- In an interview with EuroGamer on May 17th,
- In a press release on May 24th, Valve announces that that Episode One will ship on June 1st and is the "first in a trilogy of episodes that will conclude by Christmas of 2007".
- In an interview with EuroGamer on June 6th, Gabe Newell says that there are three episodes that are "worked out". He also refers to the episodic trilogy as "Half-Life 3".
- On August 29th, an anonymous user on 4Chan's /v/ board posts a zip which contains 2,546 small images that are all parts of a larger image, which turned out to be a Source 2 model of D0G. This model was later found in the Robot Repair demo, and can be downloaded here. The identity of this user has never been discovered.
- Dota 2 updates on October 9th, and it comes with "hl3.txt", a file which is used as a help document for a presumed Half-Life 3 (Source 2) FGD. The full file can be viewed here. A more condensed list of the entities can be found in the dropdown below.
hl3.txt Entity List