diff --git a/build_runner/bin/src/commands/generate_build_script.dart b/build_runner/bin/src/commands/generate_build_script.dart
index 25418513c..15ddc0893 100644
--- a/build_runner/bin/src/commands/generate_build_script.dart
+++ b/build_runner/bin/src/commands/generate_build_script.dart
@@ -33,7 +33,12 @@ class GenerateBuildScript extends Command<int> {
     var buildScript = await generateBuildScript();
     File(scriptLocation)
       ..createSync(recursive: true)
-      ..writeAsStringSync(buildScript);
+      ..writeAsStringSync(buildScript.script);
+    File(scriptDepsPath)
+      ..createSync(recursive: true)
+      ..writeAsStringSync(
+        '$scriptLocation: ${buildScript.dependencyPaths.join(' ')}',
+      );
     print(p.absolute(scriptLocation));
     return 0;
   }
diff --git a/build_runner/lib/src/build_script_generate/bootstrap.dart b/build_runner/lib/src/build_script_generate/bootstrap.dart
index dd82680a1..9134c85de 100644
--- a/build_runner/lib/src/build_script_generate/bootstrap.dart
+++ b/build_runner/lib/src/build_script_generate/bootstrap.dart
@@ -26,31 +26,29 @@ import 'build_script_generate.dart';
 /// Returns the exit code from running the build script.
 ///
 /// If an exit code of 75 is returned, this function should be re-ran.
+///
+/// Pass [script] to override the default build script for testing.
 Future<int> generateAndRun(
   List<String> args, {
   List<String>? experiments,
   Logger? logger,
-  Future<String> Function() generateBuildScript = generateBuildScript,
   void Function(Object error, StackTrace stackTrace) handleUncaughtError =
       _defaultHandleUncaughtError,
+  GeneratedScript? script,
 }) {
   return buildLog.runWithLoggerDisplay(
     logger,
-    () => _generateAndRun(
-      args,
-      experiments,
-      generateBuildScript,
-      handleUncaughtError,
-    ),
+    () =>
+        _generateAndRun(args, experiments, handleUncaughtError, script: script),
   );
 }
 
 Future<int> _generateAndRun(
   List<String> args,
   List<String>? experiments,
-  Future<String> Function() generateBuildScript,
-  void Function(Object error, StackTrace stackTrace) handleUncaughtError,
-) async {
+  void Function(Object error, StackTrace stackTrace) handleUncaughtError, {
+  GeneratedScript? script,
+}) async {
   experiments ??= [];
   ReceivePort? exitPort;
   ReceivePort? errorPort;
@@ -72,12 +70,17 @@ Future<int> _generateAndRun(
       if (buildScript.existsSync()) {
         oldContents = buildScript.readAsStringSync();
       }
-      var newContents = await generateBuildScript();
+      var newContents = script ?? await generateBuildScript();
       // Only trigger a build script update if necessary.
-      if (newContents != oldContents) {
+      if (newContents.script != oldContents) {
         buildScript
           ..createSync(recursive: true)
-          ..writeAsStringSync(newContents);
+          ..writeAsStringSync(newContents.script);
+        File(scriptDepsPath)
+          ..createSync(recursive: true)
+          ..writeAsStringSync(
+            '$scriptLocation: ${newContents.dependencyPaths.join(' ')}',
+          );
         // Delete the kernel file so it will be rebuilt.
         final kernelFile = File(scriptKernelLocation);
         if (kernelFile.existsSync()) {
@@ -183,7 +186,7 @@ Future<bool> _createKernelIfNeeded(List<String> experiments) async {
     }
   }
 
-  if (!kernelFile.existsSync()) {
+  if (!kernelFile.existsSync() || true) {
     final client = await FrontendServerClient.start(
       scriptLocation,
       scriptKernelCachedLocation,
@@ -196,9 +199,11 @@ Future<bool> _createKernelIfNeeded(List<String> experiments) async {
     var hadErrors = false;
     buildLog.doing('Compiling the build script.');
     try {
+      if (kernelCacheFile.existsSync()) kernelCacheFile.deleteSync();
       final result = await client.compile();
+      buildLog.debug(result.jsSourcesOutput.toString());
+      buildLog.debug('built ${kernelCacheFile.path}');
       hadErrors = result.errorCount > 0 || !kernelCacheFile.existsSync();
-
       // Note: We're logging all output with a single log call to keep
       // annotated source spans intact.
       final logOutput = result.compilerOutputLines.join('\n');
diff --git a/build_runner/lib/src/build_script_generate/build_script_generate.dart b/build_runner/lib/src/build_script_generate/build_script_generate.dart
index 600869bf2..13b4da3cb 100644
--- a/build_runner/lib/src/build_script_generate/build_script_generate.dart
+++ b/build_runner/lib/src/build_script_generate/build_script_generate.dart
@@ -17,6 +17,7 @@ import '../package_graph/build_config_overrides.dart';
 import 'builder_ordering.dart';
 
 const scriptLocation = '$entryPointDir/build.dart';
+const scriptDepsPath = '$entryPointDir/build.dart.deps';
 const scriptKernelLocation = '$scriptLocation$scriptKernelSuffix';
 const scriptKernelSuffix = '.dill';
 const scriptKernelCachedLocation =
@@ -25,7 +26,7 @@ const scriptKernelCachedSuffix = '.cached';
 
 final _lastShortFormatDartVersion = Version(3, 6, 0);
 
-Future<String> generateBuildScript() async {
+Future<GeneratedScript> generateBuildScript() async {
   buildLog.doing('Generating the build script.');
   final info = await findBuildScriptOptions();
   final builders = info.builderApplications;
@@ -55,14 +56,15 @@ Future<String> generateBuildScript() async {
     // the host<->isolate relationship changed in a breaking way, for example
     // if command line args or messages passed via sendports have changed
     // in a breaking way.
-    return DartFormatter(languageVersion: _lastShortFormatDartVersion).format(
-      '''
+    final script = DartFormatter(
+      languageVersion: _lastShortFormatDartVersion,
+    ).format('''
 // @dart=${_lastShortFormatDartVersion.major}.${_lastShortFormatDartVersion.minor}
 // ignore_for_file: directives_ordering
 // build_runner >=2.4.16
 ${library.accept(emitter)}
-''',
-    );
+''');
+    return GeneratedScript(script: script, dependencyPaths: info.inputs);
   } on FormatterException {
     buildLog.error(
       'Generated build script could not be parsed. '
@@ -195,13 +197,20 @@ Future<BuildScriptInfo> findBuildScriptOptions({
       _applyPostProcessBuilder(builder),
   ];
 
-  return BuildScriptInfo(applications);
+  final inputs = <String>[];
+  for (final package in packageGraph.allPackages.values) {
+    inputs.add('${package.path}/build.yaml');
+  }
+  inputs.sort();
+
+  return BuildScriptInfo(inputs, applications);
 }
 
 class BuildScriptInfo {
+  final List<String> inputs;
   final Iterable<Expression> builderApplications;
 
-  BuildScriptInfo(this.builderApplications);
+  BuildScriptInfo(this.inputs, this.builderApplications);
 }
 
 /// A method forwarding to `run`.
@@ -409,3 +418,10 @@ extension ConvertToExpression on Object? {
     }
   }
 }
+
+class GeneratedScript {
+  String script;
+  List<String> dependencyPaths;
+
+  GeneratedScript({required this.script, required this.dependencyPaths});
+}
diff --git a/build_runner/lib/src/compiler/compiler.dart b/build_runner/lib/src/compiler/compiler.dart
new file mode 100644
index 000000000..12129bce8
--- /dev/null
+++ b/build_runner/lib/src/compiler/compiler.dart
@@ -0,0 +1,73 @@
+// Copyright (c) 2025, the Dart project authors.  Please see the AUTHORS file
+// for details. All rights reserved. Use of this source code is governed by a
+// BSD-style license that can be found in the LICENSE file.
+
+import 'dart:async';
+import 'dart:convert';
+import 'dart:io';
+
+import 'package:convert/convert.dart';
+import 'package:crypto/crypto.dart';
+
+void main(List<String> arguments) async {
+  await Compiler().compile(arguments[0]);
+}
+
+class Compiler {
+  Future<void> compile(String path) async {
+    final depfilePath = '$path.deps';
+    final digestFilePath = '$path.digest';
+
+    final depfile = File(depfilePath);
+    final digestFile = File(digestFilePath);
+
+    if (depfile.existsSync() && digestFile.existsSync()) {
+      final expectedDigest = digestFile.readAsStringSync();
+      final actualDigest = computeDigest(parseDepfile(depfilePath));
+      if (expectedDigest == actualDigest) {
+        print('Input digests matched, nothing to do.');
+        return;
+      } else {
+        print(
+          'Input digests changed from $expectedDigest to $actualDigest, rebuild.',
+        );
+      }
+    }
+
+    final result = await Process.run('dart', [
+      'compile',
+      'kernel',
+      path,
+      '--depfile',
+      depfilePath,
+    ]);
+    if (result.exitCode != 0) {
+      print('Compile failed: ${result.stdout} ${result.stderr}');
+      exit(1);
+    }
+    final deps = parseDepfile(depfilePath);
+    final digest = computeDigest(deps);
+    digestFile.writeAsStringSync(digest);
+
+    //unawaited(dill.then((result) => print(result.stdout)));
+  }
+
+  List<String> parseDepfile(String depfilePath) {
+    // TODO(davidmorgan): handle spaces, they seem to be backslash escaped.
+    final result =
+        File(depfilePath).readAsStringSync().split(' ').skip(1).toList();
+    // File ends in a newline.
+    result.last = result.last.substring(0, result.last.length - 1);
+    return result;
+  }
+
+  String computeDigest(Iterable<String> deps) {
+    final digestSink = AccumulatorSink<Digest>();
+    final result = md5.startChunkedConversion(digestSink);
+    for (final dep in deps) {
+      result.add(File(dep).readAsBytesSync());
+    }
+    result.close();
+    return base64.encode(digestSink.events.first.bytes);
+  }
+}
diff --git a/build_runner/lib/src/compiler/compiler.exe b/build_runner/lib/src/compiler/compiler.exe
new file mode 100755
index 000000000..bf7d8aa1b
Binary files /dev/null and b/build_runner/lib/src/compiler/compiler.exe differ
diff --git a/build_runner/lib/src/compiler/external_build_step.dart b/build_runner/lib/src/compiler/external_build_step.dart
new file mode 100644
index 000000000..dab829926
--- /dev/null
+++ b/build_runner/lib/src/compiler/external_build_step.dart
@@ -0,0 +1,50 @@
+// Copyright (c) 2025, the Dart project authors.  Please see the AUTHORS file
+// for details. All rights reserved. Use of this source code is governed by a
+// BSD-style license that can be found in the LICENSE file.
+
+import 'dart:convert';
+import 'dart:io';
+
+import 'package:convert/convert.dart';
+import 'package:crypto/crypto.dart';
+
+class ExternalBuildStep {
+  List<String> inputPaths;
+  String outputPath;
+
+  ExternalBuildStep({required this.inputPaths, required this.outputPath});
+
+  String get depsPath => '$outputPath.deps';
+  String get digestsPath => '$outputPath.digests';
+
+  bool needsToRun() {
+    if (!File(depsPath).existsSync()) return true;
+    if (!File(outputPath).existsSync()) return true;
+    if (!File(digestsPath).existsSync()) return true;
+
+    final digests = computeDigests();
+    final oldDigests = File(digestsPath).readAsStringSync();
+    return digests != oldDigests;
+  }
+
+  void stamp() {
+    // TODO(davidmorgan): spaces.
+    File(depsPath).writeAsStringSync('$outputPath: ${inputPaths.join(' ')}');
+    File(digestsPath).writeAsStringSync(computeDigests());
+  }
+
+  String computeDigests() => '''
+inputs digest: ${_computeDigest(inputPaths)}
+output digest: ${_computeDigest([outputPath])}
+''';
+
+  String _computeDigest(Iterable<String> deps) {
+    final digestSink = AccumulatorSink<Digest>();
+    final result = md5.startChunkedConversion(digestSink);
+    for (final dep in deps) {
+      result.add(File(dep).readAsBytesSync());
+    }
+    result.close();
+    return base64.encode(digestSink.events.first.bytes);
+  }
+}
diff --git a/build_runner/lib/src/daemon/daemon_builder.dart b/build_runner/lib/src/daemon/daemon_builder.dart
index 1c9be5913..c1e39144c 100644
--- a/build_runner/lib/src/daemon/daemon_builder.dart
+++ b/build_runner/lib/src/daemon/daemon_builder.dart
@@ -77,11 +77,8 @@ class BuildRunnerDaemonBuilder implements DaemonBuilder {
               (change) => AssetChange(AssetId.parse(change.path), change.type),
             )
             .toList();
-
-    if (!_buildOptions.skipBuildScriptCheck &&
-        _buildSeries.buildScriptUpdates!.hasBeenUpdated(
-          changes.map<AssetId>((change) => change.id).toSet(),
-        )) {
+    // ignore_for_file: dead_code
+    if (!_buildOptions.skipBuildScriptCheck && false) {
       if (!_buildScriptUpdateCompleter.isCompleted) {
         _buildScriptUpdateCompleter.complete();
       }
diff --git a/build_runner/lib/src/generate/watch_impl.dart b/build_runner/lib/src/generate/watch_impl.dart
index 00440715a..5899522f6 100644
--- a/build_runner/lib/src/generate/watch_impl.dart
+++ b/build_runner/lib/src/generate/watch_impl.dart
@@ -257,9 +257,8 @@ class WatchImpl implements BuildState {
 
       _expectedDeletes.clear();
       if (!options.skipBuildScriptCheck) {
-        if (build.buildScriptUpdates!.hasBeenUpdated(
-          mergedChanges.keys.toSet(),
-        )) {
+        // ignore_for_file: dead_code
+        if (false) {
           _terminateCompleter.complete();
           buildLog.error('Terminating builds due to build script update.');
           return BuildResult(
diff --git a/build_runner/pubspec.yaml b/build_runner/pubspec.yaml
index 9cf7cdddf..c646c0b83 100644
--- a/build_runner/pubspec.yaml
+++ b/build_runner/pubspec.yaml
@@ -20,6 +20,7 @@ dependencies:
   build_daemon: ^4.0.0
   build_runner_core: '9.2.1-wip'
   code_builder: ^4.2.0
+  convert: ^3.1.2
   crypto: ^3.0.0
   dart_style: '>=2.3.7 <4.0.0'
   frontend_server_client: ">=3.0.0 <5.0.0"
diff --git a/build_runner/test/build_script_generate/bootstrap_test.dart b/build_runner/test/build_script_generate/bootstrap_test.dart
index 27fbb17cb..2e565876b 100644
--- a/build_runner/test/build_script_generate/bootstrap_test.dart
+++ b/build_runner/test/build_script_generate/bootstrap_test.dart
@@ -28,8 +28,7 @@ void main() {
     test('writes dill', () async {
       await generateAndRun(
         [],
-        generateBuildScript:
-            () async => '''
+        script: '''
 import 'dart:isolate';
 import 'package:build_runner/src/build_script_generate/build_process_state.dart';
 
@@ -55,9 +54,9 @@ void main(_, [SendPort? sendPort]) async {
 ''';
 
       buildProcessState.isolateExitCode = 6;
-      await generateAndRun([], generateBuildScript: () async => script);
+      await generateAndRun([], script: script);
       expect(buildProcessState.isolateExitCode, 7);
-      await generateAndRun([], generateBuildScript: () async => script);
+      await generateAndRun([], script: script);
       expect(buildProcessState.isolateExitCode, 8);
     });
 
@@ -65,8 +64,7 @@ void main(_, [SendPort? sendPort]) async {
       expect(
         await generateAndRun(
           [],
-          generateBuildScript:
-              () async => '''
+          script: '''
 import 'dart:isolate';
 import 'package:build_runner/src/build_script_generate/build_process_state.dart';
 
@@ -84,8 +82,7 @@ void main(_, [SendPort? sendPort]) async {
       expect(
         await generateAndRun(
           [],
-          generateBuildScript:
-              () async => '''
+          script: '''
 import 'dart:isolate';
 import 'package:build_runner/src/build_script_generate/build_process_state.dart';
 
@@ -109,8 +106,7 @@ void main(_, [SendPort? sendPort]) async {
         expect(
           await generateAndRun(
             [],
-            generateBuildScript:
-                () async => '''
+            script: '''
 import 'dart:isolate';
 import 'package:build_runner/src/build_script_generate/build_process_state.dart';
 
@@ -132,8 +128,7 @@ void main(_, [SendPort? sendPort]) async {
         expect(
           await generateAndRun(
             [],
-            generateBuildScript:
-                () async => '''
+            script: '''
 import 'dart:isolate';
 import 'package:build_runner/src/build_script_generate/build_process_state.dart';
 
@@ -156,8 +151,7 @@ void main(_, [SendPort? sendPort]) async {
       await expectLater(
         generateAndRun(
           [],
-          generateBuildScript: () async {
-            return '''
+          script: '''
 import 'dart:isolate';
 import 'package:build_runner/src/build_script_generate/build_process_state.dart';
 
@@ -165,8 +159,7 @@ void main(_, [SendPort? sendPort]) async {
   await buildProcessState.receive(sendPort);
   throw 'expected error';
 }
-''';
-          },
+''',
           handleUncaughtError: (err, trace) {
             error = err;
             stackTrace = trace;
diff --git a/build_runner/test/build_script_generate/experiments_test.dart b/build_runner/test/build_script_generate/experiments_test.dart
index 2b81fde92..65421d79a 100644
--- a/build_runner/test/build_script_generate/experiments_test.dart
+++ b/build_runner/test/build_script_generate/experiments_test.dart
@@ -17,8 +17,7 @@ void main() {
     final exitCode = await generateAndRun(
       [],
       experiments: ['records'],
-      generateBuildScript: () async {
-        return '''
+      script: '''
               // @dart=3.0
               import 'dart:io';
               import 'dart:isolate';
@@ -30,8 +29,7 @@ void main() {
                 buildProcessState.isolateExitCode = (x.\$2);
                 buildProcessState.send(sendPort);
               }
-              ''';
-      },
+              ''',
       logger: logger,
     );
     expect(exitCode, 2);
diff --git a/build_runner_core/lib/src/changes/build_script_updates.dart b/build_runner_core/lib/src/changes/build_script_updates.dart
deleted file mode 100644
index b68039476..000000000
--- a/build_runner_core/lib/src/changes/build_script_updates.dart
+++ /dev/null
@@ -1,161 +0,0 @@
-// Copyright (c) 2017, the Dart project authors.  Please see the AUTHORS file
-// for details. All rights reserved. Use of this source code is governed by a
-// BSD-style license that can be found in the LICENSE file.
-
-import 'dart:async';
-import 'dart:mirrors';
-
-import 'package:build/build.dart';
-import 'package:collection/collection.dart';
-import 'package:meta/meta.dart';
-import 'package:path/path.dart' as p;
-
-import '../asset_graph/graph.dart';
-import '../logging/build_log.dart';
-import '../package_graph/package_graph.dart';
-
-/// Functionality for detecting if the build script itself or any of its
-/// transitive imports have changed.
-abstract class BuildScriptUpdates {
-  /// Checks if the current running program has been updated, based on
-  /// [updatedIds].
-  bool hasBeenUpdated(Set<AssetId> updatedIds);
-
-  /// Creates a [BuildScriptUpdates] object, using [reader] to ensure that
-  /// the [assetGraph] is tracking digests for all transitive sources.
-  ///
-  /// If [disabled] is `true` then all checks are skipped and
-  /// [hasBeenUpdated] will always return `false`.
-  static Future<BuildScriptUpdates> create(
-    AssetReader reader,
-    PackageGraph packageGraph,
-    AssetGraph assetGraph, {
-    bool disabled = false,
-  }) async {
-    if (disabled) return _NoopBuildScriptUpdates();
-    return _MirrorBuildScriptUpdates.create(reader, packageGraph, assetGraph);
-  }
-}
-
-/// Uses mirrors to find all transitive imports of the current script.
-class _MirrorBuildScriptUpdates implements BuildScriptUpdates {
-  final Set<AssetId> _allSources;
-  final bool _supportsIncrementalRebuilds;
-
-  _MirrorBuildScriptUpdates._(
-    this._supportsIncrementalRebuilds,
-    this._allSources,
-  );
-
-  static Future<BuildScriptUpdates> create(
-    AssetReader reader,
-    PackageGraph packageGraph,
-    AssetGraph graph,
-  ) async {
-    var supportsIncrementalRebuilds = true;
-    Set<AssetId> allSources;
-    try {
-      allSources =
-          _urisForThisScript
-              .map((id) => idForUri(id, packageGraph))
-              .nonNulls
-              .toSet();
-      var missing = allSources.firstWhereOrNull((id) => !graph.contains(id));
-      if (missing != null) {
-        supportsIncrementalRebuilds = false;
-        buildLog.warning(
-          '$missing was not found in the asset graph, '
-          'incremental builds will not work. This probably means you '
-          'don\'t have your dependencies specified fully in your '
-          'pubspec.yaml.',
-        );
-      } else {
-        // Make sure we are tracking changes for all ids in [allSources].
-        for (var id in allSources) {
-          final node = graph.get(id)!;
-          if (node.digest == null) {
-            final digest = await reader.digest(id);
-            graph.updateNode(id, (nodeBuilder) {
-              nodeBuilder.digest = digest;
-            });
-          }
-        }
-      }
-    } on ArgumentError // ignore: avoid_catching_errors
-    catch (_) {
-      supportsIncrementalRebuilds = false;
-      allSources = <AssetId>{};
-    }
-    return _MirrorBuildScriptUpdates._(supportsIncrementalRebuilds, allSources);
-  }
-
-  static Iterable<Uri> get _urisForThisScript =>
-      currentMirrorSystem().libraries.keys;
-
-  /// Checks if the current running program has been updated, based on
-  /// [updatedIds].
-  @override
-  bool hasBeenUpdated(Set<AssetId> updatedIds) {
-    if (!_supportsIncrementalRebuilds) return true;
-    return updatedIds.intersection(_allSources).isNotEmpty;
-  }
-}
-
-/// Always returns false for [hasBeenUpdated], used when we want to skip
-/// the build script checks.
-class _NoopBuildScriptUpdates implements BuildScriptUpdates {
-  @override
-  bool hasBeenUpdated(void _) => false;
-}
-
-/// Attempts to return an [AssetId] for [uri].
-///
-/// Returns `null` if the uri should be ignored, or throws an [ArgumentError]
-/// if the [uri] is not recognized.
-@visibleForTesting
-AssetId? idForUri(Uri uri, PackageGraph packageGraph) {
-  switch (uri.scheme) {
-    case 'dart':
-      // TODO: check for sdk updates!
-      break;
-    case 'package':
-      var parts = uri.pathSegments;
-      return AssetId(
-        parts[0],
-        p.url.joinAll(['lib', ...parts.getRange(1, parts.length)]),
-      );
-    case 'file':
-      final package = packageGraph.asPackageConfig.packageOf(
-        Uri.file(p.canonicalize(uri.toFilePath())),
-      );
-      if (package == null) {
-        throw ArgumentError(
-          'The uri $uri could not be resolved to a package in the current '
-          'package graph. Do you have a dependency on the package '
-          'containing this uri?',
-        );
-      }
-      // The `AssetId` constructor normalizes this path to a URI style.
-      var relativePath = p.relative(
-        uri.toFilePath(),
-        from: package.root.toFilePath(),
-      );
-      return AssetId(package.name, relativePath);
-    case 'data':
-      // Test runner uses a `data` scheme, don't invalidate for those.
-      if (uri.path.contains('package:test')) break;
-      continue unsupported;
-    case 'http':
-      continue unsupported;
-    unsupported:
-    default:
-      throw ArgumentError(
-        'Unsupported uri scheme `${uri.scheme}` found for '
-        'library in build script.\n'
-        'This probably means you are running in an unsupported '
-        'context, such as in an isolate or via `dart run`.\n'
-        'Full uri was: $uri.',
-      );
-  }
-  return null;
-}
diff --git a/build_runner_core/lib/src/generate/build_definition.dart b/build_runner_core/lib/src/generate/build_definition.dart
index 021c22904..5a02ee3d1 100644
--- a/build_runner_core/lib/src/generate/build_definition.dart
+++ b/build_runner_core/lib/src/generate/build_definition.dart
@@ -14,7 +14,6 @@ import '../asset/writer.dart';
 import '../asset_graph/exceptions.dart';
 import '../asset_graph/graph.dart';
 import '../asset_graph/graph_loader.dart';
-import '../changes/build_script_updates.dart';
 import '../environment/build_environment.dart';
 import '../logging/build_log.dart';
 import '../util/constants.dart';
@@ -27,7 +26,6 @@ import 'options.dart';
 // not a build definition.
 class BuildDefinition {
   final AssetGraph assetGraph;
-  final BuildScriptUpdates? buildScriptUpdates;
 
   /// Whether this is a build starting from no previous state or outputs.
   final bool cleanBuild;
@@ -39,12 +37,7 @@ class BuildDefinition {
   /// the current build having an incompatible change.
   final Map<AssetId, ChangeType>? updates;
 
-  BuildDefinition._(
-    this.assetGraph,
-    this.buildScriptUpdates,
-    this.cleanBuild,
-    this.updates,
-  );
+  BuildDefinition._(this.assetGraph, this.cleanBuild, this.updates);
 
   static Future<BuildDefinition> prepareWorkspace(
     BuildEnvironment environment,
@@ -77,7 +70,6 @@ class _Loader {
     var cacheDirSources = await assetTracker.findCacheDirSources();
     var internalSources = await assetTracker.findInternalSources();
 
-    BuildScriptUpdates? buildScriptUpdates;
     Map<AssetId, ChangeType>? updates;
     var cleanBuild = true;
     if (assetGraph != null) {
@@ -90,17 +82,8 @@ class _Loader {
         cacheDirSources,
         internalSources,
       );
-      buildScriptUpdates = await BuildScriptUpdates.create(
-        _environment.reader,
-        _options.packageGraph,
-        assetGraph,
-        disabled: _options.skipBuildScriptCheck,
-      );
-
-      var buildScriptUpdated =
-          !_options.skipBuildScriptCheck &&
-          buildScriptUpdates.hasBeenUpdated(updates.keys.toSet());
-      if (buildScriptUpdated) {
+      // ignore_for_file: dead_code
+      if (false) {
         buildLog.fullBuildBecause(FullBuildReason.incompatibleScript);
         var deletedSourceOutputs = await assetGraph.deleteOutputs(
           _options.packageGraph,
@@ -115,7 +98,6 @@ class _Loader {
 
         inputSources.removeAll(deletedSourceOutputs);
         assetGraph = null;
-        buildScriptUpdates = null;
         updates = null;
         cleanBuild = true;
       }
@@ -137,13 +119,6 @@ class _Loader {
         buildLog.error(e.toString());
         throw const CannotBuildException();
       }
-      buildScriptUpdates = await BuildScriptUpdates.create(
-        _environment.reader,
-        _options.packageGraph,
-        assetGraph,
-        disabled: _options.skipBuildScriptCheck,
-      );
-
       conflictingOutputs =
           assetGraph.outputs
               .where((n) => n.package == _options.packageGraph.root.name)
@@ -171,12 +146,7 @@ class _Loader {
       await _initialBuildCleanup(conflictingOutputs, _environment.writer);
     }
 
-    return BuildDefinition._(
-      assetGraph,
-      buildScriptUpdates,
-      cleanBuild,
-      updates,
-    );
+    return BuildDefinition._(assetGraph, cleanBuild, updates);
   }
 
   /// Deletes the generated output directory.
diff --git a/build_runner_core/lib/src/generate/build_series.dart b/build_runner_core/lib/src/generate/build_series.dart
index 169240893..b63e31f7b 100644
--- a/build_runner_core/lib/src/generate/build_series.dart
+++ b/build_runner_core/lib/src/generate/build_series.dart
@@ -12,7 +12,6 @@ import 'package:watcher/watcher.dart';
 import '../asset/finalized_reader.dart';
 import '../asset/writer.dart';
 import '../asset_graph/graph.dart';
-import '../changes/build_script_updates.dart';
 import '../environment/build_environment.dart';
 import '../logging/build_log.dart';
 import '../package_graph/apply_builders.dart';
@@ -39,7 +38,6 @@ import 'options.dart';
 class BuildSeries {
   final BuildEnvironment environment;
   final AssetGraph assetGraph;
-  final BuildScriptUpdates? buildScriptUpdates;
   final BuildOptions options;
   final BuildPhases buildPhases;
 
@@ -66,7 +64,6 @@ class BuildSeries {
   BuildSeries._(
     this.environment,
     this.assetGraph,
-    this.buildScriptUpdates,
     this.options,
     this.buildPhases,
     this.finalizedReader,
@@ -173,7 +170,6 @@ class BuildSeries {
     var build = BuildSeries._(
       environment,
       buildDefinition.assetGraph,
-      buildDefinition.buildScriptUpdates,
       options,
       buildPhases,
       finalizedReader,
diff --git a/build_runner_core/test/changes/build_script_updates_test.dart b/build_runner_core/test/changes/build_script_updates_test.dart
deleted file mode 100644
index ecac172e0..000000000
--- a/build_runner_core/test/changes/build_script_updates_test.dart
+++ /dev/null
@@ -1,77 +0,0 @@
-// Copyright (c) 2023, the Dart project authors.  Please see the AUTHORS file
-// for details. All rights reserved. Use of this source code is governed by a
-// BSD-style license that can be found in the LICENSE file.
-
-import 'package:build/build.dart';
-import 'package:build_runner_core/src/changes/build_script_updates.dart';
-import 'package:build_runner_core/src/package_graph/package_graph.dart';
-import 'package:package_config/package_config_types.dart';
-import 'package:test/test.dart';
-
-void main() {
-  group('idForUri', () {
-    late final PackageGraph packageGraph;
-    setUpAll(() async {
-      final rootPackage = PackageNode(
-        'a',
-        '/a/',
-        DependencyType.path,
-        LanguageVersion(3, 0),
-        isRoot: true,
-      );
-      final dependency = PackageNode(
-        'b',
-        '/b/',
-        DependencyType.path,
-        LanguageVersion(3, 0),
-      );
-      rootPackage.dependencies.add(dependency);
-      packageGraph = PackageGraph.fromRoot(rootPackage);
-    });
-
-    test('dart: uris return null', () {
-      expect(idForUri(Uri.parse('dart:io'), packageGraph), isNull);
-    });
-
-    test('package: uris can be converted', () {
-      expect(
-        idForUri(Uri.parse('package:a/a.dart'), packageGraph),
-        AssetId('a', 'lib/a.dart'),
-      );
-    });
-
-    test('file: uris can be looked up', () {
-      expect(
-        idForUri(Uri.file('/a/lib/a.dart'), packageGraph),
-        AssetId('a', 'lib/a.dart'),
-      );
-      expect(
-        idForUri(Uri.file('/b/b.dart'), packageGraph),
-        AssetId('b', 'b.dart'),
-      );
-    });
-    test('data: arent supported unless they are from the test runner', () {
-      expect(
-        () => idForUri(
-          Uri.parse('data:text/plain;charset=UTF-8,foo'),
-          packageGraph,
-        ),
-        throwsA(isA<ArgumentError>()),
-      );
-      expect(
-        idForUri(
-          Uri.parse('data:text/plain;charset=UTF-8,package:test'),
-          packageGraph,
-        ),
-        null,
-      );
-    });
-
-    test('http: uris are not supported', () {
-      expect(
-        () => idForUri(Uri.parse('http://google.com'), packageGraph),
-        throwsA(isA<ArgumentError>()),
-      );
-    });
-  });
-}