Starfield has only been out in the wild a few days, but now it has the one mod to rule them all: the Starfield Script Extender (SFSE). The mod is the creation of Ian Patterson and Stephen Abel, who clearly spent this past weekend tinkering away while everyone else was exploring space, and this will be the foundation for most if not all of the more ambitious mods Starfield will receive.
The SFSE is a tool that adds additional scripting capabilities and functionality to the game, which basically means it gives modders a whole lot more to play with. If you've any intention of playing Starfield modded then this is almost the starting gun for the real work to begin (though the modders are already working fast, and here are the best Starfield mods so far). Scripts offer functionality that isn't normally available through the in-game tools, and goes beyond Bethesda's own scripting to allow for more complexity.
The importance of a Script Extender to the modding scene can be seen best in Skyrim with SkyUI. It's the all-time most popular mod for the original game and the third most popular for Special Edition, and is necessary for a whole bunch of other mods to work because of its configuration menu. It itself wouldn't be possible without the Skyrim Script Extender (SKSE). In fact, the release of the special edition saw mild panic as a bunch of mods instantly become incompatible because SKSE didn't work on the special edition, necessitating a new version called SKSE64. Incidentally Ian Patterson, the creator of SFSE, was also a collaborator on SKSE.
SFSE supports Starfield on Steam, but does not work with the Epic Games Store version or even more notably the Windows Store and Game Pass versions. "The game runtime needs to be launched suspended for this to work, and the game-specific MS Store apps (at least Fallout 4 and Skyrim SE; I don't subscribe to gamepass and don't own the game on the MS store) all prevent you from using the existing debug APIs for launching suspended," said Patterson in response to someone asking why. "I have done significant research on this and short of a ghastly hack this can't work."
There's something quite alluring about the phrase "ghastly hack" but I'll take his word for it. To briefly pause on that for a moment, it is remarkable that thanks to Microsoft's store policies and distribution methods for its own titles, the definitive version of Starfield is always going to be the one on Steam. I would argue the reputation of Bethesda games has a lot to do with what modders achieve in them post-release, and certainly it's what has helped Skyrim and others achieve such extraordinary longevity. The mods are a major strength, but you'll only be able to get the best ones by buying the game from a third party rather than direct from Microsoft. Seems odd is all.
There are already some early mods making use of the SFSE, including an Enemy Friendly Fire mod and a Native HDR one. There are also mods to make using the SFSE simpler, like the self-explanatory Launch With Steam and this enables achievements while using it. But just you wait: sit back, and get ready for the galactic fireworks.