diff --git a/Assets/UdonSharp/Editor/Editors/UdonSharpSettings.cs b/Assets/UdonSharp/Editor/Editors/UdonSharpSettings.cs
index 94bb6cf6..cf9756fe 100644
--- a/Assets/UdonSharp/Editor/Editors/UdonSharpSettings.cs
+++ b/Assets/UdonSharp/Editor/Editors/UdonSharpSettings.cs
@@ -26,6 +26,7 @@ void Start()
 
         public bool autoCompileOnModify = true;
         public bool compileAllScripts = true;
+        public bool waitForFocus = false;
         public TextAsset newScriptTemplateOverride = null;
 
         public bool buildDebugInfo = true;
@@ -89,6 +90,7 @@ public class UdonSharpSettingsProvider
     {
         private static GUIContent autoCompileLabel = new GUIContent("Auto compile on modify", "Trigger a compile whenever a U# source file is modified.");
         private static GUIContent compileAllLabel = new GUIContent("Compile all scripts", "Compile all scripts when a script is modified. This prevents some potential for weird issues where classes don't match");
+        private static GUIContent waitForFocusLabel = new GUIContent("Compile on focus", "Waits for application focus to compile any changed U# scripts");
         private static GUIContent templateOverrideLabel = new GUIContent("Script template override", "A custom override file to use as a template for newly created U# files. Put \"<TemplateClassName>\" in place of a class name for it to automatically populate with the file name.");
         private static GUIContent includeDebugInfoLabel = new GUIContent("Debug build", "Include debug info in build");
         private static GUIContent includeInlineCodeLabel = new GUIContent("Inline code", "Include C# inline in generated assembly");
@@ -116,6 +118,8 @@ public static SettingsProvider CreateSettingsProvider()
                             EditorGUILayout.HelpBox("Only compiling the script that has been modified can cause issues if you have multiple scripts communicating via methods.", MessageType.Warning);
                     }
 
+                    EditorGUILayout.PropertyField(settingsObject.FindProperty(nameof(UdonSharpSettings.waitForFocus)), waitForFocusLabel);
+
                     EditorGUILayout.PropertyField(settingsObject.FindProperty("newScriptTemplateOverride"), templateOverrideLabel);
 
                     EditorGUILayout.Space();
diff --git a/Assets/UdonSharp/Editor/UdonSharpAssetCompileWatcher.cs b/Assets/UdonSharp/Editor/UdonSharpAssetCompileWatcher.cs
index 1d38db47..2abdd00d 100644
--- a/Assets/UdonSharp/Editor/UdonSharpAssetCompileWatcher.cs
+++ b/Assets/UdonSharp/Editor/UdonSharpAssetCompileWatcher.cs
@@ -25,7 +25,7 @@ public class UdonSharpAssetCompileWatcher
         static readonly object modifiedFileLock = new object();
 
         static HashSet<string> modifiedFilePaths = new HashSet<string>();
-        static HashSet<string> renamedFilePaths = new HashSet<string>();
+        static HashSet<MonoScript> modifiedScripts = new HashSet<MonoScript>();
 
         static bool lastEnabledState = false;
 
@@ -37,7 +37,23 @@ static UdonSharpAssetCompileWatcher()
         static void SetupWatchers() 
         {
             if (fileSystemWatchers != null)
+            {
+                UdonSharpSettings settings = UdonSharpSettings.GetSettings();
+
+                bool watcherEnabled = settings == null || settings.autoCompileOnModify;
+
+                if (watcherEnabled != lastEnabledState)
+                {
+                    lastEnabledState = watcherEnabled;
+                    foreach (FileSystemWatcher watcher in fileSystemWatchers)
+                    {
+                        if (watcher != null)
+                            watcher.EnableRaisingEvents = watcherEnabled;
+                    }
+                }
+
                 return;
+            }
 
             AssemblyReloadEvents.beforeAssemblyReload += CleanupWatchers;
 
@@ -82,11 +98,23 @@ static void CleanupWatchers()
             }
         }
 
-        static void HandleScriptModifications(List<MonoScript> scripts)
+        static void HandleScriptModifications()
         {
             UdonSharpSettings settings = UdonSharpSettings.GetSettings();
 
-            if (settings != null && !settings.autoCompileOnModify)
+            if (settings != null)
+            {
+                if (!settings.autoCompileOnModify)
+                {
+                    modifiedScripts.Clear();
+                    return;
+                }
+
+                if (settings.waitForFocus && !UnityEditorInternal.InternalEditorUtility.isApplicationActive)
+                    return;
+            }
+
+            if (modifiedScripts.Count == 0)
                 return;
 
             string[] udonSharpDataAssets = AssetDatabase.FindAssets($"t:{typeof(UdonSharpProgramAsset).Name}");
@@ -100,7 +128,7 @@ static void HandleScriptModifications(List<MonoScript> scripts)
 
             HashSet<UdonSharpProgramAsset> assetsToUpdate = new HashSet<UdonSharpProgramAsset>();
 
-            foreach (MonoScript script in scripts)
+            foreach (MonoScript script in modifiedScripts)
             {
                 foreach (UdonSharpProgramAsset programAsset in udonSharpPrograms)
                 {
@@ -109,46 +137,63 @@ static void HandleScriptModifications(List<MonoScript> scripts)
                 }
             }
 
-            if (assetsToUpdate.Count > 0)
+            try
             {
-                if (settings == null || settings.compileAllScripts)
-                {
-                    UdonSharpProgramAsset.CompileAllCsPrograms();
-                }
-                else
+                if (assetsToUpdate.Count > 0)
                 {
-                    UdonSharpCompiler compiler = new UdonSharpCompiler(assetsToUpdate.ToArray());
-                    compiler.Compile();
+                    if (settings == null || settings.compileAllScripts)
+                    {
+                        UdonSharpProgramAsset.CompileAllCsPrograms();
+                    }
+                    else
+                    {
+                        UdonSharpCompiler compiler = new UdonSharpCompiler(assetsToUpdate.ToArray());
+                        compiler.Compile();
+                    }
                 }
             }
+            finally
+            {
+                modifiedScripts.Clear();
+            }
+
+            modifiedScripts.Clear();
         }
 
         static void OnEditorUpdate()
         {
             SetupWatchers();
 
-            UdonSharpSettings settings = UdonSharpSettings.GetSettings();
+            // Prevent people from entering play mode when there are compile errors, like normal Unity C#
+            if (EditorApplication.isPlayingOrWillChangePlaymode && !EditorApplication.isPlaying)
+            {
+                string[] udonSharpDataAssets = AssetDatabase.FindAssets($"t:{typeof(UdonSharpProgramAsset).Name}");
 
-            bool watcherEnabled = settings == null || settings.autoCompileOnModify;
+                bool foundCompileErrors = false;
 
-            if (watcherEnabled != lastEnabledState && fileSystemWatchers != null)
-            {
-                lastEnabledState = watcherEnabled;
-                foreach (FileSystemWatcher watcher in fileSystemWatchers)
+                foreach (string dataGuid in udonSharpDataAssets)
                 {
-                    if (watcher != null)
-                        watcher.EnableRaisingEvents = watcherEnabled;
+                    UdonSharpProgramAsset programAsset = AssetDatabase.LoadAssetAtPath<UdonSharpProgramAsset>(AssetDatabase.GUIDToAssetPath(dataGuid));
+
+                    if (programAsset.sourceCsScript != null && programAsset.compileErrors.Count > 0)
+                    {
+                        foundCompileErrors = true;
+                        break;
+                    }
                 }
-            }
 
-            List<MonoScript> modifiedScripts = null;
+                if (foundCompileErrors)
+                {
+                    EditorApplication.isPlaying = false;
 
+                    typeof(SceneView).GetMethod("ShowNotification", System.Reflection.BindingFlags.NonPublic | System.Reflection.BindingFlags.Static).Invoke(null, new object[] { "All U# compiler errors have to be fixed before you can enter playmode!" });
+                }
+            }
+            
             lock (modifiedFileLock)
             {
                 if (modifiedFilePaths.Count > 0)
                 {
-                    modifiedScripts = new List<MonoScript>();
-
                     foreach (string filePath in modifiedFilePaths)
                     {
                         MonoScript asset = AssetDatabase.LoadAssetAtPath<MonoScript>(filePath.Replace(Application.dataPath.Replace("/", "\\"), "Assets"));
@@ -159,8 +204,7 @@ static void OnEditorUpdate()
                 }
             }
 
-            if (modifiedScripts != null && modifiedScripts.Count > 0)
-                HandleScriptModifications(modifiedScripts);
+            HandleScriptModifications();
         }
 
         static void OnSourceFileChanged(object source, FileSystemEventArgs args)
diff --git a/Assets/UdonSharp/version.txt b/Assets/UdonSharp/version.txt
index d5bd67d2..1902df97 100644
--- a/Assets/UdonSharp/version.txt
+++ b/Assets/UdonSharp/version.txt
@@ -1 +1 @@
-v0.15.3
+v0.15.5