diff --git a/pkg/analysis_server/lib/src/computer/computer_lazy_type_hierarchy.dart b/pkg/analysis_server/lib/src/computer/computer_lazy_type_hierarchy.dart
new file mode 100644
index 00000000000..d6eaea6ced9
--- /dev/null
+++ b/pkg/analysis_server/lib/src/computer/computer_lazy_type_hierarchy.dart
@@ -0,0 +1,173 @@
+// Copyright (c) 2022, 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:analysis_server/src/services/search/search_engine.dart';
+import 'package:analyzer/dart/analysis/results.dart';
+import 'package:analyzer/dart/ast/ast.dart';
+import 'package:analyzer/dart/element/element.dart';
+import 'package:analyzer/dart/element/type.dart';
+import 'package:analyzer/source/source_range.dart';
+import 'package:analyzer/src/dart/ast/utilities.dart';
+import 'package:analyzer/src/dart/element/element.dart';
+import 'package:collection/collection.dart';
+
+/// A lazy computer for Type Hierarchies.
+///
+/// Unlike [TypeHierarchyComputer], this class computes hierarchies lazily and
+/// roughly follow the LSP model, which is:
+///
+///   1. Client calls `findTarget(int offset)` to locate a starting point for
+///      navigation.
+///   2. Client passes the returned target into `findSubtypes()` or
+///      `findSupertypes()` to find it's immediate sub/super types. This can be
+///      repeated recursively.
+///
+/// It is expected that clients will call the methods above at different times
+/// (as the user expands items in a tree). It is up to the caller to handle
+/// cases where a target may no longer be valid (due to file modifications) that
+/// may result in inconsistent results.
+class DartLazyTypeHierarchyComputer {
+  final ResolvedUnitResult _result;
+
+  DartLazyTypeHierarchyComputer(this._result);
+
+  /// Finds subtypes for [target].
+  Future<List<TypeHierarchyItem>?> findSubtypes(
+    TypeHierarchyItem target,
+    SearchEngine searchEngine,
+  ) async {
+    final targetElement = _findTargetElement(target);
+    if (targetElement is! InterfaceElement) {
+      return null;
+    }
+
+    final subtypes = await _getSubtypes(targetElement, searchEngine);
+    return _convert(subtypes);
+  }
+
+  /// Finds supertypes for [target].
+  Future<List<TypeHierarchyItem>?> findSupertypes(
+    TypeHierarchyItem target,
+  ) async {
+    final targetElement = _findTargetElement(target);
+    if (targetElement == null) {
+      return null;
+    }
+
+    final supertypes = _getSupertypes(targetElement);
+    return _convert(supertypes);
+  }
+
+  /// Finds a target for starting type hierarchy navigation at [offset].
+  TypeHierarchyItem? findTarget(int offset) {
+    final node = NodeLocator2(offset).searchWithin(_result.unit);
+
+    Element? element;
+
+    // Try named types.
+    final type = node?.thisOrAncestorOfType<NamedType>();
+    element = type?.name.staticElement;
+
+    if (element == null) {
+      // Try enclosing class/mixins.
+      final Declaration? declaration = node
+          ?.thisOrAncestorMatching((node) => _isValidTargetDeclaration(node));
+      element = declaration?.declaredElement;
+    }
+
+    return element != null ? TypeHierarchyItem.forElement(element) : null;
+  }
+
+  List<TypeHierarchyItem> _convert(List<InterfaceType> types) =>
+      types.map((type) => TypeHierarchyItem.forElement(type.element)).toList();
+
+  Element? _findTargetElement(TypeHierarchyItem target) {
+    assert(target.file == _result.path);
+    // Locate the element by name instead of offset since this call my occur
+    // much later than the original find target request and it's possible the
+    // user has made changes since.
+    final targetElement = _result.unit.declarations
+        .where(_isValidTargetDeclaration)
+        .map((declaration) => declaration.declaredElement)
+        .firstWhereOrNull((element) => element?.name == target.displayName);
+    return targetElement;
+  }
+
+  /// Gets immediate sub types for the class/mixin [element].
+  Future<List<InterfaceType>> _getSubtypes(
+      InterfaceElement element, SearchEngine searchEngine) async {
+    var matches = await searchEngine.searchSubtypes(element);
+    return matches
+        .map((match) => (match.element as InterfaceElement).thisType)
+        .toList();
+  }
+
+  /// Gets immediate super types for the class/mixin [element].
+  ///
+  /// Includes all elements that contribute implementation to the type
+  /// such as supertypes and mixins, but not interfaces, constraints or
+  /// extended types.
+  List<InterfaceType> _getSupertypes(Element element) {
+    final supertype = element is InterfaceElement ? element.supertype : null;
+    final mixins =
+        element is InterfaceOrAugmentationElement ? element.mixins : null;
+    return [
+      if (supertype != null) supertype,
+      ...?mixins,
+    ];
+  }
+
+  /// Returns whether [declaration] is a valid target for type hierarchy
+  /// navigation.
+  bool _isValidTargetDeclaration(AstNode? declaration) =>
+      // TODO(dantup): Should we handle `ClassAugmentationDeclaration`s?
+      declaration is ClassDeclaration || declaration is MixinDeclaration;
+}
+
+/// An item that can appear in a Type Hierarchy.
+class TypeHierarchyItem {
+  /// The user-visible name for this item in the Type Hierarchy.
+  final String displayName;
+
+  /// The file that contains the declaration of this item.
+  final String file;
+
+  /// The range of the name at the declaration of this item.
+  final SourceRange nameRange;
+
+  /// The range of the code for the declaration of this item.
+  final SourceRange codeRange;
+
+  TypeHierarchyItem({
+    required this.displayName,
+    required this.file,
+    required this.nameRange,
+    required this.codeRange,
+  });
+
+  TypeHierarchyItem.forElement(Element element)
+      : displayName = element.displayName,
+        nameRange = _nameRangeForElement(element),
+        codeRange = _codeRangeForElement(element),
+        file = element.source!.fullName;
+
+  /// Returns the [SourceRange] of the code for [element].
+  static SourceRange _codeRangeForElement(Element element) {
+    // Non-synthetic elements should always have code locations.
+    final elementImpl = element.nonSynthetic as ElementImpl;
+    return SourceRange(elementImpl.codeOffset!, elementImpl.codeLength!);
+  }
+
+  /// Returns the [SourceRange] of the name for [element].
+  static SourceRange _nameRangeForElement(Element element) {
+    element = element.nonSynthetic;
+
+    // Some non-synthetic items can still have invalid nameOffsets (for example
+    // a compilation unit). This should never happen here, but guard against it.
+    assert(element.nameOffset != -1);
+    return element.nameOffset == -1
+        ? SourceRange(0, 0)
+        : SourceRange(element.nameOffset, element.nameLength);
+  }
+}
diff --git a/pkg/analysis_server/test/src/computer/test_all.dart b/pkg/analysis_server/test/src/computer/test_all.dart
index 65087cc9665..c9d19921f6f 100644
--- a/pkg/analysis_server/test/src/computer/test_all.dart
+++ b/pkg/analysis_server/test/src/computer/test_all.dart
@@ -13,6 +13,7 @@ import 'import_elements_computer_test.dart' as import_elements_computer;
 import 'imported_elements_computer_test.dart' as imported_elements_computer;
 import 'outline_computer_test.dart' as outline_computer;
 import 'selection_range_computer_test.dart' as selection_range;
+import 'type_hierarchy_computer_test.dart' as type_hierarchy_computer_test;
 
 void main() {
   defineReflectiveSuite(() {
@@ -25,5 +26,6 @@ void main() {
     imported_elements_computer.main();
     outline_computer.main();
     selection_range.main();
+    type_hierarchy_computer_test.main();
   });
 }
diff --git a/pkg/analysis_server/test/src/computer/type_hierarchy_computer_test.dart b/pkg/analysis_server/test/src/computer/type_hierarchy_computer_test.dart
new file mode 100644
index 00000000000..e7dbc1427ca
--- /dev/null
+++ b/pkg/analysis_server/test/src/computer/type_hierarchy_computer_test.dart
@@ -0,0 +1,383 @@
+// Copyright (c) 2022, 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:analysis_server/src/computer/computer_lazy_type_hierarchy.dart';
+import 'package:analysis_server/src/services/search/search_engine.dart';
+import 'package:analysis_server/src/services/search/search_engine_internal.dart';
+import 'package:analyzer/dart/analysis/results.dart';
+import 'package:analyzer/source/source_range.dart';
+import 'package:test/test.dart';
+import 'package:test_reflective_loader/test_reflective_loader.dart';
+
+import '../../abstract_single_unit.dart';
+import '../../utils/test_code_format.dart';
+
+void main() {
+  defineReflectiveSuite(() {
+    defineReflectiveTests(TypeHierarchyComputerFindTargetTest);
+    defineReflectiveTests(TypeHierarchyComputerFindSupertypesTest);
+    defineReflectiveTests(TypeHierarchyComputerFindSubtypesTest);
+  });
+}
+
+abstract class AbstractTypeHierarchyTest extends AbstractSingleUnitTest {
+  final startOfFile = SourceRange(0, 0);
+  late TestCode code;
+
+  /// Matches a [TypeHierarchyItem] for [Object].
+  Matcher get _isObject => TypeMatcher<TypeHierarchyItem>()
+      .having((e) => e.displayName, 'displayName', 'Object')
+      // Check some basic things without hard-coding values that will make
+      // this test brittle.
+      .having((e) => e.file, 'file', convertPath('/sdk/lib/core/core.dart'))
+      .having((e) => e.nameRange.offset, 'nameRange.offset', isPositive)
+      .having((e) => e.nameRange.length, 'nameRange.length', 'Object'.length)
+      .having((e) => e.codeRange.offset, 'codeRange.offset', isPositive)
+      .having((e) => e.codeRange.length, 'codeRange.length',
+          greaterThan('class Object {}'.length));
+
+  @override
+  void addTestSource(String content) {
+    code = TestCode.parse(content);
+    super.addTestSource(code.code);
+  }
+
+  Future<TypeHierarchyItem?> findTarget() async {
+    expect(code, isNotNull, reason: 'addTestSource should be called first');
+    final result = await getResolvedUnit(testFile);
+    return DartLazyTypeHierarchyComputer(result)
+        .findTarget(code.position.offset);
+  }
+
+  Future<ResolvedUnitResult> getResolvedUnit(String file) async =>
+      await (await session).getResolvedUnit(file) as ResolvedUnitResult;
+
+  /// Matches a [TypeHierarchyItem] with the given name/kind/file.
+  Matcher _isItem(
+    String displayName,
+    String file, {
+    required SourceRange nameRange,
+    required SourceRange codeRange,
+  }) =>
+      TypeMatcher<TypeHierarchyItem>()
+          .having((e) => e.displayName, 'displayName', displayName)
+          .having((e) => e.file, 'file', file)
+          .having((e) => e.nameRange, 'nameRange', nameRange)
+          .having((e) => e.codeRange, 'codeRange', codeRange);
+}
+
+@reflectiveTest
+class TypeHierarchyComputerFindSubtypesTest extends AbstractTypeHierarchyTest {
+  late SearchEngine searchEngine;
+
+  Future<List<TypeHierarchyItem>?> findSubtypes(
+      TypeHierarchyItem target) async {
+    final result = await getResolvedUnit(target.file);
+    return DartLazyTypeHierarchyComputer(result)
+        .findSubtypes(target, searchEngine);
+  }
+
+  @override
+  void setUp() {
+    super.setUp();
+    searchEngine = SearchEngineImpl([
+      driverFor(testPackageRootPath),
+    ]);
+  }
+
+  Future<void> test_class_mixins() async {
+    final content = '''
+/*[0*/class /*[1*/MyClass1/*1]*/ with MyMixin1 {}/*0]*/
+/*[2*/class /*[3*/MyClass2/*3]*/ with MyMixin1 {}/*2]*/
+mixin MyMi^xin1 {}
+    ''';
+
+    addTestSource(content);
+    final target = await findTarget();
+    final subtypes = await findSubtypes(target!);
+    expect(subtypes, [
+      _isItem(
+        'MyClass1',
+        testFile,
+        codeRange: code.ranges[0].sourceRange,
+        nameRange: code.ranges[1].sourceRange,
+      ),
+      _isItem(
+        'MyClass2',
+        testFile,
+        codeRange: code.ranges[2].sourceRange,
+        nameRange: code.ranges[3].sourceRange,
+      ),
+    ]);
+  }
+
+  Future<void> test_class_superclass() async {
+    final content = '''
+class ^MyClass1 {}
+/*[0*/class /*[1*/MyClass2/*1]*/ extends MyClass1 {}/*0]*/
+    ''';
+
+    addTestSource(content);
+    final target = await findTarget();
+    final supertypes = await findSubtypes(target!);
+    expect(supertypes, [
+      _isItem(
+        'MyClass2',
+        testFile,
+        codeRange: code.ranges[0].sourceRange,
+        nameRange: code.ranges[1].sourceRange,
+      ),
+    ]);
+  }
+
+  Future<void> test_mixin() async {
+    final content = '''
+class MyCl^ass1 {}
+/*[0*/mixin /*[1*/MyMixin1/*1]*/ on MyClass1 {}/*0]*/
+    ''';
+
+    addTestSource(content);
+    final target = await findTarget();
+    final supertypes = await findSubtypes(target!);
+    expect(supertypes, [
+      _isItem(
+        'MyMixin1',
+        testFile,
+        codeRange: code.ranges[0].sourceRange,
+        nameRange: code.ranges[1].sourceRange,
+      ),
+    ]);
+  }
+}
+
+@reflectiveTest
+class TypeHierarchyComputerFindSupertypesTest
+    extends AbstractTypeHierarchyTest {
+  Future<List<TypeHierarchyItem>?> findSupertypes(
+      TypeHierarchyItem target) async {
+    final result = await getResolvedUnit(target.file);
+    return DartLazyTypeHierarchyComputer(result).findSupertypes(target);
+  }
+
+  /// Test that if the file is modified between fetching a target and it's
+  /// sub/supertypes it can still be located (by name).
+  Future<void> test_class_afterModification() async {
+    final content = '''
+/*[0*/class /*[1*/MyClass1/*1]*/ {}/*0]*/
+class ^MyClass2 extends MyClass1 {}
+    ''';
+
+    addTestSource(content);
+    final target = await findTarget();
+
+    // Update the content so that offsets have changed since we got `target`.
+    addTestSource('// extra\n$content');
+
+    final supertypes = await findSupertypes(target!);
+    expect(supertypes, [
+      _isItem(
+        'MyClass1',
+        testFile,
+        codeRange: code.ranges[0].sourceRange,
+        nameRange: code.ranges[1].sourceRange,
+      ),
+    ]);
+  }
+
+  Future<void> test_class_mixins() async {
+    final content = '''
+/*[0*/mixin /*[1*/MyMixin1/*1]*/ {}/*0]*/
+/*[2*/mixin /*[3*/MyMixin2/*3]*/ {}/*2]*/
+class ^MyClass1 with MyMixin1, MyMixin2 {}
+    ''';
+
+    addTestSource(content);
+    final target = await findTarget();
+    final supertypes = await findSupertypes(target!);
+    expect(supertypes, [
+      _isObject,
+      _isItem(
+        'MyMixin1',
+        testFile,
+        codeRange: code.ranges[0].sourceRange,
+        nameRange: code.ranges[1].sourceRange,
+      ),
+      _isItem(
+        'MyMixin2',
+        testFile,
+        codeRange: code.ranges[2].sourceRange,
+        nameRange: code.ranges[3].sourceRange,
+      ),
+    ]);
+  }
+
+  Future<void> test_class_superclass() async {
+    final content = '''
+/*[0*/class /*[1*/MyClass1/*1]*/ {}/*0]*/
+class ^MyClass2 extends MyClass1 {}
+    ''';
+
+    addTestSource(content);
+    final target = await findTarget();
+    final supertypes = await findSupertypes(target!);
+    expect(supertypes, [
+      _isItem(
+        'MyClass1',
+        testFile,
+        codeRange: code.ranges[0].sourceRange,
+        nameRange: code.ranges[1].sourceRange,
+      ),
+    ]);
+  }
+
+  /// Mixins have no supertypes and are provided only for subtype search,
+  /// mirroring that they appear in the supertypes list of classes.
+  Future<void> test_mixin() async {
+    final content = '''
+class MyClass1 {}
+mixin MyMix^in2 on MyClass1 {}
+    ''';
+
+    addTestSource(content);
+    final target = await findTarget();
+    final supertypes = await findSupertypes(target!);
+    expect(supertypes, isEmpty);
+  }
+}
+
+@reflectiveTest
+class TypeHierarchyComputerFindTargetTest extends AbstractTypeHierarchyTest {
+  Future<void> expectNoTarget() async {
+    await expectTarget(isNull);
+  }
+
+  Future<void> expectTarget(Matcher matcher) async {
+    final target = await findTarget();
+    expect(target, matcher);
+  }
+
+  Future<void> test_class_body() async {
+    final content = '''
+/*[0*/class /*[1*/MyClass1/*1]*/ {
+  int? a^;
+}/*0]*/
+    ''';
+
+    addTestSource(content);
+    await expectTarget(
+      _isItem(
+        'MyClass1',
+        testFile,
+        codeRange: code.ranges[0].sourceRange,
+        nameRange: code.ranges[1].sourceRange,
+      ),
+    );
+  }
+
+  Future<void> test_class_keyword() async {
+    final content = '''
+/*[0*/cla^ss /*[1*/MyClass1/*1]*/ {
+}/*0]*/
+    ''';
+
+    addTestSource(content);
+    await expectTarget(
+      _isItem(
+        'MyClass1',
+        testFile,
+        codeRange: code.ranges[0].sourceRange,
+        nameRange: code.ranges[1].sourceRange,
+      ),
+    );
+  }
+
+  Future<void> test_class_name() async {
+    final content = '''
+/*[0*/class /*[1*/MyCla^ss1/*1]*/ {
+}/*0]*/
+    ''';
+
+    addTestSource(content);
+    await expectTarget(
+      _isItem(
+        'MyClass1',
+        testFile,
+        codeRange: code.ranges[0].sourceRange,
+        nameRange: code.ranges[1].sourceRange,
+      ),
+    );
+  }
+
+  Future<void> test_invalid_topLevel_nonClass() async {
+    final content = '''
+int? a^;
+''';
+
+    addTestSource(content);
+    await expectNoTarget();
+  }
+
+  Future<void> test_invalid_topLevel_whitespace() async {
+    final content = '''
+int? a;
+^
+int? b;
+''';
+
+    addTestSource(content);
+    await expectNoTarget();
+  }
+
+  Future<void> test_mixin_body() async {
+    final content = '''
+/*[0*/mixin /*[1*/MyMixin1/*1]*/ {
+  ^
+}/*0]*/
+    ''';
+
+    addTestSource(content);
+    await expectTarget(
+      _isItem(
+        'MyMixin1',
+        testFile,
+        codeRange: code.ranges[0].sourceRange,
+        nameRange: code.ranges[1].sourceRange,
+      ),
+    );
+  }
+
+  Future<void> test_mixin_keyword() async {
+    final content = '''
+/*[0*/mi^xin /*[1*/MyMixin1/*1]*/ {
+}/*0]*/
+    ''';
+
+    addTestSource(content);
+    await expectTarget(
+      _isItem(
+        'MyMixin1',
+        testFile,
+        codeRange: code.ranges[0].sourceRange,
+        nameRange: code.ranges[1].sourceRange,
+      ),
+    );
+  }
+
+  Future<void> test_mixinName() async {
+    final content = '''
+/*[0*/mixin /*[1*/MyMix^in1/*1]*/ {
+}/*0]*/
+    ''';
+
+    addTestSource(content);
+    await expectTarget(
+      _isItem(
+        'MyMixin1',
+        testFile,
+        codeRange: code.ranges[0].sourceRange,
+        nameRange: code.ranges[1].sourceRange,
+      ),
+    );
+  }
+}