Orphaned Source SDK Content
(October 11, 2017)
With the public release of the Source engine in 2004, Valve originally released the Source SDK with each game's authoring tools bundled into one download. Valve has since moved away from this with the release of authoring tools included with each game, in the
While source code for the newest builds of the engine can be found on Valve's GitHub, historical code, model samples, modeling package plugins to add SMD support, and sample map sources for Half-Life 2, Team Fortress 2, Portal, Counter-Strike: Source, and other Source games have now been orphaned—packaged only with a nonfunctional build of the modding tools needed to use them. As a result, new modders tend not to see them.
These files have been sorted, archived, and are available for download here.