions about what abilities any particular group will have, does anyone have any advice on how to avoid this particular problem?
Don't play APs?
It's not really a fixable one, because it's a matter of perception. The APs tend to account for the most common methods of player action, and provide enough details on who the bad guys are and what they're about that the GM can react appropriately if the players pull out an unexpected scroll of Etheral Jaunt.
If the GM adapts, then it looks like the AP expected the action. If the AP has pre-emptively written about the option the player is taking, then it is actually an expected action.
Players can delibrately try to break the rails, but this usually involves either outright stupid decisions ("Let's attack the vastly overwhelming forces head-on, because the AP doesn't expect us to!"), or actively endeavouring to break the game ("Instead of getting back this NPC's wedding ring, let's leave the River Kingdoms entirely and go become pirates in Mwangi!"), so players don't generally take such actions.
The best you could do is play out the player's unexpected plan, then copy the relevant text out of the AP and hand it to the players so they could see the characters have autonomy.
For me this would mainly be a problem with APs that give insufficient motivation for the PCs. I'm currently struggeling with this in serpent skull. There my original PCs just left the group and I made a new better fitting one.
We also had some fun twists within APs for our DM. It was his first time and we sort of reversed a dungeon. It was a tower and we climbed to the top at night and worked our way downards instead of storming the front gate. Took him quite by supprise at that time but he rolled with it and it was a lot of fun.
Also in Kingmaker we had a LG multiracial kingdom. Basically every tribe/race/... was offered to joun peacefully and be part of all the benefits as long as they lived by the laws. Very few needed convincing or decided to break the law. At that point judgement was swift and drastic with the king being a paladin of ragathiel....
In the end it's to some amount up tp the players what they want to do but also depends on the AP.
If you want full freedom APs won't really work well.
My advice would be to discuss the expectations of players and DM as a group and see what kind of adventure will fit.
avr -- Even in homebrew adventures it happens. Players assume the GM has one solution in mind. But hey, thanks for your useful and insightful reply.
Pink Dragon -- It's happened as me being a player as well as a GM in different games. It's not a huge issue, but I worry that players may, on occasion, feel like there's certain things they're supposed to do rather than being able to solve (or ignore) problems however they see fit.
The one that prompted me to post this is that there's a murder mystery. The AP is written in such a way that it lists how the villain is doing it, where they are, and how they get there. How the players figure it out is completely up to them and the AP doesn't even suggest possible ways that they could do it. But the players are trying to guess what abilities the AP assumes they have rather than using the ones they do have, which is causing it to be harder for them than it should be. (And some have said they were going to use the abilities that would make it easier but then the one that thinks the AP has only one solution convinced them it was pointless to try those things.)
Reverse -- I like the idea of sending them the important text. It helps after the problem but can show them for future actions how APs tend to be written. (Or, at least, the style of AP that I like and therefore run.) And makes it so that they're not reading an entire AP or even just a book of one. When they're talking as if the AP only has one solution I try to correct them and it seems okay for a couple of weeks but then when another problem comes up they sometimes slip back into thinking there's only one way to solve it.
Christopk-K -- Yeah, some APs are bad for that. I've either managed to change them so the players have the proper motivation or I've been lucky enough to run APs that the players are invested in enough to be motivated to stay within the general story.
Fun twists like that are great fun! Quite often my players catch me off-guard so I need to figure out how NPC/enemies will react. The players always have fun with that and when they do that they figure the AP doesn't account for it but that I'll be able to make it work easily enough based on the information provided in the book.
"Full freedom" in any game doesn't work all that well as the GM typically has some sort of story in mind. But with Kingmaker (as it's one I've run before) so long as the players are invested in growing and protecting a kingdom there's not a lot that they can't do. But the players assume they can't turn an army against their king or that they can't form a treaty with the kingdom to the west so they don't even try because they assume the AP doesn't account for it. (Sure, the AP doesn't assume they do that, but a GM should be able to roll with it.)