diff --git a/packages/angular/build/src/builders/library/pipeline/entry-points.ts b/packages/angular/build/src/builders/library/pipeline/entry-points.ts
index f50824c5d9f3..f932fb992fc6 100644
--- a/packages/angular/build/src/builders/library/pipeline/entry-points.ts
+++ b/packages/angular/build/src/builders/library/pipeline/entry-points.ts
@@ -7,7 +7,7 @@
  */
 
 import path from 'node:path';
-import { toPosixPath } from '../../../utils/path';
+import { isSubDirectory, toPosixPath } from '../../../utils/path';
 import type { BuilderState } from '../builder-state';
 import type { NormalizedEntryPoint, NormalizedLibraryOptions, PackageJsonData } from '../types';
 import type { BundleEntryPointInput } from './bundler';
@@ -55,11 +55,17 @@ function normalizeEntryPoint(
   }
 
   const subpath = isPrimary ? '.' : `./${name}`;
-  const displayName = (isPrimary ? packageName : `${packageName}/${name}`).toLowerCase();
+  const displayName = isPrimary ? packageName : `${packageName}/${name}`;
   const bundleName = getEntryPointBundleName(packageName, name);
   const entryFilePath = toPosixPath(path.resolve(projectRoot, targetPath));
 
-  if (!/(?<!\.d)\.(?:ts|mts)$/.test(entryFilePath)) {
+  if (!isSubDirectory(projectRoot, entryFilePath)) {
+    throw new Error(
+      `Entry point '${key}' file path '${entryFilePath}' is outside the project root '${projectRoot}'.`,
+    );
+  }
+
+  if (!/(?<!\.d)\.m?ts$/.test(entryFilePath)) {
     throw new Error(
       `Entry point '${key}' file path must be a TypeScript file ('.ts' or '.mts'): '${entryFilePath}'.`,
     );
@@ -157,8 +163,8 @@ export function normalizeEntryPoints(
       continue;
     }
 
-    if (!isPrimary && !/\.m?ts$/.test(target)) {
-      // Static asset, stylesheet, or package.json export; preserve in package.json without compiling.
+    if (!isPrimary && !/(?<!\.d)\.m?ts$/.test(target)) {
+      // Static asset, stylesheet, declaration file, or package.json export; preserve in package.json without compiling.
       continue;
     }
 
diff --git a/packages/angular/build/src/builders/library/pipeline/entry-points_spec.ts b/packages/angular/build/src/builders/library/pipeline/entry-points_spec.ts
index b5b4aac20059..a63c5b7be6d1 100644
--- a/packages/angular/build/src/builders/library/pipeline/entry-points_spec.ts
+++ b/packages/angular/build/src/builders/library/pipeline/entry-points_spec.ts
@@ -240,12 +240,46 @@ describe('entry-points pipeline', () => {
       );
     });
 
-    it('should ignore non-TypeScript exports for secondary subpaths', () => {
+    it('should preserve casing in displayName while lowercasing bundleName', () => {
+      const rawExports = {
+        '.': './src/public-api.ts',
+        './myFeature': './my-feature/src/public-api.ts',
+      };
+
+      const entryPoints = normalizeEntryPoints(
+        rawExports,
+        projectRoot,
+        packageJsonPath,
+        '@My-Scope/My-Lib',
+      );
+
+      expect(entryPoints.get('.')).toEqual({
+        subpath: '.',
+        name: '.',
+        displayName: '@My-Scope/My-Lib',
+        bundleName: 'my-scope-my-lib',
+        entryFilePath: join(projectRoot, 'src/public-api.ts'),
+        isPrimary: true,
+      });
+
+      expect(entryPoints.get('myFeature')).toEqual({
+        subpath: './myFeature',
+        name: 'myFeature',
+        displayName: '@My-Scope/My-Lib/myFeature',
+        bundleName: 'my-scope-my-lib-myfeature',
+        entryFilePath: join(projectRoot, 'my-feature/src/public-api.ts'),
+        isPrimary: false,
+      });
+    });
+
+    it('should ignore non-TypeScript exports and static declaration files for secondary subpaths', () => {
       const rawExports = {
         '.': './src/public-api.ts',
         './package.json': './package.json',
         './styles.css': './styles.css',
         './theme': { sass: './theme.scss' },
+        './custom-types': './src/custom-types.d.ts',
+        './custom-esm-types': { default: './src/custom-types.d.mts' },
       };
 
       const entryPoints = normalizeEntryPoints(
@@ -260,6 +294,31 @@ describe('entry-points pipeline', () => {
       expect(entryPoints.has('package.json')).toBeFalse();
       expect(entryPoints.has('styles.css')).toBeFalse();
       expect(entryPoints.has('theme')).toBeFalse();
+      expect(entryPoints.has('custom-types')).toBeFalse();
+      expect(entryPoints.has('custom-esm-types')).toBeFalse();
+    });
+
+    it('should throw when entry point file path escapes projectRoot', () => {
+      expect(() =>
+        normalizeEntryPoints(
+          { '.': '../other-lib/src/public-api.ts' },
+          projectRoot,
+          packageJsonPath,
+          packageName,
+        ),
+      ).toThrowError(/is outside the project root/);
+
+      expect(() =>
+        normalizeEntryPoints(
+          {
+            '.': './src/public-api.ts',
+            './testing': '../../outside/public-api.ts',
+          },
+          projectRoot,
+          packageJsonPath,
+          packageName,
+        ),
+      ).toThrowError(/is outside the project root/);
     });
 
     it('should throw when exports is missing or not an object/string', () => {