diff --git a/src/__phutil_library_map__.php b/src/__phutil_library_map__.php
--- a/src/__phutil_library_map__.php
+++ b/src/__phutil_library_map__.php
@@ -653,6 +653,7 @@
     'DifferentialRevisionUpdateTransaction' => 'applications/differential/xaction/DifferentialRevisionUpdateTransaction.php',
     'DifferentialRevisionViewController' => 'applications/differential/controller/DifferentialRevisionViewController.php',
     'DifferentialRevisionVoidTransaction' => 'applications/differential/xaction/DifferentialRevisionVoidTransaction.php',
+    'DifferentialRevisionWrongBuildsTransaction' => 'applications/differential/xaction/DifferentialRevisionWrongBuildsTransaction.php',
     'DifferentialRevisionWrongStateTransaction' => 'applications/differential/xaction/DifferentialRevisionWrongStateTransaction.php',
     'DifferentialSchemaSpec' => 'applications/differential/storage/DifferentialSchemaSpec.php',
     'DifferentialSetDiffPropertyConduitAPIMethod' => 'applications/differential/conduit/DifferentialSetDiffPropertyConduitAPIMethod.php',
@@ -6181,6 +6182,7 @@
     'DifferentialRevisionUpdateTransaction' => 'DifferentialRevisionTransactionType',
     'DifferentialRevisionViewController' => 'DifferentialController',
     'DifferentialRevisionVoidTransaction' => 'DifferentialRevisionTransactionType',
+    'DifferentialRevisionWrongBuildsTransaction' => 'DifferentialRevisionTransactionType',
     'DifferentialRevisionWrongStateTransaction' => 'DifferentialRevisionTransactionType',
     'DifferentialSchemaSpec' => 'PhabricatorConfigSchemaSpec',
     'DifferentialSetDiffPropertyConduitAPIMethod' => 'DifferentialConduitAPIMethod',
diff --git a/src/applications/differential/engine/DifferentialDiffExtractionEngine.php b/src/applications/differential/engine/DifferentialDiffExtractionEngine.php
--- a/src/applications/differential/engine/DifferentialDiffExtractionEngine.php
+++ b/src/applications/differential/engine/DifferentialDiffExtractionEngine.php
@@ -285,6 +285,24 @@
         ->setNewValue($revision->getModernRevisionStatus());
     }
 
+    $concerning_builds = $this->loadConcerningBuilds($revision);
+    if ($concerning_builds) {
+      $build_list = array();
+      foreach ($concerning_builds as $build) {
+        $build_list[] = array(
+          'phid' => $build->getPHID(),
+          'status' => $build->getBuildStatus(),
+        );
+      }
+
+      $wrong_builds =
+        DifferentialRevisionWrongBuildsTransaction::TRANSACTIONTYPE;
+
+      $xactions[] = id(new DifferentialTransaction())
+        ->setTransactionType($wrong_builds)
+        ->setNewValue($build_list);
+    }
+
     $type_update = DifferentialRevisionUpdateTransaction::TRANSACTIONTYPE;
 
     $xactions[] = id(new DifferentialTransaction())
@@ -322,4 +340,81 @@
     return $result_data;
   }
 
+  private function loadConcerningBuilds(DifferentialRevision $revision) {
+    $viewer = $this->getViewer();
+    $diff = $revision->getActiveDiff();
+
+    $buildables = id(new HarbormasterBuildableQuery())
+      ->setViewer($viewer)
+      ->withBuildablePHIDs(array($diff->getPHID()))
+      ->needBuilds(true)
+      ->withManualBuildables(false)
+      ->execute();
+    if (!$buildables) {
+      return array();
+    }
+
+
+    $land_key = HarbormasterBuildPlanBehavior::BEHAVIOR_LANDWARNING;
+    $behavior = HarbormasterBuildPlanBehavior::getBehavior($land_key);
+
+    $key_never = HarbormasterBuildPlanBehavior::LANDWARNING_NEVER;
+    $key_building = HarbormasterBuildPlanBehavior::LANDWARNING_IF_BUILDING;
+    $key_complete = HarbormasterBuildPlanBehavior::LANDWARNING_IF_COMPLETE;
+
+    $concerning_builds = array();
+    foreach ($buildables as $buildable) {
+      $builds = $buildable->getBuilds();
+      foreach ($builds as $build) {
+        $plan = $build->getBuildPlan();
+        $option = $behavior->getPlanOption($plan);
+        $behavior_value = $option->getKey();
+
+        $if_never = ($behavior_value === $key_never);
+        if ($if_never) {
+          continue;
+        }
+
+        $if_building = ($behavior_value === $key_building);
+        if ($if_building && $build->isComplete()) {
+          continue;
+        }
+
+        $if_complete = ($behavior_value === $key_complete);
+        if ($if_complete) {
+          if (!$build->isComplete()) {
+            continue;
+          }
+
+          // TODO: If you "arc land" and a build with "Warn: If Complete"
+          // is still running, you may not see a warning, and push the revision
+          // in good faith. The build may then complete before we get here, so
+          // we now see a completed, failed build.
+
+          // For now, just err on the side of caution and assume these builds
+          // were in a good state when we prompted the user, even if they're in
+          // a bad state now.
+
+          // We could refine this with a rule like "if the build finished
+          // within a couple of minutes before the push happened, assume it was
+          // in good faith", but we don't currently have an especially
+          // convenient way to check when the build finished or when the commit
+          // was pushed or discovered, and this would create some issues in
+          // cases where the repository is observed and the fetch pipeline
+          // stalls for a while.
+
+          continue;
+        }
+
+        if ($build->isPassed()) {
+          continue;
+        }
+
+        $concerning_builds[] = $build;
+      }
+    }
+
+    return $concerning_builds;
+  }
+
 }
diff --git a/src/applications/differential/xaction/DifferentialRevisionWrongBuildsTransaction.php b/src/applications/differential/xaction/DifferentialRevisionWrongBuildsTransaction.php
new file mode 100644
--- /dev/null
+++ b/src/applications/differential/xaction/DifferentialRevisionWrongBuildsTransaction.php
@@ -0,0 +1,37 @@
+<?php
+
+final class DifferentialRevisionWrongBuildsTransaction
+  extends DifferentialRevisionTransactionType {
+
+  const TRANSACTIONTYPE = 'differential.builds.wrong';
+
+  public function generateOldValue($object) {
+    return null;
+  }
+
+  public function generateNewValue($object, $value) {
+    return $value;
+  }
+
+  public function getIcon() {
+    return 'fa-exclamation';
+  }
+
+  public function getColor() {
+    return 'pink';
+  }
+
+  public function getActionStrength() {
+    return 4;
+  }
+
+  public function getTitle() {
+    return pht(
+      'This revision was landed with ongoing or failed builds.');
+  }
+
+  public function shouldHideForFeed() {
+    return true;
+  }
+
+}
diff --git a/src/applications/harbormaster/plan/HarbormasterBuildPlanBehavior.php b/src/applications/harbormaster/plan/HarbormasterBuildPlanBehavior.php
--- a/src/applications/harbormaster/plan/HarbormasterBuildPlanBehavior.php
+++ b/src/applications/harbormaster/plan/HarbormasterBuildPlanBehavior.php
@@ -27,6 +27,12 @@
   const BUILDABLE_IF_BUILDING = 'building';
   const BUILDABLE_NEVER = 'never';
 
+  const BEHAVIOR_LANDWARNING = 'arc-land';
+  const LANDWARNING_ALWAYS = 'always';
+  const LANDWARNING_IF_BUILDING = 'building';
+  const LANDWARNING_IF_COMPLETE = 'complete';
+  const LANDWARNING_NEVER = 'never';
+
   public function setKey($key) {
     $this->key = $key;
     return $this;
@@ -176,7 +182,7 @@
 
     $land_options = array(
       id(new HarbormasterBuildPlanBehaviorOption())
-        ->setKey('always')
+        ->setKey(self::LANDWARNING_ALWAYS)
         ->setIcon('fa-check-circle-o green')
         ->setName(pht('Always'))
         ->setIsDefault(true)
@@ -185,7 +191,7 @@
             '"arc land" warns if the build is still running or has '.
             'failed.')),
       id(new HarbormasterBuildPlanBehaviorOption())
-        ->setKey('building')
+        ->setKey(self::LANDWARNING_IF_BUILDING)
         ->setIcon('fa-pause-circle-o yellow')
         ->setName(pht('If Building'))
         ->setDescription(
@@ -193,7 +199,7 @@
             '"arc land" warns if the build is still running, but ignores '.
             'the build if it has failed.')),
       id(new HarbormasterBuildPlanBehaviorOption())
-        ->setKey('complete')
+        ->setKey(self::LANDWARNING_IF_COMPLETE)
         ->setIcon('fa-dot-circle-o yellow')
         ->setName(pht('If Complete'))
         ->setDescription(
@@ -201,7 +207,7 @@
             '"arc land" warns if the build has failed, but ignores the '.
             'build if it is still running.')),
       id(new HarbormasterBuildPlanBehaviorOption())
-        ->setKey('never')
+        ->setKey(self::LANDWARNING_NEVER)
         ->setIcon('fa-circle-o red')
         ->setName(pht('Never'))
         ->setDescription(
@@ -296,7 +302,7 @@
             'revision, even if builds have failed or are still in progress.'))
         ->setOptions($draft_options),
       id(new self())
-        ->setKey('arc-land')
+        ->setKey(self::BEHAVIOR_LANDWARNING)
         ->setName(pht('Warn When Landing'))
         ->setEditInstructions(
           pht(
@@ -312,7 +318,10 @@
             'for it) or the outcome is not important.'.
             "\n\n".
             'This warning is only advisory. Users may always elect to ignore '.
-            'this warning and continue, even if builds have failed.'))
+            'this warning and continue, even if builds have failed.'.
+            "\n\n".
+            'This setting also affects the warning that is published to '.
+            'revisions when commits land with ongoing or failed builds.'))
         ->setOptions($land_options),
       id(new self())
         ->setKey(self::BEHAVIOR_BUILDABLE)