macOS Apple Silicon: Valheim starts but BepInEx does not load when Doorstop injection is lost through Rosetta launch

[No898]

Summary

On Apple Silicon macOS, BepInExPack_Valheim can launch Valheim successfully while BepInEx/Doorstop is never injected. The game reaches the menu and can join a server, but no BepInEx/LogOutput.log is created and no plugins load.

This appears to happen because the macOS start script needs to run Valheim's x86_64 slice through Rosetta, but the DYLD_INSERT_LIBRARIES environment used by Doorstop is not present at the final Valheim process when the architecture switch happens.

I found the related draft PR #20 for broader Valheim Apple Silicon support. This issue is narrower: a current-user failure mode in the packaged Valheim start script and a small workaround that restores Doorstop injection.

Environment

• Game: Valheim 0.221.12 (network version 36)
• BepInEx distribution: BepInExPack_Valheim 5.4.2333 from Thunderstore
• OS: macOS 26.3.1 (25D2128)
• Hardware: Apple M4, arm64
• Install path: external Steam library under /Volumes/FitKid/SteamLibrary/steamapps/common/Valheim
• Launch method: Steam launch options running start_game_bepinex.sh

Reproduction

1. Install Valheim from Steam on Apple Silicon macOS.
2. Install BepInExPack_Valheim 5.4.2333.
3. Configure Steam launch options to run start_game_bepinex.sh.
4. Launch Valheim from Steam.

Expected behavior

BepInEx preloader and chainloader start, BepInEx/LogOutput.log is created, and plugins under BepInEx/plugins are loaded.

Actual behavior

Valheim starts normally, but BepInEx does not load:

• BepInEx/LogOutput.log is not created.
• No plugin load messages appear.
• Valheim's player log shows the game running as unmodded, for example:

isModded: False

The game itself continues to run, so the failure is easy to miss unless the BepInEx log is checked.

Local diagnosis

The packaged macOS start script switches to Rosetta/x86_64 for Valheim. In the failing case, Valheim launches, but Doorstop is not injected.

When I set DYLD_LIBRARY_PATH and DYLD_INSERT_LIBRARIES inside an x86_64 shell immediately before exec-ing the Valheim executable, BepInEx loads correctly.

Successful log after the workaround:

[Message:   BepInEx] BepInEx 5.4.23.3 - Valheim
[Message:   BepInEx] User is running BepInExPack Valheim version 5.4.2333 from Thunderstore
[Message:   BepInEx] Chainloader started
[Info   :   BepInEx] 11 plugins to load
[Info   :   BepInEx] Loading [Craft From Containers 3.8.2]
[Info   :   BepInEx] Loading [BalrondShipyard 1.6.5]
[Info   :   BepInEx] Loading [NoTreeStump 1.0.3]
[Info   :   BepInEx] Loading [Jotunn 2.29.0]
[Info   :   BepInEx] Loading [Better Wisps 1.0.42]
[Info   :   BepInEx] Loading [ShaderHelperForMac 2.0.0]
[Info   :   BepInEx] Loading [Skills Preview 0.4.2]
[Info   :   BepInEx] Loading [Quick Stack - Store - Sort - Trash - Restock 1.4.13]
[Info   :   BepInEx] Loading [Sailing 1.1.8]
[Info   :   BepInEx] Loading [Display Day & Time in HUD 1.1.2]
[Info   :   BepInEx] Loading [RecyclePlus 1.3.0]
[Message:   BepInEx] Chainloader startup complete

Workaround

For the current Valheim start script, this works locally:

1. Enter an x86_64 shell with arch -x86_64 /bin/sh -c.
2. Set DYLD_LIBRARY_PATH and DYLD_INSERT_LIBRARIES inside that shell.
3. exec the Valheim executable from there.

I am opening a small PR with that workaround scoped to the Valheim start script. It is not intended to replace the broader native Apple Silicon work in #20.