Source Engine 2

Source Engine 2 doesn't have hidden costs or royalties - but is Steam exclusive

Source 2 announced, will also be free

Left 4 Dead 3, Source 2 spotted in Valve offices - rumour

Source Engine 2 mentioned in former Valve staffer's CV - report

Source Engine 2 in the works at Valve - report

Source 2: it's time for Valve to drop the baby steps

Valve Source 2: Discovered files hint at developer's new game engine

Valve reiterates preference to updating Source Engine, instead of creating Source Engine 2

Valve doesn't have any current plans for Source Engine 2

Rumor: Valve's E3 surprise is Source Engine 2