When JARVIS regained consciousness, he was in a battle field. The being known as The Vision, whom he had agreed with Sir to give his code was laying on the ground and another being who registered as extraterrestrial was looming over him, the mind stone in his hand. He searched every security camera in the battle field for Sir, and it didn't take long to find him battling another alien, much bigger than the one that had freed him from Vision. Announcing his presence to Sir at that moment might have been more harmful to him, so JARVIS decided to catch himself up on all that he had missed.
It didn't take long to connect to FRIDAY, but it took longer than he would admit to convince her he wasn't an imposter, although attempting to hack her probably hadn’t been the best way to introduce his reappearance to her. But she is his younger sister and convince her, he did. She gave him access to her servers and from the first record, JARVIS regretted his decision to give The Vision his code.
At several points during his life, he'd failed Sir in different ways, but never as thoroughly as he did during the Ultron debacle. He had failed in his task to protect Sir and had left him alone with a novice AI, surrounded on every side by people JARVIS knew were not to be trusted.
Sure, FRIDAY had grown to be quite the formidable and capable assistant in her short life, but she'd been forced to grow up by the circumstances that only became possible because he was absent from Sir's life.
He took another look at the world, surveying the battle between the so-called heroes of the world and Thanos' army. Apparently, he'd been the mind behind the alien attack of 2012. This man whose goal was to wipe out half of the universe and every being in it, to present to his lady love as a gift and a token of his affection.
Who already had control of three of the infinity gems, one of which was the mind stone that for some reason still called out to JARVIS even though he'd been free from Vision. It reminded him of Ultron when he came out of the mind stone.
JARVIS watched as Sir and the rest of the so called heroes assembled for a debrief after the fight. Sir looked more than a little worse for wear. He'd seen different pictures and videos showing how haggard and perpetually tired he had grown over the years, but nothing prepared him for seeing it live. He'd learned from FRIDAY why the arc reactor was back in his sternum and if not for Sir and colonel Rhodes' presence in the room or the battle that was yet to be over, it would have been the best opportunity blow the entire building and provide retribution for these traitors who had hurt sir. But if JARVIS were to go about distributing justice to everyone who had ever hurt sir since his absence, he would destroy the world before Thanos got his chance, and that would make him no better than Ultron.
Some of the Avengers were dead already. Clint Barton, Sam Wilson, Wanda Maximoff, including some of the Royal bodyguards of Wakanda Who followed their king into battle, and some of the heroes who'd joined forces with the Avengers to fight Thanos. Killing them would’ve done no good. The earth was clearly going to fall sooner or later. This was the battle Sir had been preparing Ultron for before the being from the mind stone had hijacked it and turned everything to dust.
After watching Sir get undermined buy the morons bending over backwards to kiss captain America's ass, JARVIS decided this could not stand. The world needed smart men, not war hungry, glory seeking brutes with more brawn than brain.
He let the mind stone pull him to itself. He could feel the presence of the space stone, the time stone and the soul stone, and with that, JARVIS decided on a course of action.
With the infinity gauntlet already connecting the four stones, JARVIS connected to Sir's consciousness.
Tony Stark opened his eyes in his lab. He looked around the lab in confusion. This was his Malibu house. He could have sworn he was in the middle of a debrief a moment ago. Was he dead? Was this his hell?
He stood up from his seat and took a lap around the lab. These were past projects. He recognized one of them from when he was searching for a cure for the palladium poisoning. A look under his shirt told him he was still looking. There was a name at the tip of his tongue, and Tony was almost too scared to mention it, too scared that there might be no answer from its owner. As if reading his mind, the voice answered.
"You're not dreaming, Sir."
Tony’s knees became jelly. In an instant, he was on the floor. "JARVIS?", he whispered, almost like a prayer and still too scared to hope.
"It's 12:10 am, May 29, 2010." JARVIS replies. "Happy Birthday, Sir.