The Steam website has news of an update to its SDK, as usual the update will be applied when restarting Steam.

New hl2mp character model sample
Fixed some cases of having to run the base game before being able to debug your mod
Optimized bandwidth usage in mods based upon the hl2mp code base
Implemented a fix in the lag compensation code that was occasionally preventing players from respawning correctly
Fixed xwad running vtex incorrectly
Fixed xwad building into the wrong target directory