Alert Carry is a Fallout 4 mod that adds a bit of realism to the game.
With it enabled, your character will no longer hold his or her weapon up when he or she isn't aiming or firing it at any enemy. Instead, it will be held in a non-aggressive manner.
The mod works with all non-melee weapons in the game including the new weapons from Automatron and Far Harbor.
It's pretty basic but it's one of our favorite Fallout 4 mods at the moment.