The Source 2 engine is the stuff of legend. Whispered among Counter-Strike, Day of Defeat, and Dota 2 players alike. We expected a booming announcement from Valve when it announced its latest and greatest, but instead the Dota 2 community has logged into the game today to find their much-beloved MOBA has apparently crept over to the oft-rumoured Source 2 engine.

Hammer, the Dota 2 map editor, underwent a major update overnight, and in the process converted to what looks to be the first release of the Source 2 engine. The long-awaited game engine is expected to be the basis from of Valve's future games, including Left 4 Dead 3 and Half-Life 3.

Evidence of Source 2 was spotted following a Dota 2 update.

The new Dota 2 Workshop Tools’ alpha release will allow players to create, play, and share custom maps and game modes for Valve’s hugely successful F2P online battle arena. “Today, we are announcing the Alpha release of the Dota 2 Workshop Tools,” said Valve somewhat casually in the update blog. “This is a developer focused release and currently has high system requirements which means not everyone will be able to run the tools.

So far, so normal, until you delve a little deeper. Opening up the Dota 2 install file reveals that all relevant Source assets have been renamed. engine.dll has become engine2.dll, vphysics.dll, has become vphysics2.dll. As well as this the console has been redone, and the script allows different dlls to load and render different assets, something that wasn’t possible on the previous Source engine.

There’s not much to look at just yet for the average user yet; Dota 2 seems like an identical game and set of tools, but it does indicate more significant changes and announcements could be afoot. Do you think this is at last the official arrival of the Source 2 engine? Could this signal an imminent unveiling of new titles from Valve? Let us know what you think!