G-Sync does not work when HDR is enabled on windows

When HDR is enabled in Windows, G-Sync does not activate properly in Last Epoch. I’ve attempted numerous common troubleshooting steps, including:

  • Closing all background applications and running only the game
  • Disabling all overlays (NVIDIA, RTSS, etc.)
  • Ensuring G-Sync is enabled for both Full Screen and Windowed modes
  • Forcing V-Sync via the NVIDIA Control Panel

If the game is launched with HDR disabled, G-Sync functions correctly (although with some unusual behavior described below). Interestingly, even if I enable HDR after launching the game in SDR, G-Sync continues to work. However, I’ve found no way to get G-Sync to work when launching the game directly in HDR.

Another unique behavior in Last Epoch is that, unlike most other games, G-Sync remains active even when the game window loses focus. Typically, in other titles, losing focus causes the system to revert to a fixed refresh rate until the game is refocused, at which point G-Sync resumes.

I also tested the game with the Special K utility, which often resolves presentation issues like this. Unfortunately, it doesn’t appear to work with Last Epoch. While running in HDR, Special K reports the presentation mode as “Composed Flip”, which does not support G-Sync. In SDR mode, it reports “Hardware: Independent Flip”, which does support G-Sync and functions as expected.

It’s also worth noting that “Composed Flip” introduces additional latency, as documented in Special K’s information on SwapChains.

System specs:
Monitor/Resolution: Samsung Odyssey Neo G9 57" 7680x2160@240 + HDR + G-Sync
GPU: RTX 5090
Driver Version: 576.15
OS: Windows 11 Pro (26100.3775)