Wabbadrift

Using a Wabbajack modlist as your baseline? Wabbadrift shows what drifted (mods, plugins, configs) and recovers the FOMOD installer choices each mod was installed with, so you can see which options the list picked and where yours differ. Update or restore mods with backup and undo.

It compares your Mod Organizer 2 (MO2) instance with a clean install of the same list, file by file.

It works with any MO2-managed game and any Wabbajack modlist.

What you need

• Windows (MO2 and Wabbajack are Windows tools).
• Python 3.10 or newer. Tick Add Python to PATH when installing.
• Your MO2 instance, the one you play and customise.
• A baseline: a clean install of the same list made by Wabbajack, in its own folder. It's the reference Wabbadrift compares against, so keep it untouched.
• The list's .wabbajack file. Wabbajack keeps it under <Wabbajack folder>\<version>\downloaded_mod_lists\.
• Optional, for reading FOMOD installer choices: 7-Zip. Wabbadrift finds a 7-Zip install or the copy bundled with Wabbajack on its own.

Starting it

Double-click wabbadrift.bat. The first start sets up a private Python environment in the .venv folder and installs two packages (this needs an internet connection and takes a few seconds). After that, it starts the local server and opens Wabbadrift in your browser. Keep the console window open while you use it; closing it stops Wabbadrift.

Wabbadrift only listens on your own computer (localhost). To use another port, copy .env.example to .env and change WABBADRIFT_PORT.

Setting up a comparison

The first start opens the setup form. Later, use New to add another comparison and Details → Edit to change one. You can keep as many comparisons as you like.

1. Give it a name (letters, digits, - and _).
2. Your instance: the MO2 folder (the one with ModOrganizer.exe and ModOrganizer.ini), then pick the profile.
3. Baseline instance: the same for the clean install.
4. Wabbajack list: the .wabbajack file. The form shows the list's name and version once it can read it.
5. Optional settings: game folders and the downloads folder (taken from ModOrganizer.ini when left empty), the LOOT userlist, and where to keep backups.

Every path is checked before the comparison is saved.

What it shows

Tab	Shows
Mods	Mods only in the baseline, only in your instance, at a different version, or with changed files. Open a mod to compare its files and diff its text files.
Plugins	Plugins added, removed, moved or enabled differently, and LOOT group differences.
Game root	Files in the game folder that differ from what the list installs.
Configs	Profile INIs, MO2 settings, executables and config files inside mods.
Leaks	Paths in your instance that still point into the baseline, into Wabbajack's folders, or to places that don't exist.
FOMOD	The installer options the list chose for each FOMOD mod, and where your copy differs.
Updates	What a new version of the list changes, and whether each change is safe to apply to your instance.
History	Every set of changes you applied, with Undo.

Some differences are expected: generated outputs, files tied to the game version, settings that depend on the machine, and separators you mark as your own. They are hidden by default; Show expected drift brings them back. The rules for this live in data/pairs/<name>.rules.yaml, which you can edit.

Details shows what a comparison compares, including each instance's game version and the game version the list was built for.

Adding and resetting mods

In the Mods tab, tick mods in the Change column:

• Add copies a mod you don't have from the baseline into your instance, places it in your modlist next to its neighbours from the baseline, and enables its plugins.
• Reset makes your copy of a mod identical to the baseline's. Files you added to it are removed (they're backed up first).

Review changes shows exactly what will happen before anything is written: every file, where each mod and plugin goes, and the edits to modlist.txt, plugins.txt and loadorder.txt. Apply then:

• refuses while MO2 is running for your instance,
• refuses if anything changed since you reviewed it,
• backs up every file it overwrites or removes, and
• records the changes in History, where Undo restores your instance exactly. Undo refuses, and lists the files, if you've edited any of them since.

What gets written

• Your instance: only when you apply changes, and only its mods folder and profile.
• The baseline and the .wabbajack: never.
• Wabbadrift's own data folder: comparisons, rules, caches, snapshots of list versions, and backups (unless you chose another backup folder).

For developers

python -m venv .venv
.venv\Scripts\pip install -r requirements-dev.txt
.venv\Scripts\python -m pytest
.venv\Scripts\python -m wabbadrift.server --no-browser

The tests build small synthetic MO2 instances and .wabbajack files; they never touch a real install. DESIGN.md explains how it works and why.