diff --git a/modules/mono/SCsub b/modules/mono/SCsub
index e1f5e2ef28b..706949154e0 100644
--- a/modules/mono/SCsub
+++ b/modules/mono/SCsub
@@ -88,6 +88,9 @@ vars.Update(env_mono)
 if env_mono['mono_glue']:
     env_mono.Append(CPPDEFINES=['MONO_GLUE_ENABLED'])
 
+if env_mono['tools'] or env_mono['target'] != 'release':
+    env_mono.Append(CPPDEFINES=['GD_MONO_HOT_RELOAD'])
+
 # Configure TLS checks
 
 import tls_configure
diff --git a/modules/mono/csharp_script.cpp b/modules/mono/csharp_script.cpp
index 02220ab52f2..0b21ba3347b 100644
--- a/modules/mono/csharp_script.cpp
+++ b/modules/mono/csharp_script.cpp
@@ -607,7 +607,7 @@ struct CSharpScriptDepSort {
 
 void CSharpLanguage::reload_all_scripts() {
 
-#ifdef DEBUG_ENABLED
+#ifdef GD_MONO_HOT_RELOAD
 	if (is_assembly_reloading_needed()) {
 		reload_assemblies(false);
 	}
@@ -618,15 +618,20 @@ void CSharpLanguage::reload_tool_script(const Ref<Script> &p_script, bool p_soft
 
 	(void)p_script; // UNUSED
 
+	CRASH_COND(!Engine::get_singleton()->is_editor_hint());
+
 #ifdef TOOLS_ENABLED
 	MonoReloadNode::get_singleton()->restart_reload_timer();
+#endif
+
+#ifdef GD_MONO_HOT_RELOAD
 	if (is_assembly_reloading_needed()) {
 		reload_assemblies(p_soft_reload);
 	}
 #endif
 }
 
-#ifdef TOOLS_ENABLED
+#ifdef GD_MONO_HOT_RELOAD
 bool CSharpLanguage::is_assembly_reloading_needed() {
 
 	if (!gdmono->is_runtime_initialized())
@@ -658,11 +663,13 @@ bool CSharpLanguage::is_assembly_reloading_needed() {
 			return false; // No assembly to load
 	}
 
+#ifdef TOOLS_ENABLED
 	if (!gdmono->get_core_api_assembly() && gdmono->metadata_is_api_assembly_invalidated(APIAssembly::API_CORE))
 		return false; // The core API assembly to load is invalidated
 
 	if (!gdmono->get_editor_api_assembly() && gdmono->metadata_is_api_assembly_invalidated(APIAssembly::API_EDITOR))
 		return false; // The editor API assembly to load is invalidated
+#endif
 
 	return true;
 }
@@ -760,9 +767,11 @@ void CSharpLanguage::reload_assemblies(bool p_soft_reload) {
 				PlaceHolderScriptInstance *placeholder = scr->placeholder_instance_create(obj);
 				obj->set_script_instance(placeholder);
 
+#ifdef TOOLS_ENABLED
 				// Even though build didn't fail, this tells the placeholder to keep properties and
 				// it allows using property_set_fallback for restoring the state without a valid script.
 				scr->placeholder_fallback_enabled = true;
+#endif
 
 				// Restore Variant properties state, it will be kept by the placeholder until the next script reloading
 				for (List<Pair<StringName, Variant> >::Element *G = scr->pending_reload_state[obj_id].properties.front(); G; G = G->next()) {
@@ -778,13 +787,14 @@ void CSharpLanguage::reload_assemblies(bool p_soft_reload) {
 	for (List<Ref<CSharpScript> >::Element *E = to_reload.front(); E; E = E->next()) {
 
 		Ref<CSharpScript> scr = E->get();
+#ifdef TOOLS_ENABLED
 		scr->exports_invalidated = true;
+#endif
 		scr->signals_invalidated = true;
 		scr->reload(p_soft_reload);
 		scr->update_exports();
 
 		{
-#ifdef DEBUG_ENABLED
 			for (Set<ObjectID>::Element *F = scr->pending_reload_instances.front(); F; F = F->next()) {
 				ObjectID obj_id = F->get();
 				Object *obj = ObjectDB::get_instance(obj_id);
@@ -843,17 +853,18 @@ void CSharpLanguage::reload_assemblies(bool p_soft_reload) {
 
 				scr->pending_reload_state.erase(obj_id);
 			}
-#endif
 
 			scr->pending_reload_instances.clear();
 		}
 	}
 
+#ifdef TOOLS_ENABLED
 	// FIXME: Hack to refresh editor in order to display new properties and signals. See if there is a better alternative.
 	if (Engine::get_singleton()->is_editor_hint()) {
 		EditorNode::get_singleton()->get_inspector()->update_tree();
 		NodeDock::singleton->update_lists();
 	}
+#endif
 }
 #endif
 
@@ -2810,9 +2821,11 @@ Error ResourceFormatSaverCSharpScript::save(const String &p_path, const RES &p_r
 	file->close();
 	memdelete(file);
 
+#ifdef TOOLS_ENABLED
 	if (ScriptServer::is_reload_scripts_on_save_enabled()) {
 		CSharpLanguage::get_singleton()->reload_tool_script(p_resource, false);
 	}
+#endif
 
 	return OK;
 }
diff --git a/modules/mono/csharp_script.h b/modules/mono/csharp_script.h
index e554e1f41f6..8a09be79a60 100644
--- a/modules/mono/csharp_script.h
+++ b/modules/mono/csharp_script.h
@@ -82,10 +82,7 @@ class CSharpScript : public Script {
 
 	Set<Object *> instances;
 
-#ifdef DEBUG_ENABLED
-	Set<ObjectID> pending_reload_instances;
-#endif
-
+#ifdef GD_MONO_HOT_RELOAD
 	struct StateBackup {
 		// TODO
 		// Replace with buffer containing the serialized state of managed scripts.
@@ -93,8 +90,8 @@ class CSharpScript : public Script {
 		List<Pair<StringName, Variant> > properties;
 	};
 
-#ifdef TOOLS_ENABLED
-	Map<ObjectID, CSharpScript::StateBackup> pending_reload_state;
+	Set<ObjectID> pending_reload_instances;
+	Map<ObjectID, StateBackup> pending_reload_state;
 #endif
 
 	String source;
@@ -313,7 +310,7 @@ public:
 	bool debug_break(const String &p_error, bool p_allow_continue = true);
 	bool debug_break_parse(const String &p_file, int p_line, const String &p_error);
 
-#ifdef TOOLS_ENABLED
+#ifdef GD_MONO_HOT_RELOAD
 	bool is_assembly_reloading_needed();
 	void reload_assemblies(bool p_soft_reload);
 #endif
diff --git a/modules/mono/mono_gd/gd_mono.cpp b/modules/mono/mono_gd/gd_mono.cpp
index 42a6fe1ef85..900caefe1ca 100644
--- a/modules/mono/mono_gd/gd_mono.cpp
+++ b/modules/mono/mono_gd/gd_mono.cpp
@@ -731,7 +731,9 @@ Error GDMono::_unload_scripts_domain() {
 #endif
 
 	core_api_assembly_out_of_sync = false;
+#ifdef TOOLS_ENABLED
 	editor_api_assembly_out_of_sync = false;
+#endif
 
 	MonoDomain *domain = scripts_domain;
 	scripts_domain = NULL;
@@ -764,7 +766,7 @@ Error GDMono::_load_tools_domain() {
 }
 #endif
 
-#ifdef TOOLS_ENABLED
+#ifdef GD_MONO_HOT_RELOAD
 Error GDMono::reload_scripts_domain() {
 
 	ERR_FAIL_COND_V(!runtime_initialized, ERR_BUG);
@@ -785,8 +787,12 @@ Error GDMono::reload_scripts_domain() {
 
 #ifdef MONO_GLUE_ENABLED
 	if (!_load_api_assemblies()) {
-		if ((core_api_assembly && (core_api_assembly_out_of_sync || !GDMonoUtils::mono_cache.godot_api_cache_updated)) ||
-				(editor_api_assembly && editor_api_assembly_out_of_sync)) {
+		if ((core_api_assembly && (core_api_assembly_out_of_sync || !GDMonoUtils::mono_cache.godot_api_cache_updated))
+#ifdef TOOLS_ENABLED
+				|| (editor_api_assembly && editor_api_assembly_out_of_sync)
+#endif
+		) {
+#ifdef TOOLS_ENABLED
 			// The assembly was successfully loaded, but the full api could not be cached.
 			// This is most likely an outdated assembly loaded because of an invalid version in the
 			// metadata, so we invalidate the version in the metadata and unload the script domain.
@@ -810,6 +816,10 @@ Error GDMono::reload_scripts_domain() {
 			}
 
 			return ERR_CANT_RESOLVE;
+#else
+			ERR_PRINT("The loaded API assembly is invalid");
+			CRASH_NOW();
+#endif
 		} else {
 			return ERR_CANT_OPEN;
 		}
@@ -924,7 +934,9 @@ GDMono::GDMono() {
 #endif
 
 	core_api_assembly_out_of_sync = false;
+#ifdef TOOLS_ENABLED
 	editor_api_assembly_out_of_sync = false;
+#endif
 
 	corlib_assembly = NULL;
 	core_api_assembly = NULL;
diff --git a/modules/mono/mono_gd/gd_mono.h b/modules/mono/mono_gd/gd_mono.h
index 6a00b287b02..13de3061b38 100644
--- a/modules/mono/mono_gd/gd_mono.h
+++ b/modules/mono/mono_gd/gd_mono.h
@@ -95,7 +95,9 @@ class GDMono {
 #endif
 
 	bool core_api_assembly_out_of_sync;
+#ifdef TOOLS_ENABLED
 	bool editor_api_assembly_out_of_sync;
+#endif
 
 	GDMonoAssembly *corlib_assembly;
 	GDMonoAssembly *core_api_assembly;
@@ -193,7 +195,7 @@ public:
 
 	GDMonoClass *get_class(MonoClass *p_raw_class);
 
-#ifdef TOOLS_ENABLED
+#ifdef GD_MONO_HOT_RELOAD
 	Error reload_scripts_domain();
 #endif
 
diff --git a/modules/mono/utils/osx_utils.h b/modules/mono/utils/osx_utils.h
index 918642f7b26..cc72233058b 100644
--- a/modules/mono/utils/osx_utils.h
+++ b/modules/mono/utils/osx_utils.h
@@ -31,6 +31,7 @@
 #include "core/ustring.h"
 
 #ifndef OSX_UTILS_H
+#define OSX_UTILS_H
 
 #ifdef OSX_ENABLED