Valve’s sent word that the first bout of substantial DLC  for Portal 2 will hit Xbox Live, Steam, and PSN on October 4. Entitled ‘Peer Review,’ it’s free across all platforms. Yes, even XBL.

From the announcement:

In “Peer Review”, you and a friend will continue the story of loyal bots P-Body and Atlas as you puzzle your way through a mysterious new co-op test track and once again match wits with GLaDOS. The DLC also features a single player and co-op Challenge Mode, and leaderboards to compare Challenge Mode scores with friends and the Portal community.

Valve has also updated its Portal 2 site with the final volume in Songs to Test By, the game’s official soundtrack.

Follow this author on Twitter.