Fallout: New Vegas

Fallout: New Vegas (game_id fallout-new-vegas) is a built-in modde title backed by the shared, data-driven Gamebryo game plugin. The same plugin code drives Oblivion; the per-game differences (Steam app id, save folder name, INI set, Nexus domain) are configuration on a single GamebryoGame record.

Overall status: Partial. Deployment, filesystem scanning, BSA-aware conflict classification, save tracking, and plugins.txt load-order read/write all ship. What keeps New Vegas from Done is the absence of a bespoke, end-to-end script-extender (NVSE) bootstrap workflow and the deeper plugin-management UX (automatic master/ESM ordering, in-app conflict resolution) that the Bethesda Creation-Engine titles get. Treat New Vegas as a solid deploy-and-scan target, not a full Mod-Organizer replacement. The canonical status baseline is docs/capability-matrix.toml and the supported-games table.

Engine and overall status

The plugin advertises has_plugin_system() == true and supports_save_profiles() == true, so New Vegas participates in modde’s load-order and save-profile machinery.

How modde detects the install

New Vegas is registered with a Steam launcher binding and no Heroic GOG/Epic ids:

modde locates the install by walking your Steam libraries for app 22380, landing on steamapps/common/Fallout New Vegas. Because there is no Heroic binding shipped, GOG/Epic copies are not auto-detected for this title — point modde at the directory explicitly (--game-dir on the CLI, or gameDir in the home-manager module) if you run a non-Steam copy.

The numeric Nexus game id is intentionally None for New Vegas: the newvegas domain is enough for URL-based installs and update tracking, but the in-app “Browse Nexus” picker (which needs the numeric id) will not list this title until the id is confirmed. URL installs from nexusmods.com/newvegas/mods/<id> resolve correctly via the domain.

Mod directory and deploy strategy

The mod directory is <install>/Data — the same Data/ folder New Vegas itself reads plugins, meshes, textures, sound, and BSAs from.

modde never copies mods on top of your game files. It uses the standard symlink-farm virtual filesystem described in Deployment & VFS: mods are staged, the winning file for each relative path is resolved by load order, and the result is symlinked into Data/. This keeps the base install clean and every deploy reversible.

When modde unpacks a downloaded archive, the Gamebryo plugin’s analyze_mod_archive looks for a top-level Data/ directory inside the extracted mod. If present, it applies StripContentRoot { root: "Data" }, so a mod packaged as Data/MyMod.esp deploys its contents directly into the game’s Data/ rather than nesting a redundant Data/Data/. For archives that are not wrapped in Data/, the plugin’s bare-layout recogniser accepts the mod when it sees the expected loose roots — data, meshes, textures, sound, music, menus, scripts, shaders (matched case-insensitively) — or top-level .esp / .esm / .bsa files. This is what lets older “drop into Data” mods install without manual repackaging.

What scanning finds

modde scan --game fallout-new-vegas runs the Gamebryo scanner over the single Data directory. The scanner:

• reads the top level of <install>/Data (non-recursive);
• treats every .esp and .esm file as a discovered mod;
• pairs each plugin with a same-stem .bsa archive when one exists (e.g. MyMod.esp + MyMod.bsa are reported together as one mod’s files);
• assigns each mod the id plugin/<filename> with a fixed match confidence of 0.85;
• records each file’s install-relative path and on-disk size.

Loose meshes/textures dropped straight into Data/ without an accompanying plugin are not surfaced as distinct mods by this scanner — discovery is plugin-anchored. For matching an existing install against a Wabbajack manifest (including New Vegas lists, see below), combine the scan with --manifest; the scanner’s per-mod footprint is the lowercased plugin filename, which is what manifest matching keys on. See Mod Scanning for threshold, dry-run, and import flags.

Conflict classification

Two layers cooperate when New Vegas mods overlap.

Per-file collision severity (used when two deployed mods write the same relative path) comes from the BSA-aware collision policy:

.bsa is registered as the archive extension for the New Vegas collision classifier, so archive overlaps are reasoned about as packed content rather than loose files.

Per-mod safety classification (classify_mod, used to flag whether installing/toggling a mod can invalidate saves) uses the Gamebryo content policy:

• Save-breaking extensions: .esp, .esm, .pex, .dll, .obse, .nvse, plus anything under a scripts/ directory. Adding or removing these changes the form-id / script footprint a save depends on.
• Cosmetic extensions: .nif, .bsa, .dds, .png, .tga, .jpg, .kf, .wav, .mp3, .ogg, .ini, .xml.

The same policy also classifies content into categories used across the UI and reports — Plugin (esp/esm), Texture, Mesh, Sound, Script (including .obse/.nvse), Archive (bsa), Config, and Binary (dll). See Conflicts for how severities surface in the conflict report.

Save tracking

New Vegas save tracking is shipped (Done). On Linux and macOS the game runs through Proton/Wine, so the Gamebryo save tracker points at the compatibility prefix:

<Steam>/steamapps/compatdata/22380/pfx/drive_c/users/steamuser/Documents/My Games/FalloutNV/Saves

i.e. modde derives the save folder from the Steam compatdata directory for app 22380, then descends into the Wine prefix’s Documents/My Games/FalloutNV/Saves. (Note the on-disk folder name is FalloutNV, not the modde id fallout-new-vegas.) On Windows the game runs natively, so the same saves live at their native Windows location with no prefix involved.

What is fingerprinted in that directory:

• files with the .ess (save) and .fos (co-save) extensions;
• *.bak backups are excluded;
• detection is non-recursive (the top level of Saves only);
• every match is filed under the manual category, with the relative filename as its label, sorted newest-first by modification time.

Capture summaries use the by-category form, e.g. capture: 3 saves (3 manual), so save-profile snapshots tell you how many saves were rolled into each profile. Save profiles are enabled for this title. See Save Management for snapshot, restore, and per-profile isolation.

Plugin and load-order handling

New Vegas orders plugins through a plugins.txt-style file. modde ships read/write helpers for that format:

• Reading strips comment lines (# or ;), ignores blanks, and removes a leading * enabled-marker from each plugin name, yielding the ordered list of active plugins.
• Writing emits one plugin per line, each prefixed with * to mark it enabled (creating the parent directory if needed).

This gives modde a faithful round-trip of the active-plugin list. What is not yet shipped for New Vegas is the higher-level plugin UX the Creation-Engine titles have — automatic master/ESM sorting, LOOT-style ordering, or in-app conflict resolution. Curate complex load orders with an external sorter and let modde persist the result; this is part of why New Vegas is Partial.

Installer specifics

• FOMOD is the primary scripted-installer path. New Vegas mods that ship a fomod/ModuleConfig.xml are driven through modde’s FOMOD installer just like the Bethesda titles — see the FOMOD Installers guide for the option/flag selection flow.
• Data/-rooted and bare archives install without FOMOD via the StripContentRoot / bare-layout recognition described above.
• BSA archives (.bsa) deploy as opaque packed content; modde does not unpack them, and same-stem BSAs are tracked alongside their plugin.
• NVSE / OBSE / script plugins (.nvse, .obse, .dll) deploy as files into Data/ and are flagged save-breaking, but modde does not currently bootstrap the NVSE loader executable for you — install the script extender itself manually into the game root, then manage its plugins through modde.
• REDmod, .pak, and SMAPI installers are not applicable to this engine.

Gaming tools and Proton

New Vegas ships no OptiScaler profiles (optiscaler_profiles is empty for this title), so the upscaler presets that exist for Unreal titles like Stellar Blade do not apply here. The engine-agnostic overlays and the Proton tool still work: MangoHud, vkBasalt, ReShade, GameMode, and the per-game proton tool (Proton build selection, Wine prefix, environment variables, and DLL overrides) are all available through Tools & Overlays. DLL overrides matter for script extenders and ENB-style injectors that ship a d3d9.dll/dxgi.dll — set those through the proton tool’s override settings so the Wine prefix loads them.

Linux / Proton notes and gotchas

These notes cover the game’s runtime on Linux and macOS, where New Vegas runs through Proton/Wine. On Windows the game runs natively — there is no Wine prefix, and saves and INI files live at their native Windows locations. modde itself runs natively on all three platforms.

• Saves live in the Proton prefix, not your home directory. They are under steamapps/compatdata/22380/pfx/..., which is why a fresh prefix (deleting compatdata, switching Proton builds) appears to “lose” saves. modde reads them from exactly that path, so launch the game once under Proton before expecting save detection to find anything.
• No Heroic detection ships for New Vegas. GOG/Epic copies need an explicit game directory.
• Run the game once before deploying so Proton creates the prefix and the My Games/FalloutNV tree exists; INI files (Fallout.ini, FalloutPrefs.ini, FalloutCustom.ini) are generated on first launch.
• Script extenders are DLL injection. NVSE relies on Proton honouring the loader; verify the override and that the extender’s own files sit in the game root, not in Data/.
• The numeric Nexus id is unset, so use direct nexusmods.com/newvegas/... URLs rather than the in-app browse picker.

Worked example

Home-Manager profile

programs.modde = {
  enable = true;

  nexus.apiKeyFile = "/run/secrets/nexus-api-key";

  profiles.viva-new-vegas = {
    game = "fallout-new-vegas";
    installMode = "auto";
    gameDir = "/home/me/.local/share/Steam/steamapps/common/Fallout New Vegas";

    wabbajackList = {
      url = "https://example.com/viva-new-vegas.wabbajack";
      hash = "sha256-AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA=";
    };

    tools = {
      mangohud.enable = true;
      gamemode.enable = true;
      proton = {
        enable = true;
        # Honour a script-extender / injector DLL inside the prefix.
        settings.dllOverrides = "d3d9=n,b";
      };
    };
  };
};

If New Vegas is not installed yet, omit gameDir or set installMode = "await-game"; activation prints the next step and continues without failing, then deploys once you set gameDir and rebuild. See the Home-Manager Module reference for every option.

CLI

# Discover what is already in Data/ and import it into a profile
modde scan --game fallout-new-vegas --import-to viva-new-vegas

# Match an existing install against a Wabbajack New Vegas list
modde scan --game fallout-new-vegas \
  --manifest /path/to/viva-new-vegas.wabbajack \
  --import-to viva-new-vegas \
  --prune-duplicates

# Deploy the symlink farm into <install>/Data
modde deploy --profile viva-new-vegas --game fallout-new-vegas

# Snapshot saves from the Proton prefix into the profile
modde save snapshot --game fallout-new-vegas --profile viva-new-vegas

# Deploy then launch through Proton
modde play --game fallout-new-vegas

Wabbajack manifests that name the game FalloutNewVegas or FalloutNV both map to the fallout-new-vegas id, so either spelling in a modlist resolves to this title. See Wabbajack for the full modlist workflow.

See also

• Supported Games — status table and Wabbajack mapping
• Oblivion — the other Gamebryo title sharing this plugin
• Deployment & VFS
• Mod Scanning
• Conflicts
• Save Management
• FOMOD Installers
• Tools & Overlays
• Wabbajack
• Home-Manager Module
• Parity & capability matrix