The changes include:
Steam
Source MODs will now automatically appear in the games list
Improved startup process for Steam
Fixed crash when creating a backup that would span multiple DVDs
Fixed a bug that would unnecessarily validate Steam caches after a cache corruption
Fixed Condition Zero: Deleted Scenes and Codename Gordon failing to backup correctly
Fixed a bug where the message "the game files will be deleted and re-acquired" would repeat
Fixed offline mode failing after not connecting to Steam for more than a month
Half-Life 2
Optimization to the Steam filesystem to reduce game launch and level transition time
Source SDK
Simplified debug-launch process for MOD developers. MOD developers no longer need to place a config file in their directory
Added a registry key for MOD developers to use to locate a user's Steam installation located at HKEY_CURRENT_USERSoftwareValveSteamSourceModInstallPath
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