Installing BepInEx 6 (IL2CPP)

Find the game's install folder

In Steam, right-click Two Point Museum → Manage → Browse local files. A window opens at the game root. On the example PC that folder is:

F:\SteamLibrary\steamapps\common\Two Point Museum\

Yours will differ by drive and library, but the folder name is always Two Point Museum and it always contains TPM.exe.

Confirm it's the IL2CPP build

In that folder, check these three exist. Their presence is what makes this an IL2CPP game and tells you the IL2CPP loader is the right one:

• TPM.exe — the launcher (~667 KB).
• GameAssembly.dll — the game's native-compiled code (very large, ~340 MB).
• TPM_Data\ — the Unity data folder.

Fully close the game

Make sure Two Point Museum isn't running (and isn't mid-update in Steam). Files like winhttp.dll can't be written while the game holds them.

Extract the archive into the game root

Open TPM-BepInEx-Unity.IL2CPP-win-x64-6.0.0-be.784.rar in WinRAR or 7-Zip and extract its contents directly into the game folder — the same folder as TPM.exe. The simplest way: drag the archive into the game folder, then Extract Here.

When it's done, the game root should look exactly like this (the four green items are what the archive just added):

├─ BepInEx/                     # NEW — the loader
├─ dotnet/                      # NEW — bundled .NET 6 runtime
├─ D3D12/                       # game's own
├─ DLCs/                        # game's own
├─ LicensingInfo/               # game's own
├─ TPM_Data/                    # game's own (Unity data)
├─ .doorstop_version            # NEW
├─ baselib.dll                  # game's own
├─ changelog.txt                # NEW (BepInEx)
├─ checksum_manifest_md5.txt    # game's own
├─ doorstop_config.ini          # NEW
├─ GameAssembly.dll             # game's own (IL2CPP native code)
├─ TPM.exe                      # launch THIS
├─ UnityCrashHandler64.exe      # game's own
├─ UnityPlayer.dll              # game's own
├─ version.txt                  # game's own
└─ winhttp.dll                  # NEW — the hook that loads BepInEx

Here's that exact state in File Explorer — click to view it full size:

⤢ full size

Sanity-check the four new items

Before launching, confirm these four sit in the game root next to TPM.exe:

If any are missing or buried in a subfolder, redo Step 4. That's the single most common reason BepInEx "does nothing" on first launch.

Launch once and let it build interop

Start Two Point Museum normally (through Steam, or by running TPM.exe). Let it reach the main menu and sit for a minute, then quit to desktop.

On this first run, BepInEx does its one-time heavy lifting: it unpacks the Unity base libs and generates the Il2Cpp interop assemblies — the managed "mirror" of the game's native classes that every plugin (including Ungodly AI) is compiled against. This can take a little longer than a normal boot and may show a console window; that's expected.

Confirm BepInEx attached

Open the BepInEx folder again. After that first launch it should now contain three new generated folders plus two log files:

├─ cache/          # NEW on first run — type/assembly cache
├─ config/         # NEW on first run — BepInEx.cfg is created here
├─ core/           # from the archive
├─ interop/        # NEW on first run — generated Il2Cpp proxies ★ the key one
├─ patchers/       # from the archive (empty)
├─ plugins/        # your mod goes here in Phase 2
├─ unity-libs/     # from the archive
├─ ErrorLog.log    # NEW on first run
└─ LogOutput.log   # NEW on first run — read this to confirm the load

That's the real folder after a clean first run — click to enlarge:

⤢ full size

Open LogOutput.log in a text editor. A healthy first run reads roughly like this (versions and paths will match your machine):

[Message:   BepInEx] BepInEx 6.0.0-be.784 (TPM / Unity 6000.0.63)
[Info   :   BepInEx] CLR runtime version: 6.0.x
[Message:   BepInEx] Preloader started
[Info   :Il2CppInterop] Generating Il2Cpp interop assemblies
[Info   :Il2CppInterop] Wrote interop assemblies to ...\BepInEx\interop
[Message:   BepInEx] Chainloader initialized
[Info   :   BepInEx] 0 plugins to load     # expected — no mod installed yet