I was fighting a raider boss last night and had him below half health. He divked behind some cover and when he came out again he had almost full health.

Also last night I experienced my first settlement attack at the drive-in theater. In VATS I saw where one of my settlers was close to death, and yet despite being the target of multiple enemies survived the battle and had fill health at it's conclusion.

These two events make me wonder if NPCs are programed to use aid items like stimpacks, drugs, and food that are in their inventory? Or maybe even pick up these items and use them? They obviously have the ability to loot weapons and use them and armor. Does that translate to aid items?

They'll pop Stimpaks, yeah, but I think that's it. As for Settlers, those guys are Protected, so they can only die by your own friendly fire.

They'll use stealth boys too if equipped. I gave all 14 of my settlers in The Sanctuary a stealth boy. Then a attack happened it was comical to watch, everyone was invisible.

Well that removes, to a very large extent, the need for me to protect them. In fact the safest thing for them is for me not to engage. I like the challenge and sense of urgency involved in knowing I have to defend my people. I would love to see this modded away. Even if they die they're quite easily replaced. It would give me reason to craft stimpacks and stock my settlers up with them.

What you saw on the Legendary Raider is a "mutation" feature of Legendary enemies. A notice that the enemy is mutating will pop up and there are several potential effects of this "mutation". One of them is an almost instantaneous regeneration of all health.

NPC and Companions will use Stimpaks if in their inventory (and are given the chance to use them).

They'll also use grenades if you give them some.

So do setllers just become incompacitated in battle if theur health deplinishes similar to companions?

Keep in mind, they're only Protected if you're there. So those "help defend" objectives, you've still got to show up. And I'm not sure they get up or you can Stimpak them if they go down, or if they only get up after combat ends like with companions. Either way, leaving the fight to them would just become a chore since it takes forever for them to actually do anything.

I can't wait for a mod to change that. Essential companions I can understand for the sake of the story. Essential settlers, even when conditioned by your being within proximity, makes no sense. Especially since you can loot their corpse and recruit more settlers to take their place.

NPC's will use JET, Pyscho, and quite a few other items if these are in their inventories.

Wow, aside from the fact that I want all the stealth boys for myself (I'm selfish like that), that is pretty cool. Do you have to tell them to equip them (like with weapons/armor) at the moment that they need to use it? Or will they use them on their own, when needed, as long as they have it in their inventory? Will companions use them too?

I gave some stuff to Piper for her to hold as I was over the limit. 5 minutes later we get in a fight with a Mirelurk Hunter. Just before it goes down I see the red grenade being throw icon flash up followed by me being engulfed in flames.

Bewildered I look at the corpse of the creature, "Did that thing... throw a Molotov at me?"

Then I look over to Piper... "What is that you're holding in your hand?....."

Yes, amongst the items I'd given Piper were a couple of Molotovs....