Solipsil (Serial number: SLP 0391-5) is a UNSC AI during the Human-Covenant war. Little is known about this AI, other than it holds the position of a loan/contract AI in the Office of Naval Intelligence. On December 28, 2530, Solipsil recorded a log of the interrogation of Subject 386 In a conversation between Solipsil and "Smart" AI Cortana in 2550, they were comparing AIs to Spartans, though Solipsil argued that Spartans are in a better position than AIs.