Vive Legacy, VR Compositor not launching with 4.12.5?

A SteamVR project stopped working since updating to 4.12.5 version. The project runs without error, but the VR Compositor window never opens and the headset just sees the vive gray room. This was already running fine in 4.12 before updating to the recent hotfix.

I updated video drivers (GTX 970 to latest nvidia), but no change.

I verified that an older version of the engine still runs an older version of the project (4.11.2), and that VR games in my Steam library still work. So, it doesn’t appear to be a problem with the Vive hardware setup or SteamVR.

I did 2 additional tests:

  1. downloaded a template project, it also failed to launch the vr compositor
  2. created a blank project (in 4.12.5 and 4.11.2) following UE4 vr quickstart doc, 11.2 worked and 12.5 failed

I wanted to check if this is a known issue, or if anyone else has encountered this?

Well, I’ll assume Legacy support was quietly removed in 4.12.5 then. The project launches/previews fine using the Pre.

Same problem here. Did you manage to make it work in the end?