Related issue with similar symptoms but different error in the same game: #2963
(vk_samples_from_dxgi_sample_desc: Unhandled sample count 0 → GPU page fault).
Both bugs affect Clair Obscur: Expedition 33 under vkd3d-proton and may share
a common root cause in UE5 D3D12 command list handling.
is there a reliable way to reproduce this quickly? This isn't really all that actionable if it's random and can take over half an hour.
is there a reliable way to reproduce this quickly? This isn't really all that actionable if it's random and can take over half an hour.
Regarding reproduction: the crash occurred consistently either immediately
after the boss fight with The Bishop (early story boss) or within 3–5 minutes
following the victory screen. It seems to trigger during the post-battle
transition or asset streaming phase.
This aligns with the error itself — CopyCommandList->Reset failing during
what appears to be a heavy asset streaming event (large area transition after
the encounter).
If it helps: VKD3D_CONFIG=single_queue made crashes occur faster in general
(~5 min vs ~30 min), suggesting the issue is sensitive to command queue
configuration.
I can try to reproduce it specifically at that boss fight and report back
if the timing is consistent enough to be useful.
Important update: the game crashes on Windows 11 as well, with exception
code 0xc000001d (ILLEGAL_INSTRUCTION) at offset 0x2a03d05 in
SandFall-Win64-Shipping.exe.
This suggests the root cause may be in the game itself — UE5 likely uses
__ud2 as a crash mechanism when detecting an internal error condition.
vkd3d-proton may be triggering this error path rather than being the
primary cause.
Further update: confirmed BSOD (0x000000d1) on Windows 11 with AMD
Adrenalin driver 26.3.1 (latest official) while playing the same game.
AMD Bug Reporting Tool confirmed LaunchReason: BSOD.
This strongly suggests a GFX1200 driver-level bug affecting both
Windows and Linux, not specific to vkd3d-proton.
@Tigusigalpa272 Could you provide your most recent save files at the exact crash point? please package the entire users directory (which includes both saves and config files) into a tarball using the following command:
tar -zcvf expedition33.tar.gz ~/.steam/debian-installation/steamapps/compatdata/1903340/pfx/drive_c/users/steamuser/AppData/Local/Sandfall/Saved
Also, could you provide detailed instructions on how to reproduce the bug from that save point, such as which specific battle to enter or what specific actions trigger the issue? Thanks.
VKD3D_CONFIG=single_queue`x2 2026-05PROTON_LOG=1`:x1 2026-04VKD3D_CONFIG=no_fallback_barrier`x1 2026-04VKD3D_CONFIG=no_upload_hvv`x1 2026-040xc000001dx1 2026-05
System Information
Problem Description
The game crashes after 5–40 minutes of gameplay with a UE5 LowLevelFatalError.
The assertion
!status && "vkBeginCommandBuffer"inwinevulkan/loader_thunks.cappears as a UI dialog just before the crash.
Root Cause (from Proton log)
Found in
steam-1903340.logviaPROTON_LOG=1:LowLevelFatalError [File: D3D12Util.cpp, Line: 1077]
Interfaces.CopyCommandList->Reset(*NewCommandAllocator, nullptr) failed
at D3D12CommandList.cpp:264
with error E_INVALIDARG
UE5 D3D12RHI attempts to reset a Copy Command List allocator that
vkd3d-proton considers invalid at that point.
Tested Workarounds (none worked)
VKD3D_CONFIG=no_fallback_barrier— no effectVKD3D_CONFIG=no_upload_hvv— no effectVKD3D_CONFIG=single_queue— crashes faster (~5 min vs ~30 min)r.D3D12.AsyncCopyEnabled=0in Engine.ini — no effectAdditional Notes
(GPU left in unstable state, compositor loses context)
-dx11mode as a workaround (Frame Generation unavailable)steam-1903340.log