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Launcher Compatibility

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Bobby Comet edited this page Sep 11, 2026 · 2 revisions

Overview

Kalium is a Linux helper that installs and manages Mod Organizer 2 (MO2) as a non-Steam game under Proton.
It creates isolated Wine/Proton prefixes, handles dependencies, registers games, provides NXM support, LOOT, USVFS fixes, and more.

Core principle: Every MO2 instance is independent (own AppID, own prefix, own ModOrganizer.ini). Multiple instances are fully supported.

Supported Launchers & Detection

Source Auto-detected? How it works Notes
Native Steam Yes Scans standard Steam paths + libraryfolders.vdf Full support (games + prefixes)
Flatpak Steam Yes ~/.var/app/com.valvesoftware.Steam/... Full support
Snap Steam Yes ~/snap/steam/common/.local/share/Steam Full support
Heroic (native) Yes Reads GOG + Epic/Legendary library files GOG & Epic games
Heroic (Flatpak) Yes Flatpak config path Same as above
Bottles Yes Scans bottle prefixes + Windows registry Good for non-Steam games
GOG Galaxy (native) No — Only auto if installed via Heroic. Otherwise manual folder pick
Manual / other No User browses to game folder Always available as fallback

Kalium aggregates detection via detect_all_games() (Steam + Heroic + Bottles).

Main Workflows

First-time Setup / Install New MO2

  1. Launch Kalium → MO2 tab → Install New MO2.
  2. Choose an Instance Name.
  3. Choose Install Location (empty folder recommended).
  4. Step 3 – Game to manage:
    • Select a detected game, or
    • Choose a known game template and Browse to its folder.
    • (You can skip, but the instance may not open cleanly.)
  5. Select a Proton 10+ version (Experimental / GE-Proton recommended).
  6. Leave “Update USVFS to 0.5.7.2” checked (strongly recommended).
  7. Start Installation.

Kalium will:

  • Create a non-Steam Steam shortcut
  • Create an isolated Proton prefix
  • Download & extract latest MO2
  • Install Windows dependencies (vcrun, .NET, etc.)
  • Apply USVFS 0.5.7.2
  • Write gameName + gamePath into ModOrganizer.ini
  • Register game paths in the Wine registry
  • Create Kalium Tools scripts
  • Register the instance in managed_prefixes.json

After install: Fully exit Steam → restart Steam → launch the new non-Steam entry.

Setup Existing MO2

Same wizard, but choose Setup Existing MO2 and point at a folder that already contains ModOrganizer.exe.
Kalium adds the Steam shortcut + prefix + dependencies around it.

Multiple MO2 Instances

Fully supported.

  • Each instance gets its own AppID and Proton prefix.
  • You can have several instances managing the same game or different games.
  • Switch between them freely in Steam (Non-Steam games list).
  • NXM can only be active for one instance at a time (changeable in Settings).

NXM (Nexus Mods) Handling

  1. After at least one MO2 instance exists, go to Settings.
  2. Select the desired instance → Enable NXM.
  3. In your browser, set nxm:// links to open with Kalium NXM Handler.

Downloads will now land in the active MO2 instance.

LOOT

In Settings → select managed instance → Install LOOT.

Kalium:

  • Downloads portable LOOT
  • Writes run_loot.bat with the correct --game=
  • Registers LOOT.exe as a custom executable in MO2
  • Ensures vcrun2022 is present in the prefix

USVFS / Performance Fix

MO2 2.5.2 ships usvfs 0.5.6.x which can cause severe slowdowns and duplicated virtual folders on Wine/Proton 10.20+.

Kalium automatically (or on demand) updates to usvfs 0.5.7.2.

Also recommended:

  • Settings → Set VFS max_memory (defaults to 2 GB)

Path Fixes (Custom Executables)

Qt/Wine sometimes rewrites paths with backslashes.
Run:

kalium fix-paths -p /path/to/your/MO2

or use the Launch script Kalium creates (it runs the fix automatically).

Backpatching (Version Pinning)

Supported games: Skyrim SE, Fallout 4, Starfield, Cyberpunk 2077, Witcher 3.

Workflow options:

  • Steam Console method (recommended for most users)
  • steamcmd (if available)
  • Apply already-downloaded depots

Use the Version / Backpatch section in the GUI or the CLI (kalium backpatch-skyrim ...).

Diagnostics & Maintenance

  • Diagnostics page → full health report (also writes a file you can paste into GitHub issues)
  • kalium status
  • kalium list-mo2
  • kalium check-steam
  • kalium diagnose

Useful buttons in Settings:

  • Update USVFS
  • Set VFS max_memory
  • Install LOOT
  • Ensure vcrun2022
  • Open prefix folder
  • Delete prefix (careful!)

Recommended Daily Workflow

  1. Fully exit Steam before installing or repairing shortcuts.
  2. Use one MO2 instance per major profile/setup (or per game if preferred).
  3. Keep USVFS 0.5.7.2 + reasonable VFS memory.
  4. Enable NXM only for the instance you currently use.
  5. Launch MO2 via the Steam non-Steam shortcut (or the Kalium “Launch …” script).
  6. After adding custom executables (SKSE, xEdit, etc.), run kalium fix-paths if paths look wrong.
  7. For secondary drives / SD cards → Kalium automatically injects STEAM_COMPAT_MOUNTS.

Common Gotchas

  • Steam is running while writing shortcuts → Steam overwrites shortcuts.vdf on exit. Always fully exit Steam first.
  • Flatpak / Snap Steam → detection works, but some path edge cases can appear; Kalium normalizes them.
  • GOG games → prefer installing them through Heroic for automatic detection.
  • First launch of a new instance → may need one manual launch so ModOrganizer.ini is fully created before some tools (LOOT registration, etc.) work perfectly.
  • Secondary drives → rely on STEAM_COMPAT_MOUNTS (Kalium sets this automatically in launch options).

Quick Reference – CLI Commands

kalium                          # GUI
kalium setup-mo2 -p /path -n "Name"
kalium list-mo2
kalium status
kalium diagnose
kalium enable-nxm
kalium install-loot -p /path/to/MO2
kalium install-usvfs -p /path/to/MO2
kalium fix-paths -p /path/to/MO2
kalium set-vfs-memory -p /path/to/MO2
kalium check-steam

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