People online are going wild thinking that Valve may have accidentally revealed the existence of a new Half-Life game after a developer mentioned a project referred to as "HLX."
Speaking at the Game Sound Con event, Valve sound designer Mike Morasky was discussing how Valve's games utilize high dynamic range (HDR) audio systems. He specifically called out how upcoming Valve game Deadlock has its own version of HDR and so does a project called HLX.
Another Valve developer sitting next to Morasky says to him immediately after, "Nice work," seemingly in reference to how Morasky might have spoken out of turn here by mentioning HLX. You can also see the other Valve developer saying to Morasky, "Good job, you only said HLX once."
Morasky is a Valve veteran, having worked on the sound and music for games like Team Fortress 2, Left 4 Dead, Portal 2, Half-Life: Alyx, and Counter-Strike 2. Outside of games, he worked on visual effects for Peter Jackson's The Lord of the Rings movies and The Matrix trilogy. He was a member of the band Steel Pole Bath Tab.
A while back, a datamining effort found references to something called HLX, and some think it's a new Half-Life game, or possibly the fabled Half-Life 3. For what it's worth, it's become something of an annual tradition for people to get excited about the smallest possible evidence of a new Half-Life, only to be disappointed when nothing gets announced.
The Half-Life franchise has a dedicated fanbase and the franchise has major cache, so it wouldn't be surprising to see Valve return to the series again after 2020's VR game Half-Life: Alyx. That was GameSpot's Game of the Year that year.