docs: detail multi-Pokémon trading and trade UI changes in the changelog

Resolve conflicts with the trade dupe fix and per-OT trade friendship
caching by applying both to every Pokémon in a multi-Pokémon trade.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

CHANGELOG.md

@@ -85,6 +85,16 @@
 - Bellossom
 
 ### Changes
+- Restructured Botany Pots integration folder structure
+- Decrease default pastured mon wander radius to 32.
+- Factor in the weight of pokemon when calculating pushing forces between hitboxes.
+- Remade the Starter Selection Screen with new assets
+- Refactored berry trees to be less impactful on TPS (more performant)
+- Trading has been overhauled to allow offering multiple Pokémon, up to the entire party, in a single trade
+  - Selected Pokémon are now highlighted in both parties with new party slot assets
+  - Hovering an offered Pokémon now shows its summary, and clicking the active Pokémon no longer exits the summary view
+  - The trade animation now moves the offered Pokémon towards the Poké Ball
+  - Parties are compacted after a trade so no empty slots are left between Pokémon
 - Terrain Seeds can now be planted
 - Terrain Seeds are now consumed during PvP and NPC battles
 - Glow Item Frames can be crafted using Bright Powder as an alternative to Glow Ink Sacs
@@ -133,6 +143,11 @@
 - Fixed Safari Ball catch rate outside of battle
 
 ### Developer
+- Added `PokeSnackSpawnerFactory` which allows influence registration on PokeSnack encounters
+- Added `FishingSpawnerFactory` which allows influence registration on fishing encounters
+- Added `BattleFleeAttemptEvent` fired from `PokemonBattle.checkFleeAttempt`, allowing developers to intercept and control flee attempts
+- Trade network packets (`TradeUpdatedPacket`, `UpdateTradeOfferPacket`, and `TradeCompletedPacket`) now receive an array of Pokémon instead of a single Pokémon to execute trades
+- `TradeEvent.Pre` and `TradeEvent.Post` now expose every Pokémon each participant receives (`tradeParticipant1Pokemon` and `tradeParticipant2Pokemon` are now lists), and their Molang context includes `trade_participant_1_pokemon_list` and `trade_participant_2_pokemon_list`
 - Evolution requirements can now set `pokedexIcon` and `pokedexTooltip` directly in their JSON to control how they're shown on the Pokédex's evolution tree, for example:
   ```json
   {

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

@@ -9,12 +9,14 @@
 package com.cobblemon.mod.common.api.events.pokemon
 
 import com.bedrockk.molang.runtime.value.DoubleValue
+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.entity.pokemon.PokemonEntity
 import com.cobblemon.mod.common.pokemon.Pokemon
 import com.cobblemon.mod.common.trade.TradeParticipant
+import com.cobblemon.mod.common.util.asArrayValue
 import com.cobblemon.mod.common.util.getPlayer
 
 /**
@@ -31,9 +33,9 @@ interface TradeEvent {
     val tradeParticipant1: TradeParticipant
 
     /**
-     * The [Pokemon] being traded by the first participant.
+     * All the [Pokemon] the first participant receives in the trade.
      */
-    val tradeParticipant1Pokemon: Pokemon
+    val tradeParticipant1Pokemon: List<Pokemon>
 
     /**
      * The second [TradeParticipant].
@@ -41,9 +43,19 @@ interface TradeEvent {
     val tradeParticipant2: TradeParticipant
 
     /**
-     * The [Pokemon] being traded by the second participant.
+     * All the [Pokemon] the second participant receives in the trade.
      */
-    val tradeParticipant2Pokemon: Pokemon
+    val tradeParticipant2Pokemon: List<Pokemon>
+
+    fun createContext(): MutableMap<String, MoValue> = mutableMapOf(
+        "trade_participant_1" to (tradeParticipant1.uuid.getPlayer()?.asMoLangValue() ?: DoubleValue.ZERO),
+        "trade_participant_2" to (tradeParticipant2.uuid.getPlayer()?.asMoLangValue() ?: DoubleValue.ZERO),
+        // Kept for backwards compatibility, this is the first Pokémon of each side.
+        "trade_participant_1_pokemon" to tradeParticipant1Pokemon.first().struct,
+        "trade_participant_2_pokemon" to tradeParticipant2Pokemon.first().struct,
+        "trade_participant_1_pokemon_list" to tradeParticipant1Pokemon.asArrayValue { it.struct },
+        "trade_participant_2_pokemon_list" to tradeParticipant2Pokemon.asArrayValue { it.struct }
+    )
 
     /**
      * Event fired when a trade is about to happen. Cancelling this event prevents the trade from occurring.
@@ -53,16 +65,11 @@ interface TradeEvent {
      */
     data class Pre(
         override val tradeParticipant1: TradeParticipant,
-        override val tradeParticipant1Pokemon: Pokemon,
+        override val tradeParticipant1Pokemon: List<Pokemon>,
         override val tradeParticipant2: TradeParticipant,
-        override val tradeParticipant2Pokemon: Pokemon
+        override val tradeParticipant2Pokemon: List<Pokemon>
     ) : TradeEvent, Cancelable() {
-        val context = mutableMapOf(
-            "trade_participant_1" to (tradeParticipant1.uuid.getPlayer()?.asMoLangValue() ?: DoubleValue.ZERO),
-            "trade_participant_2" to (tradeParticipant2.uuid.getPlayer()?.asMoLangValue() ?: DoubleValue.ZERO),
-            "trade_participant_1_pokemon" to tradeParticipant1Pokemon.struct,
-            "trade_participant_2_pokemon" to tradeParticipant2Pokemon.struct
-        )
+        val context = createContext()
 
         val functions = moLangFunctionMap(
             cancelFunc
@@ -77,15 +84,10 @@ interface TradeEvent {
      */
     data class Post(
         override val tradeParticipant1: TradeParticipant,
-        override val tradeParticipant1Pokemon: Pokemon,
+        override val tradeParticipant1Pokemon: List<Pokemon>,
         override val tradeParticipant2: TradeParticipant,
-        override val tradeParticipant2Pokemon: Pokemon
+        override val tradeParticipant2Pokemon: List<Pokemon>
     ) : TradeEvent {
-        val context = mutableMapOf(
-            "trade_participant_1" to (tradeParticipant1.uuid.getPlayer()?.asMoLangValue() ?: DoubleValue.ZERO),
-            "trade_participant_2" to (tradeParticipant2.uuid.getPlayer()?.asMoLangValue() ?: DoubleValue.ZERO),
-            "trade_participant_1_pokemon" to tradeParticipant1Pokemon.struct,
-            "trade_participant_2_pokemon" to tradeParticipant2Pokemon.struct
-        )
+        val context = createContext()
     }
 }

common/src/main/kotlin/com/cobblemon/mod/common/client/gui/trade/PartySlot.kt

@@ -28,9 +28,9 @@ import org.joml.Vector3f
 
 open class PartySlot(
     x: Int, y: Int,
-    private val pokemon: TradeStartedPacket.TradeablePokemon?,
+    val pokemon: TradeStartedPacket.TradeablePokemon?,
     private val parent: TradeGUI,
-    private val isOpposing: Boolean = false,
+    val isOpposing: Boolean = false,
     onPress: OnPress
 ) : Button(x, y, SIZE, SIZE, Component.literal("PartySlot"), onPress, DEFAULT_NARRATION), CobblemonRenderable {
     val state = FloatingState()
@@ -42,6 +42,8 @@ open class PartySlot(
         private val genderIconFemale = cobblemonResource("textures/gui/pc/gender_icon_female.png")
         private val selectPointerResource = cobblemonResource("textures/gui/pc/pc_pointer.png")
         private val untradeableResource = cobblemonResource("textures/gui/trade/trade_slot_icon_locked.png")
+        private val tradePartySlotSelectedResource = cobblemonResource("textures/gui/trade/trade_party_slot_selected.png")
+        private val tradePartySlotSelectedOpposingResource = cobblemonResource("textures/gui/trade/trade_party_slot_selected_opposing.png")
     }
 
     override fun playDownSound(soundManager: SoundManager) {
@@ -60,6 +62,17 @@ open class PartySlot(
             )
         }
 
+        if (hasSelected()) {
+            blitk(
+                matrixStack = matrices,
+                texture = if (isOpposing) tradePartySlotSelectedOpposingResource else tradePartySlotSelectedResource,
+                x = x - 2,
+                y = y - 2,
+                width = 29,
+                height = 29
+            )
+        }
+
         if (pokemon != null) {
             // context.enableScissor(x - 2, y + 2, x + SIZE + 4, y + SIZE + 4)
             // Render Pokémon
@@ -118,7 +131,16 @@ open class PartySlot(
             }
 
             matrices.popPose()
-            if (hasSelected()) {
+            
+            val isViewed = if (isOpposing) {
+                parent.opposingOfferedPokemon?.uuid == pokemon.pokemonId
+            } else {
+                parent.offeredPokemon?.uuid == pokemon.pokemonId
+            }
+
+            if (isViewed && pokemon.tradeable) {
+                matrices.pushPose()
+                matrices.translate(0.0, 0.0, 200.0)
                 blitk(
                     matrixStack = matrices,
                     texture = selectPointerResource,
@@ -128,6 +150,7 @@ open class PartySlot(
                     height = 8,
                     scale = TradeGUI.SCALE
                 )
+                matrices.popPose()
             }
 
             // Held Item
@@ -145,8 +168,9 @@ open class PartySlot(
     }
 
     open fun hasSelected(): Boolean {
-        val offeredPokemon = if (isOpposing) parent.trade.oppositeOffer.get() else parent.trade.myOffer.get()
-        return pokemon?.pokemonId == offeredPokemon?.uuid && pokemon != null
+        if (pokemon == null) return false
+        val offeredPokemons = if (isOpposing) parent.trade.oppositeOffer.get() else parent.trade.myOffer.get()
+        return offeredPokemons.any { it.uuid == pokemon.pokemonId }
     }
 
     fun isHovered(mouseX: Int, mouseY: Int) = pokemon?.tradeable != false && mouseX.toFloat() in (x.toFloat()..(x.toFloat() + SIZE)) && mouseY.toFloat() in (y.toFloat()..(y.toFloat() + SIZE))

common/src/main/kotlin/com/cobblemon/mod/common/client/gui/trade/TradeGUI.kt

@@ -25,6 +25,7 @@ import com.cobblemon.mod.common.client.gui.summary.widgets.common.reformatNature
 import com.cobblemon.mod.common.client.render.drawScaledText
 import com.cobblemon.mod.common.client.render.drawScaledTextJustifiedRight
 import com.cobblemon.mod.common.client.trade.ClientTrade
+import com.cobblemon.mod.common.net.messages.client.trade.TradeStartedPacket
 import com.cobblemon.mod.common.net.messages.client.trade.TradeStartedPacket.TradeablePokemon
 import com.cobblemon.mod.common.net.messages.server.trade.*
 import com.cobblemon.mod.common.pokemon.Gender
@@ -98,15 +99,23 @@ class TradeGUI(
         private val tradeAnimationArrowsResource = cobblemonResource("textures/gui/trade/trade_animation_arrows.png")
     }
 
-    private var offeredPokemonModel: ModelWidget? = null
-    private var opposingOfferedPokemonModel: ModelWidget? = null
+    private var offeredPokemonModels: MutableList<ModelWidget> = mutableListOf()
+    private var opposingOfferedPokemonModels: MutableList<ModelWidget> = mutableListOf()
 
     private lateinit var offeredPokemonMarkings: MarkingsWidget
     private lateinit var opposingOfferedPokemonMarkings: MarkingsWidget
 
+    var selectedPartyIndices = mutableListOf<Int>()
+    var offeredPokemons: MutableList<Pokemon> = mutableListOf()
+    var opposingPokemons: MutableList<Pokemon> = mutableListOf()
+
+    // For backwards compatibility where single is referenced in rendering text info
     var offeredPokemon: Pokemon? = null
     var opposingOfferedPokemon: Pokemon? = null
 
+    var myGridMode = true
+    var opposingGridMode = true
+
     var ticksElapsed = 0
     var protectiveTicks = 0
     var selectPointerOffsetY = 0
@@ -125,30 +134,67 @@ class TradeGUI(
         }
 
         trade.completedEmitter.subscribe {
-            val (pokemonId1, pokemonId2) = it
-            val myTradedPokemon = party.find { it?.pokemonId == pokemonId1 }
-            val theirTradedPokemon = traderParty.find { it?.pokemonId == pokemonId2 }
-            if (myTradedPokemon == null || theirTradedPokemon == null) {
+            val (pokemonIds1, pokemonIds2) = it
+            val myTradedPokemons = pokemonIds1.mapNotNull { id -> party.find { it?.pokemonId == id } }
+            val theirTradedPokemons = pokemonIds2.mapNotNull { id -> traderParty.find { it?.pokemonId == id } }
+            if (myTradedPokemons.isEmpty() || theirTradedPokemons.isEmpty()) {
                 CobblemonNetwork.sendToServer(CancelTradePacket())
                 return@subscribe onClose()
             }
-            val tradedSlot = party.indexOf(myTradedPokemon)
-            val opposingTradedSlot = traderParty.indexOf(theirTradedPokemon)
-            party[tradedSlot] = theirTradedPokemon
-            traderParty[opposingTradedSlot] = myTradedPokemon
+
+            myTradedPokemons.forEach { pk ->
+                val idx = party.indexOf(pk)
+                if (idx != -1) party[idx] = null
+            }
+            theirTradedPokemons.forEach { pk ->
+                val idx = traderParty.indexOf(pk)
+                if (idx != -1) traderParty[idx] = null
+            }
+
+            val newSelectedIndices = mutableListOf<Int>()
+            theirTradedPokemons.forEach { pk ->
+                val emptyIdx = party.indexOf(null)
+                if (emptyIdx != -1) {
+                    party[emptyIdx] = pk
+                }
+            }
+            myTradedPokemons.forEach { pk ->
+                val emptyIdx = traderParty.indexOf(null)
+                if (emptyIdx != -1) traderParty[emptyIdx] = pk
+            }
+
+            val compactUI = { list: MutableList<TradeStartedPacket.TradeablePokemon?> ->
+                val nonNulls = list.filterNotNull()
+                list.clear()
+                list.addAll(nonNulls)
+                while (list.size < 6) list.add(null)
+            }
+            compactUI(party)
+            compactUI(traderParty)
+
+            theirTradedPokemons.forEach { pk ->
+                val idx = party.indexOf(pk)
+                if (idx != -1) newSelectedIndices.add(idx)
+            }
 
             trade.oppositeAcceptedMyOffer.set(false)
-            CobblemonNetwork.sendToServer(UpdateTradeOfferPacket(Pair(theirTradedPokemon.pokemonId, PartyPosition(tradedSlot))))
+            selectedPartyIndices.clear()
+            selectedPartyIndices.addAll(newSelectedIndices)
+
+            val newOffers = selectedPartyIndices.mapNotNull { idx ->
+                party[idx]?.let { it.pokemonId to PartyPosition(idx) }
+            }
+            CobblemonNetwork.sendToServer(UpdateTradeOfferPacket(newOffers))
 
             rebuildWidgets()
         }
 
-        trade.oppositeOffer.subscribe { newOffer: Pokemon? ->
-            setOfferedPokemon(pokemon = newOffer, isOpposing = true)
+        trade.oppositeOffer.subscribe { newOffer: List<Pokemon> ->
+            setOfferedPokemon(pokemonList = newOffer, isOpposing = true)
         }
 
-        trade.myOffer.subscribe { myOffer: Pokemon? ->
-            setOfferedPokemon(pokemon = myOffer)
+        trade.myOffer.subscribe { myOffer: List<Pokemon> ->
+            setOfferedPokemon(pokemonList = myOffer)
         }
 
         trade.oppositeAcceptedMyOffer.subscribe {
@@ -216,9 +262,16 @@ class TradeGUI(
                 pokemon = pokemon,
                 parent = this,
                 onPress = {
-                    if (!trade.acceptedOppositeOffer && !tradeProcessing) {
-                        val pk = if (offeredPokemon?.uuid == pokemon?.pokemonId) null else pokemon
-                        CobblemonNetwork.sendToServer(UpdateTradeOfferPacket(pk?.let { it.pokemonId to PartyPosition(partyIndex) }))
+                    if (!trade.acceptedOppositeOffer && !tradeProcessing && pokemon != null) {
+                        if (selectedPartyIndices.contains(partyIndex)) {
+                            selectedPartyIndices.remove(partyIndex)
+                        } else if (selectedPartyIndices.size < 6) {
+                            selectedPartyIndices.add(partyIndex)
+                        }
+                        val newOffers = selectedPartyIndices.mapNotNull { idx ->
+                            party[idx]?.let { it.pokemonId to PartyPosition(idx) }
+                        }
+                        CobblemonNetwork.sendToServer(UpdateTradeOfferPacket(newOffers))
                         playSound(CobblemonSounds.GUI_CLICK)
                     }
                 }
@@ -250,8 +303,8 @@ class TradeGUI(
             ).also { widget -> addRenderableWidget(widget) }
         }
 
-        setOfferedPokemon(pokemon = offeredPokemon, isOpposing = false)
-        setOfferedPokemon(pokemon = opposingOfferedPokemon, isOpposing = true)
+        setOfferedPokemon(pokemonList = offeredPokemons.toList(), isOpposing = false)
+        setOfferedPokemon(pokemonList = opposingPokemons.toList(), isOpposing = true)
 
         offeredPokemonMarkings = MarkingsWidget(x + 74.5, y + 21, offeredPokemon, false)
         opposingOfferedPokemonMarkings = MarkingsWidget(x + 177.5, y + 21, opposingOfferedPokemon, false)
@@ -284,7 +337,7 @@ class TradeGUI(
                 if (tradeAnimationProgress > REVERSE_ANIMATION_TICK)
                     (REVERSE_ANIMATION_TICK + TRADE_ANIMATION_FRAMES - tradeAnimationProgress)
                 else (tradeAnimationProgress - MODEL_SCALE_BUFFER_FRAMES)
-            ) * TRADE_ANIMATION_HEIGHT
+                ) * TRADE_ANIMATION_HEIGHT
             blitk(
                 matrixStack = matrices,
                 texture = tradeAnimationResource,
@@ -313,20 +366,56 @@ class TradeGUI(
         // Render Model Portraits
         var scale = PORTRAIT_SCALE
         var scaleOffsetY = PORTRAIT_MODEL_OFFSET_Y
+        var isShrinking = false
         if (tradeProcessing) {
             val scaleInterval = if (tradeAnimationProgress > REVERSE_ANIMATION_TICK) (MAX_TRADE_PROGRESS - tradeAnimationProgress) else tradeAnimationProgress
             scale = (PORTRAIT_SCALE - (scaleInterval * PORTRAIT_SCALE_MULTIPLIER)).coerceIn(0F, PORTRAIT_SCALE)
             scaleOffsetY = (45.0 - (45.0 / PORTRAIT_SCALE) * scale) + PORTRAIT_MODEL_OFFSET_Y
+            isShrinking = true
         }
+        val shrinkPercentage = if (isShrinking) 1.0F - (scale / PORTRAIT_SCALE) else 0.0F
+        val myCenterXDest = x + 70 + (PORTRAIT_SIZE / 2.0)
+        val myCenterYDest = y + 30 + (PORTRAIT_SIZE / 2.0)
+        val opCenterXDest = x + 145 + (PORTRAIT_SIZE / 2.0)
+        val opCenterYDest = y + 30 + (PORTRAIT_SIZE / 2.0)
+
         if (scale > 0F) {
             context.enableScissor(backgroundX, backgroundY, backgroundX + BASE_BACKGROUND_WIDTH, backgroundY +  BASE_BACKGROUND_HEIGHT)
-            offeredPokemonModel?.baseScale = scale
-            offeredPokemonModel?.offsetY = scaleOffsetY
-            offeredPokemonModel?.render(context, mouseX, mouseY, delta)
 
-            opposingOfferedPokemonModel?.baseScale = scale
-            opposingOfferedPokemonModel?.offsetY = scaleOffsetY
-            opposingOfferedPokemonModel?.render(context, mouseX, mouseY, delta)
+            offeredPokemonModels.forEachIndexed { i, model ->
+                val posAndScale = getModelPositionAndScale(i, offeredPokemons.size, x + 70, y + 30)
+                val originalScale = posAndScale.second
+                model.baseScale = if (isShrinking) (originalScale / PORTRAIT_SCALE) * scale else originalScale
+                model.offsetY = if (isShrinking) scaleOffsetY else PORTRAIT_MODEL_OFFSET_Y
+
+                val startCenterX = posAndScale.first.first + (PORTRAIT_SIZE / 2.0)
+                val startCenterY = posAndScale.first.second + (PORTRAIT_SIZE / 2.0)
+
+                context.pose().pushPose()
+                context.pose().translate((myCenterXDest - startCenterX) * shrinkPercentage, (myCenterYDest - startCenterY) * shrinkPercentage, 0.0)
+
+                model.render(context, mouseX, mouseY, delta)
+
+                context.pose().popPose()
+            }
+
+            opposingOfferedPokemonModels.forEachIndexed { i, model ->
+                val posAndScale = getModelPositionAndScale(i, opposingPokemons.size, x + 145, y + 30)
+                val originalScale = posAndScale.second
+                model.baseScale = if (isShrinking) (originalScale / PORTRAIT_SCALE) * scale else originalScale
+                model.offsetY = if (isShrinking) scaleOffsetY else PORTRAIT_MODEL_OFFSET_Y
+
+                val startCenterX = posAndScale.first.first + (PORTRAIT_SIZE / 2.0)
+                val startCenterY = posAndScale.first.second + (PORTRAIT_SIZE / 2.0)
+
+                context.pose().pushPose()
+                context.pose().translate((opCenterXDest - startCenterX) * shrinkPercentage, (opCenterYDest - startCenterY) * shrinkPercentage, 0.0)
+
+                model.render(context, mouseX, mouseY, delta)
+
+                context.pose().popPose()
+            }
+
             context.disableScissor()
         }
 
@@ -341,8 +430,46 @@ class TradeGUI(
 
         renderInfoLabels(context, x, y)
 
-        renderPokemonInfo(offeredPokemon, false, context, x, y, mouseX, mouseY)
-        renderPokemonInfo(opposingOfferedPokemon, true, context, x, y, mouseX, mouseY)
+        children().filterIsInstance<PartySlot>().forEach { slot ->
+            if (slot.isHovered(mouseX, mouseY)) {
+                val hoveredId = slot.pokemon?.pokemonId
+                if (slot.isOpposing && slot.hasSelected()) {
+                    opposingPokemons.find { it.uuid == hoveredId }?.let { opposingOfferedPokemon = it }
+                } else if (!slot.isOpposing) {
+                    val matchingModel = offeredPokemons.find { it.uuid == hoveredId }
+                    if (matchingModel != null) {
+                        offeredPokemon = matchingModel
+                    } else {
+                        val realPokemon = com.cobblemon.mod.common.client.CobblemonClient.storage.party.find { it?.uuid == hoveredId }
+                        if (realPokemon != null) {
+                            offeredPokemon = realPokemon
+                        }
+                    }
+                }
+            }
+        }
+
+        val currentOffered = offeredPokemon
+        if (currentOffered != null) {
+            renderPokemonInfo(currentOffered, false, context, x, y, mouseX, mouseY)
+            if (::offeredPokemonMarkings.isInitialized) {
+                offeredPokemonMarkings.visible = true
+                if (offeredPokemonMarkings.pokemon != currentOffered) offeredPokemonMarkings.setActivePokemon(currentOffered)
+            }
+        } else {
+            if (::offeredPokemonMarkings.isInitialized) offeredPokemonMarkings.visible = false
+        }
+
+        val currentOpposing = opposingOfferedPokemon
+        if (currentOpposing != null) {
+            renderPokemonInfo(currentOpposing, true, context, x, y, mouseX, mouseY)
+            if (::opposingOfferedPokemonMarkings.isInitialized) {
+                opposingOfferedPokemonMarkings.visible = true
+                if (opposingOfferedPokemonMarkings.pokemon != currentOpposing) opposingOfferedPokemonMarkings.setActivePokemon(currentOpposing)
+            }
+        } else {
+            if (::opposingOfferedPokemonMarkings.isInitialized) opposingOfferedPokemonMarkings.visible = false
+        }
 
         if (trade.acceptedOppositeOffer) {
             blitk(
@@ -431,19 +558,25 @@ class TradeGUI(
 
         super.render(context, mouseX, mouseY, delta)
 
-        // Item Tooltip
-        if (offeredPokemon != null && !offeredPokemon!!.heldItemNoCopy().isEmpty) {
-            val itemX = x + 50
-            val itemY = y + 125
-            val itemHovered = mouseX.toFloat() in (itemX.toFloat()..(itemX.toFloat() + 16)) && mouseY.toFloat() in (itemY.toFloat()..(itemY.toFloat() + 16))
-            if (itemHovered) context.renderTooltip(Minecraft.getInstance().font, offeredPokemon!!.heldItemNoCopy(), mouseX, mouseY)
+        val ttOffered = offeredPokemon
+        if (ttOffered != null) {
+            // Item Tooltip
+            if (!ttOffered.heldItemNoCopy().isEmpty) {
+                val itemX = x + 50
+                val itemY = y + 125
+                val itemHovered = mouseX.toFloat() in (itemX.toFloat()..(itemX.toFloat() + 16)) && mouseY.toFloat() in (itemY.toFloat()..(itemY.toFloat() + 16))
+                if (itemHovered) context.renderTooltip(Minecraft.getInstance().font, ttOffered.heldItemNoCopy(), mouseX, mouseY)
+            }
         }
 
-        if (opposingOfferedPokemon != null && !opposingOfferedPokemon!!.heldItemNoCopy().isEmpty) {
-            val itemX = x + 227
-            val itemY = y + 125
-            val itemHovered = mouseX.toFloat() in (itemX.toFloat()..(itemX.toFloat() + 16)) && mouseY.toFloat() in (itemY.toFloat()..(itemY.toFloat() + 16))
-            if (itemHovered) context.renderTooltip(Minecraft.getInstance().font, opposingOfferedPokemon!!.heldItemNoCopy(), mouseX, mouseY)
+        val ttOpposing = opposingOfferedPokemon
+        if (ttOpposing != null) {
+            if (!ttOpposing.heldItemNoCopy().isEmpty) {
+                val itemX = x + 227
+                val itemY = y + 125
+                val itemHovered = mouseX.toFloat() in (itemX.toFloat()..(itemX.toFloat() + 16)) && mouseY.toFloat() in (itemY.toFloat()..(itemY.toFloat() + 16))
+                if (itemHovered) context.renderTooltip(Minecraft.getInstance().font, ttOpposing.heldItemNoCopy(), mouseX, mouseY)
+            }
         }
     }
 
@@ -480,11 +613,13 @@ class TradeGUI(
             }
 
             if (tradeAnimationProgress == (MAX_TRADE_PROGRESS + CRY_BUFFER)) {
-                if (offeredPokemonModel !== null && opposingOfferedPokemonModel !== null) {
-                    offeredPokemonModel!!.state.activeAnimations.clear()
-                    offeredPokemonModel!!.state.addFirstAnimation(setOf("cry"))
-                    opposingOfferedPokemonModel!!.state.activeAnimations.clear()
-                    opposingOfferedPokemonModel!!.state.addFirstAnimation(setOf("cry"))
+                offeredPokemonModels.forEach {
+                    it.state.activeAnimations.clear()
+                    it.state.addFirstAnimation(setOf("cry"))
+                }
+                opposingOfferedPokemonModels.forEach {
+                    it.state.activeAnimations.clear()
+                    it.state.addFirstAnimation(setOf("cry"))
                 }
             }
 
@@ -515,41 +650,140 @@ class TradeGUI(
 
     override fun renderMenuBackground(context: GuiGraphics) {}
 
-    private fun setOfferedPokemon(pokemon: Pokemon?, isOpposing: Boolean = false) {
+    private fun setOfferedPokemon(pokemonList: List<Pokemon>, isOpposing: Boolean = false) {
         protectiveTicks = 20
+        if (isOpposing) {
+            val wasEmpty = opposingPokemons.isEmpty()
+            val currentViewedUuid = if (opposingGridMode) null else opposingOfferedPokemon?.uuid
+            opposingPokemons.clear()
+            opposingPokemons.addAll(pokemonList)
+
+            val matchingPokemon = opposingPokemons.find { it.uuid == currentViewedUuid }
+
+            if (matchingPokemon != null) {
+                opposingOfferedPokemon = matchingPokemon
+                if (::opposingOfferedPokemonMarkings.isInitialized) opposingOfferedPokemonMarkings.setActivePokemon(opposingOfferedPokemon)
+            } else {
+                opposingOfferedPokemon = opposingPokemons.lastOrNull()
+                if (::opposingOfferedPokemonMarkings.isInitialized) opposingOfferedPokemonMarkings.setActivePokemon(opposingOfferedPokemon)
+                if (wasEmpty && opposingOfferedPokemon != null) {
+                    opposingGridMode = false
+                } else if (!opposingGridMode) {
+                    opposingGridMode = true
+                }
+            }
+            trade.acceptedOppositeOffer = false
+        } else {
+            val wasEmpty = offeredPokemons.isEmpty()
+            val currentViewedUuid = if (myGridMode) null else offeredPokemon?.uuid
+            offeredPokemons.clear()
+            offeredPokemons.addAll(pokemonList)
+
+            val matchingPokemon = offeredPokemons.find { it.uuid == currentViewedUuid }
+
+            if (matchingPokemon != null) {
+                offeredPokemon = matchingPokemon
+                if (::offeredPokemonMarkings.isInitialized) offeredPokemonMarkings.setActivePokemon(offeredPokemon)
+            } else {
+                offeredPokemon = offeredPokemons.lastOrNull()
+                if (::offeredPokemonMarkings.isInitialized) offeredPokemonMarkings.setActivePokemon(offeredPokemon)
+                if (wasEmpty && offeredPokemon != null) {
+                    myGridMode = false
+                } else if (!myGridMode) {
+                    myGridMode = true
+                }
+            }
+        }
+        rebuildSelectedModels(isOpposing)
+    }
+
+    private fun rebuildSelectedModels(isOpposing: Boolean) {
         val x = (width - BASE_WIDTH) / 2
         val y = (height - BASE_HEIGHT) / 2
 
         if (isOpposing) {
-            opposingOfferedPokemon = pokemon
-            opposingOfferedPokemonModel = if (pokemon != null) ModelWidget(
-                pX = x + 145,
-                pY = y + 30,
-                pWidth = PORTRAIT_SIZE,
-                pHeight = PORTRAIT_SIZE,
-                pokemon = pokemon.asRenderablePokemon(),
-                baseScale = PORTRAIT_SCALE,
-                rotationY = 35F,
-                offsetY = PORTRAIT_MODEL_OFFSET_Y
-            ) else null
-            if (::opposingOfferedPokemonMarkings.isInitialized) opposingOfferedPokemonMarkings.setActivePokemon(opposingOfferedPokemon)
-            trade.acceptedOppositeOffer = false
+            opposingOfferedPokemonModels.clear()
+            val total = opposingPokemons.size
+            opposingPokemons.forEachIndexed { i, pk ->
+                val (pos, currentScale) = getModelPositionAndScale(i, total, x + 145, y + 30)
+                opposingOfferedPokemonModels.add(ModelWidget(
+                    pX = pos.first, pY = pos.second,
+                    pWidth = PORTRAIT_SIZE, pHeight = PORTRAIT_SIZE,
+                    pokemon = pk.asRenderablePokemon(),
+                    baseScale = currentScale,
+                    rotationY = 35F,
+                    offsetY = PORTRAIT_MODEL_OFFSET_Y
+                ))
+            }
         } else {
-            offeredPokemon = pokemon
-            offeredPokemonModel = if (pokemon != null) ModelWidget(
-                pX = x + 70,
-                pY = y + 30,
-                pWidth = PORTRAIT_SIZE,
-                pHeight = PORTRAIT_SIZE,
-                pokemon = pokemon.asRenderablePokemon(),
-                baseScale = PORTRAIT_SCALE,
-                rotationY = 325F,
-                offsetY = PORTRAIT_MODEL_OFFSET_Y
-            ) else null
-            if (::offeredPokemonMarkings.isInitialized) offeredPokemonMarkings.setActivePokemon(offeredPokemon)
+            offeredPokemonModels.clear()
+            val total = offeredPokemons.size
+            offeredPokemons.forEachIndexed { i, pk ->
+                val (pos, currentScale) = getModelPositionAndScale(i, total, x + 70, y + 30)
+                offeredPokemonModels.add(ModelWidget(
+                    pX = pos.first, pY = pos.second,
+                    pWidth = PORTRAIT_SIZE, pHeight = PORTRAIT_SIZE,
+                    pokemon = pk.asRenderablePokemon(),
+                    baseScale = currentScale,
+                    rotationY = 325F,
+                    offsetY = PORTRAIT_MODEL_OFFSET_Y
+                ))
+            }
         }
     }
 
+    private fun getModelPositionAndScale(index: Int, total: Int, baseX: Int, baseY: Int): Pair<Pair<Int, Int>, Float> {
+        val scale = when (total) {
+            1 -> PORTRAIT_SCALE
+            2 -> PORTRAIT_SCALE * 0.75f
+            3 -> PORTRAIT_SCALE * 0.65f
+            4 -> PORTRAIT_SCALE * 0.55f
+            else -> PORTRAIT_SCALE * 0.5f
+        }
+
+        if (total <= 1) {
+            return Pair(Pair(baseX, baseY), scale)
+        }
+
+        val rowLength1 = when (total) {
+            2, 3, 4 -> 2
+            else -> 3
+        }
+        val rowLength2 = total - rowLength1
+
+        val isBottomRow = index >= rowLength1
+        val row = if (isBottomRow) 1 else 0
+        val col = if (isBottomRow) index - rowLength1 else index
+        val currentRowLength = if (isBottomRow) rowLength2 else rowLength1
+
+        val colSpacing = when (total) {
+            2 -> 35
+            3 -> 30
+            4 -> 25
+            else -> 23
+        }
+        val rowSpacing = when (total) {
+            2, 3 -> 30
+            4 -> 28
+            else -> 25
+        }
+
+        val totalWidth = (currentRowLength - 1) * colSpacing
+        val startX = baseX - (totalWidth / 2)
+
+        val totalHeight = if (rowLength2 > 0) rowSpacing else 0
+        var startY = baseY + 12 - (totalHeight / 2)
+
+        if (total >= 4) {
+            startY += 8
+        }
+
+        val posX = startX + (col * colSpacing)
+        val posY = startY + (row * rowSpacing)
+
+        return Pair(Pair(posX, posY), scale)
+    }
+
     private fun playSound(soundEvent: SoundEvent): SoundInstance {
         val soundInstance = SimpleSoundInstance.forUI(soundEvent, 1.0F)
         Minecraft.getInstance().soundManager.play(soundInstance)
@@ -557,10 +791,10 @@ class TradeGUI(
     }
 
     private fun cancelTradeSound() {
-        if (tradeSoundInstance !== null) Minecraft.getInstance().soundManager.stop(tradeSoundInstance)
+        if (tradeSoundInstance != null) Minecraft.getInstance().soundManager.stop(tradeSoundInstance!!)
     }
 
-    private fun renderPokemonInfo(pokemon: Pokemon?, isOpposing: Boolean, context: GuiGraphics, x: Int, y: Int, mouseX: Int, mouseY: Int) {
+    public fun renderPokemonInfo(pokemon: Pokemon?, isOpposing: Boolean, context: GuiGraphics, x: Int, y: Int, mouseX: Int, mouseY: Int) {
         if (pokemon != null) {
             val matrices = context.pose()
             // Level
@@ -1047,4 +1281,4 @@ class TradeGUI(
             scale = SCALE
         )
     }
-}
+}

common/src/main/kotlin/com/cobblemon/mod/common/client/net/trade/TradeAcceptanceChangedHandler.kt

@@ -15,9 +15,9 @@ import net.minecraft.client.Minecraft
 
 object TradeAcceptanceChangedHandler : ClientNetworkPacketHandler<TradeAcceptanceChangedPacket> {
     override fun handle(packet: TradeAcceptanceChangedPacket, client: Minecraft) {
-        if (CobblemonClient.trade?.myOffer?.get()?.uuid == packet.pokemonId) {
+        if (CobblemonClient.trade?.myOffer?.get()?.any { it.uuid == packet.pokemonId } == true) {
             CobblemonClient.trade!!.oppositeAcceptedMyOffer.set(packet.accepted)
-        } else if (CobblemonClient.trade?.oppositeOffer?.get()?.uuid == packet.pokemonId) {
+        } else if (CobblemonClient.trade?.oppositeOffer?.get()?.any { it.uuid == packet.pokemonId } == true) {
             CobblemonClient.trade!!.acceptedOppositeOffer = packet.accepted
         }
     }

common/src/main/kotlin/com/cobblemon/mod/common/client/net/trade/TradeCompletedHandler.kt

@@ -16,6 +16,6 @@ import net.minecraft.client.Minecraft
 object TradeCompletedHandler : ClientNetworkPacketHandler<TradeCompletedPacket> {
     override fun handle(packet: TradeCompletedPacket, client: Minecraft) {
         val trade = CobblemonClient.trade ?: return
-        trade.completedEmitter.emit(packet.pokemonId1 to packet.pokemonId2)
+        trade.completedEmitter.emit(packet.pokemonIds1 to packet.pokemonIds2)
     }
 }

common/src/main/kotlin/com/cobblemon/mod/common/client/net/trade/TradeStartedHandler.kt

@@ -20,7 +20,7 @@ import net.minecraft.client.Minecraft
 
 object TradeStartedHandler : ClientNetworkPacketHandler<TradeStartedPacket> {
     override fun handle(packet: TradeStartedPacket, client: Minecraft) {
-        Cobblemon.LOGGER.error("handle trade start from: " + packet.traderId)
+        Cobblemon.LOGGER.info("Trade started with {}", packet.traderId)
         val trade = ClientTrade()
         CobblemonClient.trade = trade
         Minecraft.getInstance().setScreen(

common/src/main/kotlin/com/cobblemon/mod/common/client/net/trade/TradeUpdatedHandler.kt

@@ -18,9 +18,9 @@ object TradeUpdatedHandler : ClientNetworkPacketHandler<TradeUpdatedPacket> {
         val trade = CobblemonClient.trade ?: return
 
         if (packet.playerId == Minecraft.getInstance().player?.uuid) {
-            trade.myOffer.set(packet.pokemon)
+            trade.myOffer.set(packet.pokemons)
         } else {
-            trade.oppositeOffer.set(packet.pokemon)
+            trade.oppositeOffer.set(packet.pokemons)
         }
         trade.oppositeAcceptedMyOffer.set(false)
         trade.acceptedOppositeOffer = false

common/src/main/kotlin/com/cobblemon/mod/common/client/trade/ClientTrade.kt

@@ -14,12 +14,12 @@ import com.cobblemon.mod.common.pokemon.Pokemon
 import java.util.UUID
 
 class ClientTrade {
-    var myOffer = SettableObservable<Pokemon?>(null)
-    var oppositeOffer = SettableObservable<Pokemon?>(null)
+    var myOffer = SettableObservable<List<Pokemon>>(emptyList())
+    var oppositeOffer = SettableObservable<List<Pokemon>>(emptyList())
     var tradeProcessing = SettableObservable(Pair(false, false))
     var oppositeAcceptedMyOffer = SettableObservable(false)
     var acceptedOppositeOffer = false
 
-    var completedEmitter = SimpleObservable<Pair<UUID, UUID>>()
+    var completedEmitter = SimpleObservable<Pair<List<UUID>, List<UUID>>>()
     var cancelEmitter = SimpleObservable<Unit>()
 }

common/src/main/kotlin/com/cobblemon/mod/common/events/AdvancementHandler.kt

@@ -31,6 +31,7 @@ import net.minecraft.world.item.BlockItem
 import com.cobblemon.mod.common.platform.events.ServerPlayerEvent
 import com.cobblemon.mod.common.api.storage.player.PlayerInstancedDataStoreTypes
 import com.cobblemon.mod.common.item.GemItem
+import com.cobblemon.mod.common.pokemon.Pokemon
 import com.cobblemon.mod.common.platform.events.PlatformEvents
 import com.cobblemon.mod.common.util.effectiveName
 import com.cobblemon.mod.common.util.getPlayer
@@ -164,26 +165,21 @@ object AdvancementHandler : EventHandler {
     }
 
     fun onTradeCompleted(event : TradeEvent.Post) {
-        val player1 = event.tradeParticipant1Pokemon.getOwnerPlayer()
-        val player2 = event.tradeParticipant2Pokemon.getOwnerPlayer()
-        if (player1 != null) {
-            CobblemonCriteria.TRADE_POKEMON.trigger(player1, TradePokemonContext(event.tradeParticipant1Pokemon, event.tradeParticipant2Pokemon))
-            val playerData = Cobblemon.playerDataManager.getGenericData(player1)
-            val advancementData = playerData.advancementData
-            advancementData.updateTotalTradedCount()
-            advancementData.updateAspectsCollected(player1, event.tradeParticipant2Pokemon)
-            CobblemonCriteria.COLLECT_ASPECT.trigger(player1, advancementData.aspectsCollected)
-            Cobblemon.playerDataManager.saveSingle(playerData, PlayerInstancedDataStoreTypes.GENERAL)
-        }
-        if (player2 != null) {
-            CobblemonCriteria.TRADE_POKEMON.trigger(player2, TradePokemonContext(event.tradeParticipant2Pokemon, event.tradeParticipant1Pokemon))
-            val playerData = Cobblemon.playerDataManager.getGenericData(player2)
-            val advancementData = playerData.advancementData
-            advancementData.updateTotalTradedCount()
-            advancementData.updateAspectsCollected(player2, event.tradeParticipant1Pokemon)
-            CobblemonCriteria.COLLECT_ASPECT.trigger(player2, advancementData.aspectsCollected)
-            Cobblemon.playerDataManager.saveSingle(playerData, PlayerInstancedDataStoreTypes.GENERAL)
+        onTradeCompleted(event.tradeParticipant1Pokemon, event.tradeParticipant2Pokemon)
+        onTradeCompleted(event.tradeParticipant2Pokemon, event.tradeParticipant1Pokemon)
+    }
+
+    private fun onTradeCompleted(received: List<Pokemon>, traded: List<Pokemon>) {
+        val player = received.firstOrNull()?.getOwnerPlayer() ?: return
+        received.forEach { receivedPokemon ->
+            traded.forEach { tradedPokemon -> CobblemonCriteria.TRADE_POKEMON.trigger(player, TradePokemonContext(tradedPokemon, receivedPokemon)) }
         }
+        val playerData = Cobblemon.playerDataManager.getGenericData(player)
+        val advancementData = playerData.advancementData
+        advancementData.updateTotalTradedCount()
+        received.forEach { advancementData.updateAspectsCollected(player, it) }
+        CobblemonCriteria.COLLECT_ASPECT.trigger(player, advancementData.aspectsCollected)
+        Cobblemon.playerDataManager.saveSingle(playerData, PlayerInstancedDataStoreTypes.GENERAL)
     }
 
     /**

common/src/main/kotlin/com/cobblemon/mod/common/events/StatHandler.kt

@@ -110,8 +110,8 @@ object StatHandler : EventHandler {
     }
 
     fun onTradeCompleted(event : TradeEvent.Post) {
-        event.tradeParticipant1Pokemon.getOwnerPlayer()?.awardStat(getStat(Cobblemon.statistics.TRADED))
-        event.tradeParticipant2Pokemon.getOwnerPlayer()?.awardStat(getStat(Cobblemon.statistics.TRADED))
+        event.tradeParticipant1Pokemon.firstOrNull()?.getOwnerPlayer()?.awardStat(getStat(Cobblemon.statistics.TRADED))
+        event.tradeParticipant2Pokemon.firstOrNull()?.getOwnerPlayer()?.awardStat(getStat(Cobblemon.statistics.TRADED))
     }
 
     fun onFossilRevived(event : FossilRevivedEvent) {

common/src/main/kotlin/com/cobblemon/mod/common/net/messages/client/trade/TradeCompletedPacket.kt

@@ -23,16 +23,19 @@ import java.util.UUID
  * @author Hiroku
  * @since March 5th, 2023
  */
-class TradeCompletedPacket(val pokemonId1: UUID, val pokemonId2: UUID) : NetworkPacket<TradeCompletedPacket> {
+class TradeCompletedPacket(val pokemonIds1: List<UUID>, val pokemonIds2: List<UUID>) : NetworkPacket<TradeCompletedPacket> {
     companion object {
         val ID = cobblemonResource("trade_completed")
-        fun decode(buffer: RegistryFriendlyByteBuf) = TradeCompletedPacket(buffer.readUUID(), buffer.readUUID())
+        fun decode(buffer: RegistryFriendlyByteBuf) = TradeCompletedPacket(
+            buffer.readList { it.readUUID() },
+            buffer.readList { it.readUUID() }
+        )
     }
 
     override val id = ID
 
     override fun encode(buffer: RegistryFriendlyByteBuf) {
-        buffer.writeUUID(pokemonId1)
-        buffer.writeUUID(pokemonId2)
+        buffer.writeCollection(pokemonIds1) { buf, id -> buf.writeUUID(id) }
+        buffer.writeCollection(pokemonIds2) { buf, id -> buf.writeUUID(id) }
     }
 }

common/src/main/kotlin/com/cobblemon/mod/common/net/messages/client/trade/TradeUpdatedPacket.kt

@@ -12,10 +12,6 @@ import com.cobblemon.mod.common.api.net.NetworkPacket
 import com.cobblemon.mod.common.api.net.UnsplittablePacket
 import com.cobblemon.mod.common.pokemon.Pokemon
 import com.cobblemon.mod.common.util.cobblemonResource
-import com.cobblemon.mod.common.util.readNullable
-import com.cobblemon.mod.common.util.readUUID
-import com.cobblemon.mod.common.util.writeNullable
-import com.cobblemon.mod.common.util.writeUUID
 import net.minecraft.network.RegistryFriendlyByteBuf
 import java.util.UUID
 
@@ -27,15 +23,18 @@ import java.util.UUID
  * @author Hiroku
  * @since March 5th, 2023
  */
-class TradeUpdatedPacket(val playerId: UUID, val pokemon: Pokemon?) : NetworkPacket<TradeUpdatedPacket>, UnsplittablePacket {
+class TradeUpdatedPacket(val playerId: UUID, val pokemons: List<Pokemon>) : NetworkPacket<TradeUpdatedPacket>, UnsplittablePacket {
     companion object {
         val ID = cobblemonResource("trade_updated")
-        fun decode(buffer: RegistryFriendlyByteBuf) = TradeUpdatedPacket(buffer.readUUID(), buffer.readNullable { Pokemon.S2C_CODEC.decode(buffer) })
+        fun decode(buffer: RegistryFriendlyByteBuf) = TradeUpdatedPacket(
+            buffer.readUUID(),
+            buffer.readList { Pokemon.S2C_CODEC.decode(it as RegistryFriendlyByteBuf) }
+        )
     }
 
     override val id = ID
     override fun encode(buffer: RegistryFriendlyByteBuf) {
         buffer.writeUUID(playerId)
-        buffer.writeNullable(pokemon) { _, pokemon -> Pokemon.S2C_CODEC.encode(buffer, pokemon) }
+        buffer.writeCollection(pokemons) { buf, pokemon -> Pokemon.S2C_CODEC.encode(buf as RegistryFriendlyByteBuf, pokemon) }
     }
 }

common/src/main/kotlin/com/cobblemon/mod/common/net/messages/server/trade/UpdateTradeOfferPacket.kt

@@ -11,26 +11,30 @@ package com.cobblemon.mod.common.net.messages.server.trade
 import com.cobblemon.mod.common.api.net.NetworkPacket
 import com.cobblemon.mod.common.api.storage.party.PartyPosition
 import com.cobblemon.mod.common.util.cobblemonResource
+import com.cobblemon.mod.common.util.readList
 import com.cobblemon.mod.common.util.readNullable
 import com.cobblemon.mod.common.util.readPartyPosition
 import com.cobblemon.mod.common.util.readUUID
+import com.cobblemon.mod.common.util.writeCollection
 import com.cobblemon.mod.common.util.writeNullable
 import com.cobblemon.mod.common.util.writePartyPosition
 import com.cobblemon.mod.common.util.writeUUID
 import net.minecraft.network.RegistryFriendlyByteBuf
 import java.util.UUID
 
-class UpdateTradeOfferPacket(val newOffer: Pair<UUID, PartyPosition>?): NetworkPacket<UpdateTradeOfferPacket> {
+class UpdateTradeOfferPacket(val newOffers: List<Pair<UUID, PartyPosition>>): NetworkPacket<UpdateTradeOfferPacket> {
     companion object {
         val ID = cobblemonResource("update_trade_offer")
-        fun decode(buffer: RegistryFriendlyByteBuf) = UpdateTradeOfferPacket(buffer.readNullable { buffer.readUUID() to buffer.readPartyPosition() })
+        fun decode(buffer: RegistryFriendlyByteBuf) = UpdateTradeOfferPacket(
+            buffer.readList { it.readUUID() to it.readPartyPosition() }
+        )
     }
 
     override val id = ID
     override fun encode(buffer: RegistryFriendlyByteBuf) {
-        buffer.writeNullable(newOffer) { buffer, (pokemonId, partyPosition) ->
-            buffer.writeUUID(pokemonId)
-            buffer.writePartyPosition(partyPosition)
+        buffer.writeCollection(newOffers) { buf, (pokemonId, partyPosition) ->
+            buf.writeUUID(pokemonId)
+            buf.writePartyPosition(partyPosition)
         }
     }
 }

common/src/main/kotlin/com/cobblemon/mod/common/net/serverhandling/trade/ChangeTradeAcceptanceHandler.kt

@@ -20,7 +20,7 @@ object ChangeTradeAcceptanceHandler : ServerNetworkPacketHandler<ChangeTradeAcce
     override fun handle(packet: ChangeTradeAcceptancePacket, server: MinecraftServer, player: ServerPlayer) {
         val trade = TradeManager.getActiveTrade(player.uuid) ?: return player.sendPacket(TradeCancelledPacket())
         val tradeParticipant = trade.getTradeParticipant(player.uuid)
-        if (trade.getOpposingOffer(tradeParticipant).pokemon?.uuid == packet.pokemonOfferId) {
+        if (trade.getOpposingOffer(tradeParticipant).pokemon.any { it.uuid == packet.pokemonOfferId }) {
             trade.updateAcceptance(tradeParticipant, packet.newAcceptance)
         }
     }

common/src/main/kotlin/com/cobblemon/mod/common/net/serverhandling/trade/PerformTradeHandler.kt

@@ -20,7 +20,7 @@ object PerformTradeHandler : ServerNetworkPacketHandler<PerformTradePacket> {
     override fun handle(packet: PerformTradePacket, server: MinecraftServer, player: ServerPlayer) {
         val trade = TradeManager.getActiveTrade(player.uuid) ?: return player.sendPacket(TradeCancelledPacket())
         val tradeParticipant = trade.getTradeParticipant(player.uuid)
-        if (trade.getOpposingOffer(tradeParticipant).pokemon?.uuid == packet.pokemonOfferId) {
+        if (trade.getOpposingOffer(tradeParticipant).pokemon.any { it.uuid == packet.pokemonOfferId }) {
             trade.performTrade(tradeParticipant)
         }
     }

common/src/main/kotlin/com/cobblemon/mod/common/net/serverhandling/trade/UpdateTradeOfferHandler.kt

@@ -12,6 +12,7 @@ import com.cobblemon.mod.common.CobblemonNetwork.sendPacket
 import com.cobblemon.mod.common.api.net.ServerNetworkPacketHandler
 import com.cobblemon.mod.common.net.messages.server.trade.CancelTradePacket
 import com.cobblemon.mod.common.net.messages.server.trade.UpdateTradeOfferPacket
+import com.cobblemon.mod.common.pokemon.Pokemon
 import com.cobblemon.mod.common.trade.TradeManager
 import com.cobblemon.mod.common.util.party
 import net.minecraft.server.MinecraftServer
@@ -21,20 +22,16 @@ object UpdateTradeOfferHandler : ServerNetworkPacketHandler<UpdateTradeOfferPack
     override fun handle(packet: UpdateTradeOfferPacket, server: MinecraftServer, player: ServerPlayer) {
         val trade = TradeManager.getActiveTrade(player.uuid) ?: return player.sendPacket(CancelTradePacket())
         val tradeParticipant = trade.getTradeParticipant(player.uuid)
-        val newOffer = packet.newOffer
-        if (newOffer == null) {
-            trade.updateOffer(tradeParticipant, null)
-        } else {
-            val (pokemonId, partyPosition) = newOffer
-            val party = player.party()
+        val newOffers = packet.newOffers
+
+        val validPokemons = mutableListOf<Pokemon>()
+        val party = player.party()
+        for ((pokemonId, partyPosition) in newOffers) {
             val pokemon = party[partyPosition]
-            if (pokemon == null || pokemon.uuid != pokemonId) {
-                return
-            } else if (!pokemon.tradeable) {
-                return
-            } else {
-                trade.updateOffer(tradeParticipant, pokemon)
+            if (pokemon != null && pokemon.uuid == pokemonId && pokemon.tradeable) {
+                validPokemons.add(pokemon)
             }
         }
+        trade.updateOffer(tradeParticipant, validPokemons)
     }
 }

common/src/main/kotlin/com/cobblemon/mod/common/trade/ActiveTrade.kt

@@ -19,7 +19,7 @@ class ActiveTrade(val player1: TradeParticipant, val player2: TradeParticipant)
     fun getOffer(tradeParticipant: TradeParticipant) = if (tradeParticipant == player1) player1Offer else player2Offer
     fun getOpposingOffer(tradeParticipant: TradeParticipant) = if (tradeParticipant == player1) player2Offer else player1Offer
 
-    fun updateOffer(tradeParticipant: TradeParticipant, pokemon: Pokemon?) {
+    fun updateOffer(tradeParticipant: TradeParticipant, pokemon: List<Pokemon>) {
         getOffer(tradeParticipant).updateOffer(pokemon)
         getOffer(getOppositePlayer(tradeParticipant)).accepted = false
         player1.updateOffer(this, tradeParticipant, pokemon)
@@ -30,8 +30,9 @@ class ActiveTrade(val player1: TradeParticipant, val player2: TradeParticipant)
         val offer = getOpposingOffer(tradeParticipant)
         if (offer.accepted != acceptance) {
             offer.accepted = acceptance
-            getOppositePlayer(tradeParticipant).changeTradeAcceptance(this, offer.pokemon!!.uuid, acceptance)
-            tradeParticipant.changeTradeAcceptance(this, offer.pokemon!!.uuid, acceptance)
+            val firstId = offer.pokemon.firstOrNull()?.uuid ?: java.util.UUID.randomUUID()
+            getOppositePlayer(tradeParticipant).changeTradeAcceptance(this, firstId, acceptance)
+            tradeParticipant.changeTradeAcceptance(this, firstId, acceptance)
         }
 
         if (offer.accepted && getOffer(tradeParticipant).accepted) {
@@ -51,8 +52,8 @@ class ActiveTrade(val player1: TradeParticipant, val player2: TradeParticipant)
                 activeTrade = this,
                 player1 = player1,
                 player2 = player2,
-                pokemon1 = player1Offer.pokemon!!,
-                pokemon2 = player2Offer.pokemon!!
+                pokemon1 = player1Offer.pokemon,
+                pokemon2 = player2Offer.pokemon
             )
         }
     }
@@ -64,12 +65,14 @@ class ActiveTrade(val player1: TradeParticipant, val player2: TradeParticipant)
     }
 
     fun completeTrade() {
-        player1.completeTrade(this, player1Offer.pokemon!!.uuid, player2Offer.pokemon!!.uuid)
-        player2.completeTrade(this, player2Offer.pokemon!!.uuid, player1Offer.pokemon!!.uuid)
+        val uuids1 = player1Offer.pokemon.map { it.uuid }
+        val uuids2 = player2Offer.pokemon.map { it.uuid }
+        player1.completeTrade(this, uuids1, uuids2)
+        player2.completeTrade(this, uuids2, uuids1)
 
-        player1Offer.pokemon = null
+        player1Offer.pokemon = emptyList()
         player1Offer.accepted = false
-        player2Offer.pokemon = null
+        player2Offer.pokemon = emptyList()
         player2Offer.accepted = false
     }
 }

common/src/main/kotlin/com/cobblemon/mod/common/trade/TradeManager.kt

@@ -14,6 +14,7 @@ import com.cobblemon.mod.common.api.events.CobblemonEvents
 import com.cobblemon.mod.common.api.events.pokemon.TradeEvent
 import com.cobblemon.mod.common.api.interaction.ServerPlayerActionRequest
 import com.cobblemon.mod.common.api.net.NetworkPacket
+import com.cobblemon.mod.common.api.storage.party.PartyStore
 import com.cobblemon.mod.common.api.text.aqua
 import com.cobblemon.mod.common.net.messages.client.trade.TradeOfferExpiredPacket
 import com.cobblemon.mod.common.net.messages.client.trade.TradeOfferNotificationPacket
@@ -101,71 +102,98 @@ object TradeManager : RequestManager<TradeManager.TradeRequest>() {
     fun performTrade(
         activeTrade: ActiveTrade,
         player1: TradeParticipant,
-        pokemon1: Pokemon,
+        pokemon1: List<Pokemon>,
         player2: TradeParticipant,
-        pokemon2: Pokemon
+        pokemon2: List<Pokemon>
     ) {
         val party1 = player1.party
         val party2 = player2.party
 
-        if (pokemon1 !in party1 || pokemon2 !in party2) {
+        if (pokemon1.any { it !in party1 } || pokemon2.any { it !in party2 }) {
             Cobblemon.LOGGER.warn("Attempted to perform a trade with Pokémon that aren't in the party anymore. Could be attempted duping between ${player1.name} and ${player2.name}")
             activeTrade.cancelTrade()
             return
         }
 
-        CobblemonEvents.TRADE_EVENT_PRE.postThen(TradeEvent.Pre(player1, pokemon2, player2, pokemon1)) {
-            val party1 = player1.party
-            val party2 = player2.party
+        if (pokemon1.isEmpty() || pokemon2.isEmpty()) {
+            Cobblemon.LOGGER.warn("Attempted to perform a trade where one side offered no Pokémon between ${player1.name} and ${player2.name}. This should never happen.")
+            activeTrade.cancelTrade()
+            return
+        }
 
-            val player1Removed = party1.remove(pokemon1)
-            val player2Removed = party2.remove(pokemon2)
+        CobblemonEvents.TRADE_EVENT_PRE.postThen(
+            TradeEvent.Pre(player1, pokemon2, player2, pokemon1)
+        ) {
+            val player1Removed = pokemon1.filter { party1.remove(it) }
+            val player2Removed = pokemon2.filter { party2.remove(it) }
 
-            if (!player1Removed || !player2Removed) {
-                if (!player1Removed) {
-                    Cobblemon.LOGGER.warn("Failed to remove traded Pokémon ${pokemon1.species.resourceIdentifier} from ${player1.name.string}(${player1.uuid}). Aborting trade with ${player2.name.string}(${player2.uuid}), potential exploit abused.")
+            if (player1Removed.size != pokemon1.size || player2Removed.size != pokemon2.size) {
+                (pokemon1 - player1Removed.toSet()).forEach {
+                    Cobblemon.LOGGER.warn("Failed to remove traded Pokémon ${it.species.resourceIdentifier} from ${player1.name.string}(${player1.uuid}). Aborting trade with ${player2.name.string}(${player2.uuid}), potential exploit abused.")
                 }
 
-                if (!player2Removed) {
-                    Cobblemon.LOGGER.warn("Failed to remove traded Pokémon ${pokemon2.species.resourceIdentifier} from ${player2.name.string}(${player2.uuid}). Aborting trade with ${player1.name.string}(${player1.uuid}), potential exploit abused.")
+                (pokemon2 - player2Removed.toSet()).forEach {
+                    Cobblemon.LOGGER.warn("Failed to remove traded Pokémon ${it.species.resourceIdentifier} from ${player2.name.string}(${player2.uuid}). Aborting trade with ${player1.name.string}(${player1.uuid}), potential exploit abused.")
                 }
 
                 // Revert any changes if one of the removals failed
-                if (player1Removed) party1.add(pokemon1)
-                if (player2Removed) party2.add(pokemon2)
+                player1Removed.forEach { party1.add(it) }
+                player2Removed.forEach { party2.add(it) }
                 return@postThen
             }
 
             // If player1 is the OT, keep track of the friendship
-            pokemon1.cacheFriendship(player1.uuid)
+            pokemon1.forEach { it.cacheFriendship(player1.uuid) }
             // If player2 is the OT, keep track of the friendship
-            pokemon2.cacheFriendship(player2.uuid)
+            pokemon2.forEach { it.cacheFriendship(player2.uuid) }
 
-            // If pokemon2 was originally player1's, set the friendship back to what it was at point of trading
-            if ( !pokemon2.restoreFriendship(player1.uuid) ) {
-                // Otherwise, reset the friendship
-                pokemon2.setFriendship(pokemon2.form.baseFriendship)
+            // If a Pokémon received by player1 was originally theirs, set the friendship back to what it was at point of trading
+            pokemon2.forEach {
+                if (!it.restoreFriendship(player1.uuid)) {
+                    // Otherwise, reset the friendship
+                    it.setFriendship(it.form.baseFriendship)
+                }
             }
-            // If pokemon1 was originally player2's, set the friendship back to what it was at point of trading
-            if ( !pokemon1.restoreFriendship(player2.uuid) ) {
-                // Otherwise, reset the friendship
-                pokemon1.setFriendship(pokemon1.form.baseFriendship)
+            // If a Pokémon received by player2 was originally theirs, set the friendship back to what it was at point of trading
+            pokemon1.forEach {
+                if (!it.restoreFriendship(player2.uuid)) {
+                    // Otherwise, reset the friendship
+                    it.setFriendship(it.form.baseFriendship)
+                }
             }
 
-            party2.add(pokemon1)
-            party1.add(pokemon2)
+            pokemon1.forEach { party2.add(it) }
+            pokemon2.forEach { party1.add(it) }
 
-            pokemon1.lockedEvolutions.filterIsInstance<TradeEvolution>().firstOrNull {
-                it.attemptEvolution(pokemon1, pokemon2)
-            }
+            // Each traded Pokémon may evolve if any of the Pokémon it was traded for satisfies its context.
+            // Evolutions are resolved before any are applied so one evolving can't invalidate another's context.
+            (pokemon1.map { it to pokemon2 } + pokemon2.map { it to pokemon1 })
+                .mapNotNull { (pokemon, tradedFor) ->
+                    pokemon.lockedEvolutions.filterIsInstance<TradeEvolution>()
+                        .firstOrNull { evolution -> tradedFor.any { evolution.testContext(pokemon, it) } && evolution.test(pokemon) }
+                        ?.let { pokemon to it }
+                }
+                .forEach { (pokemon, evolution) -> evolution.evolve(pokemon) }
 
-            pokemon2.lockedEvolutions.filterIsInstance<TradeEvolution>().firstOrNull {
-                it.attemptEvolution(pokemon2, pokemon1)
+            val compactParty = { party: PartyStore ->
+                var writeIdx = 0
+                for (readIdx in 0 until party.size()) {
+                    if (party.get(readIdx) != null) {
+                        if (readIdx != writeIdx) {
+                            party.swap(readIdx, writeIdx)
+                        }
+                        writeIdx++
+                    }
+                }
             }
+            compactParty(party1)
+            compactParty(party2)
 
             activeTrade.completeTrade()
 
-            CobblemonEvents.TRADE_EVENT_POST.post(TradeEvent.Post(player1, pokemon2, player2, pokemon1))
+            CobblemonEvents.TRADE_EVENT_POST.post(
+                TradeEvent.Post(player1, pokemon2, player2, pokemon1)
+            )
         }
     }
 }

common/src/main/kotlin/com/cobblemon/mod/common/trade/TradeOffer.kt

@@ -11,10 +11,10 @@ package com.cobblemon.mod.common.trade
 import com.cobblemon.mod.common.pokemon.Pokemon
 
 class TradeOffer {
-    var pokemon: Pokemon? = null
+    var pokemon: List<Pokemon> = emptyList()
     var accepted = false
 
-    fun updateOffer(pokemon: Pokemon?) {
+    fun updateOffer(pokemon: List<Pokemon>) {
         this.pokemon = pokemon
         accepted = false
     }

common/src/main/kotlin/com/cobblemon/mod/common/trade/TradeParticipant.kt

@@ -34,7 +34,7 @@ interface TradeParticipant {
      *
      * If it's null, it means they're no longer offering a Pokémon (so they're redeciding).
      */
-    fun updateOffer(trade: ActiveTrade, tradeParticipant: TradeParticipant, pokemon: Pokemon?)
+    fun updateOffer(trade: ActiveTrade, tradeParticipant: TradeParticipant, pokemon: List<Pokemon>)
 
     /**
      * Notifies the participant that the acceptance state for trading with the opponent [Pokemon] with UUID [pokemonId]
@@ -59,7 +59,7 @@ interface TradeParticipant {
     fun cancelTrade(trade: ActiveTrade)
 
     /** Notifies the participant that the trade has been completed. The actual Pokémon have already been exchanged. */
-    fun completeTrade(trade: ActiveTrade, pokemonId1: UUID, pokemonId2: UUID)
+    fun completeTrade(trade: ActiveTrade, pokemonIds1: List<UUID>, pokemonIds2: List<UUID>)
 }
 
 /**
@@ -73,7 +73,7 @@ class PlayerTradeParticipant(val player: ServerPlayer): TradeParticipant {
     override val uuid = player.uuid
     override val party = player.party()
 
-    override fun updateOffer(trade: ActiveTrade, tradeParticipant: TradeParticipant, pokemon: Pokemon?) {
+    override fun updateOffer(trade: ActiveTrade, tradeParticipant: TradeParticipant, pokemon: List<Pokemon>) {
         player.sendPacket(TradeUpdatedPacket(tradeParticipant.uuid, pokemon))
     }
 
@@ -89,8 +89,8 @@ class PlayerTradeParticipant(val player: ServerPlayer): TradeParticipant {
         player.sendPacket(TradeCancelledPacket())
     }
 
-    override fun completeTrade(trade: ActiveTrade, pokemonId1: UUID, pokemonId2: UUID) {
-        player.sendPacket(TradeCompletedPacket(pokemonId1, pokemonId2))
+    override fun completeTrade(trade: ActiveTrade, pokemonIds1: List<UUID>, pokemonIds2: List<UUID>) {
+        player.sendPacket(TradeCompletedPacket(pokemonIds1, pokemonIds2))
     }
 }
 
@@ -109,7 +109,7 @@ class DummyTradeParticipant(val pokemonList: MutableList<Pokemon>) : TradePartic
         // Don't need to do any notifying.
     }
 
-    override fun completeTrade(trade: ActiveTrade, pokemonId1: UUID, pokemonId2: UUID) {
+    override fun completeTrade(trade: ActiveTrade, pokemonIds1: List<UUID>, pokemonIds2: List<UUID>) {
         // Don't need to do any notifying.
     }
 
@@ -121,7 +121,7 @@ class DummyTradeParticipant(val pokemonList: MutableList<Pokemon>) : TradePartic
         // React, maybe. Change code and hotswap.
     }
 
-    override fun updateOffer(trade: ActiveTrade, tradeParticipant: TradeParticipant, pokemon: Pokemon?) {
+    override fun updateOffer(trade: ActiveTrade, tradeParticipant: TradeParticipant, pokemon: List<Pokemon>) {
         // React, maybe. Change code and hotswap.
     }
 }