More than 12TB of internal Valve files have reportedly leaked online, apparently covering everything published on Steam between 2003 and 2013, including beta builds and finished games from Valve itself and third-party developers. The leak is significant because it exposes years of unreleased prototypes and internal development material from one of gaming's most secretive studios, including hints at the long-rumoured, never-released Half-Life 2: Episode 3. Valve has not yet commented on the leak, so details are still being verified by the community.

Internet users have been combing through a GitHub catalogue compiling the leaked titles, which reportedly include material from Valve franchises such as Half-Life, Left 4 Dead and Portal, as well as third-party games from series like Call of Duty, Fallout and Civilization. Notable findings so far include early builds of an unreleased Valve game called F-Stop, centred on a camera that manipulates real-world objects, along with references to the cancelled Half-Life 2: Episode 3. According to a social media user credited with surfacing the leak, it stems from a publicly accessible endpoint, and the files stop at 2013 because that is when Valve moved to a different storage system.