A former Valve programmer worked on a 'Source 2' engine for over two years before departing the company, his CV has suggested.
The developer's LinkedIn profile - screen-capped by NeoGAF - claims that work on the unannounced technology has been ongoing since at least November 2010 - right after the release of Half-Life 2: Episode 2.
Valve boss Gabe Newell confirmed the Half-Life studio was working on the new game tech late last year, telling fans during a studio visit: "We've been working on new engine stuff for a while, we've just been waiting for a game to roll it out with."
Asked if that meant an "entirely new engine" rather than a simple extension, the Valve boss replied: "yeah."
Early last year more than 60 references to a "next-gen" engine were discovered in script files behind recently-released Source Filmmaker.
The Counter-Strike developer has previously bragged its engine is "considered the most flexible, comprehensive, and powerful game development environment out there. And it's about to get even better."