Skyrim Script Extender developer extrwi posted a PSA on the Skyrim modding subreddit that warns of incoming changes that’ll affect all makers and users of mods moving forward. When the Anniversary Edition for Skyrim drops, mods will essentially break, and there will be a period of time when the community tries to catch up as it finds all of the relevant functions again.
Most available Special Edition mods make use of the Skyrim Script Extender to make scripting jobs easier. If that element breaks, the vast majority of mods break with it.
In extrwi’s words:
Plugins using the Address Library will need to be divided in to “pre-AE” and “post-AE” eras. Code signatures and hooks will need to be rewritten. We will all need to find functions again. The compiler’s inlining behaviour has changed enough that literally a hundred thousand functions have disappeared and been either inlined or deadstripped, to put it in perspective.
The modder received confirmation from Bethesda that these fears were true.
So after meticulously documenting where to point code over several years, the mod community will have to re-do that work with the newly compiled AE code. It looks like they’re up to the job, but it’ll have to be done plugin by plugin, over an unknown amount of time.
The mod community has been a huge part of what’s kept Skyrim going all this time, and when combined, mods can produce some truly beautiful results. Or they can just be ridiculous. Or unplayable. Whatever your cup o’ tea.
Will my Skyrim mods work anymore?
If you have the Special Edition of Skyrim installed, the Anniversary Edition will be treated as an update. That means if you do nothing and allow the game to auto-update, you may log back in to find a completely new game.
Some aspects will be better, i.e. all the AE additions, which include 74 mods built in and supported. But unsupported mods won’t work anymore, and it’s probably a safe bet you prefer the ones you installed yourself.
Why is this happening?
Skyrim AE will be compiled in a different way, using Visual Studio 2019 instead of Visual Studio 2015. It forces mod developers to “start from scratch finding functions and writing hooks,” says extrwi.
This could be because Windows Store achievements don’t go back before 2017, but so far that’s speculation.
How can I avoid updating Skyrim?
If you want to avoid Steam auto-updating to Anniversary Edition, you can right-click on Skyrim in Steam and hit Properties, then Updates. Select the option there for Only Update This Game When I Launch It.
From there, you can avoid launching via Steam and use your mod manager skse64_loader instead.
It’s also recommended that you back up your entire folder, just in case.