diff --git a/redwood-protocol-guest/api/redwood-protocol-guest.api b/redwood-protocol-guest/api/redwood-protocol-guest.api
index 4a14797de5..4161cf6673 100644
--- a/redwood-protocol-guest/api/redwood-protocol-guest.api
+++ b/redwood-protocol-guest/api/redwood-protocol-guest.api
@@ -13,7 +13,6 @@ public final class app/cash/redwood/protocol/guest/DefaultGuestProtocolAdapter :
 	public fun emitChanges ()V
 	public fun getJson ()Lkotlinx/serialization/json/Json;
 	public fun getRoot ()Lapp/cash/redwood/widget/Widget$Children;
-	public fun getSynthesizeSubtreeRemoval ()Z
 	public fun getWidgetSystem ()Lapp/cash/redwood/widget/WidgetSystem;
 	public fun initChangesSink (Lapp/cash/redwood/protocol/ChangesSink;)V
 	public fun nextId-0HhLjSo ()I
@@ -22,7 +21,9 @@ public final class app/cash/redwood/protocol/guest/DefaultGuestProtocolAdapter :
 	public final fun takeChanges ()Ljava/util/List;
 }
 
-public abstract interface class app/cash/redwood/protocol/guest/GuestProtocolAdapter : app/cash/redwood/protocol/EventSink {
+public abstract class app/cash/redwood/protocol/guest/GuestProtocolAdapter : app/cash/redwood/protocol/EventSink {
+	public static final field $stable I
+	public synthetic fun <init> (Ljava/lang/String;Lkotlin/jvm/internal/DefaultConstructorMarker;)V
 	public abstract fun appendAdd-ARs5Qwk (IIILapp/cash/redwood/protocol/guest/ProtocolWidget;)V
 	public abstract fun appendCreate-kyz2zXs (II)V
 	public abstract fun appendModifierChange-z3jyS0k (ILapp/cash/redwood/Modifier;)V
@@ -31,11 +32,11 @@ public abstract interface class app/cash/redwood/protocol/guest/GuestProtocolAda
 	public abstract fun appendPropertyChange-M7EZMwg (III)V
 	public abstract fun appendPropertyChange-e3iP1vo (IIZ)V
 	public abstract fun appendRemove-HpxY78w (IIIILjava/util/List;)V
-	public static synthetic fun appendRemove-HpxY78w$default (Lapp/cash/redwood/protocol/guest/GuestProtocolAdapter;IIIILjava/util/List;ILjava/lang/Object;)V
 	public abstract fun emitChanges ()V
+	public final fun getChildrenVisitor ()Lapp/cash/redwood/protocol/guest/ProtocolWidget$ChildrenVisitor;
 	public abstract fun getJson ()Lkotlinx/serialization/json/Json;
 	public abstract fun getRoot ()Lapp/cash/redwood/widget/Widget$Children;
-	public abstract fun getSynthesizeSubtreeRemoval ()Z
+	public final fun getSynthesizeSubtreeRemoval ()Z
 	public abstract fun getWidgetSystem ()Lapp/cash/redwood/widget/WidgetSystem;
 	public abstract fun initChangesSink (Lapp/cash/redwood/protocol/ChangesSink;)V
 	public abstract fun nextId-0HhLjSo ()I
@@ -58,7 +59,7 @@ public final class app/cash/redwood/protocol/guest/ProtocolRedwoodCompositionKt
 }
 
 public abstract interface class app/cash/redwood/protocol/guest/ProtocolWidget : app/cash/redwood/widget/Widget {
-	public abstract fun depthFirstWalk (Lkotlin/jvm/functions/Function3;)V
+	public abstract fun depthFirstWalk (Lapp/cash/redwood/protocol/guest/ProtocolWidget$ChildrenVisitor;)V
 	public abstract fun getId-0HhLjSo ()I
 	public abstract fun getTag-BlhN7y0 ()I
 	public synthetic fun getValue ()Ljava/lang/Object;
@@ -66,10 +67,14 @@ public abstract interface class app/cash/redwood/protocol/guest/ProtocolWidget :
 	public abstract fun sendEvent (Lapp/cash/redwood/protocol/Event;)V
 }
 
+public abstract interface class app/cash/redwood/protocol/guest/ProtocolWidget$ChildrenVisitor {
+	public abstract fun visit-KUkifdM (Lapp/cash/redwood/protocol/guest/ProtocolWidget;ILapp/cash/redwood/protocol/guest/ProtocolWidgetChildren;)V
+}
+
 public final class app/cash/redwood/protocol/guest/ProtocolWidgetChildren : app/cash/redwood/widget/Widget$Children {
 	public static final field $stable I
 	public synthetic fun <init> (IILapp/cash/redwood/protocol/guest/GuestProtocolAdapter;Lkotlin/jvm/internal/DefaultConstructorMarker;)V
-	public final fun depthFirstWalk (Lapp/cash/redwood/protocol/guest/ProtocolWidget;Lkotlin/jvm/functions/Function3;)V
+	public final fun depthFirstWalk (Lapp/cash/redwood/protocol/guest/ProtocolWidget;Lapp/cash/redwood/protocol/guest/ProtocolWidget$ChildrenVisitor;)V
 	public fun detach ()V
 	public fun getWidgets ()Ljava/util/List;
 	public fun insert (ILapp/cash/redwood/widget/Widget;)V
diff --git a/redwood-protocol-guest/api/redwood-protocol-guest.klib.api b/redwood-protocol-guest/api/redwood-protocol-guest.klib.api
index 639566f456..98cbb26011 100644
--- a/redwood-protocol-guest/api/redwood-protocol-guest.klib.api
+++ b/redwood-protocol-guest/api/redwood-protocol-guest.klib.api
@@ -6,30 +6,6 @@
 // - Show declarations: true
 
 // Library unique name: <app.cash.redwood:redwood-protocol-guest>
-abstract interface app.cash.redwood.protocol.guest/GuestProtocolAdapter : app.cash.redwood.protocol/EventSink { // app.cash.redwood.protocol.guest/GuestProtocolAdapter|null[0]
-    abstract val json // app.cash.redwood.protocol.guest/GuestProtocolAdapter.json|{}json[0]
-        abstract fun <get-json>(): kotlinx.serialization.json/Json // app.cash.redwood.protocol.guest/GuestProtocolAdapter.json.<get-json>|<get-json>(){}[0]
-    abstract val root // app.cash.redwood.protocol.guest/GuestProtocolAdapter.root|{}root[0]
-        abstract fun <get-root>(): app.cash.redwood.widget/Widget.Children<kotlin/Unit> // app.cash.redwood.protocol.guest/GuestProtocolAdapter.root.<get-root>|<get-root>(){}[0]
-    abstract val synthesizeSubtreeRemoval // app.cash.redwood.protocol.guest/GuestProtocolAdapter.synthesizeSubtreeRemoval|{}synthesizeSubtreeRemoval[0]
-        abstract fun <get-synthesizeSubtreeRemoval>(): kotlin/Boolean // app.cash.redwood.protocol.guest/GuestProtocolAdapter.synthesizeSubtreeRemoval.<get-synthesizeSubtreeRemoval>|<get-synthesizeSubtreeRemoval>(){}[0]
-    abstract val widgetSystem // app.cash.redwood.protocol.guest/GuestProtocolAdapter.widgetSystem|{}widgetSystem[0]
-        abstract fun <get-widgetSystem>(): app.cash.redwood.widget/WidgetSystem<kotlin/Unit> // app.cash.redwood.protocol.guest/GuestProtocolAdapter.widgetSystem.<get-widgetSystem>|<get-widgetSystem>(){}[0]
-
-    abstract fun <#A1: kotlin/Any?> appendPropertyChange(app.cash.redwood.protocol/Id, app.cash.redwood.protocol/PropertyTag, kotlinx.serialization/KSerializer<#A1>, #A1) // app.cash.redwood.protocol.guest/GuestProtocolAdapter.appendPropertyChange|appendPropertyChange(app.cash.redwood.protocol.Id;app.cash.redwood.protocol.PropertyTag;kotlinx.serialization.KSerializer<0:0>;0:0){0§<kotlin.Any?>}[0]
-    abstract fun appendAdd(app.cash.redwood.protocol/Id, app.cash.redwood.protocol/ChildrenTag, kotlin/Int, app.cash.redwood.protocol.guest/ProtocolWidget) // app.cash.redwood.protocol.guest/GuestProtocolAdapter.appendAdd|appendAdd(app.cash.redwood.protocol.Id;app.cash.redwood.protocol.ChildrenTag;kotlin.Int;app.cash.redwood.protocol.guest.ProtocolWidget){}[0]
-    abstract fun appendCreate(app.cash.redwood.protocol/Id, app.cash.redwood.protocol/WidgetTag) // app.cash.redwood.protocol.guest/GuestProtocolAdapter.appendCreate|appendCreate(app.cash.redwood.protocol.Id;app.cash.redwood.protocol.WidgetTag){}[0]
-    abstract fun appendModifierChange(app.cash.redwood.protocol/Id, app.cash.redwood/Modifier) // app.cash.redwood.protocol.guest/GuestProtocolAdapter.appendModifierChange|appendModifierChange(app.cash.redwood.protocol.Id;app.cash.redwood.Modifier){}[0]
-    abstract fun appendMove(app.cash.redwood.protocol/Id, app.cash.redwood.protocol/ChildrenTag, kotlin/Int, kotlin/Int, kotlin/Int) // app.cash.redwood.protocol.guest/GuestProtocolAdapter.appendMove|appendMove(app.cash.redwood.protocol.Id;app.cash.redwood.protocol.ChildrenTag;kotlin.Int;kotlin.Int;kotlin.Int){}[0]
-    abstract fun appendPropertyChange(app.cash.redwood.protocol/Id, app.cash.redwood.protocol/PropertyTag, kotlin/Boolean) // app.cash.redwood.protocol.guest/GuestProtocolAdapter.appendPropertyChange|appendPropertyChange(app.cash.redwood.protocol.Id;app.cash.redwood.protocol.PropertyTag;kotlin.Boolean){}[0]
-    abstract fun appendPropertyChange(app.cash.redwood.protocol/Id, app.cash.redwood.protocol/PropertyTag, kotlin/UInt) // app.cash.redwood.protocol.guest/GuestProtocolAdapter.appendPropertyChange|appendPropertyChange(app.cash.redwood.protocol.Id;app.cash.redwood.protocol.PropertyTag;kotlin.UInt){}[0]
-    abstract fun appendRemove(app.cash.redwood.protocol/Id, app.cash.redwood.protocol/ChildrenTag, kotlin/Int, kotlin/Int, kotlin.collections/List<app.cash.redwood.protocol/Id> = ...) // app.cash.redwood.protocol.guest/GuestProtocolAdapter.appendRemove|appendRemove(app.cash.redwood.protocol.Id;app.cash.redwood.protocol.ChildrenTag;kotlin.Int;kotlin.Int;kotlin.collections.List<app.cash.redwood.protocol.Id>){}[0]
-    abstract fun emitChanges() // app.cash.redwood.protocol.guest/GuestProtocolAdapter.emitChanges|emitChanges(){}[0]
-    abstract fun initChangesSink(app.cash.redwood.protocol/ChangesSink) // app.cash.redwood.protocol.guest/GuestProtocolAdapter.initChangesSink|initChangesSink(app.cash.redwood.protocol.ChangesSink){}[0]
-    abstract fun nextId(): app.cash.redwood.protocol/Id // app.cash.redwood.protocol.guest/GuestProtocolAdapter.nextId|nextId(){}[0]
-    abstract fun removeWidget(app.cash.redwood.protocol/Id) // app.cash.redwood.protocol.guest/GuestProtocolAdapter.removeWidget|removeWidget(app.cash.redwood.protocol.Id){}[0]
-}
-
 abstract interface app.cash.redwood.protocol.guest/ProtocolMismatchHandler { // app.cash.redwood.protocol.guest/ProtocolMismatchHandler|null[0]
     abstract fun onUnknownEvent(app.cash.redwood.protocol/WidgetTag, app.cash.redwood.protocol/EventTag) // app.cash.redwood.protocol.guest/ProtocolMismatchHandler.onUnknownEvent|onUnknownEvent(app.cash.redwood.protocol.WidgetTag;app.cash.redwood.protocol.EventTag){}[0]
     abstract fun onUnknownEventNode(app.cash.redwood.protocol/Id, app.cash.redwood.protocol/EventTag) // app.cash.redwood.protocol.guest/ProtocolMismatchHandler.onUnknownEventNode|onUnknownEventNode(app.cash.redwood.protocol.Id;app.cash.redwood.protocol.EventTag){}[0]
@@ -48,8 +24,12 @@ abstract interface app.cash.redwood.protocol.guest/ProtocolWidget : app.cash.red
     open val value // app.cash.redwood.protocol.guest/ProtocolWidget.value|{}value[0]
         open fun <get-value>() // app.cash.redwood.protocol.guest/ProtocolWidget.value.<get-value>|<get-value>(){}[0]
 
-    abstract fun depthFirstWalk(kotlin/Function3<app.cash.redwood.protocol.guest/ProtocolWidget, app.cash.redwood.protocol/ChildrenTag, app.cash.redwood.protocol.guest/ProtocolWidgetChildren, kotlin/Unit>) // app.cash.redwood.protocol.guest/ProtocolWidget.depthFirstWalk|depthFirstWalk(kotlin.Function3<app.cash.redwood.protocol.guest.ProtocolWidget,app.cash.redwood.protocol.ChildrenTag,app.cash.redwood.protocol.guest.ProtocolWidgetChildren,kotlin.Unit>){}[0]
+    abstract fun depthFirstWalk(app.cash.redwood.protocol.guest/ProtocolWidget.ChildrenVisitor) // app.cash.redwood.protocol.guest/ProtocolWidget.depthFirstWalk|depthFirstWalk(app.cash.redwood.protocol.guest.ProtocolWidget.ChildrenVisitor){}[0]
     abstract fun sendEvent(app.cash.redwood.protocol/Event) // app.cash.redwood.protocol.guest/ProtocolWidget.sendEvent|sendEvent(app.cash.redwood.protocol.Event){}[0]
+
+    abstract fun interface ChildrenVisitor { // app.cash.redwood.protocol.guest/ProtocolWidget.ChildrenVisitor|null[0]
+        abstract fun visit(app.cash.redwood.protocol.guest/ProtocolWidget, app.cash.redwood.protocol/ChildrenTag, app.cash.redwood.protocol.guest/ProtocolWidgetChildren) // app.cash.redwood.protocol.guest/ProtocolWidget.ChildrenVisitor.visit|visit(app.cash.redwood.protocol.guest.ProtocolWidget;app.cash.redwood.protocol.ChildrenTag;app.cash.redwood.protocol.guest.ProtocolWidgetChildren){}[0]
+    }
 }
 
 abstract interface app.cash.redwood.protocol.guest/ProtocolWidgetSystemFactory { // app.cash.redwood.protocol.guest/ProtocolWidgetSystemFactory|null[0]
@@ -57,6 +37,34 @@ abstract interface app.cash.redwood.protocol.guest/ProtocolWidgetSystemFactory {
     abstract fun create(app.cash.redwood.protocol.guest/GuestProtocolAdapter, app.cash.redwood.protocol.guest/ProtocolMismatchHandler = ...): app.cash.redwood.widget/WidgetSystem<kotlin/Unit> // app.cash.redwood.protocol.guest/ProtocolWidgetSystemFactory.create|create(app.cash.redwood.protocol.guest.GuestProtocolAdapter;app.cash.redwood.protocol.guest.ProtocolMismatchHandler){}[0]
 }
 
+abstract class app.cash.redwood.protocol.guest/GuestProtocolAdapter : app.cash.redwood.protocol/EventSink { // app.cash.redwood.protocol.guest/GuestProtocolAdapter|null[0]
+    constructor <init>(app.cash.redwood.protocol/RedwoodVersion) // app.cash.redwood.protocol.guest/GuestProtocolAdapter.<init>|<init>(app.cash.redwood.protocol.RedwoodVersion){}[0]
+
+    abstract val json // app.cash.redwood.protocol.guest/GuestProtocolAdapter.json|{}json[0]
+        abstract fun <get-json>(): kotlinx.serialization.json/Json // app.cash.redwood.protocol.guest/GuestProtocolAdapter.json.<get-json>|<get-json>(){}[0]
+    abstract val root // app.cash.redwood.protocol.guest/GuestProtocolAdapter.root|{}root[0]
+        abstract fun <get-root>(): app.cash.redwood.widget/Widget.Children<kotlin/Unit> // app.cash.redwood.protocol.guest/GuestProtocolAdapter.root.<get-root>|<get-root>(){}[0]
+    abstract val widgetSystem // app.cash.redwood.protocol.guest/GuestProtocolAdapter.widgetSystem|{}widgetSystem[0]
+        abstract fun <get-widgetSystem>(): app.cash.redwood.widget/WidgetSystem<kotlin/Unit> // app.cash.redwood.protocol.guest/GuestProtocolAdapter.widgetSystem.<get-widgetSystem>|<get-widgetSystem>(){}[0]
+    final val childrenVisitor // app.cash.redwood.protocol.guest/GuestProtocolAdapter.childrenVisitor|{}childrenVisitor[0]
+        final fun <get-childrenVisitor>(): app.cash.redwood.protocol.guest/ProtocolWidget.ChildrenVisitor // app.cash.redwood.protocol.guest/GuestProtocolAdapter.childrenVisitor.<get-childrenVisitor>|<get-childrenVisitor>(){}[0]
+    final val synthesizeSubtreeRemoval // app.cash.redwood.protocol.guest/GuestProtocolAdapter.synthesizeSubtreeRemoval|{}synthesizeSubtreeRemoval[0]
+        final fun <get-synthesizeSubtreeRemoval>(): kotlin/Boolean // app.cash.redwood.protocol.guest/GuestProtocolAdapter.synthesizeSubtreeRemoval.<get-synthesizeSubtreeRemoval>|<get-synthesizeSubtreeRemoval>(){}[0]
+
+    abstract fun <#A1: kotlin/Any?> appendPropertyChange(app.cash.redwood.protocol/Id, app.cash.redwood.protocol/PropertyTag, kotlinx.serialization/KSerializer<#A1>, #A1) // app.cash.redwood.protocol.guest/GuestProtocolAdapter.appendPropertyChange|appendPropertyChange(app.cash.redwood.protocol.Id;app.cash.redwood.protocol.PropertyTag;kotlinx.serialization.KSerializer<0:0>;0:0){0§<kotlin.Any?>}[0]
+    abstract fun appendAdd(app.cash.redwood.protocol/Id, app.cash.redwood.protocol/ChildrenTag, kotlin/Int, app.cash.redwood.protocol.guest/ProtocolWidget) // app.cash.redwood.protocol.guest/GuestProtocolAdapter.appendAdd|appendAdd(app.cash.redwood.protocol.Id;app.cash.redwood.protocol.ChildrenTag;kotlin.Int;app.cash.redwood.protocol.guest.ProtocolWidget){}[0]
+    abstract fun appendCreate(app.cash.redwood.protocol/Id, app.cash.redwood.protocol/WidgetTag) // app.cash.redwood.protocol.guest/GuestProtocolAdapter.appendCreate|appendCreate(app.cash.redwood.protocol.Id;app.cash.redwood.protocol.WidgetTag){}[0]
+    abstract fun appendModifierChange(app.cash.redwood.protocol/Id, app.cash.redwood/Modifier) // app.cash.redwood.protocol.guest/GuestProtocolAdapter.appendModifierChange|appendModifierChange(app.cash.redwood.protocol.Id;app.cash.redwood.Modifier){}[0]
+    abstract fun appendMove(app.cash.redwood.protocol/Id, app.cash.redwood.protocol/ChildrenTag, kotlin/Int, kotlin/Int, kotlin/Int) // app.cash.redwood.protocol.guest/GuestProtocolAdapter.appendMove|appendMove(app.cash.redwood.protocol.Id;app.cash.redwood.protocol.ChildrenTag;kotlin.Int;kotlin.Int;kotlin.Int){}[0]
+    abstract fun appendPropertyChange(app.cash.redwood.protocol/Id, app.cash.redwood.protocol/PropertyTag, kotlin/Boolean) // app.cash.redwood.protocol.guest/GuestProtocolAdapter.appendPropertyChange|appendPropertyChange(app.cash.redwood.protocol.Id;app.cash.redwood.protocol.PropertyTag;kotlin.Boolean){}[0]
+    abstract fun appendPropertyChange(app.cash.redwood.protocol/Id, app.cash.redwood.protocol/PropertyTag, kotlin/UInt) // app.cash.redwood.protocol.guest/GuestProtocolAdapter.appendPropertyChange|appendPropertyChange(app.cash.redwood.protocol.Id;app.cash.redwood.protocol.PropertyTag;kotlin.UInt){}[0]
+    abstract fun appendRemove(app.cash.redwood.protocol/Id, app.cash.redwood.protocol/ChildrenTag, kotlin/Int, kotlin/Int, kotlin.collections/List<app.cash.redwood.protocol/Id>) // app.cash.redwood.protocol.guest/GuestProtocolAdapter.appendRemove|appendRemove(app.cash.redwood.protocol.Id;app.cash.redwood.protocol.ChildrenTag;kotlin.Int;kotlin.Int;kotlin.collections.List<app.cash.redwood.protocol.Id>){}[0]
+    abstract fun emitChanges() // app.cash.redwood.protocol.guest/GuestProtocolAdapter.emitChanges|emitChanges(){}[0]
+    abstract fun initChangesSink(app.cash.redwood.protocol/ChangesSink) // app.cash.redwood.protocol.guest/GuestProtocolAdapter.initChangesSink|initChangesSink(app.cash.redwood.protocol.ChangesSink){}[0]
+    abstract fun nextId(): app.cash.redwood.protocol/Id // app.cash.redwood.protocol.guest/GuestProtocolAdapter.nextId|nextId(){}[0]
+    abstract fun removeWidget(app.cash.redwood.protocol/Id) // app.cash.redwood.protocol.guest/GuestProtocolAdapter.removeWidget|removeWidget(app.cash.redwood.protocol.Id){}[0]
+}
+
 final class app.cash.redwood.protocol.guest/DefaultGuestProtocolAdapter : app.cash.redwood.protocol.guest/GuestProtocolAdapter { // app.cash.redwood.protocol.guest/DefaultGuestProtocolAdapter|null[0]
     constructor <init>(kotlinx.serialization.json/Json = ..., app.cash.redwood.protocol/RedwoodVersion, app.cash.redwood.protocol.guest/ProtocolWidgetSystemFactory, app.cash.redwood.protocol.guest/ProtocolMismatchHandler = ...) // app.cash.redwood.protocol.guest/DefaultGuestProtocolAdapter.<init>|<init>(kotlinx.serialization.json.Json;app.cash.redwood.protocol.RedwoodVersion;app.cash.redwood.protocol.guest.ProtocolWidgetSystemFactory;app.cash.redwood.protocol.guest.ProtocolMismatchHandler){}[0]
 
@@ -64,8 +72,6 @@ final class app.cash.redwood.protocol.guest/DefaultGuestProtocolAdapter : app.ca
         final fun <get-json>(): kotlinx.serialization.json/Json // app.cash.redwood.protocol.guest/DefaultGuestProtocolAdapter.json.<get-json>|<get-json>(){}[0]
     final val root // app.cash.redwood.protocol.guest/DefaultGuestProtocolAdapter.root|{}root[0]
         final fun <get-root>(): app.cash.redwood.widget/Widget.Children<kotlin/Unit> // app.cash.redwood.protocol.guest/DefaultGuestProtocolAdapter.root.<get-root>|<get-root>(){}[0]
-    final val synthesizeSubtreeRemoval // app.cash.redwood.protocol.guest/DefaultGuestProtocolAdapter.synthesizeSubtreeRemoval|{}synthesizeSubtreeRemoval[0]
-        final fun <get-synthesizeSubtreeRemoval>(): kotlin/Boolean // app.cash.redwood.protocol.guest/DefaultGuestProtocolAdapter.synthesizeSubtreeRemoval.<get-synthesizeSubtreeRemoval>|<get-synthesizeSubtreeRemoval>(){}[0]
     final val widgetSystem // app.cash.redwood.protocol.guest/DefaultGuestProtocolAdapter.widgetSystem|{}widgetSystem[0]
         final fun <get-widgetSystem>(): app.cash.redwood.widget/WidgetSystem<kotlin/Unit> // app.cash.redwood.protocol.guest/DefaultGuestProtocolAdapter.widgetSystem.<get-widgetSystem>|<get-widgetSystem>(){}[0]
 
@@ -91,7 +97,7 @@ final class app.cash.redwood.protocol.guest/ProtocolWidgetChildren : app.cash.re
     final val widgets // app.cash.redwood.protocol.guest/ProtocolWidgetChildren.widgets|{}widgets[0]
         final fun <get-widgets>(): kotlin.collections/List<app.cash.redwood.protocol.guest/ProtocolWidget> // app.cash.redwood.protocol.guest/ProtocolWidgetChildren.widgets.<get-widgets>|<get-widgets>(){}[0]
 
-    final fun depthFirstWalk(app.cash.redwood.protocol.guest/ProtocolWidget, kotlin/Function3<app.cash.redwood.protocol.guest/ProtocolWidget, app.cash.redwood.protocol/ChildrenTag, app.cash.redwood.protocol.guest/ProtocolWidgetChildren, kotlin/Unit>) // app.cash.redwood.protocol.guest/ProtocolWidgetChildren.depthFirstWalk|depthFirstWalk(app.cash.redwood.protocol.guest.ProtocolWidget;kotlin.Function3<app.cash.redwood.protocol.guest.ProtocolWidget,app.cash.redwood.protocol.ChildrenTag,app.cash.redwood.protocol.guest.ProtocolWidgetChildren,kotlin.Unit>){}[0]
+    final fun depthFirstWalk(app.cash.redwood.protocol.guest/ProtocolWidget, app.cash.redwood.protocol.guest/ProtocolWidget.ChildrenVisitor) // app.cash.redwood.protocol.guest/ProtocolWidgetChildren.depthFirstWalk|depthFirstWalk(app.cash.redwood.protocol.guest.ProtocolWidget;app.cash.redwood.protocol.guest.ProtocolWidget.ChildrenVisitor){}[0]
     final fun detach() // app.cash.redwood.protocol.guest/ProtocolWidgetChildren.detach|detach(){}[0]
     final fun insert(kotlin/Int, app.cash.redwood.widget/Widget<kotlin/Unit>) // app.cash.redwood.protocol.guest/ProtocolWidgetChildren.insert|insert(kotlin.Int;app.cash.redwood.widget.Widget<kotlin.Unit>){}[0]
     final fun move(kotlin/Int, kotlin/Int, kotlin/Int) // app.cash.redwood.protocol.guest/ProtocolWidgetChildren.move|move(kotlin.Int;kotlin.Int;kotlin.Int){}[0]
@@ -100,10 +106,12 @@ final class app.cash.redwood.protocol.guest/ProtocolWidgetChildren : app.cash.re
 }
 
 final val app.cash.redwood.protocol.guest/app_cash_redwood_protocol_guest_DefaultGuestProtocolAdapter$stableprop // app.cash.redwood.protocol.guest/app_cash_redwood_protocol_guest_DefaultGuestProtocolAdapter$stableprop|#static{}app_cash_redwood_protocol_guest_DefaultGuestProtocolAdapter$stableprop[0]
+final val app.cash.redwood.protocol.guest/app_cash_redwood_protocol_guest_GuestProtocolAdapter$stableprop // app.cash.redwood.protocol.guest/app_cash_redwood_protocol_guest_GuestProtocolAdapter$stableprop|#static{}app_cash_redwood_protocol_guest_GuestProtocolAdapter$stableprop[0]
 final val app.cash.redwood.protocol.guest/app_cash_redwood_protocol_guest_ProtocolWidgetChildren$stableprop // app.cash.redwood.protocol.guest/app_cash_redwood_protocol_guest_ProtocolWidgetChildren$stableprop|#static{}app_cash_redwood_protocol_guest_ProtocolWidgetChildren$stableprop[0]
 final val app.cash.redwood.protocol.guest/guestRedwoodVersion // app.cash.redwood.protocol.guest/guestRedwoodVersion|{}guestRedwoodVersion[0]
     final fun <get-guestRedwoodVersion>(): app.cash.redwood.protocol/RedwoodVersion // app.cash.redwood.protocol.guest/guestRedwoodVersion.<get-guestRedwoodVersion>|<get-guestRedwoodVersion>(){}[0]
 
 final fun app.cash.redwood.protocol.guest/ProtocolRedwoodComposition(kotlinx.coroutines/CoroutineScope, app.cash.redwood.protocol.guest/GuestProtocolAdapter, kotlin/UInt, app.cash.redwood.ui/OnBackPressedDispatcher, androidx.compose.runtime.saveable/SaveableStateRegistry?, kotlinx.coroutines.flow/StateFlow<app.cash.redwood.ui/UiConfiguration>, kotlin/Function0<kotlin/Unit> = ...): app.cash.redwood.compose/RedwoodComposition // app.cash.redwood.protocol.guest/ProtocolRedwoodComposition|ProtocolRedwoodComposition(kotlinx.coroutines.CoroutineScope;app.cash.redwood.protocol.guest.GuestProtocolAdapter;kotlin.UInt;app.cash.redwood.ui.OnBackPressedDispatcher;androidx.compose.runtime.saveable.SaveableStateRegistry?;kotlinx.coroutines.flow.StateFlow<app.cash.redwood.ui.UiConfiguration>;kotlin.Function0<kotlin.Unit>){}[0]
 final fun app.cash.redwood.protocol.guest/app_cash_redwood_protocol_guest_DefaultGuestProtocolAdapter$stableprop_getter(): kotlin/Int // app.cash.redwood.protocol.guest/app_cash_redwood_protocol_guest_DefaultGuestProtocolAdapter$stableprop_getter|app_cash_redwood_protocol_guest_DefaultGuestProtocolAdapter$stableprop_getter(){}[0]
+final fun app.cash.redwood.protocol.guest/app_cash_redwood_protocol_guest_GuestProtocolAdapter$stableprop_getter(): kotlin/Int // app.cash.redwood.protocol.guest/app_cash_redwood_protocol_guest_GuestProtocolAdapter$stableprop_getter|app_cash_redwood_protocol_guest_GuestProtocolAdapter$stableprop_getter(){}[0]
 final fun app.cash.redwood.protocol.guest/app_cash_redwood_protocol_guest_ProtocolWidgetChildren$stableprop_getter(): kotlin/Int // app.cash.redwood.protocol.guest/app_cash_redwood_protocol_guest_ProtocolWidgetChildren$stableprop_getter|app_cash_redwood_protocol_guest_ProtocolWidgetChildren$stableprop_getter(){}[0]
diff --git a/redwood-protocol-guest/src/commonMain/kotlin/app/cash/redwood/protocol/guest/DefaultGuestProtocolAdapter.kt b/redwood-protocol-guest/src/commonMain/kotlin/app/cash/redwood/protocol/guest/DefaultGuestProtocolAdapter.kt
index a5c5b70ced..022e28d004 100644
--- a/redwood-protocol-guest/src/commonMain/kotlin/app/cash/redwood/protocol/guest/DefaultGuestProtocolAdapter.kt
+++ b/redwood-protocol-guest/src/commonMain/kotlin/app/cash/redwood/protocol/guest/DefaultGuestProtocolAdapter.kt
@@ -44,7 +44,7 @@ public class DefaultGuestProtocolAdapter(
   hostVersion: RedwoodVersion,
   private val widgetSystemFactory: ProtocolWidgetSystemFactory,
   private val mismatchHandler: ProtocolMismatchHandler = ProtocolMismatchHandler.Throwing,
-) : GuestProtocolAdapter {
+) : GuestProtocolAdapter(hostVersion) {
   private var nextValue = Id.Root.value + 1
   private val widgets = mutableMapOf<Int, ProtocolWidget>()
   private val changes = mutableListOf<Change>()
@@ -56,8 +56,6 @@ public class DefaultGuestProtocolAdapter(
   public override val root: Widget.Children<Unit> =
     ProtocolWidgetChildren(Id.Root, ChildrenTag.Root, this)
 
-  public override val synthesizeSubtreeRemoval: Boolean = hostVersion < RedwoodVersion("0.10.0-SNAPSHOT")
-
   override fun sendEvent(event: Event) {
     val node = widgets[event.id.value]
     if (node != null) {
diff --git a/redwood-protocol-guest/src/commonMain/kotlin/app/cash/redwood/protocol/guest/GuestProtocolAdapter.kt b/redwood-protocol-guest/src/commonMain/kotlin/app/cash/redwood/protocol/guest/GuestProtocolAdapter.kt
index 40300dbda1..7f76c8f3fb 100644
--- a/redwood-protocol-guest/src/commonMain/kotlin/app/cash/redwood/protocol/guest/GuestProtocolAdapter.kt
+++ b/redwood-protocol-guest/src/commonMain/kotlin/app/cash/redwood/protocol/guest/GuestProtocolAdapter.kt
@@ -22,6 +22,7 @@ import app.cash.redwood.protocol.ChildrenTag
 import app.cash.redwood.protocol.EventSink
 import app.cash.redwood.protocol.Id
 import app.cash.redwood.protocol.PropertyTag
+import app.cash.redwood.protocol.RedwoodVersion
 import app.cash.redwood.protocol.WidgetTag
 import app.cash.redwood.widget.Widget
 import app.cash.redwood.widget.WidgetSystem
@@ -36,9 +37,11 @@ import kotlinx.serialization.json.Json
  *
  * This interface is for generated code use only.
  */
-public interface GuestProtocolAdapter : EventSink {
+public abstract class GuestProtocolAdapter(
+  hostVersion: RedwoodVersion,
+) : EventSink {
   @RedwoodCodegenApi
-  public val json: Json
+  public abstract val json: Json
 
   /**
    * Host versions prior to 0.10.0 contained a bug where they did not recursively remove widgets
@@ -46,36 +49,36 @@ public interface GuestProtocolAdapter : EventSink {
    * on the guest side by synthesizing removes for every node in the subtree.
    */
   @RedwoodCodegenApi
-  public val synthesizeSubtreeRemoval: Boolean
+  public val synthesizeSubtreeRemoval: Boolean = hostVersion < RedwoodVersion("0.10.0-SNAPSHOT")
 
   /**
    * The provider of factories of widgets which record property changes and whose children changes
    * are also recorded. You **must** attach returned widgets to [root] or the children of a widget
    * in the tree beneath [root] in order for it to be tracked.
    */
-  public val widgetSystem: WidgetSystem<Unit>
+  public abstract val widgetSystem: WidgetSystem<Unit>
 
   /**
    * The root of the widget tree onto which [widgetSystem]-produced widgets can be added. Changes to
    * this instance are recorded as changes to [Id.Root] and [ChildrenTag.Root].
    */
-  public val root: Widget.Children<Unit>
+  public abstract val root: Widget.Children<Unit>
 
-  public fun initChangesSink(changesSink: ChangesSink)
+  public abstract fun initChangesSink(changesSink: ChangesSink)
 
-  public fun emitChanges()
+  public abstract fun emitChanges()
 
   @RedwoodCodegenApi
-  public fun nextId(): Id
+  public abstract fun nextId(): Id
 
   @RedwoodCodegenApi
-  public fun appendCreate(
+  public abstract fun appendCreate(
     id: Id,
     tag: WidgetTag,
   )
 
   @RedwoodCodegenApi
-  public fun <T> appendPropertyChange(
+  public abstract fun <T> appendPropertyChange(
     id: Id,
     tag: PropertyTag,
     serializer: KSerializer<T>,
@@ -83,7 +86,7 @@ public interface GuestProtocolAdapter : EventSink {
   )
 
   @RedwoodCodegenApi
-  public fun appendPropertyChange(
+  public abstract fun appendPropertyChange(
     id: Id,
     tag: PropertyTag,
     value: Boolean,
@@ -97,20 +100,20 @@ public interface GuestProtocolAdapter : EventSink {
    * https://github.com/Kotlin/kotlinx.serialization/issues/2713
    */
   @RedwoodCodegenApi
-  public fun appendPropertyChange(
+  public abstract fun appendPropertyChange(
     id: Id,
     tag: PropertyTag,
     value: UInt,
   )
 
   @RedwoodCodegenApi
-  public fun appendModifierChange(
+  public abstract fun appendModifierChange(
     id: Id,
     value: Modifier,
   )
 
   @RedwoodCodegenApi
-  public fun appendAdd(
+  public abstract fun appendAdd(
     id: Id,
     tag: ChildrenTag,
     index: Int,
@@ -118,7 +121,7 @@ public interface GuestProtocolAdapter : EventSink {
   )
 
   @RedwoodCodegenApi
-  public fun appendMove(
+  public abstract fun appendMove(
     id: Id,
     tag: ChildrenTag,
     fromIndex: Int,
@@ -127,14 +130,44 @@ public interface GuestProtocolAdapter : EventSink {
   )
 
   @RedwoodCodegenApi
-  public fun appendRemove(
+  public abstract fun appendRemove(
     id: Id,
     tag: ChildrenTag,
     index: Int,
     count: Int,
-    removedIds: List<Id> = listOf(),
+    removedIds: List<Id>,
   )
 
   @RedwoodCodegenApi
-  public fun removeWidget(id: Id)
+  public abstract fun removeWidget(id: Id)
+
+  @RedwoodCodegenApi
+  public val childrenVisitor: ProtocolWidget.ChildrenVisitor = if (synthesizeSubtreeRemoval) {
+    object : ProtocolWidget.ChildrenVisitor {
+      override fun visit(
+        parent: ProtocolWidget,
+        childrenTag: ChildrenTag,
+        children: ProtocolWidgetChildren,
+      ) {
+        // This boxes Id values. Don't bother optimizing since it only serves very old hosts.
+        val childIds = children.widgets.map(ProtocolWidget::id)
+        for (childId in childIds) {
+          removeWidget(childId)
+        }
+        appendRemove(parent.id, childrenTag, 0, childIds.size, childIds)
+      }
+    }
+  } else {
+    object : ProtocolWidget.ChildrenVisitor {
+      override fun visit(
+        parent: ProtocolWidget,
+        childrenTag: ChildrenTag,
+        children: ProtocolWidgetChildren,
+      ) {
+        for (childWidget in children.widgets) {
+          removeWidget(childWidget.id)
+        }
+      }
+    }
+  }
 }
diff --git a/redwood-protocol-guest/src/commonMain/kotlin/app/cash/redwood/protocol/guest/ProtocolWidget.kt b/redwood-protocol-guest/src/commonMain/kotlin/app/cash/redwood/protocol/guest/ProtocolWidget.kt
index eae496ceb5..e3c51ab756 100644
--- a/redwood-protocol-guest/src/commonMain/kotlin/app/cash/redwood/protocol/guest/ProtocolWidget.kt
+++ b/redwood-protocol-guest/src/commonMain/kotlin/app/cash/redwood/protocol/guest/ProtocolWidget.kt
@@ -57,17 +57,19 @@ public interface ProtocolWidget : Widget<Unit> {
    *   }
    * }
    * ```
-   * You will see the following argument values passed to [block] if invoked on the `Split`:
+   * You will see the following argument values passed to [visitor] if invoked on the `Split`:
    * 1. parent: `Row`, childrenTag: 1, children: `[Text+Button]`
    * 2. parent: `Split`, childrenTag: 1, children: `[Row]`
    * 3. parent: `Column`, childrenTag: 1, children: `[Button+Text]`
    * 4. parent: `Split`, childrenTag: 2, children: `[Column]`
    */
-  public fun depthFirstWalk(
-    block: (
+  public fun depthFirstWalk(visitor: ChildrenVisitor)
+
+  public fun interface ChildrenVisitor {
+    public fun visit(
       parent: ProtocolWidget,
       childrenTag: ChildrenTag,
       children: ProtocolWidgetChildren,
-    ) -> Unit,
-  )
+    )
+  }
 }
diff --git a/redwood-protocol-guest/src/commonMain/kotlin/app/cash/redwood/protocol/guest/ProtocolWidgetChildren.kt b/redwood-protocol-guest/src/commonMain/kotlin/app/cash/redwood/protocol/guest/ProtocolWidgetChildren.kt
index 8ebb49809b..8c9432679e 100644
--- a/redwood-protocol-guest/src/commonMain/kotlin/app/cash/redwood/protocol/guest/ProtocolWidgetChildren.kt
+++ b/redwood-protocol-guest/src/commonMain/kotlin/app/cash/redwood/protocol/guest/ProtocolWidgetChildren.kt
@@ -38,32 +38,23 @@ public class ProtocolWidgetChildren(
 
   override fun remove(index: Int, count: Int) {
     if (guestAdapter.synthesizeSubtreeRemoval) {
+      // This boxes Id values. Don't bother optimizing since it only serves very old hosts.
       val removedIds = ArrayList<Id>(count)
       for (i in index until index + count) {
         val widget = _widgets[i]
         removedIds += widget.id
         guestAdapter.removeWidget(widget.id)
 
-        widget.depthFirstWalk { parent, childrenTag, children ->
-          val childIds = children.widgets.map(ProtocolWidget::id)
-          for (childId in childIds) {
-            guestAdapter.removeWidget(childId)
-          }
-          guestAdapter.appendRemove(parent.id, childrenTag, 0, childIds.size, childIds)
-        }
+        widget.depthFirstWalk(guestAdapter.childrenVisitor)
       }
       guestAdapter.appendRemove(id, tag, index, count, removedIds)
     } else {
       for (i in index until index + count) {
         val widget = _widgets[i]
         guestAdapter.removeWidget(widget.id)
-        widget.depthFirstWalk { _, _, children ->
-          for (childWidget in children.widgets) {
-            guestAdapter.removeWidget(childWidget.id)
-          }
-        }
+        widget.depthFirstWalk(guestAdapter.childrenVisitor)
       }
-      guestAdapter.appendRemove(id, tag, index, count)
+      guestAdapter.appendRemove(id, tag, index, count, emptyList())
     }
 
     _widgets.remove(index, count)
@@ -79,12 +70,12 @@ public class ProtocolWidgetChildren(
 
   public fun depthFirstWalk(
     parent: ProtocolWidget,
-    block: (ProtocolWidget, ChildrenTag, ProtocolWidgetChildren) -> Unit,
+    visitor: ProtocolWidget.ChildrenVisitor,
   ) {
     for (widget in widgets) {
-      widget.depthFirstWalk(block)
+      widget.depthFirstWalk(visitor)
     }
-    block(parent, tag, this)
+    visitor.visit(parent, tag, this)
   }
 
   override fun detach() {
diff --git a/redwood-protocol/api/redwood-protocol.api b/redwood-protocol/api/redwood-protocol.api
index 2a01e7f9a5..1f835c9bc7 100644
--- a/redwood-protocol/api/redwood-protocol.api
+++ b/redwood-protocol/api/redwood-protocol.api
@@ -40,6 +40,7 @@ public synthetic class app/cash/redwood/protocol/ChildrenChange$Add$$serializer
 }
 
 public final class app/cash/redwood/protocol/ChildrenChange$Add$Companion {
+	public final fun invoke-11bgaWM (IIII)Lapp/cash/redwood/protocol/ChildrenChange$Add;
 	public final fun serializer ()Lkotlinx/serialization/KSerializer;
 }
 
@@ -72,12 +73,12 @@ public synthetic class app/cash/redwood/protocol/ChildrenChange$Move$$serializer
 }
 
 public final class app/cash/redwood/protocol/ChildrenChange$Move$Companion {
+	public final fun invoke-HpxY78w (IIIII)Lapp/cash/redwood/protocol/ChildrenChange$Move;
 	public final fun serializer ()Lkotlinx/serialization/KSerializer;
 }
 
 public final class app/cash/redwood/protocol/ChildrenChange$Remove : app/cash/redwood/protocol/ChildrenChange {
 	public static final field Companion Lapp/cash/redwood/protocol/ChildrenChange$Remove$Companion;
-	public synthetic fun <init> (IIIILjava/util/List;ILkotlin/jvm/internal/DefaultConstructorMarker;)V
 	public synthetic fun <init> (IIIILjava/util/List;Lkotlin/jvm/internal/DefaultConstructorMarker;)V
 	public fun equals (Ljava/lang/Object;)Z
 	public final fun getCount ()I
@@ -101,6 +102,8 @@ public synthetic class app/cash/redwood/protocol/ChildrenChange$Remove$$serializ
 }
 
 public final class app/cash/redwood/protocol/ChildrenChange$Remove$Companion {
+	public final fun invoke-HpxY78w (IIIILjava/util/List;)Lapp/cash/redwood/protocol/ChildrenChange$Remove;
+	public static synthetic fun invoke-HpxY78w$default (Lapp/cash/redwood/protocol/ChildrenChange$Remove$Companion;IIIILjava/util/List;ILjava/lang/Object;)Lapp/cash/redwood/protocol/ChildrenChange$Remove;
 	public final fun serializer ()Lkotlinx/serialization/KSerializer;
 }
 
@@ -157,12 +160,12 @@ public synthetic class app/cash/redwood/protocol/Create$$serializer : kotlinx/se
 }
 
 public final class app/cash/redwood/protocol/Create$Companion {
+	public final fun invoke-kyz2zXs (II)Lapp/cash/redwood/protocol/Create;
 	public final fun serializer ()Lkotlinx/serialization/KSerializer;
 }
 
 public final class app/cash/redwood/protocol/Event {
 	public static final field Companion Lapp/cash/redwood/protocol/Event$Companion;
-	public synthetic fun <init> (IILjava/util/List;ILkotlin/jvm/internal/DefaultConstructorMarker;)V
 	public synthetic fun <init> (IILjava/util/List;Lkotlin/jvm/internal/DefaultConstructorMarker;)V
 	public fun equals (Ljava/lang/Object;)Z
 	public final fun getArgs ()Ljava/util/List;
@@ -184,6 +187,8 @@ public synthetic class app/cash/redwood/protocol/Event$$serializer : kotlinx/ser
 }
 
 public final class app/cash/redwood/protocol/Event$Companion {
+	public final fun invoke-OtSvs1c (IILjava/util/List;)Lapp/cash/redwood/protocol/Event;
+	public static synthetic fun invoke-OtSvs1c$default (Lapp/cash/redwood/protocol/Event$Companion;IILjava/util/List;ILjava/lang/Object;)Lapp/cash/redwood/protocol/Event;
 	public final fun serializer ()Lkotlinx/serialization/KSerializer;
 }
 
@@ -254,7 +259,6 @@ public final class app/cash/redwood/protocol/Id$Companion {
 
 public final class app/cash/redwood/protocol/ModifierChange : app/cash/redwood/protocol/ValueChange {
 	public static final field Companion Lapp/cash/redwood/protocol/ModifierChange$Companion;
-	public synthetic fun <init> (ILjava/util/List;ILkotlin/jvm/internal/DefaultConstructorMarker;)V
 	public synthetic fun <init> (ILjava/util/List;Lkotlin/jvm/internal/DefaultConstructorMarker;)V
 	public fun equals (Ljava/lang/Object;)Z
 	public final fun getElements ()Ljava/util/List;
@@ -275,6 +279,8 @@ public synthetic class app/cash/redwood/protocol/ModifierChange$$serializer : ko
 }
 
 public final class app/cash/redwood/protocol/ModifierChange$Companion {
+	public final fun invoke-z3jyS0k (ILjava/util/List;)Lapp/cash/redwood/protocol/ModifierChange;
+	public static synthetic fun invoke-z3jyS0k$default (Lapp/cash/redwood/protocol/ModifierChange$Companion;ILjava/util/List;ILjava/lang/Object;)Lapp/cash/redwood/protocol/ModifierChange;
 	public final fun serializer ()Lkotlinx/serialization/KSerializer;
 }
 
@@ -320,7 +326,6 @@ public final class app/cash/redwood/protocol/ModifierTag$Companion {
 
 public final class app/cash/redwood/protocol/PropertyChange : app/cash/redwood/protocol/ValueChange {
 	public static final field Companion Lapp/cash/redwood/protocol/PropertyChange$Companion;
-	public synthetic fun <init> (IILkotlinx/serialization/json/JsonElement;ILkotlin/jvm/internal/DefaultConstructorMarker;)V
 	public synthetic fun <init> (IILkotlinx/serialization/json/JsonElement;Lkotlin/jvm/internal/DefaultConstructorMarker;)V
 	public fun equals (Ljava/lang/Object;)Z
 	public fun getId-0HhLjSo ()I
@@ -342,6 +347,8 @@ public synthetic class app/cash/redwood/protocol/PropertyChange$$serializer : ko
 }
 
 public final class app/cash/redwood/protocol/PropertyChange$Companion {
+	public final fun invoke-e3iP1vo (IILkotlinx/serialization/json/JsonElement;)Lapp/cash/redwood/protocol/PropertyChange;
+	public static synthetic fun invoke-e3iP1vo$default (Lapp/cash/redwood/protocol/PropertyChange$Companion;IILkotlinx/serialization/json/JsonElement;ILjava/lang/Object;)Lapp/cash/redwood/protocol/PropertyChange;
 	public final fun serializer ()Lkotlinx/serialization/KSerializer;
 }
 
diff --git a/redwood-protocol/api/redwood-protocol.klib.api b/redwood-protocol/api/redwood-protocol.klib.api
index 9caf13558c..bb8f72c667 100644
--- a/redwood-protocol/api/redwood-protocol.klib.api
+++ b/redwood-protocol/api/redwood-protocol.klib.api
@@ -29,8 +29,6 @@ sealed interface app.cash.redwood.protocol/ChildrenChange : app.cash.redwood.pro
         abstract fun <get-tag>(): app.cash.redwood.protocol/ChildrenTag // app.cash.redwood.protocol/ChildrenChange.tag.<get-tag>|<get-tag>(){}[0]
 
     final class Add : app.cash.redwood.protocol/ChildrenChange { // app.cash.redwood.protocol/ChildrenChange.Add|null[0]
-        constructor <init>(app.cash.redwood.protocol/Id, app.cash.redwood.protocol/ChildrenTag, app.cash.redwood.protocol/Id, kotlin/Int) // app.cash.redwood.protocol/ChildrenChange.Add.<init>|<init>(app.cash.redwood.protocol.Id;app.cash.redwood.protocol.ChildrenTag;app.cash.redwood.protocol.Id;kotlin.Int){}[0]
-
         final val childId // app.cash.redwood.protocol/ChildrenChange.Add.childId|{}childId[0]
             final fun <get-childId>(): app.cash.redwood.protocol/Id // app.cash.redwood.protocol/ChildrenChange.Add.childId.<get-childId>|<get-childId>(){}[0]
         final val id // app.cash.redwood.protocol/ChildrenChange.Add.id|{}id[0]
@@ -54,13 +52,12 @@ sealed interface app.cash.redwood.protocol/ChildrenChange : app.cash.redwood.pro
         }
 
         final object Companion { // app.cash.redwood.protocol/ChildrenChange.Add.Companion|null[0]
+            final fun invoke(app.cash.redwood.protocol/Id, app.cash.redwood.protocol/ChildrenTag, app.cash.redwood.protocol/Id, kotlin/Int): app.cash.redwood.protocol/ChildrenChange.Add // app.cash.redwood.protocol/ChildrenChange.Add.Companion.invoke|invoke(app.cash.redwood.protocol.Id;app.cash.redwood.protocol.ChildrenTag;app.cash.redwood.protocol.Id;kotlin.Int){}[0]
             final fun serializer(): kotlinx.serialization/KSerializer<app.cash.redwood.protocol/ChildrenChange.Add> // app.cash.redwood.protocol/ChildrenChange.Add.Companion.serializer|serializer(){}[0]
         }
     }
 
     final class Move : app.cash.redwood.protocol/ChildrenChange { // app.cash.redwood.protocol/ChildrenChange.Move|null[0]
-        constructor <init>(app.cash.redwood.protocol/Id, app.cash.redwood.protocol/ChildrenTag, kotlin/Int, kotlin/Int, kotlin/Int) // app.cash.redwood.protocol/ChildrenChange.Move.<init>|<init>(app.cash.redwood.protocol.Id;app.cash.redwood.protocol.ChildrenTag;kotlin.Int;kotlin.Int;kotlin.Int){}[0]
-
         final val count // app.cash.redwood.protocol/ChildrenChange.Move.count|{}count[0]
             final fun <get-count>(): kotlin/Int // app.cash.redwood.protocol/ChildrenChange.Move.count.<get-count>|<get-count>(){}[0]
         final val fromIndex // app.cash.redwood.protocol/ChildrenChange.Move.fromIndex|{}fromIndex[0]
@@ -86,13 +83,12 @@ sealed interface app.cash.redwood.protocol/ChildrenChange : app.cash.redwood.pro
         }
 
         final object Companion { // app.cash.redwood.protocol/ChildrenChange.Move.Companion|null[0]
+            final fun invoke(app.cash.redwood.protocol/Id, app.cash.redwood.protocol/ChildrenTag, kotlin/Int, kotlin/Int, kotlin/Int): app.cash.redwood.protocol/ChildrenChange.Move // app.cash.redwood.protocol/ChildrenChange.Move.Companion.invoke|invoke(app.cash.redwood.protocol.Id;app.cash.redwood.protocol.ChildrenTag;kotlin.Int;kotlin.Int;kotlin.Int){}[0]
             final fun serializer(): kotlinx.serialization/KSerializer<app.cash.redwood.protocol/ChildrenChange.Move> // app.cash.redwood.protocol/ChildrenChange.Move.Companion.serializer|serializer(){}[0]
         }
     }
 
     final class Remove : app.cash.redwood.protocol/ChildrenChange { // app.cash.redwood.protocol/ChildrenChange.Remove|null[0]
-        constructor <init>(app.cash.redwood.protocol/Id, app.cash.redwood.protocol/ChildrenTag, kotlin/Int, kotlin/Int, kotlin.collections/List<app.cash.redwood.protocol/Id> = ...) // app.cash.redwood.protocol/ChildrenChange.Remove.<init>|<init>(app.cash.redwood.protocol.Id;app.cash.redwood.protocol.ChildrenTag;kotlin.Int;kotlin.Int;kotlin.collections.List<app.cash.redwood.protocol.Id>){}[0]
-
         final val count // app.cash.redwood.protocol/ChildrenChange.Remove.count|{}count[0]
             final fun <get-count>(): kotlin/Int // app.cash.redwood.protocol/ChildrenChange.Remove.count.<get-count>|<get-count>(){}[0]
         final val id // app.cash.redwood.protocol/ChildrenChange.Remove.id|{}id[0]
@@ -120,6 +116,7 @@ sealed interface app.cash.redwood.protocol/ChildrenChange : app.cash.redwood.pro
         final object Companion { // app.cash.redwood.protocol/ChildrenChange.Remove.Companion|null[0]
             final val $childSerializers // app.cash.redwood.protocol/ChildrenChange.Remove.Companion.$childSerializers|{}$childSerializers[0]
 
+            final fun invoke(app.cash.redwood.protocol/Id, app.cash.redwood.protocol/ChildrenTag, kotlin/Int, kotlin/Int, kotlin.collections/List<app.cash.redwood.protocol/Id> = ...): app.cash.redwood.protocol/ChildrenChange.Remove // app.cash.redwood.protocol/ChildrenChange.Remove.Companion.invoke|invoke(app.cash.redwood.protocol.Id;app.cash.redwood.protocol.ChildrenTag;kotlin.Int;kotlin.Int;kotlin.collections.List<app.cash.redwood.protocol.Id>){}[0]
             final fun serializer(): kotlinx.serialization/KSerializer<app.cash.redwood.protocol/ChildrenChange.Remove> // app.cash.redwood.protocol/ChildrenChange.Remove.Companion.serializer|serializer(){}[0]
         }
     }
@@ -133,8 +130,6 @@ sealed interface app.cash.redwood.protocol/ChildrenChange : app.cash.redwood.pro
 sealed interface app.cash.redwood.protocol/ValueChange : app.cash.redwood.protocol/Change // app.cash.redwood.protocol/ValueChange|null[0]
 
 final class app.cash.redwood.protocol/Create : app.cash.redwood.protocol/Change { // app.cash.redwood.protocol/Create|null[0]
-    constructor <init>(app.cash.redwood.protocol/Id, app.cash.redwood.protocol/WidgetTag) // app.cash.redwood.protocol/Create.<init>|<init>(app.cash.redwood.protocol.Id;app.cash.redwood.protocol.WidgetTag){}[0]
-
     final val id // app.cash.redwood.protocol/Create.id|{}id[0]
         final fun <get-id>(): app.cash.redwood.protocol/Id // app.cash.redwood.protocol/Create.id.<get-id>|<get-id>(){}[0]
     final val tag // app.cash.redwood.protocol/Create.tag|{}tag[0]
@@ -154,13 +149,12 @@ final class app.cash.redwood.protocol/Create : app.cash.redwood.protocol/Change
     }
 
     final object Companion { // app.cash.redwood.protocol/Create.Companion|null[0]
+        final fun invoke(app.cash.redwood.protocol/Id, app.cash.redwood.protocol/WidgetTag): app.cash.redwood.protocol/Create // app.cash.redwood.protocol/Create.Companion.invoke|invoke(app.cash.redwood.protocol.Id;app.cash.redwood.protocol.WidgetTag){}[0]
         final fun serializer(): kotlinx.serialization/KSerializer<app.cash.redwood.protocol/Create> // app.cash.redwood.protocol/Create.Companion.serializer|serializer(){}[0]
     }
 }
 
 final class app.cash.redwood.protocol/Event { // app.cash.redwood.protocol/Event|null[0]
-    constructor <init>(app.cash.redwood.protocol/Id, app.cash.redwood.protocol/EventTag, kotlin.collections/List<kotlinx.serialization.json/JsonElement> = ...) // app.cash.redwood.protocol/Event.<init>|<init>(app.cash.redwood.protocol.Id;app.cash.redwood.protocol.EventTag;kotlin.collections.List<kotlinx.serialization.json.JsonElement>){}[0]
-
     final val args // app.cash.redwood.protocol/Event.args|{}args[0]
         final fun <get-args>(): kotlin.collections/List<kotlinx.serialization.json/JsonElement> // app.cash.redwood.protocol/Event.args.<get-args>|<get-args>(){}[0]
     final val id // app.cash.redwood.protocol/Event.id|{}id[0]
@@ -184,13 +178,12 @@ final class app.cash.redwood.protocol/Event { // app.cash.redwood.protocol/Event
     final object Companion { // app.cash.redwood.protocol/Event.Companion|null[0]
         final val $childSerializers // app.cash.redwood.protocol/Event.Companion.$childSerializers|{}$childSerializers[0]
 
+        final fun invoke(app.cash.redwood.protocol/Id, app.cash.redwood.protocol/EventTag, kotlin.collections/List<kotlinx.serialization.json/JsonElement> = ...): app.cash.redwood.protocol/Event // app.cash.redwood.protocol/Event.Companion.invoke|invoke(app.cash.redwood.protocol.Id;app.cash.redwood.protocol.EventTag;kotlin.collections.List<kotlinx.serialization.json.JsonElement>){}[0]
         final fun serializer(): kotlinx.serialization/KSerializer<app.cash.redwood.protocol/Event> // app.cash.redwood.protocol/Event.Companion.serializer|serializer(){}[0]
     }
 }
 
 final class app.cash.redwood.protocol/ModifierChange : app.cash.redwood.protocol/ValueChange { // app.cash.redwood.protocol/ModifierChange|null[0]
-    constructor <init>(app.cash.redwood.protocol/Id, kotlin.collections/List<app.cash.redwood.protocol/ModifierElement> = ...) // app.cash.redwood.protocol/ModifierChange.<init>|<init>(app.cash.redwood.protocol.Id;kotlin.collections.List<app.cash.redwood.protocol.ModifierElement>){}[0]
-
     final val elements // app.cash.redwood.protocol/ModifierChange.elements|{}elements[0]
         final fun <get-elements>(): kotlin.collections/List<app.cash.redwood.protocol/ModifierElement> // app.cash.redwood.protocol/ModifierChange.elements.<get-elements>|<get-elements>(){}[0]
     final val id // app.cash.redwood.protocol/ModifierChange.id|{}id[0]
@@ -212,6 +205,7 @@ final class app.cash.redwood.protocol/ModifierChange : app.cash.redwood.protocol
     final object Companion { // app.cash.redwood.protocol/ModifierChange.Companion|null[0]
         final val $childSerializers // app.cash.redwood.protocol/ModifierChange.Companion.$childSerializers|{}$childSerializers[0]
 
+        final fun invoke(app.cash.redwood.protocol/Id, kotlin.collections/List<app.cash.redwood.protocol/ModifierElement> = ...): app.cash.redwood.protocol/ModifierChange // app.cash.redwood.protocol/ModifierChange.Companion.invoke|invoke(app.cash.redwood.protocol.Id;kotlin.collections.List<app.cash.redwood.protocol.ModifierElement>){}[0]
         final fun serializer(): kotlinx.serialization/KSerializer<app.cash.redwood.protocol/ModifierChange> // app.cash.redwood.protocol/ModifierChange.Companion.serializer|serializer(){}[0]
     }
 }
@@ -230,8 +224,6 @@ final class app.cash.redwood.protocol/ModifierElement { // app.cash.redwood.prot
 }
 
 final class app.cash.redwood.protocol/PropertyChange : app.cash.redwood.protocol/ValueChange { // app.cash.redwood.protocol/PropertyChange|null[0]
-    constructor <init>(app.cash.redwood.protocol/Id, app.cash.redwood.protocol/PropertyTag, kotlinx.serialization.json/JsonElement = ...) // app.cash.redwood.protocol/PropertyChange.<init>|<init>(app.cash.redwood.protocol.Id;app.cash.redwood.protocol.PropertyTag;kotlinx.serialization.json.JsonElement){}[0]
-
     final val id // app.cash.redwood.protocol/PropertyChange.id|{}id[0]
         final fun <get-id>(): app.cash.redwood.protocol/Id // app.cash.redwood.protocol/PropertyChange.id.<get-id>|<get-id>(){}[0]
     final val tag // app.cash.redwood.protocol/PropertyChange.tag|{}tag[0]
@@ -253,6 +245,7 @@ final class app.cash.redwood.protocol/PropertyChange : app.cash.redwood.protocol
     }
 
     final object Companion { // app.cash.redwood.protocol/PropertyChange.Companion|null[0]
+        final fun invoke(app.cash.redwood.protocol/Id, app.cash.redwood.protocol/PropertyTag, kotlinx.serialization.json/JsonElement = ...): app.cash.redwood.protocol/PropertyChange // app.cash.redwood.protocol/PropertyChange.Companion.invoke|invoke(app.cash.redwood.protocol.Id;app.cash.redwood.protocol.PropertyTag;kotlinx.serialization.json.JsonElement){}[0]
         final fun serializer(): kotlinx.serialization/KSerializer<app.cash.redwood.protocol/PropertyChange> // app.cash.redwood.protocol/PropertyChange.Companion.serializer|serializer(){}[0]
     }
 }
diff --git a/redwood-protocol/src/commonMain/kotlin/app/cash/redwood/protocol/protocol.kt b/redwood-protocol/src/commonMain/kotlin/app/cash/redwood/protocol/protocol.kt
index 062ba276ad..a9ed1836de 100644
--- a/redwood-protocol/src/commonMain/kotlin/app/cash/redwood/protocol/protocol.kt
+++ b/redwood-protocol/src/commonMain/kotlin/app/cash/redwood/protocol/protocol.kt
@@ -33,15 +33,35 @@ import kotlinx.serialization.json.buildJsonArray
 import kotlinx.serialization.json.jsonArray
 import kotlinx.serialization.json.jsonPrimitive
 
+/*
+Note: The types in this file are written in a careful way such that their serializable properties
+are scalars which can be serialized directly rather than using value classes are boxed within the
+generated kotlinx.serialization code.
+*/
+
 @Serializable
 @Poko
-public class Event(
+public class Event private constructor(
+  @SerialName("id")
+  private val _id: Int,
+  @SerialName("tag")
+  private val _tag: Int,
+  public val args: List<JsonElement> = emptyList(),
+) {
   /** Identifier for the widget from which this event originated. */
-  public val id: Id,
+  public val id: Id get() = Id(_id)
+
   /** Identifies which event occurred on the widget with [id]. */
-  public val tag: EventTag,
-  public val args: List<JsonElement> = emptyList(),
-)
+  public val tag: EventTag get() = EventTag(_tag)
+
+  public companion object {
+    public operator fun invoke(
+      id: Id,
+      tag: EventTag,
+      args: List<JsonElement> = emptyList(),
+    ): Event = Event(id.value, tag.value, args)
+  }
+}
 
 @Serializable
 public sealed interface Change {
@@ -52,30 +72,67 @@ public sealed interface Change {
 @Serializable
 @SerialName("create")
 @Poko
-public class Create(
-  override val id: Id,
-  public val tag: WidgetTag,
-) : Change
+public class Create private constructor(
+  @SerialName("id")
+  private val _id: Int,
+  @SerialName("tag")
+  private val _tag: Int,
+) : Change {
+  override val id: Id get() = Id(_id)
+  public val tag: WidgetTag get() = WidgetTag(_tag)
+
+  public companion object {
+    public operator fun invoke(
+      id: Id,
+      tag: WidgetTag,
+    ): Create = Create(id.value, tag.value)
+  }
+}
 
 public sealed interface ValueChange : Change
 
 @Serializable
 @SerialName("property")
 @Poko
-public class PropertyChange(
-  override val id: Id,
-  /** Identifies which property changed on the widget with [id]. */
-  public val tag: PropertyTag,
+public class PropertyChange private constructor(
+  @SerialName("id")
+  private val _id: Int,
+  @SerialName("tag")
+  private val _tag: Int,
   public val value: JsonElement = JsonNull,
-) : ValueChange
+) : ValueChange {
+  override val id: Id get() = Id(_id)
+
+  /** Identifies which property changed on the widget with [id]. */
+  public val tag: PropertyTag get() = PropertyTag(_tag)
+
+  public companion object {
+    public operator fun invoke(
+      id: Id,
+      /** Identifies which property changed on the widget with [id]. */
+      tag: PropertyTag,
+      value: JsonElement = JsonNull,
+    ): PropertyChange = PropertyChange(id.value, tag.value, value)
+  }
+}
 
 @Serializable
 @SerialName("modifier")
 @Poko
-public class ModifierChange(
-  override val id: Id,
+public class ModifierChange private constructor(
+  @SerialName("id")
+  private val _id: Int,
   public val elements: List<ModifierElement> = emptyList(),
-) : ValueChange
+) : ValueChange {
+  override val id: Id get() = Id(_id)
+
+  public companion object {
+    public operator fun invoke(
+      id: Id,
+      elements: List<ModifierElement> = emptyList(),
+    ): ModifierChange = ModifierChange(id.value, elements)
+  }
+}
 
 @Serializable(with = ModifierElementSerializer::class)
 @Poko
@@ -126,34 +183,80 @@ public sealed interface ChildrenChange : Change {
   @Serializable
   @SerialName("add")
   @Poko
-  public class Add(
-    override val id: Id,
-    override val tag: ChildrenTag,
-    public val childId: Id,
+  public class Add private constructor(
+    @SerialName("id")
+    private val _id: Int,
+    @SerialName("tag")
+    private val _tag: Int,
+    @SerialName("childId")
+    private val _childId: Int,
     public val index: Int,
-  ) : ChildrenChange
+  ) : ChildrenChange {
+    override val id: Id get() = Id(_id)
+    override val tag: ChildrenTag get() = ChildrenTag(_tag)
+    public val childId: Id get() = Id(_childId)
+
+    public companion object {
+      public operator fun invoke(
+        id: Id,
+        tag: ChildrenTag,
+        childId: Id,
+        index: Int,
+      ): Add = Add(id.value, tag.value, childId.value, index)
+    }
+  }
 
   @Serializable
   @SerialName("move")
   @Poko
-  public class Move(
-    override val id: Id,
-    override val tag: ChildrenTag,
+  public class Move private constructor(
+    @SerialName("id")
+    private val _id: Int,
+    @SerialName("tag")
+    private val _tag: Int,
     public val fromIndex: Int,
     public val toIndex: Int,
     public val count: Int,
-  ) : ChildrenChange
+  ) : ChildrenChange {
+    override val id: Id get() = Id(_id)
+    override val tag: ChildrenTag get() = ChildrenTag(_tag)
+
+    public companion object {
+      public operator fun invoke(
+        id: Id,
+        tag: ChildrenTag,
+        fromIndex: Int,
+        toIndex: Int,
+        count: Int,
+      ): Move = Move(id.value, tag.value, fromIndex, toIndex, count)
+    }
+  }
 
   @Serializable
   @SerialName("remove")
   @Poko
-  public class Remove(
-    override val id: Id,
-    override val tag: ChildrenTag,
+  public class Remove private constructor(
+    @SerialName("id")
+    private val _id: Int,
+    @SerialName("tag")
+    private val _tag: Int,
     public val index: Int,
     public val count: Int,
     // TODO Remove this for Redwood 1.0.0.
     @Deprecated("Only sent for compatibility with old hosts. Do not consume.", level = ERROR)
     public val removedIds: List<Id> = emptyList(),
-  ) : ChildrenChange
+  ) : ChildrenChange {
+    override val id: Id get() = Id(_id)
+    override val tag: ChildrenTag get() = ChildrenTag(_tag)
+
+    public companion object {
+      public operator fun invoke(
+        id: Id,
+        tag: ChildrenTag,
+        index: Int,
+        count: Int,
+        removedIds: List<Id> = emptyList(),
+      ): Remove = Remove(id.value, tag.value, index, count, removedIds)
+    }
+  }
 }
diff --git a/redwood-protocol/src/commonTest/kotlin/app/cash/redwood/protocol/SnapshotChangeListTest.kt b/redwood-protocol/src/commonTest/kotlin/app/cash/redwood/protocol/SnapshotChangeListTest.kt
index 8bdcf34b2b..be853ddde7 100644
--- a/redwood-protocol/src/commonTest/kotlin/app/cash/redwood/protocol/SnapshotChangeListTest.kt
+++ b/redwood-protocol/src/commonTest/kotlin/app/cash/redwood/protocol/SnapshotChangeListTest.kt
@@ -70,8 +70,8 @@ class SnapshotChangeListTest {
       |Snapshot change list cannot contain move or remove operations
       |
       |Found:
-      | - Move(id=Id(value=0), tag=ChildrenTag(value=1), fromIndex=1, toIndex=2, count=3)
-      | - Remove(id=Id(value=0), tag=ChildrenTag(value=1), index=1, count=2, removedIds=[Id(value=3), Id(value=4)])
+      | - Move(_id=0, _tag=1, fromIndex=1, toIndex=2, count=3)
+      | - Remove(_id=0, _tag=1, index=1, count=2, removedIds=[Id(value=3), Id(value=4)])
       """.trimMargin(),
     )
   }
diff --git a/redwood-tooling-codegen/src/main/kotlin/app/cash/redwood/tooling/codegen/protocolGuestGeneration.kt b/redwood-tooling-codegen/src/main/kotlin/app/cash/redwood/tooling/codegen/protocolGuestGeneration.kt
index 17413cdac9..7342a6d658 100644
--- a/redwood-tooling-codegen/src/main/kotlin/app/cash/redwood/tooling/codegen/protocolGuestGeneration.kt
+++ b/redwood-tooling-codegen/src/main/kotlin/app/cash/redwood/tooling/codegen/protocolGuestGeneration.kt
@@ -40,7 +40,6 @@ import com.squareup.kotlinpoet.KModifier.OVERRIDE
 import com.squareup.kotlinpoet.KModifier.PRIVATE
 import com.squareup.kotlinpoet.KModifier.PUBLIC
 import com.squareup.kotlinpoet.LONG
-import com.squareup.kotlinpoet.LambdaTypeName
 import com.squareup.kotlinpoet.MemberName
 import com.squareup.kotlinpoet.ParameterizedTypeName.Companion.parameterizedBy
 import com.squareup.kotlinpoet.PropertySpec
@@ -429,26 +428,17 @@ internal fun generateProtocolWidget(
         .addFunction(
           FunSpec.builder("depthFirstWalk")
             .addModifiers(OVERRIDE)
-            .addParameter(
-              "block",
-              LambdaTypeName.get(
-                null,
-                ProtocolGuest.ProtocolWidget,
-                Protocol.ChildrenTag,
-                ProtocolGuest.ProtocolWidgetChildren,
-                returnType = UNIT,
-              ),
-            )
+            .addParameter("visitor", ProtocolGuest.ProtocolWidgetChildrenVisitor)
             .apply {
               for (trait in widget.traits) {
                 if (trait is ProtocolChildren) {
                   if (workAroundLazyListPlaceholderRemoveCrash(widget, trait)) {
                     addComment("Work around the LazyList.placeholder remove crash.")
                     beginControlFlow("if (!guestAdapter.synthesizeSubtreeRemoval)")
-                    addStatement("%N.depthFirstWalk(this, block)", trait.name)
+                    addStatement("%N.depthFirstWalk(this, visitor)", trait.name)
                     endControlFlow()
                   } else {
-                    addStatement("%N.depthFirstWalk(this, block)", trait.name)
+                    addStatement("%N.depthFirstWalk(this, visitor)", trait.name)
                   }
                 }
               }
diff --git a/redwood-tooling-codegen/src/main/kotlin/app/cash/redwood/tooling/codegen/types.kt b/redwood-tooling-codegen/src/main/kotlin/app/cash/redwood/tooling/codegen/types.kt
index 69e94c29d7..b85ff8a231 100644
--- a/redwood-tooling-codegen/src/main/kotlin/app/cash/redwood/tooling/codegen/types.kt
+++ b/redwood-tooling-codegen/src/main/kotlin/app/cash/redwood/tooling/codegen/types.kt
@@ -44,6 +44,7 @@ internal object ProtocolGuest {
     ClassName("app.cash.redwood.protocol.guest", "ProtocolMismatchHandler")
   val ProtocolWidget = ClassName("app.cash.redwood.protocol.guest", "ProtocolWidget")
   val ProtocolWidgetChildren = ClassName("app.cash.redwood.protocol.guest", "ProtocolWidgetChildren")
+  val ProtocolWidgetChildrenVisitor = ProtocolWidget.nestedClass("ChildrenVisitor")
   val ProtocolWidgetSystemFactory = ClassName("app.cash.redwood.protocol.guest", "ProtocolWidgetSystemFactory")
 }
 
diff --git a/redwood-treehouse-guest/src/jsMain/kotlin/app/cash/redwood/treehouse/ProtocolBridgeJs.kt b/redwood-treehouse-guest/src/jsMain/kotlin/app/cash/redwood/treehouse/ProtocolBridgeJs.kt
index 8961fcea84..e7f96d5399 100644
--- a/redwood-treehouse-guest/src/jsMain/kotlin/app/cash/redwood/treehouse/ProtocolBridgeJs.kt
+++ b/redwood-treehouse-guest/src/jsMain/kotlin/app/cash/redwood/treehouse/ProtocolBridgeJs.kt
@@ -51,7 +51,7 @@ internal class FastGuestProtocolAdapter(
   hostVersion: RedwoodVersion,
   private val widgetSystemFactory: ProtocolWidgetSystemFactory,
   private val mismatchHandler: ProtocolMismatchHandler = ProtocolMismatchHandler.Throwing,
-) : GuestProtocolAdapter {
+) : GuestProtocolAdapter(hostVersion) {
   private var nextValue = Id.Root.value + 1
   private val widgets = JsMap<Int, ProtocolWidget>()
   private val changes = JsArray<Change>()
@@ -64,8 +64,6 @@ internal class FastGuestProtocolAdapter(
   override val root: ProtocolWidgetChildren =
     ProtocolWidgetChildren(Id.Root, ChildrenTag.Root, this)
 
-  override val synthesizeSubtreeRemoval: Boolean = hostVersion < RedwoodVersion("0.10.0-SNAPSHOT")
-
   override fun sendEvent(event: Event) {
     val node = widgets[event.id.value]
     if (node != null) {