diff --git a/packages/frontend-app-api/src/extensions/Core.tsx b/packages/frontend-app-api/src/extensions/Core.tsx
index 441cb5bcf0..472ed4905a 100644
--- a/packages/frontend-app-api/src/extensions/Core.tsx
+++ b/packages/frontend-app-api/src/extensions/Core.tsx
@@ -21,7 +21,7 @@ import {
 } from '@backstage/frontend-plugin-api';
 
 export const Core = createExtension({
-  id: 'core',
+  namespace: 'core',
   attachTo: { id: 'root', input: 'default' }, // ignored
   inputs: {
     apis: createExtensionInput({
diff --git a/packages/frontend-app-api/src/extensions/CoreLayout.tsx b/packages/frontend-app-api/src/extensions/CoreLayout.tsx
index 0099b67751..94681120db 100644
--- a/packages/frontend-app-api/src/extensions/CoreLayout.tsx
+++ b/packages/frontend-app-api/src/extensions/CoreLayout.tsx
@@ -23,8 +23,9 @@ import {
 import { SidebarPage } from '@backstage/core-components';
 
 export const CoreLayout = createExtension({
-  id: 'core.layout',
-  attachTo: { id: 'core.router', input: 'children' },
+  namespace: 'core',
+  name: 'layout',
+  attachTo: { id: 'core/router', input: 'children' },
   inputs: {
     nav: createExtensionInput(
       {
diff --git a/packages/frontend-app-api/src/extensions/CoreNav.tsx b/packages/frontend-app-api/src/extensions/CoreNav.tsx
index 8d0d4ea5de..21d113d3d6 100644
--- a/packages/frontend-app-api/src/extensions/CoreNav.tsx
+++ b/packages/frontend-app-api/src/extensions/CoreNav.tsx
@@ -75,8 +75,9 @@ const SidebarNavItem = (props: NavTarget) => {
 };
 
 export const CoreNav = createExtension({
-  id: 'core.nav',
-  attachTo: { id: 'core.layout', input: 'nav' },
+  namespace: 'core',
+  name: 'nav',
+  attachTo: { id: 'core/layout', input: 'nav' },
   inputs: {
     items: createExtensionInput({
       target: coreExtensionData.navTarget,
diff --git a/packages/frontend-app-api/src/extensions/CoreRouter.tsx b/packages/frontend-app-api/src/extensions/CoreRouter.tsx
index 510af04b51..088fd25ae7 100644
--- a/packages/frontend-app-api/src/extensions/CoreRouter.tsx
+++ b/packages/frontend-app-api/src/extensions/CoreRouter.tsx
@@ -36,7 +36,8 @@ import { signInPageComponentDataRef } from '../../../frontend-plugin-api/src/ext
 import { RouteTracker } from '../routing/RouteTracker';
 
 export const CoreRouter = createExtension({
-  id: 'core.router',
+  namespace: 'core',
+  name: 'router',
   attachTo: { id: 'core', input: 'root' },
   inputs: {
     signInPage: createExtensionInput(
diff --git a/packages/frontend-app-api/src/extensions/CoreRoutes.tsx b/packages/frontend-app-api/src/extensions/CoreRoutes.tsx
index 9acd27b6bf..d77839f7b3 100644
--- a/packages/frontend-app-api/src/extensions/CoreRoutes.tsx
+++ b/packages/frontend-app-api/src/extensions/CoreRoutes.tsx
@@ -26,8 +26,9 @@ import {
 import { useRoutes } from 'react-router-dom';
 
 export const CoreRoutes = createExtension({
-  id: 'core.routes',
-  attachTo: { id: 'core.layout', input: 'content' },
+  namespace: 'core',
+  name: 'routes',
+  attachTo: { id: 'core/layout', input: 'content' },
   inputs: {
     routes: createExtensionInput({
       path: coreExtensionData.routePath,
diff --git a/packages/frontend-app-api/src/wiring/createApp.tsx b/packages/frontend-app-api/src/wiring/createApp.tsx
index 4e463fb526..4671ec239d 100644
--- a/packages/frontend-app-api/src/wiring/createApp.tsx
+++ b/packages/frontend-app-api/src/wiring/createApp.tsx
@@ -73,6 +73,8 @@ import { AppLanguageSelector } from '../../../core-app-api/src/apis/implementati
 // eslint-disable-next-line @backstage/no-relative-monorepo-imports
 import { I18nextTranslationApi } from '../../../core-app-api/src/apis/implementations/TranslationApi/I18nextTranslationApi';
 // eslint-disable-next-line @backstage/no-relative-monorepo-imports
+import { resolveExtensionDefinition } from '../../../frontend-plugin-api/src/wiring/resolveExtensionDefinition';
+// eslint-disable-next-line @backstage/no-relative-monorepo-imports
 import {
   apis as defaultApis,
   components as defaultComponents,
@@ -119,7 +121,7 @@ export const builtinExtensions = [
   DefaultNotFoundErrorPageComponent,
   LightTheme,
   DarkTheme,
-];
+].map(def => resolveExtensionDefinition(def));
 
 /** @public */
 export interface ExtensionTreeNode {