Ada is a heavily modified assaultron robot, with sentry bot and protectron parts, and was created by Jackson. She traveled with his caravan, which specialized in mechanical repairs and trade, throughout the Commonwealth. Jackson's caravan attracted the attention of the Mechanist, and after three attacks, every member of the caravan except Ada had perished. Ada is first encountered during the quest Mechanical Menace during which the Sole Survivor must help Ada eliminate the robots that attacked her caravan.
If dismissed, and no location is specified, she will relocate to the Red Rocket truck stop, but will not count towards that settlement's population. If a location is specified, including Red Rocket truck stop, she will count towards the population of that settlement.
When she is the companion, upon talking to her she can give several random junk items, a trait she shares with all player-built automatrons that have their personality subroutines activated.
She is one of three companions that can be ordered to steal owned items.
She is the only companion aside from Dogmeat that doesn't care about the Sole Survivor's actions at all. She will offer advice and her opinion depending on the situation like any other companion but will never gain or lose affinity. As a result, there are no affinity perks to be gained from Ada.
Being a modifiable robot, Ada can be upgraded with lockpicking or hacking capabilities to cover for the Sole Survivor's potential shortcomings in any of those fields, should Cait or Nick Valentine be unavailable for some reason.
If taken to Vault 111 to see the Sole Survivor's spouse, she will not make any comments.
Codsworth's tone of voice, when first meeting Ada, could be interpreted as flirtatious.
Ada uses the same body animation (hands and legs) when equipped with a head laser or mesmetron (robobrain head).
Ada will lament on not having a vacuum attachment when entering certain cluttered or dirty rooms.
While still a companion character, no remarks will be made about Ada in her presence as there would be for other base companions.
If the player character takes off all clothes while with her, she may remark "people look so strange without their clothes on" or "running around without clothes on doesn't seem like the smartest thing to do in an environment like this."
The following is based on unverified behind the scenes information and has not been confirmed by canon sources.
Ada is likely named after Ada Lovelace, a real-world mathematician and an early innovator in the field of computer science. She shares her namesake with Lady Lovelace, another assaultron present at the Easy City Downs.
Some of Ada's dialogue lines are references to pop culture and science fiction. For example, "resistance is futile," is a reference to the Borg in Star Trek. Another one is found during Restoring Order, when she mentions "It feels like: Poetry in motion." Referring to the popular song by Johnny Tillotson in 1960.
End of information based on unverified behind the scenes information.