"For Vanduul combat, a section of gameplay was completed where enemy perception is reduced when searching for the player. This led to discussions of how to implement low visibility and other sense reductions across the board. They then prototyped the initial implementation for this specific gameplay use, which will also be used as a springboard for fully developing the feature. Vanduul perception and investigation progressed too."
I don't even.
For combat with aliens nobody has seen outside a janky model view animation were it ineffectively poked with its sci-fi stick...
How to implement low visibility? Seriously? I mean, we joke about backers not having played a game since the 90s, but sometimes you wonder if the devs haven't developed a game since the 90s.

Tony Zurovec - MobyGames
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Oh... yeah.
What is a subsumption tool? Are they developing text editors now?
My guess is its a fancy way of assigning goals and motivations to NPCs. But probably with a high fidelity front end so it looks good when they show it to backers, whereas most devs would be happy with, indeed, a text editor.
So, if i may, i'll take an example from NWN2. Each NPC had a number of triggers you could assign to it. On heartbeat was one. On Conversation. On Combat. On Death. And so on. About 9 or so in total. Things that would trigger the NPC to do something based on certain events. The On heartbeat one was the one where you really could go crazy giving them a life.
An amateur might start out giving custom scripts to each NPC. Like a barman who only serves drinks and wanders around a bar doesn't need the same actions as an NPC guard right?
But once the number of NPCs start piling up and you have many different types of them each with their own idle convo lines, unique and shared conversations, walk locations, things of interest, actions they can take, etc. Then what you really want to do is bring it all together with master scripts and instead of attaching unique scripts to each NPC, which can be a mess to maintain and bug fix, instead, assign the NPCs roles and character types (you can still do unique when you need to, just give them a unique tag).
So, in NWN2 you could add tags to an NPC, so we might have tags like: JOB=Barman, Location=City, Character=grumpy, Voiceset=Oldman
Then each NPC for each trigger calls the same base script and then that looks at the tags as necessary to determine what the NPC should do in each situation.
You can then make them as simple or as complicated as you want them to.
A guard can have a patrol route. Say there is a Guard with an ID=CityGuard1 then you have the heartbeat script tell it to follow the waypoints with its name attached (or walk between specified destinations or randomly walk) and only if certain events trigger (combat happens nearby, someone steals something in their perception range, someone talks to them) do you initiate other activities, then when over, it goes back to the base routines.
The NWN2 toolset and scripting set were quite limited, but you could still make it do some fancy stuff with a bit of clever coding.
This is basically what CIG are doing, but probably in a much more complicated and unnecessary way and taking like 100x it would if done the same way other developers have been doing it for decades, with no benefit and probably, because its CIG, may even be worse than other implementations.