Compatibility Report

• Name of the game with compatibility issues: Final Fantasy VII (Modded with FF7_SYW)
• Steam AppID of the game: N/A (mod launcher is external)

System Information

• GPU: AMD RX 5700 XT
• Video driver version: Mesa 25.1.7
• Kernel version: 6.15.9
• Proton version: Proton 10.0 (also tested with 9, 8 and Experimental)

I confirm:

• [x] that I haven't found an existing compatibility report for this game.
• [x] that I have checked whether there are updates for my system available.

Symptoms

.NET 9.0 application (FF7_SYW_Unified.exe) fails to launch using any official Proton version. The following error appears in the log:

Failed to create CoreCLR, HRESULT: 0x80070005
...
Message: Failed to load System.Private.CoreLib.dll (error code 0x80070005)
Path: Z:\opt\games\FF7SYW\FF7_SYW_Unified\System.Private.CoreLib.dll

The launcher used to work fine when targeting .NET Framework 4.5, but now that the developer migrated to .NET 9.0, it fails with this error. The same setup works without issues under Wine (tested with Wine 10.12 and winetricks install: dotnet40 dotnet48 dotnet9).

Reproduction

1. Download and extract FF7_SYW_Unified mod launcher to /opt/games/FF7SYW/FF7_SYW_Unified/FF7_SYW_Unified.exe
2. Create Proton prefix directory:

mkdir -p /opt/games/FF7SYW/FF7PRO

1. Attempt to launch the mod launcher using Proton:

SteamGameId=ff7s PROTON_LOG=1 PROTON_LOG_DIR="$HOME/logs_ff7p" PROTON_ENABLE_WAYLAND=0 \
STEAM_COMPAT_DATA_PATH=/opt/games/FF7SYW/FF7PRO/ \
STEAM_COMPAT_CLIENT_INSTALL_PATH=/home/joan/.local/share/Steam \
/home/joan/.steam/steam/steamapps/common/Proton\ 10.0/proton run /opt/games/FF7SYW/FF7_SYW_Unified/FF7_SYW_Unified.exe

Result: crash with CoreCLR error HRESULT: 0x80070005 (Access Denied).

I tried to force and install winetricks dotnet40 dotnet48 dotnet9 on proton prefix, but I didn't change anything and the issue is still here.

If Wine handles this correctly, it's possible Proton could be improved to support .NET 9 applications better. Alternatively, if there's a known workaround, I would be very grateful to learn about it.

Thank you for your work on Proton and your support! 👍

steam-ff7s.log