Reforge

Reforge lets a Warhammer 40,000: Darktide mod replace the game's own files, such as particle effects, materials and shader programs, by shipping edited copies inside the mod folder. Players install the mod like any other DMF mod by dropping it into mods/. No installer runs, and no game file is changed on disk. Uninstalling means deleting the mod folder.

It has three parts:

Part	What it is
reforge.dll	A small native library (Rust). While the game runs, it serves read-only opens of registered bundle/… files from files in mods/….
reforge.lua	The Lua library that mods ship. It loads one shared copy of the DLL, lets several mods coexist, and reports a state for each replaced file.
reforge CLI	A tool for mod authors. It scaffolds a mod, records stock hashes, generates the Lua manifest and checks mods after game updates.

How it works

1. DMF loads the mod. The mod's script calls reforge.register_manifest(...).
2. In on_all_mods_loaded, the mod calls reforge.commit(). The library loads bin/reforge.dll through Mods.lua.ffi (LuaJIT FFI) and installs hooks on CreateFileW, CreateFileA and CreateFile2, in this process only.
3. For every registration, the DLL checks that the stock file still has the expected SHA-256. When it does, later read-only opens of that file get a handle to the mod's copy. When the game has been patched and the hash no longer matches, the file stays stock and the mod is told why.

What the DLL will and won't do

• It redirects only read-only opens under <game>/bundle/. Opens for writing or deleting always go to the real file.
• Replacements must live under <game>/mods/. Paths with .., drive letters or backslashes are refused.
• It makes no network calls, writes no files, and patches no memory apart from the three hooks.
• Only one copy hooks a process. If several mods ship reforge.dll, the first loaded copy is shared by all of them.
• Every export catches panics, so an internal bug falls back to stock files instead of crashing the game.

For mod authors

The steps below use Windows, Python 3.9+ and the reforge.cmd wrapper in this folder.

reforge init path\to\mods\MyShaderMod --author "Me"
reforge add path\to\mods\MyShaderMod 98bb14b1d247a0c8 --copy
rem edit path\to\mods\MyShaderMod\payload\98bb14b1d247a0c8 with your own tools
reforge pack path\to\mods\MyShaderMod --game "C:\...\Warhammer 40,000 DARKTIDE"
reforge build path\to\mods\MyShaderMod --game "C:\...\Warhammer 40,000 DARKTIDE"

• add records the stock file's SHA-256 in reforge.json. With --copy, it also copies the stock file into payload/ as a starting point for editing.
• add-virtual and add-virtual-dir serve files at game paths that do not exist yet. Use them for extra resources that a replaced bundle refers to.
• pack Oodle-compresses bundle payloads whose 512 KiB chunks are stored uncompressed. Use it after writing a bundle with your own tools. The game's DirectStorage reader crashes on stored chunks with "Failed to decompress ... from package". pack uses the Oodle library installed with the game, which is not redistributable, so it needs Windows. It checks every chunk by decompressing it again.
• build refuses a bundle payload that still has stored chunks, then validates everything and writes scripts/mods/<Mod>/reforge_manifest.lua. It also copies the current reforge.lua, bin/reforge.dll and bin/REFORGE_NOTICES.txt into the mod.
• After a game update, verify shows which stock files changed.

See docs/authoring.md for the Lua API, file states and coexistence rules, and docs/ABI.md for the C ABI.

File states

State	Meaning
active	This mod's file is being served.
shared	Another mod won, but it serves a byte-identical file.
compatible	Another mod won with the same contract string.
displaced	Another mod's different file is served.
refused	The stock file changed (game update), the payload is missing, or a path is invalid. See reforge.reason(handle).
restart_required	The game already opened this file this session with other contents. The change applies after a restart.
unavailable	reforge.dll could not be loaded.
pending	commit() has not run yet.

In game, /reforge lists every replaced file. /reforge on|off toggles redirects for files opened after that point. /reforge trace on|off|dump writes a file trace to the log.

Limits

• Files the game opened before reforge.dll was installed cannot be detected after the fact. Most effect and material bundles load with missions, after mods load. A file loaded at boot needs a restart to be picked up.
• Early-loaded bundles must keep the stock layout exactly. Darktide reads some bundles, such as the weapons of the character in the menu, before any mod runs, and loads them later with the stock chunk table. A replacement with a larger chunk crashes with "Failed to decompress ... from package". A smaller one crashes with read error 0x89240007, which means end of file. This was observed in game on 2026-09-26. reforge pack --game recompresses each chunk and pads it to the stock chunk size (Oodle ignores trailing bytes), which works for edits that keep the stock record list. New resources cannot be added to such a bundle. Put them in a package that the game never loads on its own, replace that package's bundle (mark it "late_load": true), and load it from the mod after reforge.commit(). See docs/authoring.md. Bundles the game first loads in missions may differ from stock; mark them late_load too.
• Game updates change stock hashes. Affected files fall back to stock until the mod is rebuilt against the new files.
• Polychromatic and some other mods ship Wobin's Asset Redirect, which is a separate hooking DLL. Two hooks serving the same file would race, so Reforge leaves any file that Asset Redirect also registers to Asset Redirect. That file reports displaced, and reforge.winner(handle) names the other mod. Files only one of them replaces are unaffected.

Building

• Windows (MSVC): powershell -File scripts\build.ps1 -Test. This builds, runs the harness and refreshes dist/.
• Linux cross-build + Wine: scripts/build-cross.sh.
• Tests:
  • luajit lua/tests/test_reforge.lua
  • python -m unittest discover -s cli/tests
  • lua/tests/integration.lua, which runs real LuaJIT FFI against the real DLL.

Release builds come only from GitHub Actions. Each tag produces a draft release with build provenance you can check with gh attestation verify reforge.dll --repo Vansinnet/Reforge. The DLL is unsigned. Antivirus heuristics may flag any unsigned DLL that hooks CreateFileW. Compare the file against the release's SHA256SUMS and attestation, and report false positives to your antivirus vendor. Never disable scanning.

Credits

Thanks to Wobin for the original Asset Redirect DLL for Darktide. His work showed that mods could serve replacement game resources from their own folders and inspired Reforge. Reforge is an independent implementation; it does not include Wobin's DLL or source code.

Licence

MIT, see LICENSE. The DLL includes MinHook (BSD-2-Clause); see THIRD_PARTY_NOTICES.md. Mods that ship reforge.dll must ship REFORGE_NOTICES.txt with it, and reforge build does that automatically.

Reforge is a community tool. It is not affiliated with Fatshark or Games Workshop.