diff --git a/app_dart/.vscode/settings.json b/app_dart/.vscode/settings.json
new file mode 100644
index 000000000..6ea5cb24a
--- /dev/null
+++ b/app_dart/.vscode/settings.json
@@ -0,0 +1,3 @@
+{
+    "dart.lineLength": 120
+}
\ No newline at end of file
diff --git a/app_dart/bin/gae_server.dart b/app_dart/bin/gae_server.dart
index f4ff63bb5..5a8b4a606 100644
--- a/app_dart/bin/gae_server.dart
+++ b/app_dart/bin/gae_server.dart
@@ -39,12 +39,15 @@ Future<void> main() async {
     // Gerrit service class to communicate with GoB.
     final GerritService gerritService = GerritService(config: config);
 
+    final fusionTester = FusionTester();
+
     /// Cocoon scheduler service to manage validating commits in presubmit and postsubmit.
     final Scheduler scheduler = Scheduler(
       cache: cache,
       config: config,
       githubChecksService: githubChecksService,
       luciBuildService: luciBuildService,
+      fusionTester: fusionTester,
     );
 
     final BranchService branchService = BranchService(
diff --git a/app_dart/bin/local_server.dart b/app_dart/bin/local_server.dart
index 3fe049bc0..381c9284a 100644
--- a/app_dart/bin/local_server.dart
+++ b/app_dart/bin/local_server.dart
@@ -46,12 +46,15 @@ Future<void> main() async {
   // Gerrit service class to communicate with GoB.
   final GerritService gerritService = GerritService(config: config);
 
+  final fusionTester = FusionTester();
+
   /// Cocoon scheduler service to manage validating commits in presubmit and postsubmit.
   final Scheduler scheduler = Scheduler(
     cache: cache,
     config: config,
     githubChecksService: githubChecksService,
     luciBuildService: luciBuildService,
+    fusionTester: fusionTester,
   );
 
   final BranchService branchService = BranchService(
diff --git a/app_dart/bin/validate_scheduler_config.dart b/app_dart/bin/validate_scheduler_config.dart
index 3b3fb1168..8a3442035 100644
--- a/app_dart/bin/validate_scheduler_config.dart
+++ b/app_dart/bin/validate_scheduler_config.dart
@@ -25,6 +25,7 @@ void main(List<String> args) async {
   final pb.SchedulerConfig unCheckedSchedulerConfig = pb.SchedulerConfig()..mergeFromProto3Json(configYaml);
   print(
     CiYaml(
+      type: CiType.any,
       slug: Config.flutterSlug,
       branch: Config.defaultBranch(Config.flutterSlug),
       config: unCheckedSchedulerConfig,
diff --git a/app_dart/integration_test/validate_all_ci_configs_test.dart b/app_dart/integration_test/validate_all_ci_configs_test.dart
index a5f79d683..d20208246 100644
--- a/app_dart/integration_test/validate_all_ci_configs_test.dart
+++ b/app_dart/integration_test/validate_all_ci_configs_test.dart
@@ -37,6 +37,7 @@ Future<void> main() async {
       final pb.SchedulerConfig currentSchedulerConfig = pb.SchedulerConfig()..mergeFromProto3Json(configYaml);
       try {
         CiYaml(
+          type: CiType.any,
           slug: config.slug,
           branch: Config.defaultBranch(config.slug),
           config: currentSchedulerConfig,
@@ -59,6 +60,7 @@ Future<void> main() async {
         final pb.SchedulerConfig schedulerConfig = pb.SchedulerConfig()..mergeFromProto3Json(configYaml);
         // Validate using the existing CiYaml logic.
         CiYaml(
+          type: CiType.any,
           slug: config.slug,
           branch: config.branch,
           config: schedulerConfig,
diff --git a/app_dart/lib/server.dart b/app_dart/lib/server.dart
index af3f52010..003626931 100644
--- a/app_dart/lib/server.dart
+++ b/app_dart/lib/server.dart
@@ -23,7 +23,9 @@ Server createServer({
   required CommitService commitService,
   required GerritService gerritService,
   required Scheduler scheduler,
+  FusionTester? fusionTester,
 }) {
+  fusionTester ??= FusionTester();
   final Map<String, RequestHandler<dynamic>> handlers = <String, RequestHandler<dynamic>>{
     '/api/check_flaky_builders': CheckFlakyBuilders(
       config: config,
@@ -67,7 +69,7 @@ Server createServer({
       gerritService: gerritService,
       scheduler: scheduler,
       commitService: commitService,
-      fusionTester: FusionTester(),
+      fusionTester: fusionTester,
     ),
     '/api/v2/presubmit-luci-subscription': PresubmitLuciSubscription(
       cache: cache,
diff --git a/app_dart/lib/src/foundation/utils.dart b/app_dart/lib/src/foundation/utils.dart
index 454da30e5..543295fff 100644
--- a/app_dart/lib/src/foundation/utils.dart
+++ b/app_dart/lib/src/foundation/utils.dart
@@ -22,6 +22,7 @@ import '../request_handling/exceptions.dart';
 import '../service/logging.dart';
 
 const String kCiYamlPath = '.ci.yaml';
+const String kCiYamlFusionEnginePath = 'engine/src/flutter/$kCiYamlPath';
 const String kTestOwnerPath = 'TESTOWNERS';
 
 /// Signature for a function that calculates the backoff duration to wait in
@@ -293,13 +294,13 @@ List<String> validateOwnership(
   final YamlMap? ciYaml = loadYaml(ciYamlContent) as YamlMap?;
   final pb.SchedulerConfig unCheckedSchedulerConfig = pb.SchedulerConfig()..mergeFromProto3Json(ciYaml);
 
-  final CiYaml ciYamlFromProto = CiYaml(
+  final CiYamlSet ciYamlFromProto = CiYamlSet(
     slug: Config.flutterSlug,
     branch: Config.defaultBranch(Config.flutterSlug),
-    config: unCheckedSchedulerConfig,
+    yamls: {CiType.any: unCheckedSchedulerConfig},
   );
 
-  final pb.SchedulerConfig schedulerConfig = ciYamlFromProto.config;
+  final pb.SchedulerConfig schedulerConfig = ciYamlFromProto.configFor(CiType.any);
 
   for (pb.Target target in schedulerConfig.targets) {
     final String builder = target.name;
diff --git a/app_dart/lib/src/model/ci_yaml/ci_yaml.dart b/app_dart/lib/src/model/ci_yaml/ci_yaml.dart
index b5f671094..ce1d95ae9 100644
--- a/app_dart/lib/src/model/ci_yaml/ci_yaml.dart
+++ b/app_dart/lib/src/model/ci_yaml/ci_yaml.dart
@@ -11,19 +11,136 @@ import 'package:github/github.dart';
 import '../proto/internal/scheduler.pb.dart' as pb;
 import 'target.dart';
 
+/// Key used for selecting which .ci.yaml to use
+enum CiType {
+  /// "Default" associated with this slug / ci.yaml
+  ///
+  /// Pre-fusion: engine, framework, etc
+  /// Post-fusion: framework, etc
+  ///
+  /// NOTE: Required to be present
+  any,
+
+  /// Engine's .ci.yaml file located in the monorepo
+  fusionEngine,
+}
+
+/// Wrapper around one or more [CiYamlSet] files contained in a single repository.
+///
+/// Single sourced repositories will have exactly one `.ci.yaml` file at the
+/// root of the tree. This will have the type [CiType.any].
+///
+/// Merged repositories can have multiple `.ci.yaml` files located throughout
+/// the tree. Today we only support the root type as [CiType.any] and the second
+/// as [CiType.fusionEngine].
+class CiYamlSet {
+  CiYamlSet({
+    required this.slug,
+    required this.branch,
+    required Map<CiType, pb.SchedulerConfig> yamls,
+    CiYamlSet? totConfig,
+    bool validate = false,
+    this.isFusion = false,
+  }) {
+    for (final MapEntry(key: type, value: config) in yamls.entries) {
+      configs[type] = CiYaml(
+        slug: slug,
+        branch: branch,
+        config: config,
+        type: type,
+        validate: validate,
+        isFusion: isFusion,
+        totConfig: totConfig?.configs[type],
+      );
+    }
+  }
+
+  final bool isFusion;
+
+  final configs = <CiType, CiYaml>{};
+
+  /// Get's the [pb.SchedulerConfig] for the requested [type].
+  ///
+  /// The type is expected to exist and will fail otherwise.
+  pb.SchedulerConfig configFor(CiType type) => configs[type]!.config;
+
+  /// Get's the [CiYaml] for the requested [type].
+  ///
+  /// The type is expected to exist and will fail otherwise.
+  CiYaml ciYamlFor(CiType type) => configs[type]!;
+
+  /// The [RepositorySlug] that [config] is from.
+  final RepositorySlug slug;
+
+  /// The git branch currently being scheduled against.
+  final String branch;
+
+  /// Gets all [Target] that run on presubmit for this config.
+  List<Target> presubmitTargets({CiType type = CiType.any}) => configs[type]!.presubmitTargets;
+
+  /// Gets all [Target] that run on postsubmit for this config.
+  List<Target> postsubmitTargets({CiType type = CiType.any}) => configs[type]!.postsubmitTargets;
+
+  /// Gets the first [Target] matching [builderName] or null.
+  Target? getFirstPostsubmitTarget(
+    String builderName, {
+    CiType type = CiType.any,
+  }) =>
+      configs[type]!.getFirstPostsubmitTarget(builderName);
+
+  /// List of target names used to filter target from release candidate branches
+  /// that were already removed from main.
+  List<String>? totTargetNames({CiType type = CiType.any}) => configs[type]!.totTargetNames;
+
+  /// List of postsubmit target names used to filter target from release candidate branches
+  /// that were already removed from main.
+  List<String>? totPostsubmitTargetNames({CiType type = CiType.any}) => configs[type]!.totPostsubmitTargetNames;
+
+  /// Filters post submit targets to remove targets we do not want backfilled.
+  List<Target> backfillTargets({CiType type = CiType.any}) => configs[type]!.backfillTargets;
+
+  /// Filters targets that were removed from main. [slug] is the gihub
+  /// slug for branch under test, [targets] is the list of targets from
+  /// the branch under test and [totTargetNames] is the list of target
+  /// names enabled on the default branch.
+  List<Target> filterOutdatedTargets(
+    slug,
+    targets,
+    totTargetNames, {
+    CiType type = CiType.any,
+  }) =>
+      configs[type]!.filterOutdatedTargets(slug, targets, totTargetNames);
+
+  /// Filters [targets] to those that should be started immediately.
+  ///
+  /// Targets with a dependency are triggered when there dependency pushes a notification that it has finished.
+  /// This shouldn't be confused for targets that have the property named dependency, which is used by the
+  /// flutter_deps recipe module on LUCI.
+  List<Target> getInitialTargets(
+    List<Target> targets, {
+    CiType type = CiType.any,
+  }) =>
+      configs[type]!.getInitialTargets(targets);
+
+  /// Get an unfiltered list of all [targets] that are found in the ci.yaml file.
+  List<Target> targets({CiType type = CiType.any}) => configs[type]!.targets;
+}
+
 /// This is a wrapper class around S[pb.SchedulerConfig].
 ///
 /// See //CI_YAML.md for high level documentation.
 class CiYaml {
-  /// Creates [CiYaml] from a [RepositorySlug], [branch], [pb.SchedulerConfig] and an optional [CiYaml] of tip of tree CiYaml.
+  /// Creates [CiYamlSet] from a [RepositorySlug], [branch], [pb.SchedulerConfig] and an optional [CiYamlSet] of tip of tree CiYaml.
   ///
   /// If [totConfig] is passed, the validation will verify no new targets have been added that may temporarily break the LUCI infrastructure (such as new prod or presubmit targets).
   CiYaml({
     required this.slug,
     required this.branch,
     required this.config,
+    required this.type,
     CiYaml? totConfig,
     bool validate = false,
+    this.isFusion = false,
   }) {
     if (validate) {
       _validate(config, branch, totSchedulerConfig: totConfig?.config);
@@ -37,6 +154,10 @@ class CiYaml {
         totConfig?.postsubmitTargets.map((Target target) => target.value.name).toList() ?? <String>[];
   }
 
+  final CiType type;
+
+  final bool isFusion;
+
   /// List of target names used to filter target from release candidate branches
   /// that were already removed from main.
   List<String>? totTargetNames;
@@ -196,7 +317,7 @@ class CiYaml {
     return regexp.hasMatch(branch);
   }
 
-  /// Validates [pb.SchedulerConfig] extracted from [CiYaml] files.
+  /// Validates [pb.SchedulerConfig] extracted from [CiYamlSet] files.
   ///
   /// A [pb.SchedulerConfig] file is considered good if:
   ///   1. It has at least one [pb.Target] in [pb.SchedulerConfig.targets]
@@ -258,14 +379,27 @@ class CiYaml {
             }
           }
         }
-        // TODO(flutter#157358) - Handle merged repository yaml files.
+
         // Verify runIf includes foundational files.
         if (target.runIf.isNotEmpty) {
-          if (!target.runIf.contains('.ci.yaml')) {
-            exceptions.add('ERROR: ${target.name} is missing `.ci.yaml` in runIf');
-          }
-          if (slug == Config.engineSlug && !target.runIf.contains('DEPS')) {
-            exceptions.add('ERROR: ${target.name} is missing `DEPS` in runIf');
+          if (isFusion && type == CiType.fusionEngine) {
+            // Look in different locations if fusion && engine ci.yaml
+            if (!target.runIf.contains('engine/src/flutter/.ci.yaml')) {
+              exceptions.add(
+                'ERROR: ${target.name} is missing `engine/src/flutter/.ci.yaml` in runIf',
+              );
+            }
+            if (!target.runIf.contains('DEPS')) {
+              exceptions.add('ERROR: ${target.name} is missing `DEPS` in runIf');
+            }
+          } else {
+            // not fusion or not engine in fusion.
+            if (!target.runIf.contains('.ci.yaml')) {
+              exceptions.add('ERROR: ${target.name} is missing `.ci.yaml` in runIf');
+            }
+            if (slug == Config.engineSlug && !target.runIf.contains('DEPS')) {
+              exceptions.add('ERROR: ${target.name} is missing `DEPS` in runIf');
+            }
           }
         }
       }
diff --git a/app_dart/lib/src/request_handlers/check_flaky_builders.dart b/app_dart/lib/src/request_handlers/check_flaky_builders.dart
index 74f363a41..2d44430ab 100644
--- a/app_dart/lib/src/request_handlers/check_flaky_builders.dart
+++ b/app_dart/lib/src/request_handlers/check_flaky_builders.dart
@@ -60,13 +60,13 @@ class CheckFlakyBuilders extends ApiRequestHandler<Body> {
     );
     final YamlMap? ci = loadYaml(ciContent) as YamlMap?;
     final pb.SchedulerConfig unCheckedSchedulerConfig = pb.SchedulerConfig()..mergeFromProto3Json(ci);
-    final CiYaml ciYaml = CiYaml(
+    final CiYamlSet ciYaml = CiYamlSet(
       slug: slug,
       branch: Config.defaultBranch(slug),
-      config: unCheckedSchedulerConfig,
+      yamls: {CiType.any: unCheckedSchedulerConfig},
     );
 
-    final pb.SchedulerConfig schedulerConfig = ciYaml.config;
+    final pb.SchedulerConfig schedulerConfig = ciYaml.configFor(CiType.any);
     final List<pb.Target> targets = schedulerConfig.targets;
 
     final List<_BuilderInfo> eligibleBuilders =
@@ -116,7 +116,7 @@ class CheckFlakyBuilders extends ApiRequestHandler<Body> {
     GithubService gitHub,
     RepositorySlug slug, {
     required String content,
-    required CiYaml ciYaml,
+    required CiYamlSet ciYaml,
   }) async {
     final YamlMap ci = loadYaml(content) as YamlMap;
     final YamlList targets = ci[kCiYamlTargetsKey] as YamlList;
@@ -164,7 +164,7 @@ class CheckFlakyBuilders extends ApiRequestHandler<Body> {
   }
 
   @visibleForTesting
-  static bool getIgnoreFlakiness(String? builderName, CiYaml ciYaml) {
+  static bool getIgnoreFlakiness(String? builderName, CiYamlSet ciYaml) {
     if (builderName == null) {
       return false;
     }
diff --git a/app_dart/lib/src/request_handlers/file_flaky_issue_and_pr.dart b/app_dart/lib/src/request_handlers/file_flaky_issue_and_pr.dart
index e3adefa80..721597010 100644
--- a/app_dart/lib/src/request_handlers/file_flaky_issue_and_pr.dart
+++ b/app_dart/lib/src/request_handlers/file_flaky_issue_and_pr.dart
@@ -41,13 +41,13 @@ class FileFlakyIssueAndPR extends ApiRequestHandler<Body> {
     final List<BuilderStatistic> builderStatisticList = await bigquery.listBuilderStatistic(kBigQueryProjectId);
     final YamlMap? ci = loadYaml(await gitHub.getFileContent(slug, kCiYamlPath)) as YamlMap?;
     final pb.SchedulerConfig unCheckedSchedulerConfig = pb.SchedulerConfig()..mergeFromProto3Json(ci);
-    final CiYaml ciYaml = CiYaml(
+    final CiYamlSet ciYaml = CiYamlSet(
       slug: slug,
       branch: Config.defaultBranch(slug),
-      config: unCheckedSchedulerConfig,
+      yamls: {CiType.any: unCheckedSchedulerConfig},
     );
 
-    final pb.SchedulerConfig schedulerConfig = ciYaml.config;
+    final pb.SchedulerConfig schedulerConfig = ciYaml.configFor(CiType.any);
     final List<pb.Target> targets = schedulerConfig.targets;
 
     final String testOwnerContent = await gitHub.getFileContent(slug, kTestOwnerPath);
@@ -89,7 +89,7 @@ class FileFlakyIssueAndPR extends ApiRequestHandler<Body> {
     });
   }
 
-  bool shouldSkip(BuilderStatistic statistic, CiYaml ciYaml, List<pb.Target> targets) {
+  bool shouldSkip(BuilderStatistic statistic, CiYamlSet ciYaml, List<pb.Target> targets) {
     // Skips if the target has been removed from .ci.yaml.
     if (!targets.map((e) => e.name).toList().contains(statistic.name)) {
       return true;
@@ -191,9 +191,9 @@ class FileFlakyIssueAndPR extends ApiRequestHandler<Body> {
   }
 
   @visibleForTesting
-  static bool getIgnoreFlakiness(String builderName, CiYaml ciYaml) {
+  static bool getIgnoreFlakiness(String builderName, CiYamlSet ciYaml) {
     final Target? target =
-        ciYaml.postsubmitTargets.singleWhereOrNull((Target target) => target.value.name == builderName);
+        ciYaml.postsubmitTargets().singleWhereOrNull((Target target) => target.value.name == builderName);
     return target == null ? false : target.getIgnoreFlakiness();
   }
 
diff --git a/app_dart/lib/src/request_handlers/flaky_handler_utils.dart b/app_dart/lib/src/request_handlers/flaky_handler_utils.dart
index 795b389e4..30f47208c 100644
--- a/app_dart/lib/src/request_handlers/flaky_handler_utils.dart
+++ b/app_dart/lib/src/request_handlers/flaky_handler_utils.dart
@@ -303,7 +303,7 @@ TestOwnership getTestOwnership(pb.Target target, BuilderType type, String testOw
 
 /// Gets the [BuilderType] of the builder by looking up the information in the
 /// ci.yaml.
-BuilderType getTypeForBuilder(String? targetName, CiYaml ciYaml, {bool unfilteredTargets = false}) {
+BuilderType getTypeForBuilder(String? targetName, CiYamlSet ciYaml, {bool unfilteredTargets = false}) {
   final List<String>? tags = _getTags(targetName, ciYaml, unfilteredTargets: unfilteredTargets);
   if (tags == null || tags.isEmpty) {
     return BuilderType.unknown;
@@ -332,13 +332,13 @@ BuilderType getTypeForBuilder(String? targetName, CiYaml ciYaml, {bool unfiltere
   return hasFrameworkTag && hasHostOnlyTag ? BuilderType.frameworkHostOnly : BuilderType.unknown;
 }
 
-List<String>? _getTags(String? targetName, CiYaml ciYaml, {bool unfilteredTargets = false}) {
+List<String>? _getTags(String? targetName, CiYamlSet ciYaml, {bool unfilteredTargets = false}) {
   final Set<Target> allUniqueTargets = {};
   if (!unfilteredTargets) {
-    allUniqueTargets.addAll(ciYaml.presubmitTargets);
-    allUniqueTargets.addAll(ciYaml.postsubmitTargets);
+    allUniqueTargets.addAll(ciYaml.presubmitTargets());
+    allUniqueTargets.addAll(ciYaml.postsubmitTargets());
   } else {
-    allUniqueTargets.addAll(ciYaml.targets);
+    allUniqueTargets.addAll(ciYaml.targets(type: CiType.any));
   }
 
   final Target? target = allUniqueTargets.firstWhereOrNull((element) => element.value.name == targetName);
diff --git a/app_dart/lib/src/request_handlers/postsubmit_luci_subscription.dart b/app_dart/lib/src/request_handlers/postsubmit_luci_subscription.dart
index 54ba49d79..646023ac9 100644
--- a/app_dart/lib/src/request_handlers/postsubmit_luci_subscription.dart
+++ b/app_dart/lib/src/request_handlers/postsubmit_luci_subscription.dart
@@ -128,8 +128,10 @@ class PostsubmitLuciSubscription extends SubscriptionHandler {
     }
 
     final Commit commit = await datastore.lookupByValue<Commit>(commitKey);
-    final CiYaml ciYaml = await scheduler.getCiYaml(commit);
-    final List<Target> postsubmitTargets = ciYaml.postsubmitTargets;
+
+    // TODO(codefu): handle fusion
+    final CiYamlSet ciYaml = await scheduler.getCiYaml(commit);
+    final List<Target> postsubmitTargets = ciYaml.postsubmitTargets();
     if (!postsubmitTargets.any((element) => element.value.name == firestoreTask!.taskName)) {
       log.warning('Target ${firestoreTask.taskName} has been deleted from TOT. Skip updating.');
       return Body.empty;
diff --git a/app_dart/lib/src/request_handlers/presubmit_luci_subscription.dart b/app_dart/lib/src/request_handlers/presubmit_luci_subscription.dart
index f20e0c638..7ad7f9e03 100644
--- a/app_dart/lib/src/request_handlers/presubmit_luci_subscription.dart
+++ b/app_dart/lib/src/request_handlers/presubmit_luci_subscription.dart
@@ -146,7 +146,7 @@ class PresubmitLuciSubscription extends SubscriptionHandler {
       repository: slug.fullName,
       sha: userData['commit_sha'] as String,
     );
-    late CiYaml ciYaml;
+    late CiYamlSet ciYaml;
     try {
       if (commit.branch == Config.defaultBranch(commit.slug)) {
         ciYaml = await scheduler.getCiYaml(commit, validate: true);
@@ -159,16 +159,18 @@ class PresubmitLuciSubscription extends SubscriptionHandler {
       return 0;
     }
 
+    // TODO(codefu): support fusion
+
     // Do not block on the target not found.
-    if (!ciYaml.presubmitTargets.any((element) => element.value.name == builderName)) {
+    if (!ciYaml.presubmitTargets().any((element) => element.value.name == builderName)) {
       // do not reschedule
       log.warning('Did not find builder with name: $builderName in ciYaml for ${commit.sha}');
-      final List<String> availableBuilderList = ciYaml.presubmitTargets.map((Target e) => e.value.name).toList();
+      final List<String> availableBuilderList = ciYaml.presubmitTargets().map((Target e) => e.value.name).toList();
       log.warning('ciYaml presubmit targets found: $availableBuilderList');
       return 1;
     }
 
-    final Target target = ciYaml.presubmitTargets.where((element) => element.value.name == builderName).single;
+    final Target target = ciYaml.presubmitTargets().where((element) => element.value.name == builderName).single;
     final Map<String, Object> properties = target.getProperties();
     if (!properties.containsKey('presubmit_max_attempts')) {
       return 1;
diff --git a/app_dart/lib/src/request_handlers/reset_prod_task.dart b/app_dart/lib/src/request_handlers/reset_prod_task.dart
index 8965e0ae2..3cf376df0 100644
--- a/app_dart/lib/src/request_handlers/reset_prod_task.dart
+++ b/app_dart/lib/src/request_handlers/reset_prod_task.dart
@@ -153,8 +153,9 @@ class ResetProdTask extends ApiRequestHandler<Body> {
     sha ??= commit.id!.split('/').last;
     taskName ??= task.name;
 
-    final CiYaml ciYaml = await scheduler.getCiYaml(commit);
-    final Target target = ciYaml.postsubmitTargets.singleWhere((Target target) => target.value.name == task.name);
+    // TODO(codefu): handle fusion
+    final CiYamlSet ciYaml = await scheduler.getCiYaml(commit);
+    final Target target = ciYaml.postsubmitTargets().singleWhere((Target target) => target.value.name == task.name);
 
     // Prepares Firestore task.
     firestore.Task? taskDocument;
diff --git a/app_dart/lib/src/request_handlers/scheduler/batch_backfiller.dart b/app_dart/lib/src/request_handlers/scheduler/batch_backfiller.dart
index f4ece8658..6c4aad098 100644
--- a/app_dart/lib/src/request_handlers/scheduler/batch_backfiller.dart
+++ b/app_dart/lib/src/request_handlers/scheduler/batch_backfiller.dart
@@ -66,8 +66,11 @@ class BatchBackfiller extends RequestHandler {
     List<Tuple<Target, FullTask, int>> backfill = <Tuple<Target, FullTask, int>>[];
     for (List<FullTask> taskColumn in taskMap.values) {
       final FullTask task = taskColumn.first;
-      final CiYaml ciYaml = await scheduler.getCiYaml(task.commit);
-      final List<Target> ciYamlTargets = ciYaml.backfillTargets;
+
+      // TODO(codefu): handle fusion
+      final CiYamlSet ciYaml = await scheduler.getCiYaml(task.commit);
+      final List<Target> ciYamlTargets = ciYaml.backfillTargets();
+
       // Skips scheduling if the task is not in TOT commit anymore.
       final bool taskInToT = ciYamlTargets.map((Target target) => target.value.name).toList().contains(task.task.name);
       if (!taskInToT) {
diff --git a/app_dart/lib/src/request_handlers/update_existing_flaky_issues.dart b/app_dart/lib/src/request_handlers/update_existing_flaky_issues.dart
index 266abaa92..c8ea9c83c 100644
--- a/app_dart/lib/src/request_handlers/update_existing_flaky_issues.dart
+++ b/app_dart/lib/src/request_handlers/update_existing_flaky_issues.dart
@@ -34,7 +34,7 @@ class UpdateExistingFlakyIssue extends ApiRequestHandler<Body> {
   static const String kThresholdKey = 'threshold';
   static const int kFreshPeriodForOpenFlake = 7; // days
 
-  final CiYaml? ciYaml;
+  final CiYamlSet? ciYaml;
 
   @override
   Future<Body> get() async {
@@ -42,7 +42,7 @@ class UpdateExistingFlakyIssue extends ApiRequestHandler<Body> {
     final GithubService gitHub = config.createGithubServiceWithToken(await config.githubOAuthToken);
     final BigqueryService bigquery = await config.createBigQueryService();
 
-    CiYaml? localCiYaml = ciYaml;
+    CiYamlSet? localCiYaml = ciYaml;
     if (localCiYaml == null) {
       final YamlMap? ci = loadYaml(
         await gitHub.getFileContent(
@@ -51,10 +51,10 @@ class UpdateExistingFlakyIssue extends ApiRequestHandler<Body> {
         ),
       ) as YamlMap?;
       final pb.SchedulerConfig unCheckedSchedulerConfig = pb.SchedulerConfig()..mergeFromProto3Json(ci);
-      localCiYaml = CiYaml(
+      localCiYaml = CiYamlSet(
         slug: slug,
         branch: Config.defaultBranch(slug),
-        config: unCheckedSchedulerConfig,
+        yamls: {CiType.any: unCheckedSchedulerConfig},
       );
     }
 
@@ -90,7 +90,7 @@ class UpdateExistingFlakyIssue extends ApiRequestHandler<Body> {
     required bool bringup,
     required BuilderStatistic statistic,
     required Issue existingIssue,
-    required CiYaml ciYaml,
+    required CiYamlSet ciYaml,
   }) async {
     if (DateTime.now().difference(existingIssue.createdAt!) < const Duration(days: kFreshPeriodForOpenFlake)) {
       return;
@@ -110,7 +110,7 @@ class UpdateExistingFlakyIssue extends ApiRequestHandler<Body> {
         kTestOwnerPath,
       );
 
-      final pb.SchedulerConfig schedulerConfig = ciYaml.config;
+      final pb.SchedulerConfig schedulerConfig = ciYaml.configFor(CiType.any);
       final List<pb.Target> targets = schedulerConfig.targets;
 
       final String? testOwner = getTestOwnership(
@@ -128,14 +128,14 @@ class UpdateExistingFlakyIssue extends ApiRequestHandler<Body> {
   Future<void> _updateExistingFlakyIssue(
     GithubService gitHub,
     RepositorySlug slug,
-    CiYaml ciYaml, {
+    CiYamlSet ciYaml, {
     required List<BuilderStatistic> prodBuilderStatisticList,
     required List<BuilderStatistic> stagingBuilderStatisticList,
     required Map<String?, Issue> nameToExistingIssue,
   }) async {
     final Map<String, bool> builderFlakyMap = <String, bool>{};
     final Map<String, bool> ignoreFlakyMap = <String, bool>{};
-    for (Target target in ciYaml.postsubmitTargets) {
+    for (Target target in ciYaml.postsubmitTargets()) {
       builderFlakyMap[target.value.name] = target.value.bringup;
       if (target.getIgnoreFlakiness()) {
         ignoreFlakyMap[target.value.name] = true;
diff --git a/app_dart/lib/src/service/scheduler.dart b/app_dart/lib/src/service/scheduler.dart
index f52361939..7c05b09c6 100644
--- a/app_dart/lib/src/service/scheduler.dart
+++ b/app_dart/lib/src/service/scheduler.dart
@@ -14,6 +14,7 @@ import 'package:github/github.dart';
 import 'package:github/hooks.dart';
 import 'package:googleapis/bigquery/v2.dart';
 import 'package:googleapis/firestore/v1.dart';
+import 'package:meta/meta.dart';
 import 'package:retry/retry.dart';
 import 'package:truncate/truncate.dart';
 import 'package:yaml/yaml.dart';
@@ -50,6 +51,7 @@ class Scheduler {
     required this.config,
     required this.githubChecksService,
     required this.luciBuildService,
+    required this.fusionTester,
     this.datastoreProvider = DatastoreService.defaultProvider,
     this.httpClientProvider = Providers.freshHttpClient,
     this.buildStatusProvider = BuildStatusService.defaultProvider,
@@ -61,7 +63,7 @@ class Scheduler {
   final DatastoreServiceProvider datastoreProvider;
   final GithubChecksService githubChecksService;
   final HttpClientProvider httpClientProvider;
-
+  final FusionTester fusionTester;
   late DatastoreService datastore;
   late FirestoreService firestoreService;
   LuciBuildService luciBuildService;
@@ -144,9 +146,10 @@ class Scheduler {
       return;
     }
 
-    final CiYaml ciYaml = await getCiYaml(commit);
+    final CiYamlSet ciYaml = await getCiYaml(commit);
 
-    final List<Target> initialTargets = ciYaml.getInitialTargets(ciYaml.postsubmitTargets);
+    // TODO(codefu): support fusion engine
+    final List<Target> initialTargets = ciYaml.getInitialTargets(ciYaml.postsubmitTargets());
     final List<Task> tasks = targetsToTask(commit, initialTargets).toList();
 
     final List<Tuple<Target, Task, int>> toBeScheduled = <Tuple<Target, Task, int>>[];
@@ -240,65 +243,84 @@ class Scheduler {
   }
 
   /// Process and filters ciyaml.
-  Future<CiYaml> getCiYaml(
+  Future<CiYamlSet> getCiYaml(
     Commit commit, {
     bool validate = false,
   }) async {
+    final isFusion = await fusionTester.isFusionBasedRef(commit.slug, commit.sha!);
     final Commit totCommit = await generateTotCommit(slug: commit.slug, branch: Config.defaultBranch(commit.slug));
-    final CiYaml totYaml = await _getCiYaml(totCommit);
-    return _getCiYaml(commit, totCiYaml: totYaml, validate: validate);
+    final CiYamlSet totYaml = await _getCiYaml(totCommit, isFusionCommit: isFusion);
+    return _getCiYaml(commit, totCiYaml: totYaml, validate: validate, isFusionCommit: isFusion);
   }
 
   /// Load in memory the `.ci.yaml`.
-  Future<CiYaml> _getCiYaml(
+  Future<CiYamlSet> _getCiYaml(
     Commit commit, {
-    CiYaml? totCiYaml,
+    CiYamlSet? totCiYaml,
     bool validate = false,
     RetryOptions retryOptions = const RetryOptions(delayFactor: Duration(seconds: 2), maxAttempts: 4),
+    bool isFusionCommit = false,
   }) async {
-    String ciPath;
-    ciPath = '${commit.repository}/${commit.sha!}/$kCiYamlPath';
-    final Uint8List ciYamlBytes = (await cache.getOrCreate(
-      subcacheName,
-      ciPath,
-      createFn: () => _downloadCiYaml(
-        commit,
-        ciPath,
-        retryOptions: retryOptions,
-      ),
-      ttl: const Duration(hours: 1),
-    ))!;
-    final pb.SchedulerConfig schedulerConfig = pb.SchedulerConfig.fromBuffer(ciYamlBytes);
-    log.fine('Retrieved .ci.yaml for $ciPath');
+    Future<pb.SchedulerConfig> getSchedulerConfig(String ciPath) async {
+      final Uint8List ciYamlBytes = (await cache.getOrCreate(
+        subcacheName,
+        // This is a key for a cache; not a path - so its needs to be 'unique'
+        '${commit.repository}/${commit.sha!}/$ciPath',
+        createFn: () async => (await _downloadCiYaml(
+          commit,
+          // actual path to go and fetch
+          ciPath,
+          retryOptions: retryOptions,
+        ))
+            .writeToBuffer(),
+        ttl: const Duration(hours: 1),
+      ))!;
+      final pb.SchedulerConfig schedulerConfig = pb.SchedulerConfig.fromBuffer(ciYamlBytes);
+      log.fine('Retrieved .ci.yaml for $ciPath');
+      return schedulerConfig;
+    }
+
+    // First, whatever was asked of us.
+    final schedulerConfig = await getSchedulerConfig(kCiYamlPath);
+
+    // Second - maybe the engine CI
+    pb.SchedulerConfig? engineFusionConfig;
+    if (isFusionCommit) {
+      // Fetch the engine yaml and mark it up.
+      engineFusionConfig = await getSchedulerConfig(kCiYamlFusionEnginePath);
+      log.fine('fusion engine .ci.yaml file fetched');
+    }
+
     // If totCiYaml is not null, we assume upper level function has verified that current branch is not a release branch.
-    return CiYaml(
-      config: schedulerConfig,
+    return CiYamlSet(
+      yamls: {
+        CiType.any: schedulerConfig,
+        if (engineFusionConfig != null) CiType.fusionEngine: engineFusionConfig,
+      },
       slug: commit.slug,
       branch: commit.branch!,
       totConfig: totCiYaml,
       validate: validate,
+      isFusion: isFusionCommit,
     );
   }
 
-  /// Get `.ci.yaml` from GitHub, and store the bytes in redis for future retrieval.
-  ///
-  /// If GitHub returns [HttpStatus.notFound], an empty config will be inserted assuming
-  /// that commit does not support the scheduler config file.
-  Future<Uint8List> _downloadCiYaml(
+  /// Get `.ci.yaml` from GitHub
+  Future<pb.SchedulerConfig> _downloadCiYaml(
     Commit commit,
     String ciPath, {
     RetryOptions retryOptions = const RetryOptions(maxAttempts: 3),
   }) async {
     final String configContent = await githubFileContent(
       commit.slug,
-      '.ci.yaml',
+      ciPath,
       httpClientProvider: httpClientProvider,
       ref: commit.sha!,
       retryOptions: retryOptions,
     );
     final YamlMap configYaml = loadYaml(configContent) as YamlMap;
     final pb.SchedulerConfig schedulerConfig = pb.SchedulerConfig()..mergeFromProto3Json(configYaml);
-    return schedulerConfig.writeToBuffer();
+    return schedulerConfig;
   }
 
   /// Cancel all incomplete targets against a pull request.
@@ -317,7 +339,7 @@ class Scheduler {
   ///
   /// Cancels all existing targets then schedules the targets.
   ///
-  /// Schedules a [kCiYamlCheckName] to validate [CiYaml] is valid and all builds were able to be triggered.
+  /// Schedules a [kCiYamlCheckName] to validate [CiYamlSet] is valid and all builds were able to be triggered.
   /// If [builderTriggerList] is specified, then trigger only those targets.
   Future<void> triggerPresubmitTargets({
     required PullRequest pullRequest,
@@ -585,13 +607,14 @@ class Scheduler {
   /// Filters targets with runIf, matching them to the diff of [pullRequest].
   ///
   /// In the case there is an issue getting the diff from GitHub, all targets are returned.
-  Future<List<Target>> getPresubmitTargets(PullRequest pullRequest) async {
+  @visibleForTesting
+  Future<List<Target>> getPresubmitTargets(PullRequest pullRequest, {CiType type = CiType.any}) async {
     final Commit commit = Commit(
       branch: pullRequest.base!.ref,
       repository: pullRequest.base!.repo!.fullName,
       sha: pullRequest.head!.sha,
     );
-    late CiYaml ciYaml;
+    late CiYamlSet ciYaml;
     log.info('Attempting to read presubmit targets from ci.yaml for ${pullRequest.number}');
     if (commit.branch == Config.defaultBranch(commit.slug)) {
       ciYaml = await getCiYaml(commit, validate: true);
@@ -601,8 +624,10 @@ class Scheduler {
     log.info('ci.yaml loaded successfully.');
     log.info('Collecting presubmit targets for ${pullRequest.number}');
 
+    final inner = ciYaml.ciYamlFor(type);
+
     // Filter out schedulers targets with schedulers different than luci or cocoon.
-    final List<Target> presubmitTargets = ciYaml.presubmitTargets
+    final List<Target> presubmitTargets = inner.presubmitTargets
         .where(
           (Target target) =>
               target.value.scheduler == pb.SchedulerSystem.luci || target.value.scheduler == pb.SchedulerSystem.cocoon,
@@ -610,11 +635,11 @@ class Scheduler {
         .toList();
 
     // See https://github.com/flutter/flutter/issues/138430.
-    final includePostsubmitAsPresubmit = _includePostsubmitAsPresubmit(ciYaml, pullRequest);
+    final includePostsubmitAsPresubmit = _includePostsubmitAsPresubmit(inner, pullRequest);
     if (includePostsubmitAsPresubmit) {
       log.info('Including postsubmit targets as presubmit for ${pullRequest.number}');
 
-      for (Target target in ciYaml.postsubmitTargets) {
+      for (Target target in inner.postsubmitTargets) {
         // We don't want to include a presubmit twice
         // We don't want to run the builder_cache target as a presubmit
         if (!target.value.presubmit && !target.value.properties.containsKey('cache_name')) {
@@ -674,6 +699,7 @@ class Scheduler {
   /// Relevant APIs:
   ///   https://developer.github.com/v3/checks/runs/#check-runs-and-requested-actions
   Future<bool> processCheckRun(cocoon_checks.CheckRunEvent checkRunEvent) async {
+    // TODO(codefu): Figure out if we're in fusion or not.
     switch (checkRunEvent.action) {
       case 'rerequested':
         log.fine('Rerun requested by GitHub user: ${checkRunEvent.sender?.login}');
@@ -726,9 +752,9 @@ class Scheduler {
               final firestore.Task taskDocument =
                   taskDocuments.where((taskDocument) => taskDocument.taskName == checkName).toList().first;
               log.fine('Latest firestore task is $taskDocument');
-              final CiYaml ciYaml = await getCiYaml(commit);
+              final CiYamlSet ciYaml = await getCiYaml(commit);
               final Target target =
-                  ciYaml.postsubmitTargets.singleWhere((Target target) => target.value.name == task.name);
+                  ciYaml.postsubmitTargets().singleWhere((Target target) => target.value.name == task.name);
               await luciBuildService.reschedulePostsubmitBuildUsingCheckRunEvent(
                 checkRunEvent,
                 commit: commit,
@@ -799,8 +825,8 @@ class Scheduler {
 
   /// Returns the tip of tree [Commit] using specified [branch] and [RepositorySlug].
   ///
-  /// A tip of tree [Commit] is used to help generate the tip of tree [CiYaml].
-  /// The generated tip of tree [CiYaml] will be compared against Presubmit Targets in current [CiYaml],
+  /// A tip of tree [Commit] is used to help generate the tip of tree [CiYamlSet].
+  /// The generated tip of tree [CiYamlSet] will be compared against Presubmit Targets in current [CiYamlSet],
   /// to ensure new targets without `bringup: true` label are not added into the build.
   Future<Commit> generateTotCommit({required String branch, required RepositorySlug slug}) async {
     datastore = datastoreProvider(config.db);
diff --git a/app_dart/test/model/ci_yaml/ci_yaml_test.dart b/app_dart/test/model/ci_yaml/ci_yaml_test.dart
index 7ed24bad5..58e4f68b1 100644
--- a/app_dart/test/model/ci_yaml/ci_yaml_test.dart
+++ b/app_dart/test/model/ci_yaml/ci_yaml_test.dart
@@ -62,8 +62,8 @@ void main() {
 
   group('initialTargets', () {
     test('targets without deps', () {
-      final CiYaml ciYaml = exampleConfig;
-      final List<Target> initialTargets = ciYaml.getInitialTargets(ciYaml.postsubmitTargets);
+      final ciYaml = exampleConfig;
+      final List<Target> initialTargets = ciYaml.getInitialTargets(ciYaml.postsubmitTargets());
       final List<String> initialTargetNames = initialTargets.map((Target target) => target.value.name).toList();
       expect(
         initialTargetNames,
@@ -78,25 +78,27 @@ void main() {
     });
 
     test('filter bringup targets on release branches', () {
-      final CiYaml ciYaml = CiYaml(
+      final CiYamlSet ciYaml = CiYamlSet(
         slug: Config.flutterSlug,
         branch: Config.defaultBranch(Config.flutterSlug),
-        config: pb.SchedulerConfig(
-          enabledBranches: <String>[
-            Config.defaultBranch(Config.flutterSlug),
-          ],
-          targets: <pb.Target>[
-            pb.Target(
-              name: 'Linux A',
-            ),
-            pb.Target(
-              name: 'Mac A', // Should be ignored on release branches
-              bringup: true,
-            ),
-          ],
-        ),
+        yamls: {
+          CiType.any: pb.SchedulerConfig(
+            enabledBranches: <String>[
+              Config.defaultBranch(Config.flutterSlug),
+            ],
+            targets: <pb.Target>[
+              pb.Target(
+                name: 'Linux A',
+              ),
+              pb.Target(
+                name: 'Mac A', // Should be ignored on release branches
+                bringup: true,
+              ),
+            ],
+          ),
+        },
       );
-      final List<Target> initialTargets = ciYaml.getInitialTargets(ciYaml.postsubmitTargets);
+      final List<Target> initialTargets = ciYaml.getInitialTargets(ciYaml.postsubmitTargets());
       final List<String> initialTargetNames = initialTargets.map((Target target) => target.value.name).toList();
       expect(
         initialTargetNames,
@@ -110,6 +112,7 @@ void main() {
 
     group('validations and filters.', () {
       final CiYaml totCIYaml = CiYaml(
+        type: CiType.any,
         slug: Config.flutterSlug,
         branch: Config.defaultBranch(Config.flutterSlug),
         config: pb.SchedulerConfig(
@@ -128,6 +131,7 @@ void main() {
         ),
       );
       final CiYaml ciYaml = CiYaml(
+        type: CiType.any,
         slug: Config.flutterSlug,
         branch: 'flutter-2.4-candidate.3',
         config: pb.SchedulerConfig(
@@ -177,8 +181,8 @@ void main() {
       });
 
       test('Get backfill targets from postsubmit', () {
-        final CiYaml ciYaml = exampleBackfillConfig;
-        final List<Target> backfillTargets = ciYaml.backfillTargets;
+        final ciYaml = exampleBackfillConfig;
+        final List<Target> backfillTargets = ciYaml.backfillTargets();
         final List<String> backfillTargetNames = backfillTargets.map((Target target) => target.value.name).toList();
         expect(
           backfillTargetNames,
@@ -193,6 +197,7 @@ void main() {
 
       test('filter release_build targets from release candidate branches', () {
         final CiYaml releaseYaml = CiYaml(
+          type: CiType.any,
           slug: Config.flutterSlug,
           branch: 'flutter-2.4-candidate.3',
           config: pb.SchedulerConfig(
@@ -222,6 +227,7 @@ void main() {
 
       test('release_build targets for main are not filtered', () {
         final CiYaml releaseYaml = CiYaml(
+          type: CiType.any,
           slug: Config.flutterSlug,
           branch: 'main',
           config: pb.SchedulerConfig(
@@ -256,6 +262,7 @@ void main() {
       test('validates yaml config', () {
         expect(
           () => CiYaml(
+            type: CiType.any,
             slug: Config.flutterSlug,
             branch: Config.defaultBranch(Config.flutterSlug),
             config: pb.SchedulerConfig(
@@ -280,6 +287,7 @@ void main() {
     });
     group('Presubmit validation', () {
       final CiYaml totCIYaml = CiYaml(
+        type: CiType.any,
         slug: Config.flutterSlug,
         branch: Config.defaultBranch(Config.flutterSlug),
         config: pb.SchedulerConfig(
@@ -299,6 +307,7 @@ void main() {
         ),
       );
       final CiYaml ciYaml = CiYaml(
+        type: CiType.any,
         slug: Config.flutterSlug,
         branch: 'flutter-2.4-candidate.3',
         config: pb.SchedulerConfig(
@@ -336,14 +345,14 @@ void main() {
 
   group('flakiness_threshold', () {
     test('is set', () {
-      final CiYaml ciYaml = exampleFlakyConfig;
+      final ciYaml = exampleFlakyConfig;
       final flaky1 = ciYaml.getFirstPostsubmitTarget('Flaky 1');
       expect(flaky1, isNotNull);
       expect(flaky1?.flakinessThreshold, 0.04);
     });
 
     test('is missing', () {
-      final CiYaml ciYaml = exampleFlakyConfig;
+      final ciYaml = exampleFlakyConfig;
       final flaky1 = ciYaml.getFirstPostsubmitTarget('Flaky Skip');
       expect(flaky1, isNotNull);
       expect(flaky1?.flakinessThreshold, isNull);
diff --git a/app_dart/test/request_handlers/check_flaky_builders_test.dart b/app_dart/test/request_handlers/check_flaky_builders_test.dart
index 2d86a6d15..2c64e7e0a 100644
--- a/app_dart/test/request_handlers/check_flaky_builders_test.dart
+++ b/app_dart/test/request_handlers/check_flaky_builders_test.dart
@@ -29,8 +29,6 @@ const String kCurrentUserName = 'Name';
 const String kCurrentUserLogin = 'login';
 const String kCurrentUserEmail = 'login@email.com';
 
-class MockYaml extends Mock implements CiYaml {}
-
 void main() {
   group('Deflake', () {
     late CheckFlakyBuilders handler;
@@ -659,10 +657,10 @@ void main() {
     test('getIgnoreFlakiness handles non-existing builderame', () async {
       final YamlMap? ci = loadYaml(ciYamlContent) as YamlMap?;
       final pb.SchedulerConfig unCheckedSchedulerConfig = pb.SchedulerConfig()..mergeFromProto3Json(ci);
-      final CiYaml ciYaml = CiYaml(
+      final CiYamlSet ciYaml = CiYamlSet(
         slug: Config.flutterSlug,
         branch: Config.defaultBranch(Config.flutterSlug),
-        config: unCheckedSchedulerConfig,
+        yamls: {CiType.any: unCheckedSchedulerConfig},
       );
       CheckFlakyBuilders.getIgnoreFlakiness('Non_existing', ciYaml);
     });
diff --git a/app_dart/test/request_handlers/file_flaky_issue_and_pr_test.dart b/app_dart/test/request_handlers/file_flaky_issue_and_pr_test.dart
index 9fd1d165a..0274626cc 100644
--- a/app_dart/test/request_handlers/file_flaky_issue_and_pr_test.dart
+++ b/app_dart/test/request_handlers/file_flaky_issue_and_pr_test.dart
@@ -676,10 +676,10 @@ void main() {
     test('skips when the target doesn not exist', () {
       final YamlMap? ci = loadYaml(ciYamlContent) as YamlMap?;
       final pb.SchedulerConfig unCheckedSchedulerConfig = pb.SchedulerConfig()..mergeFromProto3Json(ci);
-      final CiYaml ciYaml = CiYaml(
+      final CiYamlSet ciYaml = CiYamlSet(
         slug: Config.flutterSlug,
         branch: Config.defaultBranch(Config.flutterSlug),
-        config: unCheckedSchedulerConfig,
+        yamls: {CiType.any: unCheckedSchedulerConfig},
       );
       final BuilderStatistic builderStatistic = BuilderStatistic(
         name: 'Mac_android test',
@@ -698,10 +698,10 @@ void main() {
     test('skips if the flakiness_threshold is not met', () {
       final YamlMap? ci = loadYaml(ciYamlContent) as YamlMap?;
       final pb.SchedulerConfig unCheckedSchedulerConfig = pb.SchedulerConfig()..mergeFromProto3Json(ci);
-      final CiYaml ciYaml = CiYaml(
+      final CiYamlSet ciYaml = CiYamlSet(
         slug: Config.flutterSlug,
         branch: Config.defaultBranch(Config.flutterSlug),
-        config: unCheckedSchedulerConfig,
+        yamls: {CiType.any: unCheckedSchedulerConfig},
       );
       final BuilderStatistic builderStatistic = BuilderStatistic(
         name: 'Mac_android higher_myflakiness',
@@ -724,10 +724,10 @@ void main() {
     test('honors the flakiness_threshold', () {
       final YamlMap? ci = loadYaml(ciYamlContent) as YamlMap?;
       final pb.SchedulerConfig unCheckedSchedulerConfig = pb.SchedulerConfig()..mergeFromProto3Json(ci);
-      final CiYaml ciYaml = CiYaml(
+      final CiYamlSet ciYaml = CiYamlSet(
         slug: Config.flutterSlug,
         branch: Config.defaultBranch(Config.flutterSlug),
-        config: unCheckedSchedulerConfig,
+        yamls: {CiType.any: unCheckedSchedulerConfig},
       );
       final BuilderStatistic builderStatistic = BuilderStatistic(
         name: 'Mac_android higher_myflakiness',
@@ -758,10 +758,10 @@ void main() {
   test('getIgnoreFlakiness handles non-existing builderame', () async {
     final YamlMap? ci = loadYaml(ciYamlContent) as YamlMap?;
     final pb.SchedulerConfig unCheckedSchedulerConfig = pb.SchedulerConfig()..mergeFromProto3Json(ci);
-    final CiYaml ciYaml = CiYaml(
+    final CiYamlSet ciYaml = CiYamlSet(
       slug: Config.flutterSlug,
       branch: Config.defaultBranch(Config.flutterSlug),
-      config: unCheckedSchedulerConfig,
+      yamls: {CiType.any: unCheckedSchedulerConfig},
     );
     expect(FileFlakyIssueAndPR.getIgnoreFlakiness('Non_existing', ciYaml), false);
   });
diff --git a/app_dart/test/request_handlers/update_existing_flaky_issues_test_data.dart b/app_dart/test/request_handlers/update_existing_flaky_issues_test_data.dart
index d4658014c..76d4d0016 100644
--- a/app_dart/test/request_handlers/update_existing_flaky_issues_test_data.dart
+++ b/app_dart/test/request_handlers/update_existing_flaky_issues_test_data.dart
@@ -223,84 +223,86 @@ https://flutter-dashboard.appspot.com/#/build?taskFilter=Linux%20ci_yaml_flutter
 Please follow https://github.com/flutter/flutter/blob/master/docs/infra/Reducing-Test-Flakiness.md#fixing-flaky-tests to fix the flakiness and enable the test back after validating the fix (internal dashboard to validate: go/flutter_test_flakiness).
 ''';
 
-final CiYaml testCiYaml = CiYaml(
+final CiYamlSet testCiYaml = CiYamlSet(
   slug: Config.flutterSlug,
   branch: Config.defaultBranch(Config.flutterSlug),
-  config: pb.SchedulerConfig(
-    enabledBranches: <String>[
-      Config.defaultBranch(Config.flutterSlug),
-    ],
-    targets: <pb.Target>[
-      pb.Target(
-        name: 'Mac_android android_semantics_integration_test',
-        scheduler: pb.SchedulerSystem.luci,
-        presubmit: false,
-        properties: <String, String>{
-          'tags': jsonEncode(['devicelab']),
-          'task_name': 'android_semantics_integration_test',
-        },
-      ),
-      pb.Target(
-        name: 'Mac_android ignore_myflakiness',
-        scheduler: pb.SchedulerSystem.luci,
-        presubmit: false,
-        properties: <String, String>{
-          'ignore_flakiness': 'true',
-          'tags': jsonEncode(['devicelab']),
-          'task_name': 'ignore_myflakiness',
-        },
-      ),
-      pb.Target(
-        name: 'Linux ci_yaml flutter roller',
-        scheduler: pb.SchedulerSystem.luci,
-        bringup: true,
-        timeout: 30,
-        runIf: ['.ci.yaml'],
-        recipe: 'infra/ci_yaml',
-        properties: <String, String>{
-          'tags': jsonEncode(['framework', 'hostonly', 'shard']),
-        },
-      ),
-      pb.Target(
-        name: 'Mac build_tests_1_4',
-        scheduler: pb.SchedulerSystem.luci,
-        recipe: 'flutter/flutter_drone',
-        timeout: 60,
-        properties: <String, String>{
-          'add_recipes_cq': 'true',
-          'shard': 'build_tests',
-          'subshard': '1_4',
-          'tags': jsonEncode(['framework', 'hostonly', 'shard']),
-          'dependencies': jsonEncode([
-            {
-              'dependency': 'android_sdk',
-              'version': 'version:29.0',
-            },
-            {
-              'dependency': 'chrome_and_driver',
-              'version': 'version:84',
-            },
-            {
-              'dependency': 'xcode',
-              'version': '13a233',
-            },
-            {
-              'dependency': 'open_jdk',
-              'version': '11',
-            },
-            {
-              'dependency': 'gems',
-              'version': 'v3.3.14',
-            },
-            {
-              'dependency': 'goldctl',
-              'version': 'git_revision:3a77d0b12c697a840ca0c7705208e8622dc94603',
-            },
-          ]),
-        },
-      ),
-    ],
-  ),
+  yamls: {
+    CiType.any: pb.SchedulerConfig(
+      enabledBranches: <String>[
+        Config.defaultBranch(Config.flutterSlug),
+      ],
+      targets: <pb.Target>[
+        pb.Target(
+          name: 'Mac_android android_semantics_integration_test',
+          scheduler: pb.SchedulerSystem.luci,
+          presubmit: false,
+          properties: <String, String>{
+            'tags': jsonEncode(['devicelab']),
+            'task_name': 'android_semantics_integration_test',
+          },
+        ),
+        pb.Target(
+          name: 'Mac_android ignore_myflakiness',
+          scheduler: pb.SchedulerSystem.luci,
+          presubmit: false,
+          properties: <String, String>{
+            'ignore_flakiness': 'true',
+            'tags': jsonEncode(['devicelab']),
+            'task_name': 'ignore_myflakiness',
+          },
+        ),
+        pb.Target(
+          name: 'Linux ci_yaml flutter roller',
+          scheduler: pb.SchedulerSystem.luci,
+          bringup: true,
+          timeout: 30,
+          runIf: ['.ci.yaml'],
+          recipe: 'infra/ci_yaml',
+          properties: <String, String>{
+            'tags': jsonEncode(['framework', 'hostonly', 'shard']),
+          },
+        ),
+        pb.Target(
+          name: 'Mac build_tests_1_4',
+          scheduler: pb.SchedulerSystem.luci,
+          recipe: 'flutter/flutter_drone',
+          timeout: 60,
+          properties: <String, String>{
+            'add_recipes_cq': 'true',
+            'shard': 'build_tests',
+            'subshard': '1_4',
+            'tags': jsonEncode(['framework', 'hostonly', 'shard']),
+            'dependencies': jsonEncode([
+              {
+                'dependency': 'android_sdk',
+                'version': 'version:29.0',
+              },
+              {
+                'dependency': 'chrome_and_driver',
+                'version': 'version:84',
+              },
+              {
+                'dependency': 'xcode',
+                'version': '13a233',
+              },
+              {
+                'dependency': 'open_jdk',
+                'version': '11',
+              },
+              {
+                'dependency': 'gems',
+                'version': 'v3.3.14',
+              },
+              {
+                'dependency': 'goldctl',
+                'version': 'git_revision:3a77d0b12c697a840ca0c7705208e8622dc94603',
+              },
+            ]),
+          },
+        ),
+      ],
+    ),
+  },
 );
 
 const String testOwnersContent = '''
diff --git a/app_dart/test/server_test.dart b/app_dart/test/server_test.dart
index 9684e8022..262333a21 100644
--- a/app_dart/test/server_test.dart
+++ b/app_dart/test/server_test.dart
@@ -10,6 +10,7 @@ import 'package:test/test.dart';
 import 'src/datastore/fake_config.dart';
 import 'src/request_handling/fake_authentication.dart';
 import 'src/service/fake_build_bucket_client.dart';
+import 'src/service/fake_fusion_tester.dart';
 import 'src/service/fake_gerrit_service.dart';
 import 'src/service/fake_luci_build_service.dart';
 import 'src/service/fake_scheduler.dart';
@@ -30,6 +31,7 @@ void main() {
       commitService: CommitService(config: FakeConfig()),
       gerritService: FakeGerritService(),
       scheduler: FakeScheduler(config: FakeConfig()),
+      fusionTester: FakeFusionTester(),
     );
   });
 }
diff --git a/app_dart/test/service/scheduler/graph_test.dart b/app_dart/test/service/scheduler/graph_test.dart
index 2c3b96ad3..cf457347e 100644
--- a/app_dart/test/service/scheduler/graph_test.dart
+++ b/app_dart/test/service/scheduler/graph_test.dart
@@ -25,6 +25,7 @@ targets:
       ''') as YamlMap?;
       final SchedulerConfig unCheckedSchedulerConfig = SchedulerConfig()..mergeFromProto3Json(singleTargetConfig);
       final SchedulerConfig schedulerConfig = CiYaml(
+        type: CiType.any,
         slug: Config.flutterSlug,
         branch: Config.defaultBranch(Config.flutterSlug),
         config: unCheckedSchedulerConfig,
@@ -57,6 +58,7 @@ targets:
           final SchedulerConfig unCheckedSchedulerConfig = SchedulerConfig()
             ..mergeFromProto3Json(targetWithNonexistentScheduler);
           CiYaml(
+            type: CiType.any,
             slug: Config.flutterSlug,
             branch: Config.defaultBranch(Config.flutterSlug),
             config: unCheckedSchedulerConfig,
@@ -90,6 +92,7 @@ targets:
       ''') as YamlMap?;
       final SchedulerConfig unCheckedSchedulerConfig = SchedulerConfig()..mergeFromProto3Json(dependentTargetConfig);
       final SchedulerConfig schedulerConfig = CiYaml(
+        type: CiType.any,
         slug: Config.flutterSlug,
         branch: Config.defaultBranch(Config.flutterSlug),
         config: unCheckedSchedulerConfig,
@@ -121,6 +124,7 @@ targets:
       ''') as YamlMap?;
       final SchedulerConfig unCheckedSchedulerConfig = SchedulerConfig()..mergeFromProto3Json(twoDependentTargetConfig);
       final SchedulerConfig schedulerConfig = CiYaml(
+        type: CiType.any,
         slug: Config.flutterSlug,
         branch: Config.defaultBranch(Config.flutterSlug),
         config: unCheckedSchedulerConfig,
@@ -152,6 +156,7 @@ targets:
       final SchedulerConfig unCheckedSchedulerConfig = SchedulerConfig()..mergeFromProto3Json(configWithCycle);
       expect(
         () => CiYaml(
+          type: CiType.any,
           slug: Config.flutterSlug,
           branch: Config.defaultBranch(Config.flutterSlug),
           config: unCheckedSchedulerConfig,
@@ -179,6 +184,7 @@ targets:
         ..mergeFromProto3Json(configWithDuplicateTargets);
       expect(
         () => CiYaml(
+          type: CiType.any,
           slug: Config.flutterSlug,
           branch: Config.defaultBranch(Config.flutterSlug),
           config: unCheckedSchedulerConfig,
@@ -210,6 +216,7 @@ targets:
         ..mergeFromProto3Json(configWithMultipleDependencies);
       expect(
         () => CiYaml(
+          type: CiType.any,
           slug: Config.flutterSlug,
           branch: Config.defaultBranch(Config.flutterSlug),
           config: unCheckedSchedulerConfig,
@@ -237,6 +244,7 @@ targets:
       final SchedulerConfig unCheckedSchedulerConfig = SchedulerConfig()..mergeFromProto3Json(configWithMissingTarget);
       expect(
         () => CiYaml(
+          type: CiType.any,
           slug: Config.flutterSlug,
           branch: Config.defaultBranch(Config.flutterSlug),
           config: unCheckedSchedulerConfig,
@@ -265,6 +273,7 @@ targets:
       ''') as YamlMap?;
       final SchedulerConfig unCheckedSchedulerConfig = SchedulerConfig()..mergeFromProto3Json(totYaml);
       totConfig = CiYaml(
+        type: CiType.any,
         slug: Config.flutterSlug,
         branch: Config.defaultBranch(Config.flutterSlug),
         config: unCheckedSchedulerConfig,
@@ -282,6 +291,7 @@ targets:
       final SchedulerConfig unCheckedSchedulerConfig = SchedulerConfig()..mergeFromProto3Json(currentYaml);
       expect(
         () => CiYaml(
+          type: CiType.any,
           slug: Config.flutterSlug,
           branch: Config.defaultBranch(Config.flutterSlug),
           config: unCheckedSchedulerConfig,
@@ -304,6 +314,7 @@ targets:
       final SchedulerConfig unCheckedSchedulerConfig = SchedulerConfig()..mergeFromProto3Json(currentYaml);
       expect(
         () => CiYaml(
+          type: CiType.any,
           slug: Config.flutterSlug,
           branch: Config.defaultBranch(Config.flutterSlug),
           config: unCheckedSchedulerConfig,
@@ -325,6 +336,7 @@ targets:
       final SchedulerConfig unCheckedSchedulerConfig = SchedulerConfig()..mergeFromProto3Json(currentYaml);
       expect(
         () => CiYaml(
+          type: CiType.any,
           slug: Config.flutterSlug,
           branch: Config.defaultBranch(Config.flutterSlug),
           config: unCheckedSchedulerConfig,
@@ -353,6 +365,7 @@ targets:
       final SchedulerConfig unCheckedSchedulerConfig = SchedulerConfig()..mergeFromProto3Json(currentYaml);
       expect(
         () => CiYaml(
+          type: CiType.any,
           slug: Config.flutterSlug,
           branch: Config.defaultBranch(Config.flutterSlug),
           config: unCheckedSchedulerConfig,
diff --git a/app_dart/test/service/scheduler_test.dart b/app_dart/test/service/scheduler_test.dart
index be924b01d..7bb1b9da1 100644
--- a/app_dart/test/service/scheduler_test.dart
+++ b/app_dart/test/service/scheduler_test.dart
@@ -10,6 +10,7 @@ import 'package:cocoon_service/cocoon_service.dart';
 import 'package:cocoon_service/src/model/appengine/commit.dart';
 import 'package:cocoon_service/src/model/appengine/stage.dart';
 import 'package:cocoon_service/src/model/appengine/task.dart';
+import 'package:cocoon_service/src/model/ci_yaml/ci_yaml.dart';
 import 'package:cocoon_service/src/model/firestore/task.dart' as firestore;
 import 'package:cocoon_service/src/model/ci_yaml/target.dart';
 import 'package:cocoon_service/src/model/github/checks.dart' as cocoon_checks;
@@ -33,6 +34,7 @@ import '../src/datastore/fake_datastore.dart';
 import '../src/service/fake_build_bucket_client.dart';
 import '../src/service/fake_build_status_provider.dart';
 import '../src/request_handling/fake_pubsub.dart';
+import '../src/service/fake_fusion_tester.dart';
 import '../src/service/fake_gerrit_service.dart';
 import '../src/service/fake_github_service.dart';
 import '../src/service/fake_luci_build_service.dart';
@@ -62,6 +64,27 @@ targets:
     scheduler: google_internal
 ''';
 
+const String fusionCiYaml = r'''
+enabled_branches:
+  - master
+  - main
+  - codefu
+  - flutter-\d+\.\d+-candidate\.\d+
+targets:
+  - name: Linux Z
+    properties:
+      custom: abc
+  - name: Linux Y
+    enabled_branches:
+      - stable
+    scheduler: luci
+  - name: Linux runIf engine
+    runIf:
+      - DEPS
+      - engine/src/flutter/.ci.yaml
+      - engine/src/flutter/dev/**
+''';
+
 void main() {
   late CacheService cache;
   late FakeConfig config;
@@ -71,6 +94,7 @@ void main() {
   late MockFirestoreService mockFirestoreService;
   late MockGithubChecksUtil mockGithubChecksUtil;
   late Scheduler scheduler;
+  late FakeFusionTester fakeFusion;
 
   final PullRequest pullRequest = generatePullRequest(id: 42);
 
@@ -122,6 +146,8 @@ void main() {
       // Generate check runs based on the name hash code
       when(mockGithubChecksUtil.createCheckRun(any, any, any, any, output: anyNamed('output')))
           .thenAnswer((Invocation invocation) async => generateCheckRun(invocation.positionalArguments[2].hashCode));
+
+      fakeFusion = FakeFusionTester();
       scheduler = Scheduler(
         cache: cache,
         config: config,
@@ -136,6 +162,7 @@ void main() {
             branchesValue: <String>['master', 'main'],
           ),
         ),
+        fusionTester: fakeFusion,
       );
 
       when(mockGithubChecksUtil.createCheckRun(any, any, any, any)).thenAnswer((_) async {
@@ -147,6 +174,38 @@ void main() {
       });
     });
 
+    test('fusion, getPresubmitTargets supports two ci.yamls', () async {
+      httpClient = MockClient((http.Request request) async {
+        if (request.url.path.endsWith('engine/src/flutter/.ci.yaml')) {
+          return http.Response(fusionCiYaml, 200);
+        } else if (request.url.path.endsWith('.ci.yaml')) {
+          return http.Response(singleCiYaml, 200);
+        }
+        throw Exception('Failed to find ${request.url.path}');
+      });
+
+      fakeFusion.isFusion = (_, __) => true;
+
+      final List<Target> presubmitTargets = await scheduler.getPresubmitTargets(pullRequest);
+
+      expect(
+        [...presubmitTargets.map((Target target) => target.value.name)],
+        containsAll(<String>['Linux A']),
+      );
+      presubmitTargets
+        ..clear()
+        ..addAll(
+          await scheduler.getPresubmitTargets(
+            pullRequest,
+            type: CiType.fusionEngine,
+          ),
+        );
+      expect(
+        [...presubmitTargets.map((Target target) => target.value.name)],
+        containsAll(<String>['Linux Z']),
+      );
+    });
+
     group('add commits', () {
       final FakePubSub pubsub = FakePubSub();
       List<Commit> createCommitList(
@@ -288,6 +347,7 @@ void main() {
           githubChecksService: GithubChecksService(config, githubChecksUtil: mockGithubChecksUtil),
           httpClientProvider: () => httpClient,
           luciBuildService: luciBuildService,
+          fusionTester: fakeFusion,
         );
 
         await scheduler.addCommits(createCommitList(<String>['1'], repo: 'engine', branch: 'main'));
@@ -350,6 +410,7 @@ void main() {
           githubChecksService: GithubChecksService(config, githubChecksUtil: mockGithubChecksUtil),
           httpClientProvider: () => httpClient,
           luciBuildService: luciBuildService,
+          fusionTester: fakeFusion,
         );
 
         await scheduler.addCommits(createCommitList(<String>['1'], repo: 'engine', branch: 'main'));
@@ -478,6 +539,7 @@ targets:
               branchesValue: <String>['master', 'main'],
             ),
           ),
+          fusionTester: fakeFusion,
         );
 
         final PullRequest mergedPr = generatePullRequest(
@@ -558,6 +620,7 @@ targets:
             config: config,
             githubChecksUtil: mockGithubChecksUtil,
           ),
+          fusionTester: fakeFusion,
         );
         when(mockGithubService.github).thenReturn(mockGithubClient);
         when(mockGithubService.searchIssuesAndPRs(any, any, sort: anyNamed('sort'), pages: anyNamed('pages')))
@@ -634,6 +697,7 @@ targets:
             githubChecksUtil: mockGithubChecksUtil,
             buildBucketClient: mockBuildbucket,
           ),
+          fusionTester: fakeFusion,
         );
 
         final cocoon_checks.CheckRunEvent checkRunEvent = cocoon_checks.CheckRunEvent.fromJson(
@@ -736,6 +800,7 @@ targets:
           githubChecksService: GithubChecksService(config, githubChecksUtil: mockGithubChecksUtil),
           httpClientProvider: () => httpClient,
           luciBuildService: luciBuildService,
+          fusionTester: fakeFusion,
         );
         final cocoon_checks.CheckRunEvent checkRunEvent = cocoon_checks.CheckRunEvent.fromJson(
           jsonDecode(checkRunString) as Map<String, dynamic>,
@@ -1048,6 +1113,7 @@ targets:
               branchesValue: <String>['master', 'main'],
             ),
           ),
+          fusionTester: fakeFusion,
         );
         final PullRequest pr = generatePullRequest(
           repo: Config.engineSlug.name,
@@ -1084,6 +1150,7 @@ targets:
             githubChecksUtil: mockGithubChecksUtil,
             gerritService: FakeGerritService(branchesValue: <String>['master']),
           ),
+          fusionTester: fakeFusion,
         );
         await scheduler.triggerPresubmitTargets(pullRequest: pullRequest);
         expect(
@@ -1239,6 +1306,7 @@ targets:
             gerritService: FakeGerritService(branchesValue: <String>['master']),
             pubsub: pubsub,
           ),
+          fusionTester: fakeFusion,
         );
         when(mockBuildbucket.batch(any)).thenAnswer(
           (_) async => bbv2.BatchResponse(
@@ -1310,6 +1378,7 @@ targets:
             gerritService: FakeGerritService(branchesValue: <String>['master']),
             pubsub: pubsub,
           ),
+          fusionTester: fakeFusion,
         );
         when(mockBuildbucket.batch(any)).thenAnswer(
           (_) async => bbv2.BatchResponse(
diff --git a/app_dart/test/src/service/fake_scheduler.dart b/app_dart/test/src/service/fake_scheduler.dart
index 37aa5744c..8764d1a06 100644
--- a/app_dart/test/src/service/fake_scheduler.dart
+++ b/app_dart/test/src/service/fake_scheduler.dart
@@ -3,6 +3,7 @@
 // found in the LICENSE file.
 
 import 'package:cocoon_service/src/foundation/github_checks_util.dart';
+import 'package:cocoon_service/src/foundation/utils.dart';
 import 'package:cocoon_service/src/model/appengine/commit.dart';
 import 'package:cocoon_service/src/model/ci_yaml/ci_yaml.dart';
 import 'package:cocoon_service/src/model/proto/protos.dart' as pb;
@@ -16,6 +17,7 @@ import 'package:github/github.dart';
 import 'package:retry/retry.dart';
 
 import '../utilities/entity_generators.dart';
+import 'fake_fusion_tester.dart';
 import 'fake_luci_build_service.dart';
 
 /// Fake for [Scheduler] to use for tests that rely on it.
@@ -26,6 +28,7 @@ class FakeScheduler extends Scheduler {
     BuildBucketClient? buildbucket,
     required super.config,
     GithubChecksUtil? githubChecksUtil,
+    FusionTester? fusionTester,
   }) : super(
           cache: CacheService(inMemory: true),
           githubChecksService: GithubChecksService(
@@ -38,27 +41,29 @@ class FakeScheduler extends Scheduler {
                 buildBucketClient: buildbucket,
                 githubChecksUtil: githubChecksUtil,
               ),
+          fusionTester: fusionTester ?? FakeFusionTester(),
         );
 
-  final CiYaml _defaultConfig = emptyConfig;
+  final CiYamlSet _defaultConfig = emptyConfig;
 
-  /// [CiYaml] value to be injected on [getCiYaml].
-  CiYaml? ciYaml;
+  /// [CiYamlSet] value to be injected on [getCiYaml].
+  CiYamlSet? ciYaml;
 
   /// If true, getCiYaml will throw a [FormatException] when validation is
   /// enforced, simulating failing validation.
   bool failCiYamlValidation = false;
 
   @override
-  Future<CiYaml> getCiYaml(
+  Future<CiYamlSet> getCiYaml(
     Commit commit, {
-    CiYaml? totCiYaml,
+    CiYamlSet? totCiYaml,
     RetryOptions? retryOptions,
     bool validate = false,
   }) async {
     if (validate && failCiYamlValidation) {
       throw const FormatException('Failed validation!');
     }
+
     return ciYaml ?? _defaultConfig;
   }
 
@@ -117,224 +122,246 @@ class FakeScheduler extends Scheduler {
   }
 }
 
-final CiYaml emptyConfig = CiYaml(
+final emptyConfig = CiYamlSet(
   slug: Config.flutterSlug,
   branch: Config.defaultBranch(Config.flutterSlug),
-  config: pb.SchedulerConfig(
-    enabledBranches: <String>[
-      Config.defaultBranch(Config.flutterSlug),
-    ],
-    targets: <pb.Target>[
-      pb.Target(
-        name: 'Linux A',
-        scheduler: pb.SchedulerSystem.luci,
-      ),
-    ],
-  ),
+  yamls: {
+    CiType.any: pb.SchedulerConfig(
+      enabledBranches: <String>[
+        Config.defaultBranch(Config.flutterSlug),
+      ],
+      targets: <pb.Target>[
+        pb.Target(
+          name: 'Linux A',
+          scheduler: pb.SchedulerSystem.luci,
+        ),
+      ],
+    ),
+  },
 );
 
-CiYaml exampleConfig = CiYaml(
+final exampleConfig = CiYamlSet(
   slug: Config.flutterSlug,
   branch: Config.defaultBranch(Config.flutterSlug),
-  config: pb.SchedulerConfig(
-    enabledBranches: <String>[
-      Config.defaultBranch(Config.flutterSlug),
-    ],
-    targets: <pb.Target>[
-      pb.Target(
-        name: 'Linux A',
-        scheduler: pb.SchedulerSystem.luci,
-      ),
-      pb.Target(
-        name: 'Mac A',
-        scheduler: pb.SchedulerSystem.luci,
-      ),
-      pb.Target(
-        name: 'Windows A',
-        scheduler: pb.SchedulerSystem.luci,
-      ),
-      pb.Target(
-        name: 'Google Internal Roll',
-        presubmit: false,
-        postsubmit: true,
-        scheduler: pb.SchedulerSystem.google_internal,
-      ),
-    ],
-  ),
+  yamls: {
+    CiType.any: pb.SchedulerConfig(
+      enabledBranches: <String>[
+        Config.defaultBranch(Config.flutterSlug),
+      ],
+      targets: <pb.Target>[
+        pb.Target(
+          name: 'Linux A',
+          scheduler: pb.SchedulerSystem.luci,
+        ),
+        pb.Target(
+          name: 'Mac A',
+          scheduler: pb.SchedulerSystem.luci,
+        ),
+        pb.Target(
+          name: 'Windows A',
+          scheduler: pb.SchedulerSystem.luci,
+        ),
+        pb.Target(
+          name: 'Google Internal Roll',
+          presubmit: false,
+          postsubmit: true,
+          scheduler: pb.SchedulerSystem.google_internal,
+        ),
+      ],
+    ),
+  },
 );
 
-CiYaml exampleFlakyConfig = CiYaml(
+final exampleFlakyConfig = CiYamlSet(
   slug: Config.flutterSlug,
   branch: Config.defaultBranch(Config.flutterSlug),
-  config: pb.SchedulerConfig(
-    enabledBranches: <String>[
-      Config.defaultBranch(Config.flutterSlug),
-    ],
-    targets: <pb.Target>[
-      pb.Target(
-        name: 'Flaky 1',
-        scheduler: pb.SchedulerSystem.luci,
-        properties: {
-          'flakiness_threshold': '0.04',
-        },
-      ),
-      pb.Target(
-        name: 'Flaky Skip',
-        scheduler: pb.SchedulerSystem.luci,
-        properties: {
-          'ignore_flakiness': 'true',
-        },
-      ),
-    ],
-  ),
+  yamls: {
+    CiType.any: pb.SchedulerConfig(
+      enabledBranches: <String>[
+        Config.defaultBranch(Config.flutterSlug),
+      ],
+      targets: <pb.Target>[
+        pb.Target(
+          name: 'Flaky 1',
+          scheduler: pb.SchedulerSystem.luci,
+          properties: {
+            'flakiness_threshold': '0.04',
+          },
+        ),
+        pb.Target(
+          name: 'Flaky Skip',
+          scheduler: pb.SchedulerSystem.luci,
+          properties: {
+            'ignore_flakiness': 'true',
+          },
+        ),
+      ],
+    ),
+  },
 );
 
-CiYaml exampleBackfillConfig = CiYaml(
+final exampleBackfillConfig = CiYamlSet(
   slug: Config.flutterSlug,
   branch: Config.defaultBranch(Config.flutterSlug),
-  config: pb.SchedulerConfig(
-    enabledBranches: <String>[
-      Config.defaultBranch(Config.flutterSlug),
-    ],
-    targets: <pb.Target>[
-      pb.Target(
-        name: 'Linux A',
-        scheduler: pb.SchedulerSystem.luci,
-        postsubmit: true,
-        properties: {'backfill': 'true'},
-      ),
-      pb.Target(
-        name: 'Mac A',
-        scheduler: pb.SchedulerSystem.luci,
-        postsubmit: true,
-      ),
-      pb.Target(
-        name: 'Windows A',
-        scheduler: pb.SchedulerSystem.luci,
-        postsubmit: true,
-        properties: {'backfill': 'false'},
-      ),
-    ],
-  ),
+  yamls: {
+    CiType.any: pb.SchedulerConfig(
+      enabledBranches: <String>[
+        Config.defaultBranch(Config.flutterSlug),
+      ],
+      targets: <pb.Target>[
+        pb.Target(
+          name: 'Linux A',
+          scheduler: pb.SchedulerSystem.luci,
+          postsubmit: true,
+          properties: {'backfill': 'true'},
+        ),
+        pb.Target(
+          name: 'Mac A',
+          scheduler: pb.SchedulerSystem.luci,
+          postsubmit: true,
+        ),
+        pb.Target(
+          name: 'Windows A',
+          scheduler: pb.SchedulerSystem.luci,
+          postsubmit: true,
+          properties: {'backfill': 'false'},
+        ),
+      ],
+    ),
+  },
 );
 
-CiYaml examplePresubmitRescheduleConfig = CiYaml(
+final examplePresubmitRescheduleConfig = CiYamlSet(
   slug: Config.flutterSlug,
   branch: Config.defaultBranch(Config.flutterSlug),
-  config: pb.SchedulerConfig(
-    enabledBranches: <String>[
-      Config.defaultBranch(Config.flutterSlug),
-    ],
-    targets: <pb.Target>[
-      pb.Target(
-        name: 'Linux A',
-      ),
-      pb.Target(
-        name: 'Linux B',
-        postsubmit: true,
-        properties: {'presubmit_retry': '1'},
-      ),
-    ],
-  ),
+  yamls: {
+    CiType.any: pb.SchedulerConfig(
+      enabledBranches: <String>[
+        Config.defaultBranch(Config.flutterSlug),
+      ],
+      targets: <pb.Target>[
+        pb.Target(
+          name: 'Linux A',
+        ),
+        pb.Target(
+          name: 'Linux B',
+          postsubmit: true,
+          properties: {'presubmit_retry': '1'},
+        ),
+      ],
+    ),
+  },
 );
 
-final CiYaml batchPolicyConfig = CiYaml(
+final batchPolicyConfig = CiYamlSet(
   slug: Config.flutterSlug,
   branch: Config.defaultBranch(Config.flutterSlug),
-  config: pb.SchedulerConfig(
-    enabledBranches: <String>[
-      Config.defaultBranch(Config.flutterSlug),
-    ],
-    targets: <pb.Target>[
-      pb.Target(
-        name: 'Linux_android A',
-      ),
-      pb.Target(
-        name: 'Linux_android B',
-      ),
-      pb.Target(
-        name: 'Linux_android C',
-      ),
-    ],
-  ),
+  yamls: {
+    CiType.any: pb.SchedulerConfig(
+      enabledBranches: <String>[
+        Config.defaultBranch(Config.flutterSlug),
+      ],
+      targets: <pb.Target>[
+        pb.Target(
+          name: 'Linux_android A',
+        ),
+        pb.Target(
+          name: 'Linux_android B',
+        ),
+        pb.Target(
+          name: 'Linux_android C',
+        ),
+      ],
+    ),
+  },
 );
 
-final CiYaml unsupportedPostsubmitCheckrunConfig = CiYaml(
+final unsupportedPostsubmitCheckrunConfig = CiYamlSet(
   slug: Config.flutterSlug,
   branch: Config.defaultBranch(Config.flutterSlug),
-  config: pb.SchedulerConfig(
-    enabledBranches: <String>[
-      Config.defaultBranch(Config.flutterSlug),
-    ],
-    targets: <pb.Target>[
-      pb.Target(
-        name: 'Linux flutter',
-      ),
-    ],
-  ),
+  yamls: {
+    CiType.any: pb.SchedulerConfig(
+      enabledBranches: <String>[
+        Config.defaultBranch(Config.flutterSlug),
+      ],
+      targets: <pb.Target>[
+        pb.Target(
+          name: 'Linux flutter',
+        ),
+      ],
+    ),
+  },
 );
 
-final CiYaml nonBringupPackagesConfig = CiYaml(
+final nonBringupPackagesConfig = CiYamlSet(
   slug: Config.packagesSlug,
   branch: Config.defaultBranch(Config.packagesSlug),
-  config: pb.SchedulerConfig(
-    enabledBranches: <String>[
-      Config.defaultBranch(Config.packagesSlug),
-    ],
-    targets: <pb.Target>[
-      pb.Target(
-        name: 'Linux nonbringup',
-      ),
-    ],
-  ),
+  yamls: {
+    CiType.any: pb.SchedulerConfig(
+      enabledBranches: <String>[
+        Config.defaultBranch(Config.packagesSlug),
+      ],
+      targets: <pb.Target>[
+        pb.Target(
+          name: 'Linux nonbringup',
+        ),
+      ],
+    ),
+  },
 );
 
-final CiYaml bringupPackagesConfig = CiYaml(
+final bringupPackagesConfig = CiYamlSet(
   slug: Config.packagesSlug,
   branch: Config.defaultBranch(Config.packagesSlug),
-  config: pb.SchedulerConfig(
-    enabledBranches: <String>[
-      Config.defaultBranch(Config.packagesSlug),
-    ],
-    targets: <pb.Target>[
-      pb.Target(
-        name: 'Linux bringup',
-        bringup: true,
-      ),
-    ],
-  ),
+  yamls: {
+    CiType.any: pb.SchedulerConfig(
+      enabledBranches: <String>[
+        Config.defaultBranch(Config.packagesSlug),
+      ],
+      targets: <pb.Target>[
+        pb.Target(
+          name: 'Linux bringup',
+          bringup: true,
+        ),
+      ],
+    ),
+  },
 );
 
-final CiYaml totCiYaml = CiYaml(
+final totCiYaml = CiYamlSet(
   slug: Config.flutterSlug,
   branch: Config.defaultBranch(Config.flutterSlug),
-  config: pb.SchedulerConfig(
-    enabledBranches: <String>[
-      Config.defaultBranch(Config.flutterSlug),
-    ],
-    targets: <pb.Target>[
-      pb.Target(
-        name: 'Linux_android B',
-      ),
-      pb.Target(
-        name: 'Linux_android C',
-      ),
-    ],
-  ),
+  yamls: {
+    CiType.any: pb.SchedulerConfig(
+      enabledBranches: <String>[
+        Config.defaultBranch(Config.flutterSlug),
+      ],
+      targets: <pb.Target>[
+        pb.Target(
+          name: 'Linux_android B',
+        ),
+        pb.Target(
+          name: 'Linux_android C',
+        ),
+      ],
+    ),
+  },
 );
 
-final CiYaml notInToTConfig = CiYaml(
+final notInToTConfig = CiYamlSet(
   slug: Config.flutterSlug,
   branch: Config.defaultBranch(Config.flutterSlug),
-  config: pb.SchedulerConfig(
-    enabledBranches: <String>[
-      Config.defaultBranch(Config.flutterSlug),
-    ],
-    targets: <pb.Target>[
-      pb.Target(
-        name: 'Linux_android A',
-      ),
-    ],
-  ),
+  yamls: {
+    CiType.any: pb.SchedulerConfig(
+      enabledBranches: <String>[
+        Config.defaultBranch(Config.flutterSlug),
+      ],
+      targets: <pb.Target>[
+        pb.Target(
+          name: 'Linux_android A',
+        ),
+      ],
+    ),
+  },
   totConfig: totCiYaml,
 );
diff --git a/app_dart/test/src/utilities/entity_generators.dart b/app_dart/test/src/utilities/entity_generators.dart
index ffffacf0a..8f5645133 100644
--- a/app_dart/test/src/utilities/entity_generators.dart
+++ b/app_dart/test/src/utilities/entity_generators.dart
@@ -10,7 +10,6 @@ import 'package:cocoon_service/src/model/firestore/commit.dart' as firestore_com
 import 'package:cocoon_service/src/model/firestore/github_build_status.dart';
 import 'package:cocoon_service/src/model/firestore/github_gold_status.dart';
 import 'package:cocoon_service/src/model/firestore/task.dart' as firestore;
-import 'package:cocoon_service/src/model/ci_yaml/target.dart';
 import 'package:cocoon_service/src/model/gerrit/commit.dart';
 import 'package:cocoon_service/src/model/proto/protos.dart' as pb;
 import 'package:fixnum/fixnum.dart';
@@ -220,7 +219,7 @@ Target generateTarget(
   pb.SchedulerSystem? schedulerSystem,
   String recipe = 'devicelab/devicelab',
 }) {
-  final pb.SchedulerConfig config = schedulerConfig ?? exampleConfig.config;
+  final pb.SchedulerConfig config = schedulerConfig ?? exampleConfig.configFor(CiType.any);
   if (platformProperties != null && platformDimensions != null) {
     config.platformProperties[platform.toLowerCase()] =
         pb.SchedulerConfig_PlatformProperties(properties: platformProperties, dimensions: platformDimensions);