Yet, with the performance of most games varying wildly across the broad spectrum of commercially-available virtual reality machines, will Valve be able to

Which VR headsets is Half-Life: Alyx available for?

All the PC Headsets.

Ok, more specifically:

  • Valve Index (obviously)
  • HTC Vive (and presumably Vive Pro)
  • Oculus Rift
  • Windows Mixed Reality.

I would also guess any SteamVR headset would also work, for example the Pimax.

Source:

Save 10% on Half-Life: Alyx on Steam

Valve’s return to the award-winning series in virtual reality takes place between the events of Half-Life and Half-Life 2. Alyx Vance and her father Eli mount an early resistance to the Combine’s brutal occupation of Earth.

As Alyx, players battle to save the future of humanity: engaging in visceral combat, solving puzzles, and exploring a world decimated by a mysterious alien race. VR was built for the kind of gameplay that sits at the heart of Half-Life.

As near as I can tell, it won’t be available for Oculus Quest, but you could always use the Quest Link to use PC VR on the Quest, basically using it only as a display device.

Also important to note: it won’t be a pancake game (flat). Good for Valve!