diff --git a/app_dart/lib/src/model/firestore/ci_staging.dart b/app_dart/lib/src/model/firestore/ci_staging.dart
index 7a7e145ad3..75dc596184 100644
--- a/app_dart/lib/src/model/firestore/ci_staging.dart
+++ b/app_dart/lib/src/model/firestore/ci_staging.dart
@@ -88,7 +88,8 @@ class CiStaging extends Document {
     required String checkRun,
     required String conclusion,
   }) async {
-    final logCrumb = 'markConclusion(${slug.owner}_${slug.name}_${sha}_$stage, $checkRun, $conclusion)';
+    final changeCrumb = '${slug.owner}_${slug.name}_$sha';
+    final logCrumb = 'markConclusion(${changeCrumb}_$stage, $checkRun, $conclusion)';
 
     // Marking needs to happen while in a transaction to ensure `remaining` is
     // updated correctly. For that to happen correctly; we need to perform a
@@ -110,8 +111,10 @@ class CiStaging extends Document {
 
     var remaining = -1;
     var failed = -1;
+    var total = -1;
     bool valid = false;
     String? checkRunGuard;
+    String? recordedConclusion;
 
     late final Document doc;
 
@@ -146,9 +149,15 @@ class CiStaging extends Document {
       }
       failed = maybeFailed;
 
+      final maybeTotal = int.tryParse(fields[kTotalField]?.integerValue ?? '');
+      if (maybeTotal == null) {
+        throw '$logCrumb: missing field "$kTotalField" for $transaction / ${doc.fields}';
+      }
+      total = maybeTotal;
+
       // We will have check_runs scheduled after the engine was built successfully, so missing the checkRun field
       // is an OK response to have. All fields should have been written at creation time.
-      final recordedConclusion = fields[checkRun]?.stringValue;
+      recordedConclusion = fields[checkRun]?.stringValue;
       if (recordedConclusion == null) {
         log.info('$logCrumb: $checkRun not present in doc for $transaction / $doc');
         await docRes.rollback(RollbackRequest(transaction: transaction), kDatabase);
@@ -157,6 +166,8 @@ class CiStaging extends Document {
           remaining: remaining,
           checkRunGuard: null,
           failed: failed,
+          summary: 'Check run "$checkRun" not present in $stage CI stage',
+          details: 'Change $changeCrumb',
         );
       }
 
@@ -207,7 +218,7 @@ class CiStaging extends Document {
       fields[checkRun] = Value(stringValue: conclusion);
       fields[kRemainingField] = Value(integerValue: '$remaining');
       fields[kFailedField] = Value(integerValue: '$failed');
-    } on DetailedApiRequestError catch (e) {
+    } on DetailedApiRequestError catch (e, stack) {
       if (e.status == 404) {
         // An attempt to read a document not in firestore should not be retried.
         log.info('$logCrumb: staging document not found for $transaction');
@@ -217,6 +228,15 @@ class CiStaging extends Document {
           remaining: -1,
           checkRunGuard: null,
           failed: failed,
+          summary: 'Internal server error',
+          details: '''
+Staging document not found for CI stage "$stage" for $changeCrumb. Got 404 from
+Firestore.
+
+Error:
+${e.toString()}
+$stack
+''',
         );
       }
       // All other errors should bubble up and be retried.
@@ -239,6 +259,15 @@ class CiStaging extends Document {
       remaining: remaining,
       checkRunGuard: checkRunGuard,
       failed: failed,
+      summary: valid ? 'All tests passed' : 'Not a valid state transition for $checkRun',
+      details: valid
+          ? '''
+For CI stage $stage:
+  Total check runs scheduled: $total
+  Pending: $remaining
+  Failed: $failed
+'''
+          : 'Attempted to transition the state of check run $checkRun from "$recordedConclusion" to "$conclusion".',
     );
   }
 
@@ -343,12 +372,16 @@ class StagingConclusion {
   final int remaining;
   final String? checkRunGuard;
   final int failed;
+  final String summary;
+  final String details;
 
   const StagingConclusion({
     required this.result,
     required this.remaining,
     required this.checkRunGuard,
     required this.failed,
+    required this.summary,
+    required this.details,
   });
 
   bool get isOk => result == StagingConclusionResult.ok;
@@ -366,8 +399,21 @@ class StagingConclusion {
           other.result == result &&
           other.remaining == remaining &&
           other.checkRunGuard == checkRunGuard &&
-          other.failed == failed);
+          other.failed == failed &&
+          other.summary == summary &&
+          other.details == details);
+
+  @override
+  int get hashCode => Object.hashAll([
+        result,
+        remaining,
+        checkRunGuard,
+        failed,
+        summary,
+        details,
+      ]);
 
   @override
-  int get hashCode => Object.hashAll([result, remaining, checkRunGuard, failed]);
+  String toString() =>
+      'StagingConclusion("$result", "$remaining", "$checkRunGuard", "$failed", "$summary", "$details")';
 }
diff --git a/app_dart/lib/src/service/config.dart b/app_dart/lib/src/service/config.dart
index 4f46b7a9f9..0350580152 100644
--- a/app_dart/lib/src/service/config.dart
+++ b/app_dart/lib/src/service/config.dart
@@ -32,11 +32,37 @@ const String kDefaultBranchName = 'master';
 class Config {
   Config(this._db, this._cache);
 
-  /// Labels autosubmit looks for on pull requests
+  /// When present on a pull request, instructs Cocoon to submit it
+  /// automatically as soon as all the required checks pass.
   ///
   /// Keep this in sync with the similar `Config` class in `auto_submit`.
   static const String kAutosubmitLabel = 'autosubmit';
 
+  /// When present on a pull request, allows it to land without passing all the
+  /// checks, and jumps the merge queue.
+  ///
+  /// Keep this in sync with the similar `Config` class in `auto_submit`.
+  static const String kEmergencyLabel = 'emergency';
+
+  /// Validates that CI tasks were successfully created from the .ci.yaml file.
+  ///
+  /// If this check fails, it means Cocoon failed to fully populate the list of
+  /// CI checks and the PR/commit should be treated as failing.
+  static const String kCiYamlCheckName = 'ci.yaml validation';
+
+  /// A required check that stays in pending state until a sufficient subset of
+  /// checks pass.
+  ///
+  /// This check is "required", meaning that it must pass before Github will
+  /// allow a PR to land in the merge queue, or a merge group to land on the
+  /// target branch (main or master).
+  ///
+  /// IMPORTANT: the name of this task - "Merge Queue Guard" - must strictly
+  /// match the name of the required check configured in the repo settings.
+  /// Changing the name here or in the settings alone will break the PR
+  /// workflow.
+  static const String kMergeQueueLockName = 'Merge Queue Guard';
+
   final DatastoreDB _db;
 
   final CacheService _cache;
@@ -150,7 +176,6 @@ class Config {
 
   // GitHub App properties.
   Future<String> get githubPrivateKey => _getSingleValue('githubapp_private_pem');
-  Future<String> get overrideTreeStatusLabel => _getSingleValue('override_tree_status_label');
   Future<String> get githubPublicKey => _getSingleValue('githubapp_public_pem');
   Future<String> get githubAppId => _getSingleValue('githubapp_id');
   Future<Map<String, dynamic>> get githubAppInstallations async {
diff --git a/app_dart/lib/src/service/scheduler.dart b/app_dart/lib/src/service/scheduler.dart
index 1d48b1ce5b..22558103ec 100644
--- a/app_dart/lib/src/service/scheduler.dart
+++ b/app_dart/lib/src/service/scheduler.dart
@@ -101,28 +101,9 @@ class Scheduler {
   /// Name of the subcache to store scheduler related values in redis.
   static const String subcacheName = 'scheduler';
 
-  /// Validates that CI tasks were successfully created from the .ci.yaml file.
-  ///
-  /// If this check fails, it means Cocoon failed to fully populate the list of
-  /// CI checks and the PR/commit should be treated as failing.
-  static const String kCiYamlCheckName = 'ci.yaml validation';
-
-  /// A required check that stays in pending state until a sufficient subset of
-  /// checks pass.
-  ///
-  /// This check is "required", meaning that it must pass before Github will
-  /// allow a PR to land in the merge queue, or a merge group to land on the
-  /// target branch (main or master).
-  ///
-  /// IMPORTANT: the name of this task - "Merge Queue Guard" - must strictly
-  /// match the name of the required check configured in the repo settings.
-  /// Changing the name here or in the settings alone will break the PR
-  /// workflow.
-  static const String kMergeQueueLockName = 'Merge Queue Guard';
-
   /// List of check runs that do not need to be tracked or looked up in
   /// any staging logic.
-  static const kCheckRunsToIgnore = [kMergeQueueLockName, kCiYamlCheckName];
+  static const kCheckRunsToIgnore = [Config.kMergeQueueLockName, Config.kCiYamlCheckName];
 
   /// Briefly describes what the "Merge Queue Guard" check is for.
   ///
@@ -483,9 +464,11 @@ class Scheduler {
     // Update validate ci.yaml check
     await closeCiYamlCheckRun('PR ${pullRequest.number}', exception, slug, ciValidationCheckRun);
 
-    // The 'lock' will be unlocked later in processCheckRunCompletion after all engine builds are processed.
+    // Normally the lock stays pending until the PR is ready to be enqueued, but
+    // there are situations (see code above) when it needs to be unlocked
+    // immediately.
     if (unlockMergeGroup) {
-      await unlockMergeGroupChecks(slug, pullRequest.head!.sha!, lock, exception);
+      await unlockMergeQueueGuard(slug, pullRequest.head!.sha!, lock);
     }
     log.info(
       'Finished triggering builds for: pr ${pullRequest.number}, commit ${pullRequest.base!.sha}, branch ${pullRequest.head!.ref} and slug $slug}',
@@ -510,7 +493,7 @@ class Scheduler {
         conclusion: CheckRunConclusion.success,
       );
     } else {
-      log.warning('Marking $description $kCiYamlCheckName as failed', e);
+      log.warning('Marking $description ${Config.kCiYamlCheckName} as failed', e);
       // Failure when validating ci.yaml
       await githubChecksService.githubChecksUtil.updateCheckRun(
         config,
@@ -519,7 +502,7 @@ class Scheduler {
         status: CheckRunStatus.completed,
         conclusion: CheckRunConclusion.failure,
         output: CheckRunOutput(
-          title: kCiYamlCheckName,
+          title: Config.kCiYamlCheckName,
           summary: '.ci.yaml has failures',
           text: exception.toString(),
         ),
@@ -533,9 +516,9 @@ class Scheduler {
       config,
       slug,
       pullRequest.head!.sha!,
-      kCiYamlCheckName,
+      Config.kCiYamlCheckName,
       output: const CheckRunOutput(
-        title: kCiYamlCheckName,
+        title: Config.kCiYamlCheckName,
         summary: 'If this check is stuck pending, push an empty commit to retrigger the checks',
       ),
     );
@@ -579,7 +562,7 @@ class Scheduler {
     // close the ci.yaml validation and merge group guard.
     if (!isFusion) {
       await closeCiYamlCheckRun('MQ $slug/$headSha', null, slug, ciValidationCheckRun);
-      await unlockMergeGroupChecks(slug, headSha, lock, null);
+      await unlockMergeQueueGuard(slug, headSha, lock);
       return;
     }
 
@@ -709,51 +692,57 @@ class Scheduler {
       config,
       slug,
       headSha,
-      kMergeQueueLockName,
+      Config.kMergeQueueLockName,
       output: const CheckRunOutput(
-        title: kMergeQueueLockName,
+        title: Config.kMergeQueueLockName,
         summary: kMergeQueueLockDescription,
       ),
     );
   }
 
-  /// Completes the "Merge Queue Guard" check that was scheduled using
-  /// [lockMergeGroupChecks] with either success or failure.
+  /// Completes the "Merge Queue Guard" check run.
   ///
-  /// If [exception] is null completed the check with success. Otherwise,
-  /// completes the check with failure.
+  /// If the guard is guarding a merge group, this immediately makes the merge
+  /// group eligible for landing onto the target branch (e.g. master), depending
+  /// on the success of the merge groups queued in front of this one.
   ///
-  /// Calling this method unlocks the merge group, allowing Github to either
-  /// merge the respective PR into the target branch (if success), or remove the
-  /// PR from the merge queue (if failure).
-  Future<void> unlockMergeGroupChecks(RepositorySlug slug, String headSha, CheckRun lock, Object? exception) async {
-    if (exception == null) {
-      // All checks have passed. Unlocking Github with success.
-      log.info('All required tests passed for $headSha');
-      await githubChecksService.githubChecksUtil.updateCheckRun(
-        config,
-        slug,
-        lock,
-        status: CheckRunStatus.completed,
-        conclusion: CheckRunConclusion.success,
-      );
-    } else {
-      // Some checks failed. Unlocking Github with failure.
-      log.info('Some required tests failed for $headSha');
-      log.warning(exception.toString());
-      await githubChecksService.githubChecksUtil.updateCheckRun(
-        config,
-        slug,
-        lock,
-        status: CheckRunStatus.completed,
-        conclusion: CheckRunConclusion.failure,
-        output: CheckRunOutput(
-          title: kCiYamlCheckName,
-          summary: 'Some required tests failed for $headSha',
-          text: exception.toString(),
-        ),
-      );
-    }
+  /// If the guard is guarding a pull request, this immediately makes the pull
+  /// request eligible for enqueuing into the merge queue.
+  Future<void> unlockMergeQueueGuard(RepositorySlug slug, String headSha, CheckRun lock) async {
+    log.info('Unlocking Merge Queue Guard for $slug/$headSha');
+    await githubChecksService.githubChecksUtil.updateCheckRun(
+      config,
+      slug,
+      lock,
+      status: CheckRunStatus.completed,
+      conclusion: CheckRunConclusion.success,
+    );
+  }
+
+  /// Fails the "Merge Queue Guard" check for a merge group.
+  ///
+  /// This removes the merge group from the merge queue without landing it. The
+  /// corresponding pull request will have to be fixed and re-enqueued again.
+  Future<void> failGuardForMergeGroup(
+    RepositorySlug slug,
+    String headSha,
+    String summary,
+    String details,
+    CheckRun lock,
+  ) async {
+    log.info('Failing merge group guard for merge group $headSha in $slug');
+    await githubChecksService.githubChecksUtil.updateCheckRun(
+      config,
+      slug,
+      lock,
+      status: CheckRunStatus.completed,
+      conclusion: CheckRunConclusion.failure,
+      output: CheckRunOutput(
+        title: Config.kCiYamlCheckName,
+        summary: summary,
+        text: details,
+      ),
+    );
   }
 
   /// If [builderTriggerList] is specificed, return only builders that are contained in [presubmitTarget].
@@ -888,22 +877,29 @@ class Scheduler {
     return false;
   }
 
-  /// Process completed GitHub `check_run` to enable fusion engine builds.
+  /// Process a completed GitHub `check_run`.
+  ///
+  /// Handles both fusion engine build and test stages, and both pull requests
+  /// and merge groups.
   Future<bool> processCheckRunCompletion(cocoon_checks.CheckRunEvent checkRunEvent) async {
-    final name = checkRunEvent.checkRun?.name;
-    final sha = checkRunEvent.checkRun?.headSha;
+    final checkRun = checkRunEvent.checkRun!;
+    final name = checkRun.name;
+    final sha = checkRun.headSha;
     final slug = checkRunEvent.repository?.slug();
-    final conclusion = checkRunEvent.checkRun?.conclusion;
+    final conclusion = checkRun.conclusion;
 
     if (name == null || sha == null || slug == null || conclusion == null || kCheckRunsToIgnore.contains(name)) {
       return true;
     }
 
+    final logCrumb = 'checkCompleted($name, $slug, $sha, $conclusion)';
+
     final isFusion = await fusionTester.isFusionBasedRef(slug, sha);
     if (!isFusion) {
       return true;
     }
-    final logCrumb = 'checkCompleted($name, $slug, $sha, $conclusion)';
+
+    final isMergeGroup = detectMergeGroup(checkRun);
 
     firestoreService = await config.createFirestoreService();
 
@@ -938,23 +934,50 @@ class Scheduler {
       return false;
     }
 
-    // Are their tests remaining? Then we shouldn't unblock guard yet.
+    // If an internal error happened in Cocoon, we need human assistance to
+    // figure out next steps.
+    if (stagingConclusion.result == StagingConclusionResult.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) {
+        final guard = checkRunFromString(stagingConclusion.checkRunGuard!);
+        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;
     }
 
-    // Only report failure into the merge queue guard for engine build stage.
-    // Until https://github.com/flutter/flutter/issues/159898 is fixed, the
-    // merge queue guard ignores the `fusionTests` stage.
-    if (stage == CiStage.fusionEngineBuild && stagingConclusion.isFailed) {
-      await _reportCiStageFailure(
-        conclusion: stagingConclusion,
-        slug: slug,
-        sha: sha,
-        stage: stage,
-        logCrumb: logCrumb,
-      );
+    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) {
+        final guard = checkRunFromString(stagingConclusion.checkRunGuard!);
+        await failGuardForMergeGroup(
+          slug,
+          sha,
+          stagingConclusion.summary,
+          stagingConclusion.details,
+          guard,
+        );
+      }
       return true;
     }
 
@@ -962,30 +985,41 @@ class Scheduler {
     //
     // * 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 and land it.
+    //    * 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:
-        return _closeSuccessfulEngineBuildStage(
-          checkRunEvent: checkRunEvent,
+        await _closeSuccessfulEngineBuildStage(
+          checkRun: checkRun,
           mergeQueueGuard: stagingConclusion.checkRunGuard!,
           slug: slug,
           sha: sha,
           logCrumb: logCrumb,
         );
       case CiStage.fusionTests:
-        return _closeSuccessfulTestStage(
+        await _closeSuccessfulTestStage(
           mergeQueueGuard: stagingConclusion.checkRunGuard!,
           slug: slug,
           sha: sha,
           logCrumb: logCrumb,
         );
     }
+    return true;
+  }
+
+  /// Whether the [checkRunEvent] is for a merge group (rather than a pull request).
+  bool detectMergeGroup(cocoon_checks.CheckRun checkRun) {
+    final headBranch = checkRun.checkSuite?.headBranch;
+    if (headBranch == null) {
+      return false;
+    }
+    return tryParseGitHubMergeQueueBranch(headBranch).parsed;
   }
 
-  Future<bool> _closeSuccessfulEngineBuildStage({
-    required cocoon_checks.CheckRunEvent checkRunEvent,
+  Future<void> _closeSuccessfulEngineBuildStage({
+    required cocoon_checks.CheckRun checkRun,
     required String mergeQueueGuard,
     required RepositorySlug slug,
     required String sha,
@@ -994,9 +1028,7 @@ class Scheduler {
     // 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
-    final headBranch = checkRunEvent.checkRun?.checkSuite?.headBranch;
-    final isInMergeQueue = headBranch?.startsWith('gh-readonly-queue/') ?? false;
-    if (isInMergeQueue) {
+    if (detectMergeGroup(checkRun)) {
       await _closeMergeQueue(
         mergeQueueGuard: mergeQueueGuard,
         slug: slug,
@@ -1004,46 +1036,28 @@ class Scheduler {
         stage: CiStage.fusionEngineBuild,
         logCrumb: logCrumb,
       );
-      return true;
+      return;
     }
 
     log.info('$logCrumb: Stage completed successfully: ${CiStage.fusionEngineBuild}');
 
     await _proceedToCiTestingStage(
-      checkRunEvent: checkRunEvent,
+      checkRun: checkRun,
       mergeQueueGuard: mergeQueueGuard,
       slug: slug,
       sha: sha,
       logCrumb: logCrumb,
     );
-    return true;
   }
 
-  Future<bool> _closeSuccessfulTestStage({
+  Future<void> _closeSuccessfulTestStage({
     required String mergeQueueGuard,
     required RepositorySlug slug,
     required String sha,
     required String logCrumb,
   }) async {
     log.info('$logCrumb: Stage completed: ${CiStage.fusionTests}');
-
-    // TODO: Unlock the guarding check_run after confirming that the test stage
-    //       document is tracking all check runs correctly.
-    // IMPORTANT: when moving the unlock here, REMEMBER to remove the unlock in
-    //            _proceedToCiTestingStage for non-MQ runs. MQ should unlock the
-    //            guard right after the build stage.
-    log.info('''
-Emulate:
-
-await unlockMergeGroupChecks(
-  slug = $slug,
-  sha = $sha,
-  mergeQueueGuard = $mergeQueueGuard,
-  null,
-);
-''');
-
-    return true;
+    await unlockMergeQueueGuard(slug, sha, checkRunFromString(mergeQueueGuard));
   }
 
   /// Returns the presubmit targets for the fusion repo [pullRequest] that should run for the given [stage].
@@ -1071,25 +1085,11 @@ await unlockMergeGroupChecks(
 
     // Unlock the guarding check_run.
     final checkRunGuard = checkRunFromString(mergeQueueGuard);
-    await unlockMergeGroupChecks(slug, sha, checkRunGuard, null);
-  }
-
-  Future<void> _reportCiStageFailure({
-    required RepositorySlug slug,
-    required String sha,
-    required StagingConclusion conclusion,
-    required CiStage stage,
-    required String logCrumb,
-  }) async {
-    log.info('$logCrumb: Stage failed: $stage with failed=${conclusion.failed}');
-
-    // Unlock the guarding check_run.
-    final checkRunGuard = checkRunFromString(conclusion.checkRunGuard!);
-    await unlockMergeGroupChecks(slug, sha, checkRunGuard, 'failed ${conclusion.failed} tests');
+    await unlockMergeQueueGuard(slug, sha, checkRunGuard);
   }
 
   Future<void> _proceedToCiTestingStage({
-    required cocoon_checks.CheckRunEvent checkRunEvent,
+    required cocoon_checks.CheckRun checkRun,
     required RepositorySlug slug,
     required String sha,
     required String mergeQueueGuard,
@@ -1099,8 +1099,8 @@ await unlockMergeGroupChecks(
 
     // Look up the PR in our cache first. This reduces github quota and requires less calls.
     PullRequest? pullRequest;
-    final id = checkRunEvent.checkRun!.id!;
-    final name = checkRunEvent.checkRun!.name!;
+    final id = checkRun.id!;
+    final name = checkRun.name!;
     try {
       pullRequest = await findPullRequestFor(
         firestoreService,
@@ -1113,7 +1113,7 @@ await unlockMergeGroupChecks(
 
     // We'va failed to find the pull request; try a reverse look it from the check suite.
     if (pullRequest == null) {
-      final int checkSuiteId = checkRunEvent.checkRun!.checkSuite!.id!;
+      final int checkSuiteId = checkRun.checkSuite!.id!;
       pullRequest = await githubChecksService.findMatchingPullRequest(slug, sha, checkSuiteId);
     }
 
@@ -1122,7 +1122,6 @@ await unlockMergeGroupChecks(
       throw 'No PR found matching this check_run($id, $name)';
     }
 
-    Object? exception;
     try {
       // Both the author and label should be checked to make sure that no one is
       // attempting to get a pull request without check through.
@@ -1155,18 +1154,15 @@ await unlockMergeGroupChecks(
         error,
         backtrace,
       );
-      exception = error;
+      rethrow;
     } catch (error, backtrace) {
       log.warning(
         '$logCrumb: Exception encountered when scheduling presubmit targets for ${pullRequest.number}',
         error,
         backtrace,
       );
-      exception = error;
+      rethrow;
     }
-
-    // Unlock the guarding check_run.
-    await unlockMergeGroupChecks(slug, sha, checkRunGuard, exception);
   }
 
   Future<StagingConclusion> _recordCurrentCiStage({
@@ -1205,7 +1201,7 @@ await unlockMergeGroupChecks(
   /// generated when someone clicks the re-run button from a failed build from
   /// the Github UI.
   ///
-  /// If the rerequested check is for [kCiYamlCheckName], all presubmit jobs are retried.
+  /// If the rerequested check is for [Config.kCiYamlCheckName], all presubmit jobs are retried.
   /// Otherwise, the specific check will be retried.
   ///
   /// Relevant APIs:
@@ -1220,12 +1216,12 @@ await unlockMergeGroupChecks(
         log.fine('Rerun requested by GitHub user: ${checkRunEvent.sender?.login}');
         final String? name = checkRunEvent.checkRun!.name;
         bool success = false;
-        if (name == kMergeQueueLockName) {
+        if (name == Config.kMergeQueueLockName) {
           final RepositorySlug slug = checkRunEvent.repository!.slug();
           final int checkSuiteId = checkRunEvent.checkRun!.checkSuite!.id!;
-          log.fine('Requested re-run of "$kMergeQueueLockName" for $slug / $checkSuiteId - ignoring');
+          log.fine('Requested re-run of "${Config.kMergeQueueLockName}" for $slug / $checkSuiteId - ignoring');
           success = true;
-        } else if (name == kCiYamlCheckName) {
+        } else if (name == Config.kCiYamlCheckName) {
           // The CheckRunEvent.checkRun.pullRequests array is empty for this
           // event, so we need to find the matching pull request.
           final RepositorySlug slug = checkRunEvent.repository!.slug();
diff --git a/app_dart/test/model/firestore/ci_staging_test.dart b/app_dart/test/model/firestore/ci_staging_test.dart
index 1659ae3821..ed5dfc0a4b 100644
--- a/app_dart/test/model/firestore/ci_staging_test.dart
+++ b/app_dart/test/model/firestore/ci_staging_test.dart
@@ -186,6 +186,8 @@ void main() {
             result: StagingConclusionResult.missing,
             failed: 0,
             checkRunGuard: null,
+            summary: 'Check run "test" not present in engine CI stage',
+            details: 'Change flutter_flutter_1234',
           ),
         );
         verify(docRes.rollback(argThat(predicate((RollbackRequest t) => t.transaction == kTransaction)), kDatabase))
@@ -208,6 +210,7 @@ void main() {
           (_) async => Document(
             name: expectedName,
             fields: {
+              CiStaging.kTotalField: Value(integerValue: '1'),
               CiStaging.kRemainingField: Value(integerValue: '1'),
               CiStaging.kFailedField: Value(integerValue: '0'),
               CiStaging.kCheckRunGuardField: Value(stringValue: '{}'),
@@ -234,7 +237,7 @@ void main() {
               predicate((CommitRequest t) {
                 return t.transaction == kTransaction &&
                     t.writes!.length == 1 &&
-                    t.writes!.first.update!.fields!.length == 4 &&
+                    t.writes!.first.update!.fields!.length == 5 &&
                     t.writes!.first.update!.fields!['Linux build_test']!.stringValue == 'mulligan' &&
                     t.writes!.first.update!.fields![CiStaging.kRemainingField]!.integerValue == '0';
               }),
@@ -263,6 +266,7 @@ void main() {
             fields: {
               CiStaging.kRemainingField: Value(integerValue: '1'),
               CiStaging.kFailedField: Value(integerValue: '0'),
+              CiStaging.kTotalField: Value(integerValue: '1'),
               CiStaging.kCheckRunGuardField: Value(stringValue: '{}'),
               'Linux build_test': Value(stringValue: CiStaging.kScheduledValue),
             },
@@ -283,7 +287,19 @@ void main() {
         final result = await future;
         expect(
           result,
-          const StagingConclusion(remaining: 0, result: StagingConclusionResult.ok, failed: 0, checkRunGuard: '{}'),
+          const StagingConclusion(
+            remaining: 0,
+            result: StagingConclusionResult.ok,
+            failed: 0,
+            checkRunGuard: '{}',
+            summary: 'All tests passed',
+            details: '''
+For CI stage engine:
+  Total check runs scheduled: 1
+  Pending: 0
+  Failed: 0
+''',
+          ),
         );
         verify(
           docRes.commit(
@@ -291,7 +307,7 @@ void main() {
               predicate((CommitRequest t) {
                 return t.transaction == kTransaction &&
                     t.writes!.length == 1 &&
-                    t.writes!.first.update!.fields!.length == 4 &&
+                    t.writes!.first.update!.fields!.length == 5 &&
                     t.writes!.first.update!.fields!['Linux build_test']!.stringValue == 'mulligan' &&
                     t.writes!.first.update!.fields![CiStaging.kRemainingField]!.integerValue == '0';
               }),
@@ -320,6 +336,7 @@ void main() {
             fields: {
               CiStaging.kRemainingField: Value(integerValue: '1'),
               CiStaging.kFailedField: Value(integerValue: '0'),
+              CiStaging.kTotalField: Value(integerValue: '1'),
               CiStaging.kCheckRunGuardField: Value(stringValue: '{}'),
               'MacOS build_test': Value(stringValue: CiStaging.kSuccessValue),
             },
@@ -345,6 +362,8 @@ void main() {
             result: StagingConclusionResult.internalError,
             failed: 0,
             checkRunGuard: '{}',
+            summary: 'Not a valid state transition for MacOS build_test',
+            details: 'Attempted to transition the state of check run MacOS build_test from "success" to "mulligan".',
           ),
         );
         verify(
@@ -353,7 +372,7 @@ void main() {
               predicate((CommitRequest t) {
                 return t.transaction == kTransaction &&
                     t.writes!.length == 1 &&
-                    t.writes!.first.update!.fields!.length == 4 &&
+                    t.writes!.first.update!.fields!.length == 5 &&
                     t.writes!.first.update!.fields!['MacOS build_test']!.stringValue == 'mulligan' &&
                     t.writes!.first.update!.fields![CiStaging.kRemainingField]!.integerValue == '1';
               }),
@@ -382,6 +401,7 @@ void main() {
             fields: {
               CiStaging.kRemainingField: Value(integerValue: '1'),
               CiStaging.kFailedField: Value(integerValue: '1'),
+              CiStaging.kTotalField: Value(integerValue: '1'),
               CiStaging.kCheckRunGuardField: Value(stringValue: '{}'),
               'MacOS build_test': Value(stringValue: CiStaging.kFailureValue),
             },
@@ -403,7 +423,19 @@ void main() {
         // Remaining == 1 because our test was already concluded.
         expect(
           result,
-          const StagingConclusion(remaining: 1, result: StagingConclusionResult.ok, failed: 0, checkRunGuard: '{}'),
+          const StagingConclusion(
+            remaining: 1,
+            result: StagingConclusionResult.ok,
+            failed: 0,
+            checkRunGuard: '{}',
+            summary: 'All tests passed',
+            details: '''
+For CI stage engine:
+  Total check runs scheduled: 1
+  Pending: 1
+  Failed: 0
+''',
+          ),
         );
         verify(
           docRes.commit(
@@ -411,7 +443,7 @@ void main() {
               predicate((CommitRequest t) {
                 return t.transaction == kTransaction &&
                     t.writes!.length == 1 &&
-                    t.writes!.first.update!.fields!.length == 4 &&
+                    t.writes!.first.update!.fields!.length == 5 &&
                     t.writes!.first.update!.fields!['MacOS build_test']!.stringValue == CiStaging.kSuccessValue &&
                     t.writes!.first.update!.fields![CiStaging.kRemainingField]!.integerValue == '1' &&
                     t.writes!.first.update!.fields![CiStaging.kFailedField]!.integerValue == '0';
@@ -441,6 +473,7 @@ void main() {
             fields: {
               CiStaging.kRemainingField: Value(integerValue: '1'),
               CiStaging.kFailedField: Value(integerValue: '1'),
+              CiStaging.kTotalField: Value(integerValue: '1'),
               CiStaging.kCheckRunGuardField: Value(stringValue: '{}'),
               'MacOS build_test': Value(stringValue: CiStaging.kFailureValue),
             },
@@ -466,6 +499,8 @@ void main() {
             result: StagingConclusionResult.internalError,
             failed: 1,
             checkRunGuard: '{}',
+            summary: 'Not a valid state transition for MacOS build_test',
+            details: 'Attempted to transition the state of check run MacOS build_test from "failure" to "failure".',
           ),
         );
         verify(
@@ -474,7 +509,7 @@ void main() {
               predicate((CommitRequest t) {
                 return t.transaction == kTransaction &&
                     t.writes!.length == 1 &&
-                    t.writes!.first.update!.fields!.length == 4 &&
+                    t.writes!.first.update!.fields!.length == 5 &&
                     t.writes!.first.update!.fields!['MacOS build_test']!.stringValue == CiStaging.kFailureValue &&
                     t.writes!.first.update!.fields![CiStaging.kRemainingField]!.integerValue == '1' &&
                     t.writes!.first.update!.fields![CiStaging.kFailedField]!.integerValue == '1';
@@ -504,6 +539,7 @@ void main() {
             fields: {
               CiStaging.kRemainingField: Value(integerValue: '1'),
               CiStaging.kFailedField: Value(integerValue: '0'),
+              CiStaging.kTotalField: Value(integerValue: '1'),
               CiStaging.kCheckRunGuardField: Value(stringValue: '{}'),
               'MacOS build_test': Value(stringValue: CiStaging.kSuccessValue),
             },
@@ -524,7 +560,19 @@ void main() {
         final result = await future;
         expect(
           result,
-          const StagingConclusion(remaining: 1, result: StagingConclusionResult.ok, failed: 1, checkRunGuard: '{}'),
+          const StagingConclusion(
+            remaining: 1,
+            result: StagingConclusionResult.ok,
+            failed: 1,
+            checkRunGuard: '{}',
+            summary: 'All tests passed',
+            details: '''
+For CI stage engine:
+  Total check runs scheduled: 1
+  Pending: 1
+  Failed: 1
+''',
+          ),
         );
         verify(
           docRes.commit(
@@ -532,7 +580,7 @@ void main() {
               predicate((CommitRequest t) {
                 return t.transaction == kTransaction &&
                     t.writes!.length == 1 &&
-                    t.writes!.first.update!.fields!.length == 4 &&
+                    t.writes!.first.update!.fields!.length == 5 &&
                     t.writes!.first.update!.fields!['MacOS build_test']!.stringValue == CiStaging.kFailureValue &&
                     t.writes!.first.update!.fields![CiStaging.kRemainingField]!.integerValue == '1' &&
                     t.writes!.first.update!.fields![CiStaging.kFailedField]!.integerValue == '1';
diff --git a/app_dart/test/request_handlers/github/webhook_subscription_test.dart b/app_dart/test/request_handlers/github/webhook_subscription_test.dart
index 760f091b21..21a5727cd1 100644
--- a/app_dart/test/request_handlers/github/webhook_subscription_test.dart
+++ b/app_dart/test/request_handlers/github/webhook_subscription_test.dart
@@ -2693,7 +2693,7 @@ void foo() {
           'triggerMergeGroupTargets(flutter/flutter, c9affbbb12aa40cb3afbe94b9ea6b119a256bebf, simulated): Scheduling merge group checks',
           'Updating ci.yaml validation check for MQ flutter/flutter/c9affbbb12aa40cb3afbe94b9ea6b119a256bebf',
           'ci.yaml validation check was successful for MQ flutter/flutter/c9affbbb12aa40cb3afbe94b9ea6b119a256bebf',
-          'All required tests passed for c9affbbb12aa40cb3afbe94b9ea6b119a256bebf',
+          'Unlocking Merge Queue Guard for flutter/flutter/c9affbbb12aa40cb3afbe94b9ea6b119a256bebf',
         ],
       );
     });
diff --git a/app_dart/test/service/scheduler_test.dart b/app_dart/test/service/scheduler_test.dart
index e615b8ecbb..4645a45ed7 100644
--- a/app_dart/test/service/scheduler_test.dart
+++ b/app_dart/test/service/scheduler_test.dart
@@ -184,7 +184,12 @@ void main() {
       mockGithubChecksUtil = MockGithubChecksUtil();
       // 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));
+          .thenAnswer((Invocation invocation) async {
+        return generateCheckRun(
+          invocation.positionalArguments[2].hashCode,
+          name: invocation.positionalArguments[3],
+        );
+      });
 
       fakeFusion = FakeFusionTester();
       callbacks = MockCallbacks();
@@ -726,12 +731,12 @@ targets:
           return CheckRun.fromJson(const <String, dynamic>{
             'id': 1,
             'started_at': '2020-05-10T02:49:31Z',
-            'name': Scheduler.kCiYamlCheckName,
+            'name': Config.kCiYamlCheckName,
             'check_suite': <String, dynamic>{'id': 2},
           });
         });
         final Map<String, dynamic> checkRunEventJson = jsonDecode(checkRunString) as Map<String, dynamic>;
-        checkRunEventJson['check_run']['name'] = Scheduler.kCiYamlCheckName;
+        checkRunEventJson['check_run']['name'] = Config.kCiYamlCheckName;
         final cocoon_checks.CheckRunEvent checkRunEvent = cocoon_checks.CheckRunEvent.fromJson(checkRunEventJson);
         expect(await scheduler.processCheckRun(checkRunEvent), true);
         verify(
@@ -739,7 +744,7 @@ targets:
             any,
             any,
             any,
-            Scheduler.kCiYamlCheckName,
+            Config.kCiYamlCheckName,
             output: anyNamed('output'),
           ),
         );
@@ -791,12 +796,12 @@ targets:
           return CheckRun.fromJson(const <String, dynamic>{
             'id': 1,
             'started_at': '2020-05-10T02:49:31Z',
-            'name': Scheduler.kCiYamlCheckName,
+            'name': Config.kCiYamlCheckName,
             'check_suite': <String, dynamic>{'id': 2},
           });
         });
         final Map<String, dynamic> checkRunEventJson = jsonDecode(checkRunString) as Map<String, dynamic>;
-        checkRunEventJson['check_run']['name'] = Scheduler.kMergeQueueLockName;
+        checkRunEventJson['check_run']['name'] = Config.kMergeQueueLockName;
         final cocoon_checks.CheckRunEvent checkRunEvent = cocoon_checks.CheckRunEvent.fromJson(checkRunEventJson);
         expect(await scheduler.processCheckRun(checkRunEvent), true);
         verifyNever(
@@ -804,7 +809,7 @@ targets:
             any,
             any,
             any,
-            Scheduler.kMergeQueueLockName,
+            Config.kMergeQueueLockName,
             output: anyNamed('output'),
           ),
         );
@@ -1005,6 +1010,8 @@ targets:
                 remaining: 1,
                 checkRunGuard: '{}',
                 failed: 0,
+                summary: 'Field missing',
+                details: 'Some details',
               );
             });
 
@@ -1047,6 +1054,8 @@ targets:
                 remaining: 1,
                 checkRunGuard: '{}',
                 failed: 0,
+                summary: 'Internal error',
+                details: 'Some details',
               );
             });
 
@@ -1097,6 +1106,8 @@ targets:
                 remaining: 1,
                 checkRunGuard: '{}',
                 failed: 0,
+                summary: 'OK',
+                details: 'Some details',
               );
             });
 
@@ -1131,7 +1142,11 @@ targets:
             );
           });
 
-          test('failed tests unlocks but does not schedule more', () async {
+          // The merge guard is not closed until both engine build and tests
+          // complete and are successful.
+          // This behavior is explained here:
+          // https://github.com/flutter/flutter/issues/159898#issuecomment-2597209435
+          test('failed tests neither unlock merge queue guard nor schedule test stage', () async {
             when(
               callbacks.markCheckRunConclusion(
                 firestoreService: anyNamed('firestoreService'),
@@ -1147,6 +1162,8 @@ targets:
                 remaining: 0,
                 checkRunGuard: checkRunFor(name: 'GUARD TEST'),
                 failed: 1,
+                summary: 'OK',
+                details: 'Some details',
               );
             });
 
@@ -1169,21 +1186,16 @@ targets:
               ),
             ).called(1);
 
-            verify(
+            verifyNever(
               mockGithubChecksUtil.updateCheckRun(
                 any,
-                argThat(equals(RepositorySlug('flutter', 'flutter'))),
-                argThat(
-                  predicate<CheckRun>((arg) {
-                    expect(arg.name, 'GUARD TEST');
-                    return true;
-                  }),
-                ),
-                status: argThat(equals(CheckRunStatus.completed), named: 'status'),
-                conclusion: argThat(equals(CheckRunConclusion.failure), named: 'conclusion'),
+                any,
+                any,
+                status: anyNamed('status'),
+                conclusion: anyNamed('conclusion'),
                 output: anyNamed('output'),
               ),
-            ).called(1);
+            );
           });
 
           test('schedules tests after engine stage', () async {
@@ -1264,6 +1276,8 @@ targets:
                 remaining: 0,
                 checkRunGuard: checkRunFor(name: 'GUARD TEST'),
                 failed: 0,
+                summary: 'OK',
+                details: 'Some details',
               );
             });
 
@@ -1289,21 +1303,16 @@ targets:
               ),
             ).called(1);
 
-            verify(
+            verifyNever(
               mockGithubChecksUtil.updateCheckRun(
                 any,
-                argThat(equals(RepositorySlug('flutter', 'flutter'))),
-                argThat(
-                  predicate<CheckRun>((arg) {
-                    expect(arg.name, 'GUARD TEST');
-                    return true;
-                  }),
-                ),
-                status: argThat(equals(CheckRunStatus.completed), named: 'status'),
-                conclusion: argThat(equals(CheckRunConclusion.success), named: 'conclusion'),
+                any,
+                any,
+                status: anyNamed('status'),
+                conclusion: anyNamed('conclusion'),
                 output: anyNamed('output'),
               ),
-            ).called(1);
+            );
 
             final result = verify(
               luci.scheduleTryBuilds(
@@ -1323,39 +1332,11 @@ targets:
           test('tracks test check runs in firestore', () async {
             final githubService = config.githubService = MockGithubService();
             final githubClient = MockGitHub();
-            when(githubService.github).thenReturn(githubClient);
-            when(githubService.searchIssuesAndPRs(any, any, sort: anyNamed('sort'), pages: anyNamed('pages')))
-                .thenAnswer((_) async => [generateIssue(42)]);
-
-            final pullRequest = generatePullRequest();
-            when(githubService.getPullRequest(any, any)).thenAnswer((_) async => pullRequest);
-            when(githubService.listFiles(any)).thenAnswer((_) async => ['abc/def']);
-            when(mockGithubChecksUtil.listCheckSuitesForRef(any, any, ref: anyNamed('ref'))).thenAnswer(
-              (_) async => [
-                // From check_run.check_suite.id in [checkRunString].
-                generateCheckSuite(668083231),
-              ],
-            );
-
-            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}');
-            });
             final luci = MockLuciBuildService();
-            when(luci.scheduleTryBuilds(targets: anyNamed('targets'), pullRequest: anyNamed('pullRequest')))
-                .thenAnswer((inv) async {
-              return [];
-            });
-
             final gitHubChecksService = MockGithubChecksService();
+
+            when(githubService.github).thenReturn(githubClient);
             when(gitHubChecksService.githubChecksUtil).thenReturn(mockGithubChecksUtil);
-            when(gitHubChecksService.findMatchingPullRequest(any, any, any)).thenAnswer((inv) async {
-              return pullRequest;
-            });
 
             scheduler = Scheduler(
               cache: cache,
@@ -1388,6 +1369,8 @@ targets:
                 remaining: 0,
                 checkRunGuard: checkRunFor(name: 'GUARD TEST'),
                 failed: 0,
+                summary: 'Field missing or OK',
+                details: 'Some details',
               );
             });
 
@@ -1425,44 +1408,34 @@ targets:
                 conclusion: argThat(equals('success'), named: 'conclusion'),
               ),
             ).called(1);
+
+            // Because tests completed, and completed successfully, the guard is
+            // unlocked, allowing the PR to land.
+            verify(
+              mockGithubChecksUtil.updateCheckRun(
+                any,
+                argThat(equals(RepositorySlug('flutter', 'flutter'))),
+                argThat(
+                  predicate<CheckRun>((arg) {
+                    expect(arg.name, 'GUARD TEST');
+                    return true;
+                  }),
+                ),
+                status: argThat(equals(CheckRunStatus.completed), named: 'status'),
+                conclusion: argThat(equals(CheckRunConclusion.success), named: 'conclusion'),
+                output: anyNamed('output'),
+              ),
+            ).called(1);
           });
 
           test('does not fail the merge queue guard when a test check run fails', () async {
             final githubService = config.githubService = MockGithubService();
             final githubClient = MockGitHub();
-            when(githubService.github).thenReturn(githubClient);
-            when(githubService.searchIssuesAndPRs(any, any, sort: anyNamed('sort'), pages: anyNamed('pages')))
-                .thenAnswer((_) async => [generateIssue(42)]);
-
-            final pullRequest = generatePullRequest();
-            when(githubService.getPullRequest(any, any)).thenAnswer((_) async => pullRequest);
-            when(githubService.listFiles(any)).thenAnswer((_) async => ['abc/def']);
-            when(mockGithubChecksUtil.listCheckSuitesForRef(any, any, ref: anyNamed('ref'))).thenAnswer(
-              (_) async => [
-                // From check_run.check_suite.id in [checkRunString].
-                generateCheckSuite(668083231),
-              ],
-            );
-
-            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}');
-            });
             final luci = MockLuciBuildService();
-            when(luci.scheduleTryBuilds(targets: anyNamed('targets'), pullRequest: anyNamed('pullRequest')))
-                .thenAnswer((inv) async {
-              return [];
-            });
-
             final gitHubChecksService = MockGithubChecksService();
+
+            when(githubService.github).thenReturn(githubClient);
             when(gitHubChecksService.githubChecksUtil).thenReturn(mockGithubChecksUtil);
-            when(gitHubChecksService.findMatchingPullRequest(any, any, any)).thenAnswer((inv) async {
-              return pullRequest;
-            });
 
             scheduler = Scheduler(
               cache: cache,
@@ -1498,6 +1471,8 @@ targets:
                   CiStage.fusionEngineBuild => 0,
                   CiStage.fusionTests => 1,
                 },
+                summary: 'Field missing or OK',
+                details: 'Some details',
               );
             });
 
@@ -1536,9 +1511,8 @@ targets:
               ),
             ).called(1);
 
-            // Only report failure into the merge queue guard for engine build stage.
-            // Until https://github.com/flutter/flutter/issues/159898 is fixed, the
-            // merge queue guard ignores the `fusionTests` stage.
+            // The test stage completed, but with failures. The merge queue
+            // guard should stay open to prevent the pull request from landing.
             verifyNever(
               mockGithubChecksUtil.updateCheckRun(
                 any,
@@ -1631,6 +1605,8 @@ targets:
                 remaining: 0,
                 checkRunGuard: checkRunFor(name: 'GUARD TEST'),
                 failed: 0,
+                summary: 'OK',
+                details: 'Some details',
               );
             });
 
@@ -1657,21 +1633,16 @@ targets:
               ),
             ).called(1);
 
-            verify(
+            verifyNever(
               mockGithubChecksUtil.updateCheckRun(
                 any,
-                argThat(equals(RepositorySlug('flutter', 'flutter'))),
-                argThat(
-                  predicate<CheckRun>((arg) {
-                    expect(arg.name, 'GUARD TEST');
-                    return true;
-                  }),
-                ),
-                status: argThat(equals(CheckRunStatus.completed), named: 'status'),
-                conclusion: argThat(equals(CheckRunConclusion.success), named: 'conclusion'),
+                any,
+                any,
+                status: anyNamed('status'),
+                conclusion: anyNamed('conclusion'),
                 output: anyNamed('output'),
               ),
-            ).called(1);
+            );
 
             final result = verify(
               luci.scheduleTryBuilds(
@@ -1883,14 +1854,14 @@ targets:
           verify(mockGithubChecksUtil.createCheckRun(any, any, any, captureAny, output: captureAnyNamed('output')))
               .captured,
           <Object?>[
-            Scheduler.kMergeQueueLockName,
+            Config.kMergeQueueLockName,
             const CheckRunOutput(
-              title: Scheduler.kMergeQueueLockName,
+              title: Config.kMergeQueueLockName,
               summary: Scheduler.kMergeQueueLockDescription,
             ),
-            Scheduler.kCiYamlCheckName,
+            Config.kCiYamlCheckName,
             const CheckRunOutput(
-              title: Scheduler.kCiYamlCheckName,
+              title: Config.kCiYamlCheckName,
               summary: 'If this check is stuck pending, push an empty commit to retrigger the checks',
             ),
             'Linux A',
@@ -1912,15 +1883,15 @@ targets:
           verify(mockGithubChecksUtil.createCheckRun(any, any, any, captureAny, output: captureAnyNamed('output')))
               .captured,
           <Object?>[
-            Scheduler.kMergeQueueLockName,
+            Config.kMergeQueueLockName,
             const CheckRunOutput(
-              title: Scheduler.kMergeQueueLockName,
+              title: Config.kMergeQueueLockName,
               summary: Scheduler.kMergeQueueLockDescription,
             ),
-            Scheduler.kCiYamlCheckName,
+            Config.kCiYamlCheckName,
             // No other targets should be created.
             const CheckRunOutput(
-              title: Scheduler.kCiYamlCheckName,
+              title: Config.kCiYamlCheckName,
               summary: 'If this check is stuck pending, push an empty commit to retrigger the checks',
             ),
           ],
@@ -2057,14 +2028,14 @@ targets:
           verify(mockGithubChecksUtil.createCheckRun(any, any, any, captureAny, output: captureAnyNamed('output')))
               .captured,
           <Object?>[
-            Scheduler.kMergeQueueLockName,
+            Config.kMergeQueueLockName,
             const CheckRunOutput(
-              title: Scheduler.kMergeQueueLockName,
+              title: Config.kMergeQueueLockName,
               summary: Scheduler.kMergeQueueLockDescription,
             ),
-            Scheduler.kCiYamlCheckName,
+            Config.kCiYamlCheckName,
             const CheckRunOutput(
-              title: Scheduler.kCiYamlCheckName,
+              title: Config.kCiYamlCheckName,
               summary: 'If this check is stuck pending, push an empty commit to retrigger the checks',
             ),
             'Linux A',
@@ -2085,14 +2056,14 @@ targets:
           verify(mockGithubChecksUtil.createCheckRun(any, any, any, captureAny, output: captureAnyNamed('output')))
               .captured,
           <Object?>[
-            Scheduler.kMergeQueueLockName,
+            Config.kMergeQueueLockName,
             const CheckRunOutput(
-              title: Scheduler.kMergeQueueLockName,
+              title: Config.kMergeQueueLockName,
               summary: Scheduler.kMergeQueueLockDescription,
             ),
-            Scheduler.kCiYamlCheckName,
+            Config.kCiYamlCheckName,
             const CheckRunOutput(
-              title: Scheduler.kCiYamlCheckName,
+              title: Config.kCiYamlCheckName,
               summary: 'If this check is stuck pending, push an empty commit to retrigger the checks',
             ),
             'Linux A',
@@ -2134,23 +2105,44 @@ targets:
           }
           throw Exception('Failed to find ${request.url.path}');
         });
+
+        final capturedUpdates = <(String, CheckRunStatus, CheckRunConclusion)>[];
+
+        when(
+          mockGithubChecksUtil.updateCheckRun(
+            any,
+            any,
+            any,
+            status: anyNamed('status'),
+            conclusion: anyNamed('conclusion'),
+            output: anyNamed('output'),
+          ),
+        ).thenAnswer((inv) async {
+          final CheckRun checkRun = inv.positionalArguments[2];
+          capturedUpdates.add(
+            (
+              checkRun.name!,
+              inv.namedArguments[#status],
+              inv.namedArguments[#conclusion],
+            ),
+          );
+        });
+
         await scheduler.triggerPresubmitTargets(pullRequest: pullRequest);
+
         expect(
-          verify(
-            mockGithubChecksUtil.updateCheckRun(
-              any,
-              any,
-              any,
-              status: captureAnyNamed('status'),
-              conclusion: captureAnyNamed('conclusion'),
-              output: anyNamed('output'),
+          capturedUpdates,
+          <(String, CheckRunStatus, CheckRunConclusion)>[
+            (
+              'ci.yaml validation',
+              CheckRunStatus.completed,
+              CheckRunConclusion.failure,
+            ),
+            (
+              'Merge Queue Guard',
+              CheckRunStatus.completed,
+              CheckRunConclusion.success,
             ),
-          ).captured,
-          <Object?>[
-            CheckRunStatus.completed,
-            CheckRunConclusion.failure,
-            CheckRunStatus.completed,
-            CheckRunConclusion.failure,
           ],
         );
       });
@@ -2173,7 +2165,7 @@ targets:
             CheckRunStatus.completed,
             CheckRunConclusion.failure,
             CheckRunStatus.completed,
-            CheckRunConclusion.failure,
+            CheckRunConclusion.success,
           ],
         );
       });
diff --git a/app_dart/test/src/datastore/fake_config.dart b/app_dart/test/src/datastore/fake_config.dart
index aa9c12d66f..96a37c5044 100644
--- a/app_dart/test/src/datastore/fake_config.dart
+++ b/app_dart/test/src/datastore/fake_config.dart
@@ -101,7 +101,6 @@ class FakeConfig implements Config {
   String? flutterGoldDraftChangeValue;
   String? flutterGoldStalePRValue;
   List<String>? supportedBranchesValue;
-  String? overrideTreeStatusLabelValue;
   Set<gh.RepositorySlug>? supportedReposValue;
   Set<gh.RepositorySlug>? postsubmitSupportedReposValue;
   Duration? githubRequestDelayValue;
@@ -261,9 +260,6 @@ class FakeConfig implements Config {
   @override
   Future<GithubService> createDefaultGitHubService() async => githubService!;
 
-  @override
-  Future<String> get overrideTreeStatusLabel async => overrideTreeStatusLabelValue!;
-
   @override
   String get defaultRecipeBundleRef => 'refs/heads/main';
 
diff --git a/auto_submit/lib/requests/check_pull_request.dart b/auto_submit/lib/requests/check_pull_request.dart
index ecfd92b1ee..9d82b7ca32 100644
--- a/auto_submit/lib/requests/check_pull_request.dart
+++ b/auto_submit/lib/requests/check_pull_request.dart
@@ -56,8 +56,6 @@ class CheckPullRequest extends CheckRequest {
 
     log.info('Processing ${messageList.length} messages');
 
-    final PullRequestValidationService validationService = PullRequestValidationService(config);
-
     final List<Future<void>> futures = <Future<void>>[];
 
     for (pub.ReceivedMessage message in messageList) {
@@ -92,6 +90,7 @@ class CheckPullRequest extends CheckRequest {
         processingLog.add(pullRequest.number!);
       }
 
+      final PullRequestValidationService validationService = PullRequestValidationService(config);
       futures.add(
         validationService.processMessage(pullRequest, message.ackId!, pubsub),
       );
diff --git a/auto_submit/lib/service/config.dart b/auto_submit/lib/service/config.dart
index 2c4225a621..466533a0ce 100644
--- a/auto_submit/lib/service/config.dart
+++ b/auto_submit/lib/service/config.dart
@@ -59,11 +59,37 @@ class Config {
   static const String kFlutterGitHubBotKey = 'AUTO_SUBMIT_FLUTTER_GITHUB_TOKEN';
   static const String kTreeStatusDiscordUrl = 'TREE_STATUS_DISCORD_WEBHOOK_URL';
 
-  /// Labels autosubmit looks for on pull requests
+  /// When present on a pull request, instructs Cocoon to submit it
+  /// automatically as soon as all the required checks pass.
   ///
   /// Keep this in sync with the similar `Config` class in `app_dart`.
   static const String kAutosubmitLabel = 'autosubmit';
 
+  /// When present on a pull request, allows it to land without passing all the
+  /// checks, and jumps the merge queue.
+  ///
+  /// Keep this in sync with the similar `Config` class in `app_dart`.
+  static const String kEmergencyLabel = 'emergency';
+
+  /// Validates that CI tasks were successfully created from the .ci.yaml file.
+  ///
+  /// If this check fails, it means Cocoon failed to fully populate the list of
+  /// CI checks and the PR/commit should be treated as failing.
+  static const String kCiYamlCheckName = 'ci.yaml validation';
+
+  /// A required check that stays in pending state until a sufficient subset of
+  /// checks pass.
+  ///
+  /// This check is "required", meaning that it must pass before Github will
+  /// allow a PR to land in the merge queue, or a merge group to land on the
+  /// target branch (main or master).
+  ///
+  /// IMPORTANT: the name of this task - "Merge Queue Guard" - must strictly
+  /// match the name of the required check configured in the repo settings.
+  /// Changing the name here or in the settings alone will break the PR
+  /// workflow.
+  static const String kMergeQueueLockName = 'Merge Queue Guard';
+
   /// GitHub check stale threshold.
   static const int kGitHubCheckStaleThreshold = 2; // hours
 
@@ -82,9 +108,6 @@ class Config {
   /// as a revert.
   static const String kRevertOfLabel = 'revert of';
 
-  /// The label which shows the overrideTree    Status.
-  String get overrideTreeStatusLabel => 'warning: land on red to fix tree breakage';
-
   /// Repository Slug data
   /// GitHub repositories that use CI status to determine if pull requests can be submitted.
   static Set<RepositorySlug> reposWithTreeStatus = <RepositorySlug>{
diff --git a/auto_submit/lib/service/github_service.dart b/auto_submit/lib/service/github_service.dart
index ca6d0247fd..64b1251028 100644
--- a/auto_submit/lib/service/github_service.dart
+++ b/auto_submit/lib/service/github_service.dart
@@ -43,6 +43,34 @@ class GithubService {
         .toList();
   }
 
+  Future<CheckRun> updateCheckRun({
+    required RepositorySlug slug,
+    required CheckRun checkRun,
+    String? name,
+    String? detailsUrl,
+    String? externalId,
+    DateTime? startedAt,
+    CheckRunStatus status = CheckRunStatus.queued,
+    CheckRunConclusion? conclusion,
+    DateTime? completedAt,
+    CheckRunOutput? output,
+    List<CheckRunAction>? actions,
+  }) async {
+    return github.checks.checkRuns.updateCheckRun(
+      slug,
+      checkRun,
+      name: name,
+      detailsUrl: detailsUrl,
+      externalId: externalId,
+      startedAt: startedAt,
+      status: status,
+      conclusion: conclusion,
+      completedAt: completedAt,
+      output: output,
+      actions: actions,
+    );
+  }
+
   /// Fetches the specified commit.
   Future<RepositoryCommit> getCommit(
     RepositorySlug slug,
diff --git a/auto_submit/lib/service/process_method.dart b/auto_submit/lib/service/process_method.dart
index 3a7eea63fc..bf7e8aa583 100644
--- a/auto_submit/lib/service/process_method.dart
+++ b/auto_submit/lib/service/process_method.dart
@@ -6,6 +6,7 @@
 /// found.
 enum ProcessMethod {
   processAutosubmit,
+  processEmergency,
   processRevert,
   doNotProcess,
 }
diff --git a/auto_submit/lib/service/pull_request_validation_service.dart b/auto_submit/lib/service/pull_request_validation_service.dart
index b4677d0de4..30b2dbb371 100644
--- a/auto_submit/lib/service/pull_request_validation_service.dart
+++ b/auto_submit/lib/service/pull_request_validation_service.dart
@@ -28,11 +28,13 @@ class PullRequestValidationService extends ValidationService {
 
   /// Processes a pub/sub message associated with PullRequest event.
   Future<void> processMessage(github.PullRequest messagePullRequest, String ackId, PubSub pubsub) async {
-    if (await shouldProcess(messagePullRequest)) {
+    final slug = messagePullRequest.base!.repo!.slug();
+    final fullPullRequest = await getFullPullRequest(slug, messagePullRequest.number!);
+    if (shouldProcess(fullPullRequest)) {
       await processPullRequest(
         config: config,
         result: await getNewestPullRequestInfo(config, messagePullRequest),
-        messagePullRequest: messagePullRequest,
+        pullRequest: fullPullRequest,
         ackId: ackId,
         pubsub: pubsub,
       );
@@ -42,9 +44,11 @@ class PullRequestValidationService extends ValidationService {
     }
   }
 
-  Future<bool> shouldProcess(github.PullRequest pullRequest) async {
-    final (currentPullRequest, labelNames) = await getPrWithLabels(pullRequest);
-    return (currentPullRequest.state == 'open' && labelNames.contains(Config.kAutosubmitLabel));
+  bool shouldProcess(github.PullRequest pullRequest) {
+    final labelNames = pullRequest.labelNames;
+    final containsLabelsNeedingValidation =
+        labelNames.contains(Config.kAutosubmitLabel) || labelNames.contains(Config.kEmergencyLabel);
+    return pullRequest.state == 'open' && containsLabelsNeedingValidation;
   }
 
   /// Processes a PullRequest running several validations to decide whether to
@@ -52,16 +56,16 @@ class PullRequestValidationService extends ValidationService {
   Future<void> processPullRequest({
     required Config config,
     required QueryResult result,
-    required github.PullRequest messagePullRequest,
+    required github.PullRequest pullRequest,
     required String ackId,
     required PubSub pubsub,
   }) async {
-    final github.RepositorySlug slug = messagePullRequest.base!.repo!.slug();
-    final int prNumber = messagePullRequest.number!;
+    final github.RepositorySlug slug = pullRequest.base!.repo!.slug();
+    final int prNumber = pullRequest.number!;
 
     // If a pull request is currently in the merge queue do not touch it. Let
     // the merge queue merge it, or kick it out of the merge queue.
-    if (messagePullRequest.isMergeQueueEnabled) {
+    if (pullRequest.isMergeQueueEnabled) {
       if (result.repository!.pullRequest!.isInMergeQueue) {
         log.info(
           '${slug.fullName}/$prNumber is already in the merge queue. Skipping.',
@@ -71,22 +75,91 @@ class PullRequestValidationService extends ValidationService {
       }
     }
 
+    final processor = _PullRequestValidationProcessor(
+      validationService: this,
+      githubService: await config.createGithubService(slug),
+      config: config,
+      result: result,
+      pullRequest: pullRequest,
+      ackId: ackId,
+      pubsub: pubsub,
+    );
+    await processor.process();
+  }
+}
+
+/// A helper class that breaks down the logic into multiple smaller methods, and
+/// provides common objects to all methods that need them.
+class _PullRequestValidationProcessor {
+  _PullRequestValidationProcessor({
+    required this.validationService,
+    required this.githubService,
+    required this.config,
+    required this.result,
+    required this.pullRequest,
+    required this.ackId,
+    required this.pubsub,
+  })  : slug = pullRequest.base!.repo!.slug(),
+        prNumber = pullRequest.number!;
+
+  final PullRequestValidationService validationService;
+  final GithubService githubService;
+  final Config config;
+  final QueryResult result;
+  final github.PullRequest pullRequest;
+  final String ackId;
+  final PubSub pubsub;
+  final github.RepositorySlug slug;
+  final int prNumber;
+
+  Future<void> process() async {
+    final hasEmergencyLabel = pullRequest.labelNames.contains(Config.kEmergencyLabel);
+    final hasAutosubmitLabel = pullRequest.labelNames.contains(Config.kAutosubmitLabel);
+
+    if (hasEmergencyLabel) {
+      final didEmergencyProcessCleanly = await _processEmergency();
+      if (!didEmergencyProcessCleanly) {
+        // The emergency label failed to process cleanly. Do not continue processing
+        // the "autosubmit" label, as it may not be safe. The author assumed that
+        // the combination of both labels would cleanly land, and it didn't.
+        if (hasAutosubmitLabel) {
+          await _removeAutosubmitLabel('emergency label processing failed');
+        }
+        await pubsub.acknowledge('auto-submit-queue-sub', ackId);
+        return;
+      }
+    }
+
+    if (hasAutosubmitLabel) {
+      await _processAutosubmit();
+    } else {
+      log.info('Ack the processed message : $ackId.');
+      await pubsub.acknowledge('auto-submit-queue-sub', ackId);
+    }
+  }
+
+  /// Processes the "emergency" label.
+  ///
+  /// Returns true, if the processing succeeded and the validation should move
+  /// onto the "autosubmit" label. The primary result of a successful processing
+  /// of the "emergency" label is the unlocking of the "Merge Queue Guard" check
+  /// run, which allows the respective PR to be enqueued either manually using
+  /// GitHub UI, or via the "autosubmit" label.
+  ///
+  /// Returns false, if the processing failed, the "Merge Queue Guard" was not
+  /// unlocked, and any further validation should stop.
+  Future<bool> _processEmergency() async {
     final RepositoryConfiguration repositoryConfiguration = await config.getRepositoryConfiguration(slug);
 
     // filter out validations here
     final ValidationFilter validationFilter = ValidationFilter(
       config: config,
-      processMethod: ProcessMethod.processAutosubmit,
+      processMethod: ProcessMethod.processEmergency,
       repositoryConfiguration: repositoryConfiguration,
     );
     final Set<Validation> validations = validationFilter.getValidations();
 
     final Map<String, ValidationResult> validationsMap = <String, ValidationResult>{};
-    final GithubService githubService = await config.createGithubService(slug);
-
-    // get the labels before validation so that we can detect all labels.
-    // TODO (https://github.com/flutter/flutter/issues/132811) remove this after graphql is removed.
-    final github.PullRequest updatedPullRequest = await githubService.getPullRequest(slug, messagePullRequest.number!);
 
     /// Runs all the validation defined in the service.
     /// If the runCi flag is false then we need a way to not run the ciSuccessful validation.
@@ -94,24 +167,102 @@ class PullRequestValidationService extends ValidationService {
       log.info('${slug.fullName}/$prNumber running validation ${validation.name}');
       final ValidationResult validationResult = await validation.validate(
         result,
-        updatedPullRequest,
+        pullRequest,
       );
       validationsMap[validation.name] = validationResult;
     }
 
     /// If there is at least one action that requires to remove label do so and add comments for all the failures.
     bool shouldReturn = false;
-    for (MapEntry<String, ValidationResult> result in validationsMap.entries) {
-      if (!result.value.result && result.value.action == Action.REMOVE_LABEL) {
-        final String commmentMessage = result.value.message.isEmpty ? 'Validations Fail.' : result.value.message;
-        final String message = 'auto label is removed for ${slug.fullName}/$prNumber, due to $commmentMessage';
-        await githubService.removeLabel(slug, prNumber, Config.kAutosubmitLabel);
+    for (final MapEntry(key: _, :value) in validationsMap.entries) {
+      if (!value.result && value.action == Action.REMOVE_LABEL) {
+        final String commmentMessage = value.message.isEmpty ? 'Validations Fail.' : value.message;
+        final String message =
+            '${Config.kEmergencyLabel} label is removed for ${slug.fullName}/$prNumber, due to $commmentMessage';
+        await githubService.removeLabel(slug, prNumber, Config.kEmergencyLabel);
         await githubService.createComment(slug, prNumber, message);
         log.info(message);
         shouldReturn = true;
       }
     }
 
+    if (shouldReturn) {
+      log.info('The pr ${slug.fullName}/$prNumber is not eligible for emergency landing.');
+      return false;
+    }
+
+    // If PR has some failures to ignore temporarily do nothing and continue.
+    for (final MapEntry(:key, :value) in validationsMap.entries) {
+      if (!value.result && value.action == Action.IGNORE_TEMPORARILY) {
+        log.info(
+          'Temporarily ignoring processing of ${slug.fullName}/$prNumber due to $key failing validation.',
+        );
+        return true;
+      }
+    }
+
+    // At this point all validations passed, and the PR can proceed to landing
+    // as an emergency.
+    final guard = (await githubService.getCheckRunsFiltered(
+      slug: slug,
+      ref: pullRequest.base!.ref!,
+      checkName: Config.kMergeQueueLockName,
+    ))
+        .singleOrNull;
+
+    if (guard == null) {
+      log.severe(
+        'Failed to process the emergency label in ${slug.fullName}/$prNumber. '
+        '"kMergeQueueLockName" check run is missing.',
+      );
+      return false;
+    }
+
+    await githubService.updateCheckRun(
+      slug: slug,
+      checkRun: guard,
+      status: github.CheckRunStatus.completed,
+      conclusion: github.CheckRunConclusion.success,
+    );
+
+    log.info('Unlocked merge guard for ${slug.fullName}/$prNumber to allow it to land as an emergency.');
+    return true;
+  }
+
+  Future<void> _processAutosubmit() async {
+    final RepositoryConfiguration repositoryConfiguration = await config.getRepositoryConfiguration(slug);
+
+    // filter out validations here
+    final ValidationFilter validationFilter = ValidationFilter(
+      config: config,
+      processMethod: ProcessMethod.processAutosubmit,
+      repositoryConfiguration: repositoryConfiguration,
+    );
+    final Set<Validation> validations = validationFilter.getValidations();
+
+    final Map<String, ValidationResult> validationsMap = <String, ValidationResult>{};
+
+    /// Runs all the validation defined in the service.
+    /// If the runCi flag is false then we need a way to not run the ciSuccessful validation.
+    for (Validation validation in validations) {
+      log.info('${slug.fullName}/$prNumber running validation ${validation.name}');
+      final ValidationResult validationResult = await validation.validate(
+        result,
+        pullRequest,
+      );
+      validationsMap[validation.name] = validationResult;
+    }
+
+    /// If there is at least one action that requires to remove label do so and add comments for all the failures.
+    bool shouldReturn = false;
+    for (final MapEntry(key: _, :value) in validationsMap.entries) {
+      if (!value.result && value.action == Action.REMOVE_LABEL) {
+        final String commentMessage = value.message.isEmpty ? 'Validations Fail.' : value.message;
+        await _removeAutosubmitLabel(commentMessage);
+        shouldReturn = true;
+      }
+    }
+
     if (shouldReturn) {
       log.info(
         'The pr ${slug.fullName}/$prNumber with message: $ackId should be acknowledged due to validation failure.',
@@ -122,19 +273,19 @@ class PullRequestValidationService extends ValidationService {
     }
 
     // If PR has some failures to ignore temporarily do nothing and continue.
-    for (MapEntry<String, ValidationResult> result in validationsMap.entries) {
-      if (!result.value.result && result.value.action == Action.IGNORE_TEMPORARILY) {
+    for (final MapEntry(:key, :value) in validationsMap.entries) {
+      if (!value.result && value.action == Action.IGNORE_TEMPORARILY) {
         log.info(
-          'Temporarily ignoring processing of ${slug.fullName}/$prNumber due to ${result.key} failing validation.',
+          'Temporarily ignoring processing of ${slug.fullName}/$prNumber due to $key failing validation.',
         );
         return;
       }
     }
 
     // If we got to this point it means we are ready to submit the PR.
-    final MergeResult processed = await submitPullRequest(
+    final MergeResult processed = await validationService.submitPullRequest(
       config: config,
-      messagePullRequest: messagePullRequest,
+      pullRequest: pullRequest,
     );
 
     if (!processed.result) {
@@ -145,9 +296,9 @@ class PullRequestValidationService extends ValidationService {
     } else {
       log.info('Pull Request ${slug.fullName}/$prNumber was ${processed.method.pastTenseLabel} successfully!');
       log.info('Attempting to insert a pull request record into the database for $prNumber');
-      await insertPullRequestRecord(
+      await validationService.insertPullRequestRecord(
         config: config,
-        pullRequest: messagePullRequest,
+        pullRequest: pullRequest,
         pullRequestType: PullRequestChangeType.change,
       );
     }
@@ -155,4 +306,12 @@ class PullRequestValidationService extends ValidationService {
     log.info('Ack the processed message : $ackId.');
     await pubsub.acknowledge('auto-submit-queue-sub', ackId);
   }
+
+  Future<void> _removeAutosubmitLabel(String reason) async {
+    final String message =
+        '${Config.kAutosubmitLabel} label was removed for ${slug.fullName}/$prNumber, because $reason';
+    await githubService.removeLabel(slug, prNumber, Config.kAutosubmitLabel);
+    await githubService.createComment(slug, prNumber, message);
+    log.info(message);
+  }
 }
diff --git a/auto_submit/lib/service/revert_request_validation_service.dart b/auto_submit/lib/service/revert_request_validation_service.dart
index 5db94ff72a..5a79d26616 100644
--- a/auto_submit/lib/service/revert_request_validation_service.dart
+++ b/auto_submit/lib/service/revert_request_validation_service.dart
@@ -57,11 +57,12 @@ class RevertRequestValidationService extends ValidationService {
   ) async {
     // Make sure the pull request still contains the labels.
     final github.PullRequest messagePullRequest = githubPullRequestEvent.pullRequest!;
-    final (currentPullRequest, labelNames) = await getPrWithLabels(messagePullRequest);
-    final RevertProcessMethod revertProcessMethod = await shouldProcess(currentPullRequest, labelNames);
+    final slug = messagePullRequest.base!.repo!.slug();
+    final fullPullRequest = await getFullPullRequest(slug, messagePullRequest.number!);
+    final revertProcessMethod = await shouldProcess(fullPullRequest);
 
-    final GithubPullRequestEvent updatedGithubPullRequestEvent = GithubPullRequestEvent(
-      pullRequest: currentPullRequest,
+    final updatedGithubPullRequestEvent = GithubPullRequestEvent(
+      pullRequest: fullPullRequest,
       action: githubPullRequestEvent.action,
       sender: githubPullRequestEvent.sender,
     );
@@ -80,7 +81,7 @@ class RevertRequestValidationService extends ValidationService {
       case RevertProcessMethod.revertOf:
         await processRevertOfRequest(
           result: await getNewestPullRequestInfo(config, messagePullRequest),
-          githubPullRequestEvent: updatedGithubPullRequestEvent,
+          githubPullRequestEvent: githubPullRequestEvent,
           ackId: ackId,
           pubsub: pubsub,
         );
@@ -126,10 +127,8 @@ class RevertRequestValidationService extends ValidationService {
   }
 
   /// Determine if we should process the incoming pull request webhook event.
-  Future<RevertProcessMethod> shouldProcess(
-    github.PullRequest pullRequest,
-    List<String> labelNames,
-  ) async {
+  Future<RevertProcessMethod> shouldProcess(github.PullRequest pullRequest) async {
+    final labelNames = pullRequest.labelNames;
     // This is the initial revert request state.
     if (pullRequest.state == 'closed' && labelNames.contains(Config.kRevertLabel) && pullRequest.mergedAt != null) {
       return RevertProcessMethod.revert;
@@ -214,14 +213,14 @@ class RevertRequestValidationService extends ValidationService {
     required String ackId,
     required PubSub pubsub,
   }) async {
-    final github.PullRequest messagePullRequest = githubPullRequestEvent.pullRequest!;
-    final github.RepositorySlug slug = messagePullRequest.base!.repo!.slug();
+    final pullRequest = githubPullRequestEvent.pullRequest!;
+    final github.RepositorySlug slug = pullRequest.base!.repo!.slug();
     final GithubService githubService = await config.createGithubService(slug);
-    final int prNumber = messagePullRequest.number!;
+    final int prNumber = pullRequest.number!;
 
     // If a pull request is currently in the merge queue do not touch it. Let
     // the merge queue merge it, or kick it out of the merge queue.
-    if (messagePullRequest.isMergeQueueEnabled) {
+    if (pullRequest.isMergeQueueEnabled) {
       if (result.repository!.pullRequest!.isInMergeQueue) {
         log.info(
           '${slug.fullName}/$prNumber is already in the merge queue. Skipping.',
@@ -264,15 +263,15 @@ class RevertRequestValidationService extends ValidationService {
       validationsMap[validation.name] = await validation.validate(
         result,
         // this needs to be the newly opened pull request.
-        messagePullRequest,
+        pullRequest,
       );
     }
 
     /// If there is at least one action that requires to remove label do so and add comments for all the failures.
     bool shouldReturn = false;
-    for (MapEntry<String, ValidationResult> result in validationsMap.entries) {
-      if (!result.value.result && result.value.action == Action.REMOVE_LABEL) {
-        final String commmentMessage = result.value.message.isEmpty ? 'Validations Fail.' : result.value.message;
+    for (final MapEntry(key: _, :value) in validationsMap.entries) {
+      if (!value.result && value.action == Action.REMOVE_LABEL) {
+        final String commmentMessage = value.message.isEmpty ? 'Validations Fail.' : value.message;
         final String message = 'auto label is removed for ${slug.fullName}/$prNumber, due to $commmentMessage';
         await githubService.removeLabel(slug, prNumber, Config.kRevertOfLabel);
         await githubService.createComment(slug, prNumber, message);
@@ -291,10 +290,10 @@ class RevertRequestValidationService extends ValidationService {
     }
 
     // If PR has some failures to ignore temporarily do nothing and continue.
-    for (MapEntry<String, ValidationResult> result in validationsMap.entries) {
-      if (!result.value.result && result.value.action == Action.IGNORE_TEMPORARILY) {
+    for (final MapEntry(:key, :value) in validationsMap.entries) {
+      if (!value.result && value.action == Action.IGNORE_TEMPORARILY) {
         log.info(
-          'Temporarily ignoring processing of ${slug.fullName}/$prNumber due to ${result.key} failing validation.',
+          'Temporarily ignoring processing of ${slug.fullName}/$prNumber due to $key failing validation.',
         );
         return;
       }
@@ -303,7 +302,7 @@ class RevertRequestValidationService extends ValidationService {
     // If we got to this point it means we are ready to submit the PR.
     final MergeResult processed = await submitPullRequest(
       config: config,
-      messagePullRequest: messagePullRequest,
+      pullRequest: pullRequest,
     );
 
     if (!processed.result) {
@@ -314,14 +313,14 @@ class RevertRequestValidationService extends ValidationService {
     } else {
       // Need to add the discord notification here.
       final DiscordNotification discordNotification = await discordNotificationClient;
-      final Message discordMessage = craftDiscordRevertMessage(messagePullRequest);
+      final Message discordMessage = craftDiscordRevertMessage(pullRequest);
       discordNotification.notifyDiscordChannelWebhook(jsonEncode(discordMessage.toJson()));
 
       log.info('Pull Request ${slug.fullName}/$prNumber was ${processed.method.pastTenseLabel} successfully!');
       log.info('Attempting to insert a pull request record into the database for $prNumber');
       await insertPullRequestRecord(
         config: config,
-        pullRequest: messagePullRequest,
+        pullRequest: pullRequest,
         pullRequestType: PullRequestChangeType.revert,
       );
     }
diff --git a/auto_submit/lib/service/validation_service.dart b/auto_submit/lib/service/validation_service.dart
index cfc3308f95..74747a7f76 100644
--- a/auto_submit/lib/service/validation_service.dart
+++ b/auto_submit/lib/service/validation_service.dart
@@ -45,41 +45,36 @@ class ValidationService {
     return QueryResult.fromJson(data);
   }
 
-  Future<(github.PullRequest, List<String>)> getPrWithLabels(github.PullRequest pullRequest) async {
-    final github.RepositorySlug slug = pullRequest.base!.repo!.slug();
+  Future<github.PullRequest> getFullPullRequest(github.RepositorySlug slug, int pullRequestNumber) async {
     final GithubService githubService = await config.createGithubService(slug);
-    final github.PullRequest currentPullRequest = await githubService.getPullRequest(slug, pullRequest.number!);
-    final List<String> labelNames = (currentPullRequest.labels as List<github.IssueLabel>)
-        .map<String>((github.IssueLabel labelMap) => labelMap.name)
-        .toList();
-    return (currentPullRequest, labelNames);
+    return githubService.getPullRequest(slug, pullRequestNumber);
   }
 
   /// Merges the commit if the PullRequest passes all the validations.
   Future<MergeResult> submitPullRequest({
     required Config config,
-    required github.PullRequest messagePullRequest,
+    required github.PullRequest pullRequest,
   }) async {
-    final github.RepositorySlug slug = messagePullRequest.base!.repo!.slug();
-    final int number = messagePullRequest.number!;
+    final github.RepositorySlug slug = pullRequest.base!.repo!.slug();
+    final int number = pullRequest.number!;
 
     // Pass an explicit commit message from the PR title otherwise the GitHub API will use the first commit message.
     const String revertPattern = 'Revert "Revert';
     String messagePrefix = '';
 
-    if (messagePullRequest.title!.contains(revertPattern)) {
+    if (pullRequest.title!.contains(revertPattern)) {
       // Cleanup auto-generated revert messages.
       messagePrefix = '''
-${messagePullRequest.title!.replaceFirst('Revert "Revert', 'Reland')}
+${pullRequest.title!.replaceFirst('Revert "Revert', 'Reland')}
 
 ''';
     }
 
-    final String prBody = _sanitizePrBody(messagePullRequest.body ?? '');
+    final String prBody = _sanitizePrBody(pullRequest.body ?? '');
     final String commitMessage = '$messagePrefix$prBody';
 
-    if (messagePullRequest.isMergeQueueEnabled) {
-      return _enqueuePullRequest(slug, messagePullRequest);
+    if (pullRequest.isMergeQueueEnabled) {
+      return _enqueuePullRequest(slug, pullRequest);
     } else {
       return _mergePullRequest(number, commitMessage, slug);
     }
@@ -88,7 +83,7 @@ ${messagePullRequest.title!.replaceFirst('Revert "Revert', 'Reland')}
   Future<MergeResult> _enqueuePullRequest(github.RepositorySlug slug, github.PullRequest restPullRequest) async {
     final graphQlService = await GraphQlService.forRepo(config, slug);
     final isEmergencyPullRequest =
-        restPullRequest.labels?.where((label) => label.name == 'emergency').isNotEmpty ?? false;
+        restPullRequest.labels?.where((label) => label.name == Config.kEmergencyLabel).isNotEmpty ?? false;
 
     try {
       await retryOptions.retry(
@@ -117,7 +112,6 @@ ${messagePullRequest.title!.replaceFirst('Revert "Revert', 'Reland')}
             commitMessage: commitMessage,
             slug: slug,
             number: number,
-            // TODO(ricardoamador): make this configurable per repository, https://github.com/flutter/flutter/issues/114557
             mergeMethod: github.MergeMethod.squash,
           );
         },
@@ -288,4 +282,14 @@ extension PullRequestExtension on github.PullRequest {
     final slug = base!.repo!.slug();
     return mqEnabledRepos.contains(slug.fullName);
   }
+
+  /// Extracts label names from the `IssueLabel` list [labels].
+  List<String> get labelNames {
+    final labels = this.labels;
+    if (labels == null) {
+      return const <String>[];
+    }
+
+    return labels.map<String>((label) => label.name).toList();
+  }
 }
diff --git a/auto_submit/lib/validations/ci_successful.dart b/auto_submit/lib/validations/ci_successful.dart
index 82ba156dcb..21fe05023a 100644
--- a/auto_submit/lib/validations/ci_successful.dart
+++ b/auto_submit/lib/validations/ci_successful.dart
@@ -57,7 +57,7 @@ class CiSuccessful extends Validation {
     final String? baseBranch = messagePullRequest.base!.ref;
     if (baseBranch == targetBranch) {
       // Only validate tree status where base branch is the default branch.
-      if (!treeStatusCheck(slug, prNumber, statuses)) {
+      if (!isTreeStatusReporting(slug, prNumber, statuses)) {
         log.warning('Statuses were not ready for ${slug.fullName}/$prNumber, sha: $commit.');
         return ValidationResult(false, Action.IGNORE_TEMPORARILY, 'Hold to wait for the tree status ready.');
       }
@@ -95,17 +95,22 @@ class CiSuccessful extends Validation {
             'issues identified (or deflake) before re-applying this label.');
       }
     }
-    final Action action =
-        labelNames.contains(config.overrideTreeStatusLabel) ? Action.IGNORE_FAILURE : Action.REMOVE_LABEL;
+    final Action action = labelNames.contains(Config.kEmergencyLabel) ? Action.IGNORE_FAILURE : Action.REMOVE_LABEL;
     return ValidationResult(allSuccess, action, buffer.toString());
   }
 
-  /// Check the tree status.
+  /// Return true if the tree status check has been reported, or if doesn't have
+  /// to be reported.
+  ///
+  /// Tree status is pushed by [PushBuildStatusToGithub], which is asynchronous
+  /// relative to the creation of the PR. At the time the CI status is being
+  /// checked, the tree status may not have been reported yet.
   ///
   /// If a repo has a tree status, we should wait for it to show up instead of posting
   /// a failure to GitHub pull request.
+  ///
   /// If a repo doesn't have a tree status, simply return `true`.
-  bool treeStatusCheck(github.RepositorySlug slug, int prNumber, List<ContextNode> statuses) {
+  bool isTreeStatusReporting(github.RepositorySlug slug, int prNumber, List<ContextNode> statuses) {
     bool treeStatusValid = false;
     if (!Config.reposWithTreeStatus.contains(slug)) {
       return true;
@@ -141,7 +146,6 @@ class CiSuccessful extends Validation {
     Set<FailureDetail> failures,
     bool allSuccess,
   ) {
-    final String overrideTreeStatusLabel = config.overrideTreeStatusLabel;
     log.info('Validating name: ${slug.name}/$prNumber, statuses: $statuses');
 
     final List<ContextNode> staleStatuses = <ContextNode>[];
@@ -150,7 +154,7 @@ class CiSuccessful extends Validation {
       final String? name = status.context;
 
       if (status.state != STATUS_SUCCESS) {
-        if (notInAuthorsControl.contains(name) && labelNames.contains(overrideTreeStatusLabel)) {
+        if (notInAuthorsControl.contains(name) && labelNames.contains(Config.kEmergencyLabel)) {
           continue;
         }
         allSuccess = false;
@@ -194,6 +198,11 @@ class CiSuccessful extends Validation {
     for (github.CheckRun checkRun in checkRuns) {
       final String? name = checkRun.name;
 
+      if (checkRun.name == Config.kMergeQueueLockName) {
+        // Merge Queue Guard is not used to determine the status of CI.
+        continue;
+      }
+
       if (checkRun.conclusion == github.CheckRunConclusion.skipped ||
           checkRun.conclusion == github.CheckRunConclusion.success ||
           (checkRun.status == github.CheckRunStatus.completed &&
diff --git a/auto_submit/lib/validations/validation_filter.dart b/auto_submit/lib/validations/validation_filter.dart
index f65b60eba1..7459a467e2 100644
--- a/auto_submit/lib/validations/validation_filter.dart
+++ b/auto_submit/lib/validations/validation_filter.dart
@@ -23,6 +23,8 @@ abstract class ValidationFilter {
     switch (processMethod) {
       case ProcessMethod.processAutosubmit:
         return PullRequestValidationFilter(config, repositoryConfiguration);
+      case ProcessMethod.processEmergency:
+        return EmergencyValidationFilter(config, repositoryConfiguration);
       case ProcessMethod.processRevert:
         return RevertRequestValidationFilter(config, repositoryConfiguration);
       default:
@@ -58,6 +60,20 @@ class PullRequestValidationFilter implements ValidationFilter {
   }
 }
 
+/// Provides validations for applying the `emergency` label.
+class EmergencyValidationFilter implements ValidationFilter {
+  EmergencyValidationFilter(this.config, this.repositoryConfiguration);
+
+  final Config config;
+  final RepositoryConfiguration repositoryConfiguration;
+
+  @override
+  Set<Validation> getValidations() => {
+        Approval(config: config),
+        Mergeable(config: config),
+      };
+}
+
 /// [RevertRequestValidationFilter] returns a Set of validations that we run on
 /// all revert pull requests.
 class RevertRequestValidationFilter implements ValidationFilter {
@@ -67,13 +83,9 @@ class RevertRequestValidationFilter implements ValidationFilter {
   final RepositoryConfiguration repositoryConfiguration;
 
   @override
-  Set<Validation> getValidations() {
-    final Set<Validation> validationsToRun = {};
-
-    validationsToRun.add(Approval(config: config));
-    validationsToRun.add(RequiredCheckRuns(config: config));
-    validationsToRun.add(Mergeable(config: config));
-
-    return validationsToRun;
-  }
+  Set<Validation> getValidations() => {
+        Approval(config: config),
+        RequiredCheckRuns(config: config),
+        Mergeable(config: config),
+      };
 }
diff --git a/auto_submit/test/requests/check_pull_request_test.dart b/auto_submit/test/requests/check_pull_request_test.dart
index d28dcaf0b0..bbeef08198 100644
--- a/auto_submit/test/requests/check_pull_request_test.dart
+++ b/auto_submit/test/requests/check_pull_request_test.dart
@@ -55,7 +55,6 @@ void main() {
     const String testSubscription = 'test-sub';
     const String testTopic = 'test-topic';
     const String rollorAuthor = 'engine-flutter-autoroll';
-    const String labelName = 'warning: land on red to fix tree breakage';
     const String cocoonRepo = 'cocoon';
     const String noAutosubmitLabel = 'no_autosubmit';
 
@@ -320,7 +319,10 @@ void main() {
         prNumber: 1,
         repoName: cocoonRepo,
       );
-      githubService.pullRequestData = pullRequest1;
+
+      githubService.usePullRequestList = true;
+      githubService.pullRequestMockList = [pullRequest1, pullRequest2];
+
       // 'octocat' is the pr author from generatePullRequest calls.
       // 'member' is in the review nodes and 'author1' is the pr author.
       githubService.isTeamMemberMockMap['member'] = true;
@@ -418,10 +420,10 @@ void main() {
       assert(pubsub.messagesQueue.isEmpty);
     });
 
-    test('Merges PR with failed tree status if override tree status label is provided', () async {
+    test('Merges PR with failed tree status if the "emergency" label is provided', () async {
       final PullRequest pullRequest = generatePullRequest(
         prNumber: 0,
-        labelName: labelName,
+        labelName: Config.kEmergencyLabel,
       );
       // 'member' is in the review nodes and 'author1' is the pr author.
       githubService.isTeamMemberMockMap['member'] = true;
@@ -434,6 +436,37 @@ void main() {
         ),
       );
 
+      githubService.checkRunsData = '''{
+  "total_count": 2,
+  "check_runs": [
+    {
+      "id": 1,
+      "head_sha": "be6ff099a4ee56e152a5fa2f37edd10f79d1269a",
+      "external_id": "",
+      "details_url": "https://example.com",
+      "status": "completed",
+      "conclusion": "success",
+      "started_at": "2018-05-04T01:14:52Z",
+      "name": "mighty_readme",
+      "check_suite": {
+        "id": 5
+      }
+    },
+    {
+      "id": 2,
+      "head_sha": "be6ff099a4ee56e152a5fa2f37edd10f79d1269a",
+      "external_id": "",
+      "details_url": "https://example.com",
+      "status": "in_progress",
+      "started_at": "2018-05-04T01:14:52Z",
+      "name": "Merge Queue Guard",
+      "check_suite": {
+        "id": 5
+      }
+    }
+  ]
+}''';
+
       checkPullRequest = CheckPullRequest(
         config: config,
         pubsub: pubsub,
@@ -453,19 +486,19 @@ void main() {
       verifyQueries(expectedOptions);
 
       final Map<int, RepositorySlug> expectedMergeRequestMap = {};
-      expectedMergeRequestMap[0] = RepositorySlug(
-        'flutter',
-        'flutter',
-      );
-
-      githubService.mergeRequestMock = PullRequestMerge(
-        merged: true,
-        sha: 'sha1',
-        message: 'Pull request merged successfully',
-      );
+      expectedMergeRequestMap[0] = RepositorySlug('flutter', 'flutter');
 
       githubService.verifyMergePullRequests(expectedMergeRequestMap);
 
+      // Verify that the "Merge Queue Guard" was unlocked.
+      expect(githubService.checkRunUpdates, hasLength(1));
+      final checkRunUpdate = githubService.checkRunUpdates.single;
+      expect(checkRunUpdate.slug, RepositorySlug('flutter', 'flutter'));
+      expect(checkRunUpdate.checkRun.id, 2);
+      expect(checkRunUpdate.checkRun.name, 'Merge Queue Guard');
+      expect(checkRunUpdate.status, CheckRunStatus.completed);
+      expect(checkRunUpdate.conclusion, CheckRunConclusion.success);
+
       assert(pubsub.messagesQueue.isEmpty);
     });
 
diff --git a/auto_submit/test/service/pull_request_validation_service_test.dart b/auto_submit/test/service/pull_request_validation_service_test.dart
index 07c2c3da8a..e2c1038252 100644
--- a/auto_submit/test/service/pull_request_validation_service_test.dart
+++ b/auto_submit/test/service/pull_request_validation_service_test.dart
@@ -83,7 +83,7 @@ void main() {
     await validationService.processPullRequest(
       config: config,
       result: queryResult,
-      messagePullRequest: pullRequest,
+      pullRequest: pullRequest,
       ackId: 'test',
       pubsub: pubsub,
     );
@@ -131,7 +131,7 @@ void main() {
     await validationService.processPullRequest(
       config: config,
       result: queryResult,
-      messagePullRequest: pullRequest,
+      pullRequest: pullRequest,
       ackId: 'test',
       pubsub: pubsub,
     );
@@ -173,7 +173,7 @@ void main() {
     await validationService.processPullRequest(
       config: config,
       result: queryResult,
-      messagePullRequest: pullRequest,
+      pullRequest: pullRequest,
       ackId: 'test',
       pubsub: pubsub,
     );
@@ -187,21 +187,21 @@ void main() {
     test('Should process message when autosubmit label exists and pr is open', () async {
       final PullRequest pullRequest = generatePullRequest(prNumber: 0, repoName: slug.name);
       githubService.pullRequestData = pullRequest;
-      expect(await validationService.shouldProcess(pullRequest), true);
+      expect(validationService.shouldProcess(pullRequest), true);
     });
 
     test('Skip processing message when autosubmit label does not exist anymore', () async {
       final PullRequest pullRequest = generatePullRequest(prNumber: 0, repoName: slug.name);
       pullRequest.labels = <IssueLabel>[];
       githubService.pullRequestData = pullRequest;
-      expect(await validationService.shouldProcess(pullRequest), false);
+      expect(validationService.shouldProcess(pullRequest), false);
     });
 
     test('Skip processing message when the pull request is closed', () async {
       final PullRequest pullRequest = generatePullRequest(prNumber: 0, repoName: slug.name);
       pullRequest.state = 'closed';
       githubService.pullRequestData = pullRequest;
-      expect(await validationService.shouldProcess(pullRequest), false);
+      expect(validationService.shouldProcess(pullRequest), false);
     });
 
     test('Should not process message when revert label exists and pr is open', () async {
@@ -209,7 +209,7 @@ void main() {
       final IssueLabel issueLabel = IssueLabel(name: 'revert');
       pullRequest.labels = <IssueLabel>[issueLabel];
       githubService.pullRequestData = pullRequest;
-      expect(await validationService.shouldProcess(pullRequest), false);
+      expect(validationService.shouldProcess(pullRequest), false);
     });
 
     test('Skip processing message when revert label exists and pr is closed', () async {
@@ -218,7 +218,7 @@ void main() {
       final IssueLabel issueLabel = IssueLabel(name: 'revert');
       pullRequest.labels = <IssueLabel>[issueLabel];
       githubService.pullRequestData = pullRequest;
-      expect(await validationService.shouldProcess(pullRequest), false);
+      expect(validationService.shouldProcess(pullRequest), false);
     });
   });
 
@@ -238,7 +238,7 @@ void main() {
 
       final MergeResult result = await validationService.submitPullRequest(
         config: config,
-        messagePullRequest: pullRequest,
+        pullRequest: pullRequest,
       );
 
       expect(result.message, contains('Reland "My first PR!"'));
@@ -263,7 +263,7 @@ void main() {
       await validationService.processPullRequest(
         config: config,
         result: queryResult,
-        messagePullRequest: pullRequest,
+        pullRequest: pullRequest,
         ackId: 'test',
         pubsub: pubsub,
       );
@@ -302,7 +302,7 @@ void main() {
       await validationService.processPullRequest(
         config: config,
         result: queryResult,
-        messagePullRequest: pullRequest,
+        pullRequest: pullRequest,
         ackId: 'test',
         pubsub: pubsub,
       );
@@ -348,7 +348,7 @@ void main() {
       await validationService.processPullRequest(
         config: config,
         result: queryResult,
-        messagePullRequest: pullRequest,
+        pullRequest: pullRequest,
         ackId: 'test',
         pubsub: pubsub,
       );
@@ -379,7 +379,7 @@ void main() {
       );
       final MergeResult result = await validationService.submitPullRequest(
         config: config,
-        messagePullRequest: pullRequest,
+        pullRequest: pullRequest,
       );
 
       expect(result.message, '''
@@ -438,7 +438,7 @@ If you need help, consider asking for advice on the #hackers-new channel on [Dis
 
       final MergeResult result = await validationService.submitPullRequest(
         config: config,
-        messagePullRequest: pullRequest,
+        pullRequest: pullRequest,
       );
 
       expect(result.result, isTrue);
@@ -488,7 +488,7 @@ This is the second line in a paragraph.''');
 
       final MergeResult result = await validationService.submitPullRequest(
         config: config,
-        messagePullRequest: pullRequest,
+        pullRequest: pullRequest,
       );
 
       expect(result.method, SubmitMethod.enqueue);
@@ -522,7 +522,7 @@ This is the second line in a paragraph.''');
 
       final MergeResult result = await validationService.submitPullRequest(
         config: config,
-        messagePullRequest: pullRequest,
+        pullRequest: pullRequest,
       );
 
       expect(result.method, SubmitMethod.merge);
@@ -537,7 +537,7 @@ This is the second line in a paragraph.''');
 
       final MergeResult result = await validationService.submitPullRequest(
         config: config,
-        messagePullRequest: pullRequest,
+        pullRequest: pullRequest,
       );
 
       expect(result.method, SubmitMethod.enqueue);
@@ -552,7 +552,7 @@ This is the second line in a paragraph.''');
 
       final MergeResult result = await validationService.submitPullRequest(
         config: config,
-        messagePullRequest: pullRequest,
+        pullRequest: pullRequest,
       );
 
       expect(result.method, SubmitMethod.enqueue);
@@ -595,7 +595,7 @@ This is the second line in a paragraph.''');
 
       final MergeResult result = await validationService.submitPullRequest(
         config: config,
-        messagePullRequest: pullRequest,
+        pullRequest: pullRequest,
       );
 
       expect(
@@ -650,7 +650,7 @@ This is the second line in a paragraph.''');
 
       final MergeResult result = await validationService.submitPullRequest(
         config: config,
-        messagePullRequest: pullRequest,
+        pullRequest: pullRequest,
       );
 
       expect(
@@ -700,7 +700,7 @@ This is the second line in a paragraph.''');
       await validationService.processPullRequest(
         config: config,
         result: createQueryResult(flutterRequest),
-        messagePullRequest: pullRequest,
+        pullRequest: pullRequest,
         ackId: 'test',
         pubsub: pubsub,
       );
diff --git a/auto_submit/test/service/revert_request_validation_service_test.dart b/auto_submit/test/service/revert_request_validation_service_test.dart
index 4517ed4e2d..3f62791dc8 100644
--- a/auto_submit/test/service/revert_request_validation_service_test.dart
+++ b/auto_submit/test/service/revert_request_validation_service_test.dart
@@ -124,10 +124,9 @@ void main() {
     test('Process revert from closed as "revert"', () async {
       final PullRequest pullRequest = generatePullRequest(prNumber: 0, repoName: slug.name, state: 'closed');
       final IssueLabel issueLabel = IssueLabel(name: 'revert');
-      final List<String> labelNames = ['revert'];
       pullRequest.labels = <IssueLabel>[issueLabel];
       githubService.pullRequestData = pullRequest;
-      final RevertProcessMethod revertProcessMethod = await validationService.shouldProcess(pullRequest, labelNames);
+      final RevertProcessMethod revertProcessMethod = await validationService.shouldProcess(pullRequest);
 
       expect(revertProcessMethod, RevertProcessMethod.revert);
     });
@@ -136,10 +135,9 @@ void main() {
       final PullRequest pullRequest =
           generatePullRequest(prNumber: 0, repoName: slug.name, state: 'open', author: config.autosubmitBot);
       final IssueLabel issueLabel = IssueLabel(name: 'revert of');
-      final List<String> labelNames = ['revert of'];
       pullRequest.labels = <IssueLabel>[issueLabel];
       githubService.pullRequestData = pullRequest;
-      final RevertProcessMethod revertProcessMethod = await validationService.shouldProcess(pullRequest, labelNames);
+      final RevertProcessMethod revertProcessMethod = await validationService.shouldProcess(pullRequest);
 
       expect(revertProcessMethod, RevertProcessMethod.revertOf);
 
@@ -152,10 +150,9 @@ void main() {
     test('Pull request state is open with revert label is not processed', () async {
       final PullRequest pullRequest = generatePullRequest(prNumber: 0, repoName: slug.name, state: 'open');
       final IssueLabel issueLabel = IssueLabel(name: 'revert');
-      final List<String> labelNames = ['revert'];
       pullRequest.labels = <IssueLabel>[issueLabel];
       githubService.pullRequestData = pullRequest;
-      final RevertProcessMethod revertProcessMethod = await validationService.shouldProcess(pullRequest, labelNames);
+      final RevertProcessMethod revertProcessMethod = await validationService.shouldProcess(pullRequest);
 
       expect(revertProcessMethod, RevertProcessMethod.none);
     });
@@ -164,10 +161,9 @@ void main() {
       final PullRequest pullRequest =
           generatePullRequest(prNumber: 0, repoName: slug.name, state: 'closed', author: config.autosubmitBot);
       final IssueLabel issueLabel = IssueLabel(name: 'revert of');
-      final List<String> labelNames = ['revert of'];
       pullRequest.labels = <IssueLabel>[issueLabel];
       githubService.pullRequestData = pullRequest;
-      final RevertProcessMethod revertProcessMethod = await validationService.shouldProcess(pullRequest, labelNames);
+      final RevertProcessMethod revertProcessMethod = await validationService.shouldProcess(pullRequest);
 
       expect(revertProcessMethod, RevertProcessMethod.none);
     });
@@ -176,10 +172,9 @@ void main() {
       final PullRequest pullRequest =
           generatePullRequest(prNumber: 0, repoName: slug.name, state: 'open', author: 'octocat');
       final IssueLabel issueLabel = IssueLabel(name: 'revert of');
-      final List<String> labelNames = ['revert of'];
       pullRequest.labels = <IssueLabel>[issueLabel];
       githubService.pullRequestData = pullRequest;
-      final RevertProcessMethod revertProcessMethod = await validationService.shouldProcess(pullRequest, labelNames);
+      final RevertProcessMethod revertProcessMethod = await validationService.shouldProcess(pullRequest);
 
       expect(revertProcessMethod, RevertProcessMethod.none);
     });
@@ -192,10 +187,9 @@ void main() {
         mergedAt: null,
       );
       final IssueLabel issueLabel = IssueLabel(name: 'revert');
-      final List<String> labelNames = ['revert'];
       pullRequest.labels = <IssueLabel>[issueLabel];
       githubService.pullRequestData = pullRequest;
-      final RevertProcessMethod revertProcessMethod = await validationService.shouldProcess(pullRequest, labelNames);
+      final RevertProcessMethod revertProcessMethod = await validationService.shouldProcess(pullRequest);
 
       expect(revertProcessMethod, RevertProcessMethod.none);
     });
@@ -1332,7 +1326,7 @@ Reason for reverting: comment was added by mistake.''';
 
       final MergeResult result = await validationService.submitPullRequest(
         config: config,
-        messagePullRequest: pullRequest,
+        pullRequest: pullRequest,
       );
 
       expect(result.message, contains('Reland "My first PR!"'));
@@ -1356,7 +1350,7 @@ Reason for reverting: comment was added by mistake.''';
       );
       final MergeResult result = await validationService.submitPullRequest(
         config: config,
-        messagePullRequest: pullRequest,
+        pullRequest: pullRequest,
       );
 
       expect(result.message, '''
@@ -1415,7 +1409,7 @@ If you need help, consider asking for advice on the #hackers-new channel on [Dis
 
       final MergeResult result = await validationService.submitPullRequest(
         config: config,
-        messagePullRequest: pullRequest,
+        pullRequest: pullRequest,
       );
 
       expect(result.result, isTrue);
diff --git a/auto_submit/test/src/service/fake_config.dart b/auto_submit/test/src/service/fake_config.dart
index 7570c0e6d8..d3aac3e28d 100644
--- a/auto_submit/test/src/service/fake_config.dart
+++ b/auto_submit/test/src/service/fake_config.dart
@@ -22,7 +22,6 @@ class FakeConfig extends Config {
     this.githubGraphQLClient,
     this.githubService,
     this.rollerAccountsValue,
-    this.overrideTreeStatusLabelValue,
     this.webhookKey,
     this.kPubsubPullNumberValue,
     this.bigqueryService,
@@ -35,7 +34,6 @@ class FakeConfig extends Config {
   GraphQLClient? githubGraphQLClient;
   GithubService? githubService = FakeGithubService();
   Set<String>? rollerAccountsValue;
-  String? overrideTreeStatusLabelValue;
   String? webhookKey;
   int? kPubsubPullNumberValue;
   BigqueryService? bigqueryService;
@@ -75,9 +73,6 @@ class FakeConfig extends Config {
         'dependabot',
       };
 
-  @override
-  String get overrideTreeStatusLabel => overrideTreeStatusLabelValue ?? 'warning: land on red to fix tree breakage';
-
   @override
   Future<String> getWebhookKey() async {
     return webhookKey ?? 'not_a_real_key';
diff --git a/auto_submit/test/src/service/fake_github_service.dart b/auto_submit/test/src/service/fake_github_service.dart
index e6ed6bd63f..d4bc37ad00 100644
--- a/auto_submit/test/src/service/fake_github_service.dart
+++ b/auto_submit/test/src/service/fake_github_service.dart
@@ -8,6 +8,7 @@ import 'package:auto_submit/service/github_service.dart';
 import 'package:cocoon_server/testing/mocks.dart';
 import 'package:github/github.dart';
 import 'package:shelf/src/response.dart';
+import 'package:test/test.dart';
 
 /// A fake GithubService implementation.
 class FakeGithubService implements GithubService {
@@ -135,6 +136,64 @@ class FakeGithubService implements GithubService {
     return checkRuns;
   }
 
+  final List<
+      ({
+        RepositorySlug slug,
+        CheckRun checkRun,
+        String? name,
+        String? detailsUrl,
+        String? externalId,
+        DateTime? startedAt,
+        CheckRunStatus status,
+        CheckRunConclusion? conclusion,
+        DateTime? completedAt,
+        CheckRunOutput? output,
+        List<CheckRunAction>? actions,
+      })> checkRunUpdates = [];
+
+  @override
+  Future<CheckRun> updateCheckRun({
+    required RepositorySlug slug,
+    required CheckRun checkRun,
+    String? name,
+    String? detailsUrl,
+    String? externalId,
+    DateTime? startedAt,
+    CheckRunStatus status = CheckRunStatus.queued,
+    CheckRunConclusion? conclusion,
+    DateTime? completedAt,
+    CheckRunOutput? output,
+    List<CheckRunAction>? actions,
+  }) async {
+    final Map<String, Object?> json = checkRun.toJson();
+
+    checkRunUpdates.add(
+      (
+        slug: slug,
+        checkRun: checkRun,
+        name: name,
+        detailsUrl: detailsUrl,
+        externalId: externalId,
+        startedAt: startedAt,
+        status: status,
+        conclusion: conclusion,
+        completedAt: completedAt,
+        output: output,
+        actions: actions,
+      ),
+    );
+
+    if (conclusion != null) {
+      json['conclusion'] = conclusion.value;
+    }
+
+    if (status != checkRun.status) {
+      json['status'] = status.value;
+    }
+
+    return CheckRun.fromJson(json);
+  }
+
   @override
   Future<RepositoryCommit> getCommit(RepositorySlug slug, String sha) async {
     final RepositoryCommit commit = RepositoryCommit.fromJson(jsonDecode(commitMock!) as Map<String, dynamic>);
@@ -269,10 +328,13 @@ class FakeGithubService implements GithubService {
   }
 
   void verifyMergePullRequests(Map<int, RepositorySlug> expected) {
-    assert(verifyPullRequestMergeCallMap.length == expected.length);
+    expect(
+      reason: 'Pull request numbers in mergePullRequest invocations do not match',
+      verifyPullRequestMergeCallMap.keys.toList(),
+      expected.keys.toList(),
+    );
     verifyPullRequestMergeCallMap.forEach((key, value) {
-      assert(expected.containsKey(key));
-      assert(expected[key] == value);
+      expect(value, expected[key]);
     });
   }
 
diff --git a/auto_submit/test/validations/ci_successful_test.dart b/auto_submit/test/validations/ci_successful_test.dart
index 8489d39808..e100d2babe 100644
--- a/auto_submit/test/validations/ci_successful_test.dart
+++ b/auto_submit/test/validations/ci_successful_test.dart
@@ -9,6 +9,7 @@ import 'dart:core';
 import 'package:auto_submit/configuration/repository_configuration.dart';
 import 'package:auto_submit/model/auto_submit_query_result.dart';
 import 'package:auto_submit/model/pull_request_data_types.dart';
+import 'package:auto_submit/service/config.dart';
 import 'package:auto_submit/validations/ci_successful.dart';
 import 'package:auto_submit/validations/validation.dart';
 import 'package:cocoon_server/logging.dart';
@@ -277,7 +278,7 @@ void main() {
       final Author author = Author(login: 'ricardoamador');
 
       final List<String> labelNames = [];
-      labelNames.add('warning: land on red to fix tree breakage');
+      labelNames.add(Config.kEmergencyLabel);
       labelNames.add('Other label');
 
       convertContextNodeStatuses(contextNodeList);
@@ -519,7 +520,7 @@ void main() {
 
       /// The status must be uppercase as the original code is expecting this.
       convertContextNodeStatuses(contextNodeList);
-      final bool treeStatusFlag = ciSuccessful.treeStatusCheck(slug, prNumber, contextNodeList);
+      final bool treeStatusFlag = ciSuccessful.isTreeStatusReporting(slug, prNumber, contextNodeList);
       expect(treeStatusFlag, true);
     });
 
@@ -530,7 +531,7 @@ void main() {
 
       /// The status must be uppercase as the original code is expecting this.
       convertContextNodeStatuses(contextNodeList);
-      final bool treeStatusFlag = ciSuccessful.treeStatusCheck(slug, prNumber, contextNodeList);
+      final bool treeStatusFlag = ciSuccessful.isTreeStatusReporting(slug, prNumber, contextNodeList);
       expect(treeStatusFlag, true);
     });
 
@@ -540,7 +541,7 @@ void main() {
 
       /// The status must be uppercase as the original code is expecting this.
       convertContextNodeStatuses(contextNodeList);
-      final bool treeStatusFlag = ciSuccessful.treeStatusCheck(slug, prNumber, contextNodeList);
+      final bool treeStatusFlag = ciSuccessful.isTreeStatusReporting(slug, prNumber, contextNodeList);
       expect(treeStatusFlag, false);
     });
   });
@@ -663,7 +664,7 @@ void main() {
       expect(commit, isNotNull);
       expect(commit.status, isNotNull);
 
-      final github.PullRequest npr = generatePullRequest(labelName: 'warning: land on red to fix tree breakage');
+      final github.PullRequest npr = generatePullRequest(labelName: Config.kEmergencyLabel);
       githubService.checkRunsData = checkRunsMock;
 
       ciSuccessful.validate(queryResult, npr).then((value) {