Chet Faliszek, who had been with Valve since 2004, has confirmed his departure from the studio after more than a decade of service.
The writer, who had a hand in Half-Life 2, Portal, Portal 2, Left 4 Dead and Left 4 Dead 2, is the third member to leave Gabe Newell's company, following Erik Wolpaw and Marc Laidlaw who have also recently moved on.
"[It was] Nothing exciting or drama filled," he told GamesIndustry. "I worked there 12 years, shipped a bunch of great games and some amazing hardware and wanted to change things up. There's no news on what's next etc, I will let you know when that happens."
Faliszek had most recently been involved with the growing virtual reality side of the business and had been working with external studios as Valve looked to get Steam VR off the ground.