harmony

name	harmony
description	Creates Harmony patches for method interception and runtime modification in BepInEx plugins. Use when: intercepting EFT game methods, modifying bot behavior, hooking into game lifecycle events, or patching third-party mod methods.
allowed-tools	Read, Edit, Write, Glob, Grep, Bash

Harmony Skill

Harmony is the runtime patching library used by BepInEx to intercept and modify game methods without touching original assemblies. In BotMind, Harmony patches are used to hook into EFT's game lifecycle (raid start/end), bot spawning events, and player interactions. All patches live in src/client/Patches/ and are auto-applied via Harmony.PatchAll() in BotMindPlugin.cs.

Quick Start

Prefix Patch (Run Before Original)

[HarmonyPatch(typeof(GameWorld), nameof(GameWorld.OnGameStarted))]
internal static class GameStartedPatch
{
    [HarmonyPrefix]
    private static void Prefix()
    {
        try
        {
            MedicBuddyController.Instance?.OnRaidStarted();
            BotMindPlugin.Log?.LogInfo("Raid started - modules initialized");
        }
        catch (Exception ex)
        {
            BotMindPlugin.Log?.LogError($"GameStartedPatch error: {ex.Message}");
        }
    }
}

Postfix Patch (Run After Original)

[HarmonyPatch(typeof(GameWorld), "Dispose")]
internal static class GameWorldDisposePatch
{
    [HarmonyPostfix]
    private static void Postfix()
    {
        MedicBuddyController.Instance?.OnRaidEnded();
        LootFinder.ClearCache();
    }
}

Key Concepts

Concept	Usage	Example
[HarmonyPatch]	Declares target method	[HarmonyPatch(typeof(BotOwner), "Update")]
[HarmonyPrefix]	Runs before original, can skip	Return false to skip original
[HarmonyPostfix]	Runs after original	Access __result to modify return
[HarmonyTranspiler]	IL-level modification	Inject/remove instructions
__instance	Reference to patched object	BotOwner __instance
__result	Return value (postfix only)	ref bool __result

Common Patterns

Conditional Execution with Prefix

When: Skip original method based on custom logic

[HarmonyPrefix]
private static bool Prefix(BotOwner __instance)
{
    // Skip original if MedicBuddy bot
    if (MedicBuddyController.IsMedicBuddyBot(__instance))
        return false; // Don't run original
    
    return true; // Run original
}

Modifying Return Values

When: Change what a method returns without rewriting it

[HarmonyPostfix]
private static void Postfix(ref bool __result, BotOwner __instance)
{
    // Force bots to always consider looting safe
    if (BotMindConfig.ForceEnableLooting.Value)
        __result = true;
}

Accessing Private Fields

When: Read/write private state from patched class

[HarmonyPostfix]
private static void Postfix(BotOwner __instance)
{
    var privateField = Traverse.Create(__instance)
        .Field("_internalState")
        .GetValue<BotState>();
}

See Also

• patterns - Patch types, parameter injection, error handling
• workflows - Creating patches, debugging, testing

Related Skills

• See the bepinex skill for plugin lifecycle and when patches are applied
• See the csharp skill for reflection patterns used with Traverse
• See the unity skill for MonoBehaviour lifecycle hooks that complement patches