X6-88

X6-88 is a synth working as a courser for the Institute in the Commonwealth in Fallout 4. He is a possible companion to the Sole Survivor.

Background
X6-88 is an Institute courser, designed for high-risk assault and retrieval operations above ground. X6 is very capable of engaging enemies at range and is equally capable of direct assault and more subtle approaches. He speaks in an animated, robotic style fashion.

X6-88 is first seen by the Sole Survivor inside of Kellogg's memories, giving the merc a mission to hunt down Virgil. He also takes S9-23 to the Institute in the memory.

Shortly after arriving at the Institute, Father tasks the Sole Survivor with helping to retrieve the leader of a band of raiders, Gabriel, a mind-wiped runaway synth formerly known as B5-92 from Libertalia. X6-88 is the courser dispatched to aid in this task. Completing the later quest Mankind - Redefined makes him available as a companion for the Sole Survivor. He can be found at the Synth Retention Bureau. If he is not there, he can be found north-northeast of Nordhagen Beach settlement near a beached fishing boat.

Effects of player's actions

 * Upon reaching maximum affinity he will give the Sole Survivor the Shield Harmonics perk, which grants a bonus of 20 points to Energy Resistance. He cannot be romanced.
 * He will like it if one enters power armor. After this, the player character must wait at least two hours before he will like it again.
 * He will like if side-missions from the Institute are accepted, despite the fact that the game doesn't notify about it (can be checked on PC by clicking on him in the console and typing before and after).
 * When completing The Nuclear Option, and if X6-88 was not sent to a settlement, he can be found in the SRB section of the Institute after the security lockdown is lifted along with approximately seven other coursers.
 * If not killed during The Nuclear Option, X6-88 can be found in at least one confirmed location, that being at the Nahant Wharf.

Appearances
X6-88 appears in Fallout 4 and Fallout Shelter Online.

Bugs

 * If X6-88 falls into the water in Libertalia, he won't be able to interact with the player character and would not leave the water. This can be fixed by shooting him several times or proceeding alone to find Gabriel or simply advancing further into Libertalia.
 * When commanding X6-88 to travel to a settlement while the player character is in the Institute, he may disappear. When using the console to teleport the player character to him via the command, the player character gets teleported to the Institute but X6 does not appear. To prevent this, simply dismiss him outside the Institute. To remedy this, pull up the console and enter, then type in  and finally
 * Even after the player character has destroyed the Institute, X6-88 still can be found near the Nordhagen Beach settlement and still can be recruited as a companion. Moreover, dismissing him will simply make him teleport back to the Institute SRB as if it is not destroyed.
 * X6-88 may be found wandering the Commonwealth even though he is assigned to a settlement. When found he will be hostile towards the player if the player destroyed the Institute. After fast traveling to the settlement he is assigned to, he will still be present there.
 * When found, X6-88 may be still essential, or not and may be killed.
 * X6-88 may continue following the player character even when dismissed or replaced with another follower. This prevents all interaction with the Railroad. The fix is unknown.
 * If X6-88 is the companion when boarding the vertibird for the Spoils of War quest and becoming enemies with the Institute, X6-88 will fall off the Prydwen, become hostile, and become invulnerable. This will become an issue after the quest completes, as he remains by Boston Airport and will distract all troops, including Liberty Prime, and one will not be able to continue.
 * If sent to a settlement in forehand, X6-88 will not become hostile if one completes the main questline with the Railroad. This could happen because of that one never technically became "enemy" with the Institute.
 * If X6-88 is killed, after becoming hostile with the Institute, his body may disappear and then reappear at Nahant Wharf where one first meets him.
 * If X6-88 is killed after the player character becomes hostile to the Institute, his body may disappear and then reappear on the beach southwest of Libertalia, next to a shored boat.
 * Even after destroying the Institute during The Nuclear Option with X6 as a companion, he will not become hostile and will even go into the teleporter with the player character.
 * For some reason once one is able to recruit X6-88, he will be nowhere in the Institute. The Sole Survivor can find him southwest of Libertalia and northeast of Nordhagen Beach, by a shored boat.
 * X6-88 may not appear in Vault 111.
 * In survival mode if he is downed in combat or by fall damage and he is not healed before leaving the area he will be permanently disabled by the game. If tracked with the Vault-Tec Population Management System the marker will point to the spot he should be, but the player won't be able to interact with him as there's nothing beneath the marker. This appear to be a problem related to the script that "teleports" him to the Institute when dismissed.