diff --git a/redwood-compose/api/redwood-compose.klib.api b/redwood-compose/api/redwood-compose.klib.api
index 4d0dcfd0e5..d4cabe2c36 100644
--- a/redwood-compose/api/redwood-compose.klib.api
+++ b/redwood-compose/api/redwood-compose.klib.api
@@ -95,8 +95,20 @@ final object app.cash.redwood.compose/WindowAnimationFrameClock : androidx.compo
     final suspend fun <#A1: kotlin/Any?> withFrameNanos(kotlin/Function1<kotlin/Long, #A1>): #A1 // app.cash.redwood.compose/WindowAnimationFrameClock.withFrameNanos|withFrameNanos(kotlin.Function1<kotlin.Long,0:0>){0§<kotlin.Any?>}[0]
 }
 
+// Targets: [js]
+final val app.cash.redwood.compose/app_cash_redwood_compose_JsArray$stableprop // app.cash.redwood.compose/app_cash_redwood_compose_JsArray$stableprop|#static{}app_cash_redwood_compose_JsArray$stableprop[0]
+
+// Targets: [js]
+final val app.cash.redwood.compose/app_cash_redwood_compose_JsSet$stableprop // app.cash.redwood.compose/app_cash_redwood_compose_JsSet$stableprop|#static{}app_cash_redwood_compose_JsSet$stableprop[0]
+
 // Targets: [js]
 final val app.cash.redwood.compose/app_cash_redwood_compose_WindowAnimationFrameClock$stableprop // app.cash.redwood.compose/app_cash_redwood_compose_WindowAnimationFrameClock$stableprop|#static{}app_cash_redwood_compose_WindowAnimationFrameClock$stableprop[0]
 
+// Targets: [js]
+final fun app.cash.redwood.compose/app_cash_redwood_compose_JsArray$stableprop_getter(): kotlin/Int // app.cash.redwood.compose/app_cash_redwood_compose_JsArray$stableprop_getter|app_cash_redwood_compose_JsArray$stableprop_getter(){}[0]
+
+// Targets: [js]
+final fun app.cash.redwood.compose/app_cash_redwood_compose_JsSet$stableprop_getter(): kotlin/Int // app.cash.redwood.compose/app_cash_redwood_compose_JsSet$stableprop_getter|app_cash_redwood_compose_JsSet$stableprop_getter(){}[0]
+
 // Targets: [js]
 final fun app.cash.redwood.compose/app_cash_redwood_compose_WindowAnimationFrameClock$stableprop_getter(): kotlin/Int // app.cash.redwood.compose/app_cash_redwood_compose_WindowAnimationFrameClock$stableprop_getter|app_cash_redwood_compose_WindowAnimationFrameClock$stableprop_getter(){}[0]
diff --git a/redwood-compose/build.gradle b/redwood-compose/build.gradle
index e9cb1e4d90..ddcd1641e4 100644
--- a/redwood-compose/build.gradle
+++ b/redwood-compose/build.gradle
@@ -10,9 +10,18 @@ redwoodBuild {
 apply plugin: 'org.jetbrains.kotlin.plugin.compose'
 
 kotlin {
+  applyDefaultHierarchyTemplate {
+    it.group("common") {
+      it.group("nonJs") {
+        it.group("ios") {}
+        it.withAndroidTarget()
+        it.withJvm()
+      }
+    }
+  }
+
   sourceSets {
     commonMain {
-      kotlin.srcDir(redwoodBuild.generateComposeHelpers(tasks, 'app.cash.redwood.compose'))
       dependencies {
         api libs.kotlinx.coroutines.core
         api projects.redwoodRuntime
@@ -37,6 +46,12 @@ kotlin {
         implementation libs.androidx.core
       }
     }
+    nonJsMain {
+      kotlin.srcDir(redwoodBuild.generateComposeHelpers(tasks, 'app.cash.redwood.compose'))
+      dependencies {
+        implementation libs.jetbrains.compose.collection
+      }
+    }
   }
 }
 
diff --git a/redwood-compose/src/commonMain/kotlin/app/cash/redwood/compose/PlatformList.kt b/redwood-compose/src/commonMain/kotlin/app/cash/redwood/compose/PlatformList.kt
new file mode 100644
index 0000000000..abd24e45ca
--- /dev/null
+++ b/redwood-compose/src/commonMain/kotlin/app/cash/redwood/compose/PlatformList.kt
@@ -0,0 +1,30 @@
+/*
+ * Copyright (C) 2024 Square, Inc.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+package app.cash.redwood.compose
+
+internal expect class PlatformList<T>
+
+internal expect inline fun <T> platformListOf(): PlatformList<T>
+
+internal expect inline val <T> PlatformList<T>.size: Int
+
+internal expect inline operator fun <T> PlatformList<T>.get(index: Int): T
+
+internal expect inline fun <T> PlatformList<T>.add(index: Int, element: T)
+
+internal expect inline fun <T> PlatformList<T>.remove(index: Int, count: Int)
+
+internal expect fun <T> PlatformList<T>.move(from: Int, to: Int, count: Int)
diff --git a/redwood-compose/src/commonMain/kotlin/app/cash/redwood/compose/PlatformSet.kt b/redwood-compose/src/commonMain/kotlin/app/cash/redwood/compose/PlatformSet.kt
new file mode 100644
index 0000000000..dcd1572901
--- /dev/null
+++ b/redwood-compose/src/commonMain/kotlin/app/cash/redwood/compose/PlatformSet.kt
@@ -0,0 +1,26 @@
+/*
+ * Copyright (C) 2024 Square, Inc.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+package app.cash.redwood.compose
+
+internal expect class PlatformSet<T>
+
+internal expect inline fun <T> platformSetOf(): PlatformSet<T>
+
+internal expect inline operator fun <T> PlatformSet<T>.plusAssign(element: T)
+
+internal expect inline fun <T> PlatformSet<T>.forEach(crossinline block: (T) -> Unit)
+
+internal expect inline fun <T> PlatformSet<T>.clear()
diff --git a/redwood-compose/src/commonMain/kotlin/app/cash/redwood/compose/WidgetApplier.kt b/redwood-compose/src/commonMain/kotlin/app/cash/redwood/compose/WidgetApplier.kt
index 493ef0f3a2..e11eed7286 100644
--- a/redwood-compose/src/commonMain/kotlin/app/cash/redwood/compose/WidgetApplier.kt
+++ b/redwood-compose/src/commonMain/kotlin/app/cash/redwood/compose/WidgetApplier.kt
@@ -58,7 +58,7 @@ internal class NodeApplier<W : Any>(
 ) : AbstractApplier<Node<W>>(ChildrenNode(root)),
   RedwoodApplier<W> {
   private var closed = false
-  private val changedWidgets = LinkedHashSet<ChangeListener>()
+  private val changedWidgets = platformSetOf<ChangeListener>()
 
   override fun recordChanged(widget: Widget<W>) {
     if (widget is ChangeListener) {
@@ -69,10 +69,12 @@ internal class NodeApplier<W : Any>(
   override fun onEndChanges() {
     check(!closed)
 
-    for (changedWidget in changedWidgets) {
-      changedWidget.onEndChanges()
+    changedWidgets.let { changedWidgets ->
+      changedWidgets.forEach { changedWidget ->
+        changedWidget.onEndChanges()
+      }
+      changedWidgets.clear()
     }
-    changedWidgets.clear()
 
     onEndChanges.invoke()
   }
@@ -191,7 +193,7 @@ internal class ChildrenNode<W : Any> private constructor(
   constructor(accessor: (Widget<W>) -> Widget.Children<W>) : this(accessor, null, null)
   constructor(children: Widget.Children<W>) : this(null, null, children)
 
-  private val nodes = mutableListOf<WidgetNode<Widget<W>, W>>()
+  private val nodes = platformListOf<WidgetNode<Widget<W>, W>>()
 
   fun insert(index: Int, node: WidgetNode<Widget<W>, W>) {
     nodes.let { nodes ->
diff --git a/redwood-compose/src/jsMain/kotlin/app/cash/redwood/compose/PlatformList.kt b/redwood-compose/src/jsMain/kotlin/app/cash/redwood/compose/PlatformList.kt
new file mode 100644
index 0000000000..ca70043ee4
--- /dev/null
+++ b/redwood-compose/src/jsMain/kotlin/app/cash/redwood/compose/PlatformList.kt
@@ -0,0 +1,53 @@
+/*
+ * Copyright (C) 2024 Square, Inc.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+@file:Suppress("NOTHING_TO_INLINE")
+
+package app.cash.redwood.compose
+
+@JsName("Array")
+internal external class JsArray<T> {
+  val length: Int
+  fun splice(start: Int, deleteCount: Int): JsArray<T>
+  fun splice(start: Int, deleteCount: Int, element: T)
+}
+
+internal actual typealias PlatformList<T> = JsArray<T>
+
+internal actual inline fun <T> platformListOf(): PlatformList<T> {
+  return js("[]").unsafeCast<PlatformList<T>>()
+}
+
+internal actual inline val <T> PlatformList<T>.size: Int get() = length
+
+internal actual inline operator fun <T> PlatformList<T>.get(index: Int): T {
+  return asDynamic()[index]
+}
+
+internal actual inline fun <T> PlatformList<T>.add(index: Int, element: T) {
+  splice(index, 0, element)
+}
+
+internal actual inline fun <T> PlatformList<T>.remove(index: Int, count: Int) {
+  splice(index, count)
+}
+
+internal actual fun <T> PlatformList<T>.move(from: Int, to: Int, count: Int) {
+  val dest = if (from > to) to else to - count
+  val removed = splice(from, count)
+  repeat(count) { offset ->
+    splice(dest + offset, 0, removed[offset])
+  }
+}
diff --git a/redwood-compose/src/jsMain/kotlin/app/cash/redwood/compose/PlatformSet.kt b/redwood-compose/src/jsMain/kotlin/app/cash/redwood/compose/PlatformSet.kt
new file mode 100644
index 0000000000..f841531495
--- /dev/null
+++ b/redwood-compose/src/jsMain/kotlin/app/cash/redwood/compose/PlatformSet.kt
@@ -0,0 +1,43 @@
+/*
+ * Copyright (C) 2024 Square, Inc.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+@file:Suppress("NOTHING_TO_INLINE")
+
+package app.cash.redwood.compose
+
+@JsName("Set")
+internal external class JsSet<T> {
+  fun add(element: T)
+  fun clear()
+  fun forEach(block: (T) -> Unit)
+}
+
+internal actual typealias PlatformSet<T> = JsSet<T>
+
+internal actual inline fun <T> platformSetOf(): PlatformSet<T> {
+  return JsSet()
+}
+
+internal actual inline operator fun <T> PlatformSet<T>.plusAssign(element: T) {
+  add(element)
+}
+
+internal actual inline fun <T> PlatformSet<T>.forEach(crossinline block: (T) -> Unit) {
+  forEach { block(it) }
+}
+
+internal actual inline fun <T> PlatformSet<T>.clear() {
+  clear()
+}
diff --git a/redwood-compose/src/nonJsMain/kotlin/app/cash/redwood/compose/PlatformList.kt b/redwood-compose/src/nonJsMain/kotlin/app/cash/redwood/compose/PlatformList.kt
new file mode 100644
index 0000000000..ea180cc417
--- /dev/null
+++ b/redwood-compose/src/nonJsMain/kotlin/app/cash/redwood/compose/PlatformList.kt
@@ -0,0 +1,45 @@
+/*
+ * Copyright (C) 2024 Square, Inc.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+@file:Suppress("NOTHING_TO_INLINE")
+
+package app.cash.redwood.compose
+
+@Suppress("ACTUAL_TYPE_ALIAS_NOT_TO_CLASS") // On the JVM it aliases to java.util.ArrayList.
+internal actual typealias PlatformList<T> = ArrayList<T>
+
+internal actual inline fun <T> platformListOf(): PlatformList<T> {
+  return ArrayList()
+}
+
+internal actual inline val <T> PlatformList<T>.size: Int get() = size
+
+internal actual inline operator fun <T> PlatformList<T>.get(index: Int): T {
+  return get(index)
+}
+
+internal actual inline fun <T> PlatformList<T>.add(index: Int, element: T) {
+  add(index, element)
+}
+
+internal actual inline fun <T> PlatformList<T>.remove(index: Int, count: Int) {
+  // Force resolution to the generated extension.
+  (this as MutableList<T>).remove(index, count)
+}
+
+internal actual inline fun <T> PlatformList<T>.move(from: Int, to: Int, count: Int) {
+  // Force resolution to the generated extension.
+  (this as MutableList<T>).move(from, to, count)
+}
diff --git a/redwood-compose/src/nonJsMain/kotlin/app/cash/redwood/compose/PlatformSet.kt b/redwood-compose/src/nonJsMain/kotlin/app/cash/redwood/compose/PlatformSet.kt
new file mode 100644
index 0000000000..f87fc19554
--- /dev/null
+++ b/redwood-compose/src/nonJsMain/kotlin/app/cash/redwood/compose/PlatformSet.kt
@@ -0,0 +1,39 @@
+/*
+ * Copyright (C) 2024 Square, Inc.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+@file:Suppress("NOTHING_TO_INLINE")
+
+package app.cash.redwood.compose
+
+import androidx.collection.MutableScatterSet
+import androidx.collection.mutableScatterSetOf
+
+internal actual typealias PlatformSet<T> = MutableScatterSet<T>
+
+internal actual inline fun <T> platformSetOf(): PlatformSet<T> {
+  return mutableScatterSetOf()
+}
+
+internal actual inline operator fun <T> PlatformSet<T>.plusAssign(element: T) {
+  plusAssign(element)
+}
+
+internal actual inline fun <T> PlatformSet<T>.forEach(block: (T) -> Unit) {
+  forEach(block)
+}
+
+internal actual inline fun <T> PlatformSet<T>.clear() {
+  clear()
+}