Robobrains were created before the Great War by General Atomics International both for the U.S. military and for the civilian sector. Official government records list only chimpanzee brains as being used in the robots, but at least some human brains were taken from the bodies of executed criminals. Many of these criminals were insane, so the resulting robobrains also tended to be unstable, despite complete reprogramming via the CODE technology. Some of these human-robobrains hybrids would try to kill themselves, apparently resenting being made into cyborgs. Rarely, some used the robobrain technology as a means of life extension. They underwent the procedure willingly and were not mind wiped. Bert Riggs, a lead developer of the robobrain project, lived hundreds of years beyond the war this way.
A robobrain moves on a tracked chassis (using dual 40 hydro-processor motors), either on a fixed or flexible mount. This is attached to a sizable cylindrical torso with a reinforced glass dome on top, housing the central processing unit with the organic brain suspended inside. In addition, to use consoles, operate levers, or engage targets with weapons, they have two flexible manipulators, ending in three point claws, on the sides of their torsos.
Robobrains were going to be the next generation of robotic soldier in the war against China, but their production costs made it difficult to implement their introduction into the American military.
The robobrain's organic brain is suspended in pressurized bio med gel (which is the primary reason the brains can continue to function for several centuries). Any damage to the casing or the brain itself can disrupt the robot's brainwaves and damage its neural connection to the rest of the body, affecting the robot's performance. Feeding the organic brain information about its surroundings are special sensors (typically with software written in 2076 installed), called Sensors '76. Apart from providing a real-time high resolution feed of the robot's surroundings, they are also capable of switching to infrared mode, in case the main sensors, for one reason or another, become useless for operating in unlighted areas.
The manipulators in some robobrain models are designed to operate regular human weaponry (such as AK-112 assault rifles), while some others have integrated laser guns (wattage equivalent to AEP7 laser pistols), supported by integrated mesmetrons. In addition, all robobrains have a built-in voice synthesizer.
Unlike in previous Fallout games, the robobrain from Fallout 4 appears to have a built-in eye in front of the brain.
The basic variant is the weakest and most common robobrain, with one of the manipulators replaced with a Tesla coil that fires an electrical discharge that arcs between targets. All robobrains are capable of a "mesmetron" attack that looks similar to the blast from a Gamma Gun. This blast is blue in color, staggers the player character and makes them black out briefly upon contact with the blast. Mesmetron blasts increase in frequency the more difficult the robobrain encountered.
This version of robobrain is the second most powerful variant. Cybermechs come equipped with their standard claw for melee, but an abnormally powerful robot modification, the unstable Gatling laser. Besides this change in weaponry, some kind of robot armor, perhaps primal plates, have been added to reinforce the chassis of the robobrain. This version of robobrain has a 150 point boost in health over the integrated robobrain, and is fully capable of rotating its torso independently of its treads, leaving almost no way to flank it. It may also strafe the player character with its rotating torso and treads, leaving stationary combat ill-advised.
The most deadly version of robobrain built by the Mechanist. The Quantum Robobrain has been highly modified with hydraulic armor, making damaging limbs or destruction of the robot nigh impossible without heavy weaponry. Additionally, Quantum Robobrains are capable of tactics such as basic cover systems and high-speed strafing. They are more accurate with their Unstable Gatling Laser than their Cybermech counterparts, and the frequency of the mesmetron attacks leaves the player character almost completely blind. This foe is cunning, cruel, and leaves almost nowhere to hide from their unending assault.
There is a slight inconsistency regarding robobrains in the Far Harbor and Automatron add-ons; the ones found on the Island are considerably shorter than their "cousins" encountered in the Commonwealth. This is especially evident if the Survivor enters Vault 118 with a robobrain companion made from the robot workbench. However, a likely explanation is that the robobrains of Vault 118 are custom models built specifically for the vault dwellers, and would thus differ from the mass-produced models seen elsewhere.