diff --git a/app_dart/lib/src/request_handlers/presubmit_luci_subscription_v2.dart b/app_dart/lib/src/request_handlers/presubmit_luci_subscription_v2.dart
index 5964a011f..a0bdbc81f 100644
--- a/app_dart/lib/src/request_handlers/presubmit_luci_subscription_v2.dart
+++ b/app_dart/lib/src/request_handlers/presubmit_luci_subscription_v2.dart
@@ -143,10 +143,16 @@ class PresubmitLuciSubscriptionV2 extends SubscriptionHandlerV2 {
       sha: userData['commit_sha'] as String,
     );
     late CiYaml ciYaml;
-    if (commit.branch == Config.defaultBranch(commit.slug)) {
-      ciYaml = await scheduler.getCiYaml(commit, validate: true);
-    } else {
-      ciYaml = await scheduler.getCiYaml(commit);
+    try {
+      if (commit.branch == Config.defaultBranch(commit.slug)) {
+        ciYaml = await scheduler.getCiYaml(commit, validate: true);
+      } else {
+        ciYaml = await scheduler.getCiYaml(commit);
+      }
+    } on FormatException {
+      // If ci.yaml no longer passes validation (for example, because a builder
+      // has been removed), ensure no retries.
+      return 0;
     }
 
     // Do not block on the target not found.
diff --git a/app_dart/test/request_handlers/presubmit_luci_subscription_v2_test.dart b/app_dart/test/request_handlers/presubmit_luci_subscription_v2_test.dart
index 4c2144637..7b25fead5 100644
--- a/app_dart/test/request_handlers/presubmit_luci_subscription_v2_test.dart
+++ b/app_dart/test/request_handlers/presubmit_luci_subscription_v2_test.dart
@@ -300,4 +300,58 @@ void main() {
       ),
     ).called(1);
   });
+
+  test('Build not rescheduled if ci.yaml fails validation.', () async {
+    scheduler.failCiYamlValidation = true;
+    when(
+      mockGithubChecksService.updateCheckStatus(
+        build: anyNamed('build'),
+        userDataMap: anyNamed('userDataMap'),
+        luciBuildService: anyNamed('luciBuildService'),
+        slug: anyNamed('slug'),
+        rescheduled: false,
+      ),
+    ).thenAnswer((_) async => true);
+    when(mockGithubChecksService.taskFailed(any)).thenAnswer((_) => true);
+    when(mockGithubChecksService.currentAttempt(any)).thenAnswer((_) => 1);
+
+    final Map<String, dynamic> userDataMap = {
+      'repo_owner': 'flutter',
+      'commit_branch': Config.defaultBranch(Config.flutterSlug),
+      'commit_sha': 'abc',
+      'repo_name': 'flutter',
+    };
+
+    tester.message = createPushMessageV2(
+      Int64(1),
+      status: bbv2.Status.SUCCESS,
+      builder: 'Linux C',
+      userData: userDataMap,
+    );
+
+    final bbv2.BuildsV2PubSub buildsV2PubSub = createBuild(
+      Int64(1),
+      status: bbv2.Status.SUCCESS,
+      builder: 'Linux C',
+    );
+
+    await tester.post(handler);
+    verifyNever(
+      mockLuciBuildService.rescheduleBuild(
+        build: buildsV2PubSub.build,
+        builderName: 'Linux C',
+        userDataMap: userDataMap,
+        rescheduleAttempt: 1,
+      ),
+    );
+    verify(
+      mockGithubChecksService.updateCheckStatus(
+        build: anyNamed('build'),
+        userDataMap: anyNamed('userDataMap'),
+        luciBuildService: anyNamed('luciBuildService'),
+        slug: anyNamed('slug'),
+        rescheduled: false,
+      ),
+    ).called(1);
+  });
 }
diff --git a/app_dart/test/src/service/fake_scheduler_v2.dart b/app_dart/test/src/service/fake_scheduler_v2.dart
index f06e6e9e4..5bf56285b 100644
--- a/app_dart/test/src/service/fake_scheduler_v2.dart
+++ b/app_dart/test/src/service/fake_scheduler_v2.dart
@@ -45,14 +45,22 @@ class FakeSchedulerV2 extends SchedulerV2 {
   /// [CiYaml] value to be injected on [getCiYaml].
   CiYaml? ciYaml;
 
+  /// If true, getCiYaml will throw a [FormatException] when validation is
+  /// enforced, simulating failing validation.
+  bool failCiYamlValidation = false;
+
   @override
   Future<CiYaml> getCiYaml(
     Commit commit, {
     CiYaml? totCiYaml,
     RetryOptions? retryOptions,
     bool validate = false,
-  }) async =>
-      ciYaml ?? _defaultConfig;
+  }) async {
+    if (validate && failCiYamlValidation) {
+      throw const FormatException('Failed validation!');
+    }
+    return ciYaml ?? _defaultConfig;
+  }
 
   @override
   Future<Commit> generateTotCommit({required String branch, required RepositorySlug slug}) async {