Following the release of Aperture Desk Job - Valve's free playable "short" set in the set in the Portal universe - a spot of eager datamining has uncovered references to four unannounced Valve games, including a Half-Life: Alyx follow-up, a Source 2 port of Counter-Strike: Global Offensive, a recreation of a cancelled Portal title, and Citadel, a Half-Life shooter/RTS hybrid.
All this was uncovered by long-time Valve watcher Tyler McVicker, with at least some of the new discoveries pointing to titles long rumoured to be in development at Valve, but never actually confirmed. The caveat, of course, is that their mere existence as references in Aperture Desk Job's code doesn't mean these are actual games still in development (particularly given Valve's well-reported experiment-then-ditch approach to game design), or that they'll ever see that light of day. As McVicker says in a video documenting his discoveries, "take everything that we're about to discuss with a grain of salt".
While all four games are potentially exciting in their own right, there's very little to relay beyond a couple of references in Aperture Desk Job's code as far as the Half-Life: Alyx follow-up, the recreation of a previously cancelled Portal game (possibly F-Stop, a camera-based puzzler which was canned in favour of 2011's Portal 2), and the Counter Strike port go.
Citadel, though, is a different story; it's been popping up in Valve rumours since at least 2019, and McVicker had an update last November, calling the project a mash-up of Alien Swarm, Left 4 Dead, and an RTS, all set in the Half-Life universe and being developed for Steam Deck.
Now, in his latest report, McVicker says "somehow a significant amount of Citadel code comments are just sitting in" Aperture Desk Job, noting there are "way too many to read through in this video". Based on his latest findings though, McVicker now calls the project a "Combines versus rebels, team-based, squad-based, class-based, RTS-FPS hybrid" featuring a single-player campaign and two major gameplay systems.
Those core systems, according to McVicker, revolve around abilities and bots. Abilities include weapons, weapon upgrades, grenades, team buffs, and so on, some of which can be attached directly to the body - and, crucially, directly to bots. Players are said to take control of a commander that can view the map from the top-down and then deploy bots as team mates. These bots come in "many different classes" and can be squadded into groups and given abilities, with players able to control bots individually or in those groups.
There's a load more detail on how these key systems might function in practice as part of McVicker's video, should you be keen to learn more, but the overall suggestion is Citadel appears to be in pretty advanced stages of development. Not that that's any guarantee the project will ever see the light of day, of course, but with Valve's Gabe Newell previously confirming the company would be announcing more new games post-Alyx - titles still yet to be revealed over two years later - we can only hope it'll have something to announce soon.