Fallout 4 Companions

Permanent companions
The base game has 13 companions; four more are available with the Automatron, Far Harbor, and Nuka-World add-ons.

Temporary companions
The game has a number of temporary companions that will only be available during certain quests.

Interests
Companion affinity is gained and lost with two varying degrees for both. Here is how the table below represents those changes:
 * General behavior


 * Miscellaneous activities


 * Faction quests

Bugs

 * A companion may become stuck in a reference pose position, flying around unanimated about 1-2 feet off the ground following the player character. The companion can be spoken with and interacted with in a normal manner, however, the companion will not fight. Even loading a new area by going through a door will not fix this behavior.
 * One potential fix is to fast travel to another location.
 * Another fix is to dismiss the companion. The companion can be re-recruited back.
 * Certain sound effects can get "stuck" to companions and continue to play after said companion quit performing the respective action. Known examples include the sound of wielding a Ripper, firing a Gauss rifle and using the weapon bench's drill. When the bug occurs it follows the companion around, waxing and waning depending on their distance, and can neither be stopped by fast-traveling, reloading or taking the weapon away from them. It can, however, be fixed by closing and restarting the game. It is currently unknown what exactly causes the bug.
 * Should the Ripper sound be playing over and over, having the companion use the weapon again may fix the bug.
 * If a companion has the drilling-sound glitch from an armor workbench or weapon workbenches, allowing them to re-use the corresponding workbench from where the glitched sound is and let them end its use by themselves without interruptions, the sound glitch should stop and be fixed.
 * Ada may remain with you even though you have just selected dismiss in dialogue, as well as the option of the settlement won't pop up.
 * One solution is to restart the game.
 * Another solution is to acquire a different companion.
 * When sending a companion to another settlement using the workshop he/ she will not go there straight away, and bringing the settlement choices back up will show the place still has an option to where they can be sent.
 * A fix for this is to turn the game off, then reloading the save.
 * Another fix is to fast travel to a different place and sleep in a bed and return.
 * If a companion is down while changing zones, they may remain "downed" permanently, only changing areas along with the Sole Survivor. This can be fixed by damaging their HP until they go "down" and regenerate again while out of combat.