diff --git a/Packages/nadena.dev.modular-avatar/Editor/AnimatorMerger.cs b/Packages/nadena.dev.modular-avatar/Editor/AnimatorMerger.cs
index 86ad1481..19401efc 100644
--- a/Packages/nadena.dev.modular-avatar/Editor/AnimatorMerger.cs
+++ b/Packages/nadena.dev.modular-avatar/Editor/AnimatorMerger.cs
@@ -33,7 +33,7 @@ using Object = UnityEngine.Object;
 
 namespace nadena.dev.modular_avatar.core.editor
 {
-    public class AnimatorCombiner
+    internal class AnimatorCombiner
     {
         private readonly AnimatorController _combined;
 
diff --git a/Packages/nadena.dev.modular-avatar/Editor/ApplyOnPlay.cs b/Packages/nadena.dev.modular-avatar/Editor/ApplyOnPlay.cs
index cddbd0bc..99b5f598 100644
--- a/Packages/nadena.dev.modular-avatar/Editor/ApplyOnPlay.cs
+++ b/Packages/nadena.dev.modular-avatar/Editor/ApplyOnPlay.cs
@@ -23,15 +23,11 @@
  */
 
 using UnityEditor;
-using UnityEngine;
-using UnityEngine.SceneManagement;
-using VRC.SDK3.Avatars.Components;
-using VRC.SDKBase.Editor.BuildPipeline;
 
 namespace nadena.dev.modular_avatar.core.editor
 {
     [InitializeOnLoad]
-    public static class ApplyOnPlay
+    internal static class ApplyOnPlay
     {
         private const string MENU_NAME = "Tools/Modular Avatar/Apply on Play";
 
diff --git a/Packages/nadena.dev.modular-avatar/Editor/AvatarProcessor.cs b/Packages/nadena.dev.modular-avatar/Editor/AvatarProcessor.cs
index ace3d115..8095adbe 100644
--- a/Packages/nadena.dev.modular-avatar/Editor/AvatarProcessor.cs
+++ b/Packages/nadena.dev.modular-avatar/Editor/AvatarProcessor.cs
@@ -39,6 +39,9 @@ namespace nadena.dev.modular_avatar.core.editor
     {
         public delegate void AvatarProcessorCallback(GameObject obj);
 
+        /// <summary>
+        /// This API is NOT stable. Do not use it yet.
+        /// </summary>
         public static event AvatarProcessorCallback AfterProcessing;
 
         static AvatarProcessor()
diff --git a/Packages/nadena.dev.modular-avatar/Editor/Inspector/AvatarObjectReferenceDrawer.cs b/Packages/nadena.dev.modular-avatar/Editor/Inspector/AvatarObjectReferenceDrawer.cs
index 3c44ab8d..603958a9 100644
--- a/Packages/nadena.dev.modular-avatar/Editor/Inspector/AvatarObjectReferenceDrawer.cs
+++ b/Packages/nadena.dev.modular-avatar/Editor/Inspector/AvatarObjectReferenceDrawer.cs
@@ -5,7 +5,7 @@ using VRC.SDK3.Avatars.Components;
 namespace nadena.dev.modular_avatar.core.editor
 {
     [CustomPropertyDrawer(typeof(AvatarObjectReference))]
-    public class AvatarObjectReferenceDrawer : PropertyDrawer
+    internal class AvatarObjectReferenceDrawer : PropertyDrawer
     {
         public override void OnGUI(Rect position, SerializedProperty property, GUIContent label)
         {
diff --git a/Packages/nadena.dev.modular-avatar/Editor/Inspector/ZeroIndentScope.cs b/Packages/nadena.dev.modular-avatar/Editor/Inspector/ZeroIndentScope.cs
index d5c8f4af..d2dc696d 100644
--- a/Packages/nadena.dev.modular-avatar/Editor/Inspector/ZeroIndentScope.cs
+++ b/Packages/nadena.dev.modular-avatar/Editor/Inspector/ZeroIndentScope.cs
@@ -3,7 +3,7 @@ using UnityEditor;
 
 namespace nadena.dev.modular_avatar.core.editor
 {
-    public class ZeroIndentScope : IDisposable
+    internal class ZeroIndentScope : IDisposable
     {
         private int oldIndentLevel;
 
diff --git a/Packages/nadena.dev.modular-avatar/Editor/Localization/Localization.cs b/Packages/nadena.dev.modular-avatar/Editor/Localization/Localization.cs
index ed9ace30..d1d064e1 100644
--- a/Packages/nadena.dev.modular-avatar/Editor/Localization/Localization.cs
+++ b/Packages/nadena.dev.modular-avatar/Editor/Localization/Localization.cs
@@ -9,7 +9,7 @@ using UnityEngine;
 
 namespace nadena.dev.modular_avatar.core.editor
 {
-    public static class Localization
+    internal static class Localization
     {
         private const string localizationPathGuid = "488c994003974b3ab2796371cf627bca";
         private static string localizationPathRoot = AssetDatabase.GUIDToAssetPath(localizationPathGuid);
diff --git a/Packages/nadena.dev.modular-avatar/Editor/MenuInstallHook.cs b/Packages/nadena.dev.modular-avatar/Editor/MenuInstallHook.cs
index 19417d97..cb178600 100644
--- a/Packages/nadena.dev.modular-avatar/Editor/MenuInstallHook.cs
+++ b/Packages/nadena.dev.modular-avatar/Editor/MenuInstallHook.cs
@@ -9,7 +9,7 @@ using Object = UnityEngine.Object;
 
 namespace nadena.dev.modular_avatar.core.editor
 {
-    public class MenuInstallHook
+    internal class MenuInstallHook
     {
         private static Texture2D _moreIcon = AssetDatabase.LoadAssetAtPath<Texture2D>(
             "Packages/nadena.dev.modular-avatar/Runtime/Icons/Icon_More_A.png"
diff --git a/Packages/nadena.dev.modular-avatar/Editor/MergeArmatureHook.cs b/Packages/nadena.dev.modular-avatar/Editor/MergeArmatureHook.cs
index 6135a0eb..9a7c652a 100644
--- a/Packages/nadena.dev.modular-avatar/Editor/MergeArmatureHook.cs
+++ b/Packages/nadena.dev.modular-avatar/Editor/MergeArmatureHook.cs
@@ -33,7 +33,7 @@ using Object = UnityEngine.Object;
 
 namespace nadena.dev.modular_avatar.core.editor
 {
-    public class MergeArmatureHook
+    internal class MergeArmatureHook
     {
         private Dictionary<Transform, Transform> BoneRemappings = new Dictionary<Transform, Transform>();
         private HashSet<GameObject> ToDelete = new HashSet<GameObject>();
diff --git a/Packages/nadena.dev.modular-avatar/Editor/MeshRetargeter.cs b/Packages/nadena.dev.modular-avatar/Editor/MeshRetargeter.cs
index d115a698..0461a1c0 100644
--- a/Packages/nadena.dev.modular-avatar/Editor/MeshRetargeter.cs
+++ b/Packages/nadena.dev.modular-avatar/Editor/MeshRetargeter.cs
@@ -127,7 +127,7 @@ namespace nadena.dev.modular_avatar.core.editor
      * This class processes a given mesh, adjusting the bind poses for any bones that are to be merged to instead match
      * the bind pose of the original avatar's bone.
      */
-    public class MeshRetargeter
+    internal class MeshRetargeter
     {
         private readonly SkinnedMeshRenderer renderer;
         private Mesh src, dst;
diff --git a/Packages/nadena.dev.modular-avatar/Editor/ModularAvatarSettings.cs b/Packages/nadena.dev.modular-avatar/Editor/ModularAvatarSettings.cs
index caee7d50..02b63753 100644
--- a/Packages/nadena.dev.modular-avatar/Editor/ModularAvatarSettings.cs
+++ b/Packages/nadena.dev.modular-avatar/Editor/ModularAvatarSettings.cs
@@ -27,7 +27,7 @@ using UnityEngine;
 
 namespace nadena.dev.modular_avatar.core.editor
 {
-    public static class ModularAvatarSettings
+    internal static class ModularAvatarSettings
     {
         private const string PREFKEY_APPLY_ON_PLAY = "nadena.dev.modular-avatar.applyOnPlay";
 #if UNITY_EDITOR
diff --git a/Packages/nadena.dev.modular-avatar/Editor/ParameterPolicy.cs b/Packages/nadena.dev.modular-avatar/Editor/ParameterPolicy.cs
index 6c37d08b..57045db8 100644
--- a/Packages/nadena.dev.modular-avatar/Editor/ParameterPolicy.cs
+++ b/Packages/nadena.dev.modular-avatar/Editor/ParameterPolicy.cs
@@ -11,7 +11,7 @@ using VRC.SDK3.Dynamics.PhysBone.Components;
 
 namespace nadena.dev.modular_avatar.core.editor
 {
-    public struct DetectedParameter
+    internal struct DetectedParameter
     {
         public string OriginalName;
         public bool IsPrefix;
@@ -22,7 +22,7 @@ namespace nadena.dev.modular_avatar.core.editor
         public string MapKey => IsPrefix ? OriginalName + "*" : OriginalName;
     }
 
-    public static class ParameterPolicy
+    internal static class ParameterPolicy
     {
         /// <summary>
         /// Parameters predefined by the VRChat SDK which should not be offered as remappable.
diff --git a/Packages/nadena.dev.modular-avatar/Editor/PathMappings.cs b/Packages/nadena.dev.modular-avatar/Editor/PathMappings.cs
index a946ca6c..c41fd388 100644
--- a/Packages/nadena.dev.modular-avatar/Editor/PathMappings.cs
+++ b/Packages/nadena.dev.modular-avatar/Editor/PathMappings.cs
@@ -28,11 +28,11 @@ using VRC.SDKBase.Editor.BuildPipeline;
 
 namespace nadena.dev.modular_avatar.core.editor
 {
-    public static class PathMappings
+    internal static class PathMappings
     {
         private static List<(string, MappingEntry)> Mappings = new List<(string, MappingEntry)>();
 
-        public struct MappingEntry
+        internal struct MappingEntry
         {
             public string path;
             public string transformPath;
diff --git a/Packages/nadena.dev.modular-avatar/Editor/RenameParametersHook.cs b/Packages/nadena.dev.modular-avatar/Editor/RenameParametersHook.cs
index 4be40446..d4c16d3b 100644
--- a/Packages/nadena.dev.modular-avatar/Editor/RenameParametersHook.cs
+++ b/Packages/nadena.dev.modular-avatar/Editor/RenameParametersHook.cs
@@ -13,7 +13,7 @@ using Object = UnityEngine.Object;
 
 namespace nadena.dev.modular_avatar.core.editor
 {
-    public class RenameParametersHook
+    internal class RenameParametersHook
     {
         private const string DEFAULT_EXP_PARAMS_ASSET_GUID = "03a6d797deb62f0429471c4e17ea99a7";
 
diff --git a/Packages/nadena.dev.modular-avatar/Editor/Util.cs b/Packages/nadena.dev.modular-avatar/Editor/Util.cs
index bfacf6f8..6c0551f9 100644
--- a/Packages/nadena.dev.modular-avatar/Editor/Util.cs
+++ b/Packages/nadena.dev.modular-avatar/Editor/Util.cs
@@ -43,7 +43,7 @@ namespace nadena.dev.modular_avatar.core.editor
     }
 
     [InitializeOnLoad]
-    public static class Util
+    internal static class Util
     {
         private const string generatedAssetsSubdirectory = "999_Modular_Avatar_Generated";
         private const string generatedAssetsPath = "Assets/" + generatedAssetsSubdirectory;
diff --git a/Packages/nadena.dev.modular-avatar/Editor/Version.cs b/Packages/nadena.dev.modular-avatar/Editor/Version.cs
index e0ac49a4..dfd1aea3 100644
--- a/Packages/nadena.dev.modular-avatar/Editor/Version.cs
+++ b/Packages/nadena.dev.modular-avatar/Editor/Version.cs
@@ -27,7 +27,7 @@ using JetBrains.Annotations;
 namespace nadena.dev.modular_avatar.core.editor
 {
     [UsedImplicitly]
-    public static class Version
+    internal static class Version
     {
         [UsedImplicitly] public const string VERSION = "0.0.1";
     }
diff --git a/Packages/nadena.dev.modular-avatar/Runtime/RuntimeUtil.cs b/Packages/nadena.dev.modular-avatar/Runtime/RuntimeUtil.cs
index 2c8d6454..b5b38f7e 100644
--- a/Packages/nadena.dev.modular-avatar/Runtime/RuntimeUtil.cs
+++ b/Packages/nadena.dev.modular-avatar/Runtime/RuntimeUtil.cs
@@ -33,6 +33,10 @@ using System.Reflection;
 
 namespace nadena.dev.modular_avatar.core
 {
+    /**
+     * This class is public for the benefit of the Editor namespace classes, but is not a stable API and may change
+     * on patch releases.
+     */
     public static class RuntimeUtil
     {
         // Initialized in Util