As a Beastmaster Ranger, I can't cast 'Animal Companion' or 'Find Familar' without it causing combat to initiate.
The only way to exit combat is for my party to kill the summoned creature (whether a companion or a familiar).
It wasn't like this for the first bit of the game. After making it to the outside of the crypt in the starting forest, and fighting the team there, I summoned my familiar and that initiated combat with the guy hiding on the other side of the door. It seemed that from there, summoning a creature would initiate combat.
I then decided to go Beastmaster and found that summoning an Animal Companion similarly initiated combat.
Thanks