Companion

Companions are characters who may be recruited to follow and aid the player characters during their adventures. Certain companions will have requirements that must be met in order to join the player.

Controls
Companions cannot be controlled directly. Instead, one can change some settings for their AI. In Fallout, the controls are rudimentary at best while Fallout 2 is a substantial improvement.

Level up
Companions don't level up by gaining experience as the protagonist does.

In Fallout, companions do not level up at all.

In Fallout 2, each companion has a fixed number (typically, 4-6) of predefined levels called "stages" in the form of multiple alternative models for them with different statistics. Each time the player character gains a level, every current companion has a chance to go up a stage i.e. change to a more powerful model. A companion starts with a base model, then advances to stage 1, 2 etc.

Using fixed models also means that a companion cannot permanently gain stats in any other way, e.g. by reading skill books.

Due to a design bug, companions who are supposed to have six stages cannot ever reach Stage 6, as their progression is divided not into six, but seven stages. For example, Goris is supposed to have six stages (protos 319 through 324), but the character the player interacts with and recruits is none of these protos, but a separate, "base" Goris (proto 153).

This would not normally be an issue, but each record in the file is capped at 200 bytes of length, which only accommodates five records. Anything exceeding that length is truncated and ignored by the engine. As such, each six-stage companion can only level up to Stage 5, as the data generated from party.txt at startup will never include the sixth stage, due to a hardcoded limit.

This was not a well-known bug, even to developers: In Fallout Bible 4 Chris Avellone only showed the stats for stage prototypes and missed the base prototype for Goris.

Usable weapons
The kinds of weapons a companion can use is not determined by the weapon's type but rather by the in-game model the weapon utilizes when used. A companion can use weapons that their character model has animation sprites for. The types of weapon models are:

It is due to this mechanic that a companion's model does not change from wearing different types of armor; changing the model would change their qualifications as well. The added benefit here is making it easier to distinguish the companion from regular NPCs wearing the same type of armor.

Active skills
In Fallout 2, if a companion has a higher active tag skill than the Chosen One, whenever they use that skill on something, the companion lends them a hand by running in and using the corresponding skill on the object themselves. This way, a skill check will be done against their skill level, which allows the Chosen One to do things they would otherwise be not qualified to.

This doesn't, however, extend to other interactions like skill checks in normal dialogue and during regular object use (e.g. it's not possible to use a strong companion to open jammed doors in Vault 8), or when using items that act the same as an active skill (e.g. a doctor's bag). This severely limits companions' usefulness as specialists, as they can't really save the protagonist from having to train all the needed skills and stats themselves.

Fallout Tactics
In Fallout Tactics: Brotherhood of Steel, companions are referred to as recruits. These characters may only join the party if the player can afford the recruitment cost.

Fallout 76
Fallout 76 does not offer companions in the traditional sense, but it does feature similar mechanics. Players are encouraged to form Public Teams and band together against the threats facing Appalachia and beyond. Several perk cards are designed with multiplayer in mind and provide effects similar to the companion perks in previous games.

Certain characters may serve as temporary quest companions that aid the player during select quests. These temporary companions will not revive players that are down in combat but may be revived themselves should they run out of health. If they are not revived, they will heal themselves and return to the action after a brief moment.

CAMP allies
Fallout 76 does, however, include characters that may be recruited to hang around at player C.A.M.P.s. These Allies will not follow the player around, but they can offer variety of services ranging from temporary bonuses to entire questlines. Allies will only appear once their associated workshop object has been placed. Although only one Ally may be active at a time, there are workshop objects that will spawn a friendly character.


 * Collectron stations will generate items over time and spawn a Collectron robot to defend the C.A.M.P. from hostiles. Their harvesting routine may be changed at the attached Collectron station terminal. Only one Collectron may be placed at any given time but new harvest options may become available by unlocking additional Collectrons.
 * The Brahmin pen will generate raw fertilizer over time and spawn a Brahmin that will ignore combat.
 * Workshop turrets, mannequins, and even the chassis display frames are all technically non-player characters.
 * A friendly Vertibot may be called upon to help anywhere in Appalachia by throwing a Vertibot signal grenade. This will not work if the player does not currently control a workshop with an functional Vertibot.

Creature taming
In addition to the above, players with the Animal Friend perk may discover docile, tameable creatures during certain random encounters. By walking up to the creature or aiming, a button prompt will appear that offers the option to tame the creature. Accepting it will cause the creature to walk directly to the currently activated C.A.M.P. where they will serve as a guard dog. Be wary, however, because tamed creatures may be killed in combat.