diff --git a/packages/core-compat-api/src/collectEntityPageContents.test.tsx b/packages/core-compat-api/src/collectEntityPageContents.test.tsx
new file mode 100644
index 0000000000..53aa90f247
--- /dev/null
+++ b/packages/core-compat-api/src/collectEntityPageContents.test.tsx
@@ -0,0 +1,171 @@
+/*
+ * Copyright 2025 The Backstage Authors
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+import { ExtensionAttachToSpec } from '@backstage/frontend-plugin-api';
+import { EntityLayout, EntitySwitch, isKind } from '@backstage/plugin-catalog';
+import React from 'react';
+import { collectEntityPageContents } from './collectEntityPageContents';
+import {
+  createComponentExtension,
+  createPlugin,
+} from '@backstage/core-plugin-api';
+// eslint-disable-next-line @backstage/no-relative-monorepo-imports
+import {
+  resolveExtensionDefinition,
+  toInternalExtension,
+} from '../../frontend-plugin-api/src/wiring/resolveExtensionDefinition';
+
+const fooPlugin = createPlugin({
+  id: 'foo',
+});
+
+const FooContent = fooPlugin.provide(
+  createComponentExtension({
+    name: 'FooContent',
+    component: { sync: () => <div>foo content</div> },
+  }),
+);
+const OtherFooContent = fooPlugin.provide(
+  createComponentExtension({
+    name: 'OtherFooContent',
+    component: { sync: () => <div>other foo content</div> },
+  }),
+);
+
+const simpleTestContent = (
+  <EntityLayout>
+    <EntityLayout.Route path="/" title="Overview">
+      <div>overview content</div>
+    </EntityLayout.Route>
+    <EntityLayout.Route path="/foo" title="Foo">
+      <FooContent />
+    </EntityLayout.Route>
+    <EntityLayout.Route path="/bar" title="Bar">
+      <div>bar content</div>
+    </EntityLayout.Route>
+  </EntityLayout>
+);
+
+const otherTestContent = (
+  <EntityLayout>
+    <EntityLayout.Route path="/" title="Overview">
+      <div>other overview content</div>
+    </EntityLayout.Route>
+    <EntityLayout.Route path="/foo" title="Foo">
+      <OtherFooContent />
+    </EntityLayout.Route>
+  </EntityLayout>
+);
+
+function collect(element: React.JSX.Element) {
+  const result = new Array<{
+    id: string;
+    attachTo: ExtensionAttachToSpec;
+  }>();
+
+  collectEntityPageContents(element, {
+    discoverExtension(extension, plugin) {
+      const ext = toInternalExtension(
+        resolveExtensionDefinition(extension, {
+          namespace: plugin?.getId() ?? 'test',
+        }),
+      );
+      result.push({ id: ext.id, attachTo: ext.attachTo });
+    },
+  });
+  return result;
+}
+
+describe('collectEntityPageContents', () => {
+  it('should collect contents from a simple entity page', () => {
+    expect(collect(simpleTestContent)).toMatchInlineSnapshot(`
+      [
+        {
+          "attachTo": {
+            "id": "entity-content:catalog/overview",
+            "input": "cards",
+          },
+          "id": "entity-card:test/discovered-1",
+        },
+        {
+          "attachTo": {
+            "id": "page:catalog/entity",
+            "input": "contents",
+          },
+          "id": "entity-content:foo/discovered-1",
+        },
+        {
+          "attachTo": {
+            "id": "page:catalog/entity",
+            "input": "contents",
+          },
+          "id": "entity-content:test/discovered-2",
+        },
+      ]
+    `);
+  });
+
+  it('should collect contents from an entity page with an entity switch', () => {
+    expect(
+      collect(
+        <EntitySwitch>
+          <EntitySwitch.Case if={isKind('test')}>
+            {simpleTestContent}
+          </EntitySwitch.Case>
+          <EntitySwitch.Case>{otherTestContent}</EntitySwitch.Case>
+        </EntitySwitch>,
+      ),
+    ).toMatchInlineSnapshot(`
+      [
+        {
+          "attachTo": {
+            "id": "entity-content:catalog/overview",
+            "input": "cards",
+          },
+          "id": "entity-card:test/discovered-1",
+        },
+        {
+          "attachTo": {
+            "id": "page:catalog/entity",
+            "input": "contents",
+          },
+          "id": "entity-content:foo/discovered-1",
+        },
+        {
+          "attachTo": {
+            "id": "page:catalog/entity",
+            "input": "contents",
+          },
+          "id": "entity-content:test/discovered-2",
+        },
+        {
+          "attachTo": {
+            "id": "entity-content:catalog/overview",
+            "input": "cards",
+          },
+          "id": "entity-card:test/discovered-2",
+        },
+        {
+          "attachTo": {
+            "id": "page:catalog/entity",
+            "input": "contents",
+          },
+          "id": "entity-content:foo/discovered-3",
+        },
+      ]
+    `);
+  });
+});
diff --git a/packages/core-compat-api/src/collectEntityPageContents.ts b/packages/core-compat-api/src/collectEntityPageContents.ts
index c2a3ba2145..7c26cd29ef 100644
--- a/packages/core-compat-api/src/collectEntityPageContents.ts
+++ b/packages/core-compat-api/src/collectEntityPageContents.ts
@@ -74,7 +74,7 @@ function invertFilter(ifFunc?: EntityFilter): EntityFilter {
 export function collectEntityPageContents(
   entityPageElement: React.JSX.Element,
   context: {
-    discoveryExtension(
+    discoverExtension(
       extension: ExtensionDefinition,
       plugin?: LegacyBackstagePlugin,
     ): void;
@@ -94,7 +94,7 @@ export function collectEntityPageContents(
         const mergedIf = allFilters(parentFilter, pageNode.if);
 
         if (pageNode.path === '/') {
-          context.discoveryExtension(
+          context.discoverExtension(
             EntityCardBlueprint.makeWithOverrides({
               name: `discovered-${cardCounter++}`,
               factory(originalFactory, { apis }) {
@@ -109,7 +109,7 @@ export function collectEntityPageContents(
         } else {
           const name = `discovered-${routeCounter++}`;
 
-          context.discoveryExtension(
+          context.discoverExtension(
             EntityContentBlueprint.makeWithOverrides({
               name,
               factory(originalFactory, { apis }) {
diff --git a/packages/core-compat-api/src/collectLegacyRoutes.test.tsx b/packages/core-compat-api/src/collectLegacyRoutes.test.tsx
index ce0b055c00..2d64f88535 100644
--- a/packages/core-compat-api/src/collectLegacyRoutes.test.tsx
+++ b/packages/core-compat-api/src/collectLegacyRoutes.test.tsx
@@ -57,7 +57,7 @@ describe('collectLegacyRoutes', () => {
 
     expect(
       collected.map(p => ({
-        id: p.id,
+        id: p.$$type === '@backstage/FrontendPlugin' ? p.id : p.pluginId,
         extensions: OpaqueFrontendPlugin.toInternal(p).extensions.map(e => ({
           id: e.id,
           attachTo: e.attachTo,
@@ -177,7 +177,7 @@ describe('collectLegacyRoutes', () => {
 
     expect(
       collected.map(p => ({
-        id: p.id,
+        id: p.$$type === '@backstage/FrontendPlugin' ? p.id : p.pluginId,
         extensions: OpaqueFrontendPlugin.toInternal(p).extensions.map(e => ({
           id: e.id,
           attachTo: e.attachTo,
diff --git a/packages/core-compat-api/src/collectLegacyRoutes.tsx b/packages/core-compat-api/src/collectLegacyRoutes.tsx
index 3cf16b96c0..f6408b8b3f 100644
--- a/packages/core-compat-api/src/collectLegacyRoutes.tsx
+++ b/packages/core-compat-api/src/collectLegacyRoutes.tsx
@@ -270,7 +270,7 @@ export function collectLegacyRoutes(
 
   if (entityPage) {
     collectEntityPageContents(entityPage, {
-      discoveryExtension(extension, plugin) {
+      discoverExtension(extension, plugin) {
         if (!plugin || plugin.getId() === 'catalog') {
           getPluginExtensions(orphanRoutesPlugin).push(extension);
         } else {
diff --git a/packages/core-compat-api/src/convertLegacyApp.test.tsx b/packages/core-compat-api/src/convertLegacyApp.test.tsx
index 7153fcb4be..c532c6da1a 100644
--- a/packages/core-compat-api/src/convertLegacyApp.test.tsx
+++ b/packages/core-compat-api/src/convertLegacyApp.test.tsx
@@ -21,6 +21,16 @@ import { ScoreBoardPage } from '@oriflame/backstage-plugin-score-card';
 import React, { ReactNode } from 'react';
 import { Route } from 'react-router-dom';
 import { convertLegacyApp } from './convertLegacyApp';
+import {
+  createApiFactory,
+  createComponentExtension,
+  createPlugin,
+} from '@backstage/core-plugin-api';
+import { EntityLayout, EntitySwitch, isKind } from '@backstage/plugin-catalog';
+import { renderInTestApp } from '@backstage/frontend-test-utils';
+import { default as catalogPlugin } from '@backstage/plugin-catalog/alpha';
+import { catalogApiRef } from '@backstage/plugin-catalog-react';
+import { catalogApiMock } from '@backstage/plugin-catalog-react/testUtils';
 
 const Root = ({ children }: { children: ReactNode }) => <>{children}</>;
 
@@ -159,4 +169,153 @@ describe('convertLegacyApp', () => {
       }),
     ]);
   });
+
+  it('should convert entity pages', async () => {
+    const fooPlugin = createPlugin({
+      id: 'foo',
+    });
+
+    const FooContent = fooPlugin.provide(
+      createComponentExtension({
+        name: 'FooContent',
+        component: { sync: () => <div>foo content</div> },
+      }),
+    );
+    const OtherFooContent = fooPlugin.provide(
+      createComponentExtension({
+        name: 'OtherFooContent',
+        component: { sync: () => <div>other foo content</div> },
+      }),
+    );
+
+    const simpleTestContent = (
+      <EntityLayout>
+        <EntityLayout.Route path="/" title="Overview">
+          <div>overview content</div>
+        </EntityLayout.Route>
+        <EntityLayout.Route path="/foo" title="Foo">
+          <FooContent />
+        </EntityLayout.Route>
+        <EntityLayout.Route path="/bar" title="Bar">
+          <div>bar content</div>
+        </EntityLayout.Route>
+      </EntityLayout>
+    );
+
+    const otherTestContent = (
+      <EntityLayout>
+        <EntityLayout.Route path="/" title="Overview">
+          <div>other overview content</div>
+        </EntityLayout.Route>
+        <EntityLayout.Route path="/foo" title="Foo">
+          <OtherFooContent />
+        </EntityLayout.Route>
+      </EntityLayout>
+    );
+
+    const entityPage = (
+      <EntitySwitch>
+        <EntitySwitch.Case if={isKind('test')}>
+          {simpleTestContent}
+        </EntitySwitch.Case>
+        <EntitySwitch.Case>{otherTestContent}</EntitySwitch.Case>
+      </EntitySwitch>
+    );
+
+    const converted = convertLegacyApp(
+      <FlatRoutes>
+        <Route path="/test" element={<div>test</div>} />
+      </FlatRoutes>,
+      { entityPage },
+    );
+
+    const catalogOverride = catalogPlugin.withOverrides({
+      extensions: [
+        catalogPlugin.getExtension('api:catalog').override({
+          params: {
+            factory: createApiFactory(
+              catalogApiRef,
+              catalogApiMock({
+                entities: [
+                  {
+                    apiVersion: 'backstage.io/v1alpha1',
+                    kind: 'test',
+                    metadata: {
+                      name: 'x',
+                    },
+                    spec: {},
+                  },
+                  {
+                    apiVersion: 'backstage.io/v1alpha1',
+                    kind: 'other',
+                    metadata: {
+                      name: 'x',
+                    },
+                    spec: {},
+                  },
+                ],
+              }),
+            ),
+          },
+        }),
+      ],
+    });
+
+    // Overview
+    const renderOverviewTest = await renderInTestApp(<div />, {
+      features: [catalogOverride, ...converted],
+      initialRouteEntries: ['/catalog/default/test/x'],
+    });
+    await expect(
+      renderOverviewTest.findByText('overview content'),
+    ).resolves.toBeInTheDocument();
+    renderOverviewTest.unmount();
+
+    const renderOverviewOther = await renderInTestApp(<div />, {
+      features: [catalogOverride, ...converted],
+      initialRouteEntries: ['/catalog/default/other/x'],
+    });
+    await expect(
+      renderOverviewOther.findByText('other overview content'),
+    ).resolves.toBeInTheDocument();
+    renderOverviewOther.unmount();
+
+    // Foo tab
+    const renderFooTest = await renderInTestApp(<div />, {
+      features: [catalogOverride, ...converted],
+      initialRouteEntries: ['/catalog/default/test/x/foo'],
+    });
+    await expect(
+      renderFooTest.findByText('foo content'),
+    ).resolves.toBeInTheDocument();
+    renderFooTest.unmount();
+
+    const renderFooOther = await renderInTestApp(<div />, {
+      features: [catalogOverride, ...converted],
+      initialRouteEntries: ['/catalog/default/other/x/foo'],
+    });
+    await expect(
+      renderFooOther.findByText('other foo content'),
+    ).resolves.toBeInTheDocument();
+    renderFooOther.unmount();
+
+    // Bar tab
+    const renderBarTest = await renderInTestApp(<div />, {
+      features: [catalogOverride, ...converted],
+      initialRouteEntries: ['/catalog/default/test/x/bar'],
+    });
+    await expect(
+      renderBarTest.findByText('bar content'),
+    ).resolves.toBeInTheDocument();
+    renderBarTest.unmount();
+
+    const renderBarOther = await renderInTestApp(<div />, {
+      features: [catalogOverride, ...converted],
+      initialRouteEntries: ['/catalog/default/other/x/bar'],
+    });
+    await expect(
+      renderBarOther.findByText('other overview content'),
+    ).resolves.toBeInTheDocument(); // /bar does not exist, fall back to rendering overview
+    renderBarOther.unmount();
+  });
 });
diff --git a/packages/core-compat-api/src/convertLegacyApp.ts b/packages/core-compat-api/src/convertLegacyApp.ts
index eb72cda204..dac9849aac 100644
--- a/packages/core-compat-api/src/convertLegacyApp.ts
+++ b/packages/core-compat-api/src/convertLegacyApp.ts
@@ -86,7 +86,7 @@ export function convertLegacyApp(
   options: ConvertLegacyAppOptions = {},
 ): (FrontendPlugin | FrontendModule)[] {
   if (getComponentData(rootElement, 'core.type') === 'FlatRoutes') {
-    return collectLegacyRoutes(rootElement);
+    return collectLegacyRoutes(rootElement, options?.entityPage);
   }
 
   const appRouterEls = selectChildren(