An update to Counter-Strike: Source has been released. The update will be applied automatically when you restart Counter-Strike: Source. The major changes include:

• Added 64-bit Support. 64-bit binaries will automatically be launched on systems with a 64-bit OS.
• Added a borderless window option to video settings
• Added bicubic lightmaps (from Half-Life 2: 20th Anniversary Update)
• Added radial fog (from Half-Life 2: 20th Anniversary Update)
• Added support for Steam Networking
• Added UI scaling for high-resolution screens
• Made the default server name for listen servers include the player's name
• Made the game launch in native resolution by default instead of 640x480
• Client-side prediction fixes (these fix 'jank'/rollback in certain situations)
  • Fixed a bug where when unducking, the view could glitch out if the player doesn't have space to unduck
  • Fixed gifts not randomly dropping when players are killed during the winter event
  • Added sv_autobunnyhopping so bhop servers can have this wanted behaviour with client-side prediction
  • Fixed a prediction bug where if the player was moved on the client, their input-based movement for that tick was not taken into account in non-player actions
  • Improved prediction for walking on props and other entities
  • Made certain client-side entities only trigger local prediction errors
    • e.g. If the viewmodel experiences a prediction error, the player will not experience a prediction error
  • Fixed prediction of viewmodel sway
  • Fixed a prediction error regarding weapon idle animations
• Fixed certain breakable props not gibbing correctly
• Fixed an issue where certain variables like position would not be updated correctly to match the server in certain situations
• Fixed the player's base velocity (eg. conveyors, moving items etc.) getting subtly out of sync from client/server