diff --git a/binding_generator.py b/binding_generator.py
index e7609b2c8..0ad18e366 100644
--- a/binding_generator.py
+++ b/binding_generator.py
@@ -736,6 +736,23 @@ def generate_builtin_class_header(builtin_api, size, used_classes, fully_used_cl
     result.append("")
     result.append("public:")
 
+    if class_name == "Callable":
+        result.append("\tstruct CallError {")
+        result.append("\t\tenum Error {")
+        result.append("\t\t\tCALL_OK,")
+        result.append("\t\t\tCALL_ERROR_INVALID_METHOD,")
+        result.append("\t\t\tCALL_ERROR_INVALID_ARGUMENT,")
+        result.append("\t\t\tCALL_ERROR_TOO_MANY_ARGUMENTS,")
+        result.append("\t\t\tCALL_ERROR_TOO_FEW_ARGUMENTS,")
+        result.append("\t\t\tCALL_ERROR_INSTANCE_IS_NULL,")
+        result.append("\t\t\tCALL_ERROR_METHOD_NOT_CONST,")
+        result.append("\t\t};")
+        result.append("\t\tError error = Error::CALL_OK;")
+        result.append("\t\tint argument = 0;")
+        result.append("\t\tint expected = 0;")
+        result.append("\t};")
+        result.append("")
+
     result.append(
         f"\t_FORCE_INLINE_ GDExtensionTypePtr _native_ptr() const {{ return const_cast<uint8_t (*)[{snake_class_name}_SIZE]>(&opaque); }}"
     )
diff --git a/include/godot_cpp/classes/script_instance_extension.hpp b/include/godot_cpp/classes/script_instance_extension.hpp
new file mode 100644
index 000000000..cca99db6b
--- /dev/null
+++ b/include/godot_cpp/classes/script_instance_extension.hpp
@@ -0,0 +1,109 @@
+/**************************************************************************/
+/*  script_instance_extension.hpp                                         */
+/**************************************************************************/
+/*                         This file is part of:                          */
+/*                             GODOT ENGINE                               */
+/*                        https://godotengine.org                         */
+/**************************************************************************/
+/* Copyright (c) 2014-present Godot Engine contributors (see AUTHORS.md). */
+/* Copyright (c) 2007-2014 Juan Linietsky, Ariel Manzur.                  */
+/*                                                                        */
+/* Permission is hereby granted, free of charge, to any person obtaining  */
+/* a copy of this software and associated documentation files (the        */
+/* "Software"), to deal in the Software without restriction, including    */
+/* without limitation the rights to use, copy, modify, merge, publish,    */
+/* distribute, sublicense, and/or sell copies of the Software, and to     */
+/* permit persons to whom the Software is furnished to do so, subject to  */
+/* the following conditions:                                              */
+/*                                                                        */
+/* The above copyright notice and this permission notice shall be         */
+/* included in all copies or substantial portions of the Software.        */
+/*                                                                        */
+/* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,        */
+/* EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF     */
+/* MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. */
+/* IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY   */
+/* CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT,   */
+/* TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE      */
+/* SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.                 */
+/**************************************************************************/
+
+#ifndef GODOT_SCRIPT_INSTANCE_EXTENSION_HPP
+#define GODOT_SCRIPT_INSTANCE_EXTENSION_HPP
+
+#include <godot_cpp/classes/ref.hpp>
+#include <godot_cpp/templates/pair.hpp>
+#include <godot_cpp/variant/string_name.hpp>
+
+namespace godot {
+
+class Script;
+class ScriptLanguage;
+
+class ScriptInstanceExtension {
+	static GDExtensionScriptInstanceInfo3 script_instance_info;
+
+	// Used to keep the refcounted properties alive after passing pointers to the data back to Godot.
+	static thread_local List<PropertyInfo> property_list;
+	static thread_local List<MethodInfo> method_list;
+
+	static GDExtensionBool gdextension_script_instance_set(GDExtensionScriptInstanceDataPtr p_instance, GDExtensionConstStringNamePtr p_name, GDExtensionConstVariantPtr p_value);
+	static GDExtensionBool gdextension_script_instance_get(GDExtensionScriptInstanceDataPtr p_instance, GDExtensionConstStringNamePtr p_name, GDExtensionVariantPtr r_ret);
+	static const GDExtensionPropertyInfo *gdextension_script_instance_get_property_list(GDExtensionScriptInstanceDataPtr p_instance, uint32_t *r_count);
+	static void gdextension_script_instance_free_property_list(GDExtensionScriptInstanceDataPtr p_instance, const GDExtensionPropertyInfo *p_list, uint32_t p_count);
+	static GDExtensionVariantType gdextension_script_instance_get_property_type(GDExtensionScriptInstanceDataPtr p_instance, GDExtensionConstStringNamePtr p_name, GDExtensionBool *r_is_valid);
+	static GDExtensionBool gdextension_script_instance_validate_property(GDExtensionScriptInstanceDataPtr p_instance, GDExtensionPropertyInfo *p_property);
+	static GDExtensionBool gdextension_script_instance_property_can_revert(GDExtensionScriptInstanceDataPtr p_instance, GDExtensionConstStringNamePtr p_name);
+	static GDExtensionBool gdextension_script_instance_property_get_revert(GDExtensionScriptInstanceDataPtr p_instance, GDExtensionConstStringNamePtr p_name, GDExtensionVariantPtr r_ret);
+	static GDExtensionObjectPtr gdextension_script_instance_get_owner(GDExtensionScriptInstanceDataPtr p_instance);
+	static void gdextension_script_instance_get_property_state(GDExtensionScriptInstanceDataPtr p_instance, GDExtensionScriptInstancePropertyStateAdd p_add_func, void *p_userdata);
+	static const GDExtensionMethodInfo *gdextension_script_instance_get_method_list(GDExtensionScriptInstanceDataPtr p_instance, uint32_t *r_count);
+	static void gdextension_script_instance_free_method_list(GDExtensionScriptInstanceDataPtr p_instance, const GDExtensionMethodInfo *p_list, uint32_t p_count);
+	static GDExtensionBool gdextension_script_instance_has_method(GDExtensionScriptInstanceDataPtr p_instance, GDExtensionConstStringNamePtr p_name);
+	static GDExtensionInt gdextension_script_instance_get_method_argument_count(GDExtensionScriptInstanceDataPtr p_instance, GDExtensionConstStringNamePtr p_name, GDExtensionBool *r_is_valid);
+	static void gdextension_script_instance_call(GDExtensionScriptInstanceDataPtr p_instance, GDExtensionConstStringNamePtr p_method, const GDExtensionConstVariantPtr *p_args, GDExtensionInt p_argument_count, GDExtensionVariantPtr r_return, GDExtensionCallError *r_error);
+	static void gdextension_script_instance_notification(GDExtensionScriptInstanceDataPtr p_instance, int32_t p_what, GDExtensionBool p_reversed);
+	static void gdextension_script_instance_to_string(GDExtensionScriptInstanceDataPtr p_instance, GDExtensionBool *r_is_valid, GDExtensionStringPtr r_out);
+	static void gdextension_script_instance_refcount_incremented(GDExtensionScriptInstanceDataPtr p_instance);
+	static GDExtensionBool gdextension_script_instance_refcount_decremented(GDExtensionScriptInstanceDataPtr p_instance);
+	static GDExtensionObjectPtr gdextension_script_instance_get_script(GDExtensionScriptInstanceDataPtr p_instance);
+	static GDExtensionBool gdextension_script_instance_is_placeholder(GDExtensionScriptInstanceDataPtr p_instance);
+	static GDExtensionBool gdextension_script_instance_set_fallback(GDExtensionScriptInstanceDataPtr p_instance, GDExtensionConstStringNamePtr p_name, GDExtensionConstVariantPtr p_value);
+	static GDExtensionBool gdextension_script_instance_get_fallback(GDExtensionScriptInstanceDataPtr p_instance, GDExtensionConstStringNamePtr p_name, GDExtensionVariantPtr r_ret);
+	static GDExtensionScriptLanguagePtr gdextension_script_instance_get_language(GDExtensionScriptInstanceDataPtr p_instance);
+	static void gdextension_script_instance_free(GDExtensionScriptInstanceDataPtr p_instance);
+
+public:
+	static GDExtensionScriptInstancePtr create_native_instance(ScriptInstanceExtension *p_instance) {
+		return internal::gdextension_interface_script_instance_create3(&script_instance_info, p_instance);
+	}
+
+	virtual bool set(const StringName &p_name, const Variant &p_value) = 0;
+	virtual bool get(const StringName &p_name, Variant &r_ret) const = 0;
+	virtual void get_property_list(List<PropertyInfo> *p_properties) const = 0;
+	virtual Variant::Type get_property_type(const StringName &p_name, bool *r_is_valid) const = 0;
+	virtual void validate_property(PropertyInfo &p_property) const = 0;
+	virtual bool property_can_revert(const StringName &p_name) const = 0;
+	virtual bool property_get_revert(const StringName &p_name, Variant &r_ret) const = 0;
+	virtual Object *get_owner() = 0;
+	virtual void get_property_state(List<Pair<StringName, Variant>> &state);
+	virtual void get_method_list(List<MethodInfo> *p_info) const = 0;
+	virtual bool has_method(const StringName &p_method) const = 0;
+	virtual int get_method_argument_count(const StringName &p_method, bool *r_is_valid = nullptr) const = 0;
+	virtual Variant callp(const StringName &p_method, const Variant **p_args, int p_argcount, Callable::CallError &r_error) = 0;
+	virtual void notification(int p_notification, bool p_reversed) = 0;
+	virtual String to_string(bool *r_valid) = 0;
+	virtual void refcount_incremented() = 0;
+	virtual bool refcount_decremented() = 0;
+	virtual Ref<Script> get_script() const = 0;
+	virtual bool is_placeholder() const = 0;
+	virtual void property_set_fallback(const StringName &p_name, const Variant &p_value, bool *r_valid) = 0;
+	virtual Variant property_get_fallback(const StringName &p_name, bool *r_valid) = 0;
+	virtual ScriptLanguage *get_language() = 0;
+
+	virtual ~ScriptInstanceExtension(){};
+};
+
+}; // namespace godot
+
+#endif // GODOT_SCRIPT_INSTANCE_EXTENSION_HPP
diff --git a/src/classes/script_instance_extension.cpp b/src/classes/script_instance_extension.cpp
new file mode 100644
index 000000000..d75572b61
--- /dev/null
+++ b/src/classes/script_instance_extension.cpp
@@ -0,0 +1,316 @@
+/**************************************************************************/
+/*  script_instance_extension.cpp                                         */
+/**************************************************************************/
+/*                         This file is part of:                          */
+/*                             GODOT ENGINE                               */
+/*                        https://godotengine.org                         */
+/**************************************************************************/
+/* Copyright (c) 2014-present Godot Engine contributors (see AUTHORS.md). */
+/* Copyright (c) 2007-2014 Juan Linietsky, Ariel Manzur.                  */
+/*                                                                        */
+/* Permission is hereby granted, free of charge, to any person obtaining  */
+/* a copy of this software and associated documentation files (the        */
+/* "Software"), to deal in the Software without restriction, including    */
+/* without limitation the rights to use, copy, modify, merge, publish,    */
+/* distribute, sublicense, and/or sell copies of the Software, and to     */
+/* permit persons to whom the Software is furnished to do so, subject to  */
+/* the following conditions:                                              */
+/*                                                                        */
+/* The above copyright notice and this permission notice shall be         */
+/* included in all copies or substantial portions of the Software.        */
+/*                                                                        */
+/* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,        */
+/* EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF     */
+/* MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. */
+/* IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY   */
+/* CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT,   */
+/* TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE      */
+/* SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.                 */
+/**************************************************************************/
+
+#include <godot_cpp/classes/script_instance_extension.hpp>
+
+#include <godot_cpp/classes/script.hpp>
+#include <godot_cpp/classes/script_language_extension.hpp>
+
+using namespace godot;
+
+GDExtensionBool ScriptInstanceExtension::gdextension_script_instance_set(GDExtensionScriptInstanceDataPtr p_instance, GDExtensionConstStringNamePtr p_name, GDExtensionConstVariantPtr p_value) {
+	ScriptInstanceExtension *instance = reinterpret_cast<ScriptInstanceExtension *>(p_instance);
+	const StringName *name = reinterpret_cast<const StringName *>(p_name);
+	const Variant *value = reinterpret_cast<const Variant *>(p_value);
+
+	return instance->set(*name, *value);
+}
+
+GDExtensionBool ScriptInstanceExtension::gdextension_script_instance_get(GDExtensionScriptInstanceDataPtr p_instance, GDExtensionConstStringNamePtr p_name, GDExtensionVariantPtr r_ret) {
+	ScriptInstanceExtension *instance = reinterpret_cast<ScriptInstanceExtension *>(p_instance);
+	const StringName *name = reinterpret_cast<const StringName *>(p_name);
+	Variant *ret = reinterpret_cast<Variant *>(r_ret);
+
+	return instance->get(*name, *ret);
+}
+
+const GDExtensionPropertyInfo *ScriptInstanceExtension::gdextension_script_instance_get_property_list(GDExtensionScriptInstanceDataPtr p_instance, uint32_t *r_count) {
+	ScriptInstanceExtension *instance = reinterpret_cast<ScriptInstanceExtension *>(p_instance);
+
+	instance->get_property_list(&instance->property_list);
+
+	if (instance->property_list.size() == 0) {
+		*r_count = 0;
+		return nullptr;
+	}
+
+	*r_count = instance->property_list.size();
+	GDExtensionPropertyInfo *property_array = memnew_arr(GDExtensionPropertyInfo, instance->property_list.size());
+
+	int index = 0;
+	for (const PropertyInfo &prop : instance->property_list) {
+		// @todo Do we need to allocate memory for the String and StringName pointers so the memory remains valid?
+		property_array[index] = prop._to_gdextension();
+		index++;
+	}
+
+	return property_array;
+}
+
+void ScriptInstanceExtension::gdextension_script_instance_free_property_list(GDExtensionScriptInstanceDataPtr p_instance, const GDExtensionPropertyInfo *p_list, uint32_t p_count) {
+	ScriptInstanceExtension *instance = reinterpret_cast<ScriptInstanceExtension *>(p_instance);
+	memfree((void *)p_list);
+	instance->property_list.clear();
+}
+
+GDExtensionVariantType ScriptInstanceExtension::gdextension_script_instance_get_property_type(GDExtensionScriptInstanceDataPtr p_instance, GDExtensionConstStringNamePtr p_name, GDExtensionBool *r_is_valid) {
+	ScriptInstanceExtension *instance = reinterpret_cast<ScriptInstanceExtension *>(p_instance);
+	const StringName *name = reinterpret_cast<const StringName *>(p_name);
+
+	bool is_valid;
+	GDExtensionVariantType ret = (GDExtensionVariantType)instance->get_property_type(*name, &is_valid);
+	*r_is_valid = is_valid;
+
+	return ret;
+}
+
+GDExtensionBool ScriptInstanceExtension::gdextension_script_instance_validate_property(GDExtensionScriptInstanceDataPtr p_instance, GDExtensionPropertyInfo *p_property) {
+	ScriptInstanceExtension *instance = reinterpret_cast<ScriptInstanceExtension *>(p_instance);
+
+	PropertyInfo property(p_property);
+	instance->validate_property(property);
+
+	*p_property = property._to_gdextension();
+
+	return true;
+}
+
+GDExtensionBool ScriptInstanceExtension::gdextension_script_instance_property_can_revert(GDExtensionScriptInstanceDataPtr p_instance, GDExtensionConstStringNamePtr p_name) {
+	ScriptInstanceExtension *instance = reinterpret_cast<ScriptInstanceExtension *>(p_instance);
+	const StringName *name = reinterpret_cast<const StringName *>(p_name);
+
+	return instance->property_can_revert(*name);
+}
+
+GDExtensionBool ScriptInstanceExtension::gdextension_script_instance_property_get_revert(GDExtensionScriptInstanceDataPtr p_instance, GDExtensionConstStringNamePtr p_name, GDExtensionVariantPtr r_ret) {
+	ScriptInstanceExtension *instance = reinterpret_cast<ScriptInstanceExtension *>(p_instance);
+	const StringName *name = reinterpret_cast<const StringName *>(p_name);
+	Variant *ret = reinterpret_cast<Variant *>(r_ret);
+
+	return instance->property_get_revert(*name, *ret);
+}
+
+GDExtensionObjectPtr ScriptInstanceExtension::gdextension_script_instance_get_owner(GDExtensionScriptInstanceDataPtr p_instance) {
+	ScriptInstanceExtension *instance = reinterpret_cast<ScriptInstanceExtension *>(p_instance);
+
+	Object *ret = instance->get_owner();
+	return ret->_owner;
+}
+
+void ScriptInstanceExtension::gdextension_script_instance_get_property_state(GDExtensionScriptInstanceDataPtr p_instance, GDExtensionScriptInstancePropertyStateAdd p_add_func, void *p_userdata) {
+	ScriptInstanceExtension *instance = reinterpret_cast<ScriptInstanceExtension *>(p_instance);
+
+	List<Pair<StringName, Variant>> property_state;
+	instance->get_property_state(property_state);
+
+	for (const Pair<StringName, Variant> &state : property_state) {
+		p_add_func(state.first._native_ptr(), state.second._native_ptr(), p_userdata);
+	}
+}
+
+const GDExtensionMethodInfo *ScriptInstanceExtension::gdextension_script_instance_get_method_list(GDExtensionScriptInstanceDataPtr p_instance, uint32_t *r_count) {
+	ScriptInstanceExtension *instance = reinterpret_cast<ScriptInstanceExtension *>(p_instance);
+
+	List<MethodInfo> methods;
+	instance->get_method_list(&methods);
+
+	if (methods.size() == 0) {
+		*r_count = 0;
+		return nullptr;
+	}
+
+	*r_count = methods.size();
+	GDExtensionMethodInfo *method_array = memnew_arr(GDExtensionMethodInfo, methods.size());
+
+	int index = 0;
+	for (const MethodInfo &method : methods) {
+		method_array[index].name = method.name._native_ptr();
+		method_array[index].return_value = method.return_val._to_gdextension();
+		method_array[index].flags = method.flags;
+		method_array[index].id = method.id;
+		method_array[index].argument_count = method.arguments.size();
+		method_array[index].arguments = memnew_arr(GDExtensionPropertyInfo, method.arguments.size());
+		for (int n = 0; n < method.arguments.size(); n++) {
+			method_array[index].arguments[n] = method.arguments[n]._to_gdextension();
+		}
+		method_array[index].default_argument_count = method.default_arguments.size();
+		method_array[index].default_arguments = memnew_arr(GDExtensionVariantPtr, method.default_arguments.size());
+		for (int n = 0; n < method.default_arguments.size(); n++) {
+			method_array[index].default_arguments[n] = method.default_arguments[n]._native_ptr();
+		}
+
+		index++;
+	}
+
+	return method_array;
+}
+
+void ScriptInstanceExtension::gdextension_script_instance_free_method_list(GDExtensionScriptInstanceDataPtr p_instance, const GDExtensionMethodInfo *p_list, uint32_t p_count) {
+	ScriptInstanceExtension *instance = reinterpret_cast<ScriptInstanceExtension *>(p_instance);
+	for (int i = 0; i < p_count; i++) {
+		memfree(p_list[i].arguments);
+		memfree(p_list[i].default_arguments);
+	}
+	memfree((void *)p_list);
+	instance->method_list.clear();
+}
+
+GDExtensionBool ScriptInstanceExtension::gdextension_script_instance_has_method(GDExtensionScriptInstanceDataPtr p_instance, GDExtensionConstStringNamePtr p_name) {
+	ScriptInstanceExtension *instance = reinterpret_cast<ScriptInstanceExtension *>(p_instance);
+	const StringName *name = reinterpret_cast<const StringName *>(p_name);
+
+	return instance->has_method(*name);
+}
+
+GDExtensionInt ScriptInstanceExtension::gdextension_script_instance_get_method_argument_count(GDExtensionScriptInstanceDataPtr p_instance, GDExtensionConstStringNamePtr p_name, GDExtensionBool *r_is_valid) {
+	ScriptInstanceExtension *instance = reinterpret_cast<ScriptInstanceExtension *>(p_instance);
+	const StringName *name = reinterpret_cast<const StringName *>(p_name);
+
+	bool is_valid;
+	GDExtensionInt ret = instance->get_method_argument_count(*name, &is_valid);
+	*r_is_valid = is_valid;
+
+	return ret;
+}
+
+void ScriptInstanceExtension::gdextension_script_instance_call(GDExtensionScriptInstanceDataPtr p_instance, GDExtensionConstStringNamePtr p_method, const GDExtensionConstVariantPtr *p_args, GDExtensionInt p_argument_count, GDExtensionVariantPtr r_return, GDExtensionCallError *r_error) {
+	ScriptInstanceExtension *instance = reinterpret_cast<ScriptInstanceExtension *>(p_instance);
+	const StringName *method = reinterpret_cast<const StringName *>(p_method);
+	const Variant **args = reinterpret_cast<const Variant **>(const_cast<const void **>(p_args));
+	Variant *ret = reinterpret_cast<Variant *>(r_return);
+
+	Callable::CallError error;
+	*ret = instance->callp(*method, args, p_argument_count, error);
+
+	r_error->error = (GDExtensionCallErrorType)error.error;
+	r_error->argument = error.argument;
+	r_error->expected = error.expected;
+}
+
+void ScriptInstanceExtension::gdextension_script_instance_notification(GDExtensionScriptInstanceDataPtr p_instance, int32_t p_what, GDExtensionBool p_reversed) {
+	ScriptInstanceExtension *instance = reinterpret_cast<ScriptInstanceExtension *>(p_instance);
+	instance->notification(p_what, p_reversed);
+}
+
+void ScriptInstanceExtension::gdextension_script_instance_to_string(GDExtensionScriptInstanceDataPtr p_instance, GDExtensionBool *r_is_valid, GDExtensionStringPtr r_out) {
+	ScriptInstanceExtension *instance = reinterpret_cast<ScriptInstanceExtension *>(p_instance);
+	String *out = reinterpret_cast<String *>(r_out);
+
+	bool is_valid = false;
+	*out = instance->to_string(&is_valid);
+	*r_is_valid = is_valid;
+}
+
+void ScriptInstanceExtension::gdextension_script_instance_refcount_incremented(GDExtensionScriptInstanceDataPtr p_instance) {
+	ScriptInstanceExtension *instance = reinterpret_cast<ScriptInstanceExtension *>(p_instance);
+	instance->refcount_incremented();
+}
+
+GDExtensionBool ScriptInstanceExtension::gdextension_script_instance_refcount_decremented(GDExtensionScriptInstanceDataPtr p_instance) {
+	ScriptInstanceExtension *instance = reinterpret_cast<ScriptInstanceExtension *>(p_instance);
+	return instance->refcount_decremented();
+}
+
+GDExtensionObjectPtr ScriptInstanceExtension::gdextension_script_instance_get_script(GDExtensionScriptInstanceDataPtr p_instance) {
+	ScriptInstanceExtension *instance = reinterpret_cast<ScriptInstanceExtension *>(p_instance);
+	return instance->get_script()->_owner;
+}
+
+GDExtensionBool ScriptInstanceExtension::gdextension_script_instance_is_placeholder(GDExtensionScriptInstanceDataPtr p_instance) {
+	ScriptInstanceExtension *instance = reinterpret_cast<ScriptInstanceExtension *>(p_instance);
+	return instance->is_placeholder();
+}
+
+GDExtensionBool ScriptInstanceExtension::gdextension_script_instance_set_fallback(GDExtensionScriptInstanceDataPtr p_instance, GDExtensionConstStringNamePtr p_name, GDExtensionConstVariantPtr p_value) {
+	ScriptInstanceExtension *instance = reinterpret_cast<ScriptInstanceExtension *>(p_instance);
+	const StringName *name = reinterpret_cast<const StringName *>(p_name);
+	const Variant *value = reinterpret_cast<const Variant *>(p_value);
+
+	bool is_valid = false;
+	instance->property_set_fallback(*name, *value, &is_valid);
+	return is_valid;
+}
+
+GDExtensionBool ScriptInstanceExtension::gdextension_script_instance_get_fallback(GDExtensionScriptInstanceDataPtr p_instance, GDExtensionConstStringNamePtr p_name, GDExtensionVariantPtr r_ret) {
+	ScriptInstanceExtension *instance = reinterpret_cast<ScriptInstanceExtension *>(p_instance);
+	const StringName *name = reinterpret_cast<const StringName *>(p_name);
+	Variant *ret = reinterpret_cast<Variant *>(r_ret);
+
+	bool is_valid = false;
+	instance->property_get_fallback(*name, &is_valid);
+	return is_valid;
+}
+
+GDExtensionScriptLanguagePtr ScriptInstanceExtension::gdextension_script_instance_get_language(GDExtensionScriptInstanceDataPtr p_instance) {
+	ScriptInstanceExtension *instance = reinterpret_cast<ScriptInstanceExtension *>(p_instance);
+	return instance->get_language()->_owner;
+}
+
+void ScriptInstanceExtension::gdextension_script_instance_free(GDExtensionScriptInstanceDataPtr p_instance) {
+	if (p_instance) {
+		ScriptInstanceExtension *instance = reinterpret_cast<ScriptInstanceExtension *>(p_instance);
+		memdelete(instance);
+	}
+}
+
+thread_local List<PropertyInfo> ScriptInstanceExtension::property_list;
+thread_local List<MethodInfo> ScriptInstanceExtension::method_list;
+
+GDExtensionScriptInstanceInfo3 ScriptInstanceExtension::script_instance_info = {
+	&ScriptInstanceExtension::gdextension_script_instance_set,
+	&ScriptInstanceExtension::gdextension_script_instance_get,
+	&ScriptInstanceExtension::gdextension_script_instance_get_property_list,
+	&ScriptInstanceExtension::gdextension_script_instance_free_property_list,
+	// We omit get_class_category_func for parity with Godot modules, which aren't able to
+	// customize the category from the ScriptInstance - only the Script - which is what happens
+	// if we omit this.
+	nullptr,
+	&ScriptInstanceExtension::gdextension_script_instance_property_can_revert,
+	&ScriptInstanceExtension::gdextension_script_instance_property_get_revert,
+	&ScriptInstanceExtension::gdextension_script_instance_get_owner,
+	&ScriptInstanceExtension::gdextension_script_instance_get_property_state,
+	&ScriptInstanceExtension::gdextension_script_instance_get_method_list,
+	&ScriptInstanceExtension::gdextension_script_instance_free_method_list,
+	&ScriptInstanceExtension::gdextension_script_instance_get_property_type,
+	&ScriptInstanceExtension::gdextension_script_instance_validate_property,
+	&ScriptInstanceExtension::gdextension_script_instance_has_method,
+	&ScriptInstanceExtension::gdextension_script_instance_get_method_argument_count,
+	&ScriptInstanceExtension::gdextension_script_instance_call,
+	&ScriptInstanceExtension::gdextension_script_instance_notification,
+	&ScriptInstanceExtension::gdextension_script_instance_to_string,
+	&ScriptInstanceExtension::gdextension_script_instance_refcount_incremented,
+	&ScriptInstanceExtension::gdextension_script_instance_refcount_decremented,
+	&ScriptInstanceExtension::gdextension_script_instance_get_script,
+	&ScriptInstanceExtension::gdextension_script_instance_is_placeholder,
+	&ScriptInstanceExtension::gdextension_script_instance_set_fallback,
+	&ScriptInstanceExtension::gdextension_script_instance_get_fallback,
+	&ScriptInstanceExtension::gdextension_script_instance_get_language,
+	&ScriptInstanceExtension::gdextension_script_instance_free,
+};