From 562ec50d2bfe29d588740e7b2e49842792579055 Mon Sep 17 00:00:00 2001
From: Alan Agius <17563226+alan-agius4@users.noreply.github.com>
Date: Tue, 20 Oct 2026 10:07:35 +0000
Subject: [PATCH 1/6] fix(@angular/build): enforce library compilerOptions and
 skip unused .tsbuildinfo emit

Ensure library compilations explicitly set `noEmit: false`, `emitDeclarationOnly: false`, and `emitDecoratorMetadata: false` in `transformCompilerOptions` so that configurations extending a root `tsconfig.json` with `noEmit` or `emitDeclarationOnly` still emit both JavaScript and declaration files.

Additionally, skip the application-specific `target < ES2022` Browserslist warning and `useDefineForClassFields = false` fallback when compiling libraries, and avoid serializing and writing on-disk `.tsbuildinfo` files during library builds since library outputs are emitted into in-memory maps on cold builds and watch rebuilds reuse the in-memory `BuilderProgram` directly.
---
 .../library/tests/behavior/build_spec.ts      | 31 +++++++++++++-
 .../compilation/angular-compilation_spec.ts   | 27 ++++++++++++
 .../angular/compilation/compiler-options.ts   | 42 +++++++++++--------
 3 files changed, 81 insertions(+), 19 deletions(-)

diff --git a/packages/angular/build/src/builders/library/tests/behavior/build_spec.ts b/packages/angular/build/src/builders/library/tests/behavior/build_spec.ts
index 0b6de2a26c7f..6c7906210c31 100644
--- a/packages/angular/build/src/builders/library/tests/behavior/build_spec.ts
+++ b/packages/angular/build/src/builders/library/tests/behavior/build_spec.ts
@@ -237,7 +237,7 @@ describeLibraryBuilder(executeLibraryBuilder, LIBRARY_BUILDER_INFO, (harness) =>
       );
     });
 
-    it('should write and reuse .tsbuildinfo in the persistent cache directory when cache is enabled', async () => {
+    it('should succeed without emitting .tsbuildinfo in the persistent cache directory when cache is enabled', async () => {
       harness.useProject('lib', {
         root: 'projects/lib',
         sourceRoot: 'projects/lib/src',
@@ -258,7 +258,7 @@ describeLibraryBuilder(executeLibraryBuilder, LIBRARY_BUILDER_INFO, (harness) =>
       expect(firstBuild.result?.success).toBeTrue();
       harness
         .expectFile('.angular/cache/0.0.0-PLACEHOLDER/lib/angular-build-library/.tsbuildinfo')
-        .toExist();
+        .toNotExist();
 
       await harness.writeFile(
         'projects/lib/src/public-api.ts',
@@ -278,5 +278,32 @@ describeLibraryBuilder(executeLibraryBuilder, LIBRARY_BUILDER_INFO, (harness) =>
       expect(dtsContent).toContain('LibComponent');
       expect(dtsContent).toContain('CACHED_BUILD');
     });
+
+    it('should override noEmit and emitDeclarationOnly in tsconfig.lib.json and emit both JS and .d.ts files', async () => {
+      await harness.modifyFile('projects/lib/tsconfig.lib.json', (content) => {
+        const tsconfig = JSON.parse(content);
+        tsconfig.compilerOptions = {
+          ...tsconfig.compilerOptions,
+          noEmit: true,
+          emitDeclarationOnly: true,
+          emitDecoratorMetadata: true,
+        };
+
+        return JSON.stringify(tsconfig, null, 2);
+      });
+
+      harness.useTarget('build', {
+        ...BASE_OPTIONS,
+      });
+
+      const { result } = await harness.executeOnce();
+      expect(result?.error).toBeUndefined();
+      expect(result?.success).toBeTrue();
+
+      const fesmContent = harness.readFile('dist/lib/fesm2022/lib.mjs');
+      expect(fesmContent).toContain('LibComponent');
+      const dtsContent = harness.readFile('dist/lib/types/lib.d.ts');
+      expect(dtsContent).toContain('LibComponent');
+    });
   });
 });
diff --git a/packages/angular/build/src/tools/angular/compilation/angular-compilation_spec.ts b/packages/angular/build/src/tools/angular/compilation/angular-compilation_spec.ts
index 58c492ac5214..f253e2140bf6 100644
--- a/packages/angular/build/src/tools/angular/compilation/angular-compilation_spec.ts
+++ b/packages/angular/build/src/tools/angular/compilation/angular-compilation_spec.ts
@@ -479,5 +479,32 @@ describe('AngularCompilation', () => {
       expect(compilerOptions.noEmitOnError).toBe(false);
       expect(compilerOptions.composite).toBe(false);
     });
+
+    it('enforces library compiler options and skips app-only target warning and .tsbuildinfo', () => {
+      const { compilerOptions, warnings } = transformCompilerOptions(
+        ts,
+        {
+          target: ts.ScriptTarget.ES2020,
+          noEmit: true,
+          emitDeclarationOnly: true,
+          emitDecoratorMetadata: true,
+          isolatedModules: true,
+        },
+        {
+          cachePath: '/tmp/cache',
+        },
+        'tsconfig.lib.json',
+        'library',
+      );
+
+      expect(compilerOptions.target).toBe(ts.ScriptTarget.ES2022);
+      expect(compilerOptions.useDefineForClassFields).toBeUndefined();
+      expect(compilerOptions.noEmit).toBe(false);
+      expect(compilerOptions.emitDeclarationOnly).toBe(false);
+      expect(compilerOptions.emitDecoratorMetadata).toBe(false);
+      expect(compilerOptions.incremental).toBe(false);
+      expect(compilerOptions.tsBuildInfoFile).toBeUndefined();
+      expect(warnings).toEqual([]);
+    });
   });
 });
diff --git a/packages/angular/build/src/tools/angular/compilation/compiler-options.ts b/packages/angular/build/src/tools/angular/compilation/compiler-options.ts
index 77bfdfde2f90..22e0cff30bde 100644
--- a/packages/angular/build/src/tools/angular/compilation/compiler-options.ts
+++ b/packages/angular/build/src/tools/angular/compilation/compiler-options.ts
@@ -37,11 +37,12 @@ export function transformCompilerOptions(
 ): { compilerOptions: ng.CompilerOptions; warnings: PartialMessage[] } {
   const compilerOptions = { ...baseCompilerOptions };
   const warnings: PartialMessage[] = [];
-  const isLibrary = buildType === 'library';
+  const isLibrary = buildType === 'library' || !!baseCompilerOptions.declaration;
 
   if (
-    compilerOptions.target === undefined ||
-    compilerOptions.target < typeScript.ScriptTarget.ES2022
+    !isLibrary &&
+    (compilerOptions.target === undefined ||
+      compilerOptions.target < typeScript.ScriptTarget.ES2022)
   ) {
     // If 'useDefineForClassFields' is already defined in the users project leave the value as is.
     // Otherwise fallback to false due to https://github.com/microsoft/TypeScript/issues/45995
@@ -77,13 +78,32 @@ export function transformCompilerOptions(
     compilerOptions.compilationMode ??= 'partial';
   }
 
-  // Enable incremental compilation by default if caching is enabled and incremental is not explicitly disabled
-  if (compilerOptions.incremental !== false && overrides?.cachePath) {
+  // Enable incremental compilation by default if caching is enabled and incremental is not explicitly disabled.
+  // Library compilation does not reuse on-disk .tsbuildinfo files across builds because all JS and .d.ts
+  // outputs must be emitted into in-memory maps on every cold build, while watch mode uses in-memory
+  // BuilderProgram state directly.
+  if (!isLibrary && compilerOptions.incremental !== false && overrides?.cachePath) {
     compilerOptions.incremental = true;
     // Set the build info file location to the configured cache directory
     compilerOptions.tsBuildInfoFile = path.join(overrides.cachePath, '.tsbuildinfo');
   } else {
     compilerOptions.incremental = false;
+    compilerOptions.tsBuildInfoFile = undefined;
+  }
+
+  if (isLibrary) {
+    compilerOptions.target = typeScript.ScriptTarget.ES2022;
+    compilerOptions.module = typeScript.ModuleKind.ES2022;
+    compilerOptions.moduleResolution = typeScript.ModuleResolutionKind.Bundler;
+    compilerOptions.importHelpers = true;
+    compilerOptions.declaration = true;
+    compilerOptions.declarationMap = !!(
+      overrides?.declarationMap ?? compilerOptions.declarationMap
+    );
+    compilerOptions.declarationDir = undefined;
+    compilerOptions.noEmit = false;
+    compilerOptions.emitDeclarationOnly = false;
+    compilerOptions.emitDecoratorMetadata = false;
   }
 
   if (
@@ -112,18 +132,6 @@ export function transformCompilerOptions(
     });
   }
 
-  if (isLibrary) {
-    compilerOptions.target = typeScript.ScriptTarget.ES2022;
-    compilerOptions.module = typeScript.ModuleKind.ES2022;
-    compilerOptions.moduleResolution = typeScript.ModuleResolutionKind.Bundler;
-    compilerOptions.importHelpers = true;
-    compilerOptions.declaration = true;
-    compilerOptions.declarationMap = !!(
-      overrides?.declarationMap ?? compilerOptions.declarationMap
-    );
-    compilerOptions.declarationDir = undefined;
-  }
-
   // Synchronize custom resolve conditions.
   // Set if using the supported bundler resolution mode (bundler is the default in new projects)
   if (

From 0bc182b6cb96d2a5443e4ffa5c94ed4367f5e6bd Mon Sep 17 00:00:00 2001
From: Alan Agius <17563226+alan-agius4@users.noreply.github.com>
Date: Tue, 20 Oct 2026 10:42:06 +0000
Subject: [PATCH 2/6] fixup! fix(@angular/build): enforce library
 compilerOptions and skip unused .tsbuildinfo emit

---
 .../src/builders/library/tests/behavior/build_spec.ts     | 4 ++--
 .../tools/angular/compilation/angular-compilation_spec.ts | 7 ++++---
 .../src/tools/angular/compilation/compiler-options.ts     | 8 ++------
 3 files changed, 8 insertions(+), 11 deletions(-)

diff --git a/packages/angular/build/src/builders/library/tests/behavior/build_spec.ts b/packages/angular/build/src/builders/library/tests/behavior/build_spec.ts
index 6c7906210c31..3a4a8acbf1c6 100644
--- a/packages/angular/build/src/builders/library/tests/behavior/build_spec.ts
+++ b/packages/angular/build/src/builders/library/tests/behavior/build_spec.ts
@@ -237,7 +237,7 @@ describeLibraryBuilder(executeLibraryBuilder, LIBRARY_BUILDER_INFO, (harness) =>
       );
     });
 
-    it('should succeed without emitting .tsbuildinfo in the persistent cache directory when cache is enabled', async () => {
+    it('should write and reuse .tsbuildinfo in the persistent cache directory when cache is enabled', async () => {
       harness.useProject('lib', {
         root: 'projects/lib',
         sourceRoot: 'projects/lib/src',
@@ -258,7 +258,7 @@ describeLibraryBuilder(executeLibraryBuilder, LIBRARY_BUILDER_INFO, (harness) =>
       expect(firstBuild.result?.success).toBeTrue();
       harness
         .expectFile('.angular/cache/0.0.0-PLACEHOLDER/lib/angular-build-library/.tsbuildinfo')
-        .toNotExist();
+        .toExist();
 
       await harness.writeFile(
         'projects/lib/src/public-api.ts',
diff --git a/packages/angular/build/src/tools/angular/compilation/angular-compilation_spec.ts b/packages/angular/build/src/tools/angular/compilation/angular-compilation_spec.ts
index f253e2140bf6..3b7d790f7102 100644
--- a/packages/angular/build/src/tools/angular/compilation/angular-compilation_spec.ts
+++ b/packages/angular/build/src/tools/angular/compilation/angular-compilation_spec.ts
@@ -6,6 +6,7 @@
  * found in the LICENSE file at https://angular.dev/license
  */
 
+import path from 'node:path';
 import ts from 'typescript';
 import type { AngularHostOptions } from '../angular-host';
 import { CompilerOptionOverrides, transformCompilerOptions } from './compiler-options';
@@ -480,7 +481,7 @@ describe('AngularCompilation', () => {
       expect(compilerOptions.composite).toBe(false);
     });
 
-    it('enforces library compiler options and skips app-only target warning and .tsbuildinfo', () => {
+    it('enforces library compiler options and skips app-only target warning', () => {
       const { compilerOptions, warnings } = transformCompilerOptions(
         ts,
         {
@@ -502,8 +503,8 @@ describe('AngularCompilation', () => {
       expect(compilerOptions.noEmit).toBe(false);
       expect(compilerOptions.emitDeclarationOnly).toBe(false);
       expect(compilerOptions.emitDecoratorMetadata).toBe(false);
-      expect(compilerOptions.incremental).toBe(false);
-      expect(compilerOptions.tsBuildInfoFile).toBeUndefined();
+      expect(compilerOptions.incremental).toBe(true);
+      expect(compilerOptions.tsBuildInfoFile).toBe(path.join('/tmp/cache', '.tsbuildinfo'));
       expect(warnings).toEqual([]);
     });
   });
diff --git a/packages/angular/build/src/tools/angular/compilation/compiler-options.ts b/packages/angular/build/src/tools/angular/compilation/compiler-options.ts
index 22e0cff30bde..497e132ffefd 100644
--- a/packages/angular/build/src/tools/angular/compilation/compiler-options.ts
+++ b/packages/angular/build/src/tools/angular/compilation/compiler-options.ts
@@ -78,17 +78,13 @@ export function transformCompilerOptions(
     compilerOptions.compilationMode ??= 'partial';
   }
 
-  // Enable incremental compilation by default if caching is enabled and incremental is not explicitly disabled.
-  // Library compilation does not reuse on-disk .tsbuildinfo files across builds because all JS and .d.ts
-  // outputs must be emitted into in-memory maps on every cold build, while watch mode uses in-memory
-  // BuilderProgram state directly.
-  if (!isLibrary && compilerOptions.incremental !== false && overrides?.cachePath) {
+  // Enable incremental compilation by default if caching is enabled and incremental is not explicitly disabled
+  if (compilerOptions.incremental !== false && overrides?.cachePath) {
     compilerOptions.incremental = true;
     // Set the build info file location to the configured cache directory
     compilerOptions.tsBuildInfoFile = path.join(overrides.cachePath, '.tsbuildinfo');
   } else {
     compilerOptions.incremental = false;
-    compilerOptions.tsBuildInfoFile = undefined;
   }
 
   if (isLibrary) {

From 546e896675ca2f1b82d71248c1d069688820ce46 Mon Sep 17 00:00:00 2001
From: Alan Agius <17563226+alan-agius4@users.noreply.github.com>
Date: Tue, 20 Oct 2026 10:53:22 +0000
Subject: [PATCH 3/6] fixup! fix(@angular/build): enforce library
 compilerOptions and skip unused .tsbuildinfo emit

---
 .../build/src/tools/angular/compilation/compiler-options.ts     | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/packages/angular/build/src/tools/angular/compilation/compiler-options.ts b/packages/angular/build/src/tools/angular/compilation/compiler-options.ts
index 497e132ffefd..9e7ec87ead97 100644
--- a/packages/angular/build/src/tools/angular/compilation/compiler-options.ts
+++ b/packages/angular/build/src/tools/angular/compilation/compiler-options.ts
@@ -37,7 +37,7 @@ export function transformCompilerOptions(
 ): { compilerOptions: ng.CompilerOptions; warnings: PartialMessage[] } {
   const compilerOptions = { ...baseCompilerOptions };
   const warnings: PartialMessage[] = [];
-  const isLibrary = buildType === 'library' || !!baseCompilerOptions.declaration;
+  const isLibrary = buildType === 'library';
 
   if (
     !isLibrary &&

From 11c6f399c8438c20c272153df951766ab6f4092d Mon Sep 17 00:00:00 2001
From: Alan Agius <17563226+alan-agius4@users.noreply.github.com>
Date: Tue, 20 Oct 2026 13:03:22 +0000
Subject: [PATCH 4/6] fixup! fix(@angular/build): enforce library
 compilerOptions and skip unused .tsbuildinfo emit

---
 .../library/tests/behavior/build_spec.ts      |  1 -
 .../compilation/angular-compilation_spec.ts   |  2 --
 .../angular/compilation/compiler-options.ts   | 33 +++++++++----------
 3 files changed, 15 insertions(+), 21 deletions(-)

diff --git a/packages/angular/build/src/builders/library/tests/behavior/build_spec.ts b/packages/angular/build/src/builders/library/tests/behavior/build_spec.ts
index 3a4a8acbf1c6..56aa83fbade1 100644
--- a/packages/angular/build/src/builders/library/tests/behavior/build_spec.ts
+++ b/packages/angular/build/src/builders/library/tests/behavior/build_spec.ts
@@ -286,7 +286,6 @@ describeLibraryBuilder(executeLibraryBuilder, LIBRARY_BUILDER_INFO, (harness) =>
           ...tsconfig.compilerOptions,
           noEmit: true,
           emitDeclarationOnly: true,
-          emitDecoratorMetadata: true,
         };
 
         return JSON.stringify(tsconfig, null, 2);
diff --git a/packages/angular/build/src/tools/angular/compilation/angular-compilation_spec.ts b/packages/angular/build/src/tools/angular/compilation/angular-compilation_spec.ts
index 3b7d790f7102..2fe010d6680f 100644
--- a/packages/angular/build/src/tools/angular/compilation/angular-compilation_spec.ts
+++ b/packages/angular/build/src/tools/angular/compilation/angular-compilation_spec.ts
@@ -488,7 +488,6 @@ describe('AngularCompilation', () => {
           target: ts.ScriptTarget.ES2020,
           noEmit: true,
           emitDeclarationOnly: true,
-          emitDecoratorMetadata: true,
           isolatedModules: true,
         },
         {
@@ -502,7 +501,6 @@ describe('AngularCompilation', () => {
       expect(compilerOptions.useDefineForClassFields).toBeUndefined();
       expect(compilerOptions.noEmit).toBe(false);
       expect(compilerOptions.emitDeclarationOnly).toBe(false);
-      expect(compilerOptions.emitDecoratorMetadata).toBe(false);
       expect(compilerOptions.incremental).toBe(true);
       expect(compilerOptions.tsBuildInfoFile).toBe(path.join('/tmp/cache', '.tsbuildinfo'));
       expect(warnings).toEqual([]);
diff --git a/packages/angular/build/src/tools/angular/compilation/compiler-options.ts b/packages/angular/build/src/tools/angular/compilation/compiler-options.ts
index 9e7ec87ead97..867bb136dabd 100644
--- a/packages/angular/build/src/tools/angular/compilation/compiler-options.ts
+++ b/packages/angular/build/src/tools/angular/compilation/compiler-options.ts
@@ -39,10 +39,22 @@ export function transformCompilerOptions(
   const warnings: PartialMessage[] = [];
   const isLibrary = buildType === 'library';
 
+  if (isLibrary) {
+    compilerOptions.target = typeScript.ScriptTarget.ES2022;
+    compilerOptions.module = typeScript.ModuleKind.ES2022;
+    compilerOptions.importHelpers = true;
+    compilerOptions.declaration = true;
+    compilerOptions.declarationMap = !!(
+      overrides?.declarationMap ?? compilerOptions.declarationMap
+    );
+    compilerOptions.declarationDir = undefined;
+    compilerOptions.noEmit = false;
+    compilerOptions.emitDeclarationOnly = false;
+  }
+
   if (
-    !isLibrary &&
-    (compilerOptions.target === undefined ||
-      compilerOptions.target < typeScript.ScriptTarget.ES2022)
+    compilerOptions.target === undefined ||
+    compilerOptions.target < typeScript.ScriptTarget.ES2022
   ) {
     // If 'useDefineForClassFields' is already defined in the users project leave the value as is.
     // Otherwise fallback to false due to https://github.com/microsoft/TypeScript/issues/45995
@@ -87,21 +99,6 @@ export function transformCompilerOptions(
     compilerOptions.incremental = false;
   }
 
-  if (isLibrary) {
-    compilerOptions.target = typeScript.ScriptTarget.ES2022;
-    compilerOptions.module = typeScript.ModuleKind.ES2022;
-    compilerOptions.moduleResolution = typeScript.ModuleResolutionKind.Bundler;
-    compilerOptions.importHelpers = true;
-    compilerOptions.declaration = true;
-    compilerOptions.declarationMap = !!(
-      overrides?.declarationMap ?? compilerOptions.declarationMap
-    );
-    compilerOptions.declarationDir = undefined;
-    compilerOptions.noEmit = false;
-    compilerOptions.emitDeclarationOnly = false;
-    compilerOptions.emitDecoratorMetadata = false;
-  }
-
   if (
     compilerOptions.module === undefined ||
     compilerOptions.module < typeScript.ModuleKind.ES2015

From 373dcc196e059a5b0aa8ff0bdc03cdfdc50f3a7d Mon Sep 17 00:00:00 2001
From: Alan Agius <17563226+alan-agius4@users.noreply.github.com>
Date: Tue, 20 Oct 2026 13:04:10 +0000
Subject: [PATCH 5/6] fixup! fix(@angular/build): enforce library
 compilerOptions and skip unused .tsbuildinfo emit

---
 .../library/tests/behavior/build_spec.ts      | 26 -------------------
 1 file changed, 26 deletions(-)

diff --git a/packages/angular/build/src/builders/library/tests/behavior/build_spec.ts b/packages/angular/build/src/builders/library/tests/behavior/build_spec.ts
index 56aa83fbade1..0b6de2a26c7f 100644
--- a/packages/angular/build/src/builders/library/tests/behavior/build_spec.ts
+++ b/packages/angular/build/src/builders/library/tests/behavior/build_spec.ts
@@ -278,31 +278,5 @@ describeLibraryBuilder(executeLibraryBuilder, LIBRARY_BUILDER_INFO, (harness) =>
       expect(dtsContent).toContain('LibComponent');
       expect(dtsContent).toContain('CACHED_BUILD');
     });
-
-    it('should override noEmit and emitDeclarationOnly in tsconfig.lib.json and emit both JS and .d.ts files', async () => {
-      await harness.modifyFile('projects/lib/tsconfig.lib.json', (content) => {
-        const tsconfig = JSON.parse(content);
-        tsconfig.compilerOptions = {
-          ...tsconfig.compilerOptions,
-          noEmit: true,
-          emitDeclarationOnly: true,
-        };
-
-        return JSON.stringify(tsconfig, null, 2);
-      });
-
-      harness.useTarget('build', {
-        ...BASE_OPTIONS,
-      });
-
-      const { result } = await harness.executeOnce();
-      expect(result?.error).toBeUndefined();
-      expect(result?.success).toBeTrue();
-
-      const fesmContent = harness.readFile('dist/lib/fesm2022/lib.mjs');
-      expect(fesmContent).toContain('LibComponent');
-      const dtsContent = harness.readFile('dist/lib/types/lib.d.ts');
-      expect(dtsContent).toContain('LibComponent');
-    });
   });
 });

From 4f9c4cb96361bf930846939f91c939f893174339 Mon Sep 17 00:00:00 2001
From: Alan Agius <17563226+alan-agius4@users.noreply.github.com>
Date: Tue, 20 Oct 2026 14:24:03 +0000
Subject: [PATCH 6/6] fixup! fix(@angular/build): enforce library
 compilerOptions and skip unused .tsbuildinfo emit

---
 .../tools/angular/compilation/angular-compilation_spec.ts   | 3 +++
 .../build/src/tools/angular/compilation/compiler-options.ts | 6 +++---
 2 files changed, 6 insertions(+), 3 deletions(-)

diff --git a/packages/angular/build/src/tools/angular/compilation/angular-compilation_spec.ts b/packages/angular/build/src/tools/angular/compilation/angular-compilation_spec.ts
index 2fe010d6680f..842be5528f97 100644
--- a/packages/angular/build/src/tools/angular/compilation/angular-compilation_spec.ts
+++ b/packages/angular/build/src/tools/angular/compilation/angular-compilation_spec.ts
@@ -477,7 +477,9 @@ describe('AngularCompilation', () => {
       expect(compilerOptions['_useTypeScriptTranspilation']).toBe(true);
       expect(compilerOptions.supportTestBed).toBe(true);
       expect(compilerOptions.supportJitMode).toBe(true);
+      expect(compilerOptions.noEmit).toBe(false);
       expect(compilerOptions.noEmitOnError).toBe(false);
+      expect(compilerOptions.emitDeclarationOnly).toBe(false);
       expect(compilerOptions.composite).toBe(false);
     });
 
@@ -498,6 +500,7 @@ describe('AngularCompilation', () => {
       );
 
       expect(compilerOptions.target).toBe(ts.ScriptTarget.ES2022);
+      expect(compilerOptions.module).toBe(ts.ModuleKind.Preserve);
       expect(compilerOptions.useDefineForClassFields).toBeUndefined();
       expect(compilerOptions.noEmit).toBe(false);
       expect(compilerOptions.emitDeclarationOnly).toBe(false);
diff --git a/packages/angular/build/src/tools/angular/compilation/compiler-options.ts b/packages/angular/build/src/tools/angular/compilation/compiler-options.ts
index 867bb136dabd..1c37898abb31 100644
--- a/packages/angular/build/src/tools/angular/compilation/compiler-options.ts
+++ b/packages/angular/build/src/tools/angular/compilation/compiler-options.ts
@@ -41,15 +41,13 @@ export function transformCompilerOptions(
 
   if (isLibrary) {
     compilerOptions.target = typeScript.ScriptTarget.ES2022;
-    compilerOptions.module = typeScript.ModuleKind.ES2022;
+    compilerOptions.module = typeScript.ModuleKind.Preserve;
     compilerOptions.importHelpers = true;
     compilerOptions.declaration = true;
     compilerOptions.declarationMap = !!(
       overrides?.declarationMap ?? compilerOptions.declarationMap
     );
     compilerOptions.declarationDir = undefined;
-    compilerOptions.noEmit = false;
-    compilerOptions.emitDeclarationOnly = false;
   }
 
   if (
@@ -138,7 +136,9 @@ export function transformCompilerOptions(
     compilerOptions: {
       ...compilerOptions,
       basePath: overrides?.basePath ? toPosixPath(overrides.basePath) : compilerOptions.basePath,
+      noEmit: false,
       noEmitOnError: false,
+      emitDeclarationOnly: false,
       composite: false,
       inlineSources: !!overrides?.sourcemap,
       inlineSourceMap: !isLibrary && !!overrides?.sourcemap,