diff --git a/.changeset/stupid-wasps-fold.md b/.changeset/stupid-wasps-fold.md
new file mode 100644
index 0000000000..260dd9f5f1
--- /dev/null
+++ b/.changeset/stupid-wasps-fold.md
@@ -0,0 +1,5 @@
+---
+'@backstage/core-compat-api': patch
+---
+
+Updates for compatibility with the new extension IDs.
diff --git a/packages/core-compat-api/src/collectLegacyRoutes.test.tsx b/packages/core-compat-api/src/collectLegacyRoutes.test.tsx
index d09911b39d..1238fbbcb4 100644
--- a/packages/core-compat-api/src/collectLegacyRoutes.test.tsx
+++ b/packages/core-compat-api/src/collectLegacyRoutes.test.tsx
@@ -51,13 +51,13 @@ describe('collectLegacyRoutes', () => {
         id: 'score-card',
         extensions: [
           {
-            id: 'plugin.score-card.page',
-            attachTo: { id: 'core.routes', input: 'routes' },
+            id: 'page:score-card',
+            attachTo: { id: 'core/routes', input: 'routes' },
             disabled: false,
             defaultConfig: { path: 'score-board' },
           },
           {
-            id: 'apis.plugin.scoringdata.service',
+            id: 'api:score-card',
             attachTo: { id: 'core', input: 'apis' },
             disabled: false,
           },
@@ -67,13 +67,13 @@ describe('collectLegacyRoutes', () => {
         id: 'stackstorm',
         extensions: [
           {
-            id: 'plugin.stackstorm.page',
-            attachTo: { id: 'core.routes', input: 'routes' },
+            id: 'page:stackstorm',
+            attachTo: { id: 'core/routes', input: 'routes' },
             disabled: false,
             defaultConfig: { path: 'stackstorm' },
           },
           {
-            id: 'apis.plugin.stackstorm.service',
+            id: 'api:stackstorm',
             attachTo: { id: 'core', input: 'apis' },
             disabled: false,
           },
@@ -83,19 +83,19 @@ describe('collectLegacyRoutes', () => {
         id: 'puppetDb',
         extensions: [
           {
-            id: 'plugin.puppetDb.page',
-            attachTo: { id: 'core.routes', input: 'routes' },
+            id: 'page:puppetDb',
+            attachTo: { id: 'core/routes', input: 'routes' },
             disabled: false,
             defaultConfig: { path: 'puppetdb' },
           },
           {
-            id: 'plugin.puppetDb.page2',
-            attachTo: { id: 'core.routes', input: 'routes' },
+            id: 'page:puppetDb/2',
+            attachTo: { id: 'core/routes', input: 'routes' },
             disabled: false,
             defaultConfig: { path: 'puppetdb' },
           },
           {
-            id: 'apis.plugin.puppetdb.service',
+            id: 'api:puppetDb',
             attachTo: { id: 'core', input: 'apis' },
             disabled: false,
           },
diff --git a/packages/core-compat-api/src/collectLegacyRoutes.tsx b/packages/core-compat-api/src/collectLegacyRoutes.tsx
index 037107bfda..764149948d 100644
--- a/packages/core-compat-api/src/collectLegacyRoutes.tsx
+++ b/packages/core-compat-api/src/collectLegacyRoutes.tsx
@@ -16,11 +16,11 @@
 
 import React, { ReactNode } from 'react';
 import {
-  Extension,
   createApiExtension,
   createPageExtension,
   createPlugin,
   BackstagePlugin,
+  ExtensionDefinition,
 } from '@backstage/frontend-plugin-api';
 import { Route, Routes } from 'react-router-dom';
 import {
@@ -64,7 +64,7 @@ export function collectLegacyRoutes(
 ): BackstagePlugin[] {
   const createdPluginIds = new Map<
     LegacyBackstagePlugin,
-    Extension<unknown>[]
+    ExtensionDefinition<unknown>[]
   >();
 
   React.Children.forEach(
@@ -95,19 +95,18 @@ export function collectLegacyRoutes(
         'core.mountPoint',
       );
 
-      const pluginId = plugin.getId();
-
       const detectedExtensions =
-        createdPluginIds.get(plugin) ?? new Array<Extension<unknown>>();
+        createdPluginIds.get(plugin) ??
+        new Array<ExtensionDefinition<unknown>>();
       createdPluginIds.set(plugin, detectedExtensions);
 
       const path: string = route.props.path;
 
       detectedExtensions.push(
         createPageExtension({
-          id: `plugin.${pluginId}.page${
-            detectedExtensions.length ? detectedExtensions.length + 1 : ''
-          }`,
+          name: detectedExtensions.length
+            ? String(detectedExtensions.length + 1)
+            : undefined,
           defaultPath: path[0] === '/' ? path.slice(1) : path,
           routeRef: routeRef ? convertLegacyRouteRef(routeRef) : undefined,
 
@@ -131,9 +130,10 @@ export function collectLegacyRoutes(
       id: plugin.getId(),
       extensions: [
         ...extensions,
-        ...Array.from(plugin.getApis()).map(factory =>
+        ...Array.from(plugin.getApis()).map((factory, index) =>
           createApiExtension({
             factory,
+            name: index > 0 ? String(index + 1) : undefined,
           }),
         ),
       ],
diff --git a/packages/core-compat-api/src/convertLegacyApp.test.tsx b/packages/core-compat-api/src/convertLegacyApp.test.tsx
index 0f1f6145c9..eeb53ad998 100644
--- a/packages/core-compat-api/src/convertLegacyApp.test.tsx
+++ b/packages/core-compat-api/src/convertLegacyApp.test.tsx
@@ -59,13 +59,13 @@ describe('convertLegacyApp', () => {
         id: 'score-card',
         extensions: [
           {
-            id: 'plugin.score-card.page',
-            attachTo: { id: 'core.routes', input: 'routes' },
+            id: 'page:score-card',
+            attachTo: { id: 'core/routes', input: 'routes' },
             disabled: false,
             defaultConfig: { path: 'score-board' },
           },
           {
-            id: 'apis.plugin.scoringdata.service',
+            id: 'api:score-card',
             attachTo: { id: 'core', input: 'apis' },
             disabled: false,
           },
@@ -75,13 +75,13 @@ describe('convertLegacyApp', () => {
         id: 'stackstorm',
         extensions: [
           {
-            id: 'plugin.stackstorm.page',
-            attachTo: { id: 'core.routes', input: 'routes' },
+            id: 'page:stackstorm',
+            attachTo: { id: 'core/routes', input: 'routes' },
             disabled: false,
             defaultConfig: { path: 'stackstorm' },
           },
           {
-            id: 'apis.plugin.stackstorm.service',
+            id: 'api:stackstorm',
             attachTo: { id: 'core', input: 'apis' },
             disabled: false,
           },
@@ -91,19 +91,19 @@ describe('convertLegacyApp', () => {
         id: 'puppetDb',
         extensions: [
           {
-            id: 'plugin.puppetDb.page',
-            attachTo: { id: 'core.routes', input: 'routes' },
+            id: 'page:puppetDb',
+            attachTo: { id: 'core/routes', input: 'routes' },
             disabled: false,
             defaultConfig: { path: 'puppetdb' },
           },
           {
-            id: 'plugin.puppetDb.page2',
-            attachTo: { id: 'core.routes', input: 'routes' },
+            id: 'page:puppetDb/2',
+            attachTo: { id: 'core/routes', input: 'routes' },
             disabled: false,
             defaultConfig: { path: 'puppetdb' },
           },
           {
-            id: 'apis.plugin.puppetdb.service',
+            id: 'api:puppetDb',
             attachTo: { id: 'core', input: 'apis' },
             disabled: false,
           },
@@ -113,13 +113,13 @@ describe('convertLegacyApp', () => {
         id: undefined,
         extensions: [
           {
-            id: 'core.layout',
+            id: 'core/layout',
             attachTo: { id: 'core', input: 'root' },
             disabled: false,
           },
           {
-            id: 'core.nav',
-            attachTo: { id: 'core.layout', input: 'nav' },
+            id: 'core/nav',
+            attachTo: { id: 'core/layout', input: 'nav' },
             disabled: true,
           },
         ],
diff --git a/packages/core-compat-api/src/convertLegacyApp.ts b/packages/core-compat-api/src/convertLegacyApp.ts
index 93521b3955..3b12f0e1fd 100644
--- a/packages/core-compat-api/src/convertLegacyApp.ts
+++ b/packages/core-compat-api/src/convertLegacyApp.ts
@@ -100,7 +100,8 @@ export function convertLegacyApp(
   const [routesEl] = routesEls;
 
   const CoreLayoutOverride = createExtension({
-    id: 'core.layout',
+    namespace: 'core',
+    name: 'layout',
     attachTo: { id: 'core', input: 'root' },
     inputs: {
       content: createExtensionInput(
@@ -121,8 +122,9 @@ export function convertLegacyApp(
     },
   });
   const CoreNavOverride = createExtension({
-    id: 'core.nav',
-    attachTo: { id: 'core.layout', input: 'nav' },
+    namespace: 'core',
+    name: 'nav',
+    attachTo: { id: 'core/layout', input: 'nav' },
     output: {},
     factory: () => ({}),
     disabled: true,