SlotKit

Formerly MenuKit: Containers. Mods built for Containers need an update, and the upgrading guide has the steps. Inventory Max stays on MenuKit: Containers 6.2.0, which is still in this project's version list.

SlotKit is a slot library for Fabric mods, built on MenuKit. A mod uses it to find and act on the slots in any menu, or to build real slots and custom menus that persist and sync.

It has two tiers, and a mod needs SlotKit on the other side only for the second:

Tier	Needs SlotKit on	Adds
Client	The client only. Works on any server, vanilla included.	Slot groups and categories in every menu, slot operations, vetoes and gates, panels placed against a slot group
Client and server	Both sides	Created slots, custom container menus, storage attachments, per-slot state

What it does:

• Publishes every slot group, vanilla or created, under a category any mod can read, with or without a menu open.
• Names each thing that can be done to a slot as an operation. Vanilla has eleven, one per gesture, and a mod can add its own. A slot answers for itself first, then its group, then its category, and a locking mod can veto any operation.
• Places a MenuKit panel against a slot group, so it shows on every screen with that group: the survival inventory, every chest, and every other container.
• Creates slots as UI components. A pocket, an extra equipment slot or a satchel is each a real Slot, synced by vanilla's protocol, and shows on every container screen with no per-screen setup.
• Adds custom container menus built from MenuKit panels.
• Makes created slots behave like vanilla ones in creative and survival, on death, and with Curse of Binding and Mending.
• Attaches per-slot state to any slot, either private to each player or shared by everyone viewing it. The server checks every write a client sends. The state is stored on the slot's owner (a player, block, entity or item), where /data get can read it.
• Checks which mods each side has before the world loads. A server refuses only players missing a mod that builds slots, and names the mods to install, with links. Everyone else joins.

Requires MenuKit 7 and Fabric API. Worlds and player files saved with MenuKit: Containers load with no conversion, and shulker boxes keep their contents and slot state.

Install

Minecraft 26.3 is unobfuscated, so SlotKit goes on the plain implementation configuration, beside MenuKit:

repositories {
    maven { url 'https://api.modrinth.com/maven' }
}
dependencies {
    implementation 'maven.modrinth:menukit:7.0.0+26.3'
    implementation 'maven.modrinth:xQUBXV8I:1.0.0+26.3'   // SlotKit
}

xQUBXV8I is SlotKit's Modrinth project id. It resolves whatever the project's slug is.

Declare both in fabric.mod.json, each against its own version, with both bounds (why):

"depends": { "menukit": ">=7.0.0 <8.0.0", "slotkit": ">=1.0.0 <2.0.0" }

A mod that builds slots or custom menus also declares that it needs SlotKit on both sides:

"custom": { "slotkit": { "bothSides": "required" } }

Example

A panel above the player inventory, registered once from the client entry point. It uses the client tier, so it works on any server:

Panel panel = Panel.builder("mymod:toolbar")
        .style(PanelStyle.NONE)
        .elements(toolbarButtons)
        .position(PanelPosition.region(OutsideRegion.TOP_ALIGN_RIGHT))
        .visibleWhen(() -> config.toolbar)
        .build();
new SlotGroupPanelAdapter(panel)
        .on(SlotGroupCategory.PLAYER_INVENTORY);

Nine synced pocket slots on every container screen, registered once from the common entry point. These need SlotKit on both sides:

public static final PlayerStorageAttachment<NonNullList<ItemStack>> POCKETS =
        StorageAttachment.playerAttached("mymod", "pockets", 9);

ContainerPanel.define("mymod:pockets")
        .at(OutsideRegion.LEFT_ALIGN_TOP, 7)
        .style(PanelStyle.RAISED)
        .addSlot(SlotSpec.at("pockets", SlotGroupCategory.PLAYER_INVENTORY).count(9)
                .storage(player -> POCKETS.bind(player)))
        .register();

The panel id's namespace is the mod's id. define throws at startup when it is not, or when the mod does not declare required.

The public API

The API is every type in a package named api: com.trevlar.slotkit.api.*. The version contract covers those. Every other package is internal and can change in any release. A task that seems to need an internal type is a gap in the API. Open an issue for it.

Docs

• Getting started: the dependency, a panel beside the player inventory, nine real slots.
• Concepts: the two tiers, declaring sides, slot groups, operations, created slots, addresses, slot state.
• Recipes: the common tasks.
• Limits: what SlotKit does not do, and the open gaps.
• Versioning: what a version number promises.
• Upgrading: moving a mod from MenuKit: Containers or from MenuKit 6's slot code.

Compatibility

Minecraft 26.3, Fabric. SlotKit replaces MenuKit: Containers, so the two cannot be installed together, and neither can SlotKit and Inventory Max. A player who keeps Inventory Max keeps the whole 6.2 set (MenuKit 6.2.0 and MenuKit: Containers 6.2.0) in a separate profile.

License

MIT.

Issues

github.com/trevorschoeny/slotkit/issues.