diff --git a/pkgs/_analyzer_macros/lib/macro_implementation.dart b/pkgs/_analyzer_macros/lib/macro_implementation.dart
index 0594c47b..09b48b08 100644
--- a/pkgs/_analyzer_macros/lib/macro_implementation.dart
+++ b/pkgs/_analyzer_macros/lib/macro_implementation.dart
@@ -9,9 +9,9 @@ import 'package:analyzer/src/summary2/macro_declarations.dart' as analyzer;
 import 'package:analyzer/src/summary2/macro_injected_impl.dart' as injected;
 import 'package:dart_model/dart_model.dart';
 import 'package:macro_service/macro_service.dart';
-import 'package:macros/macros.dart';
+import 'package:macros/macros.dart' as macros_api_v1;
 // ignore: implementation_imports
-import 'package:macros/src/executor.dart' as injected;
+import 'package:macros/src/executor.dart' as macros_api_v1;
 
 import 'query_service.dart';
 
@@ -83,11 +83,12 @@ class AnalyzerRunningMacro implements injected.RunningMacro {
 
   @override
   Future<AnalyzerMacroExecutionResult> executeDeclarationsPhase(
-      MacroTarget target,
-      DeclarationPhaseIntrospector declarationsPhaseIntrospector) async {
+      macros_api_v1.MacroTarget target,
+      macros_api_v1.DeclarationPhaseIntrospector
+          declarationsPhaseIntrospector) async {
     // TODO(davidmorgan): this is a hack to access analyzer internals; remove.
     introspector = declarationsPhaseIntrospector;
-    return await AnalyzerMacroExecutionResult.expandTemplates(
+    return await AnalyzerMacroExecutionResult.dartModelToInjected(
         target,
         await _impl._host.augment(
             name, AugmentRequest(phase: 2, target: target.qualifiedName)));
@@ -95,11 +96,12 @@ class AnalyzerRunningMacro implements injected.RunningMacro {
 
   @override
   Future<AnalyzerMacroExecutionResult> executeDefinitionsPhase(
-      MacroTarget target,
-      DefinitionPhaseIntrospector definitionPhaseIntrospector) async {
+      macros_api_v1.MacroTarget target,
+      macros_api_v1.DefinitionPhaseIntrospector
+          definitionPhaseIntrospector) async {
     // TODO(davidmorgan): this is a hack to access analyzer internals; remove.
     introspector = definitionPhaseIntrospector;
-    return await AnalyzerMacroExecutionResult.expandTemplates(
+    return await AnalyzerMacroExecutionResult.dartModelToInjected(
         target,
         await _impl._host.augment(
             name, AugmentRequest(phase: 3, target: target.qualifiedName)));
@@ -107,63 +109,71 @@ class AnalyzerRunningMacro implements injected.RunningMacro {
 
   @override
   Future<AnalyzerMacroExecutionResult> executeTypesPhase(
-      MacroTarget target, TypePhaseIntrospector typePhaseIntrospector) async {
+      macros_api_v1.MacroTarget target,
+      macros_api_v1.TypePhaseIntrospector typePhaseIntrospector) async {
     // TODO(davidmorgan): this is a hack to access analyzer internals; remove.
     introspector = typePhaseIntrospector;
-    return await AnalyzerMacroExecutionResult.expandTemplates(
+    return await AnalyzerMacroExecutionResult.dartModelToInjected(
         target,
         await _impl._host.augment(
             name, AugmentRequest(phase: 1, target: target.qualifiedName)));
   }
 }
 
-/// Converts [AugmentResponse] to [injected.MacroExecutionResult].
+/// Converts [AugmentResponse] to [macros_api_v1.MacroExecutionResult].
 ///
 /// TODO(davidmorgan): add to `AugmentationResponse` to cover all the
 /// functionality of `MacroExecutionResult`.
-class AnalyzerMacroExecutionResult implements injected.MacroExecutionResult {
-  final MacroTarget target;
+class AnalyzerMacroExecutionResult
+    implements macros_api_v1.MacroExecutionResult {
+  final macros_api_v1.MacroTarget target;
   @override
-  final Map<Identifier, Iterable<DeclarationCode>> typeAugmentations;
+  final Map<macros_api_v1.Identifier, Iterable<macros_api_v1.DeclarationCode>>
+      typeAugmentations;
 
   AnalyzerMacroExecutionResult(
-      this.target, Iterable<DeclarationCode> declarations)
+      this.target, Iterable<macros_api_v1.DeclarationCode> declarations)
       // TODO(davidmorgan): this assumes augmentations are for the macro
       // application target. Instead, it should be explicit in
       // `AugmentResponse`.
-      : typeAugmentations = {(target as Declaration).identifier: declarations};
+      : typeAugmentations = {
+          (target as macros_api_v1.Declaration).identifier: declarations
+        };
 
-  static Future<AnalyzerMacroExecutionResult> expandTemplates(
-      MacroTarget target, AugmentResponse augmentResponse) async {
-    final declarations = <DeclarationCode>[];
+  static Future<AnalyzerMacroExecutionResult> dartModelToInjected(
+      macros_api_v1.MacroTarget target, AugmentResponse augmentResponse) async {
+    final declarations = <macros_api_v1.DeclarationCode>[];
     for (final augmentation in augmentResponse.augmentations) {
-      declarations.add(
-          DeclarationCode.fromParts(await _expandTemplates(augmentation.code)));
+      declarations.add(macros_api_v1.DeclarationCode.fromParts(
+          await _resolveNames(augmentation.code)));
     }
     return AnalyzerMacroExecutionResult(target, declarations);
   }
 
   @override
-  List<Diagnostic> get diagnostics => [];
+  List<macros_api_v1.Diagnostic> get diagnostics => [];
 
   @override
-  Map<Identifier, Iterable<DeclarationCode>> get enumValueAugmentations => {};
+  Map<macros_api_v1.Identifier, Iterable<macros_api_v1.DeclarationCode>>
+      get enumValueAugmentations => {};
 
   @override
-  MacroException? get exception => null;
+  macros_api_v1.MacroException? get exception => null;
 
   @override
-  Map<Identifier, NamedTypeAnnotationCode> get extendsTypeAugmentations => {};
+  Map<macros_api_v1.Identifier, macros_api_v1.NamedTypeAnnotationCode>
+      get extendsTypeAugmentations => {};
 
   @override
-  Map<Identifier, Iterable<TypeAnnotationCode>> get interfaceAugmentations =>
-      {};
+  Map<macros_api_v1.Identifier, Iterable<macros_api_v1.TypeAnnotationCode>>
+      get interfaceAugmentations => {};
 
   @override
-  Iterable<DeclarationCode> get libraryAugmentations => {};
+  Iterable<macros_api_v1.DeclarationCode> get libraryAugmentations => {};
 
   @override
-  Map<Identifier, Iterable<TypeAnnotationCode>> get mixinAugmentations => {};
+  Map<macros_api_v1.Identifier, Iterable<macros_api_v1.TypeAnnotationCode>>
+      get mixinAugmentations => {};
 
   @override
   Iterable<String> get newTypeNames => [];
@@ -172,46 +182,49 @@ class AnalyzerMacroExecutionResult implements injected.MacroExecutionResult {
   void serialize(Object serializer) => throw UnimplementedError();
 }
 
-extension MacroTargetExtension on MacroTarget {
+extension MacroTargetExtension on macros_api_v1.MacroTarget {
   QualifiedName get qualifiedName {
-    final element =
-        ((this as Declaration).identifier as analyzer.IdentifierImpl).element!;
+    final element = ((this as macros_api_v1.Declaration).identifier
+            as analyzer.IdentifierImpl)
+        .element!;
     return QualifiedName(
         uri: '${element.library!.definingCompilationUnit.source.uri}',
         name: element.displayName);
   }
 }
 
-/// Converts [code] to a mix of `Identifier` and `String`.
-///
-/// Looks up references of the form `{{uri#name}}` using `resolveIdentifier`.
-///
-/// TODO(davidmorgan): move to the client side.
-Future<List<Object>> _expandTemplates(String code) async {
-  final result = <Object>[];
-  var index = 0;
-  while (index < code.length) {
-    final start = code.indexOf('{{', index);
-    if (start == -1) {
-      result.add(code.substring(index));
-      break;
+/// Converts [codes] to a list of `String` and `Identifier`.
+Future<List<Object>> _resolveNames(List<Code> codes) async {
+  // Find the set of unique [QualifiedName]s used.
+  final qualifiedNameStrings = <String>{};
+  for (final code in codes) {
+    if (code.type == CodeType.qualifiedName) {
+      qualifiedNameStrings.add(code.asQualifiedName.asString);
     }
-    result.add(code.substring(index, start));
-    final end = code.indexOf('}}', start);
-    if (end == -1) {
-      throw ArgumentError('Unmatched opening brace: $code');
-    }
-    final name = code.substring(start + 2, end);
-    final parts = name.split('#');
-    if (parts.length != 2) {
-      throw ArgumentError('Expected "uri#name" in: $name');
-    }
-    final uri = Uri.parse(parts[0]);
-    final identifier = await (introspector as TypePhaseIntrospector)
+  }
+
+  // Create futures looking up their [Identifier]s, then `await` in parallel.
+  final qualifiedNamesList =
+      qualifiedNameStrings.map(QualifiedName.parse).toList();
+  final identifierFutures = <Future<macros_api_v1.Identifier>>[];
+  for (final qualifiedName in qualifiedNamesList) {
+    identifierFutures.add((introspector as macros_api_v1.TypePhaseIntrospector)
         // ignore: deprecated_member_use
-        .resolveIdentifier(uri, parts[1]);
-    result.add(identifier);
-    index = end + 2;
+        .resolveIdentifier(Uri.parse(qualifiedName.uri), qualifiedName.name));
+  }
+  final identifiers = await Future.wait(identifierFutures);
+
+  // Build the result using the looked up [Identifier]s.
+  final identifiersByQualifiedNameStrings =
+      Map.fromIterables(qualifiedNameStrings, identifiers);
+  final result = <Object>[];
+  for (final code in codes) {
+    if (code.type == CodeType.string) {
+      result.add(code.asString);
+    } else if (code.type == CodeType.qualifiedName) {
+      final qualifiedName = code.asQualifiedName;
+      result.add(identifiersByQualifiedNameStrings[qualifiedName.asString]!);
+    }
   }
   return result;
 }
diff --git a/pkgs/_cfe_macros/lib/macro_implementation.dart b/pkgs/_cfe_macros/lib/macro_implementation.dart
index f64a6dbc..746e494b 100644
--- a/pkgs/_cfe_macros/lib/macro_implementation.dart
+++ b/pkgs/_cfe_macros/lib/macro_implementation.dart
@@ -9,9 +9,9 @@ import 'package:front_end/src/kernel/macro/identifiers.dart' as cfe;
 // ignore: implementation_imports
 import 'package:front_end/src/macros/macro_injected_impl.dart' as injected;
 import 'package:macro_service/macro_service.dart';
-import 'package:macros/macros.dart';
+import 'package:macros/macros.dart' as macros_api_v1;
 // ignore: implementation_imports
-import 'package:macros/src/executor.dart' as injected;
+import 'package:macros/src/executor.dart' as macros_api_v1;
 
 import 'query_service.dart';
 
@@ -82,22 +82,26 @@ class CfeRunningMacro implements injected.RunningMacro {
   }
 
   @override
-  Future<CfeMacroExecutionResult> executeDeclarationsPhase(MacroTarget target,
-      DeclarationPhaseIntrospector declarationsPhaseIntrospector) async {
+  Future<CfeMacroExecutionResult> executeDeclarationsPhase(
+      macros_api_v1.MacroTarget target,
+      macros_api_v1.DeclarationPhaseIntrospector
+          declarationsPhaseIntrospector) async {
     // TODO(davidmorgan): this is a hack to access CFE internals; remove.
     introspector = declarationsPhaseIntrospector;
-    return CfeMacroExecutionResult(
+    return await CfeMacroExecutionResult.dartModelToInjected(
         target,
         await _impl._host.augment(
             name, AugmentRequest(phase: 2, target: target.qualifiedName)));
   }
 
   @override
-  Future<CfeMacroExecutionResult> executeDefinitionsPhase(MacroTarget target,
-      DefinitionPhaseIntrospector definitionPhaseIntrospector) async {
+  Future<CfeMacroExecutionResult> executeDefinitionsPhase(
+      macros_api_v1.MacroTarget target,
+      macros_api_v1.DefinitionPhaseIntrospector
+          definitionPhaseIntrospector) async {
     // TODO(davidmorgan): this is a hack to access CFE internals; remove.
     introspector = definitionPhaseIntrospector;
-    return CfeMacroExecutionResult(
+    return await CfeMacroExecutionResult.dartModelToInjected(
         target,
         await _impl._host.augment(
             name, AugmentRequest(phase: 3, target: target.qualifiedName)));
@@ -105,72 +109,123 @@ class CfeRunningMacro implements injected.RunningMacro {
 
   @override
   Future<CfeMacroExecutionResult> executeTypesPhase(
-      MacroTarget target, TypePhaseIntrospector typePhaseIntrospector) async {
+      macros_api_v1.MacroTarget target,
+      macros_api_v1.TypePhaseIntrospector typePhaseIntrospector) async {
     // TODO(davidmorgan): this is a hack to access CFE internals; remove.
     introspector = typePhaseIntrospector;
-    return CfeMacroExecutionResult(
+    return await CfeMacroExecutionResult.dartModelToInjected(
         target,
         await _impl._host.augment(
             name, AugmentRequest(phase: 1, target: target.qualifiedName)));
   }
 }
 
-/// Converts [AugmentResponse] to [injected.MacroExecutionResult].
+/// Converts [AugmentResponse] to [macros_api_v1.MacroExecutionResult].
 ///
 /// TODO(davidmorgan): add to `AugmentationResponse` to cover all the
 /// functionality of `MacroExecutionResult`.
-class CfeMacroExecutionResult implements injected.MacroExecutionResult {
-  final MacroTarget target;
-  final AugmentResponse augmentResponse;
-
-  CfeMacroExecutionResult(this.target, this.augmentResponse);
+class CfeMacroExecutionResult implements macros_api_v1.MacroExecutionResult {
+  final macros_api_v1.MacroTarget target;
+  @override
+  final Map<macros_api_v1.Identifier, Iterable<macros_api_v1.DeclarationCode>>
+      typeAugmentations;
+
+  CfeMacroExecutionResult(
+      this.target, Iterable<macros_api_v1.DeclarationCode> declarations)
+      // TODO(davidmorgan): this assumes augmentations are for the macro
+      // application target. Instead, it should be explicit in
+      // `AugmentResponse`.
+      : typeAugmentations = {
+          // TODO(davidmorgan): empty augmentations response breaks the test,
+          // it's not clear why.
+          if (declarations.isNotEmpty)
+            (target as macros_api_v1.Declaration).identifier: declarations
+        };
+
+  static Future<CfeMacroExecutionResult> dartModelToInjected(
+      macros_api_v1.MacroTarget target, AugmentResponse augmentResponse) async {
+    final declarations = <macros_api_v1.DeclarationCode>[];
+    for (final augmentation in augmentResponse.augmentations) {
+      declarations.add(macros_api_v1.DeclarationCode.fromParts(
+          await _resolveNames(augmentation.code)));
+    }
+    return CfeMacroExecutionResult(target, declarations);
+  }
 
   @override
-  List<Diagnostic> get diagnostics => [];
+  List<macros_api_v1.Diagnostic> get diagnostics => [];
 
   @override
-  Map<Identifier, Iterable<DeclarationCode>> get enumValueAugmentations => {};
+  Map<macros_api_v1.Identifier, Iterable<macros_api_v1.DeclarationCode>>
+      get enumValueAugmentations => {};
 
   @override
-  MacroException? get exception => null;
+  macros_api_v1.MacroException? get exception => null;
 
   @override
-  Map<Identifier, NamedTypeAnnotationCode> get extendsTypeAugmentations => {};
+  Map<macros_api_v1.Identifier, macros_api_v1.NamedTypeAnnotationCode>
+      get extendsTypeAugmentations => {};
 
   @override
-  Map<Identifier, Iterable<TypeAnnotationCode>> get interfaceAugmentations =>
-      {};
+  Map<macros_api_v1.Identifier, Iterable<macros_api_v1.TypeAnnotationCode>>
+      get interfaceAugmentations => {};
 
   @override
-  Iterable<DeclarationCode> get libraryAugmentations => {};
+  Iterable<macros_api_v1.DeclarationCode> get libraryAugmentations => {};
 
   @override
-  Map<Identifier, Iterable<TypeAnnotationCode>> get mixinAugmentations => {};
+  Map<macros_api_v1.Identifier, Iterable<macros_api_v1.TypeAnnotationCode>>
+      get mixinAugmentations => {};
 
   @override
   Iterable<String> get newTypeNames => [];
 
   @override
   void serialize(Object serializer) => throw UnimplementedError();
-
-  @override
-  Map<Identifier, Iterable<DeclarationCode>> get typeAugmentations => {
-        // TODO(davidmorgan): this assumes augmentations are for the macro
-        // application target. Instead, it should be explicit in
-        // `AugmentResponse`.
-        // TODO(davidmorgan): empty augmentations response breaks the test,
-        // it's not clear why.
-        if (augmentResponse.augmentations.isNotEmpty)
-          (target as Declaration).identifier: augmentResponse.augmentations
-              .map((a) => DeclarationCode.fromParts([a.code]))
-              .toList(),
-      };
 }
 
-extension MacroTargetExtension on MacroTarget {
+extension MacroTargetExtension on macros_api_v1.MacroTarget {
   QualifiedName get qualifiedName {
-    final identifier = ((this as Declaration).identifier as cfe.IdentifierImpl)
-        .resolveIdentifier();
+    final identifier =
+        ((this as macros_api_v1.Declaration).identifier as cfe.IdentifierImpl)
+            .resolveIdentifier();
     return QualifiedName(uri: '${identifier.uri}', name: identifier.name);
   }
 }
+
+/// Converts [codes] to a list of `String` and `Identifier`.
+// TODO(davidmorgan): share this code with `package:_analyzer_macros`.
+Future<List<Object>> _resolveNames(List<Code> codes) async {
+  // Find the set of unique [QualifiedName]s used.
+  final qualifiedNameStrings = <String>{};
+  for (final code in codes) {
+    if (code.type == CodeType.qualifiedName) {
+      qualifiedNameStrings.add(code.asQualifiedName.asString);
+    }
+  }
+
+  // Create futures looking up their [Identifier]s, then `await` in parallel.
+  final qualifiedNamesList =
+      qualifiedNameStrings.map(QualifiedName.parse).toList();
+  final identifierFutures = <Future<macros_api_v1.Identifier>>[];
+  for (final qualifiedName in qualifiedNamesList) {
+    identifierFutures.add((introspector as macros_api_v1.TypePhaseIntrospector)
+        // ignore: deprecated_member_use
+        .resolveIdentifier(Uri.parse(qualifiedName.uri), qualifiedName.name));
+  }
+  final identifiers = await Future.wait(identifierFutures);
+
+  // Build the result using the looked up [Identifier]s.
+  final identifiersByQualifiedNameStrings =
+      Map.fromIterables(qualifiedNameStrings, identifiers);
+  final result = <Object>[];
+  for (final code in codes) {
+    if (code.type == CodeType.string) {
+      result.add(code.asString);
+    } else if (code.type == CodeType.qualifiedName) {
+      final qualifiedName = code.asQualifiedName;
+      result.add(identifiersByQualifiedNameStrings[qualifiedName.asString]!);
+    }
+  }
+  return result;
+}
diff --git a/pkgs/_macro_client/test/macro_client_test.dart b/pkgs/_macro_client/test/macro_client_test.dart
index 2ad447b4..f27494e3 100644
--- a/pkgs/_macro_client/test/macro_client_test.dart
+++ b/pkgs/_macro_client/test/macro_client_test.dart
@@ -128,9 +128,16 @@ void main() {
           'type': 'AugmentResponse',
           'value': {
             'augmentations': [
-              {'code': 'int get x => 3;'}
+              {
+                'code': [
+                  {
+                    'type': 'String',
+                    'value': 'int get x => 3;',
+                  }
+                ]
+              }
             ]
-          }
+          },
         });
       });
 
@@ -205,10 +212,16 @@ void main() {
             'value': {
               'augmentations': [
                 {
-                  'code': '// {"uris":{"package:foo/foo.dart":{"scopes":{}}}}',
+                  'code': [
+                    {
+                      'type': 'String',
+                      'value':
+                          '// {"uris":{"package:foo/foo.dart":{"scopes":{}}}}'
+                    }
+                  ]
                 }
               ]
-            }
+            },
           },
         );
       });
@@ -276,10 +289,16 @@ void main() {
             'value': {
               'augmentations': [
                 {
-                  'code': '// {"uris":{"package:foo/foo1.dart":{"scopes":{}}}}',
+                  'code': [
+                    {
+                      'type': 'String',
+                      'value':
+                          '// {"uris":{"package:foo/foo1.dart":{"scopes":{}}}}'
+                    }
+                  ]
                 }
               ]
-            }
+            },
           },
         );
 
@@ -291,10 +310,16 @@ void main() {
             'value': {
               'augmentations': [
                 {
-                  'code': '// {"uris":{"package:foo/foo2.dart":{"scopes":{}}}}',
+                  'code': [
+                    {
+                      'type': 'String',
+                      'value':
+                          '// {"uris":{"package:foo/foo2.dart":{"scopes":{}}}}'
+                    }
+                  ]
                 }
               ]
-            }
+            },
           },
         );
       });
diff --git a/pkgs/_macro_host/test/macro_host_test.dart b/pkgs/_macro_host/test/macro_host_test.dart
index df30bdb8..ef5424a4 100644
--- a/pkgs/_macro_host/test/macro_host_test.dart
+++ b/pkgs/_macro_host/test/macro_host_test.dart
@@ -34,8 +34,9 @@ void main() {
 
         expect(
             await host.augment(macroAnnotation, AugmentRequest(phase: 2)),
-            Scope.macro.run(() => AugmentResponse(
-                augmentations: [Augmentation(code: 'int get x => 3;')])));
+            Scope.macro.run(() => AugmentResponse(augmentations: [
+                  Augmentation(code: [Code.string('int get x => 3;')])
+                ])));
       });
 
       test('hosts a macro, responds to queries', () async {
@@ -62,9 +63,10 @@ void main() {
                     target: QualifiedName(
                         uri: 'package:foo/foo.dart', name: 'Foo'))),
             Scope.macro.run(() => AugmentResponse(augmentations: [
-                  Augmentation(
-                      code:
-                          '// {"uris":{"package:foo/foo.dart":{"scopes":{}}}}')
+                  Augmentation(code: [
+                    Code.string(
+                        '// {"uris":{"package:foo/foo.dart":{"scopes":{}}}}')
+                  ])
                 ])));
       });
 
diff --git a/pkgs/_test_macros/lib/declare_x_macro.dart b/pkgs/_test_macros/lib/declare_x_macro.dart
index 83e19b14..ece158b3 100644
--- a/pkgs/_test_macros/lib/declare_x_macro.dart
+++ b/pkgs/_test_macros/lib/declare_x_macro.dart
@@ -6,6 +6,8 @@ import 'package:dart_model/dart_model.dart';
 import 'package:macro/macro.dart';
 import 'package:macro_service/macro_service.dart';
 
+import 'templating.dart';
+
 /// Adds a getter `int get x` to the class.
 class DeclareX {
   const DeclareX();
@@ -27,6 +29,6 @@ class DeclareXImplementation implements Macro {
 
     // TODO(davidmorgan): still need to pass through the augment target.
     return AugmentResponse(
-        augmentations: [Augmentation(code: 'int get x => 3;')]);
+        augmentations: [Augmentation(code: expandTemplate('int get x => 3;'))]);
   }
 }
diff --git a/pkgs/_test_macros/lib/json_codable.dart b/pkgs/_test_macros/lib/json_codable.dart
index 874f0bad..919ec1df 100644
--- a/pkgs/_test_macros/lib/json_codable.dart
+++ b/pkgs/_test_macros/lib/json_codable.dart
@@ -6,6 +6,8 @@ import 'package:dart_model/dart_model.dart';
 import 'package:macro/macro.dart';
 import 'package:macro_service/macro_service.dart';
 
+import 'templating.dart';
+
 /// A macro which adds a `fromJson(Map<String, Object?> json)` JSON decoding
 /// constructor to a class.
 class JsonCodable {
@@ -35,11 +37,11 @@ class JsonCodableImplementation implements Macro {
   Future<AugmentResponse> phase2(Host host, AugmentRequest request) async {
     final target = request.target;
     return AugmentResponse(augmentations: [
-      Augmentation(code: '''
+      Augmentation(code: expandTemplate('''
 // TODO(davidmorgan): see https://github.com/dart-lang/macros/issues/80.
 // external ${target.name}.fromJson($_jsonMapType json);
 // external $_jsonMapType toJson();
-   '''),
+   '''))
     ]);
   }
 
@@ -61,10 +63,10 @@ class JsonCodableImplementation implements Macro {
 
     // TODO(davidmorgan): helper for augmenting initializers.
     // See: https://github.com/dart-lang/sdk/blob/main/pkg/_macros/lib/src/executor/builder_impls.dart#L500
-    result.add(Augmentation(code: '''
+    result.add(Augmentation(code: expandTemplate('''
 augment ${target.name}.fromJson($_jsonMapType json) :
 ${initializers.join(',\n')};
-'''));
+''')));
 
     final serializers = <String>[];
     for (final field
@@ -80,13 +82,13 @@ ${initializers.join(',\n')};
 
     // TODO(davidmorgan): helper for augmenting methods.
     // See: https://github.com/dart-lang/sdk/blob/main/pkg/_macros/lib/src/executor/builder_impls.dart#L500
-    result.add(Augmentation(code: '''
+    result.add(Augmentation(code: expandTemplate('''
 augment $_jsonMapType toJson() {
   final json = $_jsonMapTypeForLiteral{};
 ${serializers.join('')}
   return json;
 }
-'''));
+''')));
 
     return AugmentResponse(augmentations: result);
   }
@@ -182,8 +184,3 @@ ${serializers.join('')}
     throw UnsupportedError('$type');
   }
 }
-
-// TODO(davidmorgan): figure out where this should go.
-extension TemplatingExtension on QualifiedName {
-  String get code => '{{$uri#$name}}';
-}
diff --git a/pkgs/_test_macros/lib/query_class.dart b/pkgs/_test_macros/lib/query_class.dart
index 246ef06f..6f652b2a 100644
--- a/pkgs/_test_macros/lib/query_class.dart
+++ b/pkgs/_test_macros/lib/query_class.dart
@@ -8,6 +8,8 @@ import 'package:dart_model/dart_model.dart';
 import 'package:macro/macro.dart';
 import 'package:macro_service/macro_service.dart';
 
+import 'templating.dart';
+
 /// Applies a macro which sends an empty query, and outputs an augmentation
 /// that is the query result as a comment.
 class QueryClass {
@@ -31,7 +33,8 @@ class QueryClassImplementation implements Macro {
     final model = await host.query(Query(
       target: request.target,
     ));
-    return AugmentResponse(
-        augmentations: [Augmentation(code: '// ${json.encode(model)}')]);
+    return AugmentResponse(augmentations: [
+      Augmentation(code: expandTemplate('// ${json.encode(model)}'))
+    ]);
   }
 }
diff --git a/pkgs/_test_macros/lib/templating.dart b/pkgs/_test_macros/lib/templating.dart
new file mode 100644
index 00000000..98f75608
--- /dev/null
+++ b/pkgs/_test_macros/lib/templating.dart
@@ -0,0 +1,42 @@
+// Copyright (c) 2024, the Dart project authors. Please see the AUTHORS file
+// for details. All rights reserved. Use of this source code is governed by a
+// BSD-style license that can be found in the LICENSE file.
+
+import 'package:dart_model/dart_model.dart';
+
+// TODO(davidmorgan): figure out where this should go.
+extension TemplatingExtension on QualifiedName {
+  String get code => '{{$uri#$name}}';
+}
+
+/// Converts [template] to a mix of `Identifier` and `String`.
+///
+/// References of the form `{{uri#name}}` become [QualifiedName] wrapped in
+/// [Code.qualifiedName], everything else becomes `String`.
+///
+/// TODO(davidmorgan): figure out where this should go.
+List<Code> expandTemplate(String template) {
+  final result = <Code>[];
+  var index = 0;
+  while (index < template.length) {
+    final start = template.indexOf('{{', index);
+    if (start == -1) {
+      result.add(Code.string(template.substring(index)));
+      break;
+    }
+    result.add(Code.string(template.substring(index, start)));
+    final end = template.indexOf('}}', start);
+    if (end == -1) {
+      throw ArgumentError('Unmatched opening brace: $template');
+    }
+    final name = template.substring(start + 2, end);
+    final parts = name.split('#');
+    if (parts.length != 2) {
+      throw ArgumentError('Expected "uri#name" in: $name');
+    }
+    result
+        .add(Code.qualifiedName(QualifiedName(uri: parts[0], name: parts[1])));
+    index = end + 2;
+  }
+  return result;
+}
diff --git a/pkgs/dart_model/lib/src/dart_model.g.dart b/pkgs/dart_model/lib/src/dart_model.g.dart
index 8a7b4f30..a23d2826 100644
--- a/pkgs/dart_model/lib/src/dart_model.g.dart
+++ b/pkgs/dart_model/lib/src/dart_model.g.dart
@@ -6,21 +6,72 @@ import 'package:dart_model/src/json_buffer/json_buffer_builder.dart';
 // ignore: implementation_imports,unused_import,prefer_relative_imports
 import 'package:dart_model/src/scopes.dart';
 
-/// An augmentation to Dart code. TODO(davidmorgan): this is a placeholder.
+/// An augmentation to Dart code.
 extension type Augmentation.fromJson(Map<String, Object?> node)
     implements Object {
   static final TypedMapSchema _schema = TypedMapSchema({
-    'code': Type.stringPointer,
+    'code': Type.closedListPointer,
   });
   Augmentation({
-    String? code,
+    List<Code>? code,
   }) : this.fromJson(Scope.createMap(
           _schema,
           code,
         ));
 
   /// Augmentation code.
-  String get code => node['code'] as String;
+  List<Code> get code => (node['code'] as List).cast();
+}
+
+enum CodeType {
+  // Private so switches must have a default. See `isKnown`.
+  _unknown,
+  qualifiedName,
+  string;
+
+  bool get isKnown => this != _unknown;
+}
+
+extension type Code.fromJson(Map<String, Object?> node) implements Object {
+  static final TypedMapSchema _schema = TypedMapSchema({
+    'type': Type.stringPointer,
+    'value': Type.anyPointer,
+  });
+  static Code qualifiedName(QualifiedName qualifiedName) =>
+      Code.fromJson(Scope.createMap(
+        _schema,
+        'QualifiedName',
+        qualifiedName,
+      ));
+  static Code string(String string) => Code.fromJson(Scope.createMap(
+        _schema,
+        'String',
+        string,
+      ));
+  CodeType get type {
+    switch (node['type'] as String) {
+      case 'QualifiedName':
+        return CodeType.qualifiedName;
+      case 'String':
+        return CodeType.string;
+      default:
+        return CodeType._unknown;
+    }
+  }
+
+  QualifiedName get asQualifiedName {
+    if (node['type'] != 'QualifiedName') {
+      throw StateError('Not a QualifiedName.');
+    }
+    return QualifiedName.fromJson(node['value'] as Map<String, Object?>);
+  }
+
+  String get asString {
+    if (node['type'] != 'String') {
+      throw StateError('Not a String.');
+    }
+    return node['value'] as String;
+  }
 }
 
 /// The type-hierarchy representation of the type `dynamic`.
diff --git a/schemas/dart_model.schema.json b/schemas/dart_model.schema.json
index 18e1e6fb..c941b56d 100644
--- a/schemas/dart_model.schema.json
+++ b/schemas/dart_model.schema.json
@@ -8,14 +8,40 @@
   "$defs": {
     "Augmentation": {
       "type": "object",
-      "description": "An augmentation to Dart code. TODO(davidmorgan): this is a placeholder.",
+      "description": "An augmentation to Dart code.",
       "properties": {
         "code": {
-          "type": "string",
-          "description": "Augmentation code."
+          "type": "array",
+          "description": "Augmentation code.",
+          "items": {
+            "$ref": "#/$defs/Code"
+          }
         }
       }
     },
+    "Code": {
+      "type": "object",
+      "description": "Code that is part of augmentations to Dart code.",
+      "properties": {
+        "type": {
+          "type": "string"
+        },
+        "value": {
+          "oneOf": [
+            {
+              "$ref": "#/$defs/QualifiedName"
+            },
+            {
+              "type": "string"
+            }
+          ]
+        },
+        "required": [
+          "type",
+          "value"
+        ]
+      }
+    },
     "DynamicTypeDesc": {
       "type": "null",
       "description": "The type-hierarchy representation of the type `dynamic`."
diff --git a/tool/dart_model_generator/lib/definitions.dart b/tool/dart_model_generator/lib/definitions.dart
index 90055fcd..b0ddb9f3 100644
--- a/tool/dart_model_generator/lib/definitions.dart
+++ b/tool/dart_model_generator/lib/definitions.dart
@@ -66,12 +66,19 @@ static Protocol handshakeProtocol = Protocol(
         Definition.clazz(
           'Augmentation',
           createInBuffer: true,
-          description: 'An augmentation to Dart code. '
-              'TODO(davidmorgan): this is a placeholder.',
+          description: 'An augmentation to Dart code.',
           properties: [
-            Property('code', type: 'String', description: 'Augmentation code.'),
+            Property('code',
+                type: 'List<Code>', description: 'Augmentation code.'),
           ],
         ),
+        Definition.union(
+          'Code',
+          createInBuffer: true,
+          description: 'Code that is part of augmentations to Dart code.',
+          types: ['QualifiedName', 'String'],
+          properties: [],
+        ),
         Definition.nullTypedef('DynamicTypeDesc',
             description:
                 'The type-hierarchy representation of the type `dynamic`.'),
diff --git a/tool/dart_model_generator/lib/generate_dart_model.dart b/tool/dart_model_generator/lib/generate_dart_model.dart
index d497ba39..1a7e0f32 100644
--- a/tool/dart_model_generator/lib/generate_dart_model.dart
+++ b/tool/dart_model_generator/lib/generate_dart_model.dart
@@ -647,11 +647,17 @@ class UnionTypeDefinition implements Definition {
       result
         ..writeln('$type get as$type {')
         ..writeln("if (node['type'] != '$type') "
-            "{ throw StateError('Not a $type.'); }")
-        ..writeln('return $type.fromJson'
+            "{ throw StateError('Not a $type.'); }");
+      // TODO(davidmorgan): this special case allows `String` to be in a union
+      // type, see if there is a nice way to generalize to other primitives.
+      if (type == 'String') {
+        result.writeln("return node['value'] as String;");
+      } else {
+        result.writeln('return $type.fromJson'
             "(node['value'] as "
-            '${context.lookupDefinition(type).representationTypeName});')
-        ..writeln('}');
+            '${context.lookupDefinition(type).representationTypeName});');
+      }
+      result.writeln('}');
     }
 
     for (final property in properties) {