diff --git a/app_dart/lib/src/model/bbv2_extension.dart b/app_dart/lib/src/model/bbv2_extension.dart
index f3ac928a5..4201de5ad 100644
--- a/app_dart/lib/src/model/bbv2_extension.dart
+++ b/app_dart/lib/src/model/bbv2_extension.dart
@@ -2,21 +2,28 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
-import 'package:buildbucket/buildbucket_pb.dart' as bbv2;
+import 'package:buildbucket/buildbucket_pb.dart' as bb;
 import 'package:cocoon_common/task_status.dart';
 
-extension StatusExtension on bbv2.Status {
-  /// Converts from a [bbv2.Status] to a [TaskStatus].
+extension StatusExtension on bb.Status {
+  /// Converts from a [bb.Status] to a [TaskStatus].
   ///
   /// An unrecognized status is disallowed.
   TaskStatus toTaskStatus() {
     return switch (this) {
-      bbv2.Status.SCHEDULED || bbv2.Status.STARTED => TaskStatus.inProgress,
-      bbv2.Status.SUCCESS => TaskStatus.succeeded,
-      bbv2.Status.CANCELED => TaskStatus.cancelled,
-      bbv2.Status.INFRA_FAILURE => TaskStatus.infraFailure,
-      bbv2.Status.FAILURE => TaskStatus.failed,
+      bb.Status.SCHEDULED || bb.Status.STARTED => TaskStatus.inProgress,
+      bb.Status.SUCCESS => TaskStatus.succeeded,
+      bb.Status.CANCELED => TaskStatus.cancelled,
+      bb.Status.INFRA_FAILURE => TaskStatus.infraFailure,
+      bb.Status.FAILURE => TaskStatus.failed,
       _ => throw StateError('Unexpected status: $this'),
     };
   }
 }
+
+extension TaskFailedExtension on bb.Status {
+  bool isTaskFailed() => switch (this) {
+    bb.Status.FAILURE || bb.Status.CANCELED || bb.Status.INFRA_FAILURE => true,
+    _ => false,
+  };
+}
diff --git a/app_dart/lib/src/model/common/presubmit_guard_conclusion.dart b/app_dart/lib/src/model/common/presubmit_guard_conclusion.dart
index fe14c82b3..2adf49fa4 100644
--- a/app_dart/lib/src/model/common/presubmit_guard_conclusion.dart
+++ b/app_dart/lib/src/model/common/presubmit_guard_conclusion.dart
@@ -38,7 +38,7 @@ enum PresubmitGuardConclusionResult {
 class PresubmitGuardConclusion {
   final PresubmitGuardConclusionResult result;
   final int remaining;
-  final int? checkRunId;
+  final String checkRunJson;
   final int failed;
   final String summary;
   final String details;
@@ -46,7 +46,7 @@ class PresubmitGuardConclusion {
   const PresubmitGuardConclusion({
     required this.result,
     required this.remaining,
-    required this.checkRunId,
+    required this.checkRunJson,
     required this.failed,
     required this.summary,
     required this.details,
@@ -66,16 +66,22 @@ class PresubmitGuardConclusion {
       (other is PresubmitGuardConclusion &&
           other.result == result &&
           other.remaining == remaining &&
-          other.checkRunId == checkRunId &&
+          other.checkRunJson == checkRunJson &&
           other.failed == failed &&
           other.summary == summary &&
           other.details == details);
 
   @override
-  int get hashCode =>
-      Object.hashAll([result, remaining, checkRunId, failed, summary, details]);
+  int get hashCode => Object.hashAll([
+    result,
+    remaining,
+    checkRunJson,
+    failed,
+    summary,
+    details,
+  ]);
 
   @override
   String toString() =>
-      'BuildConclusion("$result", "$remaining", "$checkRunId", "$failed", "$summary", "$details")';
+      'BuildConclusion("$result", "$remaining", "$failed", "$summary", "$details", "$checkRunJson")';
 }
diff --git a/app_dart/lib/src/model/firestore/presubmit_guard.dart b/app_dart/lib/src/model/firestore/presubmit_guard.dart
index c94cae042..5514afefd 100644
--- a/app_dart/lib/src/model/firestore/presubmit_guard.dart
+++ b/app_dart/lib/src/model/firestore/presubmit_guard.dart
@@ -185,9 +185,15 @@ final class PresubmitGuard extends AppDocument<PresubmitGuard> {
   CheckRun get checkRun {
     final jsonData =
         jsonDecode(fields[fieldCheckRun]!.stringValue!) as Map<String, Object?>;
+    // Workaround for https://github.com/SpinlockLabs/github.dart/issues/412
+    if (jsonData['conclusion'] == 'null') {
+      jsonData.remove('conclusion');
+    }
     return CheckRun.fromJson(jsonData);
   }
 
+  String get checkRunJson => fields[fieldCheckRun]!.stringValue!;
+
   /// The repository that this stage is recorded for.
   RepositorySlug get slug {
     // Read it from the document name.
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 941b95f92..3fb17f78b 100644
--- a/app_dart/lib/src/request_handlers/presubmit_luci_subscription.dart
+++ b/app_dart/lib/src/request_handlers/presubmit_luci_subscription.dart
@@ -9,6 +9,7 @@ import 'package:buildbucket/buildbucket_pb.dart' as bbv2;
 import 'package:cocoon_server/logging.dart';
 import 'package:github/github.dart';
 
+import '../model/bbv2_extension.dart';
 import '../model/ci_yaml/ci_yaml.dart';
 import '../model/ci_yaml/target.dart';
 import '../model/commit_ref.dart';
@@ -102,65 +103,70 @@ final class PresubmitLuciSubscription extends SubscriptionHandler {
 
     final userData = PresubmitUserData.fromBytes(pubSubCallBack.userData);
     var rescheduled = false;
-    if (_githubChecksService.taskFailed(build.status)) {
-      final currentAttempt = _nextAttempt(tagSet);
+    if (build.status.isTaskFailed()) {
+      // if failed summary stored in github check run and unified check run.
+      build.summaryMarkdown = (await _luciBuildService.getBuildById(
+        build.id,
+        buildMask: bbv2.BuildMask(
+          // Need to use allFields as there is a bug with fieldMask and summaryMarkdown.
+          allFields: true,
+        ),
+      )).summaryMarkdown;
       final maxAttempt = await _getMaxAttempt(
         userData.commit,
         builderName,
         tagSet,
       );
-      if (currentAttempt < maxAttempt) {
+      if (tagSet.currentAttempt < maxAttempt) {
         rescheduled = true;
         log.info('Rerunning failed task: $builderName');
         await _luciBuildService.reschedulePresubmitBuild(
           builderName: builderName,
           build: build,
-          nextAttempt: currentAttempt + 1,
+          nextAttempt: tagSet.currentAttempt + 1,
           userData: userData,
         );
       }
     }
-    await _githubChecksService.updateCheckStatus(
-      checkRunId: userData.checkRunId,
-      build: build,
-      luciBuildService: _luciBuildService,
-      slug: userData.commit.slug,
-      rescheduled: rescheduled,
-    );
+    if (userData.checkRunId != null) {
+      await _githubChecksService.updateCheckStatus(
+        checkRunId: userData.checkRunId!,
+        build: build,
+        luciBuildService: _luciBuildService,
+        slug: userData.commit.slug,
+        rescheduled: rescheduled,
+      );
 
-    if (!rescheduled && config.flags.closeMqGuardAfterPresubmit) {
-      // Process to the check-run status in the merge queue document during
-      // the LUCI callback.
-      final conclusion = _githubChecksService.conclusionForResult(build.status);
-      await _scheduler.processCheckRunCompleted(
-        cocoon_checks.CheckRun(
-          id: userData.checkRunId,
-          name: builderName,
-          headSha: userData.commit.sha,
-          conclusion: '$conclusion',
-          checkSuite: CheckSuite(
-            id: userData.checkSuiteId,
-            headBranch: userData.commit.branch,
+      if (!rescheduled && config.flags.closeMqGuardAfterPresubmit) {
+        // Process to the check-run status in the merge queue document during
+        // the LUCI callback.
+        final conclusion = _githubChecksService.conclusionForResult(
+          build.status,
+        );
+        await _scheduler.processCheckRunCompleted(
+          cocoon_checks.CheckRun(
+            id: userData.checkRunId,
+            name: builderName,
             headSha: userData.commit.sha,
-            conclusion: conclusion,
-            pullRequests: [],
+            conclusion: '$conclusion',
+            checkSuite: CheckSuite(
+              id: userData.checkSuiteId,
+              headBranch: userData.commit.branch,
+              headSha: userData.commit.sha,
+              conclusion: conclusion,
+              pullRequests: [],
+            ),
           ),
-        ),
-        userData.commit.slug,
-      );
+          userData.commit.slug,
+        );
+      }
+    } else if (!rescheduled) {
+      await _scheduler.processUnifiedCheckRunCompleted(build, userData);
     }
 
     return Response.emptyOk;
   }
 
-  /// Returns the current reschedule attempt.
-  ///
-  /// It returns 1 if this is the first run.
-  static int _nextAttempt(BuildTags buildTags) {
-    final attempt = buildTags.getTagOfType<CurrentAttemptBuildTag>();
-    return attempt?.attemptNumber ?? 1;
-  }
-
   Future<int> _getMaxAttempt(
     CommitRef commit,
     String builderName,
diff --git a/app_dart/lib/src/service/firestore/unified_check_run.dart b/app_dart/lib/src/service/firestore/unified_check_run.dart
index 981febb6d..044a93a0b 100644
--- a/app_dart/lib/src/service/firestore/unified_check_run.dart
+++ b/app_dart/lib/src/service/firestore/unified_check_run.dart
@@ -249,7 +249,7 @@ final class UnifiedCheckRun {
         return PresubmitGuardConclusion(
           result: PresubmitGuardConclusionResult.missing,
           remaining: presubmitGuard.remainingBuilds ?? -1,
-          checkRunId: guardId.checkRunId,
+          checkRunJson: presubmitGuard.checkRunJson,
           failed: presubmitGuard.failedBuilds ?? -1,
           summary:
               'Check run "${state.buildName}" not present in ${guardId.stage} CI stage',
@@ -336,7 +336,7 @@ final class UnifiedCheckRun {
         return PresubmitGuardConclusion(
           result: PresubmitGuardConclusionResult.internalError,
           remaining: -1,
-          checkRunId: null,
+          checkRunJson: '',
           failed: failed,
           summary: 'Internal server error',
           details:
@@ -371,7 +371,7 @@ $stack
             ? PresubmitGuardConclusionResult.ok
             : PresubmitGuardConclusionResult.internalError,
         remaining: remaining,
-        checkRunId: guardId.checkRunId,
+        checkRunJson: presubmitGuard.checkRunJson,
         failed: failed,
         summary: valid
             ? 'Successfully updated presubmit guard status'
diff --git a/app_dart/lib/src/service/github_checks_service.dart b/app_dart/lib/src/service/github_checks_service.dart
index 06bc505bd..52147996b 100644
--- a/app_dart/lib/src/service/github_checks_service.dart
+++ b/app_dart/lib/src/service/github_checks_service.dart
@@ -7,6 +7,7 @@ import 'package:cocoon_server/logging.dart';
 import 'package:github/github.dart' as github;
 
 import '../foundation/github_checks_util.dart';
+import '../model/bbv2_extension.dart';
 import 'config.dart';
 import 'luci_build_service.dart';
 
@@ -72,7 +73,7 @@ class GithubChecksService {
     final url = 'https://cr-buildbucket.appspot.com/build/${build.id}';
     github.CheckRunOutput? output;
     // If status has completed with failure then provide more details.
-    if (taskFailed(build.status)) {
+    if (build.status.isTaskFailed()) {
       log.info(
         'failed presubmit task, ${build.id} has failed, status = ${build.status.toString()}',
       );
@@ -114,14 +115,6 @@ class GithubChecksService {
     return true;
   }
 
-  /// Check if task has completed with failure.
-  bool taskFailed(bbv2.Status status) {
-    final checkRunStatus = statusForResult(status);
-    final conclusion = conclusionForResult(status);
-    return (checkRunStatus == github.CheckRunStatus.completed) &&
-        failedStatesSet.contains(conclusion);
-  }
-
   /// Appends triage wiki page to `summaryMarkdown` from LUCI build so that people can easily
   /// reference from github check run page.
   String getGithubSummary(String? summary) {
diff --git a/app_dart/lib/src/service/luci_build_service.dart b/app_dart/lib/src/service/luci_build_service.dart
index 99c1d28ad..94f7bbd23 100644
--- a/app_dart/lib/src/service/luci_build_service.dart
+++ b/app_dart/lib/src/service/luci_build_service.dart
@@ -11,7 +11,6 @@ import 'package:cocoon_common/is_release_branch.dart';
 import 'package:cocoon_common/task_status.dart';
 import 'package:cocoon_server/logging.dart';
 import 'package:fixnum/fixnum.dart';
-import 'package:github/github.dart' as github;
 import 'package:github/github.dart';
 import 'package:googleapis/firestore/v1.dart' hide Status;
 import 'package:meta/meta.dart';
@@ -20,6 +19,7 @@ import '../../cocoon_service.dart';
 import '../foundation/github_checks_util.dart';
 import '../model/ci_yaml/target.dart';
 import '../model/commit_ref.dart';
+import '../model/firestore/base.dart';
 import '../model/firestore/pr_check_runs.dart' as fs;
 import '../model/firestore/task.dart' as fs;
 import '../model/github/checks.dart' as cocoon_checks;
@@ -98,7 +98,7 @@ class LuciBuildService {
   ///
   /// Returns a list of BuildBucket [Build]s for a given Github [PullRequest].
   Future<Iterable<bbv2.Build>> getTryBuildsByPullRequest({
-    required github.PullRequest pullRequest,
+    required PullRequest pullRequest,
   }) async {
     final slug = pullRequest.base!.repo!.slug();
     return _getBuilds(
@@ -226,8 +226,10 @@ class LuciBuildService {
   /// framework tests, provide [EngineArtifacts.noFrameworkTests].
   Future<List<Target>> scheduleTryBuilds({
     required List<Target> targets,
-    required github.PullRequest pullRequest,
+    required PullRequest pullRequest,
     required EngineArtifacts engineArtifacts,
+    CheckRun? checkRunGuard,
+    CiStage? stage,
   }) async {
     if (targets.isEmpty) {
       return targets;
@@ -235,30 +237,51 @@ class LuciBuildService {
 
     final batchRequestList = <bbv2.BatchRequest_Request>[];
     final commitSha = pullRequest.head!.sha!;
-    final isFusion = pullRequest.base!.repo!.slug() == Config.flutterSlug;
+    final slug = pullRequest.base!.repo!.slug();
+    final commitBranch = pullRequest.base!.ref!.replaceAll('refs/heads/', '');
+    final isFusion = slug == Config.flutterSlug;
+    final isUnifiedCheckRunFlow = _config.flags
+        .isUnifiedCheckRunFlowEnabledForUser(pullRequest.user!.login!);
     final cipdVersion = await _getAndCheckRecipeVersion(
       slug: pullRequest.base!.repo!.slug(),
       branch: pullRequest.base!.ref!,
     );
 
-    final checkRuns = <github.CheckRun>[];
-    for (var target in targets) {
-      final checkRun = await _githubChecksUtil.createCheckRun(
-        _config,
-        target.slug,
-        commitSha,
-        target.name,
-      );
-      checkRuns.add(checkRun);
-
-      final slug = pullRequest.base!.repo!.slug();
-      final commitBranch = pullRequest.base!.ref!.replaceAll('refs/heads/', '');
-      final userData = PresubmitUserData(
+    final checkRuns = <CheckRun>[];
+    late PresubmitUserData userData;
+    // If the unified check run flow is enabled, do not create individual
+    // check runs for each target but use the guard check run instead.
+    if (isUnifiedCheckRunFlow && checkRunGuard != null) {
+      userData = PresubmitUserData(
         commit: CommitRef(slug: slug, sha: commitSha, branch: commitBranch),
-        checkRunId: checkRun.id!,
-        checkSuiteId: checkRun.checkSuiteId!,
+        guardCheckRunId: checkRunGuard.id!,
+        checkSuiteId: checkRunGuard.checkSuiteId,
+        pullRequestNumber: pullRequest.number!,
+        stage: stage,
       );
+      // We need to store PR to checkrun mapping in order to get PR later in
+      // [Scheduler.proceedUnifiedCheckRunToTestingStage] method
+      checkRuns.add(checkRunGuard);
+    }
 
+    for (var target in targets) {
+      // If the unified check run flow is disabled create individual check runs
+      // for each target.
+      if (!isUnifiedCheckRunFlow || checkRunGuard == null) {
+        final checkRun = await _githubChecksUtil.createCheckRun(
+          _config,
+          target.slug,
+          commitSha,
+          target.name,
+        );
+        checkRuns.add(checkRun);
+
+        userData = PresubmitUserData(
+          commit: CommitRef(slug: slug, sha: commitSha, branch: commitBranch),
+          checkRunId: checkRun.id,
+          checkSuiteId: checkRun.checkSuiteId,
+        );
+      }
       final properties = target.getProperties();
       properties.putIfAbsent('git_branch', () => commitBranch);
 
@@ -314,9 +337,14 @@ class LuciBuildService {
             cipdVersion: cipdVersion,
             userData: userData,
             properties: properties,
-            tags: BuildTags([
-              GitHubCheckRunIdBuildTag(checkRunId: checkRun.id!),
-            ]),
+            // if unified check run flow is enabled, use guard check run othervise check run id.
+            tags: isUnifiedCheckRunFlow && checkRunGuard != null
+                ? BuildTags([
+                    GuardCheckRunIdBuildTag(guardCheckRunId: checkRunGuard.id!),
+                  ])
+                : BuildTags([
+                    GitHubCheckRunIdBuildTag(checkRunId: userData.checkRunId!),
+                  ]),
             dimensions: requestedDimensions,
           ),
         ),
@@ -356,7 +384,7 @@ class LuciBuildService {
 
   /// Cancels all the current builds on [pullRequest] with [reason].
   Future<void> cancelBuilds({
-    required github.PullRequest pullRequest,
+    required PullRequest pullRequest,
     required String reason,
   }) async {
     log.info(
@@ -472,7 +500,7 @@ class LuciBuildService {
   ///
   /// Returns a [List] of prefixed label names as [String]s.
   static List<String>? _extractPrefixedLabels({
-    List<github.IssueLabel>? issueLabels,
+    List<IssueLabel>? issueLabels,
     required String prefix,
   }) {
     return issueLabels
@@ -744,7 +772,7 @@ class LuciBuildService {
   /// Create a Presubmit ScheduleBuildRequest using the [slug], [sha], and
   /// [checkName] for the provided [build] with the provided [checkRunId].
   bbv2.ScheduleBuildRequest _createPresubmitScheduleBuild({
-    required github.RepositorySlug slug,
+    required RepositorySlug slug,
     required String sha,
     required String checkName,
     required int pullRequestNumber,
diff --git a/app_dart/lib/src/service/luci_build_service/build_tags.dart b/app_dart/lib/src/service/luci_build_service/build_tags.dart
index e472f6544..ed9b43f47 100644
--- a/app_dart/lib/src/service/luci_build_service/build_tags.dart
+++ b/app_dart/lib/src/service/luci_build_service/build_tags.dart
@@ -337,11 +337,11 @@ final class GitHubCheckRunIdBuildTag extends BuildTag {
 /// A link back to the GitHub checkRun for this build.
 final class GuardCheckRunIdBuildTag extends BuildTag {
   static const _keyName = 'guard_checkrun';
-  GuardCheckRunIdBuildTag({required this.checkRunId})
-    : super(_keyName, '$checkRunId');
+  GuardCheckRunIdBuildTag({required this.guardCheckRunId})
+    : super(_keyName, '$guardCheckRunId');
 
   /// ID of the checkRun.
-  final int checkRunId;
+  final int guardCheckRunId;
 }
 
 /// A build tag that specifies the ID of the scheduling job.
diff --git a/app_dart/lib/src/service/luci_build_service/user_data.dart b/app_dart/lib/src/service/luci_build_service/user_data.dart
index a4a74172b..f432f024a 100644
--- a/app_dart/lib/src/service/luci_build_service/user_data.dart
+++ b/app_dart/lib/src/service/luci_build_service/user_data.dart
@@ -11,6 +11,7 @@ import 'package:json_annotation/json_annotation.dart';
 import 'package:meta/meta.dart';
 
 import '../../model/commit_ref.dart';
+import '../../model/firestore/base.dart';
 import '../../model/firestore/task.dart';
 
 part 'user_data.g.dart';
@@ -65,8 +66,11 @@ abstract final class PresubmitUserData extends BuildBucketUserData {
   /// [checkRunId] and [checkSuiteId].
   factory PresubmitUserData({
     required CommitRef commit,
-    required int checkRunId,
-    required int checkSuiteId,
+    int? checkRunId,
+    int? checkSuiteId,
+    int? guardCheckRunId,
+    int? pullRequestNumber,
+    CiStage? stage,
   }) {
     return _PresubmitUserData(
       repoOwner: commit.slug.owner,
@@ -75,6 +79,9 @@ abstract final class PresubmitUserData extends BuildBucketUserData {
       commitSha: commit.sha,
       checkRunId: checkRunId,
       checkSuiteId: checkSuiteId,
+      guardCheckRunId: guardCheckRunId,
+      pullRequestNumber: pullRequestNumber,
+      stage: stage,
     );
   }
 
@@ -102,45 +109,64 @@ abstract final class PresubmitUserData extends BuildBucketUserData {
   CommitRef get commit;
 
   /// Which GitHub check run this build reports status to.
-  int get checkRunId;
+  int? get checkRunId;
 
-  int get checkSuiteId;
+  /// The check suite ID to which check run belongs.
+  int? get checkSuiteId;
+
+  /// The check run ID of the MQ guard build associated with this presubmit.
+  /// Used for Unified check runs.
+  int? get guardCheckRunId;
+
+  /// The pull request number associated with this presubmit.
+  /// Used for Unified check runs.
+  int? get pullRequestNumber;
+
+  /// The CI stage associated with this presubmit.
+  /// Used for Unified check runs.
+  CiStage? get stage;
 }
 
-@JsonSerializable(checked: true)
+@JsonSerializable(checked: true, fieldRename: FieldRename.snake)
 final class _PresubmitUserData extends PresubmitUserData {
   const _PresubmitUserData({
     required this.repoOwner,
     required this.repoName,
     required this.commitBranch,
     required this.commitSha,
-    required this.checkRunId,
-    required this.checkSuiteId,
+    this.checkRunId,
+    this.checkSuiteId,
+    this.guardCheckRunId,
+    this.pullRequestNumber,
+    this.stage,
   }) : super._();
 
   /// The owner of the GitHub repo, i.e. `flutter` or `matanlurey`.
-  @JsonKey(name: 'repo_owner')
   final String repoOwner;
 
   /// The name of the GitHub repo, i.e. `flutter` or `packages`.
-  @JsonKey(name: 'repo_name')
   final String repoName;
 
   /// The branch the [commitSha] is on.
-  @JsonKey(name: 'commit_branch')
   final String commitBranch;
 
   /// The commit SHA being built at.
-  @JsonKey(name: 'commit_sha')
   final String commitSha;
 
-  @JsonKey(name: 'check_run_id')
   @override
-  final int checkRunId;
+  final int? checkRunId;
+
+  @override
+  final int? checkSuiteId;
+
+  @override
+  final int? guardCheckRunId;
+
+  @override
+  final int? pullRequestNumber;
 
-  @JsonKey(name: 'check_suite_id', defaultValue: 0)
   @override
-  final int checkSuiteId;
+  final CiStage? stage;
 
   @override
   CommitRef get commit {
@@ -156,7 +182,11 @@ final class _PresubmitUserData extends PresubmitUserData {
 }
 
 /// Represents the data passed to Buildbucket as part of a postsubmit build.
-@JsonSerializable(checked: true, includeIfNull: false)
+@JsonSerializable(
+  checked: true,
+  includeIfNull: false,
+  fieldRename: FieldRename.snake,
+)
 final class PostsubmitUserData extends BuildBucketUserData {
   PostsubmitUserData({required this.checkRunId, required this.taskId});
 
@@ -183,11 +213,10 @@ final class PostsubmitUserData extends BuildBucketUserData {
   /// Which GitHub check run this build reports status to.
   ///
   /// If this postsubmit is marked bringup (`bringup: true`) there is no associated ID.
-  @JsonKey(name: 'check_run_id', includeIfNull: false)
   final int? checkRunId;
 
   /// The firestore task document name storing results of this build.
-  @JsonKey(name: 'task_id', fromJson: TaskId.parse, toJson: _documentToString)
+  @JsonKey(fromJson: TaskId.parse, toJson: _documentToString)
   final TaskId taskId;
   static String _documentToString(TaskId firestoreTask) {
     return firestoreTask.documentId;
diff --git a/app_dart/lib/src/service/luci_build_service/user_data.g.dart b/app_dart/lib/src/service/luci_build_service/user_data.g.dart
index a670aec1b..c6f4412f5 100644
--- a/app_dart/lib/src/service/luci_build_service/user_data.g.dart
+++ b/app_dart/lib/src/service/luci_build_service/user_data.g.dart
@@ -20,11 +20,23 @@ _PresubmitUserData _$PresubmitUserDataFromJson(Map<String, dynamic> json) =>
           commitSha: $checkedConvert('commit_sha', (v) => v as String),
           checkRunId: $checkedConvert(
             'check_run_id',
-            (v) => (v as num).toInt(),
+            (v) => (v as num?)?.toInt(),
           ),
           checkSuiteId: $checkedConvert(
             'check_suite_id',
-            (v) => (v as num?)?.toInt() ?? 0,
+            (v) => (v as num?)?.toInt(),
+          ),
+          guardCheckRunId: $checkedConvert(
+            'guard_check_run_id',
+            (v) => (v as num?)?.toInt(),
+          ),
+          pullRequestNumber: $checkedConvert(
+            'pull_request_number',
+            (v) => (v as num?)?.toInt(),
+          ),
+          stage: $checkedConvert(
+            'stage',
+            (v) => $enumDecodeNullable(_$CiStageEnumMap, v),
           ),
         );
         return val;
@@ -36,6 +48,8 @@ _PresubmitUserData _$PresubmitUserDataFromJson(Map<String, dynamic> json) =>
         'commitSha': 'commit_sha',
         'checkRunId': 'check_run_id',
         'checkSuiteId': 'check_suite_id',
+        'guardCheckRunId': 'guard_check_run_id',
+        'pullRequestNumber': 'pull_request_number',
       },
     );
 
@@ -47,8 +61,16 @@ Map<String, dynamic> _$PresubmitUserDataToJson(_PresubmitUserData instance) =>
       'commit_sha': instance.commitSha,
       'check_run_id': instance.checkRunId,
       'check_suite_id': instance.checkSuiteId,
+      'guard_check_run_id': instance.guardCheckRunId,
+      'pull_request_number': instance.pullRequestNumber,
+      'stage': _$CiStageEnumMap[instance.stage],
     };
 
+const _$CiStageEnumMap = {
+  CiStage.fusionEngineBuild: 'fusionEngineBuild',
+  CiStage.fusionTests: 'fusionTests',
+};
+
 PostsubmitUserData _$PostsubmitUserDataFromJson(Map<String, dynamic> json) =>
     $checkedCreate(
       'PostsubmitUserData',
diff --git a/app_dart/lib/src/service/scheduler.dart b/app_dart/lib/src/service/scheduler.dart
index 9acbb720a..c57539073 100644
--- a/app_dart/lib/src/service/scheduler.dart
+++ b/app_dart/lib/src/service/scheduler.dart
@@ -6,6 +6,7 @@ import 'dart:convert';
 import 'dart:io';
 import 'dart:math';
 
+import 'package:buildbucket/buildbucket_pb.dart' as bbv2;
 import 'package:cocoon_common/task_status.dart';
 import 'package:cocoon_server/logging.dart';
 import 'package:collection/collection.dart';
@@ -17,13 +18,17 @@ import 'package:meta/meta.dart';
 import 'package:retry/retry.dart';
 
 import '../foundation/utils.dart';
+import '../model/bbv2_extension.dart';
 import '../model/ci_yaml/ci_yaml.dart';
 import '../model/ci_yaml/target.dart';
 import '../model/commit_ref.dart';
+import '../model/common/presubmit_check_state.dart';
+import '../model/common/presubmit_guard_conclusion.dart';
 import '../model/firestore/base.dart';
 import '../model/firestore/ci_staging.dart';
 import '../model/firestore/commit.dart' as fs;
 import '../model/firestore/pr_check_runs.dart';
+import '../model/firestore/presubmit_guard.dart';
 import '../model/firestore/task.dart' as fs;
 import '../model/github/checks.dart' as cocoon_checks;
 import '../model/github/checks.dart' show MergeGroup;
@@ -35,11 +40,14 @@ import 'config.dart';
 import 'content_aware_hash_service.dart';
 import 'exceptions.dart';
 import 'firestore.dart';
+import 'firestore/unified_check_run.dart';
 import 'get_files_changed.dart';
 import 'github_checks_service.dart';
 import 'luci_build_service.dart';
+import 'luci_build_service/build_tags.dart';
 import 'luci_build_service/engine_artifacts.dart';
 import 'luci_build_service/pending_task.dart';
+import 'luci_build_service/user_data.dart';
 import 'scheduler/ci_yaml_fetcher.dart';
 import 'scheduler/files_changed_optimization.dart';
 import 'scheduler/process_check_run_result.dart';
@@ -368,18 +376,19 @@ class Scheduler {
               'triggerPresubmitTargets($slug, $sha){frameworkOnly}';
           log.info('$logCrumb: FRAMEWORK_ONLY_TESTING_PR');
 
-          await CiStaging.initializeDocument(
+          await UnifiedCheckRun.initializeCiStagingDocument(
             firestoreService: _firestore,
             slug: slug,
             sha: sha,
             stage: CiStage.fusionEngineBuild,
             tasks: [],
-            checkRunGuard: '',
+            pullRequest: pullRequest,
+            config: _config,
           );
 
           await _runCiTestingStage(
             pullRequest: pullRequest,
-            checkRunGuard: '$lock',
+            checkRunGuard: lock,
             logCrumb: logCrumb,
 
             // The if-branch already skips the engine build phase.
@@ -405,13 +414,15 @@ class Scheduler {
         // to complete before we can schedule more tests (i.e. build engine artifacts before testing against them).
         final EngineArtifacts engineArtifacts;
         if (isFusion) {
-          await CiStaging.initializeDocument(
+          await UnifiedCheckRun.initializeCiStagingDocument(
             firestoreService: _firestore,
             slug: slug,
             sha: sha,
             stage: CiStage.fusionEngineBuild,
             tasks: [...presubmitTriggerTargets.map((t) => t.name)],
-            checkRunGuard: '$lock',
+            pullRequest: pullRequest,
+            config: _config,
+            checkRun: lock,
           );
 
           // Even though this appears to be an engine build, it could be a
@@ -433,6 +444,8 @@ class Scheduler {
           targets: presubmitTriggerTargets,
           pullRequest: pullRequest,
           engineArtifacts: engineArtifacts,
+          checkRunGuard: lock,
+          stage: CiStage.fusionEngineBuild,
         );
       } on FormatException catch (e, s) {
         log.warn(
@@ -558,7 +571,7 @@ class Scheduler {
       }
     }
     log.info('$logCrumb: scheduling merge group checks');
-    return triggerTargetsForMergeGroup(
+    return await triggerTargetsForMergeGroup(
       baseRef: baseRef,
       headSha: headSha,
       headRef: headRef,
@@ -625,13 +638,14 @@ class Scheduler {
 
       // Create the staging doc that will track our engine progress and allow us to unlock
       // the merge group lock later.
-      await CiStaging.initializeDocument(
+      await UnifiedCheckRun.initializeCiStagingDocument(
         firestoreService: _firestore,
         slug: slug,
         sha: headSha,
         stage: CiStage.fusionEngineBuild,
         tasks: [...availableTargets.map((t) => t.name)],
-        checkRunGuard: '$lock',
+        config: _config,
+        checkRun: lock,
       );
 
       // Create the minimal Commit needed to pass the next stage.
@@ -1051,17 +1065,176 @@ $s
       case CiStage.fusionEngineBuild:
         if (isMergeGroup) {
           await _completeArtifacts(sha, true);
+          await _closeMergeQueue(
+            mergeQueueGuard: stagingConclusion.checkRunGuard!,
+            slug: slug,
+            sha: sha,
+            stage: CiStage.fusionEngineBuild,
+            logCrumb: logCrumb,
+          );
+        } else {
+          await _closeSuccessfulEngineBuildStage(
+            checkRun: checkRun,
+            mergeQueueGuard: stagingConclusion.checkRunGuard!,
+            slug: slug,
+            sha: sha,
+            logCrumb: logCrumb,
+          );
+        }
+      case CiStage.fusionTests:
+        await _closeSuccessfulTestStage(
+          mergeQueueGuard: stagingConclusion.checkRunGuard!,
+          slug: slug,
+          sha: sha,
+          logCrumb: logCrumb,
+        );
+    }
+    return true;
+  }
+
+  /// Process a completed unified check run.
+  ///
+  /// Handles pull requests only
+  Future<bool> processUnifiedCheckRunCompleted(
+    bbv2.Build build,
+    PresubmitUserData userData,
+  ) async {
+    final name = build.builder.builder;
+    final sha = userData.commit.sha;
+    final status = build.status.toTaskStatus();
+    final slug = userData.commit.slug;
+    final stage = userData.stage!;
+    final tagSet = BuildTags.fromStringPairs(build.tags);
+
+    /// Create a fake check run to pass to existing methods.
+    final checkRun = cocoon_checks.CheckRun(
+      id: userData.guardCheckRunId,
+      name: 'Merge Queue Guard',
+      headSha: userData.commit.sha,
+      checkSuite: CheckSuite(
+        id: userData.checkSuiteId,
+        headBranch: userData.commit.branch,
+        headSha: userData.commit.sha,
+        conclusion: CheckRunConclusion.empty,
+        pullRequests: [],
+      ),
+    );
+
+    if (kCheckRunsToIgnore.contains(name)) {
+      return true;
+    }
+
+    final logCrumb =
+        'processUnifiedCheckRunCompleted($name, $slug, $sha, $status)';
+
+    final isFusion = slug == Config.flutterSlug;
+    if (!isFusion) {
+      return true;
+    }
+
+    final isMergeGroup = detectMergeGroup(checkRun);
+
+    final stagingConclusion = await _markUnifiedCheckRunConclusion(
+      slug: slug,
+      stage: stage,
+      name: name,
+      status: status,
+      pullRequestNumber: userData.pullRequestNumber!,
+      guardCheckRunId: userData.guardCheckRunId!,
+      attempt: tagSet.currentAttempt,
+      startTime: build.startTime.toDateTime().microsecondsSinceEpoch,
+      endTime: build.endTime.toDateTime().microsecondsSinceEpoch,
+      summary: build.summaryMarkdown,
+    );
+
+    // First; check if we even recorded anything. This can occur if we've already passed the check_run and
+    // have moved on to running more tests (which wouldn't be present in our document).
+    if (!stagingConclusion.isOk) {
+      return false;
+    }
+
+    // If an internal error happened in Cocoon, we need human assistance to
+    // figure out next steps.
+    if (stagingConclusion.result ==
+        PresubmitGuardConclusionResult.internalError) {
+      // If an internal error happened in the merge group, there may be no further
+      // signals from GitHub that would cause the merge group to either land or
+      // fail. The safest thing to do is to kick the pull request out of the queue
+      // and let humans sort it out. If the group is left hanging in the queue, it
+      // will hold up all other PRs that are trying to land.
+      if (isMergeGroup) {
+        await _completeArtifacts(sha, false);
+        final guard = checkRunFromString(stagingConclusion.checkRunJson);
+        await failGuardForMergeGroup(
+          slug,
+          sha,
+          stagingConclusion.summary,
+          stagingConclusion.details,
+          guard,
+        );
+      }
+      return false;
+    }
+
+    // Are there tests remaining? Keep waiting.
+    if (stagingConclusion.isPending) {
+      log.info(
+        '$logCrumb: not progressing, remaining work count: ${stagingConclusion.remaining}',
+      );
+      return false;
+    }
+
+    if (stagingConclusion.isFailed) {
+      // Something failed in the current CI stage:
+      //
+      // * If this is a pull request: keep the merge guard open and do not proceed
+      //   to the next stage. Let the author sort out what's up.
+      // * If this is a merge group: kick the pull request out of the queue, and
+      //   let the author sort it out.
+      if (isMergeGroup) {
+        await _completeArtifacts(sha, false);
+        final guard = checkRunFromString(stagingConclusion.checkRunJson);
+        await failGuardForMergeGroup(
+          slug,
+          sha,
+          stagingConclusion.summary,
+          stagingConclusion.details,
+          guard,
+        );
+      }
+      return true;
+    }
+
+    // The logic for finishing a stage is different between build and test stages:
+    //
+    // * If this is a build stage, then:
+    //    * If this is a pull request presubmit, then start the test stage.
+    //    * If this is a merge group (in MQ), then close the MQ guard, letting
+    //      GitHub land it.
+    // * If this is a test stage, then close the MQ guard (allowing the PR to
+    //   enter the MQ).
+    switch (stage) {
+      case CiStage.fusionEngineBuild:
+        if (isMergeGroup) {
+          await _completeArtifacts(sha, true);
+          await _closeMergeQueue(
+            mergeQueueGuard: stagingConclusion.checkRunJson,
+            slug: slug,
+            sha: sha,
+            stage: CiStage.fusionEngineBuild,
+            logCrumb: logCrumb,
+          );
         }
         await _closeSuccessfulEngineBuildStage(
           checkRun: checkRun,
-          mergeQueueGuard: stagingConclusion.checkRunGuard!,
+          mergeQueueGuard: stagingConclusion.checkRunJson,
           slug: slug,
           sha: sha,
           logCrumb: logCrumb,
         );
       case CiStage.fusionTests:
         await _closeSuccessfulTestStage(
-          mergeQueueGuard: stagingConclusion.checkRunGuard!,
+          mergeQueueGuard: stagingConclusion.checkRunJson,
           slug: slug,
           sha: sha,
           logCrumb: logCrumb,
@@ -1101,20 +1274,6 @@ $s
     required String sha,
     required String logCrumb,
   }) async {
-    // We know that we're in a fusion repo; now we need to figure out if we are
-    //   1) in a presubmit test or
-    //   2) in the merge queue
-    if (detectMergeGroup(checkRun)) {
-      await _closeMergeQueue(
-        mergeQueueGuard: mergeQueueGuard,
-        slug: slug,
-        sha: sha,
-        stage: CiStage.fusionEngineBuild,
-        logCrumb: logCrumb,
-      );
-      return;
-    }
-
     log.info(
       '$logCrumb: Stage completed successfully: ${CiStage.fusionEngineBuild}',
     );
@@ -1178,7 +1337,7 @@ $s
   /// Schedules post-engine build tests (i.e. engine tests, and framework tests).
   Future<void> _runCiTestingStage({
     required PullRequest pullRequest,
-    required String checkRunGuard,
+    required CheckRun checkRunGuard,
     required String logCrumb,
     required _FlutterRepoTestsToRun testsToRun,
   }) async {
@@ -1222,13 +1381,15 @@ $s
           tasks = [...presubmitTargets.map((t) => t.name)];
         }
 
-        await CiStaging.initializeDocument(
+        await UnifiedCheckRun.initializeCiStagingDocument(
           firestoreService: _firestore,
           slug: pullRequest.base!.repo!.slug(),
           sha: pullRequest.head!.sha!,
           stage: CiStage.fusionTests,
           tasks: tasks,
-          checkRunGuard: checkRunGuard,
+          config: _config,
+          pullRequest: pullRequest,
+          checkRun: checkRunGuard,
         );
 
         // Here is where it gets fun: how do framework tests* know what engine
@@ -1255,6 +1416,8 @@ $s
           targets: presubmitTargets,
           pullRequest: pullRequest,
           engineArtifacts: engineArtifacts,
+          checkRunGuard: checkRunGuard,
+          stage: CiStage.fusionTests,
         );
       }
     } on FormatException catch (e, s) {
@@ -1314,7 +1477,7 @@ $s
     try {
       await _runCiTestingStage(
         pullRequest: pullRequest,
-        checkRunGuard: '$checkRunGuard',
+        checkRunGuard: checkRunGuard,
         logCrumb: logCrumb,
         testsToRun: _FlutterRepoTestsToRun.engineTestsAndFrameworkTests,
       );
@@ -1382,6 +1545,48 @@ $stacktrace
     });
   }
 
+  Future<PresubmitGuardConclusion> _markUnifiedCheckRunConclusion({
+    required RepositorySlug slug,
+    required CiStage stage,
+    required String name,
+    required TaskStatus status,
+    required int pullRequestNumber,
+    required int guardCheckRunId,
+    required int attempt,
+    int? startTime,
+    int? endTime,
+    String? summary,
+  }) async {
+    final logCrumb = 'checkCompleted($name, $stage, $slug, $status)';
+    final guardId = PresubmitGuardId(
+      slug: slug,
+      pullRequestId: pullRequestNumber,
+      checkRunId: guardCheckRunId,
+      stage: stage,
+    );
+    final state = PresubmitCheckState(
+      buildName: name,
+      status: status,
+      attemptNumber: attempt,
+      startTime: startTime,
+      endTime: endTime,
+      summary: summary,
+    );
+    log.info('$logCrumb: ${guardId.documentId}');
+    // We're doing a transactional update, which could fail if multiple tasks
+    // are running at the same time so retry a sane amount of times before
+    // giving up.
+    const r = RetryOptions(maxAttempts: 3, delayFactor: Duration(seconds: 2));
+
+    return r.retry(() {
+      return UnifiedCheckRun.markConclusion(
+        firestoreService: _firestore,
+        guardId: guardId,
+        state: state,
+      );
+    });
+  }
+
   /// Reschedules a failed build using a [CheckRunEvent]. The CheckRunEvent is
   /// generated when someone clicks the re-run button from a failed build from
   /// the Github UI.
@@ -1510,6 +1715,8 @@ $stacktrace
                 targets: [target],
                 pullRequest: pullRequest,
                 engineArtifacts: engineArtifacts,
+                checkRunGuard: null,
+                stage: null,
               );
             } else {
               log.debug('Rescheduling postsubmit build.');
diff --git a/app_dart/test/request_handlers/presubmit_luci_subscription_test.dart b/app_dart/test/request_handlers/presubmit_luci_subscription_test.dart
index 5584cb84d..a402b9c5b 100644
--- a/app_dart/test/request_handlers/presubmit_luci_subscription_test.dart
+++ b/app_dart/test/request_handlers/presubmit_luci_subscription_test.dart
@@ -91,7 +91,6 @@ void main() {
       ),
     ).thenAnswer((_) async => true);
 
-    when(mockGithubChecksService.taskFailed(any)).thenAnswer((_) => false);
     when(
       mockGithubChecksService.conclusionForResult(any),
     ).thenAnswer((_) => github.CheckRunConclusion.empty);
@@ -136,7 +135,7 @@ void main() {
         slug: anyNamed('slug'),
       ),
     ).thenAnswer((_) async => true);
-    when(mockGithubChecksService.taskFailed(any)).thenAnswer((_) => true);
+
     when(
       mockGithubChecksService.conclusionForResult(any),
     ).thenAnswer((_) => github.CheckRunConclusion.empty);
@@ -155,14 +154,14 @@ void main() {
     );
     tester.message = createPushMessage(
       Int64(1),
-      status: bbv2.Status.SUCCESS,
+      status: bbv2.Status.FAILURE,
       builder: 'Linux A',
       userData: userData,
     );
 
     final buildsPubSub = createBuild(
       Int64(1),
-      status: bbv2.Status.SUCCESS,
+      status: bbv2.Status.FAILURE,
       builder: 'Linux A',
     );
 
@@ -196,11 +195,10 @@ void main() {
         rescheduled: true,
       ),
     ).thenAnswer((_) async => true);
-    when(mockGithubChecksService.taskFailed(any)).thenAnswer((_) => true);
 
     tester.message = createPushMessage(
       Int64(1),
-      status: bbv2.Status.SUCCESS,
+      status: bbv2.Status.FAILURE,
       builder: 'Linux presubmit_max_attempts=2',
       userData: PresubmitUserData(
         commit: CommitRef(
@@ -236,7 +234,9 @@ void main() {
         rescheduled: true,
       ),
     ).thenAnswer((_) async => true);
-    when(mockGithubChecksService.taskFailed(any)).thenAnswer((_) => true);
+    when(
+      mockLuciBuildService.getBuildById(any, buildMask: anyNamed('buildMask')),
+    ).thenAnswer((_) async => bbv2.Build(summaryMarkdown: 'test summary'));
 
     tester.message = createPushMessage(
       Int64(1),
@@ -315,7 +315,7 @@ void main() {
         rescheduled: false,
       ),
     ).thenAnswer((_) async => true);
-    when(mockGithubChecksService.taskFailed(any)).thenAnswer((_) => true);
+
     when(
       mockGithubChecksService.conclusionForResult(any),
     ).thenAnswer((_) => github.CheckRunConclusion.empty);
@@ -335,14 +335,14 @@ void main() {
 
     tester.message = createPushMessage(
       Int64(1),
-      status: bbv2.Status.SUCCESS,
+      status: bbv2.Status.FAILURE,
       builder: 'Linux C',
       userData: userData,
     );
 
     final buildsPubSub = createBuild(
       Int64(1),
-      status: bbv2.Status.SUCCESS,
+      status: bbv2.Status.FAILURE,
       builder: 'Linux C',
     );
 
@@ -364,7 +364,7 @@ void main() {
         rescheduled: false,
       ),
     ).called(1);
-    verify(mockGithubChecksService.taskFailed(any)).called(1);
+
     verify(mockScheduler.processCheckRunCompleted(any, any)).called(1);
   });
 
@@ -378,7 +378,7 @@ void main() {
         rescheduled: false,
       ),
     ).thenAnswer((_) async => true);
-    when(mockGithubChecksService.taskFailed(any)).thenAnswer((_) => true);
+
     when(
       mockGithubChecksService.conclusionForResult(any),
     ).thenAnswer((_) => github.CheckRunConclusion.empty);
@@ -397,14 +397,14 @@ void main() {
     );
     tester.message = createPushMessage(
       Int64(1),
-      status: bbv2.Status.SUCCESS,
+      status: bbv2.Status.FAILURE,
       builder: 'Linux C',
       userData: userData,
     );
 
     final buildsPubSub = createBuild(
       Int64(1),
-      status: bbv2.Status.SUCCESS,
+      status: bbv2.Status.FAILURE,
       builder: 'Linux C',
     );
 
@@ -430,8 +430,6 @@ void main() {
   });
 
   test('Pubsub rejected if branch is not enabled.', () async {
-    when(mockGithubChecksService.taskFailed(any)).thenAnswer((_) => true);
-
     final userData = PresubmitUserData(
       checkRunId: 1,
       checkSuiteId: 2,
@@ -443,7 +441,7 @@ void main() {
     );
     tester.message = createPushMessage(
       Int64(1),
-      status: bbv2.Status.SUCCESS,
+      status: bbv2.Status.FAILURE,
       builder: 'Linux C',
       userData: userData,
     );
@@ -470,11 +468,13 @@ void main() {
         rescheduled: anyNamed('rescheduled'),
       ),
     ).thenAnswer((_) async => true);
-    when(mockGithubChecksService.taskFailed(any)).thenAnswer((_) => true);
+    when(
+      mockLuciBuildService.getBuildById(any, buildMask: anyNamed('buildMask')),
+    ).thenAnswer((_) async => bbv2.Build(summaryMarkdown: 'test summary'));
 
     tester.message = createPushMessage(
       Int64(1),
-      status: bbv2.Status.SUCCESS,
+      status: bbv2.Status.FAILURE,
       builder: 'Linux presubmit_max_attempts=2',
       userData: PresubmitUserData(
         checkRunId: 1,
@@ -545,7 +545,6 @@ void main() {
         rescheduled: anyNamed('rescheduled'),
       ),
     ).thenAnswer((_) async => true);
-    when(mockGithubChecksService.taskFailed(any)).thenAnswer((_) => false);
 
     tester.message = createPushMessage(
       Int64(1),
diff --git a/app_dart/test/service/luci_build_service/schedule_try_builds_test.dart b/app_dart/test/service/luci_build_service/schedule_try_builds_test.dart
index 814a8339f..8665f4a87 100644
--- a/app_dart/test/service/luci_build_service/schedule_try_builds_test.dart
+++ b/app_dart/test/service/luci_build_service/schedule_try_builds_test.dart
@@ -7,9 +7,13 @@ import 'package:cocoon_common_test/cocoon_common_test.dart';
 import 'package:cocoon_server/logging.dart';
 import 'package:cocoon_server_test/test_logging.dart';
 import 'package:cocoon_service/src/model/commit_ref.dart';
+import 'package:cocoon_service/src/model/firestore/base.dart';
 import 'package:cocoon_service/src/model/firestore/pr_check_runs.dart';
 import 'package:cocoon_service/src/service/cache_service.dart';
+import 'package:cocoon_service/src/service/flags/dynamic_config.dart';
+import 'package:cocoon_service/src/service/flags/unified_check_run_flow_flags.dart';
 import 'package:cocoon_service/src/service/luci_build_service.dart';
+import 'package:cocoon_service/src/service/luci_build_service/build_tags.dart';
 import 'package:cocoon_service/src/service/luci_build_service/engine_artifacts.dart';
 import 'package:cocoon_service/src/service/luci_build_service/user_data.dart';
 import 'package:fixnum/fixnum.dart';
@@ -400,6 +404,151 @@ void main() {
     );
   });
 
+  group('Unified Check Run Flow', () {
+    test(
+      'schedules try builds with unified check run flow and guard',
+      () async {
+        final pullRequest = generatePullRequest(
+          id: 1,
+          repo: 'flutter',
+          headSha: 'headsha123',
+        );
+
+        final buildTarget = generateTarget(
+          1,
+          properties: {'os': 'abc'},
+          slug: RepositorySlug.full('flutter/flutter'),
+          name: 'Linux foo',
+        );
+
+        // Enable Unified Check Run Flow
+        luci = LuciBuildService(
+          config: FakeConfig(
+            dynamicConfig: DynamicConfig(
+              unifiedCheckRunFlow: UnifiedCheckRunFlow(useForAll: true),
+            ),
+          ),
+          cache: CacheService(inMemory: true),
+          buildBucketClient: mockBuildBucketClient,
+          githubChecksUtil: mockGithubChecksUtil,
+          pubsub: pubSub,
+          gerritService: gerritService,
+          firestore: firestore,
+        );
+
+        final checkRunGuard = generateCheckRun(1234, name: 'Guard');
+
+        await expectLater(
+          luci.scheduleTryBuilds(
+            pullRequest: pullRequest,
+            targets: [buildTarget],
+            engineArtifacts: EngineArtifacts.builtFromSource(
+              commitSha: pullRequest.head!.sha!,
+            ),
+            checkRunGuard: checkRunGuard,
+            stage: CiStage.fusionTests,
+          ),
+          completion([isTarget.hasName('Linux foo')]),
+        );
+
+        // Should NOT create individual check runs
+        verifyNever(mockGithubChecksUtil.createCheckRun(any, any, any, any));
+
+        final bbv2.ScheduleBuildRequest scheduleBuild;
+        {
+          final batchRequest = bbv2.BatchRequest().createEmptyInstance();
+          batchRequest.mergeFromProto3Json(pubSub.messages.single);
+          scheduleBuild = batchRequest.requests.single.scheduleBuild;
+        }
+
+        final userData = PresubmitUserData.fromBytes(
+          scheduleBuild.notify.userData,
+        );
+        expect(userData.guardCheckRunId, 1234);
+        expect(userData.stage, CiStage.fusionTests);
+        expect(userData.checkRunId, isNull);
+
+        final tags = BuildTags.fromStringPairs(scheduleBuild.tags);
+        expect(
+          tags.buildTags.contains(
+            GuardCheckRunIdBuildTag(guardCheckRunId: 1234),
+          ),
+          isTrue,
+          reason: 'Should have GuardCheckRunIdBuildTag',
+        );
+      },
+    );
+
+    test('falls back to individual check runs when guard is missing', () async {
+      final pullRequest = generatePullRequest(
+        id: 1,
+        repo: 'flutter',
+        headSha: 'headsha123',
+      );
+
+      final buildTarget = generateTarget(
+        1,
+        properties: {'os': 'abc'},
+        slug: RepositorySlug.full('flutter/flutter'),
+        name: 'Linux foo',
+      );
+
+      // Enable Unified Check Run Flow but provide NO guard
+      luci = LuciBuildService(
+        config: FakeConfig(
+          dynamicConfig: DynamicConfig(
+            unifiedCheckRunFlow: UnifiedCheckRunFlow(useForAll: true),
+          ),
+        ),
+        cache: CacheService(inMemory: true),
+        buildBucketClient: mockBuildBucketClient,
+        githubChecksUtil: mockGithubChecksUtil,
+        pubsub: pubSub,
+        gerritService: gerritService,
+        firestore: firestore,
+      );
+
+      when(
+        mockGithubChecksUtil.createCheckRun(any, any, any, any),
+      ).thenAnswer((_) async => generateCheckRun(456, name: 'Linux foo'));
+
+      await expectLater(
+        luci.scheduleTryBuilds(
+          pullRequest: pullRequest,
+          targets: [buildTarget],
+          engineArtifacts: EngineArtifacts.builtFromSource(
+            commitSha: pullRequest.head!.sha!,
+          ),
+          checkRunGuard: null, // No guard provided
+        ),
+        completion([isTarget.hasName('Linux foo')]),
+      );
+
+      // Should create individual check run as fallback
+      verify(
+        mockGithubChecksUtil.createCheckRun(
+          any,
+          RepositorySlug.full('flutter/flutter'),
+          'headsha123',
+          'Linux foo',
+        ),
+      ).called(1);
+
+      final bbv2.ScheduleBuildRequest scheduleBuild;
+      {
+        final batchRequest = bbv2.BatchRequest().createEmptyInstance();
+        batchRequest.mergeFromProto3Json(pubSub.messages.single);
+        scheduleBuild = batchRequest.requests.single.scheduleBuild;
+      }
+
+      final userData = PresubmitUserData.fromBytes(
+        scheduleBuild.notify.userData,
+      );
+      expect(userData.checkRunId, 456);
+      expect(userData.guardCheckRunId, isNull);
+    });
+  });
+
   group('CIPD', () {
     final loggedFallingBackToDefaultRecipe = bufferedLoggerOf(
       contains(logThat(message: contains('Falling back to default recipe'))),
diff --git a/app_dart/test/service/luci_build_service/user_data_test.dart b/app_dart/test/service/luci_build_service/user_data_test.dart
index 3c4305114..d810103ed 100644
--- a/app_dart/test/service/luci_build_service/user_data_test.dart
+++ b/app_dart/test/service/luci_build_service/user_data_test.dart
@@ -30,6 +30,9 @@ void main() {
         'commit_branch': 'main',
         'repo_owner': 'repo-owner',
         'repo_name': 'repo-name',
+        'guard_check_run_id': null,
+        'pull_request_number': null,
+        'stage': null,
       });
     });
 
@@ -42,6 +45,8 @@ void main() {
           'commit_branch': 'main',
           'repo_owner': 'repo-owner',
           'repo_name': 'repo-name',
+          'guard_check_run_id': null,
+          'stage': null,
         }),
         PresubmitUserData(
           checkRunId: 1234,
diff --git a/app_dart/test/service/scheduler/hash_workflow_test.dart b/app_dart/test/service/scheduler/hash_workflow_test.dart
index ddf1e70f2..7bee9f98e 100644
--- a/app_dart/test/service/scheduler/hash_workflow_test.dart
+++ b/app_dart/test/service/scheduler/hash_workflow_test.dart
@@ -60,6 +60,7 @@ void main() {
         targets: anyNamed('targets'),
         pullRequest: anyNamed('pullRequest'),
         engineArtifacts: anyNamed('engineArtifacts'),
+        checkRunGuard: anyNamed('checkRunGuard'),
       ),
     ).thenAnswer((inv) async {
       return [];
diff --git a/app_dart/test/service/scheduler_test.dart b/app_dart/test/service/scheduler_test.dart
index ac1b1d178..8602c9e97 100644
--- a/app_dart/test/service/scheduler_test.dart
+++ b/app_dart/test/service/scheduler_test.dart
@@ -12,20 +12,25 @@ import 'package:cocoon_server_test/test_logging.dart';
 import 'package:cocoon_service/cocoon_service.dart';
 import 'package:cocoon_service/src/model/ci_yaml/ci_yaml.dart';
 import 'package:cocoon_service/src/model/ci_yaml/target.dart';
+import 'package:cocoon_service/src/model/commit_ref.dart';
 import 'package:cocoon_service/src/model/firestore/base.dart';
 import 'package:cocoon_service/src/model/firestore/ci_staging.dart';
 import 'package:cocoon_service/src/model/firestore/commit.dart' as fs;
 import 'package:cocoon_service/src/model/firestore/pr_check_runs.dart';
+import 'package:cocoon_service/src/model/firestore/presubmit_check.dart';
+import 'package:cocoon_service/src/model/firestore/presubmit_guard.dart';
 import 'package:cocoon_service/src/model/firestore/task.dart' as fs;
 import 'package:cocoon_service/src/model/github/checks.dart' as cocoon_checks;
 import 'package:cocoon_service/src/service/big_query.dart';
+import 'package:cocoon_service/src/service/firestore/unified_check_run.dart';
 import 'package:cocoon_service/src/service/flags/dynamic_config.dart';
+import 'package:cocoon_service/src/service/flags/unified_check_run_flow_flags.dart';
 import 'package:cocoon_service/src/service/luci_build_service/engine_artifacts.dart';
 import 'package:cocoon_service/src/service/luci_build_service/pending_task.dart';
+import 'package:cocoon_service/src/service/luci_build_service/user_data.dart';
 import 'package:cocoon_service/src/service/scheduler/process_check_run_result.dart';
 import 'package:fixnum/fixnum.dart';
 import 'package:github/github.dart';
-import 'package:github/hooks.dart';
 import 'package:googleapis/bigquery/v2.dart';
 import 'package:mockito/mockito.dart';
 import 'package:test/test.dart';
@@ -956,6 +961,8 @@ void main() {
             targets: anyNamed('targets'),
             pullRequest: anyNamed('pullRequest'),
             engineArtifacts: anyNamed('engineArtifacts'),
+            checkRunGuard: anyNamed('checkRunGuard'),
+            stage: anyNamed('stage'),
           ),
         ).thenAnswer((inv) async {
           return [];
@@ -1369,6 +1376,8 @@ targets:
                 targets: anyNamed('targets'),
                 pullRequest: anyNamed('pullRequest'),
                 engineArtifacts: anyNamed('engineArtifacts'),
+                checkRunGuard: anyNamed('checkRunGuard'),
+                stage: anyNamed('stage'),
               ),
             ).thenAnswer((inv) async {
               return [];
@@ -1454,6 +1463,8 @@ targets:
                 targets: captureAnyNamed('targets'),
                 pullRequest: captureAnyNamed('pullRequest'),
                 engineArtifacts: anyNamed('engineArtifacts'),
+                checkRunGuard: anyNamed('checkRunGuard'),
+                stage: anyNamed('stage'),
               ),
             );
             expect(result.callCount, 1);
@@ -1506,6 +1517,8 @@ targets:
                   targets: anyNamed('targets'),
                   pullRequest: anyNamed('pullRequest'),
                   engineArtifacts: anyNamed('engineArtifacts'),
+                  checkRunGuard: anyNamed('checkRunGuard'),
+                  stage: anyNamed('stage'),
                 ),
               ).thenAnswer((inv) async {
                 return [];
@@ -1595,6 +1608,8 @@ targets:
                   targets: captureAnyNamed('targets'),
                   pullRequest: captureAnyNamed('pullRequest'),
                   engineArtifacts: anyNamed('engineArtifacts'),
+                  checkRunGuard: anyNamed('checkRunGuard'),
+                  stage: anyNamed('stage'),
                 ),
               );
               expect(result.callCount, 1);
@@ -1830,6 +1845,8 @@ targets:
                 targets: anyNamed('targets'),
                 pullRequest: anyNamed('pullRequest'),
                 engineArtifacts: anyNamed('engineArtifacts'),
+                checkRunGuard: anyNamed('checkRunGuard'),
+                stage: anyNamed('stage'),
               ),
             ).thenAnswer((Invocation i) async {
               engineArtifacts =
@@ -2153,6 +2170,8 @@ targets:
                   targets: anyNamed('targets'),
                   pullRequest: anyNamed('pullRequest'),
                   engineArtifacts: anyNamed('engineArtifacts'),
+                  checkRunGuard: anyNamed('checkRunGuard'),
+                  stage: anyNamed('stage'),
                 ),
               ).thenAnswer((inv) async {
                 return [];
@@ -2226,6 +2245,8 @@ targets:
                   targets: captureAnyNamed('targets'),
                   pullRequest: captureAnyNamed('pullRequest'),
                   engineArtifacts: anyNamed('engineArtifacts'),
+                  checkRunGuard: anyNamed('checkRunGuard'),
+                  stage: anyNamed('stage'),
                 ),
               );
               expect(result.callCount, 1);
@@ -2728,6 +2749,8 @@ targets:
             targets: anyNamed('targets'),
             pullRequest: anyNamed('pullRequest'),
             engineArtifacts: anyNamed('engineArtifacts'),
+            checkRunGuard: anyNamed('checkRunGuard'),
+            stage: anyNamed('stage'),
           ),
         ).thenAnswer((inv) async {
           return [];
@@ -2796,6 +2819,8 @@ targets:
             targets: captureAnyNamed('targets'),
             pullRequest: anyNamed('pullRequest'),
             engineArtifacts: anyNamed('engineArtifacts'),
+            checkRunGuard: anyNamed('checkRunGuard'),
+            stage: anyNamed('stage'),
           ),
         );
         expect(result.callCount, 1);
@@ -2858,6 +2883,8 @@ targets:
             targets: anyNamed('targets'),
             pullRequest: anyNamed('pullRequest'),
             engineArtifacts: anyNamed('engineArtifacts'),
+            checkRunGuard: anyNamed('checkRunGuard'),
+            stage: anyNamed('stage'),
           ),
         ).thenAnswer((inv) async {
           return [];
@@ -2994,6 +3021,8 @@ targets:
             targets: anyNamed('targets'),
             pullRequest: anyNamed('pullRequest'),
             engineArtifacts: anyNamed('engineArtifacts'),
+            checkRunGuard: anyNamed('checkRunGuard'),
+            stage: anyNamed('stage'),
           ),
         ).thenAnswer((inv) async {
           return [];
@@ -3122,6 +3151,8 @@ targets:
             targets: anyNamed('targets'),
             pullRequest: anyNamed('pullRequest'),
             engineArtifacts: anyNamed('engineArtifacts'),
+            checkRunGuard: anyNamed('checkRunGuard'),
+            stage: anyNamed('stage'),
           ),
         ).thenAnswer((inv) async {
           return [];
@@ -3504,6 +3535,273 @@ targets:
         );
       });
     });
+    group('process unified check run', () {
+      late _CapturingFakeLuciBuildService fakeLuciBuildService;
+
+      setUp(() {
+        fakeLuciBuildService = _CapturingFakeLuciBuildService();
+        scheduler = Scheduler(
+          cache: cache,
+          config: config,
+          githubChecksService: GithubChecksService(
+            config,
+            githubChecksUtil: mockGithubChecksUtil,
+          ),
+          getFilesChanged: getFilesChanged,
+          ciYamlFetcher: ciYamlFetcher,
+          luciBuildService: fakeLuciBuildService,
+          contentAwareHash: fakeContentAwareHash,
+          firestore: firestore,
+          bigQuery: bigQuery,
+        );
+      });
+
+      test('schedules tests after engine stage', () async {
+        final pullRequest = generatePullRequest();
+        final checkRunGuard = generateCheckRun(1234, name: 'Merge Queue Guard');
+
+        await PrCheckRuns.initializeDocument(
+          firestoreService: firestore,
+          checks: [checkRunGuard],
+          pullRequest: pullRequest,
+        );
+
+        // Initialize presubmit guard for engine stage
+        await UnifiedCheckRun.initializePresubmitGuardDocument(
+          firestoreService: firestore,
+          slug: pullRequest.base!.repo!.slug(),
+          pullRequestId: pullRequest.number!,
+          checkRun: checkRunGuard,
+          stage: CiStage.fusionEngineBuild,
+          commitSha: pullRequest.head!.sha!,
+          creationTime: DateTime.now().millisecondsSinceEpoch,
+          author: pullRequest.user!.login!,
+          tasks: ['Linux engine_build'],
+        );
+
+        // Initialize check run for the task
+        firestore.putDocument(
+          PresubmitCheck.init(
+            buildName: 'Linux engine_build',
+            checkRunId: checkRunGuard.id!,
+            creationTime: DateTime.now().millisecondsSinceEpoch,
+          ),
+        );
+
+        // Enable fusion
+        ciYamlFetcher.setCiYamlFrom(singleCiYaml, engine: fusionCiYaml);
+        config.dynamicConfig = DynamicConfig(
+          unifiedCheckRunFlow: UnifiedCheckRunFlow(useForAll: true),
+        );
+
+        final userData = PresubmitUserData(
+          commit: CommitRef(
+            slug: pullRequest.base!.repo!.slug(),
+            sha: pullRequest.head!.sha!,
+            branch: pullRequest.head!.ref!,
+          ),
+          guardCheckRunId: checkRunGuard.id,
+          stage: CiStage.fusionEngineBuild,
+          checkSuiteId: 2,
+          pullRequestNumber: pullRequest.number,
+        );
+
+        final build = generateBbv2Build(
+          Int64(1),
+          name: 'Linux engine_build',
+          tags: [
+            bbv2.StringPair(key: 'current_attempt', value: '1'),
+            bbv2.StringPair(
+              key: 'buildset',
+              value: 'sha/git/${pullRequest.head!.sha!}',
+            ),
+          ],
+        );
+
+        expect(
+          await scheduler.processUnifiedCheckRunCompleted(build, userData),
+          isTrue,
+        );
+
+        // Should schedule tests for the next stage (fusionTests)
+        expect(fakeLuciBuildService.scheduledTryBuilds, isNotEmpty);
+        expect(fakeLuciBuildService.stage, CiStage.fusionTests);
+        // Verify state update in Firestore
+        final guards = await firestore.query(PresubmitGuard.collectionId, {});
+        final guard = guards
+            .map(PresubmitGuard.fromDocument)
+            .firstWhere((g) => g.stage == CiStage.fusionEngineBuild);
+        expect(guard.builds?['Linux engine_build'], TaskStatus.succeeded);
+        expect(guard.remainingBuilds, 0);
+      });
+
+      test(
+        'fails the merge queue guard when a test check run fails (merge group)',
+        () async {
+          final pullRequest = generatePullRequest();
+          final checkRunGuard = generateCheckRun(
+            1234,
+            name: 'Merge Queue Guard',
+            startedAt: DateTime.now(),
+          );
+
+          await PrCheckRuns.initializeDocument(
+            firestoreService: firestore,
+            checks: [checkRunGuard],
+            pullRequest: pullRequest,
+          );
+
+          // Make it look like a merge group
+          // checkRunGuard.checkSuite!.headBranch = 'gh-readonly-queue/master/pr-123-abc';
+
+          // Initialize presubmit guard for tests stage
+          await UnifiedCheckRun.initializePresubmitGuardDocument(
+            firestoreService: firestore,
+            slug: pullRequest.base!.repo!.slug(),
+            pullRequestId: pullRequest.number!,
+            checkRun: checkRunGuard,
+            stage: CiStage.fusionTests,
+            commitSha: pullRequest.head!.sha!,
+            creationTime: DateTime.now().millisecondsSinceEpoch,
+            author: pullRequest.user!.login!,
+            tasks: ['Linux test'],
+          );
+
+          // Initialize check run for the task
+          firestore.putDocument(
+            PresubmitCheck.init(
+              buildName: 'Linux test',
+              checkRunId: checkRunGuard.id!,
+              creationTime: DateTime.now().millisecondsSinceEpoch,
+            ),
+          );
+
+          final userData = PresubmitUserData(
+            commit: CommitRef(
+              slug: pullRequest.base!.repo!.slug(),
+              sha: pullRequest.head!.sha!,
+              branch: 'gh-readonly-queue/master/pr-123-abc',
+            ),
+            guardCheckRunId: checkRunGuard.id,
+            stage: CiStage.fusionTests,
+            checkSuiteId: 2,
+            pullRequestNumber: pullRequest.number,
+          );
+
+          final build = generateBbv2Build(
+            Int64(1),
+            name: 'Linux test',
+            status: bbv2.Status.FAILURE,
+            tags: [bbv2.StringPair(key: 'current_attempt', value: '1')],
+          );
+
+          expect(
+            await scheduler.processUnifiedCheckRunCompleted(build, userData),
+            isTrue,
+          );
+
+          verify(
+            mockGithubChecksUtil.updateCheckRun(
+              any,
+              any,
+              any,
+              status: anyNamed('status'),
+              conclusion: CheckRunConclusion.failure, // Merge queue failure
+              output: anyNamed('output'),
+            ),
+          ).called(1);
+
+          final guards = await firestore.query(PresubmitGuard.collectionId, {});
+          final guard = PresubmitGuard.fromDocument(guards.single);
+          expect(guard.failedBuilds, 1);
+        },
+      );
+
+      test('closes merge queue guard in merge group success', () async {
+        final pullRequest = generatePullRequest();
+        final checkRunGuard = generateCheckRun(
+          1234,
+          name: 'Merge Queue Guard',
+          startedAt: DateTime.now(),
+        );
+
+        await PrCheckRuns.initializeDocument(
+          firestoreService: firestore,
+          checks: [checkRunGuard],
+          pullRequest: pullRequest,
+        );
+
+        // Make it look like a merge group
+        // checkRunGuard.checkSuite!.headBranch = 'gh-readonly-queue/master/pr-123-abc';
+
+        // Initialize presubmit guard for tests stage
+        await UnifiedCheckRun.initializePresubmitGuardDocument(
+          firestoreService: firestore,
+          slug: pullRequest.base!.repo!.slug(),
+          pullRequestId: pullRequest.number!,
+          checkRun: checkRunGuard,
+          stage: CiStage.fusionTests,
+          commitSha: pullRequest.head!.sha!,
+          creationTime: DateTime.now().millisecondsSinceEpoch,
+          author: pullRequest.user!.login!,
+          tasks: ['Linux test'],
+        );
+
+        // Initialize check run for the task
+        firestore.putDocument(
+          PresubmitCheck.init(
+            buildName: 'Linux test',
+            checkRunId: checkRunGuard.id!,
+            creationTime: DateTime.now().millisecondsSinceEpoch,
+          ),
+        );
+
+        final userData = PresubmitUserData(
+          commit: CommitRef(
+            slug: pullRequest.base!.repo!.slug(),
+            sha: pullRequest.head!.sha!,
+            branch: 'gh-readonly-queue/master/pr-123-abc',
+          ),
+          guardCheckRunId: checkRunGuard.id,
+          stage: CiStage.fusionTests,
+          checkSuiteId: 2,
+          pullRequestNumber: pullRequest.number,
+        );
+
+        final build = generateBbv2Build(
+          Int64(1),
+          name: 'Linux test',
+          status: bbv2.Status.SUCCESS,
+          tags: [
+            bbv2.StringPair(key: 'current_attempt', value: '1'),
+            bbv2.StringPair(
+              key: 'buildset',
+              value: 'sha/git/${pullRequest.head!.sha!}',
+            ),
+          ],
+        );
+
+        expect(
+          await scheduler.processUnifiedCheckRunCompleted(build, userData),
+          isTrue,
+        );
+
+        verify(
+          mockGithubChecksUtil.updateCheckRun(
+            any,
+            any,
+            any,
+            status: anyNamed('status'),
+            conclusion: CheckRunConclusion.success, // Merge queue success
+            output: anyNamed('output'),
+          ),
+        ).called(1);
+
+        final guards = await firestore.query(PresubmitGuard.collectionId, {});
+        final guard = PresubmitGuard.fromDocument(guards.single);
+        expect(guard.remainingBuilds, 0);
+      });
+    });
   });
 }
 
@@ -3511,16 +3809,23 @@ final class _CapturingFakeLuciBuildService extends Fake
     implements LuciBuildService {
   List<Target> scheduledTryBuilds = [];
   EngineArtifacts? engineArtifacts;
+  PullRequest? pullRequest;
+  CheckRun? checkRunGuard;
+  CiStage? stage;
 
   @override
   Future<List<Target>> scheduleTryBuilds({
     required List<Target> targets,
     required PullRequest pullRequest,
-    CheckSuiteEvent? checkSuiteEvent,
-    EngineArtifacts? engineArtifacts,
+    required EngineArtifacts engineArtifacts,
+    CheckRun? checkRunGuard,
+    CiStage? stage,
   }) async {
     scheduledTryBuilds = targets;
     this.engineArtifacts = engineArtifacts;
+    this.pullRequest = pullRequest;
+    this.checkRunGuard = checkRunGuard;
+    this.stage = stage;
     return targets;
   }
 
diff --git a/app_dart/test/src/utilities/mocks.mocks.dart b/app_dart/test/src/utilities/mocks.mocks.dart
index afa677853..9aa263480 100644
--- a/app_dart/test/src/utilities/mocks.mocks.dart
+++ b/app_dart/test/src/utilities/mocks.mocks.dart
@@ -12,13 +12,14 @@ import 'package:buildbucket/buildbucket_pb.dart' as _i6;
 import 'package:cocoon_common/rpc_model.dart' as _i19;
 import 'package:cocoon_service/cocoon_service.dart' as _i17;
 import 'package:cocoon_service/src/foundation/github_checks_util.dart' as _i10;
-import 'package:cocoon_service/src/model/ci_yaml/ci_yaml.dart' as _i40;
+import 'package:cocoon_service/src/model/ci_yaml/ci_yaml.dart' as _i41;
 import 'package:cocoon_service/src/model/ci_yaml/target.dart' as _i28;
-import 'package:cocoon_service/src/model/commit_ref.dart' as _i32;
-import 'package:cocoon_service/src/model/firestore/commit.dart' as _i38;
-import 'package:cocoon_service/src/model/firestore/task.dart' as _i33;
-import 'package:cocoon_service/src/model/github/checks.dart' as _i31;
-import 'package:cocoon_service/src/model/github/workflow_job.dart' as _i39;
+import 'package:cocoon_service/src/model/commit_ref.dart' as _i33;
+import 'package:cocoon_service/src/model/firestore/base.dart' as _i30;
+import 'package:cocoon_service/src/model/firestore/commit.dart' as _i39;
+import 'package:cocoon_service/src/model/firestore/task.dart' as _i34;
+import 'package:cocoon_service/src/model/github/checks.dart' as _i32;
+import 'package:cocoon_service/src/model/github/workflow_job.dart' as _i40;
 import 'package:cocoon_service/src/service/big_query.dart' as _i18;
 import 'package:cocoon_service/src/service/commit_service.dart' as _i21;
 import 'package:cocoon_service/src/service/config.dart' as _i2;
@@ -26,18 +27,18 @@ import 'package:cocoon_service/src/service/discord_service.dart' as _i25;
 import 'package:cocoon_service/src/service/flags/dynamic_config.dart' as _i24;
 import 'package:cocoon_service/src/service/github_service.dart' as _i9;
 import 'package:cocoon_service/src/service/luci_build_service/build_tags.dart'
-    as _i36;
+    as _i37;
 import 'package:cocoon_service/src/service/luci_build_service/cipd_version.dart'
     as _i23;
 import 'package:cocoon_service/src/service/luci_build_service/engine_artifacts.dart'
     as _i29;
 import 'package:cocoon_service/src/service/luci_build_service/pending_task.dart'
-    as _i35;
+    as _i36;
 import 'package:cocoon_service/src/service/luci_build_service/user_data.dart'
-    as _i30;
+    as _i31;
 import 'package:cocoon_service/src/service/scheduler/process_check_run_result.dart'
-    as _i41;
-import 'package:fixnum/fixnum.dart' as _i34;
+    as _i42;
+import 'package:fixnum/fixnum.dart' as _i35;
 import 'package:github/github.dart' as _i7;
 import 'package:github/hooks.dart' as _i22;
 import 'package:googleapis/bigquery/v2.dart' as _i4;
@@ -49,7 +50,7 @@ import 'package:http/http.dart' as _i5;
 import 'package:mockito/mockito.dart' as _i1;
 import 'package:mockito/src/dummies.dart' as _i20;
 import 'package:neat_cache/neat_cache.dart' as _i16;
-import 'package:process/src/interface/process_manager.dart' as _i37;
+import 'package:process/src/interface/process_manager.dart' as _i38;
 
 import '../../service/cache_service_test.dart' as _i26;
 
@@ -1886,14 +1887,6 @@ class MockGithubChecksService extends _i1.Mock
           )
           as _i13.Future<bool>);
 
-  @override
-  bool taskFailed(_i6.Status? status) =>
-      (super.noSuchMethod(
-            Invocation.method(#taskFailed, [status]),
-            returnValue: false,
-          )
-          as bool);
-
   @override
   String getGithubSummary(String? summary) =>
       (super.noSuchMethod(
@@ -4074,12 +4067,16 @@ class MockLuciBuildService extends _i1.Mock implements _i17.LuciBuildService {
     required List<_i28.Target>? targets,
     required _i7.PullRequest? pullRequest,
     required _i29.EngineArtifacts? engineArtifacts,
+    _i7.CheckRun? checkRunGuard,
+    _i30.CiStage? stage,
   }) =>
       (super.noSuchMethod(
             Invocation.method(#scheduleTryBuilds, [], {
               #targets: targets,
               #pullRequest: pullRequest,
               #engineArtifacts: engineArtifacts,
+              #checkRunGuard: checkRunGuard,
+              #stage: stage,
             }),
             returnValue: _i13.Future<List<_i28.Target>>.value(<_i28.Target>[]),
           )
@@ -4120,7 +4117,7 @@ class MockLuciBuildService extends _i1.Mock implements _i17.LuciBuildService {
     required String? builderName,
     required _i6.Build? build,
     required int? nextAttempt,
-    required _i30.PresubmitUserData? userData,
+    required _i31.PresubmitUserData? userData,
   }) =>
       (super.noSuchMethod(
             Invocation.method(#reschedulePresubmitBuild, [], {
@@ -4145,10 +4142,10 @@ class MockLuciBuildService extends _i1.Mock implements _i17.LuciBuildService {
 
   @override
   _i13.Future<void> reschedulePostsubmitBuildUsingCheckRunEvent(
-    _i31.CheckRunEvent? checkRunEvent, {
-    required _i32.CommitRef? commit,
+    _i32.CheckRunEvent? checkRunEvent, {
+    required _i33.CommitRef? commit,
     required _i28.Target? target,
-    required _i33.Task? task,
+    required _i34.Task? task,
   }) =>
       (super.noSuchMethod(
             Invocation.method(
@@ -4163,7 +4160,7 @@ class MockLuciBuildService extends _i1.Mock implements _i17.LuciBuildService {
 
   @override
   _i13.Future<_i6.Build> getBuildById(
-    _i34.Int64? id, {
+    _i35.Int64? id, {
     _i6.BuildMask? buildMask,
   }) =>
       (super.noSuchMethod(
@@ -4192,9 +4189,9 @@ class MockLuciBuildService extends _i1.Mock implements _i17.LuciBuildService {
           as _i13.Future<Set<String>>);
 
   @override
-  _i13.Future<List<_i35.PendingTask>> schedulePostsubmitBuilds({
-    required _i32.CommitRef? commit,
-    required List<_i35.PendingTask>? toBeScheduled,
+  _i13.Future<List<_i36.PendingTask>> schedulePostsubmitBuilds({
+    required _i33.CommitRef? commit,
+    required List<_i36.PendingTask>? toBeScheduled,
     String? contentHash,
   }) =>
       (super.noSuchMethod(
@@ -4203,15 +4200,15 @@ class MockLuciBuildService extends _i1.Mock implements _i17.LuciBuildService {
               #toBeScheduled: toBeScheduled,
               #contentHash: contentHash,
             }),
-            returnValue: _i13.Future<List<_i35.PendingTask>>.value(
-              <_i35.PendingTask>[],
+            returnValue: _i13.Future<List<_i36.PendingTask>>.value(
+              <_i36.PendingTask>[],
             ),
           )
-          as _i13.Future<List<_i35.PendingTask>>);
+          as _i13.Future<List<_i36.PendingTask>>);
 
   @override
   _i13.Future<void> scheduleMergeGroupBuilds({
-    required _i32.CommitRef? commit,
+    required _i33.CommitRef? commit,
     required List<_i28.Target>? targets,
     String? contentHash,
   }) =>
@@ -4228,7 +4225,7 @@ class MockLuciBuildService extends _i1.Mock implements _i17.LuciBuildService {
 
   @override
   _i13.Future<_i7.CheckRun> createPostsubmitCheckRun(
-    _i32.CommitRef? commit,
+    _i33.CommitRef? commit,
     _i28.Target? target,
   ) =>
       (super.noSuchMethod(
@@ -4244,10 +4241,10 @@ class MockLuciBuildService extends _i1.Mock implements _i17.LuciBuildService {
 
   @override
   _i13.Future<bool> rerunBuilder({
-    required _i32.CommitRef? commit,
+    required _i33.CommitRef? commit,
     required _i28.Target? target,
-    required _i33.Task? task,
-    Iterable<_i36.BuildTag>? tags = const [],
+    required _i34.Task? task,
+    Iterable<_i37.BuildTag>? tags = const [],
   }) =>
       (super.noSuchMethod(
             Invocation.method(#rerunBuilder, [], {
@@ -4262,8 +4259,8 @@ class MockLuciBuildService extends _i1.Mock implements _i17.LuciBuildService {
 
   @override
   _i13.Future<bool> rerunDartInternalReleaseBuilder({
-    required _i32.CommitRef? commit,
-    required _i33.Task? task,
+    required _i33.CommitRef? commit,
+    required _i34.Task? task,
   }) =>
       (super.noSuchMethod(
             Invocation.method(#rerunDartInternalReleaseBuilder, [], {
@@ -4278,7 +4275,7 @@ class MockLuciBuildService extends _i1.Mock implements _i17.LuciBuildService {
 /// A class which mocks [ProcessManager].
 ///
 /// See the documentation for Mockito's code generation for more information.
-class MockProcessManager extends _i1.Mock implements _i37.ProcessManager {
+class MockProcessManager extends _i1.Mock implements _i38.ProcessManager {
   MockProcessManager() {
     _i1.throwOnMissingStub(this);
   }
@@ -5438,7 +5435,7 @@ class MockScheduler extends _i1.Mock implements _i17.Scheduler {
   }
 
   @override
-  _i13.Future<void> addCommits(List<_i38.Commit>? commits) =>
+  _i13.Future<void> addCommits(List<_i39.Commit>? commits) =>
       (super.noSuchMethod(
             Invocation.method(#addCommits, [commits]),
             returnValue: _i13.Future<void>.value(),
@@ -5508,7 +5505,7 @@ class MockScheduler extends _i1.Mock implements _i17.Scheduler {
 
   @override
   _i13.Future<void> handleMergeGroupEvent({
-    required _i31.MergeGroupEvent? mergeGroupEvent,
+    required _i32.MergeGroupEvent? mergeGroupEvent,
   }) =>
       (super.noSuchMethod(
             Invocation.method(#handleMergeGroupEvent, [], {
@@ -5541,7 +5538,7 @@ class MockScheduler extends _i1.Mock implements _i17.Scheduler {
           as _i13.Future<void>);
 
   @override
-  _i13.Future<void> processWorkflowJob(_i39.WorkflowJobEvent? event) =>
+  _i13.Future<void> processWorkflowJob(_i40.WorkflowJobEvent? event) =>
       (super.noSuchMethod(
             Invocation.method(#processWorkflowJob, [event]),
             returnValue: _i13.Future<void>.value(),
@@ -5554,7 +5551,7 @@ class MockScheduler extends _i1.Mock implements _i17.Scheduler {
     String? baseRef,
     _i7.RepositorySlug? slug,
     String? headSha,
-    dynamic stage,
+    _i30.CiStage? stage,
   ) =>
       (super.noSuchMethod(
             Invocation.method(#getMergeGroupTargetsForStage, [
@@ -5572,7 +5569,7 @@ class MockScheduler extends _i1.Mock implements _i17.Scheduler {
     String? baseRef,
     _i7.RepositorySlug? slug,
     String? headSha, {
-    _i40.CiType? type = _i40.CiType.any,
+    _i41.CiType? type = _i41.CiType.any,
   }) =>
       (super.noSuchMethod(
             Invocation.method(
@@ -5664,7 +5661,7 @@ class MockScheduler extends _i1.Mock implements _i17.Scheduler {
   @override
   _i13.Future<List<_i28.Target>> getPresubmitTargets(
     _i7.PullRequest? pullRequest, {
-    _i40.CiType? type = _i40.CiType.any,
+    _i41.CiType? type = _i41.CiType.any,
   }) =>
       (super.noSuchMethod(
             Invocation.method(
@@ -5678,7 +5675,7 @@ class MockScheduler extends _i1.Mock implements _i17.Scheduler {
 
   @override
   _i13.Future<bool> processCheckRunCompleted(
-    _i31.CheckRun? checkRun,
+    _i32.CheckRun? checkRun,
     _i7.RepositorySlug? slug,
   ) =>
       (super.noSuchMethod(
@@ -5688,7 +5685,21 @@ class MockScheduler extends _i1.Mock implements _i17.Scheduler {
           as _i13.Future<bool>);
 
   @override
-  bool detectMergeGroup(_i31.CheckRun? checkRun) =>
+  _i13.Future<bool> processUnifiedCheckRunCompleted(
+    _i6.Build? build,
+    _i31.PresubmitUserData? userData,
+  ) =>
+      (super.noSuchMethod(
+            Invocation.method(#processUnifiedCheckRunCompleted, [
+              build,
+              userData,
+            ]),
+            returnValue: _i13.Future<bool>.value(false),
+          )
+          as _i13.Future<bool>);
+
+  @override
+  bool detectMergeGroup(_i32.CheckRun? checkRun) =>
       (super.noSuchMethod(
             Invocation.method(#detectMergeGroup, [checkRun]),
             returnValue: false,
@@ -5697,7 +5708,7 @@ class MockScheduler extends _i1.Mock implements _i17.Scheduler {
 
   @override
   _i13.Future<void> proceedToCiTestingStage({
-    required _i31.CheckRun? checkRun,
+    required _i32.CheckRun? checkRun,
     required _i7.RepositorySlug? slug,
     required String? sha,
     required String? mergeQueueGuard,
@@ -5717,19 +5728,19 @@ class MockScheduler extends _i1.Mock implements _i17.Scheduler {
           as _i13.Future<void>);
 
   @override
-  _i13.Future<_i41.ProcessCheckRunResult> processCheckRun(
-    _i31.CheckRunEvent? checkRunEvent,
+  _i13.Future<_i42.ProcessCheckRunResult> processCheckRun(
+    _i32.CheckRunEvent? checkRunEvent,
   ) =>
       (super.noSuchMethod(
             Invocation.method(#processCheckRun, [checkRunEvent]),
-            returnValue: _i13.Future<_i41.ProcessCheckRunResult>.value(
-              _i20.dummyValue<_i41.ProcessCheckRunResult>(
+            returnValue: _i13.Future<_i42.ProcessCheckRunResult>.value(
+              _i20.dummyValue<_i42.ProcessCheckRunResult>(
                 this,
                 Invocation.method(#processCheckRun, [checkRunEvent]),
               ),
             ),
           )
-          as _i13.Future<_i41.ProcessCheckRunResult>);
+          as _i13.Future<_i42.ProcessCheckRunResult>);
 
   @override
   _i7.CheckRun checkRunFromString(String? input) =>