Leaked Valve files reveal cancelled Half-Life 3 built on unfinished Source 2 engine

A leaked 12TB archive of Valve development files dated 2003–2013 reveals that Half-Life 3 was in development around 2013–2014 as a procedurally generated, replayable game fusing Left 4 Dead-style gameplay with scripted story moments. The project was cancelled because it was built on the unfinished Source 2 engine. Valve has not commented. Eurogamer reported the leak on 30 August 2026.