Compatibility Report

Name of the game with compatibility issues: Armored Core VI Fires of Rubicon
Steam AppID of the game: 1888160

System Information

GPU: Intel Arc B390 (Xe3, Panther Lake) — MSI Claw 8 EX AI+ (CG3EM)
Driver/Mesa version: Mesa 26.2.3-arch3.1 (OpenGL 4.6 Compatibility Profile)
Kernel version: 7.2.3-3-cachyos-deckify
Distro: CachyOS
Proton versions tested: GE-Proton11-7, Proton Experimental (both fail identically)

Symptoms
Game window shows a brief white/black screen, then either silently closes back to Steam or hangs before terminating. vkd3d-proton successfully creates a Vulkan swapchain, confirming basic GPU/driver init works. The crash occurs shortly after, inside the game's own code.

Steps already tried (all failed to resolve):

Switching between Proton Experimental and multiple GE-Proton builds
Fully resetting the Proton prefix (compatdata/1888160 deleted, rebuilt clean)
Clearing vkd3d-proton.cache
Verifying game file integrity via Steam (15,272/15,272 files validated, no corruption)
Bypassing EasyAntiCheat entirely (renamed armoredcore6.exe to start_protected_game.exe) — crash persists identically, ruling out EAC as the cause

Reproduction / Log details
Two distinct exception patterns observed across attempts:

EXCEPTION_ACCESS_VIOLATION (0xc0000005) at armoredcore6.exe+0x29214f9, disassembling to movl $0xdeadba, 0 — a deliberate write to a null pointer.
A separate EXCEPTION_ACCESS_VIOLATION at armoredcore6.exe+0x303c8aa, thrown and caught in a tight repeating loop (~30ms intervals) via a vectored exception handler, causing the process to hang before eventually terminating.

Full Proton log (PROTON_LOG=1) available on request — please let me know if a gist/paste link is preferred for the full trace, as it's several hundred MB across attempts.