fix: avoid OpenGL driver loading in unit tests

I'm never doing an update where I have to keep track of 650+ structure files again

See merge request cable-mc/cobblemon!2414

CHANGELOG.md

@@ -1,41 +1,45 @@
 # Changelog
-## [1.8.1 (September 13th, 2026)](#1-8-1)
+## [1.8.2 (MONTH xth, 2026)](#1-8-2)
+
+### Additions
+- The following items can now be placed on the ground as blocks:
+  - King's Rock, Galarica Cuff, Unremarkable Teacup, Masterpiece Teacup, Chipped Pot, Cracked Pot, Sachet, Metal Powder, Quick Powder, Bright Powder, Icy Rock, Heat Rock, Smooth Rock, Damp Rock, Destiny Knot, Luminous Moss, Never-Melt Ice, Wide Lens, Scope Lens, and Zoom Lens.
+  - Iron Ball, Metal Coat, Throat Spray, HP Up, Protein, Iron, Carbos, Calcium, Zinc, PP Up, PP Max, Upgrade, Dubious Disc, and Loaded Dice.
+- The following items can now be placed on various surfaces:
+  - Galarica Wreath, Magnet, Flame Orb, Life Orb, Toxic Orb, Light Ball, and Smoke Ball.
+- The following items can now be placed as blocks, and have additional functionality:
+  - Ring Target, Metronome, and Eject Button.
+- The following items can now be worn by Players and Pokémon:
+  - Galarica Wreath, Cleanse Tag, Spell Tag, Sharp Beak, Covert Cloak, Shell Helmet, and Never-Melt Ice.
+- Wearable items can now be equipped by a player by holding it and right-clicking (or rebound use/interact)
+  - Wearable items that can be placed down are exempt from this behaviour.
+
+### New rideable Pokémon
+
+### Pokémon Added
+
+#### Regional Forms
+
+### Model updates for the following Pokémon
 
 ### Animation updates for the following Pokémon
-- Flapple, Appletun, Dipplin, Hydrapple (placeholder animations only).
+
+#### Added sounds to the following moves
+
+### Changes
 
 ### Fixes
-- Fixed a potential world generation stall caused by Type Gem clusters.
-- Fixed Pokémon on shoulders not animating if they are visibly holding a held item.
-- Fixed NPCs getting their own TM progress file.
-- Fixed odd NeoForge crash due to a dependency being outdated. It will now correctly flag the dependency for being outdated.
-- Fixed the TM Machine refusing move selections that the `unlockAllMoveDexMovesByDefault` config had made visible, leaving the move slot blank and the craft button unresponsive.
-- Fixed the Beast Ball not applying its 0.1× penalty to Pokémon that are not Ultra Beasts.
-- Fixed the Moon Ball reading the world's total elapsed time instead of the time of day, so its bonus applied during the day instead.
-- Fixed the Love Ball never awarding its 2.5× opposite gender bonus, and matching species by display name instead of identifier.
-- Fixed the Timer Ball being weaker than a regular Poké Ball on early turns and only reaching 4× on turn 14 instead of turn 10.
-- Fixed the Luxury Ball only doubling Friendship gains of 1, leaving level up and berry gains unaffected.
-- Fixed Rufflet, Braviary, and Hisuian Braviary flooding logs with errors about missing sound events.
-- Fixed Pokémon property typos in Pangoro and Dedenne herd spawn files.
-- Fixed unintentional watermelon cosmetic for Hisuian Electrode. 
-- Fixed Blastoise having an unintentional passenger seat.
-- Fixed form typo in Rockruff-Dusk spawn, preventing it from being able to spawn.
-- Fixed the `stat_compare` and `stat_equal` evolution requirements crashing the game when given `special_attack` or `special_defence`, and made them treat any non-permanent stat as a failed requirement instead of crashing.
-- Fixed Rowap and Jacoba berries not correctly altering Pokémon sizes when used as bait.
-- Fixed Ampharos' eyes not emitting particles.
-- Fixed Alolan Raticate's cry not playing.
-- Fixed several incorrect light-based spawning conditions for ghosts and bugs. 
-- Removed unused, placeholder habitat pools.
-- Fixed Mantyke, Mantine, and Quaxly getting stuck in a recoil 'expression' during battles due to having an expression assigned as a recoil animation. 
-- Fixed Lucario's aura particles not emitting.
-- Fixed Lycanroc's head movement.
-- Added head movement to Archaludon.
-- Fixed Duraludon line not having their sleep animations.
-- Fixed Diglett line not having their faint animations.
-- Fixed Kingambit moving its legs while walking.
+- Correctly grants "They're Minerals!" advancement when planting a type gem
+- Type Gem Blocks now have advancements to give you the recipe in the recipe book (the data for the advancements were inside the recipes somehow??)
+- Corrected the TM Recipes for Charge Beam and Payday
+
+### Developer
+
+### Molang & Datapacks
+
+### Particles
+
+#### New Move Animations
 
 ### Localization
-- Updated translations for:
-  - Brazilian Portuguese
-  - Simplified Chinese
-  - Japanese
+- Updated translations for:

changelogs/CHANGELOG-1.8.1.md

@@ -0,0 +1,41 @@
+# Changelog
+## [1.8.1 (September 13th, 2026)](#1-8-1)
+
+### Animation updates for the following Pokémon
+- Flapple, Appletun, Dipplin, Hydrapple (placeholder animations only).
+
+### Fixes
+- Fixed a potential world generation stall caused by Type Gem clusters.
+- Fixed Pokémon on shoulders not animating if they are visibly holding a held item.
+- Fixed NPCs getting their own TM progress file.
+- Fixed odd NeoForge crash due to a dependency being outdated. It will now correctly flag the dependency for being outdated.
+- Fixed the TM Machine refusing move selections that the `unlockAllMoveDexMovesByDefault` config had made visible, leaving the move slot blank and the craft button unresponsive.
+- Fixed the Beast Ball not applying its 0.1× penalty to Pokémon that are not Ultra Beasts.
+- Fixed the Moon Ball reading the world's total elapsed time instead of the time of day, so its bonus applied during the day instead.
+- Fixed the Love Ball never awarding its 2.5× opposite gender bonus, and matching species by display name instead of identifier.
+- Fixed the Timer Ball being weaker than a regular Poké Ball on early turns and only reaching 4× on turn 14 instead of turn 10.
+- Fixed the Luxury Ball only doubling Friendship gains of 1, leaving level up and berry gains unaffected.
+- Fixed Rufflet, Braviary, and Hisuian Braviary flooding logs with errors about missing sound events.
+- Fixed Pokémon property typos in Pangoro and Dedenne herd spawn files.
+- Fixed unintentional watermelon cosmetic for Hisuian Electrode. 
+- Fixed Blastoise having an unintentional passenger seat.
+- Fixed form typo in Rockruff-Dusk spawn, preventing it from being able to spawn.
+- Fixed the `stat_compare` and `stat_equal` evolution requirements crashing the game when given `special_attack` or `special_defence`, and made them treat any non-permanent stat as a failed requirement instead of crashing.
+- Fixed Rowap and Jacoba berries not correctly altering Pokémon sizes when used as bait.
+- Fixed Ampharos' eyes not emitting particles.
+- Fixed Alolan Raticate's cry not playing.
+- Fixed several incorrect light-based spawning conditions for ghosts and bugs. 
+- Removed unused, placeholder habitat pools.
+- Fixed Mantyke, Mantine, and Quaxly getting stuck in a recoil 'expression' during battles due to having an expression assigned as a recoil animation. 
+- Fixed Lucario's aura particles not emitting.
+- Fixed Lycanroc's head movement.
+- Added head movement to Archaludon.
+- Fixed Duraludon line not having their sleep animations.
+- Fixed Diglett line not having their faint animations.
+- Fixed Kingambit moving its legs while walking.
+
+### Localization
+- Updated translations for:
+  - Brazilian Portuguese
+  - Simplified Chinese
+  - Japanese

common/build.gradle.kts

@@ -1,9 +1,9 @@
 
+import utilities.isSnapshot
+import utilities.version
 import java.time.OffsetDateTime
 import java.time.ZoneOffset
 import java.time.format.DateTimeFormatter
-import utilities.isSnapshot
-import utilities.version
 
 /*
  *
@@ -66,6 +66,8 @@ dependencies {
 
 tasks.withType<Test> {
     useJUnitPlatform()
+    // Static GL mocks must not load a graphics driver on headless CI.
+    systemProperty("org.lwjgl.opengl.explicitInit", "true")
     testLogging {
         setEvents(listOf("failed"))
         setExceptionFormat("full")

common/src/main/java/com/cobblemon/mod/common/mixin/LivingEntityMixin.java

@@ -8,6 +8,7 @@
 
 package com.cobblemon.mod.common.mixin;
 
+import com.cobblemon.mod.common.CobblemonNetwork;
 import com.cobblemon.mod.common.OrientationControllable;
 import com.cobblemon.mod.common.api.orientation.OrientationController;
 import com.cobblemon.mod.common.api.pokemon.effect.ShoulderEffectRegistry;
@@ -17,6 +18,7 @@ import com.cobblemon.mod.common.api.riding.behaviour.types.liquid.SubmarineBehav
 import com.cobblemon.mod.common.client.entity.PokemonClientDelegate;
 import com.cobblemon.mod.common.client.render.MatrixWrapper;
 import com.cobblemon.mod.common.entity.pokemon.PokemonEntity;
+import com.cobblemon.mod.common.net.messages.server.orientation.ServerboundUpdateOrientationPacket;
 import com.llamalad7.mixinextras.injector.wrapoperation.Operation;
 import com.llamalad7.mixinextras.injector.wrapoperation.WrapOperation;
 import net.minecraft.server.level.ServerPlayer;

common/src/main/java/com/cobblemon/mod/common/mixin/accessor/RecipeBookComponentAccessor.java

@@ -10,7 +10,9 @@ package com.cobblemon.mod.common.mixin.accessor;
 
 import net.minecraft.client.gui.components.StateSwitchingButton;
 import net.minecraft.client.gui.screens.recipebook.RecipeBookComponent;
+import net.minecraft.network.chat.Component;
 import org.spongepowered.asm.mixin.Mixin;
+import org.spongepowered.asm.mixin.Mutable;
 import org.spongepowered.asm.mixin.gen.Accessor;
 
 @Mixin(RecipeBookComponent.class)

common/src/main/java/com/cobblemon/mod/common/mixin/brewing/BrewingStandBlockEntityMixin.java

@@ -15,9 +15,11 @@ import com.llamalad7.mixinextras.injector.wrapoperation.Operation;
 import com.llamalad7.mixinextras.injector.wrapoperation.WrapOperation;
 import com.llamalad7.mixinextras.sugar.Local;
 import net.minecraft.core.BlockPos;
+import net.minecraft.core.Direction;
 import net.minecraft.core.NonNullList;
 import net.minecraft.world.Containers;
 import net.minecraft.world.item.ItemStack;
+import net.minecraft.world.item.Items;
 import net.minecraft.world.item.alchemy.PotionBrewing;
 import net.minecraft.world.item.crafting.RecipeHolder;
 import net.minecraft.world.item.crafting.RecipeManager;
@@ -32,7 +34,6 @@ import org.spongepowered.asm.mixin.injection.callback.CallbackInfoReturnable;
 
 import java.util.List;
 import java.util.Optional;
-
 @Mixin(BrewingStandBlockEntity.class)
 public class BrewingStandBlockEntityMixin {
 

common/src/main/java/com/cobblemon/mod/common/mixin/brewing/BrewingStandMenuMixin.java

@@ -9,11 +9,17 @@
 package com.cobblemon.mod.common.mixin.brewing;
 
 import com.cobblemon.mod.common.duck.RecipeAwareSlot;
+import com.cobblemon.mod.common.item.crafting.brewingstand.BrewingStandRecipe;
+import com.llamalad7.mixinextras.injector.wrapoperation.Operation;
+import com.llamalad7.mixinextras.injector.wrapoperation.WrapOperation;
+import com.llamalad7.mixinextras.sugar.Local;
 import net.minecraft.world.Container;
 import net.minecraft.world.entity.player.Inventory;
+import net.minecraft.world.entity.player.Player;
 import net.minecraft.world.inventory.BrewingStandMenu;
 import net.minecraft.world.inventory.ContainerData;
 import net.minecraft.world.inventory.Slot;
+import net.minecraft.world.item.ItemStack;
 import org.spongepowered.asm.mixin.Mixin;
 import org.spongepowered.asm.mixin.injection.At;
 import org.spongepowered.asm.mixin.injection.Inject;

common/src/main/java/com/cobblemon/mod/common/mixin/brewing/PotionSlotMixin.java

@@ -13,6 +13,7 @@ import com.cobblemon.mod.common.item.crafting.brewingstand.BrewingStandRecipe;
 import net.minecraft.world.inventory.BrewingStandMenu;
 import net.minecraft.world.item.ItemStack;
 import net.minecraft.world.item.crafting.RecipeManager;
+import net.minecraft.world.level.Level;
 import org.spongepowered.asm.mixin.Mixin;
 import org.spongepowered.asm.mixin.Unique;
 import org.spongepowered.asm.mixin.injection.At;

common/src/main/java/com/cobblemon/mod/common/mixin/client/CameraMixin.java

@@ -19,6 +19,7 @@ import net.minecraft.client.Camera;
 import net.minecraft.world.entity.Entity;
 import net.minecraft.world.level.BlockGetter;
 import net.minecraft.world.phys.Vec3;
+import org.joml.Quaternionf;
 import org.joml.Vector3f;
 import org.spongepowered.asm.mixin.Final;
 import org.spongepowered.asm.mixin.Mixin;

common/src/main/java/com/cobblemon/mod/common/mixin/client/ClientRecipeBookMixin.java

@@ -10,7 +10,9 @@ package com.cobblemon.mod.common.mixin.client;
 
 import com.cobblemon.mod.common.CobblemonRecipeCategories;
 import com.cobblemon.mod.common.item.crafting.CookingPotBookCategory;
+import com.cobblemon.mod.common.item.crafting.CookingPotRecipe;
 import com.cobblemon.mod.common.item.crafting.CookingPotRecipeBase;
+import com.cobblemon.mod.common.item.crafting.CookingPotShapelessRecipe;
 import com.google.common.collect.ImmutableList;
 import com.google.common.collect.ImmutableMap;
 import com.google.common.collect.Maps;

common/src/main/java/com/cobblemon/mod/common/mixin/client/RenderStateShardMixin.java

@@ -0,0 +1,30 @@
+/*
+ * Copyright (C) 2023 Cobblemon Contributors
+ *
+ * This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at https://mozilla.org/MPL/2.0/.
+ */
+
+package com.cobblemon.mod.common.mixin.client;
+
+import com.cobblemon.mod.common.client.render.RenderAlphaScope;
+import net.minecraft.client.renderer.RenderStateShard;
+import net.minecraft.client.renderer.RenderType;
+import org.spongepowered.asm.mixin.Mixin;
+import org.spongepowered.asm.mixin.injection.At;
+import org.spongepowered.asm.mixin.injection.Inject;
+import org.spongepowered.asm.mixin.injection.callback.CallbackInfo;
+
+@Mixin(RenderStateShard.class)
+public abstract class RenderStateShardMixin {
+    @Inject(method = "setupRenderState", at = @At("RETURN"))
+    private void cobblemon$applyScopedAlpha(CallbackInfo ci) {
+        if ((Object) this instanceof RenderType) RenderAlphaScope.afterMaterialSetup();
+    }
+
+    @Inject(method = "clearRenderState", at = @At("RETURN"))
+    private void cobblemon$restoreScopedAlpha(CallbackInfo ci) {
+        if ((Object) this instanceof RenderType) RenderAlphaScope.afterMaterialClear();
+    }
+}

common/src/main/kotlin/com/cobblemon/mod/common/Cobblemon.kt

@@ -22,6 +22,8 @@ import com.cobblemon.mod.common.api.habitats.HabitatPools
 import com.cobblemon.mod.common.api.interaction.RequestManager
 import com.cobblemon.mod.common.api.molang.MoLangLoadedFilesCache
 import com.cobblemon.mod.common.api.molang.ObjectValue
+import com.cobblemon.mod.common.api.molangui.MolangUiActionRegistry
+import com.cobblemon.mod.common.api.molangui.MolangUiService
 import com.cobblemon.mod.common.api.permission.PermissionValidator
 import com.cobblemon.mod.common.api.pokeball.catching.calculators.CaptureCalculator
 import com.cobblemon.mod.common.api.pokeball.catching.calculators.CaptureCalculators
@@ -69,6 +71,7 @@ import com.cobblemon.mod.common.api.storage.player.adapter.TMMoveNbtBackend
 import com.cobblemon.mod.common.api.storage.player.factory.CachedPlayerDataStoreFactory
 import com.cobblemon.mod.common.api.tags.CobblemonEntityTypeTags
 import com.cobblemon.mod.common.api.tags.CobblemonItemTags
+import com.cobblemon.mod.common.api.vending.VendingMachinePageHandler
 import com.cobblemon.mod.common.battles.BagItems
 import com.cobblemon.mod.common.battles.BattleFormat
 import com.cobblemon.mod.common.battles.BattleRegistry
@@ -97,10 +100,10 @@ import com.cobblemon.mod.common.pokemon.Pokemon
 import com.cobblemon.mod.common.pokemon.aspects.ALPHA_ASPECT
 import com.cobblemon.mod.common.pokemon.aspects.CHARACTERISTIC_RAINBOW_ASPECT
 import com.cobblemon.mod.common.pokemon.aspects.COSMETIC_SLOT_ASPECT
-import com.cobblemon.mod.common.pokemon.aspects.FORM_ASPECTS
 import com.cobblemon.mod.common.pokemon.aspects.GENDER_ASPECT
 import com.cobblemon.mod.common.pokemon.aspects.MARK_ASPECT
 import com.cobblemon.mod.common.pokemon.aspects.SHINY_ASPECT
+import com.cobblemon.mod.common.pokemon.evolution.variants.BlockClickEvolution
 import com.cobblemon.mod.common.pokemon.feature.SlowpokeTailRegrowthSpeciesFeature
 import com.cobblemon.mod.common.pokemon.feature.SlowpokeTailRegrowthSpeciesFeatureProvider
 import com.cobblemon.mod.common.pokemon.feature.TagSeasonResolver
@@ -115,7 +118,6 @@ import com.cobblemon.mod.common.pokemon.properties.NoAIProperty
 import com.cobblemon.mod.common.pokemon.properties.UnaspectPropertyType
 import com.cobblemon.mod.common.pokemon.properties.UncatchableProperty
 import com.cobblemon.mod.common.pokemon.stat.CobblemonStatProvider
-import com.cobblemon.mod.common.pokemon.transformation.triggers.BlockClickTrigger
 import com.cobblemon.mod.common.starter.CobblemonStarterHandler
 import com.cobblemon.mod.common.util.*
 import com.cobblemon.mod.common.world.feature.CobblemonPlacedFeatures
@@ -260,6 +262,7 @@ object Cobblemon {
             playerDataManager.onPlayerDisconnect(it.player)
             RequestManager.onLogoff(it.player)
             serverPlayerStructs.remove(it.player.uuid)
+            MolangUiService.closeAllForPlayer(it.player.uuid)
         }
         PlatformEvents.PLAYER_DEATH.subscribe {
             PCLinkManager.removeLink(it.player.uuid)
@@ -274,8 +277,13 @@ object Cobblemon {
         PlatformEvents.RIGHT_CLICK_BLOCK.subscribe { event ->
             val player = event.player
             val block = player.level().getBlockState(event.pos).block
-            val context = BlockClickTrigger.Context(block, player.level())
-            player.party().forEach { pokemon -> pokemon.triggerTransformations<BlockClickTrigger>(context) }
+            player.party().forEach { pokemon ->
+                pokemon.lockedEvolutions
+                    .filterIsInstance<BlockClickEvolution>()
+                    .forEach { evolution ->
+                        evolution.attemptEvolution(pokemon, BlockClickEvolution.BlockInteractionContext(block, player.level()))
+                    }
+            }
         }
 
         PlatformEvents.CHANGE_DIMENSION.subscribe {
@@ -317,9 +325,13 @@ object Cobblemon {
         // Start up the data provider.
         CobblemonDataProvider.registerDefaults()
 
+        MolangUiActionRegistry.register(
+            VendingMachinePageHandler.ACTION,
+            VendingMachinePageHandler
+        )
+
         SHINY_ASPECT.register()
         GENDER_ASPECT.register()
-        FORM_ASPECTS.register()
         COSMETIC_SLOT_ASPECT.register()
         CHARACTERISTIC_RAINBOW_ASPECT.register()
         ALPHA_ASPECT.register()
@@ -447,6 +459,7 @@ object Cobblemon {
         }
 
         PlatformEvents.SERVER_STOPPED.subscribe {
+            MolangUiService.closeAll()
             storage.unregisterAll(it.server.registryAccess())
             playerDataManager.saveAllStores()
             playerDataManager.saveExecutor.shutdown()

common/src/main/kotlin/com/cobblemon/mod/common/CobblemonBehaviours.kt

@@ -9,7 +9,6 @@
 package com.cobblemon.mod.common
 
 import com.bedrockk.molang.Expression
-import com.cobblemon.mod.common.CobblemonBehaviours.autoPokemonBehaviours
 import com.cobblemon.mod.common.CobblemonNetwork.sendPacket
 import com.cobblemon.mod.common.api.ai.CobblemonBehaviour
 import com.cobblemon.mod.common.api.ai.config.BehaviourConfig
@@ -20,7 +19,16 @@ import com.cobblemon.mod.common.api.molang.ExpressionLike
 import com.cobblemon.mod.common.api.npc.configuration.MoLangConfigVariable
 import com.cobblemon.mod.common.api.reactive.SimpleObservable
 import com.cobblemon.mod.common.net.messages.client.data.BehaviourSyncPacket
-import com.cobblemon.mod.common.util.adapters.*
+import com.cobblemon.mod.common.util.adapters.ActivityAdapter
+import com.cobblemon.mod.common.util.adapters.BehaviourConfigAdapter
+import com.cobblemon.mod.common.util.adapters.ExpressionAdapter
+import com.cobblemon.mod.common.util.adapters.ExpressionLikeAdapter
+import com.cobblemon.mod.common.util.adapters.ExpressionOrEntityVariableAdapter
+import com.cobblemon.mod.common.util.adapters.IdentifierAdapter
+import com.cobblemon.mod.common.util.adapters.MemoryModuleTypeAdapter
+import com.cobblemon.mod.common.util.adapters.SensorTypeAdapter
+import com.cobblemon.mod.common.util.adapters.TaskConfigAdapter
+import com.cobblemon.mod.common.util.adapters.TranslatedTextAdapter
 import com.cobblemon.mod.common.util.cobblemonResource
 import com.cobblemon.mod.common.util.endsWith
 import com.google.gson.Gson

common/src/main/kotlin/com/cobblemon/mod/common/CobblemonBlocks.kt

@@ -16,6 +16,8 @@ import com.cobblemon.mod.common.block.MintBlock.MintType
 import com.cobblemon.mod.common.block.campfirepot.CampfireBlock
 import com.cobblemon.mod.common.block.campfirepot.CampfirePotBlock
 import com.cobblemon.mod.common.block.chest.GildedChestBlock
+import com.cobblemon.mod.common.block.decor.ActivatableDecorationBlock
+import com.cobblemon.mod.common.block.decor.RingTargetBlock
 import com.cobblemon.mod.common.block.general.BaleBlock
 import com.cobblemon.mod.common.block.general.HorizontalRotationCarpetBlock
 import com.cobblemon.mod.common.block.general.HorizontalRotationalBlock
@@ -620,6 +622,88 @@ object CobblemonBlocks : PlatformRegistry<Registry<Block>, ResourceKey<Registry<
     @JvmField
     val WEAKNESS_POLICY = create("weakness_policy", WallAttachedDirectionalShapeBlock(BlockBehaviour.Properties.of().sound(CobblemonSounds.ITEM_BLOCK_PAPER_LARGE_SOUNDS).mapColor(MapColor.NONE).noOcclusion().noCollission(), 14, 12, 1))
 
+    @JvmField
+    val RING_TARGET = create("ring_target", RingTargetBlock(BlockBehaviour.Properties.of().sound(SoundType.WOOD).mapColor(MapColor.NONE).noOcclusion().strength(0.125f)))
+    @JvmField
+    val MAGNET = create("magnet", MagnetBlock(BlockBehaviour.Properties.of().sound(SoundType.METAL).mapColor(MapColor.NONE).noOcclusion().strength(0.075f)))
+    @JvmField
+    val GALARICA_WREATH = create("galarica_wreath", GalaricaWreathBlock(BlockBehaviour.Properties.of().sound(SoundType.AZALEA_LEAVES).mapColor(MapColor.NONE).noOcclusion().noCollission()))
+
+    @JvmField
+    val FLAME_ORB = create("flame_orb", OrbBlock(BlockBehaviour.Properties.of().sound(SoundType.GLASS).mapColor(MapColor.NONE).noOcclusion().lightLevel{15}))
+    @JvmField
+    val TOXIC_ORB = create("toxic_orb", OrbBlock(BlockBehaviour.Properties.of().sound(SoundType.GLASS).mapColor(MapColor.NONE).noOcclusion()))
+    @JvmField
+    val LIFE_ORB = create("life_orb", OrbBlock(BlockBehaviour.Properties.of().sound(SoundType.GLASS).mapColor(MapColor.NONE).noOcclusion().lightLevel{7}))
+    @JvmField
+    val LIGHT_BALL = create("light_ball", OrbBlock(BlockBehaviour.Properties.of().sound(SoundType.GLASS).mapColor(MapColor.NONE).noOcclusion().lightLevel{13}))
+    @JvmField
+    val SMOKE_BALL = create("smoke_ball", OrbBlock(BlockBehaviour.Properties.of().sound(SoundType.GLASS).mapColor(MapColor.NONE).noOcclusion()))
+
+    @JvmField
+    val KINGS_ROCK = create("kings_rock", DecorativeItemBlock(BlockBehaviour.Properties.of().sound(CobblemonSounds.TUMBLESTONE_BLOCK_SOUNDS).mapColor(MapColor.NONE).noOcclusion(), DecorativeItemBlock.DecorativeItemBlockType.CENTERED_6x))
+
+    @JvmField
+    val GALARICA_CUFF = create("galarica_cuff", DecorativeItemBlock(BlockBehaviour.Properties.of().sound(SoundType.AZALEA_LEAVES).mapColor(MapColor.NONE).noCollission().noOcclusion(), DecorativeItemBlock.DecorativeItemBlockType.FLATTENED_10x4))
+    @JvmField
+    val UNREMARKABLE_TEACUP = create("unremarkable_teacup", DecorativeItemBlock(BlockBehaviour.Properties.of().sound(SoundType.DECORATED_POT).mapColor(MapColor.NONE).noOcclusion(), DecorativeItemBlock.DecorativeItemBlockType.TEACUP))
+    @JvmField
+    val MASTERPIECE_TEACUP = create("masterpiece_teacup", DecorativeItemBlock(BlockBehaviour.Properties.of().sound(SoundType.DECORATED_POT).mapColor(MapColor.NONE).noOcclusion(), DecorativeItemBlock.DecorativeItemBlockType.TEACUP))
+    @JvmField
+    val CHIPPED_POT = create("chipped_pot", DecorativeItemBlock(BlockBehaviour.Properties.of().sound(SoundType.DECORATED_POT).mapColor(MapColor.NONE).noOcclusion(), DecorativeItemBlock.DecorativeItemBlockType.TEAPOT))
+    @JvmField
+    val CRACKED_POT = create("cracked_pot", DecorativeItemBlock(BlockBehaviour.Properties.of().sound(SoundType.DECORATED_POT).mapColor(MapColor.NONE).noOcclusion(), DecorativeItemBlock.DecorativeItemBlockType.TEAPOT))
+
+    @JvmField
+    val SACHET = create("sachet", DecorativeItemBlock(BlockBehaviour.Properties.of().sound(SoundType.WOOL).mapColor(MapColor.NONE).noOcclusion(), DecorativeItemBlock.DecorativeItemBlockType.POUCH))
+    @JvmField
+    val METAL_POWDER = create("metal_powder", DecorativeItemBlock(BlockBehaviour.Properties.of().sound(SoundType.WOOL).mapColor(MapColor.NONE).noOcclusion(), DecorativeItemBlock.DecorativeItemBlockType.POUCH))
+    @JvmField
+    val QUICK_POWDER = create("quick_powder", DecorativeItemBlock(BlockBehaviour.Properties.of().sound(SoundType.WOOL).mapColor(MapColor.NONE).noOcclusion(), DecorativeItemBlock.DecorativeItemBlockType.POUCH))
+    @JvmField
+    val BRIGHT_POWDER = create("bright_powder", DecorativeItemBlock(BlockBehaviour.Properties.of().sound(SoundType.WOOL).mapColor(MapColor.NONE).noOcclusion().lightLevel{3}, DecorativeItemBlock.DecorativeItemBlockType.POUCH))
+
+    @JvmField
+    val NEVER_MELT_ICE = create("never_melt_ice", DecorativeItemBlock(BlockBehaviour.Properties.of().sound(SoundType.GLASS).mapColor(MapColor.NONE).noOcclusion().friction(0.989F), DecorativeItemBlock.DecorativeItemBlockType.NEVERMELT))
+    @JvmField
+    val SCOPE_LENS = create("scope_lens", DecorativeItemBlock(BlockBehaviour.Properties.of().sound(SoundType.COPPER).mapColor(MapColor.NONE).noOcclusion(), DecorativeItemBlock.DecorativeItemBlockType.SCOPE))
+    @JvmField
+    val WIDE_LENS = create("wide_lens", DecorativeItemBlock(BlockBehaviour.Properties.of().sound(SoundType.COPPER).mapColor(MapColor.NONE).noOcclusion(), DecorativeItemBlock.DecorativeItemBlockType.WIDE))
+    @JvmField
+    val ZOOM_LENS = create("zoom_lens", DecorativeItemBlock(BlockBehaviour.Properties.of().sound(SoundType.COPPER).mapColor(MapColor.NONE).noOcclusion(), DecorativeItemBlock.DecorativeItemBlockType.ZOOM))
+
+    @JvmField
+    val ICY_ROCK = create("icy_rock", DecorativeItemBlock(BlockBehaviour.Properties.of().sound(SoundType.DEEPSLATE).mapColor(MapColor.NONE).noOcclusion(), DecorativeItemBlock.DecorativeItemBlockType.FLATTENED_8x4))
+    @JvmField
+    val HEAT_ROCK = create("heat_rock", DecorativeItemBlock(BlockBehaviour.Properties.of().sound(SoundType.DEEPSLATE).mapColor(MapColor.NONE).noOcclusion(), DecorativeItemBlock.DecorativeItemBlockType.FLATTENED_8x4))
+    @JvmField
+    val SMOOTH_ROCK = create("smooth_rock", DecorativeItemBlock(BlockBehaviour.Properties.of().sound(SoundType.DEEPSLATE).mapColor(MapColor.NONE).noOcclusion(), DecorativeItemBlock.DecorativeItemBlockType.FLATTENED_8x4))
+    @JvmField
+    val DAMP_ROCK = create("damp_rock", DecorativeItemBlock(BlockBehaviour.Properties.of().sound(SoundType.DEEPSLATE).mapColor(MapColor.NONE).noOcclusion(), DecorativeItemBlock.DecorativeItemBlockType.FLATTENED_8x6))
+    @JvmField
+    val DESTINY_KNOT = create("destiny_knot", DecorativeItemBlock(BlockBehaviour.Properties.of().sound(SoundType.WOOL).mapColor(MapColor.NONE).noOcclusion(), DecorativeItemBlock.DecorativeItemBlockType.KNOT))
+    @JvmField
+    val LUMINOUS_MOSS = create("luminous_moss", DecorativeItemBlock(BlockBehaviour.Properties.of().sound(SoundType.MOSS).mapColor(MapColor.NONE).noOcclusion().lightLevel{5}, DecorativeItemBlock.DecorativeItemBlockType.CENTERED_8x))
+
+    @JvmField
+    val METRONOME = create("metronome", ActivatableDecorationBlock(BlockBehaviour.Properties.of().sound(SoundType.METAL).mapColor(MapColor.NONE).pushReaction(PushReaction.DESTROY).noOcclusion(), ActivatableDecorationBlock.ActivatableDecorationBlockType.METRONOME))
+    @JvmField
+    val EJECT_BUTTON = create("eject_button", EjectButtonBlock(BlockBehaviour.Properties.of().sound(SoundType.METAL).mapColor(MapColor.NONE).pushReaction(PushReaction.DESTROY).noOcclusion().strength(0.125f), 40))
+
+    @JvmField
+    val LOADED_DICE = create("loaded_dice", StackableItemBlock(BlockBehaviour.Properties.of().sound(SoundType.CANDLE).mapColor(MapColor.NONE).noOcclusion(), StackableItemBlock.StackableItemBlockType.DICE))
+    @JvmField
+    val IRON_BALL = create("iron_ball", StackableItemBlock(BlockBehaviour.Properties.of().sound(SoundType.METAL).mapColor(MapColor.NONE).noOcclusion(), StackableItemBlock.StackableItemBlockType.IRON_BALL))
+    @JvmField
+    val METAL_COAT = create("metal_coat", StackableItemBlock(BlockBehaviour.Properties.of().sound(SoundType.METAL).mapColor(MapColor.NONE).noOcclusion(), StackableItemBlock.StackableItemBlockType.METAL_COAT))
+    @JvmField
+    val UPGRADE = create("upgrade", StackableItemBlock(BlockBehaviour.Properties.of().sound(SoundType.CANDLE).mapColor(MapColor.NONE).noOcclusion(), StackableItemBlock.StackableItemBlockType.UPGRADE))
+    @JvmField
+    val DUBIOUS_DISC = create("dubious_disc", StackableItemBlock(BlockBehaviour.Properties.of().sound(SoundType.CANDLE).mapColor(MapColor.NONE).noOcclusion(), StackableItemBlock.StackableItemBlockType.UPGRADE))
+
+    @JvmField
+    val THROAT_SPRAY = create("throat_spray", StackableItemBlock(BlockBehaviour.Properties.of().sound(SoundType.CANDLE).mapColor(MapColor.NONE).noOcclusion(), StackableItemBlock.StackableItemBlockType.THROAT_SPRAY))
+
     @JvmField
     val FULL_HEAL = create("full_heal", StackableItemBlock(BlockBehaviour.Properties.of().sound(SoundType.CANDLE).mapColor(MapColor.NONE).noOcclusion(), StackableItemBlock.StackableItemBlockType.STATUS_RESTORE))
     @JvmField
@@ -670,6 +754,23 @@ object CobblemonBlocks : PlatformRegistry<Registry<Block>, ResourceKey<Registry<
     @JvmField
     val X_SPEED = create("x_${Stats.SPEED.identifier.path}", StackableItemBlock(BlockBehaviour.Properties.of().sound(SoundType.CANDLE).mapColor(MapColor.NONE).noOcclusion(), StackableItemBlock.StackableItemBlockType.BATTLE_ITEM))
 
+    @JvmField
+    val HP_UP = create("hp_up", StackableItemBlock(BlockBehaviour.Properties.of().sound(SoundType.CANDLE).mapColor(MapColor.NONE).noOcclusion(), StackableItemBlock.StackableItemBlockType.VITAMIN))
+    @JvmField
+    val PROTEIN = create("protein", StackableItemBlock(BlockBehaviour.Properties.of().sound(SoundType.CANDLE).mapColor(MapColor.NONE).noOcclusion(), StackableItemBlock.StackableItemBlockType.VITAMIN))
+    @JvmField
+    val IRON = create("iron", StackableItemBlock(BlockBehaviour.Properties.of().sound(SoundType.CANDLE).mapColor(MapColor.NONE).noOcclusion(), StackableItemBlock.StackableItemBlockType.VITAMIN))
+    @JvmField
+    val CARBOS = create("carbos", StackableItemBlock(BlockBehaviour.Properties.of().sound(SoundType.CANDLE).mapColor(MapColor.NONE).noOcclusion(), StackableItemBlock.StackableItemBlockType.VITAMIN))
+    @JvmField
+    val CALCIUM = create("calcium", StackableItemBlock(BlockBehaviour.Properties.of().sound(SoundType.CANDLE).mapColor(MapColor.NONE).noOcclusion(), StackableItemBlock.StackableItemBlockType.VITAMIN))
+    @JvmField
+    val ZINC = create("zinc", StackableItemBlock(BlockBehaviour.Properties.of().sound(SoundType.CANDLE).mapColor(MapColor.NONE).noOcclusion(), StackableItemBlock.StackableItemBlockType.VITAMIN))
+    @JvmField
+    val PP_UP = create("pp_up", StackableItemBlock(BlockBehaviour.Properties.of().sound(SoundType.CANDLE).mapColor(MapColor.NONE).noOcclusion(), StackableItemBlock.StackableItemBlockType.VITAMIN))
+    @JvmField
+    val PP_MAX = create("pp_max", StackableItemBlock(BlockBehaviour.Properties.of().sound(SoundType.CANDLE).mapColor(MapColor.NONE).noOcclusion(), StackableItemBlock.StackableItemBlockType.VITAMIN))
+
     @JvmField
     val MONITOR = create("monitor", MonitorBlock(BlockBehaviour.Properties.of().mapColor(MapColor.METAL).sound(SoundType.METAL).pushReaction(PushReaction.BLOCK).requiresCorrectToolForDrops().strength(5.0F, 6.0F).lightLevel { if (it.getValue(MonitorBlock.SCREEN) != MonitorBlock.MonitorScreen.OFF) 13 else 0 }))
     @JvmField
@@ -707,6 +808,9 @@ object CobblemonBlocks : PlatformRegistry<Registry<Block>, ResourceKey<Registry<
     @JvmField
     val DISPLAY_CASE = create("display_case", DisplayCaseBlock(BlockBehaviour.Properties.of().sound(CobblemonSounds.DISPLAY_CASE_SOUNDS).noOcclusion().pushReaction(PushReaction.BLOCK).mapColor(MapColor.STONE).strength(0.3F).requiresCorrectToolForDrops()))
 
+    @JvmField
+    val VENDING_MACHINE = create("vending_machine", VendingMachineBlock(BlockBehaviour.Properties.of().mapColor(MapColor.METAL).sound(SoundType.METAL).pushReaction(PushReaction.BLOCK).strength(2F).requiresCorrectToolForDrops()))
+
     // TODO after 1.7
 //    @JvmField
 //    val INCENSE_SWEET = create("incense_sweet", SweetIncenseBlock(BlockBehaviour.Properties.of().sound(CobblemonSounds.DISPLAY_CASE_SOUNDS).noOcclusion().pushReaction(PushReaction.BLOCK).mapColor(MapColor.STONE).strength(0.3F)))

common/src/main/kotlin/com/cobblemon/mod/common/CobblemonCommands.kt

@@ -41,8 +41,6 @@ object CobblemonCommands {
         HeldItemCommand.register(dispatcher, registry)
         PcCommand.register(dispatcher)
         SpawnPokemonFromPool.register(dispatcher)
-        SpawnMeteorCommand.register(dispatcher)
-        SetMegaBondCommand.register(dispatcher)
         PokeboxCommand.register(dispatcher)
         PokedexCommand.register(dispatcher)
         TestStoreCommand.register(dispatcher)
@@ -79,5 +77,6 @@ object CobblemonCommands {
         // Possibly lock down registration if and only if under dev environment or running in an environment
         // with a certain system environment variable set
         CobblemonInfoCommand.register(dispatcher)
+        MolangUiCommand.register(dispatcher)
     }
 }

common/src/main/kotlin/com/cobblemon/mod/common/CobblemonEntities.kt

@@ -16,7 +16,6 @@ import com.cobblemon.mod.common.entity.generic.GenericBedrockEntity
 import com.cobblemon.mod.common.entity.npc.NPCEntity
 import com.cobblemon.mod.common.entity.pokeball.EmptyPokeBallEntity
 import com.cobblemon.mod.common.entity.pokemon.PokemonEntity
-import com.cobblemon.mod.common.entity.projectile.FallingStarEntity
 import com.cobblemon.mod.common.platform.PlatformRegistry
 import com.cobblemon.mod.common.util.cobblemonResource
 import net.minecraft.core.Registry
@@ -96,15 +95,6 @@ object CobblemonEntities : PlatformRegistry<Registry<EntityType<*>>, ResourceKey
         EntityType.Builder.of({ _, world -> NPCEntity(world) }, MobCategory.CREATURE).build("$NPC_KEY")
     )
 
-    @JvmField
-    val FALLING_STAR_KEY = cobblemonResource("falling_star")
-    @JvmField
-    val FALLING_STAR: EntityType<FallingStarEntity> = create(
-        FALLING_STAR_KEY.path,
-        EntityType.Builder.of(::FallingStarEntity, MobCategory.MISC).sized(0.5F, 0.5F).clientTrackingRange(8)
-            .build(FALLING_STAR_KEY.toString())
-    )
-
     fun registerAttributes(consumer: (EntityType<out LivingEntity>, AttributeSupplier.Builder) -> Unit) {
         consumer(POKEMON, PokemonEntity.createAttributes())
         consumer(NPC, NPCEntity.createAttributes())

common/src/main/kotlin/com/cobblemon/mod/common/CobblemonImplementation.kt

@@ -19,6 +19,7 @@ import net.minecraft.server.level.ServerPlayer
 import net.minecraft.server.packs.PackType
 import net.minecraft.server.packs.resources.PreparableReloadListener
 import net.minecraft.tags.TagKey
+import net.minecraft.world.inventory.MenuType
 import net.minecraft.world.level.GameRules
 import net.minecraft.world.level.ItemLike
 import net.minecraft.world.level.biome.Biome

common/src/main/kotlin/com/cobblemon/mod/common/CobblemonItemComponents.kt

@@ -33,12 +33,6 @@ object CobblemonItemComponents : PlatformRegistry<Registry<DataComponentType<*>>
         .networkSynchronized(HeldItemEffectComponent.PACKET_CODEC)
         .build())
 
-    @JvmField
-    val MEGA_BOND: DataComponentType<MegaBondComponent> = create("mega_bond", DataComponentType.builder<MegaBondComponent>()
-        .persistent(MegaBondComponent.CODEC)
-        .networkSynchronized(MegaBondComponent.PACKET_CODEC)
-        .build())
-
     @JvmField
     val BAIT: DataComponentType<RodBaitComponent> = create("bait", DataComponentType.builder<RodBaitComponent>()
         .persistent(RodBaitComponent.CODEC)

common/src/main/kotlin/com/cobblemon/mod/common/CobblemonItems.kt

@@ -465,6 +465,8 @@ object CobblemonItems : PlatformRegistry<Registry<Item>, ResourceKey<Registry<It
     val PASTURE = blockItem("pasture", CobblemonBlocks.PASTURE)
     @JvmField
     val DISPLAY_CASE = blockItem("display_case", CobblemonBlocks.DISPLAY_CASE)
+    @JvmField
+    val VENDING_MACHINE = blockItem("vending_machine", CobblemonBlocks.VENDING_MACHINE)
 //    @JvmField
 //    val INCENSE_SWEET = blockItem("incense_sweet", CobblemonBlocks.INCENSE_SWEET) // TODO after 1.7
 
@@ -472,9 +474,9 @@ object CobblemonItems : PlatformRegistry<Registry<Item>, ResourceKey<Registry<It
     // Evolution items
     @JvmField val LINK_CABLE = create("link_cable", LinkCableItem())
     @JvmField val DRAGON_SCALE = noSettingsItem("dragon_scale")
-    @JvmField val METAL_COAT = noSettingsItem("metal_coat")
-    @JvmField val UPGRADE = noSettingsItem("upgrade")
-    @JvmField val DUBIOUS_DISC = noSettingsItem("dubious_disc")
+    @JvmField val METAL_COAT = itemNameBlockItem("metal_coat", CobblemonBlocks.METAL_COAT)
+    @JvmField val UPGRADE = itemNameBlockItem("upgrade", CobblemonBlocks.UPGRADE)
+    @JvmField val DUBIOUS_DISC = itemNameBlockItem("dubious_disc", CobblemonBlocks.DUBIOUS_DISC)
     @JvmField val DEEP_SEA_SCALE = noSettingsItem("deep_sea_scale")
     @JvmField val DEEP_SEA_TOOTH = noSettingsItem("deep_sea_tooth")
     @JvmField val ELECTIRIZER = noSettingsItem("electirizer")
@@ -483,7 +485,7 @@ object CobblemonItems : PlatformRegistry<Registry<Item>, ResourceKey<Registry<It
     @JvmField val PROTECTOR = noSettingsItem("protector")
     @JvmField val REAPER_CLOTH = noSettingsItem("reaper_cloth")
     @JvmField val PRISM_SCALE = noSettingsItem("prism_scale")
-    @JvmField val SACHET = noSettingsItem("sachet")
+    @JvmField val SACHET = itemNameBlockItem("sachet", CobblemonBlocks.SACHET)
     @JvmField val WHIPPED_DREAM = create("whipped_dream", foodItem(8, 0.3f))
     @JvmField val STRAWBERRY_SWEET = create("strawberry_sweet", foodItem(6, 0.125f))
     @JvmField val LOVE_SWEET = create("love_sweet", foodItem(6, 0.125f))
@@ -492,22 +494,20 @@ object CobblemonItems : PlatformRegistry<Registry<Item>, ResourceKey<Registry<It
     @JvmField val FLOWER_SWEET = create("flower_sweet", foodItem(6, 0.125f))
     @JvmField val STAR_SWEET = create("star_sweet", foodItem(6, 0.125f))
     @JvmField val RIBBON_SWEET = create("ribbon_sweet", foodItem(6, 0.125f))
-    @JvmField val CHIPPED_POT = noSettingsItem("chipped_pot")
-    @JvmField val CRACKED_POT = noSettingsItem("cracked_pot")
-    @JvmField val MASTERPIECE_TEACUP = noSettingsItem("masterpiece_teacup")
-    @JvmField val UNREMARKABLE_TEACUP = noSettingsItem("unremarkable_teacup")
+    @JvmField val CHIPPED_POT = itemNameBlockItem("chipped_pot", CobblemonBlocks.CHIPPED_POT)
+    @JvmField val CRACKED_POT = itemNameBlockItem("cracked_pot", CobblemonBlocks.CRACKED_POT)
+    @JvmField val MASTERPIECE_TEACUP = itemNameBlockItem("masterpiece_teacup", CobblemonBlocks.MASTERPIECE_TEACUP)
+    @JvmField val UNREMARKABLE_TEACUP = itemNameBlockItem("unremarkable_teacup", CobblemonBlocks.UNREMARKABLE_TEACUP)
     @JvmField val SWEET_APPLE = compostableItem("sweet_apple", foodItem(4, 0.3f), 0.65f)
     @JvmField val TART_APPLE = compostableItem("tart_apple", foodItem(4, 0.3f), 0.65f)
     @JvmField val SYRUPY_APPLE = compostableItem("syrupy_apple", foodItem(4, 0.3f), 0.65f)
-    @JvmField val GALARICA_CUFF = noSettingsItem("galarica_cuff")
-    @JvmField val GALARICA_WREATH = noSettingsItem("galarica_wreath")
+    @JvmField val GALARICA_CUFF = itemNameBlockItem("galarica_cuff", CobblemonBlocks.GALARICA_CUFF)
     @JvmField val BLACK_AUGURITE = noSettingsItem("black_augurite")
     @JvmField val PEAT_BLOCK = noSettingsItem("peat_block")
     @JvmField val RAZOR_CLAW = noSettingsItem("razor_claw")
     @JvmField val RAZOR_FANG = noSettingsItem("razor_fang")
     @JvmField val AUSPICIOUS_ARMOR = heldItem("auspicious_armor")
     @JvmField val MALICIOUS_ARMOR = heldItem("malicious_armor")
-    @JvmField val SHELL_HELMET = heldItem("shell_helmet")
     @JvmField val METAL_ALLOY = noSettingsItem("metal_alloy")
     @JvmField val SCROLL_OF_DARKNESS = noSettingsItem("scroll_of_darkness")
     @JvmField val SCROLL_OF_WATERS = noSettingsItem("scroll_of_waters")
@@ -651,17 +651,17 @@ object CobblemonItems : PlatformRegistry<Registry<Item>, ResourceKey<Registry<It
     @JvmField
     val EXPERIENCE_CANDY_XL = candyItem("exp_candy_xl") { _, _ -> CandyItem.DEFAULT_XL_CANDY_YIELD }
     @JvmField
-    val CALCIUM = create("calcium", VitaminItem(Stats.SPECIAL_ATTACK))
+    val CALCIUM = create("calcium", VitaminItem(Stats.SPECIAL_ATTACK, CobblemonBlocks.CALCIUM))
     @JvmField
-    val CARBOS = create("carbos", VitaminItem(Stats.SPEED))
+    val CARBOS = create("carbos", VitaminItem(Stats.SPEED, CobblemonBlocks.CARBOS))
     @JvmField
-    val HP_UP = create("hp_up", VitaminItem(Stats.HP))
+    val HP_UP = create("hp_up", VitaminItem(Stats.HP, CobblemonBlocks.HP_UP))
     @JvmField
-    val IRON = create("iron", VitaminItem(Stats.DEFENCE))
+    val IRON = create("iron", VitaminItem(Stats.DEFENCE, CobblemonBlocks.IRON))
     @JvmField
-    val PROTEIN = create("protein", VitaminItem(Stats.ATTACK))
+    val PROTEIN = create("protein", VitaminItem(Stats.ATTACK, CobblemonBlocks.PROTEIN))
     @JvmField
-    val ZINC = create("zinc", VitaminItem(Stats.SPECIAL_DEFENCE))
+    val ZINC = create("zinc", VitaminItem(Stats.SPECIAL_DEFENCE, CobblemonBlocks.ZINC))
     @JvmField
     val HEALTH_MOCHI = create("health_mochi", MochiItem(Stats.HP))
     @JvmField
@@ -743,9 +743,9 @@ object CobblemonItems : PlatformRegistry<Registry<Item>, ResourceKey<Registry<It
     @JvmField
     val MAX_REVIVE = create("max_revive", ReviveItem(max = true))
     @JvmField
-    val PP_UP = create("pp_up", PPUpItem(1))
+    val PP_UP = create("pp_up", PPUpItem(1, CobblemonBlocks.PP_UP))
     @JvmField
-    val PP_MAX = create("pp_max", PPUpItem(3))
+    val PP_MAX = create("pp_max", PPUpItem(3, CobblemonBlocks.PP_MAX))
 
     @JvmField
     val RED_MINT_SEEDS = mintSeed("red", MintType.RED.getCropBlock())
@@ -914,10 +914,6 @@ object CobblemonItems : PlatformRegistry<Registry<Item>, ResourceKey<Registry<It
     val THUNDER_STONE = noSettingsItem("thunder_stone")
     @JvmField
     val WATER_STONE = noSettingsItem("water_stone")
-    @JvmField
-    val MEGA_SHARD = noSettingsItem("mega_shard")
-    @JvmField
-    val DORMANT_MEGA_STONE = heldItem("dormant_mega_stone")
 
     val wearables = mutableListOf<WearableItem>()
     //Wearable items (these items should have a corresponding 3D model)
@@ -926,44 +922,31 @@ object CobblemonItems : PlatformRegistry<Registry<Item>, ResourceKey<Registry<It
     @JvmField val CHOICE_SPECS = wearableItem("choice_specs")
     @JvmField val EXP_SHARE = wearableItem("exp_share")
     @JvmField val FOCUS_BAND = wearableItem("focus_band")
-    @JvmField val KINGS_ROCK = wearableItem("kings_rock")
+    @JvmField val KINGS_ROCK = wearableBlockItem("kings_rock", CobblemonBlocks.KINGS_ROCK)
+    @JvmField val NEVER_MELT_ICE = wearableBlockItem("never_melt_ice", CobblemonBlocks.NEVER_MELT_ICE)
     @JvmField val MUSCLE_BAND = wearableItem("muscle_band")
     @JvmField val ROCKY_HELMET = wearableItem("rocky_helmet")
     @JvmField val SAFETY_GOGGLES = wearableItem("safety_goggles")
     @JvmField val WISE_GLASSES = wearableItem("wise_glasses")
+    @JvmField val SHARP_BEAK = wearableItem("sharp_beak")
+    @JvmField val COVERT_CLOAK = wearableItem("covert_cloak")
+    @JvmField val SHELL_HELMET = wearableItem("shell_helmet")
+    @JvmField val GALARICA_WREATH = wearableBlockItem("galarica_wreath", CobblemonBlocks.GALARICA_WREATH)
+    @JvmField val CLEANSE_TAG = wearableBlockItem("cleanse_tag", CobblemonBlocks.CLEANSE_TAG)
+    @JvmField val SPELL_TAG = wearableBlockItem("spell_tag", CobblemonBlocks.SPELL_TAG)
 
     // Held Items
     @JvmField
     val ABILITY_SHIELD = heldItem("ability_shield")
     @JvmField
-    val ABOMASITE = heldItem("abomasite")
-    @JvmField
-    val ABSOLITE = heldItem("absolite")
-    @JvmField
     val ABSORB_BULB = heldItem("absorb_bulb")
     @JvmField
-    val AERODACTYLITE = heldItem("aerodactylite")
-    @JvmField
-    val AGGRONITE = heldItem("aggronite")
-    @JvmField
     val AIR_BALLOON = heldItem("air_balloon")
     @JvmField
-    val ALAKAZITE = heldItem("alakazite")
-    @JvmField
-    val ALTARIANITE = heldItem("altarianite")
-    @JvmField
-    val AMPHAROSITE = heldItem("ampharosite")
-    @JvmField
     val ASSAULT_VEST = heldItem("assault_vest")
     @JvmField
     val BIG_ROOT = compostableBlockItem("big_root", CobblemonBlocks.BIG_ROOT, 0.30f)
     @JvmField
-    val AUDINITE = heldItem("audinite")
-    @JvmField
-    val BANETTITE = heldItem("banettite")
-    @JvmField
-    val BEEDRILLITE = heldItem("beedrillite")
-    @JvmField
     val BINDING_BAND = heldItem("binding_band")
     @JvmField
     val BLACK_BELT = heldItem("black_belt")
@@ -972,35 +955,19 @@ object CobblemonItems : PlatformRegistry<Registry<Item>, ResourceKey<Registry<It
     @JvmField
     val BLUNDER_POLICY = itemNameBlockItem("blunder_policy", CobblemonBlocks.BLUNDER_POLICY)
     @JvmField
-    val BLASTOISINITE = heldItem("blastoisinite")
-    @JvmField
-    val BLAZIKENITE = heldItem("blazikenite")
-    @JvmField
-    val CAMERUPTITE = heldItem("cameruptite")
-    @JvmField
     val CELL_BATTERY = heldItem("cell_battery")
     @JvmField
     val CHARCOAL = heldItem("charcoal_stick", remappedName = "charcoal")
     @JvmField
-    val CHARIZARDITE_X = heldItem("charizardite_x")
-    @JvmField
-    val CHARIZARDITE_Y = heldItem("charizardite_y")
-    @JvmField
     val CHOICE_SCARF = heldItem("choice_scarf")
     @JvmField
-    val CLEANSE_TAG = itemNameBlockItem("cleanse_tag", CobblemonBlocks.CLEANSE_TAG)
-    @JvmField
     val CLEAR_AMULET = heldItem("clear_amulet")
     @JvmField
-    val COVERT_CLOAK = heldItem("covert_cloak")
-    @JvmField
-    val DESTINY_KNOT = heldItem("destiny_knot")
-    @JvmField
-    val DIANCITE = heldItem("diancite")
+    val DESTINY_KNOT = itemNameBlockItem("destiny_knot", CobblemonBlocks.DESTINY_KNOT)
     @JvmField
     val DRAGON_FANG = heldItem("dragon_fang")
     @JvmField
-    val EJECT_BUTTON = heldItem("eject_button")
+    val EJECT_BUTTON = itemNameBlockItem("eject_button", CobblemonBlocks.EJECT_BUTTON)
     @JvmField
     val EJECT_PACK = heldItem("eject_pack")
     @JvmField
@@ -1014,90 +981,46 @@ object CobblemonItems : PlatformRegistry<Registry<Item>, ResourceKey<Registry<It
     @JvmField
     val FAIRY_FEATHER = heldItem("fairy_feather")
     @JvmField
-    val FLAME_ORB = heldItem("flame_orb")
+    val FLAME_ORB = itemNameBlockItem("flame_orb", CobblemonBlocks.FLAME_ORB)
     @JvmField
     val FLOAT_STONE = heldItem("float_stone")
     @JvmField
     val FOCUS_SASH = heldItem("focus_sash")
     @JvmField
-    val GALLADITE = heldItem("galladite")
-    @JvmField
-    val GARCHOMPITE = heldItem("garchompite")
-    @JvmField
-    val GARDEVOIRITE = heldItem("gardevoirite")
-    @JvmField
-    val GENGARITE = heldItem("gengarite")
-    @JvmField
-    val GLALITITE = heldItem("glalitite")
-    @JvmField
     val GRASSY_SEED = heldItem("grassy_seed")
     @JvmField
     val GRIP_CLAW = heldItem("grip_claw")
     @JvmField
-    val GYARADOSITE = heldItem("gyaradosite")
-    @JvmField
     val HARD_STONE = heldItem("hard_stone")
     @JvmField
     val HEAVY_DUTY_BOOTS = heldItem("heavy_duty_boots")
     @JvmField
-    val HERACRONITE = heldItem("heracronite")
-    @JvmField
-    val HOUNDOOMINITE = heldItem("houndoominite")
-    @JvmField
-    val IRON_BALL = heldItem("iron_ball")
-    @JvmField
-    val KANGASKHANITE = heldItem("kangaskhanite")
+    val IRON_BALL = itemNameBlockItem("iron_ball", CobblemonBlocks.IRON_BALL)
     @JvmField
     val LAGGING_TAIL = heldItem("lagging_tail")
     @JvmField
     val LEFTOVERS = compostableHeldItem("leftovers", null, 0.50f)
     @JvmField
-    val LATIASITE = heldItem("latiasite")
+    val LIFE_ORB = itemNameBlockItem("life_orb", CobblemonBlocks.LIFE_ORB)
     @JvmField
-    val LATIOSITE = heldItem("latiosite")
-    @JvmField
-    val LIFE_ORB = heldItem("life_orb")
-    @JvmField
-    val LIGHT_BALL = heldItem("light_ball")
+    val LIGHT_BALL = itemNameBlockItem("light_ball", CobblemonBlocks.LIGHT_BALL)
     @JvmField
     val LIGHT_CLAY = heldItem("light_clay")
     @JvmField
-    val LOADED_DICE = heldItem("loaded_dice")
-    @JvmField
-    val LOPUNNITE = heldItem("lopunnite")
-    @JvmField
-    val LUCARIONITE = heldItem("lucarionite")
+    val LOADED_DICE = itemNameBlockItem("loaded_dice", CobblemonBlocks.LOADED_DICE)
     @JvmField
     val LUCKY_EGG = heldItem("lucky_egg")
     @JvmField
-    val LUMINOUS_MOSS = heldItem("luminous_moss")
+    val LUMINOUS_MOSS = itemNameBlockItem("luminous_moss", CobblemonBlocks.LUMINOUS_MOSS)
     @JvmField
-    val MAGNET = heldItem("magnet")
+    val MAGNET = itemNameBlockItem("magnet", CobblemonBlocks.MAGNET)
     @JvmField
-    val MANECTITE = heldItem("manectite")
-    @JvmField
-    val MAWILITE = heldItem("mawilite")
-    @JvmField
-    val MEDICHAMITE = heldItem("medichamite")
-    @JvmField
-    val METAGROSSITE = heldItem("metagrossite")
-    @JvmField
-    val METRONOME = heldItem("metronome")
-    @JvmField
-    val MEWTWONITE_X = heldItem("mewtwonite_x")
-    @JvmField
-    val MEWTWONITE_Y = heldItem("mewtwonite_y")
+    val METRONOME = itemNameBlockItem("metronome", CobblemonBlocks.METRONOME)
     @JvmField
     val MIRACLE_SEED = heldItem("miracle_seed")
     @JvmField
     val MYSTIC_WATER = heldItem("mystic_water")
     @JvmField
-    val NEVER_MELT_ICE = heldItem("never_melt_ice")
-    @JvmField
-    val PIDGEOTITE = heldItem("pidgeotite")
-    @JvmField
-    val PINSIRITE = heldItem("pinsirite")
-    @JvmField
     val POISON_BARB = heldItem("poison_barb")
     @JvmField
     val POWER_ANKLET = heldItem("power_anklet")
@@ -1122,23 +1045,11 @@ object CobblemonItems : PlatformRegistry<Registry<Item>, ResourceKey<Registry<It
     @JvmField
     val RED_CARD = heldItem("red_card")
     @JvmField
-    val RING_TARGET = heldItem("ring_target")
+    val RING_TARGET = itemNameBlockItem("ring_target", CobblemonBlocks.RING_TARGET)
     @JvmField
     val ROOM_SERVICE = heldItem("room_service")
     @JvmField
-    val SABLENITE = heldItem("sablenite")
-    @JvmField
-    val SALAMENCITE = heldItem("salamencite")
-    @JvmField
-    val SCEPTILITE = heldItem("sceptilite")
-    @JvmField
-    val SCIZORITE = heldItem("scizorite")
-    @JvmField
-    val SCOPE_LENS = heldItem("scope_lens")
-    @JvmField
-    val SHARP_BEAK = heldItem("sharp_beak")
-    @JvmField
-    val SHARPEDONITE = heldItem("sharpedonite")
+    val SCOPE_LENS = itemNameBlockItem("scope_lens", CobblemonBlocks.SCOPE_LENS)
     @JvmField
     val SHED_SHELL = heldItem("shed_shell")
     @JvmField
@@ -1148,41 +1059,29 @@ object CobblemonItems : PlatformRegistry<Registry<Item>, ResourceKey<Registry<It
     @JvmField
     val SILVER_POWDER = heldItem("silver_powder")
     @JvmField
-    val SLOWBRONITE = heldItem("slowbronite")
-    @JvmField
     val SOFT_SAND = heldItem("soft_sand")
     @JvmField
-    val SPELL_TAG = itemNameBlockItem("spell_tag", CobblemonBlocks.SPELL_TAG)
-    @JvmField
-    val SMOKE_BALL = heldItem("smoke_ball")
+    val SMOKE_BALL = itemNameBlockItem("smoke_ball", CobblemonBlocks.SMOKE_BALL)
     @JvmField
     val SOOTHE_BELL = heldItem("soothe_bell")
     @JvmField
-    val STEELIXITE = heldItem("steelixite")
-    @JvmField
     val STICKY_BARB = heldItem("sticky_barb")
     @JvmField
-    val SWAMPERTITE = heldItem("swampertite")
-    @JvmField
     val TERRAIN_EXTENDER = heldItem("terrain_extender")
     @JvmField
-    val THROAT_SPRAY = heldItem("throat_spray")
+    val THROAT_SPRAY = itemNameBlockItem("throat_spray", CobblemonBlocks.THROAT_SPRAY)
     @JvmField
-    val TOXIC_ORB = heldItem("toxic_orb")
+    val TOXIC_ORB = itemNameBlockItem("toxic_orb", CobblemonBlocks.TOXIC_ORB)
     @JvmField
     val TWISTED_SPOON = heldItem("twisted_spoon")
     @JvmField
-    val TYRANITARITE = heldItem("tyranitarite")
-    @JvmField
     val UTILITY_UMBRELLA = heldItem("utility_umbrella")
     @JvmField
     val WEAKNESS_POLICY = itemNameBlockItem("weakness_policy", CobblemonBlocks.WEAKNESS_POLICY)
     @JvmField
-    val VENUSAURITE = heldItem("venusaurite")
+    val WIDE_LENS = itemNameBlockItem("wide_lens", CobblemonBlocks.WIDE_LENS)
     @JvmField
-    val WIDE_LENS = heldItem("wide_lens")
-    @JvmField
-    val ZOOM_LENS = heldItem("zoom_lens")
+    val ZOOM_LENS = itemNameBlockItem("zoom_lens", CobblemonBlocks.ZOOM_LENS)
     @JvmField
     val MENTAL_HERB = compostableHeldItem("mental_herb", null, 0.85F)
     @JvmField
@@ -1194,19 +1093,19 @@ object CobblemonItems : PlatformRegistry<Registry<Item>, ResourceKey<Registry<It
     @JvmField
     val WHITE_HERB = compostableHeldItem("white_herb", null, 0.85F)
     @JvmField
-    val BRIGHT_POWDER = heldItem("bright_powder")
+    val BRIGHT_POWDER = itemNameBlockItem("bright_powder", CobblemonBlocks.BRIGHT_POWDER)
     @JvmField
-    val METAL_POWDER = heldItem("metal_powder")
+    val METAL_POWDER = itemNameBlockItem("metal_powder", CobblemonBlocks.METAL_POWDER)
     @JvmField
-    val QUICK_POWDER = heldItem("quick_powder")
+    val QUICK_POWDER = itemNameBlockItem("quick_powder", CobblemonBlocks.QUICK_POWDER)
     @JvmField
-    val DAMP_ROCK = heldItem("damp_rock")
+    val DAMP_ROCK = itemNameBlockItem("damp_rock", CobblemonBlocks.DAMP_ROCK)
     @JvmField
-    val HEAT_ROCK = heldItem("heat_rock")
+    val HEAT_ROCK = itemNameBlockItem("heat_rock", CobblemonBlocks.HEAT_ROCK)
     @JvmField
-    val SMOOTH_ROCK = heldItem("smooth_rock")
+    val SMOOTH_ROCK = itemNameBlockItem("smooth_rock", CobblemonBlocks.SMOOTH_ROCK)
     @JvmField
-    val ICY_ROCK = heldItem("icy_rock")
+    val ICY_ROCK = itemNameBlockItem("icy_rock", CobblemonBlocks.ICY_ROCK)
 
     // Mulch
     @JvmField
@@ -1697,7 +1596,16 @@ object CobblemonItems : PlatformRegistry<Registry<Item>, ResourceKey<Registry<It
 
     private fun wearableItem(name: String, heldItemRemappedName: String? = null): CobblemonItem = create(
         name,
-        WearableItem(name).also {
+        WearableHatItem(name).also {
+            wearables.add(it)
+            if (heldItemRemappedName != null) {
+                CobblemonHeldItemManager.registerRemap(it, heldItemRemappedName)
+            }
+        }
+    )
+    private fun wearableBlockItem(name: String, block: Block, heldItemRemappedName: String? = null): WearableBlockItem = create(
+        name,
+        WearableBlockItem(name, block).also {
             wearables.add(it)
             if (heldItemRemappedName != null) {
                 CobblemonHeldItemManager.registerRemap(it, heldItemRemappedName)
@@ -1854,4 +1762,4 @@ object CobblemonItems : PlatformRegistry<Registry<Item>, ResourceKey<Registry<It
     private fun foodItem(nutrition: Int, saturationModifier: Float): Item {
         return CobblemonItem(Item.Properties().food(FoodProperties.Builder().nutrition(nutrition).saturationModifier(saturationModifier).build()))
     }
-}
+}

common/src/main/kotlin/com/cobblemon/mod/common/CobblemonMemories.kt

@@ -15,12 +15,12 @@ import com.cobblemon.mod.common.api.moves.animations.ActionEffectContext
 import com.mojang.serialization.Codec
 import com.mojang.serialization.codecs.ListCodec
 import com.mojang.serialization.codecs.PrimitiveCodec
-import java.util.Optional
-import java.util.UUID
 import net.minecraft.core.BlockPos
+import net.minecraft.core.GlobalPos
 import net.minecraft.core.UUIDUtil
 import net.minecraft.world.entity.LivingEntity
 import net.minecraft.world.entity.ai.memory.MemoryModuleType
+import java.util.*
 
 object CobblemonMemories {
     val memories = mutableMapOf<String, MemoryModuleType<*>>()

common/src/main/kotlin/com/cobblemon/mod/common/CobblemonMenuType.kt

@@ -10,6 +10,7 @@ package com.cobblemon.mod.common
 
 
 import com.cobblemon.mod.common.block.campfirepot.CookingPotMenu
+import com.cobblemon.mod.common.api.molangui.container.MolangContainerMenu
 import com.cobblemon.mod.common.block.tmmachine.TMMachineMenu
 import com.cobblemon.mod.common.platform.PlatformRegistry
 import net.minecraft.core.Registry
@@ -22,9 +23,10 @@ object CobblemonMenuType : PlatformRegistry<Registry<MenuType<*>>, ResourceKey<R
 
     val COOKING_POT = MenuType.register("cooking_pot_menu", ::CookingPotMenu)
     val TM_MACHINE = MenuType.register("tm_machine_menu", ::TMMachineMenu)
+    val MOLANG_UI = MenuType.register("molang_ui", ::MolangContainerMenu)
 
     override val registry: Registry<MenuType<*>>
         get() = BuiltInRegistries.MENU
     override val resourceKey: ResourceKey<Registry<MenuType<*>>>
         get() = Registries.MENU
-}
+}

common/src/main/kotlin/com/cobblemon/mod/common/CobblemonNetwork.kt

@@ -32,6 +32,10 @@ import com.cobblemon.mod.common.client.net.effect.SpawnSnowstormParticleHandler
 import com.cobblemon.mod.common.client.net.gui.ExpGainedDataPacketHandler
 import com.cobblemon.mod.common.client.net.gui.InteractPokemonUIPacketHandler
 import com.cobblemon.mod.common.client.net.gui.PokedexUIPacketHandler
+import com.cobblemon.mod.common.client.net.molangui.MolangUiCloseHandler
+import com.cobblemon.mod.common.client.net.molangui.MolangUiCompatibilityRequestHandler
+import com.cobblemon.mod.common.client.net.molangui.MolangUiOpenHandler
+import com.cobblemon.mod.common.client.net.molangui.MolangUiUpdateHandler
 import com.cobblemon.mod.common.client.net.gui.SetActiveTMPacketHandler
 import com.cobblemon.mod.common.client.net.gui.SetTMMachineContainerDataPacketHandler
 import com.cobblemon.mod.common.client.net.gui.SummaryUIPacketHandler
@@ -83,6 +87,10 @@ import com.cobblemon.mod.common.net.messages.client.callback.OpenPartyMoveCallba
 import com.cobblemon.mod.common.net.messages.client.cooking.SeasoningRegistrySyncPacket
 import com.cobblemon.mod.common.net.messages.client.cooking.ToggleCookingPotLidPacket
 import com.cobblemon.mod.common.net.messages.client.data.*
+import com.cobblemon.mod.common.net.messages.client.molangui.MolangUiClosePacket
+import com.cobblemon.mod.common.net.messages.client.molangui.MolangUiCompatibilityRequestPacket
+import com.cobblemon.mod.common.net.messages.client.molangui.MolangUiOpenPacket
+import com.cobblemon.mod.common.net.messages.client.molangui.MolangUiUpdatePacket
 import com.cobblemon.mod.common.net.messages.client.debug.RequestOpenRidingStatsDebugGUIPacket
 import com.cobblemon.mod.common.net.messages.client.dialogue.DialogueClosedPacket
 import com.cobblemon.mod.common.net.messages.client.dialogue.DialogueOpenedPacket
@@ -107,14 +115,10 @@ import com.cobblemon.mod.common.net.messages.client.pokemon.update.evolution.Add
 import com.cobblemon.mod.common.net.messages.client.pokemon.update.evolution.ClearEvolutionsPacket
 import com.cobblemon.mod.common.net.messages.client.pokemon.update.evolution.ClientboundSeatAssignmentPacket
 import com.cobblemon.mod.common.net.messages.client.pokemon.update.evolution.RemoveEvolutionPacket
-import com.cobblemon.mod.common.net.messages.client.pokemon.update.form.AddFormPacket
-import com.cobblemon.mod.common.net.messages.client.pokemon.update.form.ClearFormsPacket
-import com.cobblemon.mod.common.net.messages.client.pokemon.update.form.RemoveFormPacket
 import com.cobblemon.mod.common.net.messages.client.settings.OpenCobblemonConfigScreenPacket
 import com.cobblemon.mod.common.net.messages.client.settings.ServerSettingsPacket
 import com.cobblemon.mod.common.net.messages.client.sound.UnvalidatedPlaySoundS2CPacket
 import com.cobblemon.mod.common.net.messages.client.spawn.SpawnGenericBedrockPacket
-import com.cobblemon.mod.common.net.messages.client.spawn.SpawnFallingStarPacket
 import com.cobblemon.mod.common.net.messages.client.spawn.SpawnNPCPacket
 import com.cobblemon.mod.common.net.messages.client.spawn.SpawnPokeballPacket
 import com.cobblemon.mod.common.net.messages.client.spawn.SpawnPokemonPacket
@@ -184,6 +188,9 @@ import com.cobblemon.mod.common.net.messages.server.dialogue.EscapeDialoguePacke
 import com.cobblemon.mod.common.net.messages.server.dialogue.InputToDialoguePacket
 import com.cobblemon.mod.common.net.messages.server.habitat.SaveHabitatBlockSettingsPacket
 import com.cobblemon.mod.common.net.messages.server.npc.SaveNPCPacket
+import com.cobblemon.mod.common.net.messages.server.molangui.MolangUiActionPacket
+import com.cobblemon.mod.common.net.messages.server.molangui.MolangUiClosedPacket
+import com.cobblemon.mod.common.net.messages.server.molangui.MolangUiCompatibilityResponsePacket
 import com.cobblemon.mod.common.net.messages.server.orientation.ServerboundUpdateOrientationPacket
 import com.cobblemon.mod.common.net.messages.server.pasture.PasturePokemonPacket
 import com.cobblemon.mod.common.net.messages.server.pasture.SetPastureConflictPacket
@@ -198,8 +205,6 @@ import com.cobblemon.mod.common.net.messages.server.pokemon.update.SetItemHidden
 import com.cobblemon.mod.common.net.messages.server.pokemon.update.SetMarkingsPacket
 import com.cobblemon.mod.common.net.messages.server.pokemon.update.SetNicknamePacket
 import com.cobblemon.mod.common.net.messages.server.pokemon.update.evolution.AcceptEvolutionPacket
-import com.cobblemon.mod.common.net.messages.server.pokemon.update.form.AcceptFormPacket
-import com.cobblemon.mod.common.net.messages.server.pokemon.update.form.RevertFormPacket
 import com.cobblemon.mod.common.net.messages.server.riding.DismountPokemonPacket
 import com.cobblemon.mod.common.net.messages.server.riding.ServerboundUpdateDriverInputPacket
 import com.cobblemon.mod.common.net.messages.server.riding.ServerboundUpdatePassengerPositionPacket
@@ -217,11 +222,9 @@ import com.cobblemon.mod.common.net.messages.server.trade.ChangeTradeAcceptanceP
 import com.cobblemon.mod.common.net.messages.server.trade.OfferTradePacket
 import com.cobblemon.mod.common.net.messages.server.trade.PerformTradePacket
 import com.cobblemon.mod.common.net.messages.server.trade.UpdateTradeOfferPacket
-import com.cobblemon.mod.common.net.serverhandling.AcceptFormHandler
 import com.cobblemon.mod.common.net.serverhandling.ChallengeHandler
 import com.cobblemon.mod.common.net.serverhandling.ChallengeResponseHandler
 import com.cobblemon.mod.common.net.serverhandling.RequestInteractionsHandler
-import com.cobblemon.mod.common.net.serverhandling.RevertFormHandler
 import com.cobblemon.mod.common.net.serverhandling.battle.BattleSelectActionsHandler
 import com.cobblemon.mod.common.net.serverhandling.battle.RemoveSpectatorHandler
 import com.cobblemon.mod.common.net.serverhandling.battle.SpectateBattleHandler
@@ -247,6 +250,9 @@ import com.cobblemon.mod.common.net.serverhandling.dialogue.InputToDialogueHandl
 import com.cobblemon.mod.common.net.serverhandling.evolution.AcceptEvolutionHandler
 import com.cobblemon.mod.common.net.serverhandling.habitat.SaveHabitatBlockSettingsHandler
 import com.cobblemon.mod.common.net.serverhandling.npc.SaveNPCHandler
+import com.cobblemon.mod.common.net.serverhandling.molangui.MolangUiActionHandler
+import com.cobblemon.mod.common.net.serverhandling.molangui.MolangUiClosedHandler
+import com.cobblemon.mod.common.net.serverhandling.molangui.MolangUiCompatibilityResponseHandler
 import com.cobblemon.mod.common.net.serverhandling.orientation.ServerboundUpdateOrientationHandler
 import com.cobblemon.mod.common.net.serverhandling.pasture.PasturePokemonHandler
 import com.cobblemon.mod.common.net.serverhandling.pasture.SetPastureConflictHandler
@@ -453,6 +459,11 @@ object CobblemonNetwork {
         list.add(PacketRegisterInfo(RideSettingsSyncPacket.ID, RideSettingsSyncPacket::decode, RideSettingsSyncHandler))
         list.add(PacketRegisterInfo(TechnicalMachineRegistrySyncPacket.ID, TechnicalMachineRegistrySyncPacket::decode, DataRegistrySyncPacketHandler()))
 
+        list.add(PacketRegisterInfo(MolangUiOpenPacket.ID, MolangUiOpenPacket::decode, MolangUiOpenHandler))
+        list.add(PacketRegisterInfo(MolangUiClosePacket.ID, MolangUiClosePacket::decode, MolangUiCloseHandler))
+        list.add(PacketRegisterInfo(MolangUiUpdatePacket.ID, MolangUiUpdatePacket::decode, MolangUiUpdateHandler))
+        list.add(PacketRegisterInfo(MolangUiCompatibilityRequestPacket.ID, MolangUiCompatibilityRequestPacket::decode, MolangUiCompatibilityRequestHandler))
+
         // Effects
         list.add(PacketRegisterInfo(SpawnSnowstormParticlePacket.ID, SpawnSnowstormParticlePacket::decode, SpawnSnowstormParticleHandler))
         list.add(PacketRegisterInfo(SpawnSnowstormEntityParticlePacket.ID, SpawnSnowstormEntityParticlePacket::decode, SpawnSnowstormEntityParticleHandler))
@@ -465,7 +476,6 @@ object CobblemonNetwork {
         list.add(PacketRegisterInfo(SpawnPokemonPacket.ID, SpawnPokemonPacket::decode, SpawnExtraDataEntityHandler()))
         list.add(PacketRegisterInfo(SpawnPokeballPacket.ID, SpawnPokeballPacket::decode, SpawnExtraDataEntityHandler()))
         list.add(PacketRegisterInfo(SpawnGenericBedrockPacket.ID, SpawnGenericBedrockPacket::decode, SpawnExtraDataEntityHandler()))
-        list.add(PacketRegisterInfo(SpawnFallingStarPacket.ID, SpawnFallingStarPacket::decode, SpawnExtraDataEntityHandler()))
         list.add(PacketRegisterInfo(SpawnNPCPacket.ID, SpawnNPCPacket::decode, SpawnExtraDataEntityHandler()))
         list.add(PacketRegisterInfo(ToastPacket.ID, ToastPacket::decode, ToastPacketHandler))
 
@@ -515,11 +525,6 @@ object CobblemonNetwork {
         // Pokédex scanning
         list.add(PacketRegisterInfo(ServerConfirmedRegisterPacket.ID, ServerConfirmedRegisterPacket::decode, ServerConfirmedRegisterHandler))
 
-        // Form packets
-        list.add(PacketRegisterInfo(AddFormPacket.ID, AddFormPacket::decode, PokemonUpdatePacketHandler()))
-        list.add(PacketRegisterInfo(ClearFormsPacket.ID, ClearFormsPacket::decode, PokemonUpdatePacketHandler()))
-        list.add(PacketRegisterInfo(RemoveFormPacket.ID, RemoveFormPacket::decode, PokemonUpdatePacketHandler()))
-
         // Riding
         list.add(PacketRegisterInfo(ClientboundUpdateRidingStatePacket.ID, ClientboundUpdateRidingStatePacket::decode, ClientboundUpdateRidingStateHandler))
         list.add(PacketRegisterInfo(ClientboundUpdateDriverInputPacket.ID, ClientboundUpdateDriverInputPacket::decode, ClientboundUpdateDriverInputHandler))
@@ -635,10 +640,6 @@ object CobblemonNetwork {
         // NPC packets
         list.add(PacketRegisterInfo(SaveNPCPacket.ID, SaveNPCPacket::decode, SaveNPCHandler))
 
-        // Form Packets
-        list.add(PacketRegisterInfo(AcceptFormPacket.ID, AcceptFormPacket::decode, AcceptFormHandler))
-        list.add(PacketRegisterInfo(RevertFormPacket.ID, RevertFormPacket::decode, RevertFormHandler))
-
         // Riding packet(s)
         list.add(PacketRegisterInfo(ServerboundUpdateOrientationPacket.ID, ServerboundUpdateOrientationPacket::decode, ServerboundUpdateOrientationHandler))
         list.add(PacketRegisterInfo(ServerboundUpdateRidingStatePacket.ID, ServerboundUpdateRidingStatePacket::decode, ServerboundUpdateRidingStateHandler))
@@ -661,6 +662,10 @@ object CobblemonNetwork {
         list.add(PacketRegisterInfo(SetEntityBehaviourPacket.ID, SetEntityBehaviourPacket::decode, SetEntityBehaviourHandler))
         list.add(PacketRegisterInfo(DamageOnCollisionPacket.ID, DamageOnCollisionPacket::decode, DamageOnCollisionPacketHandler))
 
+        list.add(PacketRegisterInfo(MolangUiActionPacket.ID, MolangUiActionPacket::decode, MolangUiActionHandler))
+        list.add(PacketRegisterInfo(MolangUiClosedPacket.ID, MolangUiClosedPacket::decode, MolangUiClosedHandler))
+        list.add(PacketRegisterInfo(MolangUiCompatibilityResponsePacket.ID, MolangUiCompatibilityResponsePacket::decode, MolangUiCompatibilityResponseHandler))
+
         // Habitat blocks
         list.add(PacketRegisterInfo(SaveHabitatBlockSettingsPacket.ID, SaveHabitatBlockSettingsPacket::decode, SaveHabitatBlockSettingsHandler))
 
@@ -674,4 +679,4 @@ object CobblemonNetwork {
     fun sendPacketToPlayer(player: ServerPlayer, packet: NetworkPacket<*>) {
         Cobblemon.implementation.networkManager.sendPacketToPlayer(player, packet)
     }
-}
+}

common/src/main/kotlin/com/cobblemon/mod/common/CobblemonSensors.kt

@@ -9,9 +9,9 @@
 package com.cobblemon.mod.common
 
 import com.cobblemon.mod.common.entity.pokemon.ai.sensors.*
+import com.cobblemon.mod.common.pokemon.ai.PokemonDisturbancesSensor
 import com.cobblemon.mod.common.entity.sensor.BattlingPokemonSensor
 import com.cobblemon.mod.common.entity.sensor.NPCBattlingSensor
-import com.cobblemon.mod.common.pokemon.ai.PokemonDisturbancesSensor
 import java.util.function.Supplier
 import net.minecraft.world.entity.Entity
 import net.minecraft.world.entity.ai.sensing.Sensor

common/src/main/kotlin/com/cobblemon/mod/common/CobblemonTradeOffers.kt

@@ -8,7 +8,6 @@
 
 package com.cobblemon.mod.common
 
-import java.util.Optional
 import net.minecraft.core.registries.BuiltInRegistries
 import net.minecraft.util.RandomSource
 import net.minecraft.world.entity.Entity
@@ -19,6 +18,7 @@ import net.minecraft.world.item.ItemStack
 import net.minecraft.world.item.Items
 import net.minecraft.world.item.trading.ItemCost
 import net.minecraft.world.item.trading.MerchantOffer
+import java.util.Optional
 
 /**
  * A generator for various trade offers in the mod.

common/src/main/kotlin/com/cobblemon/mod/common/advancement/criterion/AspectCriterion.kt

@@ -11,10 +11,10 @@ package com.cobblemon.mod.common.advancement.criterion
 import com.cobblemon.mod.common.util.cobblemonResource
 import com.mojang.serialization.Codec
 import com.mojang.serialization.codecs.RecordCodecBuilder
-import java.util.Optional
 import net.minecraft.advancements.critereon.ContextAwarePredicate
 import net.minecraft.resources.ResourceLocation
 import net.minecraft.server.level.ServerPlayer
+import java.util.Optional
 
 class AspectCriterion(
     playerCtx: Optional<ContextAwarePredicate>,

common/src/main/kotlin/com/cobblemon/mod/common/advancement/criterion/CastPokeRodCriterionCondition.kt

@@ -14,8 +14,8 @@ import com.mojang.serialization.codecs.RecordCodecBuilder
 import java.util.Optional
 import net.minecraft.advancements.critereon.ContextAwarePredicate
 import net.minecraft.advancements.critereon.EntityPredicate
-import net.minecraft.resources.ResourceLocation
 import net.minecraft.server.level.ServerPlayer
+import net.minecraft.resources.ResourceLocation
 
 class CastPokeRodContext(val baitId: ResourceLocation)
 

common/src/main/kotlin/com/cobblemon/mod/common/advancement/criterion/CatchPokemonCriterion.kt

@@ -10,10 +10,10 @@ package com.cobblemon.mod.common.advancement.criterion
 
 import com.mojang.serialization.Codec
 import com.mojang.serialization.codecs.RecordCodecBuilder
-import java.util.Optional
 import net.minecraft.advancements.critereon.ContextAwarePredicate
 import net.minecraft.advancements.critereon.EntityPredicate
 import net.minecraft.server.level.ServerPlayer
+import java.util.Optional
 
 /**
  * A context that is used when you require a [CountableContext] along with some type string.

common/src/main/kotlin/com/cobblemon/mod/common/advancement/criterion/ReelInPokemonCriterionCondition.kt

@@ -14,8 +14,8 @@ import com.mojang.serialization.codecs.RecordCodecBuilder
 import java.util.Optional
 import net.minecraft.advancements.critereon.ContextAwarePredicate
 import net.minecraft.advancements.critereon.EntityPredicate
-import net.minecraft.resources.ResourceLocation
 import net.minecraft.server.level.ServerPlayer
+import net.minecraft.resources.ResourceLocation
 
 class ReelInPokemonContext(val species : ResourceLocation, val baitId: ResourceLocation)
 

common/src/main/kotlin/com/cobblemon/mod/common/api/abilities/AbilityTemplate.kt

@@ -9,7 +9,6 @@
 package com.cobblemon.mod.common.api.abilities
 
 import com.cobblemon.mod.common.api.Priority
-import com.cobblemon.mod.common.api.data.ShowdownIdentifiable
 import com.cobblemon.mod.common.util.codec.CodecUtils
 import com.google.gson.JsonObject
 import com.mojang.serialization.Codec
@@ -26,7 +25,7 @@ class AbilityTemplate(
     var builder: (AbilityTemplate, forced: Boolean, priority: Priority) -> Ability = { template, forced, priority -> Ability(template, forced, priority) },
     val displayName: String = "cobblemon.ability.$name",
     val description: String = "cobblemon.ability.$name.desc"
-) : ShowdownIdentifiable {
+) {
     /**
      * Returns the Ability or if applicable the extension connected to this template
      */
@@ -46,8 +45,6 @@ class AbilityTemplate(
      */
     fun create(json: JsonObject) = create().loadFromJSON(json)
 
-    override fun showdownId(): String = ShowdownIdentifiable.REGEX.replace(this.name.lowercase(), "")
-
     companion object {
 
         @JvmStatic

common/src/main/kotlin/com/cobblemon/mod/common/api/ai/BehaviourConfigurationContext.kt

@@ -18,6 +18,7 @@ import com.cobblemon.mod.common.api.molang.MoLangFunctions.addStandardFunctions
 import com.cobblemon.mod.common.api.molang.MoLangFunctions.asMostSpecificMoLangValue
 import com.cobblemon.mod.common.api.molang.MoLangFunctions.setup
 import com.cobblemon.mod.common.api.molang.ObjectValue
+import com.cobblemon.mod.common.api.scripting.CobblemonScripts
 import com.cobblemon.mod.common.entity.MoLangScriptingEntity
 import com.cobblemon.mod.common.util.activityRegistry
 import com.cobblemon.mod.common.util.asIdentifierDefaultingNamespace

common/src/main/kotlin/com/cobblemon/mod/common/api/ai/CobblemonBehaviour.kt

@@ -13,6 +13,7 @@ import com.cobblemon.mod.common.api.ai.config.BehaviourConfig
 import com.cobblemon.mod.common.api.molang.ExpressionLike
 import com.cobblemon.mod.common.api.molang.MoLangFunctions.asMostSpecificMoLangValue
 import com.cobblemon.mod.common.api.molang.MoLangFunctions.setup
+import com.cobblemon.mod.common.api.scripting.CobblemonScripts
 import com.cobblemon.mod.common.util.asTranslated
 import com.cobblemon.mod.common.util.resolve
 import com.cobblemon.mod.common.util.withQueryValue

common/src/main/kotlin/com/cobblemon/mod/common/api/ai/CobblemonWanderControl.kt

@@ -13,6 +13,7 @@ import com.cobblemon.mod.common.util.getBooleanOrNull
 import com.cobblemon.mod.common.util.getDoubleOrNull
 import kotlin.math.sqrt
 import net.minecraft.core.BlockPos
+import net.minecraft.world.entity.PathfinderMob
 
 /**
  * Used to maintain some settings around how the entity should wander this tick. The idea is you

common/src/main/kotlin/com/cobblemon/mod/common/api/ai/config/BehaviourConfig.kt

@@ -8,12 +8,16 @@
 
 package com.cobblemon.mod.common.api.ai.config
 
+import com.bedrockk.molang.runtime.MoLangRuntime
 import com.cobblemon.mod.common.api.ai.BehaviourConfigurationContext
 import com.cobblemon.mod.common.api.ai.ExpressionOrEntityVariable
+import com.cobblemon.mod.common.api.molang.MoLangFunctions.asMostSpecificMoLangValue
+import com.cobblemon.mod.common.api.molang.MoLangFunctions.setup
 import com.cobblemon.mod.common.api.npc.configuration.MoLangConfigVariable
 import com.cobblemon.mod.common.util.asExpression
 import com.cobblemon.mod.common.util.cobblemonResource
 import com.cobblemon.mod.common.util.resolveBoolean
+import com.cobblemon.mod.common.util.withQueryValue
 import net.minecraft.resources.ResourceLocation
 import net.minecraft.world.entity.LivingEntity
 

common/src/main/kotlin/com/cobblemon/mod/common/api/ai/config/task/RandomTaskConfig.kt

@@ -11,8 +11,13 @@ package com.cobblemon.mod.common.api.ai.config.task
 import com.cobblemon.mod.common.api.ai.BehaviourConfigurationContext
 import com.cobblemon.mod.common.api.ai.ExpressionOrEntityVariable
 import com.cobblemon.mod.common.api.ai.asVariables
+import com.cobblemon.mod.common.api.molang.ExpressionLike
+import com.cobblemon.mod.common.api.molang.MoLangFunctions.asMostSpecificMoLangValue
 import com.cobblemon.mod.common.util.asExpression
+import com.cobblemon.mod.common.util.asExpressionLike
+import com.cobblemon.mod.common.util.resolveBoolean
 import com.cobblemon.mod.common.util.weightedSelection
+import com.cobblemon.mod.common.util.withQueryValue
 import com.mojang.datafixers.util.Either
 import net.minecraft.world.entity.LivingEntity
 import net.minecraft.world.entity.ai.behavior.BehaviorControl

common/src/main/kotlin/com/cobblemon/mod/common/api/ai/config/task/StopAttackingIfTargetInvalidTaskConfig.kt

@@ -8,10 +8,12 @@
 
 package com.cobblemon.mod.common.api.ai.config.task
 
+import com.bedrockk.molang.runtime.MoLangRuntime
 import com.cobblemon.mod.common.CobblemonMemories
 import com.cobblemon.mod.common.api.ai.BehaviourConfigurationContext
 import com.cobblemon.mod.common.api.ai.WrapperLivingEntityTask.Companion.wrapped
 import com.cobblemon.mod.common.api.molang.MoLangFunctions.asMostSpecificMoLangValue
+import com.cobblemon.mod.common.api.molang.MoLangFunctions.setup
 import com.cobblemon.mod.common.api.npc.configuration.MoLangConfigVariable
 import com.cobblemon.mod.common.util.mainThreadRuntime
 import com.cobblemon.mod.common.util.resolveBoolean

common/src/main/kotlin/com/cobblemon/mod/common/api/ai/config/task/StopBeingAngryIfAttackerDeadTaskConfig.kt

@@ -10,6 +10,8 @@ package com.cobblemon.mod.common.api.ai.config.task
 
 import com.cobblemon.mod.common.api.ai.BehaviourConfigurationContext
 import com.cobblemon.mod.common.api.ai.asVariables
+import com.cobblemon.mod.common.api.molang.MoLangFunctions.asMostSpecificMoLangValue
+import com.cobblemon.mod.common.util.withQueryValue
 import net.minecraft.world.entity.LivingEntity
 import net.minecraft.world.entity.ai.behavior.BehaviorControl
 import net.minecraft.world.entity.ai.behavior.StopBeingAngryIfTargetDead

common/src/main/kotlin/com/cobblemon/mod/common/api/ai/config/task/SwitchToFightTaskConfig.kt

@@ -9,7 +9,9 @@
 package com.cobblemon.mod.common.api.ai.config.task
 
 import com.cobblemon.mod.common.api.ai.BehaviourConfigurationContext
+import com.cobblemon.mod.common.api.molang.MoLangFunctions.asMostSpecificMoLangValue
 import com.cobblemon.mod.common.api.npc.configuration.MoLangConfigVariable
+import com.cobblemon.mod.common.util.withQueryValue
 import net.minecraft.world.Difficulty
 import net.minecraft.world.entity.LivingEntity
 import net.minecraft.world.entity.ai.behavior.declarative.BehaviorBuilder

common/src/main/kotlin/com/cobblemon/mod/common/api/ai/config/task/SwitchToNPCBattleTaskConfig.kt

@@ -15,6 +15,7 @@ import com.cobblemon.mod.common.api.npc.configuration.MoLangConfigVariable
 import com.cobblemon.mod.common.entity.npc.ai.SwitchToBattleTask
 import net.minecraft.world.entity.LivingEntity
 import net.minecraft.world.entity.ai.behavior.BehaviorControl
+import net.minecraft.world.entity.ai.memory.MemoryModuleType
 
 class SwitchToNPCBattleTaskConfig : SingleTaskConfig {
     override fun getVariables(entity: LivingEntity, behaviourConfigurationContext: BehaviourConfigurationContext) = emptyList<MoLangConfigVariable>()

common/src/main/kotlin/com/cobblemon/mod/common/api/ai/config/task/SwitchToPanicWhenHostilesNearbyTaskConfig.kt

@@ -10,6 +10,8 @@ package com.cobblemon.mod.common.api.ai.config.task
 
 import com.cobblemon.mod.common.api.ai.BehaviourConfigurationContext
 import com.cobblemon.mod.common.api.ai.asVariables
+import com.cobblemon.mod.common.api.molang.MoLangFunctions.asMostSpecificMoLangValue
+import com.cobblemon.mod.common.util.withQueryValue
 import net.minecraft.world.entity.LivingEntity
 import net.minecraft.world.entity.PathfinderMob
 import net.minecraft.world.entity.ai.behavior.BehaviorControl

common/src/main/kotlin/com/cobblemon/mod/common/api/ai/config/task/SwitchToPanicWhenHurtTaskConfig.kt

@@ -10,6 +10,8 @@ package com.cobblemon.mod.common.api.ai.config.task
 
 import com.cobblemon.mod.common.api.ai.BehaviourConfigurationContext
 import com.cobblemon.mod.common.api.ai.asVariables
+import com.cobblemon.mod.common.api.molang.MoLangFunctions.asMostSpecificMoLangValue
+import com.cobblemon.mod.common.util.withQueryValue
 import net.minecraft.world.entity.LivingEntity
 import net.minecraft.world.entity.PathfinderMob
 import net.minecraft.world.entity.ai.behavior.BehaviorControl

common/src/main/kotlin/com/cobblemon/mod/common/api/ai/config/task/TargetEntityTaskConfig.kt

@@ -25,6 +25,7 @@ import net.minecraft.world.entity.ai.behavior.BehaviorControl
 import net.minecraft.world.entity.ai.behavior.declarative.BehaviorBuilder
 import net.minecraft.world.entity.ai.behavior.declarative.Trigger
 import net.minecraft.world.entity.ai.memory.MemoryModuleType
+import net.minecraft.world.entity.ai.memory.MemoryStatus
 import net.minecraft.world.entity.ai.sensing.SensorType
 
 /**

common/src/main/kotlin/com/cobblemon/mod/common/api/ai/config/task/WaterWanderTaskConfig.kt

@@ -22,7 +22,6 @@ import com.cobblemon.mod.common.util.mainThreadRuntime
 import com.cobblemon.mod.common.util.resolveFloat
 import com.cobblemon.mod.common.util.withQueryValue
 import com.mojang.datafixers.util.Either
-import kotlin.math.ceil
 import net.minecraft.core.BlockPos
 import net.minecraft.world.entity.LivingEntity
 import net.minecraft.world.entity.PathfinderMob
@@ -35,6 +34,7 @@ import net.minecraft.world.entity.ai.memory.MemoryModuleType
 import net.minecraft.world.level.material.Fluids
 import net.minecraft.world.level.pathfinder.PathType
 import net.minecraft.world.phys.Vec3
+import kotlin.math.ceil
 
 class WaterWanderTaskConfig : SingleTaskConfig {
     val condition = booleanVariable(WANDER, "water_wanders", true).asExpressible()

common/src/main/kotlin/com/cobblemon/mod/common/api/battles/model/PokemonBattle.kt

@@ -54,9 +54,9 @@ import com.cobblemon.mod.common.net.messages.client.battle.BattleEndPacket
 import com.cobblemon.mod.common.net.messages.client.battle.BattleMakeChoicePacket
 import com.cobblemon.mod.common.net.messages.client.battle.BattleMessagePacket
 import com.cobblemon.mod.common.net.messages.client.battle.BattleQueueRequestPacket
-import com.cobblemon.mod.common.pokemon.transformation.progress.DefeatTransformationProgress
-import com.cobblemon.mod.common.pokemon.transformation.progress.LastBattleCriticalHitsTransformationProgress
-import com.cobblemon.mod.common.pokemon.transformation.requirements.DefeatRequirement
+import com.cobblemon.mod.common.pokemon.evolution.progress.DefeatEvolutionProgress
+import com.cobblemon.mod.common.pokemon.evolution.progress.LastBattleCriticalHitsEvolutionProgress
+import com.cobblemon.mod.common.pokemon.requirements.DefeatRequirement
 import com.cobblemon.mod.common.util.battleLang
 import com.cobblemon.mod.common.util.getPlayer
 import com.cobblemon.mod.common.util.giveOrDropItemStack
@@ -97,8 +97,8 @@ open class PokemonBattle(
         this.actors.forEach { actor ->
             actor.battle = this
             actor.pokemonList.forEach { battlePokemon ->
-                battlePokemon.effectedPokemon.requirementProgress
-                    .filterIsInstance<LastBattleCriticalHitsTransformationProgress>()
+                battlePokemon.effectedPokemon.evolutionProxy.current().progress()
+                    .filterIsInstance<LastBattleCriticalHitsEvolutionProgress>()
                     .forEach { it.reset() }
             }
         }
@@ -271,13 +271,12 @@ open class PokemonBattle(
                         val facedFainted = opponentPokemon.facedOpponents.contains(faintedPokemon)
                         val pokemon = opponentPokemon.effectedPokemon
                         if (facedFainted) {
-                            if (pokemon.hasMatchingRequirement<DefeatRequirement>({ it.target.matches(faintedPokemon.effectedPokemon) })) {
-                                val requiredPokemonProperties = pokemon.getRelevantRequirements<DefeatRequirement> { it.target.matches(faintedPokemon.effectedPokemon) }
-                                    .map { it.target }
-                                    .distinctBy { it.asString() }
-                                for (props in requiredPokemonProperties) {
-                                    val progress = pokemon.progressFirstOrCreate({ it is DefeatTransformationProgress && it.currentProgress().target.asString().equals(props.asString(), ignoreCase = true) }, ::DefeatTransformationProgress)
-                                    progress.updateProgress(DefeatTransformationProgress.Progress(props.copy(), progress.currentProgress().amount + 1))
+                            pokemon.lockedEvolutions.forEach { evolution ->
+                                evolution.requirements.filterIsInstance<DefeatRequirement>().forEach { defeatRequirement ->
+                                    if (defeatRequirement.target.matches(faintedPokemon.effectedPokemon)) {
+                                        val progress = pokemon.evolutionProxy.current().progressFirstOrCreate({ it is DefeatEvolutionProgress && it.currentProgress().target == defeatRequirement.target }) { DefeatEvolutionProgress() }
+                                        progress.updateProgress(DefeatEvolutionProgress.Progress(defeatRequirement.target, progress.currentProgress().amount + 1))
+                                    }
                                 }
                             }
                         }

common/src/main/kotlin/com/cobblemon/mod/common/api/battles/model/actor/BattleActor.kt

@@ -22,9 +22,9 @@ import com.cobblemon.mod.common.item.battle.BagItem
 import com.cobblemon.mod.common.net.messages.client.battle.BattleApplyPassResponsePacket
 import com.cobblemon.mod.common.net.messages.client.battle.BattleMakeChoicePacket
 import com.cobblemon.mod.common.net.messages.client.battle.BattleMessagePacket
-import java.util.UUID
 import net.minecraft.network.chat.Component
 import net.minecraft.network.chat.MutableComponent
+import java.util.UUID
 import net.minecraft.server.level.ServerPlayer
 
 abstract class BattleActor(

common/src/main/kotlin/com/cobblemon/mod/common/api/berry/Berries.kt

@@ -21,7 +21,6 @@ import com.cobblemon.mod.common.util.adapters.*
 import com.cobblemon.mod.common.util.cobblemonResource
 import com.google.gson.GsonBuilder
 import com.google.gson.reflect.TypeToken
-import java.awt.Color
 import net.minecraft.advancements.critereon.MinMaxBounds
 import net.minecraft.core.registries.Registries
 import net.minecraft.resources.ResourceLocation
@@ -31,6 +30,7 @@ import net.minecraft.tags.TagKey
 import net.minecraft.world.level.biome.Biome
 import net.minecraft.world.phys.AABB
 import net.minecraft.world.phys.Vec3
+import java.awt.Color
 
 /**
  * The data registry for [Berry].

common/src/main/kotlin/com/cobblemon/mod/common/api/berry/Berry.kt

@@ -26,10 +26,10 @@ import com.cobblemon.mod.common.util.writeBox
 import com.cobblemon.mod.common.util.writeEnumConstant
 import com.cobblemon.mod.common.util.writeIdentifier
 import com.google.gson.annotations.SerializedName
-import java.awt.Color
-import java.util.EnumSet
 import net.minecraft.core.BlockPos
 import net.minecraft.network.RegistryFriendlyByteBuf
+import java.awt.Color
+import java.util.EnumSet
 import net.minecraft.resources.ResourceLocation
 import net.minecraft.tags.TagKey
 import net.minecraft.world.entity.LivingEntity

common/src/main/kotlin/com/cobblemon/mod/common/api/drop/EvolutionItemDropEntry.kt

@@ -8,11 +8,11 @@
 
 package com.cobblemon.mod.common.api.drop
 
-import com.cobblemon.mod.common.api.pokemon.transformation.requirement.TransformationRequirement
+import com.cobblemon.mod.common.api.pokemon.requirement.Requirement
 import com.cobblemon.mod.common.pokemon.Pokemon
 
 class EvolutionItemDropEntry : ItemDropEntry() {
-    val requirements: MutableSet<TransformationRequirement> = mutableSetOf()
+    val requirements: MutableSet<Requirement> = mutableSetOf()
 
     override fun canDrop(pokemon: Pokemon?): Boolean = pokemon != null && requirements.all { it.check(pokemon) }
 }

common/src/main/kotlin/com/cobblemon/mod/common/api/events/CobblemonEvents.kt

@@ -48,10 +48,6 @@ import com.cobblemon.mod.common.api.events.pokemon.evolution.EvolutionAcceptedEv
 import com.cobblemon.mod.common.api.events.pokemon.evolution.EvolutionCompleteEvent
 import com.cobblemon.mod.common.api.events.pokemon.evolution.EvolutionDisplayEvent
 import com.cobblemon.mod.common.api.events.pokemon.evolution.EvolutionTestedEvent
-import com.cobblemon.mod.common.api.events.pokemon.form.FormAcceptedEvent
-import com.cobblemon.mod.common.api.events.pokemon.form.FormCompleteEvent
-import com.cobblemon.mod.common.api.events.pokemon.form.FormDisplayEvent
-import com.cobblemon.mod.common.api.events.pokemon.form.FormTestedEvent
 import com.cobblemon.mod.common.api.events.pokemon.healing.PokemonHealedEvent
 import com.cobblemon.mod.common.api.events.pokemon.interaction.ExperienceCandyUseEvent
 import com.cobblemon.mod.common.api.events.pokemon.interaction.PokemonInteractionGUICreationEvent
@@ -107,18 +103,6 @@ object CobblemonEvents {
     @JvmField
     val EVOLUTION_COMPLETE = EventObservable<EvolutionCompleteEvent>()
 
-    @JvmField
-    val FORM_ACCEPTED = CancelableObservable<FormAcceptedEvent>()
-
-    @JvmField
-    val FORM_DISPLAY = EventObservable<FormDisplayEvent>()
-
-    @JvmField
-    val FORM_TESTED = EventObservable<FormTestedEvent>()
-
-    @JvmField
-    val FORM_COMPLETE = EventObservable<FormCompleteEvent>()
-
     @JvmField
     val POKEMON_NICKNAMED = CancelableObservable<PokemonNicknamedEvent>()
 

common/src/main/kotlin/com/cobblemon/mod/common/api/events/battles/BattleVictoryEvent.kt

@@ -15,7 +15,9 @@ import com.cobblemon.mod.common.api.battles.model.actor.ActorType
 import com.cobblemon.mod.common.api.battles.model.actor.BattleActor
 import com.cobblemon.mod.common.api.battles.model.actor.EntityBackedBattleActor
 import com.cobblemon.mod.common.api.molang.MoLangFunctions.asMostSpecificMoLangValue
+import com.cobblemon.mod.common.battles.actor.PlayerBattleActor
 import com.cobblemon.mod.common.entity.MoLangScriptingEntity
+import com.cobblemon.mod.common.entity.npc.NPCBattleActor
 import com.cobblemon.mod.common.util.asArrayValue
 import net.minecraft.world.entity.LivingEntity
 

common/src/main/kotlin/com/cobblemon/mod/common/api/events/pokemon/TradeEvent.kt

@@ -12,6 +12,7 @@ import com.bedrockk.molang.runtime.value.DoubleValue
 import com.cobblemon.mod.common.api.events.Cancelable
 import com.cobblemon.mod.common.api.molang.MoLangFunctions.asMoLangValue
 import com.cobblemon.mod.common.api.molang.MoLangFunctions.moLangFunctionMap
+import com.cobblemon.mod.common.entity.pokemon.PokemonEntity
 import com.cobblemon.mod.common.pokemon.Pokemon
 import com.cobblemon.mod.common.trade.TradeParticipant
 import com.cobblemon.mod.common.util.getPlayer

common/src/main/kotlin/com/cobblemon/mod/common/api/events/pokemon/evolution/EvolutionAcceptedEvent.kt

@@ -12,8 +12,8 @@ import com.bedrockk.molang.runtime.value.MoValue
 import com.cobblemon.mod.common.api.events.Cancelable
 import com.cobblemon.mod.common.api.molang.MoLangFunctions.asMoLangValue
 import com.cobblemon.mod.common.api.molang.MoLangFunctions.moLangFunctionMap
+import com.cobblemon.mod.common.api.pokemon.evolution.Evolution
 import com.cobblemon.mod.common.pokemon.Pokemon
-import com.cobblemon.mod.common.pokemon.transformation.evolution.Evolution
 
 /**
  * Fired when an evolution is accepted.

common/src/main/kotlin/com/cobblemon/mod/common/api/events/pokemon/evolution/EvolutionCompleteEvent.kt

@@ -10,8 +10,8 @@ package com.cobblemon.mod.common.api.events.pokemon.evolution
 
 import com.bedrockk.molang.runtime.value.MoValue
 import com.cobblemon.mod.common.api.molang.MoLangFunctions.asMoLangValue
+import com.cobblemon.mod.common.api.pokemon.evolution.Evolution
 import com.cobblemon.mod.common.pokemon.Pokemon
-import com.cobblemon.mod.common.pokemon.transformation.evolution.Evolution
 
 /**
  * Fired after an evolution finishes.

common/src/main/kotlin/com/cobblemon/mod/common/api/events/pokemon/evolution/EvolutionDisplayEvent.kt

@@ -8,9 +8,9 @@
 
 package com.cobblemon.mod.common.api.events.pokemon.evolution
 
-import com.cobblemon.mod.common.pokemon.transformation.evolution.Evolution
+import com.cobblemon.mod.common.api.pokemon.evolution.Evolution
+import com.cobblemon.mod.common.api.pokemon.evolution.EvolutionDisplay
 import com.cobblemon.mod.common.pokemon.Pokemon
-import com.cobblemon.mod.common.pokemon.transformation.evolution.EvolutionDisplay
 
 /**
  * Fired before an evolution is sent to clients.

common/src/main/kotlin/com/cobblemon/mod/common/api/events/pokemon/evolution/EvolutionEvent.kt

@@ -8,7 +8,7 @@
 
 package com.cobblemon.mod.common.api.events.pokemon.evolution
 
-import com.cobblemon.mod.common.pokemon.transformation.evolution.Evolution
+import com.cobblemon.mod.common.api.pokemon.evolution.Evolution
 import com.cobblemon.mod.common.pokemon.Pokemon
 
 /**

common/src/main/kotlin/com/cobblemon/mod/common/api/events/pokemon/evolution/EvolutionTestedEvent.kt

@@ -12,8 +12,8 @@ import com.bedrockk.molang.runtime.value.DoubleValue
 import com.bedrockk.molang.runtime.value.MoValue
 import com.cobblemon.mod.common.api.molang.MoLangFunctions.asMoLangValue
 import com.cobblemon.mod.common.api.molang.MoLangFunctions.moLangFunctionMap
+import com.cobblemon.mod.common.api.pokemon.evolution.Evolution
 import com.cobblemon.mod.common.pokemon.Pokemon
-import com.cobblemon.mod.common.pokemon.transformation.evolution.Evolution
 import com.cobblemon.mod.common.util.getBoolean
 
 /**

common/src/main/kotlin/com/cobblemon/mod/common/api/events/pokemon/form/FormAcceptedEvent.kt

@@ -1,37 +0,0 @@
-/*
- * Copyright (C) 2023 Cobblemon Contributors
- *
- * This Source Code Form is subject to the terms of the Mozilla Public
- * License, v. 2.0. If a copy of the MPL was not distributed with this
- * file, You can obtain one at https://mozilla.org/MPL/2.0/.
- */
-
-package com.cobblemon.mod.common.api.events.pokemon.form
-
-import com.bedrockk.molang.runtime.value.StringValue
-import com.cobblemon.mod.common.api.events.Cancelable
-import com.cobblemon.mod.common.api.molang.MoLangFunctions.moLangFunctionMap
-import com.cobblemon.mod.common.pokemon.Pokemon
-import com.cobblemon.mod.common.pokemon.transformation.form.TemporaryForm
-
-/**
- * Fired when a temporary form change is accepted.
- * Cancelling will not notify users nor remove the form from the pending list.
- *
- * @param pokemon The [Pokemon] about to change form.
- * @param form The [TemporaryForm] being used.
- *
- * @author Hiroku
- * @since June 3rd, 2026
- */
-data class FormAcceptedEvent(
-    override val pokemon: Pokemon,
-    override val form: TemporaryForm
-) : Cancelable(), FormEvent {
-    val context = mutableMapOf(
-        "pokemon" to pokemon.struct,
-        "form" to StringValue(form.formOnlyShowdownId())
-    )
-
-    val functions = moLangFunctionMap(cancelFunc)
-}

common/src/main/kotlin/com/cobblemon/mod/common/api/events/pokemon/form/FormCompleteEvent.kt

@@ -1,34 +0,0 @@
-/*
- * Copyright (C) 2023 Cobblemon Contributors
- *
- * This Source Code Form is subject to the terms of the Mozilla Public
- * License, v. 2.0. If a copy of the MPL was not distributed with this
- * file, You can obtain one at https://mozilla.org/MPL/2.0/.
- */
-
-package com.cobblemon.mod.common.api.events.pokemon.form
-
-import com.bedrockk.molang.runtime.value.StringValue
-import com.cobblemon.mod.common.pokemon.Pokemon
-import com.cobblemon.mod.common.pokemon.transformation.form.TemporaryForm
-
-/**
- * Fired after a temporary form change finishes.
- *
- * @param pokemon The [Pokemon] resulting from the form change.
- * @param form The [TemporaryForm] that was used.
- *
- * @author Hiroku
- * @since June 3rd, 2026
- */
-data class FormCompleteEvent(
-    /** The [Pokemon] that did the form change. */
-    override val pokemon: Pokemon,
-    /** The [TemporaryForm] that was used. */
-    override val form: TemporaryForm
-) : FormEvent {
-    val context = mutableMapOf(
-        "pokemon" to pokemon.struct,
-        "form" to StringValue(form.formOnlyShowdownId())
-    )
-}

common/src/main/kotlin/com/cobblemon/mod/common/api/events/pokemon/form/FormDisplayEvent.kt

@@ -1,37 +0,0 @@
-/*
- * Copyright (C) 2023 Cobblemon Contributors
- *
- * This Source Code Form is subject to the terms of the Mozilla Public
- * License, v. 2.0. If a copy of the MPL was not distributed with this
- * file, You can obtain one at https://mozilla.org/MPL/2.0/.
- */
-
-package com.cobblemon.mod.common.api.events.pokemon.form
-
-import com.bedrockk.molang.runtime.value.StringValue
-import com.cobblemon.mod.common.pokemon.Pokemon
-import com.cobblemon.mod.common.pokemon.transformation.form.FormDisplay
-import com.cobblemon.mod.common.pokemon.transformation.form.TemporaryForm
-
-/**
- * Fired before a form is sent to clients. For modifications on the actual output when they accept it modify
- * the [display] directly.
- *
- * @param pokemon The [Pokemon] that will change form if this proposition is accepted.
- * @param display The current [FormDisplay] the client will see.
- * @param form The [TemporaryForm] being used.
- *
- * @author Hiroku
- * @since June 3rd, 2026
- */
-data class FormDisplayEvent(
-    override val pokemon: Pokemon,
-    var display: FormDisplay,
-    override val form: TemporaryForm
-) : FormEvent {
-    val context = mutableMapOf(
-        "pokemon" to pokemon.struct,
-        "display" to display.struct,
-        "form" to StringValue(form.formOnlyShowdownId())
-    )
-}

common/src/main/kotlin/com/cobblemon/mod/common/api/events/pokemon/form/FormEvent.kt

@@ -1,22 +0,0 @@
-/*
- * Copyright (C) 2023 Cobblemon Contributors
- *
- * This Source Code Form is subject to the terms of the Mozilla Public
- * License, v. 2.0. If a copy of the MPL was not distributed with this
- * file, You can obtain one at https://mozilla.org/MPL/2.0/.
- */
-
-package com.cobblemon.mod.common.api.events.pokemon.form
-
-import com.cobblemon.mod.common.pokemon.Pokemon
-import com.cobblemon.mod.common.pokemon.transformation.form.TemporaryForm
-
-/**
- * The root of the various [TemporaryForm]-related events.
- */
-interface FormEvent {
-    /** The Pokémon impacted in this event.*/
-    val pokemon: Pokemon
-    /*** The form triggering this event.*/
-    val form: TemporaryForm
-}

common/src/main/kotlin/com/cobblemon/mod/common/api/events/pokemon/form/FormTestedEvent.kt

@@ -1,47 +0,0 @@
-/*
- * Copyright (C) 2023 Cobblemon Contributors
- *
- * This Source Code Form is subject to the terms of the Mozilla Public
- * License, v. 2.0. If a copy of the MPL was not distributed with this
- * file, You can obtain one at https://mozilla.org/MPL/2.0/.
- */
-
-package com.cobblemon.mod.common.api.events.pokemon.form
-
-import com.bedrockk.molang.runtime.value.DoubleValue
-import com.bedrockk.molang.runtime.value.StringValue
-import com.cobblemon.mod.common.api.molang.MoLangFunctions.moLangFunctionMap
-import com.cobblemon.mod.common.pokemon.Pokemon
-import com.cobblemon.mod.common.pokemon.transformation.form.TemporaryForm
-import com.cobblemon.mod.common.util.getBoolean
-
-/**
- * An event fired when [TemporaryForm.test] has been performed.
- * The final state [result] will be the return value of the test function.
- *
- * @property pokemon The [Pokemon] being tested against.
- * @property form The [TemporaryForm] instance performing the test.
- * @property originalResult The base result from the Cobblemon implementation.
- * @property result The final value returned by [TemporaryForm.test].
- */
-data class FormTestedEvent(
-    override val pokemon: Pokemon,
-    override val form: TemporaryForm,
-    val originalResult: Boolean,
-) : FormEvent {
-    var result: Boolean = originalResult
-
-    val context = mutableMapOf(
-        "pokemon" to pokemon.struct,
-        "form" to StringValue(form.formOnlyShowdownId()),
-        "original_result" to DoubleValue(originalResult),
-    )
-
-    val functions = moLangFunctionMap(
-        "result" to { DoubleValue(result) },
-        "set_result" to {
-            result = it.getBoolean(0)
-            DoubleValue.ONE
-        }
-    )
-}

common/src/main/kotlin/com/cobblemon/mod/common/api/events/starter/StarterChosenEvent.kt

@@ -15,6 +15,7 @@ import com.cobblemon.mod.common.api.molang.MoLangFunctions.asMoLangValue
 import com.cobblemon.mod.common.api.molang.MoLangFunctions.moLangFunctionMap
 import com.cobblemon.mod.common.api.pokemon.PokemonProperties
 import com.cobblemon.mod.common.pokemon.Pokemon
+import com.cobblemon.mod.common.util.getPlayer
 import net.minecraft.server.level.ServerPlayer
 
 /**

common/src/main/kotlin/com/cobblemon/mod/common/api/events/storage/ChangePCBoxWallpaperEvent.kt

@@ -8,6 +8,7 @@
 
 package com.cobblemon.mod.common.api.events.storage
 
+import com.bedrockk.molang.runtime.value.DoubleValue
 import com.bedrockk.molang.runtime.value.StringValue
 import com.cobblemon.mod.common.api.events.Cancelable
 import com.cobblemon.mod.common.api.molang.MoLangFunctions.asMoLangValue

common/src/main/kotlin/com/cobblemon/mod/common/api/events/storage/ReleasePokemonEvent.kt

@@ -16,7 +16,9 @@ import com.cobblemon.mod.common.api.molang.MoLangFunctions.asMoLangValue
 import com.cobblemon.mod.common.api.molang.MoLangFunctions.moLangFunctionMap
 import com.cobblemon.mod.common.api.storage.PokemonStore
 import com.cobblemon.mod.common.pokemon.Pokemon
+import com.cobblemon.mod.common.util.getPlayer
 import net.minecraft.server.level.ServerPlayer
+import java.util.UUID
 
 /**
  * The base of the events around the release of Pokémon from pc or party.

common/src/main/kotlin/com/cobblemon/mod/common/api/fossil/Fossils.kt

@@ -14,7 +14,7 @@ import com.cobblemon.mod.common.api.data.JsonDataRegistry
 import com.cobblemon.mod.common.api.pokemon.PokemonProperties
 import com.cobblemon.mod.common.api.reactive.SimpleObservable
 import com.cobblemon.mod.common.net.messages.client.data.FossilRegistrySyncPacket
-import com.cobblemon.mod.common.pokemon.transformation.adapters.LegacyItemConditionWrapperAdapter
+import com.cobblemon.mod.common.pokemon.evolution.adapters.LegacyItemConditionWrapperAdapter
 import com.cobblemon.mod.common.util.adapters.IdentifierAdapter
 import com.cobblemon.mod.common.util.adapters.ItemLikeConditionAdapter
 import com.cobblemon.mod.common.util.adapters.pokemonPropertiesShortAdapter

common/src/main/kotlin/com/cobblemon/mod/common/api/interaction/PokemonInteractions.kt

@@ -13,13 +13,13 @@ import com.cobblemon.mod.common.api.conditional.RegistryLikeCondition
 import com.cobblemon.mod.common.api.data.JsonDataRegistry
 import com.cobblemon.mod.common.api.molang.ExpressionLike
 import com.cobblemon.mod.common.api.pokemon.PokemonProperties
-import com.cobblemon.mod.common.api.pokemon.transformation.requirement.TransformationRequirement
+import com.cobblemon.mod.common.api.pokemon.requirement.Requirement
 import com.cobblemon.mod.common.api.reactive.SimpleObservable
 import com.cobblemon.mod.common.entity.pokemon.PokemonEntity
 import com.cobblemon.mod.common.net.messages.client.data.PokemonInteractionsSyncPacket
-import com.cobblemon.mod.common.pokemon.transformation.adapters.CobblemonRequirementAdapter
-import com.cobblemon.mod.common.pokemon.transformation.adapters.LegacyItemConditionWrapperAdapter
-import com.cobblemon.mod.common.pokemon.transformation.requirements.PokemonPropertiesRequirement
+import com.cobblemon.mod.common.pokemon.adapters.CobblemonRequirementAdapter
+import com.cobblemon.mod.common.pokemon.evolution.adapters.LegacyItemConditionWrapperAdapter
+import com.cobblemon.mod.common.pokemon.requirements.PokemonPropertiesRequirement
 import com.cobblemon.mod.common.util.adapters.*
 import com.cobblemon.mod.common.util.cobblemonResource
 import com.google.gson.Gson
@@ -46,7 +46,7 @@ object PokemonInteractions : JsonDataRegistry<PokemonInteractionSet> {
         .registerTypeAdapter(ResourceLocation::class.java, IdentifierAdapter)
         .registerTypeAdapter(PokemonProperties::class.java, pokemonPropertiesShortAdapter)
         .registerTypeAdapter(ItemPredicate::class.java, LegacyItemConditionWrapperAdapter)
-        .registerTypeAdapter(TransformationRequirement::class.java, CobblemonRequirementAdapter)
+        .registerTypeAdapter(Requirement::class.java, CobblemonRequirementAdapter)
         .registerTypeAdapter(InteractionEffect::class.java, InteractionEffectAdapter)
         .registerTypeAdapter(ExpressionLike::class.java, ExpressionLikeAdapter)
         .registerTypeAdapter(TypeToken.getParameterized(RegistryLikeCondition::class.java, Biome::class.java).type, BiomeLikeConditionAdapter)

common/src/main/kotlin/com/cobblemon/mod/common/api/interaction/PokemonInteration.kt

@@ -12,16 +12,11 @@ import com.bedrockk.molang.runtime.MoLangRuntime
 import com.cobblemon.mod.common.api.molang.ExpressionLike
 import com.cobblemon.mod.common.api.molang.MoLangFunctions.asMoLangValue
 import com.cobblemon.mod.common.api.molang.MoLangFunctions.setup
-import com.cobblemon.mod.common.api.pokemon.transformation.requirement.TransformationRequirement
+import com.cobblemon.mod.common.api.pokemon.requirement.Requirement
 import com.cobblemon.mod.common.entity.pokemon.PokemonEntity
 import com.cobblemon.mod.common.net.messages.client.sound.UnvalidatedPlaySoundS2CPacket
-import com.cobblemon.mod.common.pokemon.transformation.adapters.CobblemonRequirementAdapter
-import com.cobblemon.mod.common.util.asExpressionLike
-import com.cobblemon.mod.common.util.giveOrDropItemStack
-import com.cobblemon.mod.common.util.readExpressionLike
-import com.cobblemon.mod.common.util.withPlayerValue
-import com.cobblemon.mod.common.util.withQueryValue
-import com.cobblemon.mod.common.util.writeExpressionLike
+import com.cobblemon.mod.common.pokemon.adapters.CobblemonRequirementAdapter
+import com.cobblemon.mod.common.util.*
 import com.google.gson.annotations.SerializedName
 import net.minecraft.core.registries.Registries
 import net.minecraft.network.FriendlyByteBuf
@@ -34,7 +29,7 @@ import net.minecraft.world.entity.item.ItemEntity
 import net.minecraft.world.item.ItemStack
 
 data class PokemonInteractionSet(
-    val requirements: List<TransformationRequirement> = listOf(),
+    val requirements: List<Requirement> = listOf(),
     val interactions: List<PokemonInteraction> = listOf(),
 ) {
     fun encode(buffer: FriendlyByteBuf) {
@@ -56,7 +51,7 @@ data class PokemonInteractionSet(
 }
 
 data class PokemonInteraction(
-    val requirements: List<TransformationRequirement> = listOf(),
+    val requirements: List<Requirement> = listOf(),
     val effects: List<InteractionEffect> = listOf(),
     val cooldown: ExpressionLike = "0".asExpressionLike()
 ) {

common/src/main/kotlin/com/cobblemon/mod/common/api/interaction/RequestManager.kt

@@ -74,7 +74,7 @@ abstract class RequestManager<T : ServerPlayerActionRequest> {
         ?: this.getInboundRequest(receiver.uuid, requestID)
 
     /** Determines whether [player] can receive a [T]. */
-    open fun isBusy(player: ServerPlayer): Boolean = player.isBusy() || player.isPartyBusy()
+    open fun isBusy(player: ServerPlayer): Boolean = player.isInBattle() || player.isTrading() || player.party().find { it.entity?.isBusy == true } != null
 
     /** Determines if the [target] is a valid interaction request target. */
     abstract fun isValidInteraction(player: ServerPlayer, target: ServerPlayer): Boolean

common/src/main/kotlin/com/cobblemon/mod/common/api/item/HeldItems.kt

@@ -9,7 +9,6 @@
 package com.cobblemon.mod.common.api.item
 
 import com.cobblemon.mod.common.api.data.DataRegistry
-import com.cobblemon.mod.common.api.data.ShowdownIdentifiable
 import com.cobblemon.mod.common.api.reactive.SimpleObservable
 import com.cobblemon.mod.common.battles.runner.ShowdownService
 import com.cobblemon.mod.common.pokemon.helditem.CobblemonHeldItemManager
@@ -30,11 +29,9 @@ object HeldItems : DataRegistry {
     // val heldItems = PrioritizedList<BagItemLike>()
     internal val heldItemsScripts = mutableMapOf<String, String>() // showdown item ID to JavaScript
     val showdownItems = hashSetOf<String>()
-    val megaStones = hashMapOf<String, String>()
 
     override fun reload(manager: ResourceManager) {
         heldItemsScripts.clear()
-        megaStones.clear()
         ShowdownService.service.resetRegistryData("heldItem")
         manager.listResources("held_items") { it.path.endsWith(".js") }.forEach { (identifier, resource) ->
             resource.open().use { stream ->
@@ -51,9 +48,6 @@ object HeldItems : DataRegistry {
         for (i in 0 until itemsJson.size()) {
             val jsItem = itemsJson[i].asJsonObject
             showdownItems += jsItem.get("id").asString
-            if (jsItem.has("megaEvolves")) {
-                megaStones[jsItem.get("id").asString] = ShowdownIdentifiable.REGEX.replace(jsItem.get("megaEvolves").asString.lowercase(), "")
-            }
         }
 
         CobblemonHeldItemManager.load()

common/src/main/kotlin/com/cobblemon/mod/common/api/molang/MoLangFunctions.kt

@@ -21,9 +21,34 @@ import com.cobblemon.mod.common.api.battles.interpreter.BattleMessage
 import com.cobblemon.mod.common.api.battles.model.PokemonBattle
 import com.cobblemon.mod.common.api.battles.model.actor.BattleActor
 import com.cobblemon.mod.common.api.drop.DropEntry
-import com.cobblemon.mod.common.api.molang.function.*
+import com.cobblemon.mod.common.api.molang.function.BattleActorMoLangFunctions
+import com.cobblemon.mod.common.api.molang.function.BattleMessageMoLangFunctions
+import com.cobblemon.mod.common.api.molang.function.BattleMoLangFunctions
+import com.cobblemon.mod.common.api.molang.function.BiomeMoLangFunctions
+import com.cobblemon.mod.common.api.molang.function.BlockMoLangFunctions
+import com.cobblemon.mod.common.api.molang.function.DimensionTypeMoLangFunctions
+import com.cobblemon.mod.common.api.molang.function.DropEntryMoLangFunctions
+import com.cobblemon.mod.common.api.molang.function.EntityMoLangFunctions
+import com.cobblemon.mod.common.api.molang.function.EvolutionMoLangFunctions
+import com.cobblemon.mod.common.api.molang.function.GeneralMoLangFunctions
+import com.cobblemon.mod.common.api.molang.function.ItemStackMoLangFunctions
+import com.cobblemon.mod.common.api.molang.function.LivingEntityMoLangFunctions
+import com.cobblemon.mod.common.api.molang.function.NPCMoLangFunctions
+import com.cobblemon.mod.common.api.molang.function.PCMoLangFunctions
+import com.cobblemon.mod.common.api.molang.function.PartyMoLangFunctions
+import com.cobblemon.mod.common.api.molang.function.PlayerMoLangFunctions
+import com.cobblemon.mod.common.api.molang.function.PokedexMoLangFunctions
+import com.cobblemon.mod.common.api.molang.function.PokemonEntityMoLangFunctions
+import com.cobblemon.mod.common.api.molang.function.PokemonMoLangFunctions
+import com.cobblemon.mod.common.api.molang.function.PokemonPropertiesMoLangFunctions
+import com.cobblemon.mod.common.api.molang.function.PokemonStoreMoLangFunctions
+import com.cobblemon.mod.common.api.molang.function.ServerMoLangFunctions
+import com.cobblemon.mod.common.api.molang.function.SpawnablePositionMoLangFunctions
+import com.cobblemon.mod.common.api.molang.function.SpeciesMoLangFunctions
+import com.cobblemon.mod.common.api.molang.function.WorldMoLangFunctions
 import com.cobblemon.mod.common.api.pokedex.AbstractPokedexManager
 import com.cobblemon.mod.common.api.pokemon.PokemonProperties
+import com.cobblemon.mod.common.api.pokemon.evolution.Evolution
 import com.cobblemon.mod.common.api.scripting.CobblemonScripts
 import com.cobblemon.mod.common.api.spawning.position.SpawnablePosition
 import com.cobblemon.mod.common.api.storage.PokemonStore
@@ -33,10 +58,8 @@ import com.cobblemon.mod.common.entity.npc.NPCEntity
 import com.cobblemon.mod.common.entity.pokemon.PokemonEntity
 import com.cobblemon.mod.common.pokemon.Pokemon
 import com.cobblemon.mod.common.pokemon.Species
-import com.cobblemon.mod.common.pokemon.transformation.evolution.Evolution
 import com.cobblemon.mod.common.util.effectiveName
 import com.mojang.datafixers.util.Either
-import java.util.function.Function
 import net.minecraft.core.Holder
 import net.minecraft.core.Registry
 import net.minecraft.core.RegistryAccess
@@ -61,6 +84,7 @@ import net.minecraft.world.level.biome.Biome
 import net.minecraft.world.level.block.Block
 import net.minecraft.world.level.dimension.DimensionType
 import net.minecraft.world.phys.Vec3
+import java.util.function.Function
 
 /**
  * Holds a bunch of useful MoLang trickery that can be used or extended in API

common/src/main/kotlin/com/cobblemon/mod/common/api/molang/function/BattleMoLangFunctions.kt

@@ -13,7 +13,7 @@ import com.bedrockk.molang.runtime.value.DoubleValue
 import com.bedrockk.molang.runtime.value.StringValue
 import com.cobblemon.mod.common.api.battles.model.PokemonBattle
 import com.cobblemon.mod.common.util.asArrayValue
-import java.util.UUID
+import java.util.*
 
 object BattleMoLangFunctions : AbstractMoLangFunctionHolder<PokemonBattle>() {
     override fun PokemonBattle.moLangFunctions(): MutableMap<String, (MoParams) -> Any> {

common/src/main/kotlin/com/cobblemon/mod/common/api/molang/function/EvolutionMoLangFunctions.kt

@@ -11,34 +11,31 @@ package com.cobblemon.mod.common.api.molang.function
 import com.bedrockk.molang.runtime.MoParams
 import com.bedrockk.molang.runtime.value.DoubleValue
 import com.cobblemon.mod.common.api.molang.MoLangFunctions.asMoLangValue
-import com.cobblemon.mod.common.api.pokemon.transformation.Transformation
-import com.cobblemon.mod.common.pokemon.transformation.evolution.Evolution
-import com.cobblemon.mod.common.pokemon.transformation.triggers.ItemInteractionTrigger
-import com.cobblemon.mod.common.pokemon.transformation.triggers.LevelUpTrigger
-import com.cobblemon.mod.common.pokemon.transformation.triggers.TradeTrigger
+import com.cobblemon.mod.common.api.pokemon.evolution.Evolution
+import com.cobblemon.mod.common.pokemon.evolution.variants.ItemInteractionEvolution
+import com.cobblemon.mod.common.pokemon.evolution.variants.LevelUpEvolution
+import com.cobblemon.mod.common.pokemon.evolution.variants.TradeEvolution
 
-object EvolutionMoLangFunctions : AbstractMoLangFunctionHolder<Transformation>() {
-    override fun Transformation.moLangFunctions(): MutableMap<String, (MoParams) -> Any> {
+object EvolutionMoLangFunctions : AbstractMoLangFunctionHolder<Evolution>() {
+    override fun Evolution.moLangFunctions(): MutableMap<String, (MoParams) -> Any> {
         val evolution = this
         val functions = hashMapOf<String, (MoParams) -> Any>()
 
-        functions["reevaluate"] = { DoubleValue(evolution.reevaluate) }
+        functions["result"] = { evolution.result.asMoLangValue() }
         functions["is_optional"] = { DoubleValue(evolution.optional) }
+        functions["consumes_held_item"] = { DoubleValue(evolution.consumeHeldItem) }
 
-        if (evolution is Evolution) {
-            functions["result"] = { evolution.result.asMoLangValue() }
-            when (evolution.trigger) {
-                is LevelUpTrigger -> {
-                    functions["is_level_up"] = { DoubleValue.ONE }
-                }
+        when (evolution) {
+            is LevelUpEvolution -> {
+                functions["is_level_up"] = { DoubleValue.ONE }
+            }
 
-                is TradeTrigger -> {
-                    functions["is_trade"] = { DoubleValue.ONE }
-                }
+            is TradeEvolution -> {
+                functions["is_trade"] = { DoubleValue.ONE }
+            }
 
-                is ItemInteractionTrigger -> {
-                    functions["is_item"] = { DoubleValue.ONE }
-                }
+            is ItemInteractionEvolution -> {
+                functions["is_item"] = { DoubleValue.ONE }
             }
         }
 

common/src/main/kotlin/com/cobblemon/mod/common/api/molang/function/GeneralMoLangFunctions.kt

@@ -45,6 +45,11 @@ object GeneralMoLangFunctions {
     val functions: MutableMap<String, (MoParams) -> Any> = mutableMapOf()
 
     init {
+        functions["format"] = { params ->
+            val value = params.get<MoValue>(0).asDouble()
+            val decimals = params.get<MoValue>(1).asDouble().toInt().coerceIn(0, 10)
+            StringValue(String.format("%.${decimals}f", value))
+        }
         functions["print"] = { params ->
             val message = params.get<MoValue>(0).asString()
             LOGGER.info(message)

common/src/main/kotlin/com/cobblemon/mod/common/api/molang/function/PokemonMoLangFunctions.kt

@@ -445,7 +445,7 @@ object PokemonMoLangFunctions : AbstractMoLangFunctionHolder<Pokemon>() {
             val idx = params.getInt(0)
             val evolution =
                 if (idx >= 0) pokemon.evolutions.elementAtOrNull(idx) else return@forceEvolve DoubleValue.ZERO
-            evolution?.perform(pokemon)
+            evolution?.forceEvolve(pokemon)
             StringValue(evolution.toString())
         }
 

common/src/main/kotlin/com/cobblemon/mod/common/api/molangui/GuiMode.kt

@@ -0,0 +1,18 @@
+/*
+ * Copyright (C) 2023 Cobblemon Contributors
+ *
+ * This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at https://mozilla.org/MPL/2.0/.
+ */
+
+package com.cobblemon.mod.common.api.molangui
+
+enum class GuiMode {
+    OVERLAY,
+    SCREEN;
+
+    companion object {
+        fun fromString(value: String): GuiMode? = entries.firstOrNull { it.name.equals(value, ignoreCase = true) }
+    }
+}

common/src/main/kotlin/com/cobblemon/mod/common/api/molangui/MolangUiActionRegistry.kt

@@ -0,0 +1,50 @@
+/*
+ * Copyright (C) 2023 Cobblemon Contributors
+ *
+ * This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at https://mozilla.org/MPL/2.0/.
+ */
+
+package com.cobblemon.mod.common.api.molangui
+
+import com.cobblemon.mod.common.api.scripting.CobblemonScripts
+import java.util.concurrent.ConcurrentHashMap
+
+object MolangUiActionRegistry {
+    private val handlers = ConcurrentHashMap<ActionKey, MolangUiActionHandler>()
+
+    fun register(key: ActionKey, handler: MolangUiActionHandler) {
+        check(handlers.putIfAbsent(key, handler) == null) { "Molang UI action '$key' is already registered" }
+    }
+
+    fun unregister(key: ActionKey): Boolean = handlers.remove(key) != null
+
+    internal fun dispatch(
+        session: MolangUiSession,
+        action: ActionKey,
+        parameters: Map<String, ParameterValue>
+    ) {
+        val definition = session.contract.actions[action]
+            ?: throw IllegalArgumentException("undeclared action '${action.value}'")
+        val registered = handlers[action]
+        if (registered != null) {
+            registered.handle(MolangUiActionContext(session, session.player, parameters))
+            return
+        }
+        val scriptId = definition.handler
+            ?: throw IllegalStateException("action '${action.value}' has no registered handler")
+        val script = CobblemonScripts.scripts[scriptId]
+            ?: throw IllegalStateException("Molang UI action script '$scriptId' was not loaded")
+        val runtime = MolangUiServerRuntimeFactory.create(session)
+        parameters.forEach { (name, value) -> runtime.environment.setSimpleVariable(name, value.asMoLangValue()) }
+        script.resolve(runtime, emptyMap())
+    }
+
+    internal fun executeOnOpen(session: MolangUiSession) {
+        val scriptId = session.contract.onOpen ?: return
+        val script = CobblemonScripts.scripts[scriptId]
+            ?: throw IllegalStateException("Molang UI on_open script '$scriptId' was not loaded")
+        script.resolve(MolangUiServerRuntimeFactory.create(session), emptyMap())
+    }
+}

common/src/main/kotlin/com/cobblemon/mod/common/api/molangui/MolangUiContractRegistry.kt

@@ -0,0 +1,201 @@
+/*
+ * Copyright (C) 2023 Cobblemon Contributors
+ *
+ * This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at https://mozilla.org/MPL/2.0/.
+ */
+
+package com.cobblemon.mod.common.api.molangui
+
+import com.google.gson.JsonArray
+import com.cobblemon.mod.common.api.data.DataRegistry
+import com.cobblemon.mod.common.api.molangui.container.CollectionConfig
+import com.cobblemon.mod.common.api.molangui.container.CollectionSource
+import com.cobblemon.mod.common.api.molangui.container.CloseItemsPolicy
+import com.cobblemon.mod.common.api.molangui.container.ItemFilterEntry
+import com.cobblemon.mod.common.api.molangui.container.ShiftClickRule
+import com.cobblemon.mod.common.api.molangui.container.SlotLayout
+import com.cobblemon.mod.common.api.reactive.SimpleObservable
+import com.cobblemon.mod.common.net.messages.client.molangui.MolangUiCompatibilityRequestPacket
+import com.cobblemon.mod.common.util.cobblemonResource
+import com.google.gson.JsonElement
+import com.google.gson.JsonObject
+import com.google.gson.JsonParser
+import net.minecraft.resources.ResourceLocation
+import net.minecraft.core.registries.BuiltInRegistries
+import net.minecraft.server.level.ServerPlayer
+import net.minecraft.server.packs.PackType
+import net.minecraft.server.packs.resources.ResourceManager
+import com.cobblemon.mod.common.Cobblemon
+import java.util.concurrent.atomic.AtomicLong
+
+object MolangUiContractRegistry : DataRegistry {
+    override val id = cobblemonResource("molang_ui_contracts")
+    override val type = PackType.SERVER_DATA
+    override val observable = SimpleObservable<MolangUiContractRegistry>()
+    private val contracts = linkedMapOf<ResourceLocation, MolangUiContract>()
+    private val parseFailures = AtomicLong()
+    private const val DIRECTORY = "molang_ui"
+
+    override fun reload(manager: ResourceManager) {
+        val next = linkedMapOf<ResourceLocation, MolangUiContract>()
+        manager.listResources(DIRECTORY) { it.path.endsWith(".json") }.forEach { (location, resource) ->
+            val id = ResourceLocation.fromNamespaceAndPath(
+                location.namespace,
+                location.path.removePrefix("$DIRECTORY/").removeSuffix(".json")
+            )
+            try {
+                val json = resource.openAsReader().use { JsonParser.parseReader(it).asJsonObject }
+                next[id] = parse(id, json)
+            } catch (error: Exception) {
+                parseFailures.incrementAndGet()
+                Cobblemon.LOGGER.error("Rejected Molang UI contract '$location': ${error.message}")
+            }
+        }
+        require(next.size <= MolangUiPacketLimits.MAX_CONTRACTS) {
+            "Molang UI contract count exceeds ${MolangUiPacketLimits.MAX_CONTRACTS}"
+        }
+        contracts.clear()
+        contracts.putAll(next)
+        Cobblemon.LOGGER.info("Loaded ${contracts.size} validated Molang UI contracts")
+        observable.emit(this)
+    }
+
+    override fun sync(player: ServerPlayer) {
+        MolangUiCompatibilityRequestPacket(versions()).sendToPlayer(player)
+    }
+
+    internal fun parse(
+        id: ResourceLocation,
+        json: JsonObject,
+        itemExists: (ResourceLocation) -> Boolean = BuiltInRegistries.ITEM::containsKey
+    ): MolangUiContract {
+        require(!json.has("blocks_input")) { "blocks_input is unsupported; input handling is determined by mode" }
+        val formatVersion = json.get("format_version").requireUiInt("format_version")
+        require(formatVersion == MOLANG_UI_FORMAT_VERSION) { "unsupported format_version $formatVersion" }
+        val contractVersion = json.get("contract_version").requireUiString("contract_version")
+        MolangUiPacketLimits.requireIdentifier(contractVersion, "contract_version")
+        val mode = GuiMode.fromString(json.get("mode").requireUiString("mode"))
+            ?: throw IllegalArgumentException("unknown mode '${json.get("mode").asString}'")
+        val parameters = parseParameters(json.getAsJsonObject("parameters"))
+        val actions = parseActions(json.getAsJsonObject("actions"))
+        val collections = parseCollections(json.getAsJsonObject("collections"), itemExists)
+        val shiftRules = parseShiftRules(json.getAsJsonArray("shift_click_rules"), collections.keys)
+        val closePolicy = json.get("on_close_items")?.requireUiString("on_close_items")?.let { raw ->
+            CloseItemsPolicy.fromId(raw) ?: throw IllegalArgumentException("unknown on_close_items policy '$raw'")
+        } ?: CloseItemsPolicy.RETURN
+        return MolangUiContract(
+            id, formatVersion, contractVersion, mode, parameters, actions,
+            json.get("on_open")?.requireUiString("on_open")?.let { ResourceLocation.tryParse(it) ?: error("invalid on_open script id") },
+            collections, shiftRules, closePolicy,
+            json.get("exclusive")?.requireUiBoolean("exclusive") ?: false
+        )
+    }
+
+    private fun parseParameters(json: JsonObject?): Map<String, ParameterDefinition> {
+        require((json?.size() ?: 0) <= MolangUiPacketLimits.MAX_ACTION_FIELDS) { "too many parameters" }
+        return json?.entrySet()?.associate { (name, element) ->
+            MolangUiParameters.requireName(name)
+            val obj = element.asJsonObject
+            val type = ParameterType.fromId(obj.get("type").requireUiString("parameters.$name.type"))
+                ?: throw IllegalArgumentException("unknown type for parameter '$name'")
+            val default = obj.get("default")?.let { parseDefault(type, it, "parameters.$name.default") }
+            name to ParameterDefinition(type, obj.get("required")?.requireUiBoolean("parameters.$name.required") ?: (default == null), default)
+        }?.toMap() ?: emptyMap()
+    }
+
+    private fun parseDefault(type: ParameterType, element: JsonElement, path: String): ParameterDefault {
+        if (element.isJsonObject && element.asJsonObject.has("molang")) {
+            require(element.asJsonObject.size() == 1) { "expression '$path' contains unknown fields" }
+            return ParameterDefault.Molang(element.asJsonObject.get("molang").requireUiString("$path.molang"))
+        }
+        val value = when (type) {
+            ParameterType.STRING -> ParameterValue.StringValue(element.requireUiString(path))
+            ParameterType.NUMBER -> ParameterValue.NumberValue(element.requireUiNumber(path))
+            ParameterType.BOOLEAN -> ParameterValue.BooleanValue(element.requireUiBoolean(path))
+            ParameterType.VEC3 -> {
+                require(element.isJsonArray && element.asJsonArray.size() == 3) { "'$path' must be a three-number array" }
+                ParameterValue.Vec3Value(
+                    element.asJsonArray[0].requireUiNumber("$path[0]"),
+                    element.asJsonArray[1].requireUiNumber("$path[1]"),
+                    element.asJsonArray[2].requireUiNumber("$path[2]")
+                )
+            }
+        }
+        MolangUiPacketLimits.requireValue(value.asWireValue(), path)
+        return ParameterDefault.Literal(value)
+    }
+
+    private fun parseActions(json: JsonObject?): Map<ActionKey, ActionDefinition> {
+        val result = json?.entrySet()?.associate { (name, element) ->
+            val key = ActionKey(name)
+            val obj = element.asJsonObject
+            val handler = obj.get("handler")?.requireUiString("actions.$name.handler")?.let { ResourceLocation.tryParse(it) ?: error("invalid handler for action '$name'") }
+            val params = obj.getAsJsonObject("parameters")?.entrySet()?.associate { (paramName, typeElement) ->
+                MolangUiPacketLimits.requireIdentifier(paramName, "action parameter name")
+                paramName to (ParameterType.fromId(typeElement.requireUiString("actions.$name.parameters.$paramName"))
+                    ?: throw IllegalArgumentException("unknown type for action parameter '$name.$paramName'"))
+            }?.toMap() ?: emptyMap()
+            require(params.size <= MolangUiPacketLimits.MAX_ACTION_FIELDS) { "action '$name' has too many parameters" }
+            key to ActionDefinition(handler, params)
+        }?.toMap() ?: emptyMap()
+        require(result.size <= MolangUiPacketLimits.MAX_ACTION_FIELDS) { "contract has too many actions" }
+        return result
+    }
+
+    private fun parseCollections(
+        json: JsonObject?,
+        itemExists: (ResourceLocation) -> Boolean
+    ): Map<String, CollectionConfig> {
+        require((json?.size() ?: 0) <= MolangUiPacketLimits.MAX_CONTRACTS) { "too many container collections" }
+        return json?.entrySet()?.associate { (name, element) ->
+            MolangUiPacketLimits.requireIdentifier(name, "collection name")
+            val obj = element.asJsonObject
+            val source = CollectionSource.fromId(obj.get("source")?.requireUiString("collections.$name.source") ?: "session")
+                ?: throw IllegalArgumentException("unknown source for collection '$name'")
+            val filters = obj.getAsJsonArray("allowed_items")?.map { raw ->
+                val filter = ItemFilterEntry.parse(raw.requireUiString("collections.$name.allowed_items"))
+                    ?: throw IllegalArgumentException("invalid item filter '${raw.asString}' in '$name'")
+                if (filter is ItemFilterEntry.Item) require(itemExists(filter.id)) {
+                    "unknown item '${filter.id}' in collection '$name'"
+                }
+                filter
+            }?.toList() ?: emptyList()
+            val layoutObj = obj.getAsJsonObject("layout") ?: throw IllegalArgumentException("collection '$name' is missing layout")
+            val offset = layoutObj.pair("offset", 0, 0)
+            val grid = layoutObj.pair("grid_dimensions", 1, 1)
+            val slotSize = layoutObj.pair("slot_size", 18, 18)
+            val spacing = layoutObj.pair("slot_spacing", 0, 0)
+            val layout = SlotLayout(offset.first, offset.second, grid.first, grid.second, slotSize.first, slotSize.second, spacing.first, spacing.second)
+            name to CollectionConfig(
+                obj.get("size").requireUiInt("collections.$name.size"), filters,
+                obj.get("take_only")?.requireUiBoolean("collections.$name.take_only") ?: false, source,
+                obj.getAsJsonArray("slots")?.map { it.requireUiInt("collections.$name.slots") }?.toList(), layout
+            )
+        }?.toMap() ?: emptyMap()
+    }
+
+    private fun parseShiftRules(array: JsonArray?, collections: Set<String>): List<ShiftClickRule> =
+        array?.map { element ->
+            val obj = element.asJsonObject
+            val from = obj.stringList("from")
+            val to = obj.stringList("to")
+            val valid = collections + ShiftClickRule.PLAYER_SIDE_NAMES
+            require(from.isNotEmpty() && to.isNotEmpty() && (from + to).all { it in valid }) { "shift-click rule references an unknown collection" }
+            ShiftClickRule(from, to)
+        }?.toList() ?: emptyList()
+
+    fun getContract(id: ResourceLocation): MolangUiContract? = contracts[id]
+    fun getAllContracts(): Map<ResourceLocation, MolangUiContract> = contracts.toMap()
+    fun versions(): Map<ResourceLocation, String> = contracts.mapValues { it.value.contractVersion }
+    fun parseFailureCount(): Long = parseFailures.get()
+}
+
+private fun JsonObject.pair(name: String, first: Int, second: Int): Pair<Int, Int> {
+    val value = getAsJsonArray(name) ?: return first to second
+    require(value.size() == 2) { "'$name' must have two entries" }
+    return value[0].requireUiInt(name) to value[1].requireUiInt(name)
+}
+private fun JsonObject.stringList(name: String): List<String> = getAsJsonArray(name)?.map { it.requireUiString(name) }?.toList()
+    ?: throw IllegalArgumentException("missing array '$name'")

common/src/main/kotlin/com/cobblemon/mod/common/api/molangui/MolangUiDefinition.kt

@@ -0,0 +1,24 @@
+/*
+ * Copyright (C) 2023 Cobblemon Contributors
+ *
+ * This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at https://mozilla.org/MPL/2.0/.
+ */
+
+package com.cobblemon.mod.common.api.molangui
+
+import com.cobblemon.mod.common.api.molangui.widget.WidgetDefinition
+import net.minecraft.resources.ResourceLocation
+
+data class MolangUiDefinition(
+    val guiId: ResourceLocation,
+    val formatVersion: Int,
+    val contractVersion: String,
+    val mode: GuiMode,
+    val parameters: Map<String, ParameterType>,
+    val actions: Set<ActionKey>,
+    val exclusive: Boolean,
+    val root: WidgetDefinition,
+    val variables: Map<String, Double>
+)

common/src/main/kotlin/com/cobblemon/mod/common/api/molangui/MolangUiDiagnostics.kt

@@ -0,0 +1,26 @@
+/*
+ * Copyright (C) 2023 Cobblemon Contributors
+ *
+ * This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at https://mozilla.org/MPL/2.0/.
+ */
+
+package com.cobblemon.mod.common.api.molangui
+
+import java.util.concurrent.atomic.AtomicLong
+
+object MolangUiDiagnostics {
+    private val activeSessions = AtomicLong()
+    private val rejectedActions = AtomicLong()
+    private val compatibilityFailures = AtomicLong()
+
+    internal fun sessionOpened() { activeSessions.incrementAndGet() }
+    internal fun sessionClosed() { activeSessions.updateAndGet { value -> (value - 1).coerceAtLeast(0) } }
+    internal fun actionRejected() { rejectedActions.incrementAndGet() }
+    internal fun compatibilityFailures(count: Long) { compatibilityFailures.addAndGet(count) }
+
+    fun snapshot() = Snapshot(activeSessions.get(), rejectedActions.get(), compatibilityFailures.get(), MolangUiContractRegistry.parseFailureCount())
+
+    data class Snapshot(val activeSessions: Long, val rejectedActions: Long, val compatibilityFailures: Long, val parseFailures: Long)
+}

common/src/main/kotlin/com/cobblemon/mod/common/api/molangui/MolangUiJson.kt

@@ -0,0 +1,35 @@
+/*
+ * Copyright (C) 2023 Cobblemon Contributors
+ *
+ * This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at https://mozilla.org/MPL/2.0/.
+ */
+
+package com.cobblemon.mod.common.api.molangui
+
+import com.google.gson.JsonElement
+
+internal fun JsonElement?.requireUiString(path: String): String {
+    require(this != null && isJsonPrimitive && asJsonPrimitive.isString) { "'$path' must be a string" }
+    return asString
+}
+
+internal fun JsonElement?.requireUiBoolean(path: String): Boolean {
+    require(this != null && isJsonPrimitive && asJsonPrimitive.isBoolean) { "'$path' must be a boolean" }
+    return asBoolean
+}
+
+internal fun JsonElement?.requireUiNumber(path: String): Double {
+    require(this != null && isJsonPrimitive && asJsonPrimitive.isNumber) { "'$path' must be a number" }
+    return asDouble.also { require(it.isFinite()) { "'$path' must be finite" } }
+}
+
+internal fun JsonElement?.requireUiInt(path: String): Int {
+    require(this != null && isJsonPrimitive && asJsonPrimitive.isNumber) { "'$path' must be an integer" }
+    return try {
+        asBigDecimal.intValueExact()
+    } catch (error: ArithmeticException) {
+        throw IllegalArgumentException("'$path' must be an integer in the 32-bit range", error)
+    }
+}

common/src/main/kotlin/com/cobblemon/mod/common/api/molangui/MolangUiModels.kt

@@ -0,0 +1,151 @@
+/*
+ * Copyright (C) 2023 Cobblemon Contributors
+ *
+ * This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at https://mozilla.org/MPL/2.0/.
+ */
+
+package com.cobblemon.mod.common.api.molangui
+
+import com.cobblemon.mod.common.api.molangui.container.SlotLayout
+import com.cobblemon.mod.common.api.molangui.container.CollectionConfig
+import com.cobblemon.mod.common.api.molangui.container.CloseItemsPolicy
+import com.cobblemon.mod.common.api.molangui.container.ShiftClickRule
+import net.minecraft.core.BlockPos
+import net.minecraft.resources.ResourceLocation
+import net.minecraft.server.level.ServerPlayer
+import java.util.UUID
+
+const val MOLANG_UI_FORMAT_VERSION = 1
+
+enum class ParameterType(val id: String) {
+    STRING("string"),
+    NUMBER("number"),
+    BOOLEAN("boolean"),
+    VEC3("vec3");
+
+    companion object {
+        fun fromId(id: String): ParameterType? = entries.firstOrNull { it.id == id }
+    }
+}
+
+sealed interface ParameterValue {
+    val type: ParameterType
+    fun asWireValue(): String
+
+    data class StringValue(val value: String) : ParameterValue {
+        override val type = ParameterType.STRING
+        override fun asWireValue() = value
+    }
+
+    data class NumberValue(val value: Double) : ParameterValue {
+        init { require(value.isFinite()) { "number parameters must be finite" } }
+        override val type = ParameterType.NUMBER
+        override fun asWireValue() = value.toString()
+    }
+
+    data class BooleanValue(val value: Boolean) : ParameterValue {
+        override val type = ParameterType.BOOLEAN
+        override fun asWireValue() = value.toString()
+    }
+
+    data class Vec3Value(val x: Double, val y: Double, val z: Double) : ParameterValue {
+        init { require(x.isFinite() && y.isFinite() && z.isFinite()) { "vec3 parameters must be finite" } }
+        override val type = ParameterType.VEC3
+        override fun asWireValue() = "$x,$y,$z"
+    }
+
+    companion object {
+        fun parse(type: ParameterType, value: String): ParameterValue? = when (type) {
+            ParameterType.STRING -> StringValue(value)
+            ParameterType.NUMBER -> value.toDoubleOrNull()?.takeIf(Double::isFinite)?.let(::NumberValue)
+            ParameterType.BOOLEAN -> value.toBooleanStrictOrNull()?.let(::BooleanValue)
+            ParameterType.VEC3 -> value.split(',').takeIf { it.size == 3 }
+                ?.map { it.trim().toDoubleOrNull() }
+                ?.takeIf { it.all { part -> part != null && part.isFinite() } }
+                ?.let { Vec3Value(it[0]!!, it[1]!!, it[2]!!) }
+        }
+    }
+}
+
+data class ParameterDefinition(
+    val type: ParameterType,
+    val required: Boolean = true,
+    val default: ParameterDefault? = null
+)
+
+sealed interface ParameterDefault {
+    data class Literal(val value: ParameterValue) : ParameterDefault
+    data class Molang(val expression: String) : ParameterDefault
+}
+
+@JvmInline
+value class ActionKey(val value: String) {
+    init { require(value.isNotBlank() && value.length <= MolangUiPacketLimits.MAX_IDENTIFIER_LENGTH) }
+}
+
+data class ActionDefinition(
+    val handler: ResourceLocation? = null,
+    val parameters: Map<String, ParameterType> = emptyMap()
+)
+
+data class MolangUiContract(
+    val id: ResourceLocation,
+    val formatVersion: Int,
+    val contractVersion: String,
+    val mode: GuiMode,
+    val parameters: Map<String, ParameterDefinition>,
+    val actions: Map<ActionKey, ActionDefinition>,
+    val onOpen: ResourceLocation?,
+    val collections: Map<String, CollectionConfig>,
+    val shiftClickRules: List<ShiftClickRule>,
+    val closeItemsPolicy: CloseItemsPolicy,
+    val exclusive: Boolean
+) {
+    init {
+        require(mode == GuiMode.SCREEN || collections.isEmpty()) { "overlay views cannot have container collections" }
+        SlotLayout.validateCollections(collections.mapValues { it.value.layout })
+    }
+}
+
+data class MolangUiOpenRequest(
+    val uiId: ResourceLocation,
+    val parameters: Map<String, ParameterValue> = emptyMap(),
+    val blockPos: BlockPos? = null
+)
+
+sealed interface MolangUiOpenResult {
+    data class Opened(val session: MolangUiSessionHandle) : MolangUiOpenResult
+    data class Rejected(val reason: RejectionReason, val detail: String) : MolangUiOpenResult
+}
+
+enum class RejectionReason {
+    UNKNOWN_UI,
+    INCOMPATIBLE_CLIENT,
+    INVALID_PARAMETERS,
+    SESSION_LIMIT,
+    INVALID_CONTAINER,
+    INTERNAL_ERROR
+}
+
+enum class SessionState { OPENING, ACTIVE, CLOSING, CLOSED }
+
+interface MolangUiSessionHandle : AutoCloseable {
+    val sessionId: UUID
+    val uiId: ResourceLocation
+    val state: SessionState
+    fun updateParameters(parameters: Map<String, ParameterValue>): Boolean
+    fun updateVariables(variables: Map<String, Double>): Boolean
+    override fun close()
+}
+
+data class MolangUiActionContext(
+    val session: MolangUiSessionHandle,
+    val player: ServerPlayer,
+    val parameters: Map<String, ParameterValue>
+)
+
+fun interface MolangUiActionHandler {
+    fun handle(context: MolangUiActionContext)
+}

common/src/main/kotlin/com/cobblemon/mod/common/api/molangui/MolangUiPacketLimits.kt

@@ -0,0 +1,29 @@
+/*
+ * Copyright (C) 2023 Cobblemon Contributors
+ *
+ * This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at https://mozilla.org/MPL/2.0/.
+ */
+
+package com.cobblemon.mod.common.api.molangui
+
+object MolangUiPacketLimits {
+    const val MAX_CONTRACTS = 256
+    const val MAX_ACTION_FIELDS = 32
+    const val MAX_IDENTIFIER_LENGTH = 128
+    const val MAX_VALUE_LENGTH = 4 * 1024
+    const val MAX_PACKET_BYTES = 256 * 1024
+
+    fun requireIdentifier(value: String, label: String): String {
+        require(value.isNotBlank() && value.length <= MAX_IDENTIFIER_LENGTH) {
+            "$label must contain 1..$MAX_IDENTIFIER_LENGTH characters"
+        }
+        return value
+    }
+
+    fun requireValue(value: String, label: String): String {
+        require(value.length <= MAX_VALUE_LENGTH) { "$label exceeds $MAX_VALUE_LENGTH characters" }
+        return value
+    }
+}

common/src/main/kotlin/com/cobblemon/mod/common/api/molangui/MolangUiParameters.kt

@@ -0,0 +1,68 @@
+/*
+ * Copyright (C) 2023 Cobblemon Contributors
+ *
+ * This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at https://mozilla.org/MPL/2.0/.
+ */
+
+package com.cobblemon.mod.common.api.molangui
+
+import com.bedrockk.molang.runtime.value.DoubleValue
+import com.bedrockk.molang.runtime.value.MoValue
+import com.bedrockk.molang.runtime.value.StringValue
+
+internal object MolangUiParameters {
+    val GENERAL_FUNCTIONS = setOf("format", "to_string", "to_number", "to_int", "is_number", "is_int", "is_blank")
+    private val reserved = GENERAL_FUNCTIONS + setOf(
+        "gui_id", "gui_time", "delta", "screen_width", "screen_height", "mouse_x", "mouse_y", "item", "translate", "event"
+    )
+    private val namePattern = Regex("[a-z_][a-z0-9_]*")
+
+    fun requireName(name: String) {
+        MolangUiPacketLimits.requireIdentifier(name, "parameter name")
+        require(namePattern.matches(name) && name !in reserved) { "invalid or reserved parameter name '$name'" }
+    }
+
+    fun decode(types: Map<String, ParameterType>, values: Map<String, String>): Map<String, ParameterValue> {
+        require(values.size <= MolangUiPacketLimits.MAX_ACTION_FIELDS) { "too many parameters" }
+        return values.mapValues { (name, raw) ->
+            requireName(name)
+            val type = types[name] ?: throw IllegalArgumentException("undeclared parameter '$name'")
+            MolangUiPacketLimits.requireValue(raw, name)
+            ParameterValue.parse(type, raw) ?: throw IllegalArgumentException("invalid ${type.id} parameter '$name'")
+        }
+    }
+
+    fun validate(values: Map<String, ParameterValue>) {
+        require(values.size <= MolangUiPacketLimits.MAX_ACTION_FIELDS) { "too many parameters" }
+        values.forEach { (name, value) ->
+            requireName(name)
+            MolangUiPacketLimits.requireValue(value.asWireValue(), name)
+        }
+    }
+
+    fun requireVariableName(name: String): String {
+        MolangUiPacketLimits.requireIdentifier(name, "variable name")
+        return name.removePrefix("v.").also {
+            require(namePattern.matches(it)) { "invalid variable '$name'" }
+        }
+    }
+
+    fun validateVariables(values: Map<String, Double>) {
+        val names = mutableSetOf<String>()
+        values.forEach { (name, value) ->
+            val canonical = requireVariableName(name)
+            require(names.add(canonical) && value.isFinite()) {
+                "invalid or duplicate variable '$name'"
+            }
+        }
+    }
+}
+
+internal fun ParameterValue.asMoLangValue(): MoValue = when (this) {
+    is ParameterValue.StringValue -> StringValue(value)
+    is ParameterValue.NumberValue -> DoubleValue(value)
+    is ParameterValue.BooleanValue -> DoubleValue(value)
+    is ParameterValue.Vec3Value -> StringValue(asWireValue())
+}

common/src/main/kotlin/com/cobblemon/mod/common/api/molangui/MolangUiRegistry.kt

@@ -0,0 +1,95 @@
+/*
+ * Copyright (C) 2023 Cobblemon Contributors
+ *
+ * This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at https://mozilla.org/MPL/2.0/.
+ */
+
+package com.cobblemon.mod.common.api.molangui
+
+import com.cobblemon.mod.common.Cobblemon
+import com.cobblemon.mod.common.api.molangui.template.TemplateLibraryRegistry
+import com.cobblemon.mod.common.api.molangui.widget.WidgetDefinition
+import com.cobblemon.mod.common.api.molangui.widget.WidgetTree
+import com.google.gson.JsonObject
+import com.google.gson.JsonParser
+import net.minecraft.resources.ResourceLocation
+import net.minecraft.server.packs.resources.ResourceManager
+import java.util.concurrent.atomic.AtomicLong
+
+/** Client asset registry. Server code must use [MolangUiContractRegistry]. */
+object MolangUiRegistry {
+    private const val DIRECTORY = "molang_ui"
+    private val definitions = linkedMapOf<ResourceLocation, MolangUiDefinition>()
+    private val parseFailures = AtomicLong()
+
+    fun reload(manager: ResourceManager) {
+        TemplateLibraryRegistry.reload(manager)
+        val next = linkedMapOf<ResourceLocation, MolangUiDefinition>()
+        manager.listResources(DIRECTORY) { it.path.endsWith(".json") && !it.path.contains("/templates/") }
+            .forEach { (identifier, resource) ->
+                val guiId = ResourceLocation.fromNamespaceAndPath(
+                    identifier.namespace,
+                    identifier.path.removePrefix("$DIRECTORY/").removeSuffix(".json")
+                )
+                try {
+                    val json = resource.openAsReader().use { JsonParser.parseReader(it).asJsonObject }
+                    next[guiId] = parse(guiId, json)
+                } catch (error: Exception) {
+                    parseFailures.incrementAndGet()
+                    Cobblemon.LOGGER.error("Rejected Molang UI view '$identifier': ${error.message}")
+                }
+            }
+        require(next.size <= MolangUiPacketLimits.MAX_CONTRACTS) { "too many Molang UI views" }
+        definitions.clear()
+        definitions.putAll(next)
+        Cobblemon.LOGGER.info("Loaded ${definitions.size} validated Molang UI views")
+    }
+
+    internal fun parse(guiId: ResourceLocation, json: JsonObject): MolangUiDefinition {
+        require(!json.has("blocks_input")) { "blocks_input is unsupported; input handling is determined by mode" }
+        val formatVersion = json.get("format_version").requireUiInt("format_version")
+        require(formatVersion == MOLANG_UI_FORMAT_VERSION) { "unsupported format_version $formatVersion" }
+        val contractVersion = json.get("contract_version").requireUiString("contract_version")
+        MolangUiPacketLimits.requireIdentifier(contractVersion, "contract_version")
+        val mode = GuiMode.fromString(json.get("mode").requireUiString("mode"))
+            ?: throw IllegalArgumentException("unknown mode '${json.get("mode").asString}'")
+        val parameterJson = json.getAsJsonObject("parameters")
+        require((parameterJson?.size() ?: 0) <= MolangUiPacketLimits.MAX_ACTION_FIELDS) { "too many parameters" }
+        val parameters = parameterJson?.entrySet()?.associate { (name, value) ->
+            MolangUiParameters.requireName(name)
+            val type = ParameterType.fromId(value.requireUiString("parameters.$name"))
+                ?: throw IllegalArgumentException("unknown parameter type for '$name'")
+            name to type
+        }?.toMap() ?: emptyMap()
+        val actions = json.getAsJsonArray("actions")?.map { ActionKey(it.requireUiString("actions")) }?.toSet() ?: emptySet()
+        require(actions.size <= MolangUiPacketLimits.MAX_ACTION_FIELDS) { "too many declared actions" }
+        val variables = json.getAsJsonObject("variables")?.entrySet()?.associate { (name, value) ->
+            MolangUiPacketLimits.requireIdentifier(name, "variable name")
+            name to value.requireUiNumber("variables.$name")
+        }?.toMap() ?: emptyMap()
+        MolangUiParameters.validateVariables(variables)
+        require(!json.has("imports")) { "template imports are unsupported; use qualified template references" }
+        val root = WidgetTree.parse(json)
+        val referencedActions = linkedSetOf<ActionKey>().also { collectActions(root, it) }
+        val undeclared = referencedActions - actions
+        require(undeclared.isEmpty()) { "widgets reference undeclared actions: ${undeclared.joinToString { it.value }}" }
+        return MolangUiDefinition(
+            guiId, formatVersion, contractVersion, mode, parameters, actions,
+            json.get("exclusive")?.requireUiBoolean("exclusive") ?: false,
+            root, variables
+        )
+    }
+
+    private fun collectActions(node: WidgetDefinition, output: MutableSet<ActionKey>) {
+        node.events.values.forEach { output += it.action }
+        node.children.forEach { collectActions(it, output) }
+        node.itemTemplate?.let { collectActions(it, output) }
+    }
+
+    fun getDefinition(guiId: ResourceLocation): MolangUiDefinition? = definitions[guiId]
+    fun getAllDefinitions(): Map<ResourceLocation, MolangUiDefinition> = definitions.toMap()
+    fun getVersionMap(): Map<ResourceLocation, String> = definitions.mapValues { it.value.contractVersion }
+    fun parseFailureCount(): Long = parseFailures.get()
+}

common/src/main/kotlin/com/cobblemon/mod/common/api/molangui/MolangUiServerRuntimeFactory.kt

@@ -0,0 +1,93 @@
+/*
+ * Copyright (C) 2023 Cobblemon Contributors
+ *
+ * This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at https://mozilla.org/MPL/2.0/.
+ */
+
+package com.cobblemon.mod.common.api.molangui
+
+import com.bedrockk.molang.runtime.MoLangRuntime
+import com.bedrockk.molang.runtime.value.DoubleValue
+import com.bedrockk.molang.runtime.value.MoValue
+import com.bedrockk.molang.runtime.value.StringValue
+import com.cobblemon.mod.common.api.molang.function.GeneralMoLangFunctions
+import net.minecraft.core.registries.BuiltInRegistries
+import net.minecraft.resources.ResourceLocation
+import net.minecraft.world.item.Item
+import net.minecraft.world.item.ItemStack
+
+/** Builds a server runtime with only UI-scoped capabilities. It never exposes q.player. */
+internal object MolangUiServerRuntimeFactory {
+    fun create(session: MolangUiSession): MoLangRuntime = MoLangRuntime().also { runtime ->
+        GeneralMoLangFunctions.functions.filterKeys { it in MolangUiParameters.GENERAL_FUNCTIONS }.forEach { (name, function) ->
+            runtime.environment.query.addFunction(name) { function(it) }
+        }
+        runtime.environment.query.addFunction("parameter") { params ->
+            session.getParameter(params.getString(0))?.asMoLangValue() ?: DoubleValue.ZERO
+        }
+        runtime.environment.query.addFunction("update_parameter") { params ->
+            val name = params.getString(0)
+            val raw = params.get<MoValue>(1).asString()
+            val type = session.contract.parameters[name]?.type
+            DoubleValue(type != null && ParameterValue.parse(type, raw)?.let { session.updateParameters(mapOf(name to it)) } == true)
+        }
+        runtime.environment.query.addFunction("update_variable") { params ->
+            val value = params.getDouble(1)
+            DoubleValue(value.isFinite() && session.updateVariables(mapOf(params.getString(0) to value)))
+        }
+        runtime.environment.query.addFunction("close_ui") {
+            session.close()
+            DoubleValue.ONE
+        }
+        runtime.environment.query.addFunction("count_item") { params ->
+            val item = validatedItem(params.getString(0)) ?: return@addFunction DoubleValue.ZERO
+            DoubleValue(session.player.inventory.items.filter { it.`is`(item) }.sumOf(ItemStack::getCount).toDouble())
+        }
+        runtime.environment.query.addFunction("remove_items") { params ->
+            val item = validatedItem(params.getString(0)) ?: return@addFunction DoubleValue.ZERO
+            val count = params.getDouble(1).asNonnegativeInt() ?: return@addFunction DoubleValue.ZERO
+            DoubleValue(count > 0 && removeAtomically(session, item, count))
+        }
+        runtime.environment.query.addFunction("slot") { params ->
+            val index = params.getDouble(1).asNonnegativeInt() ?: return@addFunction StringValue("")
+            val stack = session.containerMenu?.getStack(params.getString(0), index)
+            if (stack == null || stack.isEmpty) StringValue("") else StringValue(BuiltInRegistries.ITEM.getKey(stack.item).toString())
+        }
+        runtime.environment.query.addFunction("replace_slot") { params ->
+            val itemId = params.getString(5)
+            validatedItem(itemId) ?: return@addFunction DoubleValue.ZERO
+            val inputIndex = params.getDouble(1).asNonnegativeInt() ?: return@addFunction DoubleValue.ZERO
+            val consumeCount = params.getDouble(2).asNonnegativeInt() ?: return@addFunction DoubleValue.ZERO
+            val outputIndex = params.getDouble(4).asNonnegativeInt() ?: return@addFunction DoubleValue.ZERO
+            val outputCount = params.getDouble(6).asNonnegativeInt() ?: return@addFunction DoubleValue.ZERO
+            val result = session.containerMenu?.replaceSlotAtomically(
+                params.getString(0), inputIndex, consumeCount,
+                params.getString(3), outputIndex, itemId, outputCount
+            ) ?: false
+            DoubleValue(result)
+        }
+    }
+
+    private fun validatedItem(raw: String) = ResourceLocation.tryParse(raw)
+        ?.takeIf(BuiltInRegistries.ITEM::containsKey)
+        ?.let(BuiltInRegistries.ITEM::get)
+
+    private fun Double.asNonnegativeInt(): Int? =
+        takeIf { it.isFinite() && it in 0.0..Int.MAX_VALUE.toDouble() && it % 1.0 == 0.0 }?.toInt()
+
+    private fun removeAtomically(session: MolangUiSession, item: Item, count: Int): Boolean {
+        val stacks = session.player.inventory.items.filter { it.`is`(item) }
+        if (stacks.sumOf(ItemStack::getCount) < count) return false
+        var remaining = count
+        stacks.forEach { stack ->
+            if (remaining == 0) return@forEach
+            val removed = minOf(stack.count, remaining)
+            stack.shrink(removed)
+            remaining -= removed
+        }
+        session.player.inventory.setChanged()
+        return true
+    }
+}

common/src/main/kotlin/com/cobblemon/mod/common/api/molangui/MolangUiSession.kt

@@ -0,0 +1,317 @@
+/*
+ * Copyright (C) 2023 Cobblemon Contributors
+ *
+ * This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at https://mozilla.org/MPL/2.0/.
+ */
+
+package com.cobblemon.mod.common.api.molangui
+
+import com.bedrockk.molang.runtime.MoLangRuntime
+import net.minecraft.core.BlockPos
+import com.cobblemon.mod.common.Cobblemon
+import com.cobblemon.mod.common.api.molangui.container.CollectionSource
+import com.cobblemon.mod.common.api.molangui.container.MolangContainerMenu
+import com.cobblemon.mod.common.api.molangui.container.ServerCollectionSetup
+import com.cobblemon.mod.common.net.messages.client.molangui.MolangUiClosePacket
+import com.cobblemon.mod.common.net.messages.client.molangui.MolangUiOpenPacket
+import com.cobblemon.mod.common.net.messages.client.molangui.MolangUiUpdatePacket
+import com.cobblemon.mod.common.util.asExpressionLike
+import net.minecraft.network.chat.Component
+import net.minecraft.resources.ResourceLocation
+import net.minecraft.server.level.ServerPlayer
+import net.minecraft.world.Container
+import net.minecraft.world.MenuProvider
+import net.minecraft.world.SimpleContainer
+import net.minecraft.world.entity.player.Inventory
+import net.minecraft.world.entity.player.Player
+import net.minecraft.world.inventory.AbstractContainerMenu
+import java.util.UUID
+
+internal class MolangUiSession(
+    override val sessionId: UUID,
+    override val uiId: ResourceLocation,
+    val player: ServerPlayer,
+    val contract: MolangUiContract,
+    initialParameters: Map<String, ParameterValue>,
+    val blockPos: BlockPos?
+) : MolangUiSessionHandle {
+    override var state: SessionState = SessionState.OPENING
+        private set
+    private val parameters = initialParameters.toMutableMap()
+    internal var containerMenu: MolangContainerMenu? = null
+    private var clientWasNotified = false
+
+    override fun updateParameters(parameters: Map<String, ParameterValue>): Boolean {
+        assertServerThread()
+        if (state != SessionState.ACTIVE || !validateParameterUpdate(parameters)) return false
+        MolangUiUpdatePacket(sessionId, parameters.mapValues { it.value.asWireValue() }).sendToPlayer(player)
+        this.parameters.putAll(parameters)
+        return true
+    }
+
+    override fun updateVariables(variables: Map<String, Double>): Boolean {
+        assertServerThread()
+        if (state != SessionState.ACTIVE || variables.size > MolangUiPacketLimits.MAX_ACTION_FIELDS) return false
+        try {
+            MolangUiParameters.validateVariables(variables)
+        } catch (error: IllegalArgumentException) {
+            return false
+        }
+        MolangUiUpdatePacket(sessionId, emptyMap(), variables).sendToPlayer(player)
+        return true
+    }
+
+    override fun close() = closeInternal(notifyClient = true, closeMenu = true)
+
+    internal fun closeFromClient() = closeInternal(notifyClient = false, closeMenu = true)
+    internal fun closeFromMenu() = closeInternal(notifyClient = true, closeMenu = false)
+
+    internal fun activate() {
+        assertServerThread()
+        check(state == SessionState.OPENING)
+        state = SessionState.ACTIVE
+    }
+
+    internal fun notifyOpened(hasContainer: Boolean) {
+        check(state == SessionState.OPENING)
+        clientWasNotified = true
+        MolangUiOpenPacket(
+            sessionId, uiId, contract.contractVersion, contract.mode,
+            parameters.mapValues { it.value.asWireValue() }, contract.exclusive,
+            hasContainer, contract.collections.mapValues { it.value.layout }
+        ).sendToPlayer(player)
+    }
+
+    internal fun getParameter(name: String): ParameterValue? = parameters[name]
+
+    private fun validateParameterUpdate(values: Map<String, ParameterValue>): Boolean =
+        values.size <= MolangUiPacketLimits.MAX_ACTION_FIELDS && values.all { (name, value) ->
+            contract.parameters[name]?.type == value.type && value.asWireValue().length <= MolangUiPacketLimits.MAX_VALUE_LENGTH
+        }
+
+    private fun closeInternal(notifyClient: Boolean, closeMenu: Boolean) {
+        assertServerThread()
+        if (state == SessionState.CLOSING || state == SessionState.CLOSED) return
+        state = SessionState.CLOSING
+        val menu = containerMenu
+        containerMenu = null
+        try {
+            cleanup("notify client") {
+                if (notifyClient && clientWasNotified) MolangUiClosePacket(sessionId).sendToPlayer(player)
+            }
+            cleanup("close container") {
+                if (closeMenu && menu != null && player.containerMenu === menu) player.closeContainer()
+            }
+            cleanup("release items") { menu?.releaseOwnedItemsOnce(player) }
+        } finally {
+            state = SessionState.CLOSED
+            MolangUiService.remove(sessionId)
+        }
+    }
+
+    private inline fun cleanup(operation: String, action: () -> Unit) {
+        try {
+            action()
+        } catch (error: Exception) {
+            Cobblemon.LOGGER.error("Failed to $operation while closing Molang UI session $sessionId", error)
+        }
+    }
+
+    private fun assertServerThread() {
+        check(player.server.isSameThread) { "Molang UI sessions are confined to the server thread" }
+    }
+}
+
+object MolangUiService {
+    private const val MAX_OVERLAYS_PER_PLAYER = 8
+    private val sessions = linkedMapOf<UUID, MolangUiSession>()
+    private val disabled = mutableMapOf<UUID, Set<ResourceLocation>>()
+    private val rateLimiters = mutableMapOf<UUID, MolangUiRateLimiter>()
+
+    fun open(player: ServerPlayer, request: MolangUiOpenRequest): MolangUiOpenResult {
+        check(player.server.isSameThread) { "MolangUiService.open must run on the server thread" }
+        val contract = MolangUiContractRegistry.getContract(request.uiId)
+            ?: return MolangUiOpenResult.Rejected(RejectionReason.UNKNOWN_UI, "Unknown Molang UI '${request.uiId}'")
+        // Intentionally does not wait for the compatibility round-trip; the client re-validates on open.
+        if (disabled[player.uuid]?.contains(request.uiId) == true) {
+            return MolangUiOpenResult.Rejected(RejectionReason.INCOMPATIBLE_CLIENT, "Client view is missing or incompatible")
+        }
+        val parameters = resolveParameters(contract, request.parameters)
+            ?: return MolangUiOpenResult.Rejected(RejectionReason.INVALID_PARAMETERS, "Parameters do not match the contract")
+        val playerSessions = sessions.values.filter { it.player.uuid == player.uuid && it.state != SessionState.CLOSED }
+        if (contract.mode == GuiMode.OVERLAY && playerSessions.count { it.contract.mode == GuiMode.OVERLAY } >= MAX_OVERLAYS_PER_PLAYER) {
+            return MolangUiOpenResult.Rejected(RejectionReason.SESSION_LIMIT, "At most $MAX_OVERLAYS_PER_PLAYER overlays may be active")
+        }
+        val collectionSetup = try {
+            createCollections(player, contract, request.blockPos)
+                ?: return MolangUiOpenResult.Rejected(RejectionReason.INVALID_CONTAINER, "The bound block container is unavailable or invalid")
+        } catch (error: Exception) {
+            Cobblemon.LOGGER.error("Failed to prepare Molang UI '${request.uiId}'", error)
+            return MolangUiOpenResult.Rejected(RejectionReason.INTERNAL_ERROR, error.message ?: "Unable to prepare UI")
+        }
+        val session = MolangUiSession(UUID.randomUUID(), request.uiId, player, contract, parameters, request.blockPos)
+        sessions[session.sessionId] = session
+        MolangUiDiagnostics.sessionOpened()
+        return try {
+            if (contract.mode == GuiMode.SCREEN) {
+                playerSessions.filter { it.contract.mode == GuiMode.SCREEN }.forEach(MolangUiSession::close)
+            }
+            check(session.state == SessionState.OPENING) { "Molang UI closed while replacing its previous screen" }
+            MolangUiActionRegistry.executeOnOpen(session)
+            check(session.state == SessionState.OPENING) { "Molang UI closed during on_open" }
+            val hasContainer = contract.collections.isNotEmpty()
+            session.notifyOpened(hasContainer)
+            check(session.state == SessionState.OPENING) { "Molang UI closed while notifying the client" }
+            if (hasContainer) openContainer(session, collectionSetup)
+            session.activate()
+            MolangUiOpenResult.Opened(session)
+        } catch (error: Exception) {
+            Cobblemon.LOGGER.error("Failed to open Molang UI '${request.uiId}'", error)
+            session.close()
+            MolangUiOpenResult.Rejected(RejectionReason.INTERNAL_ERROR, error.message ?: "Unable to open UI")
+        }
+    }
+
+    fun handleAction(sessionId: UUID, player: ServerPlayer, actionRaw: String, raw: Map<String, String>) {
+        check(player.server.isSameThread)
+        val session = sessions[sessionId]
+        if (session == null || session.player.uuid != player.uuid || session.state != SessionState.ACTIVE) {
+            MolangUiDiagnostics.actionRejected()
+            return
+        }
+        if (!rateLimiters.getOrPut(sessionId) { MolangUiRateLimiter() }.tryAcquire()) {
+            MolangUiDiagnostics.actionRejected()
+            return
+        }
+        val action = runCatching { ActionKey(actionRaw) }.getOrNull()
+        val definition = action?.let(session.contract.actions::get)
+        if (action == null || definition == null || raw.keys != definition.parameters.keys || raw.size > MolangUiPacketLimits.MAX_ACTION_FIELDS) {
+            MolangUiDiagnostics.actionRejected()
+            return
+        }
+        val typed = linkedMapOf<String, ParameterValue>()
+        for ((name, type) in definition.parameters) {
+            val value = raw[name]
+            if (value == null || value.length > MolangUiPacketLimits.MAX_VALUE_LENGTH) {
+                MolangUiDiagnostics.actionRejected(); return
+            }
+            typed[name] = ParameterValue.parse(type, value) ?: run { MolangUiDiagnostics.actionRejected(); return }
+        }
+        try {
+            MolangUiActionRegistry.dispatch(session, action, typed)
+        } catch (error: Exception) {
+            MolangUiDiagnostics.actionRejected()
+            Cobblemon.LOGGER.error("Molang UI action '${action.value}' failed in session $sessionId", error)
+        }
+    }
+
+    fun handleClosed(sessionId: UUID, player: ServerPlayer) {
+        val session = sessions[sessionId] ?: return
+        if (session.player.uuid == player.uuid) session.closeFromClient() else MolangUiDiagnostics.actionRejected()
+    }
+
+    fun applyCompatibility(player: ServerPlayer, clientVersions: Map<ResourceLocation, String>) {
+        val incompatible = MolangUiContractRegistry.versions().filter { (id, version) -> clientVersions[id] != version }.keys
+        if (incompatible.isEmpty()) disabled.remove(player.uuid) else disabled[player.uuid] = incompatible
+        MolangUiDiagnostics.compatibilityFailures(incompatible.size.toLong())
+        sessions.values.filter { it.player.uuid == player.uuid && it.uiId in incompatible }.toList().forEach(MolangUiSession::close)
+    }
+
+    fun requestCompatibility(player: ServerPlayer) = MolangUiContractRegistry.sync(player)
+
+    fun closeAllForPlayer(playerId: UUID) {
+        sessions.values.filter { it.player.uuid == playerId }.toList().forEach(MolangUiSession::close)
+        disabled.remove(playerId)
+    }
+
+    fun closeAll() {
+        sessions.values.toList().forEach(MolangUiSession::close)
+        disabled.clear()
+    }
+
+    fun getSession(sessionId: UUID): MolangUiSessionHandle? = sessions[sessionId]
+    fun getSessionForPlayer(player: ServerPlayer, id: ResourceLocation): MolangUiSessionHandle? =
+        sessions.values.firstOrNull { it.player.uuid == player.uuid && it.uiId == id && it.state == SessionState.ACTIVE }
+    fun activeSessionCount(): Int = sessions.size
+
+    internal fun remove(sessionId: UUID) {
+        if (sessions.remove(sessionId) != null) MolangUiDiagnostics.sessionClosed()
+        rateLimiters.remove(sessionId)
+    }
+
+    private fun resolveParameters(contract: MolangUiContract, supplied: Map<String, ParameterValue>): Map<String, ParameterValue>? {
+        if (supplied.keys.any { it !in contract.parameters }) return null
+        val values = linkedMapOf<String, ParameterValue>()
+        for ((name, definition) in contract.parameters) {
+            val suppliedValue = supplied[name]
+            val value = suppliedValue ?: when (val default = definition.default) {
+                is ParameterDefault.Literal -> default.value
+                is ParameterDefault.Molang -> runCatching {
+                    val result = default.expression.asExpressionLike().resolveString(MoLangRuntime())
+                    ParameterValue.parse(definition.type, result)
+                }.getOrNull()
+                null -> null
+            }
+            if (value == null) {
+                if (definition.required) return null else continue
+            }
+            if (value.type != definition.type || value.asWireValue().length > MolangUiPacketLimits.MAX_VALUE_LENGTH) return null
+            values[name] = value
+        }
+        return values
+    }
+
+    private fun createCollections(
+        player: ServerPlayer,
+        contract: MolangUiContract,
+        blockPos: BlockPos?
+    ): List<ServerCollectionSetup>? {
+        val setups = mutableListOf<ServerCollectionSetup>()
+        for ((name, config) in contract.collections) {
+            val container: Container = when (config.source) {
+                CollectionSource.SESSION -> SimpleContainer(config.size)
+                CollectionSource.BLOCK_ENTITY -> {
+                    val pos = blockPos ?: return null
+                    if (player.distanceToSqr(pos.x + .5, pos.y + .5, pos.z + .5) > 64.0 || !player.level().hasChunk(pos.x shr 4, pos.z shr 4)) return null
+                    val blockEntity = player.level().getBlockEntity(pos)
+                    if (blockEntity !is Container) return null
+                    if ((config.slots ?: (0 until config.size).toList()).any { it >= blockEntity.containerSize }) return null
+                    blockEntity
+                }
+            }
+            setups += ServerCollectionSetup(name, config, container)
+        }
+        return setups
+    }
+
+    private fun openContainer(session: MolangUiSession, setup: List<ServerCollectionSetup>) {
+        val owned = setup.filter { it.config.source == CollectionSource.SESSION }.mapTo(mutableSetOf()) { it.name }
+        val opened = session.player.openMenu(object : MenuProvider {
+            override fun getDisplayName() = Component.empty()
+            override fun createMenu(containerId: Int, inventory: Inventory, player: Player): AbstractContainerMenu =
+                MolangContainerMenu(containerId, inventory).also { menu ->
+                    check(session.state == SessionState.OPENING) { "Molang UI closed before creating its container" }
+                    session.containerMenu = menu
+                    menu.initializeServer(
+                        setup, session.contract.shiftClickRules, owned, session.contract.closeItemsPolicy,
+                        owner = session.player, session = session, blockPos = session.blockPos
+                    )
+                }
+        })
+        check(opened.isPresent) { "player rejected the Molang UI container menu" }
+    }
+}
+
+internal class MolangUiRateLimiter(private var lastNanos: Long = System.nanoTime()) {
+    private var tokens = 40.0
+    fun tryAcquire(now: Long = System.nanoTime()): Boolean {
+        val elapsed = (now - lastNanos).coerceAtLeast(0) / 1_000_000_000.0
+        tokens = minOf(40.0, tokens + elapsed * 20.0)
+        lastNanos = now
+        if (tokens < 1.0) return false
+        tokens -= 1.0
+        return true
+    }
+}

common/src/main/kotlin/com/cobblemon/mod/common/api/molangui/container/CollectionConfig.kt

@@ -0,0 +1,94 @@
+/*
+ * Copyright (C) 2023 Cobblemon Contributors
+ *
+ * This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at https://mozilla.org/MPL/2.0/.
+ */
+
+package com.cobblemon.mod.common.api.molangui.container
+
+import net.minecraft.core.registries.BuiltInRegistries
+import net.minecraft.core.registries.Registries
+import net.minecraft.resources.ResourceLocation
+import net.minecraft.tags.TagKey
+import net.minecraft.world.item.ItemStack
+
+data class CollectionConfig(
+    val size: Int,
+    val allowedItems: List<ItemFilterEntry> = emptyList(),
+    val takeOnly: Boolean = false,
+    val source: CollectionSource = CollectionSource.SESSION,
+    val slots: List<Int>? = null,
+    val layout: SlotLayout
+) {
+    init {
+        require(size in 1..MAX_COLLECTION_SIZE) { "collection size must be in 1..$MAX_COLLECTION_SIZE" }
+        require(layout.slotCount == size) { "collection size must match its grid dimensions" }
+        require(slots == null || slots.size == size) { "block collection slot mapping must match collection size" }
+        require(slots == null || slots.distinct().size == slots.size) { "block collection slot mapping contains duplicates" }
+        require(slots == null || slots.all { it >= 0 }) { "block collection slot indices must be nonnegative" }
+        require(source == CollectionSource.BLOCK_ENTITY || slots == null) { "slot mapping is only valid for block_entity sources" }
+    }
+
+    fun isItemAllowed(stack: ItemStack): Boolean {
+        return !takeOnly && matchesFilter(stack)
+    }
+
+    fun matchesFilter(stack: ItemStack): Boolean {
+        if (allowedItems.isEmpty()) return true
+        return allowedItems.any { it.matches(stack) }
+    }
+
+    companion object { const val MAX_COLLECTION_SIZE = 256 }
+}
+
+enum class CollectionSource(val id: String) {
+    SESSION("session"), BLOCK_ENTITY("block_entity");
+    companion object { fun fromId(id: String) = entries.firstOrNull { it.id == id } }
+}
+
+data class ShiftClickRule(
+    val from: List<String>,
+    val to: List<String>
+) {
+    companion object {
+        const val PLAYER_INVENTORY = "player_inventory"
+        const val PLAYER_HOTBAR = "player_hotbar"
+        val PLAYER_SIDE_NAMES = listOf(PLAYER_INVENTORY, PLAYER_HOTBAR)
+    }
+}
+
+sealed interface ItemFilterEntry {
+    fun matches(stack: ItemStack): Boolean
+
+    data class Item(val id: ResourceLocation) : ItemFilterEntry {
+        override fun matches(stack: ItemStack): Boolean {
+            if (!BuiltInRegistries.ITEM.containsKey(id)) return false
+            return stack.`is`(BuiltInRegistries.ITEM.get(id))
+        }
+    }
+
+    data class Tag(val id: ResourceLocation) : ItemFilterEntry {
+        override fun matches(stack: ItemStack): Boolean = stack.`is`(TagKey.create(Registries.ITEM, id))
+    }
+
+    companion object {
+        fun parse(value: String): ItemFilterEntry? {
+            val trimmed = value.trim()
+            val isTag = trimmed.startsWith('#')
+            val id = ResourceLocation.tryParse(if (isTag) trimmed.substring(1) else trimmed) ?: return null
+            return if (isTag) Tag(id) else Item(id)
+        }
+    }
+}
+
+enum class CloseItemsPolicy(val id: String) {
+    DROP("drop"),
+    RETURN("return"),
+    DESTROY("destroy");
+
+    companion object {
+        fun fromId(id: String): CloseItemsPolicy? = entries.firstOrNull { it.id == id }
+    }
+}

common/src/main/kotlin/com/cobblemon/mod/common/api/molangui/container/CollectionSetup.kt

@@ -6,10 +6,12 @@
  * file, You can obtain one at https://mozilla.org/MPL/2.0/.
  */
 
-package com.cobblemon.mod.common.entity.projectile
+package com.cobblemon.mod.common.api.molangui.container
 
-enum class FallingStarResultType {
-    MINIOR,
-    ITEM,
-    POKEMON
-}
+import net.minecraft.world.Container
+
+data class ServerCollectionSetup(
+    val name: String,
+    val config: CollectionConfig,
+    val container: Container
+)

common/src/main/kotlin/com/cobblemon/mod/common/api/molangui/container/MolangContainerMenu.kt

@@ -0,0 +1,300 @@
+/*
+ * Copyright (C) 2023 Cobblemon Contributors
+ *
+ * This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at https://mozilla.org/MPL/2.0/.
+ */
+
+package com.cobblemon.mod.common.api.molangui.container
+
+import com.cobblemon.mod.common.CobblemonMenuType
+import com.cobblemon.mod.common.api.molangui.MolangUiSession
+import com.cobblemon.mod.common.api.molangui.SessionState
+import net.minecraft.core.BlockPos
+import net.minecraft.core.registries.BuiltInRegistries
+import net.minecraft.resources.ResourceLocation
+import net.minecraft.server.level.ServerPlayer
+import net.minecraft.world.Container
+import net.minecraft.world.SimpleContainer
+import net.minecraft.world.entity.player.Inventory
+import net.minecraft.world.entity.player.Player
+import net.minecraft.world.inventory.AbstractContainerMenu
+import net.minecraft.world.inventory.Slot
+import net.minecraft.world.item.ItemStack
+
+private data class CollectionSlotRange(
+    val name: String,
+    val startIndex: Int,
+    val endIndex: Int
+)
+
+class MolangContainerMenu(
+    containerId: Int,
+    private val playerInventory: Inventory
+) : AbstractContainerMenu(CobblemonMenuType.MOLANG_UI, containerId) {
+
+    private val collections: MutableMap<String, Container> = mutableMapOf()
+
+    private val collectionRanges: MutableList<CollectionSlotRange> = mutableListOf()
+    private var playerInventoryStart: Int = 0
+    private var playerHotbarStart: Int = 0
+    private var playerHotbarEnd: Int = 0
+
+    private var shiftClickRules: List<ShiftClickRule> = emptyList()
+
+    private val collectionConfigs: MutableMap<String, CollectionConfig> = mutableMapOf()
+    private val sessionOwnedCollections: MutableSet<String> = mutableSetOf()
+    private var closeItemsPolicy: CloseItemsPolicy = CloseItemsPolicy.RETURN
+    private var owner: ServerPlayer? = null
+    private var owningSession: MolangUiSession? = null
+    private var blockPos: BlockPos? = null
+    private var originalBlockContainer: Container? = null
+    private var ownedItemsReleased = false
+
+    internal fun initializeServer(
+        collectionSetup: List<ServerCollectionSetup>,
+        shiftClickRules: List<ShiftClickRule> = emptyList(),
+        sessionOwned: Set<String> = emptySet(),
+        closeItemsPolicy: CloseItemsPolicy = CloseItemsPolicy.RETURN,
+        owner: ServerPlayer,
+        session: MolangUiSession,
+        blockPos: BlockPos? = null
+    ) {
+        this.shiftClickRules = shiftClickRules
+        this.sessionOwnedCollections.addAll(sessionOwned)
+        this.closeItemsPolicy = closeItemsPolicy
+        this.owner = owner
+        this.owningSession = session
+        this.blockPos = blockPos
+
+        for (setup in collectionSetup) {
+            val (name, config, container) = setup
+            collections[name] = container
+            if (config.source == CollectionSource.BLOCK_ENTITY) originalBlockContainer = container
+            collectionConfigs[name] = config
+
+            val startIndex = slots.size
+            addCollectionSlots(name, config, container)
+            val endIndex = slots.size
+            collectionRanges.add(CollectionSlotRange(name, startIndex, endIndex))
+        }
+
+        addPlayerSlots()
+    }
+
+    fun initializeClient(
+        collectionLayouts: Map<String, SlotLayout>
+    ) {
+        SlotLayout.validateCollections(collectionLayouts)
+        for ((name, layout) in collectionLayouts) {
+            val config = CollectionConfig(size = layout.slotCount, layout = layout)
+            val container = SimpleContainer(layout.slotCount)
+            collections[name] = container
+            collectionConfigs[name] = config
+
+            val startIndex = slots.size
+            addCollectionSlots(name, config, container)
+            val endIndex = slots.size
+            collectionRanges.add(CollectionSlotRange(name, startIndex, endIndex))
+        }
+
+        addPlayerSlots()
+    }
+
+    private fun addCollectionSlots(
+        name: String,
+        config: CollectionConfig,
+        container: Container
+    ) {
+        val layout = config.layout
+        var containerIndex = 0
+        for (row in 0 until layout.rows) {
+            for (col in 0 until layout.columns) {
+                val x = layout.offsetX + col * (layout.slotWidth + layout.spacingX)
+                val y = layout.offsetY + row * (layout.slotHeight + layout.spacingY)
+                val mappedIndex = config.slots?.getOrNull(containerIndex) ?: containerIndex
+                require(mappedIndex in 0 until container.containerSize) { "collection '$name' maps outside its container" }
+                addSlot(MolangSlot(
+                    container = container,
+                    index = mappedIndex,
+                    x = x,
+                    y = y,
+                    collectionConfig = config
+                ))
+                containerIndex++
+            }
+        }
+    }
+
+    private fun addPlayerSlots() {
+        playerInventoryStart = slots.size
+
+        for (row in 0 until 3) {
+            for (col in 0 until 9) {
+                val inventoryIndex = 9 + row * 9 + col
+                val x = 8 + col * 18
+                val y = 84 + row * 18
+                addSlot(Slot(playerInventory, inventoryIndex, x, y))
+            }
+        }
+
+        playerHotbarStart = slots.size
+
+        for (col in 0 until 9) {
+            addSlot(Slot(playerInventory, col, 8 + col * 18, 142))
+        }
+
+        playerHotbarEnd = slots.size
+    }
+
+    override fun quickMoveStack(player: Player, index: Int): ItemStack {
+        val slot = slots.getOrNull(index) ?: return ItemStack.EMPTY
+        if (!slot.hasItem() || !slot.mayPickup(player)) return ItemStack.EMPTY
+
+        val slotItem = slot.item
+        val original = slotItem.copy()
+
+        val clickedCollection = collectionRanges.firstOrNull { index >= it.startIndex && index < it.endIndex }
+        val isPlayerInventory = index >= playerInventoryStart && index < playerInventoryEnd()
+        val isHotbar = index >= playerHotbarStart && index < playerHotbarEnd
+
+        val sourceName = clickedCollection?.name ?: when {
+            isPlayerInventory -> ShiftClickRule.PLAYER_INVENTORY
+            isHotbar -> ShiftClickRule.PLAYER_HOTBAR
+            else -> return ItemStack.EMPTY
+        }
+        val destinations = findShiftClickRule(sourceName)?.to ?: if (clickedCollection != null) {
+            ShiftClickRule.PLAYER_SIDE_NAMES
+        } else {
+            collectionRanges.map { it.name }
+        }
+        if (!tryMoveToCollections(slotItem, slot, destinations)) return ItemStack.EMPTY
+
+        if (slotItem.isEmpty) {
+            slot.setByPlayer(ItemStack.EMPTY)
+        } else {
+            slot.setChanged()
+        }
+
+        if (slotItem.count == original.count) return ItemStack.EMPTY
+
+        slot.onTake(player, slotItem)
+        return original
+    }
+
+    override fun stillValid(player: Player): Boolean {
+        val expectedOwner = owner ?: return true // client menu
+        if (player.uuid != expectedOwner.uuid || owningSession?.state != SessionState.ACTIVE) return false
+        val pos = blockPos ?: return true
+        if (player.distanceToSqr(pos.x + .5, pos.y + .5, pos.z + .5) > 64.0) return false
+        return player.level().getBlockEntity(pos) === originalBlockContainer
+    }
+
+    override fun removed(player: Player) {
+        try {
+            super.removed(player)
+        } finally {
+            try {
+                releaseOwnedItemsOnce(player)
+            } finally {
+                owningSession?.closeFromMenu()
+            }
+        }
+    }
+
+    fun releaseOwnedItemsOnce(player: Player) {
+        if (ownedItemsReleased) return
+        ownedItemsReleased = true
+        for (name in sessionOwnedCollections) {
+            val container = collections[name] ?: continue
+            when (closeItemsPolicy) {
+                CloseItemsPolicy.DROP -> clearContainer(player, container)
+                CloseItemsPolicy.RETURN -> returnItemsToPlayer(player, container)
+                CloseItemsPolicy.DESTROY -> container.clearContent()
+            }
+        }
+    }
+
+    fun getStack(collection: String, index: Int): ItemStack? {
+        return collectionSlot(collection, index)?.item
+    }
+
+    fun replaceSlotAtomically(
+        inputCollection: String,
+        inputIndex: Int,
+        consumeCount: Int,
+        outputCollection: String,
+        outputIndex: Int,
+        outputItemId: String,
+        outputCount: Int
+    ): Boolean {
+        if (consumeCount <= 0 || outputCount <= 0) return false
+        val input = collectionSlot(inputCollection, inputIndex) ?: return false
+        val output = collectionSlot(outputCollection, outputIndex) ?: return false
+        val id = ResourceLocation.tryParse(outputItemId)?.takeIf(BuiltInRegistries.ITEM::containsKey) ?: return false
+        val produced = ItemStack(BuiltInRegistries.ITEM.get(id), outputCount)
+        val outputConfig = collectionConfigs[outputCollection] ?: return false
+        if (!outputConfig.matchesFilter(produced)) return false
+        val source = input.item
+        if (source.count < consumeCount) return false
+        val remaining = source.copyWithCount(source.count - consumeCount)
+        val sameSlot = input.container === output.container && input.containerSlot == output.containerSlot
+        val existing = if (sameSlot) remaining else output.item
+        if (!existing.isEmpty && !ItemStack.isSameItemSameComponents(existing, produced)) return false
+        val limit = output.getMaxStackSize(produced)
+        if (existing.count > limit || outputCount > limit - existing.count) return false
+        val result = if (existing.isEmpty) produced else existing.copyWithCount(existing.count + outputCount)
+        if (!sameSlot) input.set(remaining)
+        output.set(result)
+        return true
+    }
+
+    private fun playerInventoryEnd() = playerHotbarStart
+
+    private fun findShiftClickRule(fromCollection: String): ShiftClickRule? {
+        return shiftClickRules.firstOrNull { rule ->
+            rule.from.contains(fromCollection)
+        }
+    }
+
+    private fun collectionSlot(name: String, index: Int): Slot? {
+        val range = collectionRanges.firstOrNull { it.name == name } ?: return null
+        if (index !in 0 until range.endIndex - range.startIndex) return null
+        return slots[range.startIndex + index]
+    }
+
+    private fun tryMoveToCollections(stack: ItemStack, source: Slot, toNames: List<String>): Boolean {
+        val originalCount = stack.count
+        for (name in toNames) {
+            val indices = when (name) {
+                ShiftClickRule.PLAYER_INVENTORY -> playerInventoryStart until playerHotbarStart
+                ShiftClickRule.PLAYER_HOTBAR -> playerHotbarStart until playerHotbarEnd
+                else -> collectionRanges.firstOrNull { it.name == name }?.let { it.startIndex until it.endIndex } ?: continue
+            }
+            for (merge in listOf(true, false)) {
+                for (index in indices) {
+                    if (stack.isEmpty) return true
+                    val destination = slots[index]
+                    if (destination.container === source.container && destination.containerSlot == source.containerSlot) continue
+                    if (destination.hasItem() != merge || destination.item.count >= destination.getMaxStackSize(stack)) continue
+                    destination.safeInsert(stack)
+                }
+            }
+        }
+        return stack.count < originalCount
+    }
+
+    private fun returnItemsToPlayer(player: Player, container: Container) {
+        val inventory = player.inventory
+        for (i in 0 until container.containerSize) {
+            val stack = container.getItem(i)
+            if (!stack.isEmpty) {
+                if (!inventory.add(stack)) {
+                    player.drop(stack, false)
+                }
+                container.setItem(i, ItemStack.EMPTY)
+            }
+        }
+    }
+}

common/src/main/kotlin/com/cobblemon/mod/common/api/molangui/container/MolangSlot.kt

@@ -0,0 +1,28 @@
+/*
+ * Copyright (C) 2023 Cobblemon Contributors
+ *
+ * This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at https://mozilla.org/MPL/2.0/.
+ */
+
+package com.cobblemon.mod.common.api.molangui.container
+
+import net.minecraft.world.Container
+import net.minecraft.world.inventory.Slot
+import net.minecraft.world.item.ItemStack
+
+class MolangSlot(
+    container: Container,
+    index: Int,
+    x: Int,
+    y: Int,
+    private val collectionConfig: CollectionConfig
+) : Slot(container, index, x, y) {
+
+    override fun mayPlace(stack: ItemStack): Boolean {
+        return collectionConfig.isItemAllowed(stack) && container.canPlaceItem(containerSlot, stack)
+    }
+
+    override fun getMaxStackSize(stack: ItemStack): Int = container.getMaxStackSize(stack)
+}

common/src/main/kotlin/com/cobblemon/mod/common/api/molangui/container/SlotLayout.kt

@@ -0,0 +1,56 @@
+/*
+ * Copyright (C) 2023 Cobblemon Contributors
+ *
+ * This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at https://mozilla.org/MPL/2.0/.
+ */
+
+package com.cobblemon.mod.common.api.molangui.container
+
+import com.cobblemon.mod.common.api.molangui.MolangUiPacketLimits
+import net.minecraft.world.entity.player.Inventory
+
+data class SlotLayout(
+    val offsetX: Int,
+    val offsetY: Int,
+    val columns: Int,
+    val rows: Int,
+    val slotWidth: Int = 18,
+    val slotHeight: Int = 18,
+    val spacingX: Int = 0,
+    val spacingY: Int = 0
+) {
+    init {
+        require(columns in 1..MAX_GRID_DIMENSION && rows in 1..MAX_GRID_DIMENSION) { "slot grid dimensions must be in 1..$MAX_GRID_DIMENSION" }
+        validateAxis(offsetX, columns, slotWidth, spacingX)
+        validateAxis(offsetY, rows, slotHeight, spacingY)
+    }
+
+    val slotCount: Int get() = columns * rows
+
+    private fun validateAxis(offset: Int, count: Int, size: Int, spacing: Int) {
+        require(size > 0 && spacing >= 0) { "slot size must be positive and spacing nonnegative" }
+        val stride = size.toLong() + spacing
+        val lastSlotOffset = (count - 1) * stride
+        require(stride <= Int.MAX_VALUE && lastSlotOffset <= Int.MAX_VALUE && offset + lastSlotOffset + size <= Int.MAX_VALUE) {
+            "slot grid coordinates exceed the integer range"
+        }
+    }
+
+    companion object {
+        const val MAX_GRID_DIMENSION = 16
+
+        fun validateCollections(layouts: Map<String, SlotLayout>) {
+            require(layouts.size <= MolangUiPacketLimits.MAX_CONTRACTS) { "too many container collections" }
+            layouts.keys.forEach { name ->
+                MolangUiPacketLimits.requireIdentifier(name, "collection name")
+                require(name !in ShiftClickRule.PLAYER_SIDE_NAMES) { "collection name '$name' is reserved for player slots" }
+            }
+            // Native container packets encode slot indices as signed shorts.
+            require(layouts.values.sumOf { it.slotCount.toLong() } + Inventory.INVENTORY_SIZE <= Short.MAX_VALUE + 1L) {
+                "container slot indices exceed the native packet range"
+            }
+        }
+    }
+}

common/src/main/kotlin/com/cobblemon/mod/common/api/molangui/event/ClientEventProcessor.kt

@@ -0,0 +1,89 @@
+/*
+ * Copyright (C) 2023 Cobblemon Contributors
+ *
+ * This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at https://mozilla.org/MPL/2.0/.
+ */
+
+package com.cobblemon.mod.common.api.molangui.event
+
+import com.bedrockk.molang.runtime.MoLangRuntime
+import com.bedrockk.molang.runtime.struct.QueryStruct
+import com.bedrockk.molang.runtime.value.DoubleValue
+import com.bedrockk.molang.runtime.value.StringValue
+import com.cobblemon.mod.common.api.molangui.MolangUiPacketLimits
+import com.cobblemon.mod.common.Cobblemon
+import com.cobblemon.mod.common.api.molangui.widget.WidgetDefinition
+import com.cobblemon.mod.common.api.molangui.widget.WidgetInstance
+import com.cobblemon.mod.common.api.molangui.widget.WidgetType
+import com.cobblemon.mod.common.net.messages.server.molangui.MolangUiActionPacket
+import com.cobblemon.mod.common.util.asExpressionLike
+import java.util.UUID
+
+object ClientEventProcessor {
+
+    fun processEvent(
+        event: WidgetEvent,
+        widget: WidgetDefinition,
+        runtime: MoLangRuntime,
+        sessionId: UUID
+    ) {
+        val context = QueryStruct(hashMapOf())
+        event.data.forEach { (key, value) -> context.addFunction(key) { DoubleValue(value) } }
+        context.addFunction("type") { StringValue(event.type.id) }
+        context.addFunction("widget_id") { StringValue(event.widgetId) }
+        val functions = runtime.environment.query.functions
+        val previous = functions.remove("event")
+        runtime.environment.query.addFunction("event") { context }
+        try {
+            widget.clientEvents[event.type.clientId]?.asExpressionLike()?.resolve(runtime)
+            widget.events[event.type.id]?.let { serverHandler ->
+                // Action arguments may depend on variables changed by the client handler.
+                val parameters = serverHandler.parameters.mapValues { (_, property) -> property.resolveString(runtime) }
+                require(parameters.size <= MolangUiPacketLimits.MAX_ACTION_FIELDS) { "too many action parameters" }
+                parameters.forEach { (name, value) ->
+                    MolangUiPacketLimits.requireIdentifier(name, "action parameter")
+                    MolangUiPacketLimits.requireValue(value, name)
+                }
+                MolangUiActionPacket(sessionId, serverHandler.action.value, parameters).sendToServer()
+            }
+        } catch (error: Exception) {
+            Cobblemon.LOGGER.warn("Failed UI event {} on widget {}: {}", event.type.id, event.widgetId, error.message)
+        } finally {
+            functions.remove("event")
+            if (previous != null) functions["event"] = previous
+        }
+    }
+
+    fun hitTest(root: WidgetInstance, x: Float, y: Float): WidgetInstance? {
+        if (!root.visible || !root.enabled) return null
+        val isScrollPanel = root.definition.type == WidgetType.SCROLL_PANEL
+        if (isScrollPanel && !root.containsPoint(x, y)) return null
+
+        for (child in root.children.asReversed()) {
+            if (!child.visible) continue
+            val testY = if (isScrollPanel) y - root.scrollOffset else y
+            val hit = hitTest(child, x, testY)
+            if (hit != null) return hit
+        }
+        return if (root.containsPoint(x, y)) root else null
+    }
+}
+
+enum class WidgetEventType(val id: String) {
+    CLICK("on_click"),
+    CHANGE("on_change"),
+    HOVER_ENTER("on_hover_enter"),
+    HOVER_EXIT("on_hover_exit"),
+    SCROLL("on_scroll"),
+    KEY("on_key");
+
+    val clientId: String get() = "${id}_client"
+}
+
+data class WidgetEvent(
+    val type: WidgetEventType,
+    val widgetId: String,
+    val data: Map<String, Double> = emptyMap()
+)

common/src/main/kotlin/com/cobblemon/mod/common/api/molangui/layout/LayoutEngine.kt

@@ -0,0 +1,151 @@
+/*
+ * Copyright (C) 2023 Cobblemon Contributors
+ *
+ * This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at https://mozilla.org/MPL/2.0/.
+ */
+
+package com.cobblemon.mod.common.api.molangui.layout
+
+import com.cobblemon.mod.common.api.molangui.widget.WidgetInstance
+import com.bedrockk.molang.runtime.MoLangRuntime
+
+object LayoutEngine {
+
+    fun layout(root: WidgetInstance, screenWidth: Float, screenHeight: Float, runtime: MoLangRuntime): Unit = root.withItemContext(runtime) {
+        require(screenWidth.isFinite() && screenHeight.isFinite() && screenWidth >= 0f && screenHeight >= 0f) {
+            "invalid screen dimensions"
+        }
+        if (!root.visible) return@withItemContext
+        root.computedWidth = root.widthExpr.resolve(screenWidth, runtime)
+        root.computedHeight = root.heightExpr.resolve(screenHeight, runtime)
+        val anchor = root.definition.getAnchor()
+        val offsetX = root.offsetXExpr.resolve(screenWidth, runtime)
+        val offsetY = root.offsetYExpr.resolve(screenHeight, runtime)
+        root.absoluteX = (screenWidth - root.computedWidth) * anchor.xFactor + offsetX
+        root.absoluteY = (screenHeight - root.computedHeight) * anchor.yFactor + offsetY
+        validateBounds(root)
+        layoutChildren(root, runtime)
+    }
+
+    private fun layoutChildren(parent: WidgetInstance, runtime: MoLangRuntime): Unit = parent.withItemContext(runtime) {
+        val layout = parent.definition.getStringProperty("layout")
+        val spacing = parent.definition.getProperty("spacing")?.resolveFloat(runtime) ?: 0f
+        require(spacing.isFinite()) { "non-finite spacing at '${parent.definition.id}'" }
+        val padding = parent.paddingProperties.map { it.resolveFloat(runtime) }
+        require(padding.size == 4 && padding.all { it.isFinite() && it >= 0f }) {
+            "invalid padding at '${parent.definition.id}'"
+        }
+        val innerWidth = (parent.computedWidth - padding[3] - padding[1]).coerceAtLeast(0f)
+        val innerHeight = (parent.computedHeight - padding[0] - padding[2]).coerceAtLeast(0f)
+        val innerX = parent.absoluteX + padding[3]
+        val innerY = parent.absoluteY + padding[0]
+
+        for (child in parent.children) {
+            if (!child.visible) continue
+            child.computedWidth = child.withItemContext(runtime) { child.widthExpr.resolve(innerWidth, runtime) }
+            child.computedHeight = child.withItemContext(runtime) { child.heightExpr.resolve(innerHeight, runtime) }
+        }
+
+        when (layout) {
+            "stack_vertical" -> layoutStackVertical(parent, innerX, innerY, innerWidth, innerHeight, spacing, runtime)
+            "stack_horizontal" -> layoutStackHorizontal(parent, innerX, innerY, innerWidth, innerHeight, spacing, runtime)
+            "grid" -> layoutGrid(parent, innerX, innerY, innerWidth, spacing, runtime)
+            else -> layoutAnchored(parent, innerX, innerY, innerWidth, innerHeight, runtime)
+        }
+
+        for (child in parent.children) {
+            if (!child.visible) continue
+            validateBounds(child)
+            layoutChildren(child, runtime)
+        }
+    }
+
+    private fun layoutAnchored(parent: WidgetInstance, innerX: Float, innerY: Float, innerWidth: Float, innerHeight: Float, runtime: MoLangRuntime) {
+        for (child in parent.children) {
+            if (!child.visible) continue
+            val anchor = child.definition.getAnchor()
+            val offsetX = child.withItemContext(runtime) { child.offsetXExpr.resolve(innerWidth, runtime) }
+            val offsetY = child.withItemContext(runtime) { child.offsetYExpr.resolve(innerHeight, runtime) }
+            child.absoluteX = innerX + (innerWidth - child.computedWidth) * anchor.xFactor + offsetX
+            child.absoluteY = innerY + (innerHeight - child.computedHeight) * anchor.yFactor + offsetY
+        }
+    }
+
+    private fun layoutStackVertical(parent: WidgetInstance, innerX: Float, innerY: Float, innerWidth: Float, innerHeight: Float, spacing: Float, runtime: MoLangRuntime) {
+        val visibleChildren = parent.children.filter { it.visible }
+        resolveFillSizes(visibleChildren, innerHeight, spacing, isVertical = true)
+        var currentY = innerY
+        for (child in visibleChildren) {
+            child.absoluteX = innerX + child.withItemContext(runtime) { child.offsetXExpr.resolve(innerWidth, runtime) }
+            child.absoluteY = currentY + child.withItemContext(runtime) { child.offsetYExpr.resolve(innerHeight, runtime) }
+            currentY += child.computedHeight + spacing
+        }
+    }
+
+    private fun layoutStackHorizontal(parent: WidgetInstance, innerX: Float, innerY: Float, innerWidth: Float, innerHeight: Float, spacing: Float, runtime: MoLangRuntime) {
+        val visibleChildren = parent.children.filter { it.visible }
+        resolveFillSizes(visibleChildren, innerWidth, spacing, isVertical = false)
+        var currentX = innerX
+        for (child in visibleChildren) {
+            child.absoluteX = currentX + child.withItemContext(runtime) { child.offsetXExpr.resolve(innerWidth, runtime) }
+            child.absoluteY = innerY + child.withItemContext(runtime) { child.offsetYExpr.resolve(innerHeight, runtime) }
+            currentX += child.computedWidth + spacing
+        }
+    }
+
+    private fun layoutGrid(parent: WidgetInstance, innerX: Float, innerY: Float, innerWidth: Float, spacing: Float, runtime: MoLangRuntime) {
+        val columns = (parent.definition.getProperty("columns")?.resolveInt(runtime) ?: 1).coerceIn(1, 256)
+        val visibleChildren = parent.children.filter { it.visible }
+        val cellWidth = ((innerWidth - spacing * (columns - 1)) / columns).coerceAtLeast(0f)
+        var col = 0
+        var currentY = innerY
+        var rowHeight = 0f
+        for (child in visibleChildren) {
+            if (child.widthExpr is SizeExpression.Fill) child.computedWidth = cellWidth
+            child.absoluteX = innerX + col * (cellWidth + spacing)
+            child.absoluteY = currentY
+            rowHeight = maxOf(rowHeight, child.computedHeight)
+            col++
+            if (col >= columns) {
+                col = 0
+                currentY += rowHeight + spacing
+                rowHeight = 0f
+            }
+        }
+    }
+
+    private fun resolveFillSizes(children: List<WidgetInstance>, totalSpace: Float, spacing: Float, isVertical: Boolean) {
+        val totalSpacing = spacing * (children.size - 1).coerceAtLeast(0)
+        var usedSpace = totalSpacing
+        var fillCount = 0
+        for (child in children) {
+            val expr = if (isVertical) child.heightExpr else child.widthExpr
+            if (expr is SizeExpression.Fill) {
+                fillCount++
+            } else {
+                usedSpace += if (isVertical) child.computedHeight else child.computedWidth
+            }
+        }
+        if (fillCount > 0) {
+            val fillSize = ((totalSpace - usedSpace) / fillCount).coerceAtLeast(0f)
+            for (child in children) {
+                val expr = if (isVertical) child.heightExpr else child.widthExpr
+                if (expr is SizeExpression.Fill) {
+                    if (isVertical) child.computedHeight = fillSize else child.computedWidth = fillSize
+                }
+            }
+        }
+    }
+
+    private fun validateBounds(widget: WidgetInstance) {
+        fun validAxis(position: Float, size: Float): Boolean =
+            position.isFinite() && size.isFinite() && size >= 0f && size.toDouble() <= Int.MAX_VALUE &&
+                position.toDouble() >= Int.MIN_VALUE && position.toDouble() + size.toDouble() <= Int.MAX_VALUE
+
+        require(validAxis(widget.absoluteX, widget.computedWidth) && validAxis(widget.absoluteY, widget.computedHeight)) {
+            "widget '${widget.definition.id}' has invalid or overflowing bounds"
+        }
+    }
+}

common/src/main/kotlin/com/cobblemon/mod/common/api/molangui/layout/SizeExpression.kt

@@ -0,0 +1,75 @@
+/*
+ * Copyright (C) 2023 Cobblemon Contributors
+ *
+ * This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at https://mozilla.org/MPL/2.0/.
+ */
+
+package com.cobblemon.mod.common.api.molangui.layout
+
+import com.cobblemon.mod.common.api.molang.ExpressionLike
+import com.cobblemon.mod.common.util.asExpressionLike
+import com.bedrockk.molang.runtime.MoLangRuntime
+import com.cobblemon.mod.common.api.molangui.widget.WidgetExpression
+
+sealed class SizeExpression {
+    abstract fun resolve(parentSize: Float, runtime: MoLangRuntime): Float
+
+    data class Pixels(val value: Float) : SizeExpression() {
+        init { require(value.isFinite()) { "pixel size must be finite" } }
+        override fun resolve(parentSize: Float, runtime: MoLangRuntime) = value
+    }
+
+    data class Percent(val fraction: Float) : SizeExpression() {
+        init { require(fraction.isFinite()) { "percentage must be finite" } }
+        override fun resolve(parentSize: Float, runtime: MoLangRuntime) = parentSize * fraction
+    }
+
+    data class PercentWithOffset(val fraction: Float, val offset: Float) : SizeExpression() {
+        init { require(fraction.isFinite() && offset.isFinite()) { "percentage and offset must be finite" } }
+        override fun resolve(parentSize: Float, runtime: MoLangRuntime) = parentSize * fraction + offset
+    }
+
+    data object Fill : SizeExpression() {
+        override fun resolve(parentSize: Float, runtime: MoLangRuntime) = parentSize
+    }
+
+    data class MolangSize(val expression: ExpressionLike) : SizeExpression() {
+        override fun resolve(parentSize: Float, runtime: MoLangRuntime) = expression.resolveFloat(runtime)
+    }
+
+    companion object {
+        private val PERCENT_PATTERN = Regex("""^(\d+(?:\.\d+)?)%$""")
+        private val PERCENT_OFFSET_PATTERN = Regex("""^(\d+(?:\.\d+)?)%\s*([+-])\s*(\d+(?:\.\d+)?)$""")
+
+        fun parse(value: Any): SizeExpression {
+            return when (value) {
+                is Number -> Pixels(value.toFloat())
+                is String -> parseString(value)
+                is WidgetExpression -> MolangSize(value.source.asExpressionLike())
+                else -> throw IllegalArgumentException("size must be a number, percentage, fill, or explicit Molang expression")
+            }
+        }
+
+        private fun parseString(value: String): SizeExpression {
+            val trimmed = value.trim()
+            return when {
+                trimmed == "fill" -> Fill
+                trimmed.toFloatOrNull() != null -> Pixels(trimmed.toFloat())
+                PERCENT_PATTERN.matches(trimmed) -> {
+                    val pct = PERCENT_PATTERN.matchEntire(trimmed)!!.groupValues[1].toFloat()
+                    Percent(pct / 100f)
+                }
+                PERCENT_OFFSET_PATTERN.matches(trimmed) -> {
+                    val match = PERCENT_OFFSET_PATTERN.matchEntire(trimmed)!!
+                    val pct = match.groupValues[1].toFloat() / 100f
+                    val sign = if (match.groupValues[2] == "+") 1f else -1f
+                    val offset = match.groupValues[3].toFloat() * sign
+                    PercentWithOffset(pct, offset)
+                }
+                else -> throw IllegalArgumentException("invalid size '$value'; Molang requires an explicit expression object")
+            }
+        }
+    }
+}

common/src/main/kotlin/com/cobblemon/mod/common/api/molangui/template/TemplateLibraryRegistry.kt

@@ -0,0 +1,114 @@
+/*
+ * Copyright (C) 2023 Cobblemon Contributors
+ *
+ * This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at https://mozilla.org/MPL/2.0/.
+ */
+
+package com.cobblemon.mod.common.api.molangui.template
+
+import com.google.gson.Gson
+import com.google.gson.JsonObject
+import com.google.gson.JsonElement
+import net.minecraft.resources.ResourceLocation
+import net.minecraft.server.packs.resources.ResourceManager
+import com.cobblemon.mod.common.Cobblemon
+
+
+object TemplateLibraryRegistry {
+    private val gson = Gson()
+    private val libraries: MutableMap<ResourceLocation, Map<String, TemplateDefinition>> = mutableMapOf()
+
+    private const val DIRECTORY = "molang_ui/templates"
+
+    fun reload(manager: ResourceManager) {
+        val next = mutableMapOf<ResourceLocation, Map<String, TemplateDefinition>>()
+        val resources = manager.listResources(DIRECTORY) { it.path.endsWith(".json") }
+        for ((location, resource) in resources) {
+            try {
+                val json = resource.openAsReader().use { gson.fromJson(it, JsonObject::class.java) }
+                val namespace = location.namespace
+                val name = location.path.removePrefix("$DIRECTORY/").removeSuffix(".json")
+                val libraryId = ResourceLocation.fromNamespaceAndPath(namespace, name)
+                val templates = parseTemplates(json, namespace)
+                next[libraryId] = templates
+            } catch (e: Exception) {
+                Cobblemon.LOGGER.error("Rejected Molang UI template library '$location': ${e.message}")
+            }
+        }
+        libraries.clear()
+        libraries.putAll(next)
+    }
+
+    fun getTemplate(qualifiedName: String): TemplateDefinition? {
+        val dotIndex = qualifiedName.lastIndexOf('.')
+        if (dotIndex == -1) return null
+        val libraryName = qualifiedName.substring(0, dotIndex)
+        val templateName = qualifiedName.substring(dotIndex + 1)
+        val library = if (':' in libraryName) {
+            ResourceLocation.tryParse(libraryName)?.let(libraries::get)
+        } else {
+            libraries.entries.singleOrNull { it.key.path == libraryName }?.value
+        }
+        return library?.get(templateName)
+    }
+
+    private fun parseTemplates(json: JsonObject, namespace: String): Map<String, TemplateDefinition> {
+        val result = mutableMapOf<String, TemplateDefinition>()
+        val templatesObj = json.getAsJsonObject("templates") ?: return result
+        for ((name, element) in templatesObj.entrySet()) {
+            val templateJson = element.asJsonObject
+            val inputs = mutableMapOf<String, TemplateInput>()
+            templateJson.getAsJsonObject("inputs")?.let { inputsObj ->
+                for ((inputName, inputEl) in inputsObj.entrySet()) {
+                    val inputObj = inputEl.asJsonObject
+                    val type = TemplateInputType.fromId(inputObj.get("type")?.asString ?: "string")
+                        ?: throw IllegalArgumentException("unknown template input type for '$inputName'")
+                    val default = inputObj.get("default")
+                    require(default == null || type.accepts(default)) { "invalid template default at '$name.$inputName'" }
+                    inputs[inputName] = TemplateInput(type, default)
+                }
+            }
+            val extends = templateJson.get("extends")?.asString
+            result[name] = TemplateDefinition(
+                name = name,
+                namespace = namespace,
+                inputs = inputs,
+                extends = extends,
+                body = templateJson
+            )
+        }
+        return result
+    }
+}
+
+data class TemplateDefinition(
+    val name: String,
+    val namespace: String,
+    val inputs: Map<String, TemplateInput> = emptyMap(),
+    val extends: String? = null,
+    val body: JsonObject
+)
+
+data class TemplateInput(
+    val type: TemplateInputType = TemplateInputType.STRING,
+    val default: JsonElement? = null
+)
+
+enum class TemplateInputType(val id: String) {
+    STRING("string"), NUMBER("number"), BOOLEAN("boolean"), EXPRESSION("expression"), OBJECT("object"), ARRAY("array");
+
+    fun accepts(value: JsonElement): Boolean = when (this) {
+        STRING -> value.isJsonPrimitive && value.asJsonPrimitive.isString
+        NUMBER -> value.isJsonPrimitive && value.asJsonPrimitive.isNumber && value.asDouble.isFinite()
+        BOOLEAN -> value.isJsonPrimitive && value.asJsonPrimitive.isBoolean
+        EXPRESSION -> value.isJsonObject && value.asJsonObject.size() == 1 && value.asJsonObject.get("molang")?.let {
+            it.isJsonPrimitive && it.asJsonPrimitive.isString
+        } == true
+        OBJECT -> value.isJsonObject
+        ARRAY -> value.isJsonArray
+    }
+
+    companion object { fun fromId(id: String) = entries.firstOrNull { it.id == id } }
+}

common/src/main/kotlin/com/cobblemon/mod/common/api/molangui/template/TemplateResolver.kt

@@ -0,0 +1,135 @@
+/*
+ * Copyright (C) 2023 Cobblemon Contributors
+ *
+ * This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at https://mozilla.org/MPL/2.0/.
+ */
+
+package com.cobblemon.mod.common.api.molangui.template
+
+import com.cobblemon.mod.common.api.molangui.widget.WidgetTree
+import com.google.gson.JsonArray
+import com.google.gson.JsonElement
+import com.google.gson.JsonObject
+import com.google.gson.JsonPrimitive
+
+object TemplateResolver {
+    fun resolve(root: JsonObject, localTemplates: Map<String, TemplateDefinition>): JsonObject =
+        Resolution(localTemplates).resolveNode(root, emptyList(), 1)
+
+    private class Resolution(private val localTemplates: Map<String, TemplateDefinition>) {
+        private var nodes = 0
+        private var values = 0
+
+        fun resolveNode(node: JsonObject, chain: List<String>, depth: Int): JsonObject {
+            require(depth <= WidgetTree.MAX_DEPTH) { "template expansion exceeds maximum widget depth ${WidgetTree.MAX_DEPTH}" }
+            require(++nodes <= WidgetTree.MAX_NODES) { "template expansion exceeds maximum widget count ${WidgetTree.MAX_NODES}" }
+            val result = JsonObject()
+            node.entrySet().filter { it.key != "controls" && it.key != "item_template" }.forEach { (key, value) ->
+                result.add(key, copy(value))
+            }
+            node.getAsJsonArray("controls")?.let { controls ->
+                val resolvedControls = JsonArray()
+                controls.forEach { element ->
+                    val wrapper = element.takeIf(JsonElement::isJsonObject)?.asJsonObject
+                        ?: throw IllegalArgumentException("control entries must be objects")
+                    require(wrapper.size() == 1) { "control entries must contain exactly one widget" }
+                    val (key, value) = wrapper.entrySet().single()
+                    val output = JsonObject()
+                    require(value.isJsonObject) { "widget '$key' must be an object" }
+                    output.add(key.substringBefore('@'), resolveWidgetEntry(key, value.asJsonObject, chain, depth + 1))
+                    resolvedControls.add(output)
+                }
+                result.add("controls", resolvedControls)
+            }
+            node.getAsJsonObject("item_template")?.let {
+                result.add("item_template", resolveNode(it, chain, depth + 1))
+            }
+            return result
+        }
+
+        private fun resolveWidgetEntry(
+            key: String,
+            overrides: JsonObject,
+            chain: List<String>,
+            depth: Int
+        ): JsonObject {
+            if ('@' !in key) return resolveNode(overrides, chain, depth)
+            val templateRef = key.substringAfter('@')
+            require(templateRef !in chain) { "template expansion cycle: ${(chain + templateRef).joinToString(" -> ")}" }
+            require(depth <= WidgetTree.MAX_DEPTH) { "template expansion exceeds maximum widget depth ${WidgetTree.MAX_DEPTH}" }
+            val template = findTemplate(templateRef)
+                ?: throw IllegalArgumentException("missing template '$templateRef'")
+            val inherited = resolveTemplateChain(templateRef, template, emptyList())
+            val inputs = inherited.inputs.mapValues { (name, input) ->
+                val supplied = overrides.get(name)
+                val value = supplied ?: input.default
+                    ?: throw IllegalArgumentException("missing required template input '$name' for '$templateRef'")
+                require(input.type.accepts(value)) {
+                    "template input '$name' for '$templateRef' must be ${input.type.id}"
+                }
+                value
+            }
+            val substituted = copy(inherited.body, inputs).asJsonObject
+            val nonInputs = JsonObject().also { obj ->
+                overrides.entrySet().filter { it.key !in inherited.inputs }.forEach { (name, value) -> obj.add(name, value) }
+            }
+            return resolveNode(mergeJson(substituted, nonInputs), chain + templateRef, depth)
+        }
+
+        private fun resolveTemplateChain(
+            ref: String,
+            template: TemplateDefinition,
+            chain: List<String>
+        ): TemplateDefinition {
+            require(ref !in chain) { "template inheritance cycle: ${(chain + ref).joinToString(" -> ")}" }
+            require(chain.size < WidgetTree.MAX_DEPTH) { "template inheritance exceeds maximum depth ${WidgetTree.MAX_DEPTH}" }
+            val nextChain = chain + ref
+            val body = JsonObject().also { obj ->
+                template.body.entrySet().filter { it.key != "inputs" && it.key != "extends" }
+                    .forEach { (name, value) -> obj.add(name, value) }
+            }
+            val parentRef = template.extends ?: return template.copy(body = body)
+            val parent = findTemplate(parentRef)
+                ?: throw IllegalArgumentException("missing parent template '$parentRef' referenced by '$ref'")
+            val inherited = resolveTemplateChain(parentRef, parent, nextChain)
+            return template.copy(inputs = inherited.inputs + template.inputs, body = mergeJson(inherited.body, body))
+        }
+
+        private fun findTemplate(ref: String) =
+            localTemplates[ref] ?: TemplateLibraryRegistry.getTemplate(ref)
+
+        private fun copy(element: JsonElement, inputs: Map<String, JsonElement>? = null, depth: Int = 0): JsonElement {
+            require(depth <= 128) { "template JSON exceeds maximum depth 128" }
+            require(++values <= 1_048_576) { "template expansion exceeds maximum JSON work" }
+            if (inputs != null && element.isJsonPrimitive && element.asJsonPrimitive.isString) {
+                val text = element.asString
+                if (text.startsWith('$') && text.length > 1 && text.indexOf('$', 1) == -1) {
+                    val supplied = inputs[text.substring(1)]
+                        ?: throw IllegalArgumentException("unknown template input reference '$text'")
+                    return copy(supplied, depth = depth + 1)
+                }
+                return JsonPrimitive(text)
+            }
+            if (element.isJsonArray) return JsonArray().also { out -> element.asJsonArray.forEach { out.add(copy(it, inputs, depth + 1)) } }
+            if (element.isJsonObject) return JsonObject().also { out ->
+                element.asJsonObject.entrySet().forEach { (key, value) ->
+                    out.add(key, copy(value, inputs, depth + 1))
+                }
+            }
+            return element.deepCopy()
+        }
+
+        private fun mergeJson(base: JsonObject, overlay: JsonObject): JsonObject {
+            val result = copy(base).asJsonObject
+            overlay.entrySet().forEach { (key, value) ->
+                val existing = result.get(key)
+                result.add(key, if (value.isJsonObject && existing?.isJsonObject == true) {
+                    mergeJson(existing.asJsonObject, value.asJsonObject)
+                } else copy(value))
+            }
+            return result
+        }
+    }
+}

common/src/main/kotlin/com/cobblemon/mod/common/api/molangui/widget/WidgetDefinition.kt

@@ -0,0 +1,68 @@
+/*
+ * Copyright (C) 2023 Cobblemon Contributors
+ *
+ * This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at https://mozilla.org/MPL/2.0/.
+ */
+
+package com.cobblemon.mod.common.api.molangui.widget
+
+import com.cobblemon.mod.common.api.molangui.ActionKey
+
+data class WidgetDefinition(
+    val id: String,
+    val type: WidgetType,
+    val properties: Map<String, WidgetProperty> = emptyMap(),
+    val children: List<WidgetDefinition> = emptyList(),
+    val events: Map<String, ServerWidgetEvent> = emptyMap(),
+    val clientEvents: Map<String, String> = emptyMap(),
+    val hoverOverrides: Map<String, WidgetProperty> = emptyMap(),
+    val itemTemplate: WidgetDefinition? = null
+) {
+    fun getProperty(name: String): WidgetProperty? = properties[name]
+    fun getStringProperty(name: String): String? = (properties[name]?.raw as? String)
+    fun getAnchor(): Anchor = Anchor.fromId(getStringProperty("anchor") ?: "top_left")
+}
+
+data class ServerWidgetEvent(
+    val action: ActionKey,
+    val parameters: Map<String, WidgetProperty> = emptyMap()
+)
+
+enum class WidgetType(val id: String) {
+    PANEL("panel"),
+    LABEL("label"),
+    IMAGE("image"),
+    FILL("fill"),
+    BUTTON("button"),
+    LIST("list"),
+    PROGRESS_BAR("progress_bar"),
+    SCROLL_PANEL("scroll_panel"),
+    POKEMON_RENDER("pokemon_render"),
+    NUMBER_INPUT("number_input"),
+    ITEM_SLOT("item_slot"),
+    SLOT_GRID("slot_grid");
+
+    companion object {
+        private val BY_ID = entries.associateBy { it.id }
+        fun fromId(id: String): WidgetType? = BY_ID[id]
+    }
+}
+
+enum class Anchor(val id: String, val xFactor: Float, val yFactor: Float) {
+    TOP_LEFT("top_left", 0f, 0f),
+    TOP_CENTER("top_center", 0.5f, 0f),
+    TOP_RIGHT("top_right", 1f, 0f),
+    CENTER_LEFT("center_left", 0f, 0.5f),
+    CENTER("center", 0.5f, 0.5f),
+    CENTER_RIGHT("center_right", 1f, 0.5f),
+    BOTTOM_LEFT("bottom_left", 0f, 1f),
+    BOTTOM_CENTER("bottom_center", 0.5f, 1f),
+    BOTTOM_RIGHT("bottom_right", 1f, 1f);
+
+    companion object {
+        private val BY_ID = entries.associateBy { it.id }
+        fun fromId(id: String): Anchor = BY_ID[id] ?: TOP_LEFT
+    }
+}

common/src/main/kotlin/com/cobblemon/mod/common/api/molangui/widget/WidgetExpansion.kt

@@ -0,0 +1,92 @@
+/*
+ * Copyright (C) 2023 Cobblemon Contributors
+ *
+ * This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at https://mozilla.org/MPL/2.0/.
+ */
+
+package com.cobblemon.mod.common.api.molangui.widget
+
+import com.bedrockk.molang.runtime.MoLangRuntime
+import com.bedrockk.molang.runtime.struct.QueryStruct
+import com.bedrockk.molang.runtime.value.DoubleValue
+import com.bedrockk.molang.runtime.value.MoValue
+import com.bedrockk.molang.runtime.value.StringValue
+import com.cobblemon.mod.common.api.molangui.MolangUiPacketLimits
+import com.cobblemon.mod.common.api.molangui.layout.SizeExpression
+import com.google.gson.JsonElement
+import com.google.gson.JsonParser
+
+internal object WidgetExpansion {
+    private data class Node(val definition: WidgetDefinition, val context: QueryStruct?, val children: List<Node>)
+
+    fun refresh(definition: WidgetDefinition, runtime: MoLangRuntime, previous: WidgetInstance? = null): WidgetInstance {
+        var count = 0
+        fun plan(def: WidgetDefinition, context: QueryStruct?, depth: Int): Node = withItemContext(runtime, context) {
+            require(depth <= WidgetTree.MAX_DEPTH && ++count <= WidgetTree.MAX_NODES) {
+                "expanded widget tree exceeds ${WidgetTree.MAX_NODES} widgets or depth ${WidgetTree.MAX_DEPTH}"
+            }
+            val children = if (def.type == WidgetType.LIST) {
+                val template = requireNotNull(def.itemTemplate) { "list '${def.id}' requires item_template" }
+                items(def, runtime).mapIndexed { index, values ->
+                    val item = QueryStruct(hashMapOf())
+                    values.forEach { (key, value) -> item.addFunction(key) { value } }
+                    item.addFunction("index") { DoubleValue(index.toDouble()) }
+                    plan(template.copy(id = "${template.id}[$index]"), item, depth + 1)
+                }
+            } else def.children.map { plan(it, context, depth + 1) }
+            Node(def, context, children)
+        }
+        val planned = plan(definition, null, 1)
+        fun apply(node: Node, old: WidgetInstance?, parent: WidgetInstance?): WidgetInstance {
+            val widget = old?.takeIf { it.definition == node.definition } ?: WidgetInstance(node.definition, parent).apply {
+                val size = node.definition.getProperty("size")?.raw as? List<*>
+                if (size?.size == 2) {
+                    widthExpr = SizeExpression.parse(size[0] ?: 0)
+                    heightExpr = SizeExpression.parse(size[1] ?: 0)
+                }
+                val offset = node.definition.getProperty("offset")?.raw as? List<*>
+                if (offset?.size == 2) {
+                    offsetXExpr = SizeExpression.parse(offset[0] ?: 0)
+                    offsetYExpr = SizeExpression.parse(offset[1] ?: 0)
+                }
+            }
+            widget.itemContext = node.context
+            val children = node.children.mapIndexed { index, child -> apply(child, widget.children.getOrNull(index), widget) }
+            widget.children.clear()
+            widget.children.addAll(children)
+            return widget
+        }
+        return apply(planned, previous, null)
+    }
+
+    private fun items(definition: WidgetDefinition, runtime: MoLangRuntime): List<Map<String, MoValue>> =
+        when (definition.getStringProperty("source_type") ?: "data") {
+            "count" -> {
+                val count = definition.getProperty("source")?.resolveDouble(runtime) ?: 0.0
+                require(count.isFinite() && count in 0.0..WidgetTree.MAX_NODES.toDouble() && count % 1.0 == 0.0) {
+                    "list '${definition.id}' requires a whole count between 0 and ${WidgetTree.MAX_NODES}"
+                }
+                List(count.toInt()) { emptyMap() }
+            }
+            "data" -> {
+                val source = definition.getProperty("source")?.resolveString(runtime) ?: "[]"
+                require(source.length <= MolangUiPacketLimits.MAX_VALUE_LENGTH) { "list '${definition.id}' source is too large" }
+                val array = JsonParser.parseString(source).asJsonArray
+                require(array.size() <= WidgetTree.MAX_NODES) { "list '${definition.id}' has too many items" }
+                array.map { element -> element.asJsonObject.entrySet().associate { (key, item) -> key to value(item) } }
+            }
+            else -> throw IllegalArgumentException("unsupported list source_type at '${definition.id}'")
+        }
+
+    private fun value(element: JsonElement): MoValue {
+        if (!element.isJsonPrimitive) return StringValue(element.toString())
+        val primitive = element.asJsonPrimitive
+        return when {
+            primitive.isBoolean -> DoubleValue(primitive.asBoolean)
+            primitive.isNumber -> DoubleValue(primitive.asDouble.also { require(it.isFinite()) { "non-finite list item value" } })
+            else -> StringValue(primitive.asString)
+        }
+    }
+}

common/src/main/kotlin/com/cobblemon/mod/common/api/molangui/widget/WidgetInstance.kt

@@ -0,0 +1,67 @@
+/*
+ * Copyright (C) 2023 Cobblemon Contributors
+ *
+ * This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at https://mozilla.org/MPL/2.0/.
+ */
+
+package com.cobblemon.mod.common.api.molangui.widget
+
+import com.cobblemon.mod.common.api.molangui.layout.SizeExpression
+import com.bedrockk.molang.runtime.MoLangRuntime
+import com.bedrockk.molang.runtime.struct.QueryStruct
+
+class WidgetInstance(
+    val definition: WidgetDefinition,
+    val parent: WidgetInstance? = null
+) {
+    var absoluteX: Float = 0f
+    var absoluteY: Float = 0f
+    var computedWidth: Float = 0f
+    var computedHeight: Float = 0f
+
+    var widthExpr: SizeExpression = SizeExpression.Pixels(0f)
+    var heightExpr: SizeExpression = SizeExpression.Pixels(0f)
+    var offsetXExpr: SizeExpression = SizeExpression.Pixels(0f)
+    var offsetYExpr: SizeExpression = SizeExpression.Pixels(0f)
+
+    internal val paddingProperties: List<WidgetProperty> =
+        (definition.getProperty("padding")?.raw as? List<*>)?.map {
+            when (it) {
+                is Number -> WidgetProperty.literal(it)
+                is WidgetExpression -> WidgetProperty.molang(it.source)
+                else -> throw IllegalArgumentException("invalid padding at '${definition.id}'")
+            }
+        } ?: List(4) { WidgetProperty.literal(0) }
+
+    val children: MutableList<WidgetInstance> = mutableListOf()
+
+    var visible: Boolean = true
+    var enabled: Boolean = true
+    var hovered: Boolean = false
+
+    var scrollOffset: Float = 0f
+    var rendererState: Any? = null
+    var itemContext: QueryStruct? = null
+
+    inline fun <T> withItemContext(runtime: MoLangRuntime, action: () -> T): T =
+        withItemContext(runtime, itemContext, action)
+
+    fun containsPoint(x: Float, y: Float): Boolean {
+        return x >= absoluteX && x <= absoluteX + computedWidth &&
+               y >= absoluteY && y <= absoluteY + computedHeight
+    }
+}
+
+inline fun <T> withItemContext(runtime: MoLangRuntime, context: QueryStruct?, action: () -> T): T {
+    val functions = runtime.environment.query.functions
+    val previous = functions.remove("item")
+    if (context != null) runtime.environment.query.addFunction("item") { context }
+    try {
+        return action()
+    } finally {
+        functions.remove("item")
+        if (previous != null) functions["item"] = previous
+    }
+}

common/src/main/kotlin/com/cobblemon/mod/common/api/molangui/widget/WidgetProperty.kt

@@ -0,0 +1,63 @@
+/*
+ * Copyright (C) 2023 Cobblemon Contributors
+ *
+ * This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at https://mozilla.org/MPL/2.0/.
+ */
+
+package com.cobblemon.mod.common.api.molangui.widget
+
+import com.cobblemon.mod.common.api.molang.ExpressionLike
+import com.cobblemon.mod.common.util.asExpressionLike
+import com.bedrockk.molang.runtime.MoLangRuntime
+
+class WidgetProperty private constructor(val raw: Any, expressionSource: String?) {
+    val expression: ExpressionLike? = expressionSource?.asExpressionLike()
+
+    fun resolveDouble(runtime: MoLangRuntime): Double {
+        return expression?.resolveDouble(runtime) ?: when (raw) {
+            is Number -> raw.toDouble()
+            is String -> parseNumericString(raw)
+            is Boolean -> if (raw) 1.0 else 0.0
+            else -> 0.0
+        }
+    }
+
+    fun resolveString(runtime: MoLangRuntime): String {
+        return expression?.resolveString(runtime) ?: raw.toString()
+    }
+
+    fun resolveBoolean(runtime: MoLangRuntime): Boolean {
+        return expression?.resolveBoolean(runtime) ?: when (raw) {
+            is Boolean -> raw
+            is Number -> raw.toDouble() != 0.0
+            is String -> raw.toBooleanStrictOrNull() ?: (raw.isNotEmpty())
+            else -> false
+        }
+    }
+
+    fun resolveInt(runtime: MoLangRuntime): Int {
+        if (expression == null && raw is String && raw.startsWith("0x", ignoreCase = true)) {
+            return raw.substring(2).toLongOrNull(16)?.toInt() ?: 0
+        }
+        return resolveDouble(runtime).toInt()
+    }
+
+    fun resolveFloat(runtime: MoLangRuntime): Float = resolveDouble(runtime).toFloat()
+
+    companion object {
+        fun literal(value: Any): WidgetProperty = WidgetProperty(value, null)
+        fun molang(source: String): WidgetProperty = WidgetProperty(source, source)
+
+        private fun parseNumericString(value: String): Double {
+            value.toDoubleOrNull()?.let { return it }
+            if (value.startsWith("0x", ignoreCase = true)) {
+                value.substring(2).toLongOrNull(16)?.let { return it.toDouble() }
+            }
+            return 0.0
+        }
+    }
+}
+
+data class WidgetExpression(val source: String)