This article is about the final stage of A.I. Rampancy. You may be looking for Agent Maine.

Metastability is the fourth and final stage of A.I. Rampancy.
According to theory, A.I. having reached Metastability can actually be considered a human being. It was first thought impossible for an A.I. Fragment to reach Metastability, however Sigma has reached this phase (Sigma by taking Maine's body). The reaching of this phase is extremely rare, but not impossible after Sigma made it so.
Epsilon however, even though developing a legit personality, gaining sentience, and expressing more than one emotion/attribute, is NOT metastable, as stated by Burnie Burns.
Order of the Just[]

Metastability(found on the back of Maine/The Meta's neck)
Princess Luna made it a strict regulation that no future A.I. programs are allowed to get even close to Metastability after the situation with The Meta. If A.I.s are about to approach Metastability, repairs must be preformed.
However, if the conditions are correct for an A.I. to approach the Meta stage WITHOUT going ammok, they can be allowed to do so.