Same problem
System:
OS: EndeavourOS x86_64
Kernel: Linux 7.0.14-zen1-1-zen
Display (SAM7778): 2560x1440 in 27", 240 Hz [External]
WM: niri 26.04 (Wayland)
CPU: AMD Ryzen 7 7800X3D (8) @ 5.05 GHz
GPU 1: AMD Radeon RX 9070 XT [Discrete]
GPU 2: AMD Raphael [Integrated]
Memory: 7.46 GiB / 46.11 GiB (16%)

Full system info https://gist.github.com/rocket-duck/25f7a10d7d5f86e51810f9756d97d740
Logs: https://gist.github.com/rocket-duck/581098a2e70d37b6991f8fd7c1bc8f34

Same problem for me

Compatibility Report

• Name of the game with compatibility issues: Diablo IV
• Steam AppID of the game: 2344520

System Information

• GPU: NVIDIA GeForce RTX 5080 Laptop GPU
• Driver/LLVM version: NVIDIA 610.43.02 (nvidia-open)
• Kernel version: 7.1.2-3-cachyos (CachyOS, KDE Plasma 6 / Wayland)
• Link to full system information report as Gist:
• Proton version: proton-experimental (experimental-11.0-20260622b) — also reproduces on Proton Hotfix (hotfix-20260616) and GE-Proton11-1

Symptoms

Since Diablo IV patch 3.1.0 (Build #72578, 2026-06-30) the game no longer
launches. Steam shows "Running" for ~4–7 seconds, then the process exits. No
window is ever created and no error dialog is shown in Steam.

The game dies inside Blizzard's anti-tamper loader before any graphics
initialization (no D3D12/VKD3D device is ever created — VKD3D never logs).
PROTON_LOG=1 shows a handled-then-fatal EXCEPTION_BREAKPOINT (0x80000003)
originating in diablo_iv_loader.dll:

warn:seh:dispatch_exception backtrace: --- Exception 0x80000003.
trace:seh:dispatch_exception code=80000003 (EXCEPTION_BREAKPOINT) ...
warn:seh:virtual_unwind backtrace: ... L"diablo_iv_loader.dll" + 0x...4A05
warn:seh:virtual_unwind backtrace: ... L"diablo_iv_loader.dll" + 0x...95C6
...
pid != , skipping destruction (fork without exec?)

Blizzard's own crash handler reports the same (seen by other affected users):
<BlizzardError.ProjectId>4
BREAKPOINT
diablo_iv_loader.dll (+ ...4A05)
diablo_iv_loader.dll (+ ...95C6)
ntdll.dll RtlUserThreadStart+0

This is not a GPU/driver fault: no Xid in dmesg, no VK_ERROR_DEVICE_LOST,
and the Proton helper xalia.exe initializes the RTX 5080 via Vulkan without any
problem in the same run.

Ruled out

• Cleared the game's shader cache — no change.
• Verified integrity of game files — passed, no change.
• Disabled the Steam in-game overlay — no change.
• Reset LocalPrefs.txt in the prefix — no change.
• Reproduces identically on Proton Experimental, Proton Hotfix and GE-Proton11-1.
• Other users report the same launch crash on Windows/Steam, so the patch-3.1.0
  loader change is likely the trigger; under Wine/Proton the loader's breakpoint
  (INT3) anti-tamper path aborts instead of continuing.

Reproduction

1. Have Diablo IV (AppID 2344520) updated to patch 3.1.0 (Build #72578).
2. Set launch options PROTON_LOG=1 %command%, force Proton Experimental.
3. Launch from Steam.
4. Game runs ~4–7 s, then exits with no window; ~/steam-2344520.log shows the
   EXCEPTION_BREAKPOINT in diablo_iv_loader.dll as above.

Confirming this affects AMD GPU as well, not just NVIDIA.

System:

• GPU: AMD Radeon RX 7900 XT (Navi 31 / RADV)
• iGPU: AMD Ryzen 9 7900X (Raphael, RADV) — integrated, not used for gaming
• Mesa/Vulkan driver: 26.1.3
• Vulkan API: 1.4.348
• Kernel: 7.0.13-arch1-1 (Arch Linux)
• Launcher: Lutris + UMU + GE-Proton (tested GE-Proton10-33, GE-Proton10-34, GE-Proton11-1, UMU-Proton-9.0-4e — all identical failure)
• Game version: 3.1.0.72592 (updated June 30, 2026)

Symptom: Game launches, runs for ~9 seconds, exits silently. No window ever appears.

Root cause (from Blizzard's own crash reporter): diablo_iv_loader.dll hits an INT3 (BREAKPOINT) in the main thread before any graphics initialization — no D3D12, no Vulkan device creation. The crash is identical across two attempts with the same two offsets:

<BlizzardError.Summary> BREAKPOINT </BlizzardError.Summary>
Thread 0x00000898 "Main Thread"
DBG-ADDR<00006FFFF7C84A05>("diablo_iv_loader.dll")
DBG-ADDR<00006FFFF70495C6>("diablo_iv_loader.dll")
DBG-ADDR<00006FFFFFEFFF30>("ntdll.dll")
00006FFFFFF001E8 ntdll.dll RtlUserThreadStart+0

Loaded module confirms it's the patch-day build:

DBG-MODULE diablo_iv_loader.dll "D:\Jenkins\workspace\eidolon-generator_main\fen_retail_workspace__build\vs2022\RelWithDebInfo\loader.pdb" timestamp 1772221093
DBG-MODULE Diablo IV.exe "branches\3_1_0\bin\Release\Fenris_er.pdb" timestamp 1782256640

Ruled out: GPU/driver (no Vulkan errors, no device lost), shader cache (cleared), file integrity (verified), Proton version (fails on all).

Conclusion: The new diablo_iv_loader.dll shipped in patch 3.1.0 triggers a breakpoint that Wine/Proton handles differently than Windows, causing an abort before the game initializes. Not GPU-vendor specific.