The Old Realms — Assimilation Crash Fix

Harmony hot-patch that prevents IndexOutOfRangeException in TroopRoster.AddToCountsAtIndex caused by TOR assimilation when entering custom locations or during recruit/bind/summon flows. No save edits. Safe mid-playthrough.

Status

• Built on: Bannerlord 1.2.12.6623
• Tested on: The Old Realms 1.2.11
• Scope: Singleplayer

Why it crashes

AssimilationCampaignBehavior.SwapTroopsIfNeeded used:

TroopRoster.RemoveTroop(CharacterObject troop, int count, UniqueTroopDescriptor seed, int xp)

This call can resolve a stale roster element. The engine then feeds an invalid index into AddToCountsAtIndex and throws.

What this mod changes

• Replaces the seeded remover with a seedless, clamped path.
• Clamps removal to GetTroopCount(troop).
• Uses RemoveTroop(CharacterObject, int).
• Fallback removes one by one on exception.
• Assimilation outcomes are unchanged.

Known triggers (vanilla TOR)

• Interacting with custom locations like Hunger Woods and similar TOR custom locations.
• Being a vampire in an army with parties led by companions of other cultures.
• Solo companions in their own party visiting those locations and trying to recruit / bind / summon wraiths.

Installation (players)

• Vortex or MO2: install and enable. Load after TOR_Core.
• Manual: copy TOR_AssimilationFix to Mount & Blade II Bannerlord/Modules/, enable in the launcher, load after TOR_Core.

Load order: Bannerlord.Harmony → base modules → TOR_Core → TOR_AssimilationFix

Safe to add or remove mid-save.

Building (developers)

• Open Source/TOR_AssimilationFix.csproj in Visual Studio or Rider.
• Adjust game DLL reference paths if needed.
• Build Release. The DLL is copied to Modules/TOR_AssimilationFix/bin/Win64_Shipping_Client/.

How it works

A Harmony transpiler targets:

TOR_Core.CampaignMechanics.Assimilation.AssimilationCampaignBehavior
  .SwapTroopsIfNeeded(Hero, TroopRoster, CharacterObject, int)

and replaces calls to the 4-arg RemoveTroop(...) with a safe remover that does not depend on a cached index or seed.

Compatibility

• Conflicts only with mods that also patch the same method.
• If there is a conflict, place the preferred patch later in load order.
• This mod does not add its own logging or telemetry.

Changelog

• 1.0.0 — Initial release.

License

Licensed under the Apache License, Version 2.0. See LICENSE for details.

Links

• Nexus Mods: https://www.nexusmods.com/mountandblade2bannerlord/mods/8872
• Source: https://github.com/xmarre/TOR_AssimilationFix