X3-51 is a synth courser working for the Institute in 2287.
Background[]
They were tasked to retrieve K8-23, a runaway synth. Instead, they found K8's remains near Saugus Ironworks and returned them to the Institute. The Synth Retention Bureau hypothesizes that K8 was shot to death by the Forged.[1]
Appearances[]
X3-51 is mentioned only in Fallout 4.