Content registration

Add these examples to the first mod's OnInitializeMelon, after creating content. Register on the main thread before opening a world, then leave definitions unchanged.

Keys and ownership

content.Key("chip") produces example.firstmod:chip. IDs are case-sensitive, nonblank, and cannot contain : or surrounding whitespace. Keep released IDs stable.

Each assembly needs its own mod ID. Do not register the same key twice. Items, fluids, and gases share one namespace.

Categories

content.RegisterCategory(new CategoryDefinition
{
    Id = "machines",
    Name = "My Machines",
    SortOrder = 110
});

Parts can use the local category ID "machines". Cross-mod categories need a full key such as "other.mod:machines".

Items, fluids, and gases

Add using UnityEngine; for colours.

content.RegisterItem(new ItemDefinition
{
    Id = "chip", Name = "Control Chip", Mass = 0.1f, MaxStackSize = 100
});
content.RegisterFluid(new FluidDefinition
{
    Id = "coolant", Name = "Coolant", Mass = 1f, Color = Color.cyan
});
content.RegisterGas(new FluidDefinition
{
    Id = "gas", Name = "Example Gas", Mass = 0.01f, Color = Color.magenta
});

Use positive mass and stack sizes. Registration defines an item; your mod must provide a way to obtain it.

Parts and building costs

A part clones a donor by its exact asset name, such as Constant.

content.RegisterPart(new PartDefinition
{
    Id = "machine",
    Name = "Chip Machine",
    Donor = "Constant",
    Category = "machines",
    BuildingCost = new[]
    {
        new ItemCost { Item = ItemRef.Mod(content.Key("chip")), Quantity = 2 }
    }
});

This uses the category and chip above. A null building cost keeps the donor's cost; an empty array makes it free. Give the part its own unlock with Research, or it inherits donor research.

Resolve content after binding

Lookups become available when a world is ready:

content.WorldBound += () =>
{
    var reference = PartRef.Mod(content.Key("controller"));
    if (StriderRegistry.TryGetNumericId(reference, out var id))
        MelonLogger.Msg($"Controller ID: {id}");
};

Use TryGetPart, TryGetItem, or TryGetResearch when you need settings. Clear cached IDs/settings in WorldUnbinding; they belong to that world.

Full signatures and defaults are in Registry and references and Content definitions.