diff --git a/pkgs/native_assets_builder/CHANGELOG.md b/pkgs/native_assets_builder/CHANGELOG.md
index 97f2bf472..d10ec539d 100644
--- a/pkgs/native_assets_builder/CHANGELOG.md
+++ b/pkgs/native_assets_builder/CHANGELOG.md
@@ -2,6 +2,8 @@
 
 - Removed support for dry run (Flutter no long requires it).
 - Various fixes to caching.
+- **Breaking change** `BuildConfig.targetOS` is now only provided if
+  `buildAssetTypes` contains the code asset.
 
 ## 0.9.0
 
diff --git a/pkgs/native_assets_builder/lib/src/build_runner/build_runner.dart b/pkgs/native_assets_builder/lib/src/build_runner/build_runner.dart
index b3a20931f..8f86b49f9 100644
--- a/pkgs/native_assets_builder/lib/src/build_runner/build_runner.dart
+++ b/pkgs/native_assets_builder/lib/src/build_runner/build_runner.dart
@@ -92,7 +92,6 @@ class NativeAssetsBuildRunner {
     required BuildConfigValidator configValidator,
     required BuildValidator buildValidator,
     required ApplicationAssetValidator applicationAssetValidator,
-    required OS targetOS,
     required Uri workingDirectory,
     PackageLayout? packageLayout,
     String? runPackageName,
@@ -121,7 +120,6 @@ class NativeAssetsBuildRunner {
 
       final configBuilder = configCreator()
         ..setupHookConfig(
-          targetOS: targetOS,
           buildAssetTypes: buildAssetTypes,
           packageName: package.name,
           packageRoot: packageLayout.packageRoot(package.name),
@@ -197,7 +195,6 @@ class NativeAssetsBuildRunner {
     required LinkConfigCreator configCreator,
     required LinkConfigValidator configValidator,
     required LinkValidator linkValidator,
-    required OS targetOS,
     required Uri workingDirectory,
     required ApplicationAssetValidator applicationAssetValidator,
     PackageLayout? packageLayout,
@@ -220,7 +217,6 @@ class NativeAssetsBuildRunner {
     for (final package in buildPlan) {
       final configBuilder = configCreator()
         ..setupHookConfig(
-          targetOS: targetOS,
           buildAssetTypes: buildAssetTypes,
           packageName: package.name,
           packageRoot: packageLayout.packageRoot(package.name),
diff --git a/pkgs/native_assets_builder/test/build_runner/build_runner_reusability_test.dart b/pkgs/native_assets_builder/test/build_runner/build_runner_reusability_test.dart
index d279a12ae..aa7356a6c 100644
--- a/pkgs/native_assets_builder/test/build_runner/build_runner_reusability_test.dart
+++ b/pkgs/native_assets_builder/test/build_runner/build_runner_reusability_test.dart
@@ -30,12 +30,12 @@ void main() async {
       BuildConfigBuilder configCreator() => BuildConfigBuilder()
         ..setupCodeConfig(
           targetArchitecture: Architecture.current,
+          targetOS: OS.current,
           linkModePreference: LinkModePreference.dynamic,
         );
 
       await buildRunner.build(
         configCreator: configCreator,
-        targetOS: OS.current,
         workingDirectory: packageUri,
         linkingEnabled: false,
         buildAssetTypes: [],
@@ -45,7 +45,6 @@ void main() async {
       );
       await buildRunner.build(
         configCreator: configCreator,
-        targetOS: OS.current,
         workingDirectory: packageUri,
         linkingEnabled: false,
         buildAssetTypes: [],
diff --git a/pkgs/native_assets_builder/test/build_runner/concurrency_shared_test_helper.dart b/pkgs/native_assets_builder/test/build_runner/concurrency_shared_test_helper.dart
index e741bfa13..d31b8c434 100644
--- a/pkgs/native_assets_builder/test/build_runner/concurrency_shared_test_helper.dart
+++ b/pkgs/native_assets_builder/test/build_runner/concurrency_shared_test_helper.dart
@@ -20,8 +20,14 @@ void main(List<String> args) async {
     logger: logger,
     dartExecutable: dartExecutable,
   ).build(
-    configCreator: BuildConfigBuilder.new,
-    targetOS: target.os,
+    // Set up the code config, so that the builds for different targets are
+    // in different directories.
+    configCreator: () => BuildConfigBuilder()
+      ..setupCodeConfig(
+        targetArchitecture: target.architecture,
+        targetOS: target.os,
+        linkModePreference: LinkModePreference.dynamic,
+      ),
     workingDirectory: packageUri,
     linkingEnabled: false,
     buildAssetTypes: [DataAsset.type],
diff --git a/pkgs/native_assets_builder/test/build_runner/concurrency_test_helper.dart b/pkgs/native_assets_builder/test/build_runner/concurrency_test_helper.dart
index 9a680232b..75d2cb096 100644
--- a/pkgs/native_assets_builder/test/build_runner/concurrency_test_helper.dart
+++ b/pkgs/native_assets_builder/test/build_runner/concurrency_test_helper.dart
@@ -28,11 +28,11 @@ void main(List<String> args) async {
     configCreator: () => BuildConfigBuilder()
       ..setupCodeConfig(
         targetArchitecture: Architecture.current,
+        targetOS: OS.current,
         linkModePreference: LinkModePreference.dynamic,
         cCompilerConfig: dartCICompilerConfig,
         targetMacOSVersion: OS.current == OS.macOS ? defaultMacOSVersion : null,
       ),
-    targetOS: OS.current,
     workingDirectory: packageUri,
     linkingEnabled: false,
     buildAssetTypes: [CodeAsset.type, DataAsset.type],
diff --git a/pkgs/native_assets_builder/test/build_runner/helpers.dart b/pkgs/native_assets_builder/test/build_runner/helpers.dart
index 275ec9c9a..6be66afea 100644
--- a/pkgs/native_assets_builder/test/build_runner/helpers.dart
+++ b/pkgs/native_assets_builder/test/build_runner/helpers.dart
@@ -59,6 +59,7 @@ Future<BuildResult?> build(
         if (buildAssetTypes.contains(CodeAsset.type)) {
           configBuilder.setupCodeConfig(
             targetArchitecture: target?.architecture ?? Architecture.current,
+            targetOS: targetOS,
             linkModePreference: linkModePreference,
             cCompilerConfig: cCompilerConfig ?? dartCICompilerConfig,
             targetIOSSdk: targetIOSSdk,
@@ -71,7 +72,6 @@ Future<BuildResult?> build(
         return configBuilder;
       },
       configValidator: configValidator,
-      targetOS: targetOS,
       workingDirectory: packageUri,
       packageLayout: packageLayout,
       runPackageName: runPackageName,
@@ -124,6 +124,7 @@ Future<LinkResult?> link(
         if (buildAssetTypes.contains(CodeAsset.type)) {
           configBuilder.setupCodeConfig(
             targetArchitecture: target?.architecture ?? Architecture.current,
+            targetOS: target?.os ?? OS.current,
             linkModePreference: linkModePreference,
             cCompilerConfig: cCompilerConfig ?? dartCICompilerConfig,
             targetIOSSdk: targetIOSSdk,
@@ -136,7 +137,6 @@ Future<LinkResult?> link(
         return configBuilder;
       },
       configValidator: configValidator,
-      targetOS: target?.os ?? OS.current,
       workingDirectory: packageUri,
       packageLayout: packageLayout,
       buildResult: buildResult,
@@ -185,6 +185,7 @@ Future<(BuildResult?, LinkResult?)> buildAndLink(
         configCreator: () => BuildConfigBuilder()
           ..setupCodeConfig(
             targetArchitecture: target?.architecture ?? Architecture.current,
+            targetOS: target?.os ?? OS.current,
             linkModePreference: linkModePreference,
             cCompilerConfig: cCompilerConfig ?? dartCICompilerConfig,
             targetIOSSdk: targetIOSSdk,
@@ -193,7 +194,6 @@ Future<(BuildResult?, LinkResult?)> buildAndLink(
             targetAndroidNdkApi: targetAndroidNdkApi,
           ),
         configValidator: buildConfigValidator,
-        targetOS: target?.os ?? OS.current,
         workingDirectory: packageUri,
         packageLayout: packageLayout,
         runPackageName: runPackageName,
@@ -217,6 +217,7 @@ Future<(BuildResult?, LinkResult?)> buildAndLink(
         configCreator: () => LinkConfigBuilder()
           ..setupCodeConfig(
             targetArchitecture: target?.architecture ?? Architecture.current,
+            targetOS: target?.os ?? OS.current,
             linkModePreference: linkModePreference,
             cCompilerConfig: cCompilerConfig,
             targetIOSSdk: targetIOSSdk,
@@ -225,7 +226,6 @@ Future<(BuildResult?, LinkResult?)> buildAndLink(
             targetAndroidNdkApi: targetAndroidNdkApi,
           ),
         configValidator: linkConfigValidator,
-        targetOS: target?.os ?? OS.current,
         workingDirectory: packageUri,
         packageLayout: packageLayout,
         buildResult: buildResult,
diff --git a/pkgs/native_assets_builder/test/test_data/native_dynamic_linking_test.dart b/pkgs/native_assets_builder/test/test_data/native_dynamic_linking_test.dart
index a2b167d12..2e35c3b13 100644
--- a/pkgs/native_assets_builder/test/test_data/native_dynamic_linking_test.dart
+++ b/pkgs/native_assets_builder/test/test_data/native_dynamic_linking_test.dart
@@ -34,7 +34,6 @@ void main() async {
         ..setupHookConfig(
           packageName: name,
           packageRoot: testPackageUri,
-          targetOS: OS.current,
           buildAssetTypes: [CodeAsset.type],
         )
         ..setupBuildConfig(dryRun: false, linkingEnabled: false)
@@ -44,6 +43,7 @@ void main() async {
         )
         ..setupCodeConfig(
           targetArchitecture: Architecture.current,
+          targetOS: OS.current,
           linkModePreference: LinkModePreference.dynamic,
           cCompilerConfig: cCompiler,
         );
diff --git a/pkgs/native_assets_builder/test/test_data/transformer_test.dart b/pkgs/native_assets_builder/test/test_data/transformer_test.dart
index c965e136d..05d2b868c 100644
--- a/pkgs/native_assets_builder/test/test_data/transformer_test.dart
+++ b/pkgs/native_assets_builder/test/test_data/transformer_test.dart
@@ -49,7 +49,6 @@ void main() async {
           ..setupHookConfig(
             packageName: packageName,
             packageRoot: packageUri,
-            targetOS: OS.current,
             buildAssetTypes: [DataAsset.type],
           )
           ..setupBuildConfig(dryRun: false, linkingEnabled: false)
@@ -59,6 +58,7 @@ void main() async {
           )
           ..setupCodeConfig(
             targetArchitecture: architecture,
+            targetOS: OS.current,
             linkModePreference: LinkModePreference.dynamic,
           );
 
diff --git a/pkgs/native_assets_builder/test_data/fail_on_os_sdk_version/hook/build.dart b/pkgs/native_assets_builder/test_data/fail_on_os_sdk_version/hook/build.dart
index 177b2d794..d774f5e13 100644
--- a/pkgs/native_assets_builder/test_data/fail_on_os_sdk_version/hook/build.dart
+++ b/pkgs/native_assets_builder/test_data/fail_on_os_sdk_version/hook/build.dart
@@ -14,7 +14,7 @@ const minMacOSVersionForThisPackage = 13;
 
 void main(List<String> arguments) async {
   await build(arguments, (config, output) async {
-    if (config.targetOS == OS.android) {
+    if (config.codeConfig.targetOS == OS.android) {
       if (config.codeConfig.targetAndroidNdkApi! <
           minNdkApiVersionForThisPackage) {
         throw UnsupportedError(
@@ -22,7 +22,7 @@ void main(List<String> arguments) async {
           'least Android NDK API level $minNdkApiVersionForThisPackage.',
         );
       }
-    } else if (config.targetOS == OS.iOS) {
+    } else if (config.codeConfig.targetOS == OS.iOS) {
       final iosVersion = config.codeConfig.targetIOSVersion;
       // iosVersion is nullable to deal with version skew.
       if (iosVersion != null && iosVersion < minIosVersionForThisPackage) {
@@ -31,7 +31,7 @@ void main(List<String> arguments) async {
           'least iOS version $minIosVersionForThisPackage.',
         );
       }
-    } else if (config.targetOS == OS.macOS) {
+    } else if (config.codeConfig.targetOS == OS.macOS) {
       final macosVersion = config.codeConfig.targetMacOSVersion;
       // macosVersion is nullable to deal with version skew.
       if (macosVersion != null &&
diff --git a/pkgs/native_assets_builder/test_data/fail_on_os_sdk_version_linker/hook/link.dart b/pkgs/native_assets_builder/test_data/fail_on_os_sdk_version_linker/hook/link.dart
index 27aec5e37..a4603499f 100644
--- a/pkgs/native_assets_builder/test_data/fail_on_os_sdk_version_linker/hook/link.dart
+++ b/pkgs/native_assets_builder/test_data/fail_on_os_sdk_version_linker/hook/link.dart
@@ -14,7 +14,7 @@ const minMacOSVersionForThisPackage = 13;
 
 void main(List<String> arguments) async {
   await link(arguments, (config, output) async {
-    if (config.targetOS == OS.android) {
+    if (config.codeConfig.targetOS == OS.android) {
       if (config.codeConfig.targetAndroidNdkApi! <
           minNdkApiVersionForThisPackage) {
         throw UnsupportedError(
@@ -22,7 +22,7 @@ void main(List<String> arguments) async {
           'least Android NDK API level $minNdkApiVersionForThisPackage.',
         );
       }
-    } else if (config.targetOS == OS.iOS) {
+    } else if (config.codeConfig.targetOS == OS.iOS) {
       final iosVersion = config.codeConfig.targetIOSVersion;
       // iosVersion is nullable to deal with version skew.
       if (iosVersion != null && iosVersion < minIosVersionForThisPackage) {
@@ -31,7 +31,7 @@ void main(List<String> arguments) async {
           'least iOS version $minIosVersionForThisPackage.',
         );
       }
-    } else if (config.targetOS == OS.macOS) {
+    } else if (config.codeConfig.targetOS == OS.macOS) {
       final macosVersion = config.codeConfig.targetMacOSVersion;
       // macosVersion is nullable to deal with version skew.
       if (macosVersion != null &&
diff --git a/pkgs/native_assets_cli/CHANGELOG.md b/pkgs/native_assets_cli/CHANGELOG.md
index 20a84d7d7..4d01bed7a 100644
--- a/pkgs/native_assets_cli/CHANGELOG.md
+++ b/pkgs/native_assets_cli/CHANGELOG.md
@@ -9,6 +9,8 @@
   it can be controlled in the build hook together with the `OptimizationLevel`.
   Most likely, every package should ship with `release`. `BuildMode.debug`
   should only be used while developing the package locally.
+- **Breaking change** Move `HookConfig.targetOS` to `CodeConfig`. `DataAsset`s
+  and other asset types might now support varying on the target OS.
 - **Breaking change**: Change the behavior of `testBuildHook` and
   `testCodeBuildHook`; instead of defining tests, these methods should now be
   called from within tests.
diff --git a/pkgs/native_assets_cli/example/build/local_asset/hook/build.dart b/pkgs/native_assets_cli/example/build/local_asset/hook/build.dart
index 3e61c0c4a..9547ac51b 100644
--- a/pkgs/native_assets_cli/example/build/local_asset/hook/build.dart
+++ b/pkgs/native_assets_cli/example/build/local_asset/hook/build.dart
@@ -38,7 +38,7 @@ Future<void> main(List<String> args) async {
         name: 'asset.txt',
         file: assetPath,
         linkMode: DynamicLoadingBundled(),
-        os: config.targetOS,
+        os: config.codeConfig.targetOS,
         architecture:
             // ignore: deprecated_member_use
             config.dryRun ? null : config.codeConfig.targetArchitecture,
diff --git a/pkgs/native_assets_cli/lib/code_assets.dart b/pkgs/native_assets_cli/lib/code_assets.dart
index 0e84016a7..82c32b6d5 100644
--- a/pkgs/native_assets_cli/lib/code_assets.dart
+++ b/pkgs/native_assets_cli/lib/code_assets.dart
@@ -32,3 +32,4 @@ export 'src/code_assets/link_mode.dart'
         LookupInProcess,
         StaticLinking;
 export 'src/code_assets/link_mode_preference.dart' show LinkModePreference;
+export 'src/code_assets/os.dart' show OS;
diff --git a/pkgs/native_assets_cli/lib/native_assets_cli.dart b/pkgs/native_assets_cli/lib/native_assets_cli.dart
index a484fe804..be4d880a3 100644
--- a/pkgs/native_assets_cli/lib/native_assets_cli.dart
+++ b/pkgs/native_assets_cli/lib/native_assets_cli.dart
@@ -21,4 +21,3 @@ export 'src/config.dart'
         LinkOutputBuilder;
 export 'src/encoded_asset.dart' show EncodedAsset;
 export 'src/metadata.dart';
-export 'src/os.dart' show OS;
diff --git a/pkgs/native_assets_cli/lib/src/api/build.dart b/pkgs/native_assets_cli/lib/src/api/build.dart
index c033a8c58..cd7cc063f 100644
--- a/pkgs/native_assets_cli/lib/src/api/build.dart
+++ b/pkgs/native_assets_cli/lib/src/api/build.dart
@@ -82,7 +82,7 @@ import '../validation.dart';
 ///         name: 'asset.txt',
 ///         file: assetPath,
 ///         linkMode: DynamicLoadingBundled(),
-///         os: config.targetOS,
+///         os: config.codeConfig.targetOS,
 ///         architecture: config.codeConfig.targetArchitecture,
 ///       ),
 ///     );
diff --git a/pkgs/native_assets_cli/lib/src/code_assets/code_asset.dart b/pkgs/native_assets_cli/lib/src/code_assets/code_asset.dart
index dcfeaf4ff..4a65875ae 100644
--- a/pkgs/native_assets_cli/lib/src/code_assets/code_asset.dart
+++ b/pkgs/native_assets_cli/lib/src/code_assets/code_asset.dart
@@ -5,12 +5,11 @@
 import '../config.dart';
 import '../encoded_asset.dart';
 import '../json_utils.dart';
-import '../os.dart';
 import '../utils/json.dart';
 import '../utils/map.dart';
-
 import 'architecture.dart';
 import 'link_mode.dart';
+import 'os.dart';
 
 /// A code asset which respects the native application binary interface (ABI).
 ///
diff --git a/pkgs/native_assets_cli/lib/src/code_assets/config.dart b/pkgs/native_assets_cli/lib/src/code_assets/config.dart
index f9a3d97e8..6f749a106 100644
--- a/pkgs/native_assets_cli/lib/src/code_assets/config.dart
+++ b/pkgs/native_assets_cli/lib/src/code_assets/config.dart
@@ -4,12 +4,12 @@
 
 import '../config.dart';
 import '../json_utils.dart';
-
 import 'architecture.dart';
 import 'c_compiler_config.dart';
 import 'code_asset.dart';
 import 'ios_sdk.dart';
 import 'link_mode_preference.dart';
+import 'os.dart';
 
 /// Extension to the [BuildConfig] providing access to configuration specific to
 /// code assets (only available if code assets are supported).
@@ -48,6 +48,9 @@ class CodeConfig {
   final int? targetAndroidNdkApi;
   final IOSSdk? targetIOSSdk;
 
+  /// The operating system being compiled for.
+  final OS targetOS;
+
   CodeConfig(HookConfig config)
       : linkModePreference = LinkModePreference.fromString(
             config.json.string(_linkModePreferenceKey)),
@@ -56,6 +59,7 @@ class CodeConfig {
             ? null
             : Architecture.fromString(config.json.string(_targetArchitectureKey,
                 validValues: Architecture.values.map((a) => a.name))),
+        targetOS = OS.fromString(config.json.string(_targetOSConfigKey)),
         cCompiler = switch (config.json.optionalMap(_compilerKey)) {
           final Map<String, Object?> map => CCompilerConfig.fromJson(map),
           null => CCompilerConfig(),
@@ -121,6 +125,7 @@ extension type CodeAssetLinkOutputBuilderAdd._(LinkOutputBuilder _output) {
 extension CodeAssetBuildConfigBuilder on HookConfigBuilder {
   void setupCodeConfig({
     required Architecture? targetArchitecture,
+    required OS targetOS,
     required LinkModePreference linkModePreference,
     CCompilerConfig? cCompilerConfig,
     int? targetIOSVersion,
@@ -131,6 +136,7 @@ extension CodeAssetBuildConfigBuilder on HookConfigBuilder {
     if (targetArchitecture != null) {
       json[_targetArchitectureKey] = targetArchitecture.toString();
     }
+    json[_targetOSConfigKey] = targetOS.toString();
     json[_linkModePreferenceKey] = linkModePreference.toString();
     if (cCompilerConfig != null) {
       json[_compilerKey] = cCompilerConfig.toJson();
@@ -170,9 +176,10 @@ extension CodeAssetLinkOutput on LinkOutput {
 }
 
 const String _compilerKey = 'c_compiler';
+const String _linkModePreferenceKey = 'link_mode_preference';
+const String _targetAndroidNdkApiKey = 'target_android_ndk_api';
 const String _targetArchitectureKey = 'target_architecture';
 const String _targetIOSSdkKey = 'target_ios_sdk';
-const String _linkModePreferenceKey = 'link_mode_preference';
 const String _targetIOSVersionKey = 'target_ios_version';
 const String _targetMacOSVersionKey = 'target_macos_version';
-const String _targetAndroidNdkApiKey = 'target_android_ndk_api';
+const String _targetOSConfigKey = 'target_os';
diff --git a/pkgs/native_assets_cli/lib/src/os.dart b/pkgs/native_assets_cli/lib/src/code_assets/os.dart
similarity index 100%
rename from pkgs/native_assets_cli/lib/src/os.dart
rename to pkgs/native_assets_cli/lib/src/code_assets/os.dart
diff --git a/pkgs/native_assets_cli/lib/src/code_assets/testing.dart b/pkgs/native_assets_cli/lib/src/code_assets/testing.dart
index 25f3741f1..3d2648273 100644
--- a/pkgs/native_assets_cli/lib/src/code_assets/testing.dart
+++ b/pkgs/native_assets_cli/lib/src/code_assets/testing.dart
@@ -42,6 +42,7 @@ Future<void> testCodeBuildHook({
         linkModePreference: linkModePreference ?? LinkModePreference.dynamic,
         cCompilerConfig: cCompiler,
         targetArchitecture: targetArchitecture ?? Architecture.current,
+        targetOS: targetOS ?? OS.current,
         targetIOSSdk: targetIOSSdk,
         targetIOSVersion: targetIOSVersion,
         targetMacOSVersion: targetMacOSVersion,
@@ -58,7 +59,6 @@ Future<void> testCodeBuildHook({
 
       await check(config, output);
     },
-    targetOS: targetOS,
     buildAssetTypes: buildAssetTypes,
     linkingEnabled: linkingEnabled,
   );
diff --git a/pkgs/native_assets_cli/lib/src/code_assets/validation.dart b/pkgs/native_assets_cli/lib/src/code_assets/validation.dart
index 8361824b5..b01dcc559 100644
--- a/pkgs/native_assets_cli/lib/src/code_assets/validation.dart
+++ b/pkgs/native_assets_cli/lib/src/code_assets/validation.dart
@@ -12,7 +12,7 @@ Future<ValidationErrors> validateCodeAssetBuildConfig(
         BuildConfig config) async =>
     _validateCodeConfig(
       'BuildConfig',
-      config.targetOS,
+      config.codeConfig.targetOS,
       // ignore: deprecated_member_use_from_same_package
       config.dryRun,
       config.codeConfig,
@@ -20,7 +20,7 @@ Future<ValidationErrors> validateCodeAssetBuildConfig(
 
 Future<ValidationErrors> validateCodeAssetLinkConfig(LinkConfig config) async =>
     _validateCodeConfig(
-        'LinkConfig', config.targetOS, false, config.codeConfig);
+        'LinkConfig', config.codeConfig.targetOS, false, config.codeConfig);
 
 ValidationErrors _validateCodeConfig(
     String configName, OS targetOS, bool dryRun, CodeConfig codeConfig) {
@@ -169,9 +169,9 @@ void _validateCodeAssets(
   }
 
   final os = codeAsset.os;
-  if (config.targetOS != os) {
+  if (codeConfig.targetOS != os) {
     final error = 'CodeAsset "$id" has a os "$os", which '
-        'is not the target os "${config.targetOS}".';
+        'is not the target os "${codeConfig.targetOS}".';
     errors.add(error);
   }
 
diff --git a/pkgs/native_assets_cli/lib/src/config.dart b/pkgs/native_assets_cli/lib/src/config.dart
index 27d66de18..ff1912306 100644
--- a/pkgs/native_assets_cli/lib/src/config.dart
+++ b/pkgs/native_assets_cli/lib/src/config.dart
@@ -10,10 +10,10 @@ import 'package:pub_semver/pub_semver.dart';
 
 import 'api/deprecation_messages.dart';
 import 'code_assets/architecture.dart';
+import 'code_assets/os.dart';
 import 'encoded_asset.dart';
 import 'json_utils.dart';
 import 'metadata.dart';
-import 'os.dart';
 import 'utils/datetime.dart';
 import 'utils/json.dart';
 
@@ -61,9 +61,6 @@ sealed class HookConfig {
   /// another. For this it is convenient to know the packageRoot.
   final Uri packageRoot;
 
-  /// The operating system being compiled for.
-  final OS targetOS;
-
   /// The asset types that the invoker of this hook supports.
   final List<String> buildAssetTypes;
 
@@ -80,7 +77,6 @@ sealed class HookConfig {
         outputDirectoryShared = json.path(_outDirSharedConfigKey),
         packageRoot = json.path(_packageRootConfigKey),
         packageName = json.string(_packageNameConfigKey),
-        targetOS = OS.fromString(json.string(_targetOSConfigKey)),
         buildAssetTypes = json.optionalStringList(_buildAssetTypesKey) ??
             json.optionalStringList(_supportedAssetTypesKey) ??
             const [];
@@ -97,12 +93,10 @@ sealed class HookConfigBuilder {
   void setupHookConfig({
     required Uri packageRoot,
     required String packageName,
-    required OS targetOS,
     required List<String> buildAssetTypes,
   }) {
     json[_packageNameConfigKey] = packageName;
     json[_packageRootConfigKey] = packageRoot.toFilePath();
-    json[_targetOSConfigKey] = targetOS.toString();
     json[_buildAssetTypesKey] = buildAssetTypes;
     json[_supportedAssetTypesKey] = buildAssetTypes;
   }
@@ -135,7 +129,6 @@ sealed class HookConfigBuilder {
   }
 }
 
-const _targetOSConfigKey = 'target_os';
 // TODO: Bump min-SDK constraint to 3.7 and remove once stable.
 const _buildModeConfigKeyDeprecated = 'build_mode';
 const _metadataConfigKey = 'metadata';
diff --git a/pkgs/native_assets_cli/lib/src/model/build_config_CHANGELOG.md b/pkgs/native_assets_cli/lib/src/model/build_config_CHANGELOG.md
index 77c5947e0..c460ecc8a 100644
--- a/pkgs/native_assets_cli/lib/src/model/build_config_CHANGELOG.md
+++ b/pkgs/native_assets_cli/lib/src/model/build_config_CHANGELOG.md
@@ -3,6 +3,14 @@
 - `BuildConfig.supportedAssetTypes` renamed to `BuildConfig.buildAssetTypes`.
   Compatibility with older SDKs: Look for the old key. Compatibility with older
   hooks: Also provide the old hook in the config.
+- `BuildConfig.targetOS` is now only provided if `buildAssetTypes` contains the
+  code asset.
+  Compatibility with older SDKs: Fine, they always provide it.
+  Compatibility with older hooks: Currently, no embedders call hooks without
+  support for code assets. Once they do (data assets on web), existing hooks
+  will break. Mitigation: Update existing hooks to check for `buildAssetTypes`
+  and/or change `CBuilder` to be a no-op if `buildAssetTypes` does not contain
+  code assets.
 - `BuildConfig.outputDirectoryShared` for sharing between hook invocations.
   Compatibility with older SDKs: Create a sibling dir next to the output
   directory. This does not facilitate caching, but should not break the hook.
diff --git a/pkgs/native_assets_cli/lib/src/target.dart b/pkgs/native_assets_cli/lib/src/target.dart
index fc595fed6..39cc5687e 100644
--- a/pkgs/native_assets_cli/lib/src/target.dart
+++ b/pkgs/native_assets_cli/lib/src/target.dart
@@ -6,7 +6,7 @@ import 'dart:ffi' show Abi;
 import 'dart:io';
 
 import 'code_assets/architecture.dart';
-import 'os.dart';
+import 'code_assets/os.dart';
 
 final class Target implements Comparable<Target> {
   final Abi abi;
diff --git a/pkgs/native_assets_cli/lib/test.dart b/pkgs/native_assets_cli/lib/test.dart
index 21deb2490..e18210a4b 100644
--- a/pkgs/native_assets_cli/lib/test.dart
+++ b/pkgs/native_assets_cli/lib/test.dart
@@ -30,7 +30,6 @@ Future<void> testBuildHook({
   required FutureOr<void> Function(List<String> arguments) mainMethod,
   required FutureOr<void> Function(BuildConfig config, BuildOutput output)
       check,
-  OS? targetOS,
   List<String>? buildAssetTypes,
   bool? linkingEnabled,
 }) async {
@@ -53,7 +52,6 @@ Future<void> testBuildHook({
       ..setupHookConfig(
         packageRoot: Directory.current.uri,
         packageName: _readPackageNameFromPubspec(),
-        targetOS: targetOS ?? OS.current,
         buildAssetTypes: buildAssetTypes ?? [],
       )
       ..setupBuildConfig(
diff --git a/pkgs/native_assets_cli/test/api/build_test.dart b/pkgs/native_assets_cli/test/api/build_test.dart
index b10d9adb1..aa2801b37 100644
--- a/pkgs/native_assets_cli/test/api/build_test.dart
+++ b/pkgs/native_assets_cli/test/api/build_test.dart
@@ -34,7 +34,6 @@ void main() async {
       ..setupHookConfig(
         packageRoot: tempUri,
         packageName: packageName,
-        targetOS: OS.iOS,
         buildAssetTypes: ['foo'],
       )
       ..setupBuildConfig(
diff --git a/pkgs/native_assets_cli/test/build_config_test.dart b/pkgs/native_assets_cli/test/build_config_test.dart
index 61fdf685a..10e844ab0 100644
--- a/pkgs/native_assets_cli/test/build_config_test.dart
+++ b/pkgs/native_assets_cli/test/build_config_test.dart
@@ -40,7 +40,6 @@ void main() async {
       ..setupHookConfig(
         packageName: packageName,
         packageRoot: packageRootUri,
-        targetOS: OS.android,
         buildAssetTypes: ['my-asset-type'],
       )
       ..setupBuildConfig(
@@ -73,7 +72,6 @@ void main() async {
       'package_name': packageName,
       'package_root': packageRootUri.toFilePath(),
       'supported_asset_types': ['my-asset-type'],
-      'target_os': 'android',
       'version': latestVersion.toString(),
     };
 
@@ -85,7 +83,6 @@ void main() async {
 
     expect(config.packageName, packageName);
     expect(config.packageRoot, packageRootUri);
-    expect(config.targetOS, OS.android);
     expect(config.buildAssetTypes, ['my-asset-type']);
 
     expect(config.linkingEnabled, false);
@@ -98,7 +95,6 @@ void main() async {
       ..setupHookConfig(
         packageName: packageName,
         packageRoot: packageRootUri,
-        targetOS: OS.android,
         buildAssetTypes: ['my-asset-type'],
       )
       ..setupBuildConfig(
@@ -121,7 +117,6 @@ void main() async {
       'package_name': packageName,
       'package_root': packageRootUri.toFilePath(),
       'supported_asset_types': ['my-asset-type'],
-      'target_os': 'android',
       'version': latestVersion.toString(),
     };
 
@@ -133,7 +128,6 @@ void main() async {
 
     expect(config.packageName, packageName);
     expect(config.packageRoot, packageRootUri);
-    expect(config.targetOS, OS.android);
     expect(config.buildAssetTypes, ['my-asset-type']);
 
     expect(config.linkingEnabled, true);
diff --git a/pkgs/native_assets_cli/test/checksum_test.dart b/pkgs/native_assets_cli/test/checksum_test.dart
index aee34b710..3b2376d28 100644
--- a/pkgs/native_assets_cli/test/checksum_test.dart
+++ b/pkgs/native_assets_cli/test/checksum_test.dart
@@ -14,21 +14,31 @@ void main() {
     final configs = <String>[];
     final checksums = <String>[];
     for (final os in [OS.linux, OS.macOS]) {
-      for (final packageName in ['foo', 'bar']) {
-        for (final assetType in [CodeAsset.type, DataAsset.type]) {
-          for (final dryRun in [true, false]) {
-            for (final linking in [true, false]) {
-              final builder = BuildConfigBuilder()
-                ..setupHookConfig(
-                  packageRoot: Uri.file('foo'),
-                  packageName: packageName,
-                  targetOS: os,
-                  buildAssetTypes: [assetType],
-                )
-                ..setupBuildConfig(dryRun: dryRun, linkingEnabled: linking);
-              configs
-                  .add(const JsonEncoder.withIndent(' ').convert(builder.json));
-              checksums.add(builder.computeChecksum());
+      for (final architecture in [Architecture.arm64, Architecture.x64]) {
+        for (final packageName in ['foo', 'bar']) {
+          for (final assetType in [CodeAsset.type, DataAsset.type]) {
+            for (final dryRun in [true, false]) {
+              for (final linking in [true, false]) {
+                final builder = BuildConfigBuilder()
+                  ..setupHookConfig(
+                    packageRoot: Uri.file('foo'),
+                    packageName: packageName,
+                    buildAssetTypes: [assetType],
+                  )
+                  ..setupBuildConfig(
+                    dryRun: dryRun,
+                    linkingEnabled: linking,
+                  )
+                  ..setupCodeConfig(
+                    targetArchitecture: architecture,
+                    targetOS: os,
+                    linkModePreference: LinkModePreference.dynamic,
+                  );
+                configs.add(
+                  const JsonEncoder.withIndent(' ').convert(builder.json),
+                );
+                checksums.add(builder.computeChecksum());
+              }
             }
           }
         }
@@ -42,38 +52,70 @@ void main() {
     // needing to update this list).
 
     final expectedChecksums = <String>[
-      '4cfa5fbd14f8d73d04014ee5b453b000',
-      '365e989ba01bac43d654981fec67205d',
-      '2191c07f18b5ef13999eb6f8356ae02e',
-      '257890f33b84d191746a378fb0db4eba',
-      'c22d663cde074a6722c2d5253b8e0619',
-      'f520e2f4fd0f2fd76da0c6c18db9559b',
-      '7cc71dd803c24a424db70444002df999',
-      'a5774f32e91551e8dfdcc3f63e45f3ed',
-      '0f361f3a5072f66f68eb4d7a7e4b92d6',
-      '5cc8e330ea24c647a1dbf2d82497c73c',
-      '97b5dbdf7a76cf5839de3bd0cac63b6d',
-      'ccc846104ddc0dbd700190638b756435',
-      '0fca1f77969d6e24602cf44c28695c2b',
-      '683be025644ff73c5eba9d1f99f9808c',
-      '7a6982964efcf50507669706e31bdab5',
-      'd2b17c98c64e750d8bd2ed5beb907401',
-      'de3ac273831822414783f0d72acf9d82',
-      '09c17c21bd277ea2709c35205a2fdfa6',
-      'f07b3399888444bc2b7fa837c0c1dddb',
-      '6e92bc3271d65229793d8bd1ed4e00be',
-      'd353ae01cf04e201180edf8c5e4dac37',
-      '25044b641a83b33860cf8f79154652bb',
-      'afc5e24300cf70245146148111b8a746',
-      '8023595c2343952c02e2aa47f6ee809f',
-      '226d39440aa5380bbcf71fb9a804a4b0',
-      '26cab023910889c0c96cbba2bb04ad97',
-      '32bea1c49326ae259fe97a6fc7b1e08d',
-      'a0cccc3aa7069efc86a84b0299dba682',
-      '28280ef1dfe5e5922eb97577e8a85c40',
-      '69595125d5987c952355903deaa87684',
-      'b5328455769192919339d0e6158d728d',
-      'ed827ce888b9929ba83e04af8d5b7a37',
+      'd666127fab5478b736d505c0cbd2e08e',
+      '5d5cf5cf7916bd7adc26f5d5611f23ec',
+      '29cb9cf638acac26c1e7eb20bf4e359a',
+      '2214edee21375319f5612344dfe6acbc',
+      '40b61c96feff406659bc35e24875744b',
+      'a0492f5322cea695e3bc1522d66a20ce',
+      '9f5269a2c0c663023af449e77ac39980',
+      'c9add26b586b1fb897f9ff0d2edb235d',
+      '95ec14e605b3519f00ea8816b328e0ad',
+      'fc5792f6beb3c0e0f7894537a3fa4850',
+      'bbf84c44fb1ce09636a70d3e9a8590be',
+      '9c83dfb94b98c6f4ec79cbabc95e6198',
+      'af8712f4857423f455d2912c55fe6766',
+      '99d1eba44f3e914b58768c210d139cc1',
+      '12cc255c3fc076d3550ac32b43166631',
+      '2188cca31e8306cbacb9c3d799b5513c',
+      '65ad5d4fb66745aad4e5a2969a1e45b1',
+      '29da0a967b9cfd5e4d21d61c97d2a99e',
+      'efef4a8ab871ed05a9358a2e4d6d4e03',
+      '672a07ce5b6f82204ba92b45c287781c',
+      '4bcdd217687c15fb108dc9a9b8f8537c',
+      'c0593c4282d42a659d66d8b72e44b2a6',
+      'dd428de57da1d45149f4ff8a27fa3ea0',
+      'c04f80b8be73bcfe435c586ef8a979bc',
+      '1056f2bf80b3c1979952af1e62e34576',
+      'b7d943b4bab492e10c582bdd58aced0e',
+      'ed56d7afbd306393c3206685e6d1ba81',
+      '1463940666f69e3b132f3766570ef83b',
+      '5451c1a2a24bc5e1206b245b028e0078',
+      '5f2c169a71039d3d6b2ae74e3c2723d7',
+      '67759625e5a0908dabcaeeb2b1264f84',
+      '921b2b7012548949e9b465addccc2e71',
+      '94bc85e935634df06e208ac8ab9643d3',
+      'ee4cd19fc3ac5d4a85ceaf2e80e44682',
+      '661bf4e49dff3c104784a0d75cf45204',
+      '0b3529f1337b3759e97733095a868d29',
+      '1522580f1e96c5ea5dc68ca7a720adee',
+      '5c08a30f498edf9962c8ff20a1ab4fba',
+      '69f4f6640eba043f4df2e6f109f07b90',
+      '62db9da306210856e44bb7f8a75a15fd',
+      '125f6fa99282a3b7e8937030a3aa2c6d',
+      '1cf817dd1a1710bfacb82ef71da94e4f',
+      '1eccd6e8e62985cb9955db4fd8c22d2f',
+      '4becc04d3263f2b362dd76c0e0eb6d7b',
+      '74ecd3c74beb88f2f7f02921a8de1143',
+      'ad6bf3865f8addf4233e3a83192f5464',
+      'edf54995d97ad818449f09d9b2fc86e2',
+      '89014c91ebb4075bdea2d52f2d35b4ae',
+      'cb59b4041a0a7bbf636ed4e3b30d06be',
+      '3dd69a72235c9b45e1f85c143e8f97bc',
+      'b08bec82fca775aeec2e4f400b20a4a0',
+      '79381e4fd8c1191f2fceb7ad30b3fd64',
+      'b8e5434a62d4b0a381363dca1152a0d5',
+      'f70e0798fa96df0b6e1d14d69fd0deaa',
+      '3d807e9c6306c16f2ee61a32e8081e2f',
+      '0646eefc0cfd913506051f0c8a900983',
+      'b5adb85aeaf88a23e7bafd29e63c03ac',
+      '7b269c3e21fe9e29285daba8c370073f',
+      '1a47af48f1e3158000d44ef59ab597da',
+      '2665c64ac2a9d919fff7420c0e770db3',
+      '27c0acf56ef48f3855fc20ea8810ff8d',
+      '2a9a03940008cdd6f9231f1f54dd94bf',
+      '86d87e3cb682646e5d1158898ed7913f',
+      '6a7b30ccd5a35694c515d22f165be589',
     ];
     printOnFailure('final expectedChecksums = <String>[');
     printOnFailure(checksums.map((e) => "  '$e',").join('\n'));
diff --git a/pkgs/native_assets_cli/test/code_assets/config_test.dart b/pkgs/native_assets_cli/test/code_assets/config_test.dart
index b205e5b40..fe7943afa 100644
--- a/pkgs/native_assets_cli/test/code_assets/config_test.dart
+++ b/pkgs/native_assets_cli/test/code_assets/config_test.dart
@@ -91,7 +91,6 @@ void main() async {
       ..setupHookConfig(
         packageName: packageName,
         packageRoot: packageRootUri,
-        targetOS: OS.android,
         buildAssetTypes: [CodeAsset.type],
       )
       ..setupBuildConfig(
@@ -103,6 +102,7 @@ void main() async {
         outputDirectoryShared: outputDirectoryShared,
       )
       ..setupCodeConfig(
+        targetOS: OS.android,
         targetArchitecture: null, // not available in dry run
         cCompilerConfig: null, // not available in dry run
         linkModePreference: LinkModePreference.preferStatic,
@@ -116,7 +116,6 @@ void main() async {
       ..setupHookConfig(
         packageName: packageName,
         packageRoot: packageRootUri,
-        targetOS: OS.android,
         buildAssetTypes: [CodeAsset.type],
       )
       ..setupBuildConfig(
@@ -128,6 +127,7 @@ void main() async {
         outputDirectoryShared: outputDirectoryShared,
       )
       ..setupCodeConfig(
+        targetOS: OS.android,
         targetArchitecture: Architecture.arm64,
         targetAndroidNdkApi: 30,
         linkModePreference: LinkModePreference.preferStatic,
@@ -148,7 +148,6 @@ void main() async {
       ..setupHookConfig(
         packageName: packageName,
         packageRoot: packageRootUri,
-        targetOS: OS.android,
         buildAssetTypes: [CodeAsset.type],
       )
       ..setupLinkConfig(assets: assets)
@@ -158,6 +157,7 @@ void main() async {
         recordedUsesFile: null,
       )
       ..setupCodeConfig(
+        targetOS: OS.android,
         targetArchitecture: Architecture.arm64,
         targetAndroidNdkApi: 30,
         linkModePreference: LinkModePreference.preferStatic,
diff --git a/pkgs/native_assets_cli/test/code_assets/validation_test.dart b/pkgs/native_assets_cli/test/code_assets/validation_test.dart
index 4365f1712..09aa23571 100644
--- a/pkgs/native_assets_cli/test/code_assets/validation_test.dart
+++ b/pkgs/native_assets_cli/test/code_assets/validation_test.dart
@@ -29,12 +29,11 @@ void main() {
     await Directory.fromUri(tempUri).delete(recursive: true);
   });
 
-  BuildConfigBuilder makeBuildConfigBuilder({OS os = OS.iOS}) {
+  BuildConfigBuilder makeBuildConfigBuilder() {
     final configBuilder = BuildConfigBuilder()
       ..setupHookConfig(
         packageName: packageName,
         packageRoot: tempUri,
-        targetOS: os,
         buildAssetTypes: [CodeAsset.type],
       )
       ..setupBuildConfig(
@@ -48,12 +47,14 @@ void main() {
     return configBuilder;
   }
 
-  BuildConfig makeCodeBuildConfig(
-      {LinkModePreference linkModePreference = LinkModePreference.dynamic}) {
+  BuildConfig makeCodeBuildConfig({
+    LinkModePreference linkModePreference = LinkModePreference.dynamic,
+    OS os = OS.iOS,
+  }) {
     final builder = makeBuildConfigBuilder()
       ..setupCodeConfig(
+        targetOS: os,
         targetArchitecture: Architecture.arm64,
-        targetIOSSdk: IOSSdk.iPhoneOS,
         linkModePreference: linkModePreference,
       );
     return BuildConfig(builder.json);
@@ -66,7 +67,7 @@ void main() {
       package: config.packageName,
       name: 'foo.dylib',
       architecture: config.codeConfig.targetArchitecture,
-      os: config.targetOS,
+      os: config.codeConfig.targetOS,
       linkMode: DynamicLoadingBundled(),
     ));
     final errors = await validateCodeAssetBuildOutput(
@@ -93,7 +94,7 @@ void main() {
           name: 'foo.dart',
           file: assetFile.uri,
           linkMode: linkMode,
-          os: config.targetOS,
+          os: config.codeConfig.targetOS,
           architecture: config.codeConfig.targetArchitecture,
         ),
       );
@@ -119,7 +120,7 @@ void main() {
         name: 'foo.dart',
         file: assetFile.uri,
         linkMode: DynamicLoadingBundled(),
-        os: config.targetOS,
+        os: config.codeConfig.targetOS,
         architecture: Architecture.x64,
       ),
     );
@@ -144,7 +145,7 @@ void main() {
         name: 'foo.dart',
         file: assetFile.uri,
         linkMode: DynamicLoadingBundled(),
-        os: config.targetOS,
+        os: config.codeConfig.targetOS,
       ),
     );
     final errors = await validateCodeAssetBuildOutput(
@@ -185,7 +186,7 @@ void main() {
   test('duplicate dylib name', () async {
     final config = makeCodeBuildConfig();
     final outputBuilder = BuildOutputBuilder();
-    final fileName = config.targetOS.dylibFileName('foo');
+    final fileName = config.codeConfig.targetOS.dylibFileName('foo');
     final assetFile = File.fromUri(outDirUri.resolve(fileName));
     await assetFile.writeAsBytes([1, 2, 3]);
     outputBuilder.codeAssets.addAll([
@@ -194,7 +195,7 @@ void main() {
         name: 'src/foo.dart',
         file: assetFile.uri,
         linkMode: DynamicLoadingBundled(),
-        os: config.targetOS,
+        os: config.codeConfig.targetOS,
         architecture: config.codeConfig.targetArchitecture,
       ),
       CodeAsset(
@@ -202,7 +203,7 @@ void main() {
         name: 'src/bar.dart',
         file: assetFile.uri,
         linkMode: DynamicLoadingBundled(),
-        os: config.targetOS,
+        os: config.codeConfig.targetOS,
         architecture: config.codeConfig.targetArchitecture,
       ),
     ]);
@@ -216,10 +217,12 @@ void main() {
 
   group('BuildConfig.codeConfig validation', () {
     test('Missing targetIOSVersion', () async {
-      final builder = makeBuildConfigBuilder(os: OS.iOS)
+      final builder = makeBuildConfigBuilder()
         ..setupCodeConfig(
-            targetArchitecture: Architecture.arm64,
-            linkModePreference: LinkModePreference.dynamic);
+          targetOS: OS.iOS,
+          targetArchitecture: Architecture.arm64,
+          linkModePreference: LinkModePreference.dynamic,
+        );
       final errors =
           await validateCodeAssetBuildConfig(BuildConfig(builder.json));
       expect(
@@ -232,20 +235,24 @@ void main() {
               contains('BuildConfig.codeConfig.targetIOSSdk was missing')));
     });
     test('Missing targetAndroidNdkApi', () async {
-      final builder = makeBuildConfigBuilder(os: OS.android)
+      final builder = makeBuildConfigBuilder()
         ..setupCodeConfig(
-            targetArchitecture: Architecture.arm64,
-            linkModePreference: LinkModePreference.dynamic);
+          targetOS: OS.android,
+          targetArchitecture: Architecture.arm64,
+          linkModePreference: LinkModePreference.dynamic,
+        );
       expect(
           await validateCodeAssetBuildConfig(BuildConfig(builder.json)),
           contains(contains(
               'BuildConfig.codeConfig.targetAndroidNdkApi was missing')));
     });
     test('Missing targetMacOSVersion', () async {
-      final builder = makeBuildConfigBuilder(os: OS.macOS)
+      final builder = makeBuildConfigBuilder()
         ..setupCodeConfig(
-            targetArchitecture: Architecture.arm64,
-            linkModePreference: LinkModePreference.dynamic);
+          targetOS: OS.macOS,
+          targetArchitecture: Architecture.arm64,
+          linkModePreference: LinkModePreference.dynamic,
+        );
       expect(
           await validateCodeAssetBuildConfig(BuildConfig(builder.json)),
           contains(contains(
@@ -253,8 +260,9 @@ void main() {
     });
     test('Nonexisting compiler/archiver/linker/envScript', () async {
       final nonExistent = outDirUri.resolve('foo baz');
-      final builder = makeBuildConfigBuilder(os: OS.linux)
+      final builder = makeBuildConfigBuilder()
         ..setupCodeConfig(
+            targetOS: OS.linux,
             targetArchitecture: Architecture.arm64,
             linkModePreference: LinkModePreference.dynamic,
             cCompilerConfig: CCompilerConfig(
diff --git a/pkgs/native_assets_cli/test/data_assets/validation_test.dart b/pkgs/native_assets_cli/test/data_assets/validation_test.dart
index 422b2e6c9..f38180203 100644
--- a/pkgs/native_assets_cli/test/data_assets/validation_test.dart
+++ b/pkgs/native_assets_cli/test/data_assets/validation_test.dart
@@ -34,7 +34,6 @@ void main() {
       ..setupHookConfig(
           packageName: packageName,
           packageRoot: tempUri,
-          targetOS: OS.iOS,
           buildAssetTypes: [DataAsset.type])
       ..setupBuildConfig(
         linkingEnabled: false,
diff --git a/pkgs/native_assets_cli/test/example/local_asset_test.dart b/pkgs/native_assets_cli/test/example/local_asset_test.dart
index 5c9de1312..ce57a4b62 100644
--- a/pkgs/native_assets_cli/test/example/local_asset_test.dart
+++ b/pkgs/native_assets_cli/test/example/local_asset_test.dart
@@ -44,7 +44,6 @@ void main() async {
         ..setupHookConfig(
           packageRoot: testPackageUri,
           packageName: name,
-          targetOS: OS.current,
           buildAssetTypes: [CodeAsset.type],
         )
         ..setupBuildRunConfig(
@@ -52,9 +51,11 @@ void main() async {
             outputDirectoryShared: outputDirectoryShared)
         ..setupBuildConfig(linkingEnabled: false, dryRun: dryRun)
         ..setupCodeConfig(
-            targetArchitecture: dryRun ? null : Architecture.current,
-            linkModePreference: LinkModePreference.dynamic,
-            cCompilerConfig: dryRun ? null : cCompiler);
+          targetOS: OS.current,
+          targetArchitecture: dryRun ? null : Architecture.current,
+          linkModePreference: LinkModePreference.dynamic,
+          cCompilerConfig: dryRun ? null : cCompiler,
+        );
 
       final buildConfigUri = testTempUri.resolve('build_config.json');
       await File.fromUri(buildConfigUri)
diff --git a/pkgs/native_assets_cli/test/example/native_add_library_test.dart b/pkgs/native_assets_cli/test/example/native_add_library_test.dart
index 3d9c9b14c..2a3415901 100644
--- a/pkgs/native_assets_cli/test/example/native_add_library_test.dart
+++ b/pkgs/native_assets_cli/test/example/native_add_library_test.dart
@@ -44,7 +44,6 @@ void main() async {
         ..setupHookConfig(
           packageRoot: testPackageUri,
           packageName: name,
-          targetOS: OS.current,
           buildAssetTypes: [CodeAsset.type],
         )
         ..setupBuildRunConfig(
@@ -52,9 +51,11 @@ void main() async {
             outputDirectoryShared: outputDirectoryShared)
         ..setupBuildConfig(linkingEnabled: false, dryRun: dryRun)
         ..setupCodeConfig(
-            targetArchitecture: dryRun ? null : Architecture.current,
-            linkModePreference: LinkModePreference.dynamic,
-            cCompilerConfig: dryRun ? null : cCompiler);
+          targetOS: OS.current,
+          targetArchitecture: dryRun ? null : Architecture.current,
+          linkModePreference: LinkModePreference.dynamic,
+          cCompilerConfig: dryRun ? null : cCompiler,
+        );
 
       final buildConfigUri = testTempUri.resolve('build_config.json');
       await File.fromUri(buildConfigUri)
diff --git a/pkgs/native_assets_cli/test/example/native_dynamic_linking_test.dart b/pkgs/native_assets_cli/test/example/native_dynamic_linking_test.dart
index 64b3f50de..f90d91f15 100644
--- a/pkgs/native_assets_cli/test/example/native_dynamic_linking_test.dart
+++ b/pkgs/native_assets_cli/test/example/native_dynamic_linking_test.dart
@@ -48,7 +48,6 @@ void main() async {
         ..setupHookConfig(
           packageRoot: testPackageUri,
           packageName: name,
-          targetOS: OS.current,
           buildAssetTypes: [CodeAsset.type],
         )
         ..setupBuildRunConfig(
@@ -57,6 +56,7 @@ void main() async {
         )
         ..setupBuildConfig(linkingEnabled: false, dryRun: dryRun)
         ..setupCodeConfig(
+          targetOS: OS.current,
           targetArchitecture: dryRun ? null : Architecture.current,
           linkModePreference: LinkModePreference.dynamic,
           cCompilerConfig: dryRun ? null : cCompiler,
diff --git a/pkgs/native_assets_cli/test/link_config_test.dart b/pkgs/native_assets_cli/test/link_config_test.dart
index dc87cc772..2cf9616ea 100644
--- a/pkgs/native_assets_cli/test/link_config_test.dart
+++ b/pkgs/native_assets_cli/test/link_config_test.dart
@@ -33,7 +33,6 @@ void main() async {
       ..setupHookConfig(
         packageName: packageName,
         packageRoot: packageRootUri,
-        targetOS: OS.android,
         buildAssetTypes: ['asset-type-1', 'asset-type-2'],
       )
       ..setupLinkConfig(assets: assets)
@@ -53,7 +52,6 @@ void main() async {
       'package_name': packageName,
       'package_root': packageRootUri.toFilePath(),
       'supported_asset_types': ['asset-type-1', 'asset-type-2'],
-      'target_os': 'android',
       'version': latestVersion.toString(),
     };
     expect(config.json, expectedConfigJson);
@@ -64,7 +62,6 @@ void main() async {
 
     expect(config.packageName, packageName);
     expect(config.packageRoot, packageRootUri);
-    expect(config.targetOS, OS.android);
     expect(config.buildAssetTypes, ['asset-type-1', 'asset-type-2']);
     expect(config.encodedAssets, assets);
   });
diff --git a/pkgs/native_assets_cli/test/validation_test.dart b/pkgs/native_assets_cli/test/validation_test.dart
index 8a45a1b96..fae2834d1 100644
--- a/pkgs/native_assets_cli/test/validation_test.dart
+++ b/pkgs/native_assets_cli/test/validation_test.dart
@@ -34,7 +34,6 @@ void main() {
       ..setupHookConfig(
         packageName: packageName,
         packageRoot: tempUri,
-        targetOS: OS.iOS,
         buildAssetTypes: ['my-asset-type'],
       )
       ..setupBuildConfig(
diff --git a/pkgs/native_toolchain_c/lib/src/cbuilder/cbuilder.dart b/pkgs/native_toolchain_c/lib/src/cbuilder/cbuilder.dart
index 9fda6b34f..c2e3c0a34 100644
--- a/pkgs/native_toolchain_c/lib/src/cbuilder/cbuilder.dart
+++ b/pkgs/native_toolchain_c/lib/src/cbuilder/cbuilder.dart
@@ -126,9 +126,10 @@ class CBuilder extends CTool implements Builder {
     await Directory.fromUri(outDir).create(recursive: true);
     final linkMode =
         getLinkMode(linkModePreference ?? config.codeConfig.linkModePreference);
-    final libUri =
-        outDir.resolve(config.targetOS.libraryFileName(name, linkMode));
-    final exeUri = outDir.resolve(config.targetOS.executableFileName(name));
+    final libUri = outDir
+        .resolve(config.codeConfig.targetOS.libraryFileName(name, linkMode));
+    final exeUri =
+        outDir.resolve(config.codeConfig.targetOS.executableFileName(name));
     final sources = [
       for (final source in this.sources)
         packageRoot.resolveUri(Uri.file(source)),
@@ -188,7 +189,7 @@ class CBuilder extends CTool implements Builder {
           name: assetName!,
           file: libUri,
           linkMode: linkMode,
-          os: config.targetOS,
+          os: config.codeConfig.targetOS,
           architecture:
               // ignore: deprecated_member_use
               config.dryRun ? null : config.codeConfig.targetArchitecture,
diff --git a/pkgs/native_toolchain_c/lib/src/cbuilder/clinker.dart b/pkgs/native_toolchain_c/lib/src/cbuilder/clinker.dart
index aa804863e..425944630 100644
--- a/pkgs/native_toolchain_c/lib/src/cbuilder/clinker.dart
+++ b/pkgs/native_toolchain_c/lib/src/cbuilder/clinker.dart
@@ -51,7 +51,7 @@ class CLinker extends CTool implements Linker {
     required LinkOutputBuilder output,
     required Logger? logger,
   }) async {
-    if (OS.current != OS.linux || config.targetOS != OS.linux) {
+    if (OS.current != OS.linux || config.codeConfig.targetOS != OS.linux) {
       throw UnsupportedError('Currently, only linux is supported for this '
           'feature. See also https://github.com/dart-lang/native/issues/1376');
     }
@@ -60,8 +60,8 @@ class CLinker extends CTool implements Linker {
     await Directory.fromUri(outDir).create(recursive: true);
     final linkMode =
         getLinkMode(linkModePreference ?? config.codeConfig.linkModePreference);
-    final libUri =
-        outDir.resolve(config.targetOS.libraryFileName(name, linkMode));
+    final libUri = outDir
+        .resolve(config.codeConfig.targetOS.libraryFileName(name, linkMode));
     final sources = [
       for (final source in this.sources)
         packageRoot.resolveUri(Uri.file(source)),
@@ -104,7 +104,7 @@ class CLinker extends CTool implements Linker {
         name: assetName!,
         file: libUri,
         linkMode: linkMode,
-        os: config.targetOS,
+        os: config.codeConfig.targetOS,
         architecture: config.codeConfig.targetArchitecture,
       ));
     }
diff --git a/pkgs/native_toolchain_c/lib/src/cbuilder/compiler_resolver.dart b/pkgs/native_toolchain_c/lib/src/cbuilder/compiler_resolver.dart
index 149b64df2..3e4854764 100644
--- a/pkgs/native_toolchain_c/lib/src/cbuilder/compiler_resolver.dart
+++ b/pkgs/native_toolchain_c/lib/src/cbuilder/compiler_resolver.dart
@@ -20,14 +20,12 @@ import '../tool/tool_instance.dart';
 // TODO(dacoharkes): This should support alternatives.
 // For example use Clang or MSVC on Windows.
 class CompilerResolver {
-  final HookConfig hookConfig;
   final CodeConfig codeConfig;
   final Logger? logger;
   final OS hostOS;
   final Architecture hostArchitecture;
 
   CompilerResolver({
-    required this.hookConfig,
     required this.codeConfig,
     required this.logger,
     OS? hostOS, // Only visible for testing.
@@ -49,7 +47,7 @@ class CompilerResolver {
       return result;
     }
 
-    final targetOS = hookConfig.targetOS;
+    final targetOS = codeConfig.targetOS;
     final targetArchitecture = codeConfig.targetArchitecture;
     final errorMessage =
         "No tools configured on host '${hostOS}_$hostArchitecture' with target "
@@ -60,7 +58,7 @@ class CompilerResolver {
 
   /// Select the right compiler for cross compiling to the specified target.
   Tool? _selectCompiler() {
-    final targetOS = hookConfig.targetOS;
+    final targetOS = codeConfig.targetOS;
     final targetArch = codeConfig.targetArchitecture;
 
     // TODO(dacoharkes): Support falling back on other tools.
@@ -135,7 +133,7 @@ class CompilerResolver {
       return result;
     }
 
-    final targetOS = hookConfig.targetOS;
+    final targetOS = codeConfig.targetOS;
     final targetArchitecture = codeConfig.targetArchitecture;
     final errorMessage =
         "No tools configured on host '${hostOS}_$hostArchitecture' with target "
@@ -146,7 +144,7 @@ class CompilerResolver {
 
   /// Select the right archiver for cross compiling to the specified target.
   Tool? _selectArchiver() {
-    final targetOS = hookConfig.targetOS;
+    final targetOS = codeConfig.targetOS;
     final targetArchitecture = codeConfig.targetArchitecture;
 
     // TODO(dacoharkes): Support falling back on other tools.
@@ -224,7 +222,7 @@ class CompilerResolver {
   }
 
   Future<ToolInstance> resolveLinker() async {
-    final targetOS = hookConfig.targetOS;
+    final targetOS = codeConfig.targetOS;
     final targetArchitecture = codeConfig.targetArchitecture;
     // First, check if the launcher provided a direct path to the compiler.
     var result = await _tryLoadLinkerFromConfig();
@@ -261,7 +259,7 @@ class CompilerResolver {
 
   /// Select the right compiler for cross compiling to the specified target.
   Tool? _selectLinker() {
-    final targetOS = hookConfig.targetOS;
+    final targetOS = codeConfig.targetOS;
     final targetArchitecture = codeConfig.targetArchitecture;
 
     if (targetOS == OS.macOS || targetOS == OS.iOS) return appleLd;
diff --git a/pkgs/native_toolchain_c/lib/src/cbuilder/ctool.dart b/pkgs/native_toolchain_c/lib/src/cbuilder/ctool.dart
index 13e9ff0ad..4234337e2 100644
--- a/pkgs/native_toolchain_c/lib/src/cbuilder/ctool.dart
+++ b/pkgs/native_toolchain_c/lib/src/cbuilder/ctool.dart
@@ -18,7 +18,7 @@ abstract class CTool {
 
   /// Name of the library or executable to build or link.
   ///
-  /// The filename will be decided by [LinkConfig.targetOS] and
+  /// The filename will be decided by [CodeConfig.targetOS] and
   /// [OSLibraryNaming.libraryFileName] or
   /// [OSLibraryNaming.executableFileName].
   ///
diff --git a/pkgs/native_toolchain_c/lib/src/cbuilder/run_cbuilder.dart b/pkgs/native_toolchain_c/lib/src/cbuilder/run_cbuilder.dart
index a4b8197c1..23d61225c 100644
--- a/pkgs/native_toolchain_c/lib/src/cbuilder/run_cbuilder.dart
+++ b/pkgs/native_toolchain_c/lib/src/cbuilder/run_cbuilder.dart
@@ -76,7 +76,7 @@ class RunCBuilder {
                 .whereType<Uri>()
                 .length ==
             1) {
-    if (config.targetOS == OS.windows && cppLinkStdLib != null) {
+    if (codeConfig.targetOS == OS.windows && cppLinkStdLib != null) {
       throw ArgumentError.value(
         cppLinkStdLib,
         'cppLinkStdLib',
@@ -85,8 +85,8 @@ class RunCBuilder {
     }
   }
 
-  late final _resolver = CompilerResolver(
-      hookConfig: config, codeConfig: codeConfig, logger: logger);
+  late final _resolver =
+      CompilerResolver(codeConfig: codeConfig, logger: logger);
 
   Future<ToolInstance> compiler() async => await _resolver.resolveCompiler();
 
@@ -139,7 +139,7 @@ class RunCBuilder {
     }
 
     final IOSSdk? targetIosSdk;
-    if (config.targetOS == OS.iOS) {
+    if (codeConfig.targetOS == OS.iOS) {
       targetIosSdk = codeConfig.targetIOSSdk;
     } else {
       targetIosSdk = null;
@@ -149,7 +149,7 @@ class RunCBuilder {
     // invoking clang. Mimic that behavior here.
     // See https://github.com/dart-lang/native/issues/171.
     final int? targetAndroidNdkApi;
-    if (config.targetOS == OS.android) {
+    if (codeConfig.targetOS == OS.android) {
       final minimumApi =
           codeConfig.targetArchitecture == Architecture.riscv64 ? 35 : 21;
       targetAndroidNdkApi = max(codeConfig.targetAndroidNdkApi!, minimumApi);
@@ -158,9 +158,9 @@ class RunCBuilder {
     }
 
     final targetIOSVersion =
-        config.targetOS == OS.iOS ? codeConfig.targetIOSVersion : null;
+        codeConfig.targetOS == OS.iOS ? codeConfig.targetIOSVersion : null;
     final targetMacOSVersion =
-        config.targetOS == OS.macOS ? codeConfig.targetMacOSVersion : null;
+        codeConfig.targetOS == OS.macOS ? codeConfig.targetMacOSVersion : null;
 
     final architecture = codeConfig.targetArchitecture;
     final sourceFiles = sources.map((e) => e.toFilePath()).toList();
@@ -219,24 +219,24 @@ class RunCBuilder {
     await runProcess(
       executable: toolInstance.uri,
       arguments: [
-        if (config.targetOS == OS.android) ...[
+        if (codeConfig.targetOS == OS.android) ...[
           '--target='
               '${androidNdkClangTargetFlags[architecture]!}'
               '${targetAndroidNdkApi!}',
           '--sysroot=${androidSysroot(toolInstance).toFilePath()}',
         ],
-        if (config.targetOS == OS.macOS)
+        if (codeConfig.targetOS == OS.macOS)
           '--target=${appleClangMacosTargetFlags[architecture]!}',
-        if (config.targetOS == OS.iOS)
+        if (codeConfig.targetOS == OS.iOS)
           '--target=${appleClangIosTargetFlags[architecture]![targetIosSdk]!}',
         if (targetIOSVersion != null) '-mios-version-min=$targetIOSVersion',
         if (targetMacOSVersion != null)
           '-mmacos-version-min=$targetMacOSVersion',
-        if (config.targetOS == OS.iOS) ...[
+        if (codeConfig.targetOS == OS.iOS) ...[
           '-isysroot',
           (await iosSdk(targetIosSdk!, logger: logger)).toFilePath(),
         ],
-        if (config.targetOS == OS.macOS) ...[
+        if (codeConfig.targetOS == OS.macOS) ...[
           '-isysroot',
           (await macosSdk(logger: logger)).toFilePath(),
         ],
@@ -280,14 +280,14 @@ class RunCBuilder {
           '-x',
           'c++',
           '-l',
-          cppLinkStdLib ?? defaultCppLinkStdLib[config.targetOS]!
+          cppLinkStdLib ?? defaultCppLinkStdLib[codeConfig.targetOS]!
         ],
         if (optimizationLevel != OptimizationLevel.unspecified)
           optimizationLevel.clangFlag(),
         ...linkerOptions?.preSourcesFlags(toolInstance.tool, sourceFiles) ?? [],
         // Support Android 15 page size by default, can be overridden by
         // passing [flags].
-        if (config.targetOS == OS.android) '-Wl,-z,max-page-size=16384',
+        if (codeConfig.targetOS == OS.android) '-Wl,-z,max-page-size=16384',
         ...flags,
         for (final MapEntry(key: name, :value) in defines.entries)
           if (value == null) '-D$name' else '-D$name=$value',
@@ -314,7 +314,7 @@ class RunCBuilder {
         ...linkerOptions?.postSourcesFlags(toolInstance.tool, sourceFiles) ??
             [],
         if (executable != null || dynamicLibrary != null) ...[
-          if (config.targetOS case OS.android || OS.linux)
+          if (codeConfig.targetOS case OS.android || OS.linux)
             // During bundling code assets are all placed in the same directory.
             // Setting this rpath allows the binary to find other code assets
             // it is linked against.
diff --git a/pkgs/native_toolchain_c/test/cbuilder/cbuilder_build_failure_test.dart b/pkgs/native_toolchain_c/test/cbuilder/cbuilder_build_failure_test.dart
index 164dde262..7e906878d 100644
--- a/pkgs/native_toolchain_c/test/cbuilder/cbuilder_build_failure_test.dart
+++ b/pkgs/native_toolchain_c/test/cbuilder/cbuilder_build_failure_test.dart
@@ -34,13 +34,13 @@ void main() {
         buildAssetTypes: [CodeAsset.type],
         packageName: name,
         packageRoot: tempUri,
-        targetOS: OS.current,
       )
       ..setupBuildConfig(
         linkingEnabled: false,
         dryRun: false,
       )
       ..setupCodeConfig(
+        targetOS: OS.current,
         targetArchitecture: Architecture.current,
         linkModePreference: LinkModePreference.dynamic,
         cCompilerConfig: cCompiler,
diff --git a/pkgs/native_toolchain_c/test/cbuilder/cbuilder_cross_android_test.dart b/pkgs/native_toolchain_c/test/cbuilder/cbuilder_cross_android_test.dart
index 6b3002c75..cb8e80201 100644
--- a/pkgs/native_toolchain_c/test/cbuilder/cbuilder_cross_android_test.dart
+++ b/pkgs/native_toolchain_c/test/cbuilder/cbuilder_cross_android_test.dart
@@ -149,13 +149,13 @@ Future<Uri> buildLib(
       buildAssetTypes: [CodeAsset.type],
       packageName: name,
       packageRoot: tempUri,
-      targetOS: OS.android,
     )
     ..setupBuildConfig(
       linkingEnabled: false,
       dryRun: false,
     )
     ..setupCodeConfig(
+      targetOS: OS.android,
       targetArchitecture: targetArchitecture,
       cCompilerConfig: cCompiler,
       targetAndroidNdkApi: androidNdkApi,
diff --git a/pkgs/native_toolchain_c/test/cbuilder/cbuilder_cross_ios_test.dart b/pkgs/native_toolchain_c/test/cbuilder/cbuilder_cross_ios_test.dart
index 29e78e72f..90e358aa5 100644
--- a/pkgs/native_toolchain_c/test/cbuilder/cbuilder_cross_ios_test.dart
+++ b/pkgs/native_toolchain_c/test/cbuilder/cbuilder_cross_ios_test.dart
@@ -75,13 +75,13 @@ void main() {
                   buildAssetTypes: [CodeAsset.type],
                   packageName: name,
                   packageRoot: tempUri,
-                  targetOS: OS.iOS,
                 )
                 ..setupBuildConfig(
                   linkingEnabled: false,
                   dryRun: false,
                 )
                 ..setupCodeConfig(
+                  targetOS: OS.iOS,
                   targetArchitecture: target,
                   linkModePreference: linkMode == DynamicLoadingBundled()
                       ? LinkModePreference.dynamic
@@ -233,13 +233,13 @@ Future<Uri> buildLib(
       buildAssetTypes: [CodeAsset.type],
       packageName: name,
       packageRoot: tempUri,
-      targetOS: OS.iOS,
     )
     ..setupBuildConfig(
       linkingEnabled: false,
       dryRun: false,
     )
     ..setupCodeConfig(
+      targetOS: OS.iOS,
       targetArchitecture: targetArchitecture,
       linkModePreference: linkMode == DynamicLoadingBundled()
           ? LinkModePreference.dynamic
diff --git a/pkgs/native_toolchain_c/test/cbuilder/cbuilder_cross_linux_host_test.dart b/pkgs/native_toolchain_c/test/cbuilder/cbuilder_cross_linux_host_test.dart
index c39d398d0..d0be152b7 100644
--- a/pkgs/native_toolchain_c/test/cbuilder/cbuilder_cross_linux_host_test.dart
+++ b/pkgs/native_toolchain_c/test/cbuilder/cbuilder_cross_linux_host_test.dart
@@ -47,13 +47,13 @@ void main() {
             buildAssetTypes: [CodeAsset.type],
             packageName: name,
             packageRoot: tempUri,
-            targetOS: OS.linux,
           )
           ..setupBuildConfig(
             linkingEnabled: false,
             dryRun: false,
           )
           ..setupCodeConfig(
+            targetOS: OS.linux,
             targetArchitecture: target,
             linkModePreference: linkMode == DynamicLoadingBundled()
                 ? LinkModePreference.dynamic
diff --git a/pkgs/native_toolchain_c/test/cbuilder/cbuilder_cross_macos_host_test.dart b/pkgs/native_toolchain_c/test/cbuilder/cbuilder_cross_macos_host_test.dart
index 129c8bec3..9df36f3ad 100644
--- a/pkgs/native_toolchain_c/test/cbuilder/cbuilder_cross_macos_host_test.dart
+++ b/pkgs/native_toolchain_c/test/cbuilder/cbuilder_cross_macos_host_test.dart
@@ -62,13 +62,13 @@ void main() {
               buildAssetTypes: [CodeAsset.type],
               packageName: name,
               packageRoot: tempUri,
-              targetOS: OS.macOS,
             )
             ..setupBuildConfig(
               linkingEnabled: false,
               dryRun: false,
             )
             ..setupCodeConfig(
+              targetOS: OS.macOS,
               targetArchitecture: target,
               linkModePreference: linkMode == DynamicLoadingBundled()
                   ? LinkModePreference.dynamic
@@ -163,13 +163,13 @@ Future<Uri> buildLib(
       buildAssetTypes: [CodeAsset.type],
       packageName: name,
       packageRoot: tempUri,
-      targetOS: OS.macOS,
     )
     ..setupBuildConfig(
       linkingEnabled: false,
       dryRun: false,
     )
     ..setupCodeConfig(
+      targetOS: OS.macOS,
       targetArchitecture: targetArchitecture,
       linkModePreference: linkMode == DynamicLoadingBundled()
           ? LinkModePreference.dynamic
diff --git a/pkgs/native_toolchain_c/test/cbuilder/cbuilder_cross_windows_host_test.dart b/pkgs/native_toolchain_c/test/cbuilder/cbuilder_cross_windows_host_test.dart
index 6c9532653..92109a604 100644
--- a/pkgs/native_toolchain_c/test/cbuilder/cbuilder_cross_windows_host_test.dart
+++ b/pkgs/native_toolchain_c/test/cbuilder/cbuilder_cross_windows_host_test.dart
@@ -66,13 +66,13 @@ void main() {
             buildAssetTypes: [CodeAsset.type],
             packageName: name,
             packageRoot: tempUri,
-            targetOS: OS.windows,
           )
           ..setupBuildConfig(
             linkingEnabled: false,
             dryRun: false,
           )
           ..setupCodeConfig(
+            targetOS: OS.windows,
             targetArchitecture: target,
             linkModePreference: linkMode == DynamicLoadingBundled()
                 ? LinkModePreference.dynamic
diff --git a/pkgs/native_toolchain_c/test/cbuilder/cbuilder_test.dart b/pkgs/native_toolchain_c/test/cbuilder/cbuilder_test.dart
index 4b0a30793..3873a5b85 100644
--- a/pkgs/native_toolchain_c/test/cbuilder/cbuilder_test.dart
+++ b/pkgs/native_toolchain_c/test/cbuilder/cbuilder_test.dart
@@ -48,13 +48,13 @@ void main() {
             buildAssetTypes: [CodeAsset.type],
             packageName: name,
             packageRoot: tempUri,
-            targetOS: OS.current,
           )
           ..setupBuildConfig(
             linkingEnabled: false,
             dryRun: false,
           )
           ..setupCodeConfig(
+            targetOS: OS.current,
             targetArchitecture: Architecture.current,
             // Ignored by executables.
             linkModePreference: LinkModePreference.dynamic,
@@ -97,7 +97,7 @@ void main() {
           (message) => message.contains(helloWorldCUri.toFilePath()),
         );
 
-        switch ((buildConfig.targetOS, pic)) {
+        switch ((buildConfig.codeConfig.targetOS, pic)) {
           case (OS.windows, _) || (_, null):
             expect(compilerInvocation, isNot(contains('-fPIC')));
             expect(compilerInvocation, isNot(contains('-fPIE')));
@@ -130,13 +130,13 @@ void main() {
             buildAssetTypes: [CodeAsset.type],
             packageName: name,
             packageRoot: tempUri,
-            targetOS: OS.current,
           )
           ..setupBuildConfig(
             linkingEnabled: false,
             dryRun: dryRun,
           )
           ..setupCodeConfig(
+            targetOS: OS.current,
             targetArchitecture: Architecture.current,
             linkModePreference: LinkModePreference.dynamic,
             cCompilerConfig: dryRun ? null : cCompiler,
@@ -172,7 +172,7 @@ void main() {
           final compilerInvocation = logMessages.singleWhere(
             (message) => message.contains(addCUri.toFilePath()),
           );
-          switch ((buildConfig.targetOS, pic)) {
+          switch ((buildConfig.codeConfig.targetOS, pic)) {
             case (OS.windows, _) || (_, null):
               expect(compilerInvocation, isNot(contains('-fPIC')));
               expect(compilerInvocation, isNot(contains('-fPIE')));
@@ -231,13 +231,13 @@ void main() {
         buildAssetTypes: [CodeAsset.type],
         packageName: name,
         packageRoot: tempUri,
-        targetOS: OS.current,
       )
       ..setupBuildConfig(
         linkingEnabled: false,
         dryRun: false,
       )
       ..setupCodeConfig(
+        targetOS: OS.current,
         targetArchitecture: Architecture.current,
         // Ignored by executables.
         linkModePreference: LinkModePreference.dynamic,
@@ -250,7 +250,7 @@ void main() {
     final buildConfig = BuildConfig(buildConfigBuilder.json);
     final buildOutput = BuildOutputBuilder();
 
-    final flag = switch (buildConfig.targetOS) {
+    final flag = switch (buildConfig.codeConfig.targetOS) {
       OS.windows => '/DFOO=USER_FLAG',
       _ => '-DFOO=USER_FLAG',
     };
@@ -298,13 +298,13 @@ void main() {
         buildAssetTypes: [CodeAsset.type],
         packageName: name,
         packageRoot: tempUri,
-        targetOS: OS.current,
       )
       ..setupBuildConfig(
         linkingEnabled: false,
         dryRun: false,
       )
       ..setupCodeConfig(
+        targetOS: OS.current,
         targetArchitecture: Architecture.current,
         // Ignored by executables.
         linkModePreference: LinkModePreference.dynamic,
@@ -354,13 +354,13 @@ void main() {
         buildAssetTypes: [CodeAsset.type],
         packageName: name,
         packageRoot: tempUri,
-        targetOS: OS.current,
       )
       ..setupBuildConfig(
         linkingEnabled: false,
         dryRun: false,
       )
       ..setupCodeConfig(
+        targetOS: OS.current,
         targetArchitecture: Architecture.current,
         // Ignored by executables.
         linkModePreference: LinkModePreference.dynamic,
@@ -373,7 +373,7 @@ void main() {
     final buildConfig = BuildConfig(buildConfigBuilder.json);
     final buildOutput = BuildOutputBuilder();
 
-    final stdFlag = switch (buildConfig.targetOS) {
+    final stdFlag = switch (buildConfig.codeConfig.targetOS) {
       OS.windows => '/std:$std',
       _ => '-std=$std',
     };
@@ -422,13 +422,13 @@ void main() {
         buildAssetTypes: [CodeAsset.type],
         packageName: name,
         packageRoot: tempUri,
-        targetOS: OS.current,
       )
       ..setupBuildConfig(
         linkingEnabled: false,
         dryRun: false,
       )
       ..setupCodeConfig(
+        targetOS: OS.current,
         targetArchitecture: Architecture.current,
         // Ignored by executables.
         linkModePreference: LinkModePreference.dynamic,
@@ -441,7 +441,7 @@ void main() {
     final buildConfig = BuildConfig(buildConfigBuilder.json);
     final buildOutput = BuildOutputBuilder();
 
-    final defaultStdLibLinkFlag = switch (buildConfig.targetOS) {
+    final defaultStdLibLinkFlag = switch (buildConfig.codeConfig.targetOS) {
       OS.windows => null,
       OS.linux => '-l stdc++',
       OS.macOS => '-l c++',
@@ -495,13 +495,13 @@ void main() {
         buildAssetTypes: [CodeAsset.type],
         packageName: name,
         packageRoot: tempUri,
-        targetOS: OS.current,
       )
       ..setupBuildConfig(
         linkingEnabled: false,
         dryRun: false,
       )
       ..setupCodeConfig(
+        targetOS: OS.current,
         targetArchitecture: Architecture.current,
         // Ignored by executables.
         linkModePreference: LinkModePreference.dynamic,
@@ -522,7 +522,7 @@ void main() {
       buildMode: BuildMode.release,
     );
 
-    if (buildConfig.targetOS == OS.windows) {
+    if (buildConfig.codeConfig.targetOS == OS.windows) {
       await expectLater(
         () => cbuilder.run(
           config: buildConfig,
@@ -579,13 +579,13 @@ void main() {
         buildAssetTypes: [CodeAsset.type],
         packageName: name,
         packageRoot: tempUri,
-        targetOS: OS.current,
       )
       ..setupBuildConfig(
         linkingEnabled: false,
         dryRun: false,
       )
       ..setupCodeConfig(
+        targetOS: OS.current,
         targetArchitecture: Architecture.current,
         // Ignored by executables.
         linkModePreference: LinkModePreference.dynamic,
@@ -680,13 +680,13 @@ Future<void> testDefines({
       buildAssetTypes: [CodeAsset.type],
       packageName: name,
       packageRoot: tempUri,
-      targetOS: OS.current,
     )
     ..setupBuildConfig(
       linkingEnabled: false,
       dryRun: false,
     )
     ..setupCodeConfig(
+      targetOS: OS.current,
       targetArchitecture: Architecture.current,
       // Ignored by executables.
       linkModePreference: LinkModePreference.dynamic,
diff --git a/pkgs/native_toolchain_c/test/cbuilder/compiler_resolver_test.dart b/pkgs/native_toolchain_c/test/cbuilder/compiler_resolver_test.dart
index b4c1ddf01..929312368 100644
--- a/pkgs/native_toolchain_c/test/cbuilder/compiler_resolver_test.dart
+++ b/pkgs/native_toolchain_c/test/cbuilder/compiler_resolver_test.dart
@@ -46,13 +46,13 @@ void main() {
         buildAssetTypes: [CodeAsset.type],
         packageName: 'dummy',
         packageRoot: tempUri,
-        targetOS: OS.current,
       )
       ..setupBuildConfig(
         linkingEnabled: false,
         dryRun: false,
       )
       ..setupCodeConfig(
+        targetOS: OS.current,
         targetArchitecture: Architecture.current,
         linkModePreference: LinkModePreference.dynamic,
         cCompilerConfig: CCompilerConfig(
@@ -67,10 +67,8 @@ void main() {
       outputDirectoryShared: tempUri2,
     );
     final buildConfig = BuildConfig(buildConfigBuilder.json);
-    final resolver = CompilerResolver(
-        hookConfig: buildConfig,
-        codeConfig: buildConfig.codeConfig,
-        logger: logger);
+    final resolver =
+        CompilerResolver(codeConfig: buildConfig.codeConfig, logger: logger);
     final compiler = await resolver.resolveCompiler();
     final archiver = await resolver.resolveArchiver();
     expect(compiler.uri, buildConfig.codeConfig.cCompiler.compiler);
@@ -85,13 +83,13 @@ void main() {
         buildAssetTypes: [CodeAsset.type],
         packageName: 'dummy',
         packageRoot: tempUri,
-        targetOS: OS.windows,
       )
       ..setupBuildConfig(
         linkingEnabled: false,
         dryRun: false,
       )
       ..setupCodeConfig(
+        targetOS: OS.windows,
         targetArchitecture: Architecture.arm64,
         linkModePreference: LinkModePreference.dynamic,
         cCompilerConfig: cCompiler,
@@ -104,7 +102,6 @@ void main() {
     final buildConfig = BuildConfig(buildConfigBuilder.json);
 
     final resolver = CompilerResolver(
-      hookConfig: buildConfig,
       codeConfig: buildConfig.codeConfig,
       logger: logger,
       hostOS: OS.android, // This is never a host.
diff --git a/pkgs/native_toolchain_c/test/cbuilder/objective_c_test.dart b/pkgs/native_toolchain_c/test/cbuilder/objective_c_test.dart
index 23f8fe9ca..e251080a2 100644
--- a/pkgs/native_toolchain_c/test/cbuilder/objective_c_test.dart
+++ b/pkgs/native_toolchain_c/test/cbuilder/objective_c_test.dart
@@ -40,13 +40,13 @@ void main() {
         buildAssetTypes: [CodeAsset.type],
         packageName: name,
         packageRoot: tempUri,
-        targetOS: OS.current,
       )
       ..setupBuildConfig(
         linkingEnabled: false,
         dryRun: false,
       )
       ..setupCodeConfig(
+        targetOS: OS.current,
         targetArchitecture: Architecture.current,
         linkModePreference: LinkModePreference.dynamic,
         cCompilerConfig: cCompiler,
diff --git a/pkgs/native_toolchain_c/test/clinker/build_testfiles.dart b/pkgs/native_toolchain_c/test/clinker/build_testfiles.dart
index fe183eb09..2dbc32946 100644
--- a/pkgs/native_toolchain_c/test/clinker/build_testfiles.dart
+++ b/pkgs/native_toolchain_c/test/clinker/build_testfiles.dart
@@ -30,13 +30,13 @@ Future<Uri> buildTestArchive(
       buildAssetTypes: [CodeAsset.type],
       packageName: name,
       packageRoot: tempUri,
-      targetOS: os,
     )
     ..setupBuildConfig(
       linkingEnabled: false,
       dryRun: false,
     )
     ..setupCodeConfig(
+      targetOS: os,
       targetArchitecture: architecture,
       linkModePreference: LinkModePreference.dynamic,
       cCompilerConfig: cCompiler,
diff --git a/pkgs/native_toolchain_c/test/clinker/objects_test.dart b/pkgs/native_toolchain_c/test/clinker/objects_test.dart
index d080e984a..0797b194c 100644
--- a/pkgs/native_toolchain_c/test/clinker/objects_test.dart
+++ b/pkgs/native_toolchain_c/test/clinker/objects_test.dart
@@ -36,12 +36,12 @@ Future<void> main() async {
         buildAssetTypes: [CodeAsset.type],
         packageName: 'testpackage',
         packageRoot: tempUri,
-        targetOS: os,
       )
       ..setupLinkConfig(
         assets: [],
       )
       ..setupCodeConfig(
+        targetOS: os,
         targetArchitecture: architecture,
         linkModePreference: LinkModePreference.dynamic,
         cCompilerConfig: cCompiler,
diff --git a/pkgs/native_toolchain_c/test/clinker/throws_test.dart b/pkgs/native_toolchain_c/test/clinker/throws_test.dart
index 149f09001..9a1c2a633 100644
--- a/pkgs/native_toolchain_c/test/clinker/throws_test.dart
+++ b/pkgs/native_toolchain_c/test/clinker/throws_test.dart
@@ -27,12 +27,12 @@ Future<void> main() async {
             buildAssetTypes: [CodeAsset.type],
             packageName: 'testpackage',
             packageRoot: tempUri,
-            targetOS: os,
           )
           ..setupLinkConfig(
             assets: [],
           )
           ..setupCodeConfig(
+            targetOS: os,
             targetArchitecture: Architecture.x64,
             linkModePreference: LinkModePreference.dynamic,
             cCompilerConfig: cCompiler,
diff --git a/pkgs/native_toolchain_c/test/clinker/treeshake_helper.dart b/pkgs/native_toolchain_c/test/clinker/treeshake_helper.dart
index 322d9ba04..d8d55c88b 100644
--- a/pkgs/native_toolchain_c/test/clinker/treeshake_helper.dart
+++ b/pkgs/native_toolchain_c/test/clinker/treeshake_helper.dart
@@ -66,12 +66,12 @@ Future<void> runTests(List<Architecture> architectures) async {
             buildAssetTypes: [CodeAsset.type],
             packageName: 'testpackage',
             packageRoot: tempUri,
-            targetOS: os,
           )
           ..setupLinkConfig(
             assets: [],
           )
           ..setupCodeConfig(
+            targetOS: os,
             targetArchitecture: architecture,
             linkModePreference: LinkModePreference.dynamic,
             cCompilerConfig: cCompiler,