Fans have spotted that the recently released test build of Counter-Strike 2 (CS2) contains files referencing a "Left4Dead3," (L4D3) although, it appears that it could simply be leftover code from early in Source 2’s development.

The details:

Reddit user u/PaP3s shared an image of code discovered in the files of CS2 referencing a long-awaited third installment in the co-op zombie shooter franchise. The code itself does not reveal anything significant, though one line reads "priority = none," which piqued the fans' interest given that the second entry in the series has been out for over 13 years. A similar situation occurred in the past when code referencing L4D3 and CS:GO was discovered in the Half-Life Alyx Workshop code.
Some fans believe the code is just another joke from Valve, as the company is known to troll players with references to anticipated games and updates. Even the announcement of CS2 was riddled with attempts to mislead fans and prolong their wait. This is entirely unconfirmed, but don't be surprised if it proves true.
According to the interactive documentary The Final Hours of Half-Life: Alyx, the original version of L4D3 was being worked on by a team of 30 developers in 2013, and was to be featuring an open-world setting in the country of Morocco. The development process stopped as the team planned to have hundreds of zombies populating the world similarly to the structured levels in the other two entries, which the then-new Source 2 engine could not handle. It’s becoming increasingly unlikely that fans will get to play a new game in the franchise soon as Valve appears to be diverting all of its attention to CS2, and it doesn’t help that the company seems to be scared of the number 3 as we wait for Portal 3, and the widely joked about Half-Life 3.

Other Valve news:

The limited test for CS2 was leaked online only two days after its release to a select group of players. The leaked copy cannot be played online, although some players are worried that cheat creators may be able to develop cheats for the full release using the existing code.
Steam Deck designer Pierre-Loup Griffais has stated that Valve is interested in an OLED model of the handheld but has yet to create one due to the amount of work necessary to implement the higher-quality screen. Griffais stated that everything is built around the screen and that both the internals and software would likely need to be altered to change the existing LCD panel.

References to Left 4 Dead 3 found in Counter-Strike 2’s files