diff --git a/src/__phutil_library_map__.php b/src/__phutil_library_map__.php
index 447d4a534e..32c80d75a1 100644
--- a/src/__phutil_library_map__.php
+++ b/src/__phutil_library_map__.php
@@ -380,6 +380,7 @@ phutil_register_library_map(array(
     'DifferentialBlockHeraldAction' => 'applications/differential/herald/DifferentialBlockHeraldAction.php',
     'DifferentialBlockingReviewerDatasource' => 'applications/differential/typeahead/DifferentialBlockingReviewerDatasource.php',
     'DifferentialBranchField' => 'applications/differential/customfield/DifferentialBranchField.php',
+    'DifferentialBuildableEngine' => 'applications/differential/harbormaster/DifferentialBuildableEngine.php',
     'DifferentialChangeDetailMailView' => 'applications/differential/mail/DifferentialChangeDetailMailView.php',
     'DifferentialChangeHeraldFieldGroup' => 'applications/differential/herald/DifferentialChangeHeraldFieldGroup.php',
     'DifferentialChangeType' => 'applications/differential/constants/DifferentialChangeType.php',
@@ -638,6 +639,7 @@ phutil_register_library_map(array(
     'DiffusionBrowseQueryConduitAPIMethod' => 'applications/diffusion/conduit/DiffusionBrowseQueryConduitAPIMethod.php',
     'DiffusionBrowseResultSet' => 'applications/diffusion/data/DiffusionBrowseResultSet.php',
     'DiffusionBrowseTableView' => 'applications/diffusion/view/DiffusionBrowseTableView.php',
+    'DiffusionBuildableEngine' => 'applications/diffusion/harbormaster/DiffusionBuildableEngine.php',
     'DiffusionCacheEngineExtension' => 'applications/diffusion/engineextension/DiffusionCacheEngineExtension.php',
     'DiffusionCachedResolveRefsQuery' => 'applications/diffusion/query/DiffusionCachedResolveRefsQuery.php',
     'DiffusionChangeController' => 'applications/diffusion/controller/DiffusionChangeController.php',
@@ -1285,6 +1287,7 @@ phutil_register_library_map(array(
     'HarbormasterBuildable' => 'applications/harbormaster/storage/HarbormasterBuildable.php',
     'HarbormasterBuildableActionController' => 'applications/harbormaster/controller/HarbormasterBuildableActionController.php',
     'HarbormasterBuildableAdapterInterface' => 'applications/harbormaster/herald/HarbormasterBuildableAdapterInterface.php',
+    'HarbormasterBuildableEngine' => 'applications/harbormaster/engine/HarbormasterBuildableEngine.php',
     'HarbormasterBuildableInterface' => 'applications/harbormaster/interface/HarbormasterBuildableInterface.php',
     'HarbormasterBuildableListController' => 'applications/harbormaster/controller/HarbormasterBuildableListController.php',
     'HarbormasterBuildablePHIDType' => 'applications/harbormaster/phid/HarbormasterBuildablePHIDType.php',
@@ -5586,6 +5589,7 @@ phutil_register_library_map(array(
     'DifferentialBlockHeraldAction' => 'HeraldAction',
     'DifferentialBlockingReviewerDatasource' => 'PhabricatorTypeaheadCompositeDatasource',
     'DifferentialBranchField' => 'DifferentialCustomField',
+    'DifferentialBuildableEngine' => 'HarbormasterBuildableEngine',
     'DifferentialChangeDetailMailView' => 'DifferentialMailView',
     'DifferentialChangeHeraldFieldGroup' => 'HeraldFieldGroup',
     'DifferentialChangeType' => 'Phobject',
@@ -5883,6 +5887,7 @@ phutil_register_library_map(array(
     'DiffusionBrowseQueryConduitAPIMethod' => 'DiffusionQueryConduitAPIMethod',
     'DiffusionBrowseResultSet' => 'Phobject',
     'DiffusionBrowseTableView' => 'DiffusionView',
+    'DiffusionBuildableEngine' => 'HarbormasterBuildableEngine',
     'DiffusionCacheEngineExtension' => 'PhabricatorCacheEngineExtension',
     'DiffusionCachedResolveRefsQuery' => 'DiffusionLowLevelQuery',
     'DiffusionChangeController' => 'DiffusionController',
@@ -6636,6 +6641,7 @@ phutil_register_library_map(array(
       'PhabricatorDestructibleInterface',
     ),
     'HarbormasterBuildableActionController' => 'HarbormasterController',
+    'HarbormasterBuildableEngine' => 'Phobject',
     'HarbormasterBuildableListController' => 'HarbormasterController',
     'HarbormasterBuildablePHIDType' => 'PhabricatorPHIDType',
     'HarbormasterBuildableQuery' => 'PhabricatorCursorPagedPolicyAwareQuery',
diff --git a/src/applications/differential/harbormaster/DifferentialBuildableEngine.php b/src/applications/differential/harbormaster/DifferentialBuildableEngine.php
new file mode 100644
index 0000000000..9ba44d9b81
--- /dev/null
+++ b/src/applications/differential/harbormaster/DifferentialBuildableEngine.php
@@ -0,0 +1,4 @@
+<?php
+
+final class DifferentialBuildableEngine
+  extends HarbormasterBuildableEngine {}
diff --git a/src/applications/differential/storage/DifferentialDiff.php b/src/applications/differential/storage/DifferentialDiff.php
index 85ffccc4a3..9a352af48c 100644
--- a/src/applications/differential/storage/DifferentialDiff.php
+++ b/src/applications/differential/storage/DifferentialDiff.php
@@ -557,6 +557,10 @@ final class DifferentialDiff
     );
   }
 
+  public function newBuildableEngine() {
+    return new DifferentialBuildableEngine();
+  }
+
 
 /* -(  HarbormasterCircleCIBuildableInterface  )----------------------------- */
 
diff --git a/src/applications/differential/storage/DifferentialRevision.php b/src/applications/differential/storage/DifferentialRevision.php
index 6813c124d7..45deef4616 100644
--- a/src/applications/differential/storage/DifferentialRevision.php
+++ b/src/applications/differential/storage/DifferentialRevision.php
@@ -800,6 +800,10 @@ final class DifferentialRevision extends DifferentialDAO
     return array();
   }
 
+  public function newBuildableEngine() {
+    return new DifferentialBuildableEngine();
+  }
+
 
 /* -(  PhabricatorSubscribableInterface  )----------------------------------- */
 
diff --git a/src/applications/diffusion/harbormaster/DiffusionBuildableEngine.php b/src/applications/diffusion/harbormaster/DiffusionBuildableEngine.php
new file mode 100644
index 0000000000..b0cb591b46
--- /dev/null
+++ b/src/applications/diffusion/harbormaster/DiffusionBuildableEngine.php
@@ -0,0 +1,4 @@
+<?php
+
+final class DiffusionBuildableEngine
+  extends HarbormasterBuildableEngine {}
diff --git a/src/applications/harbormaster/engine/HarbormasterBuildableEngine.php b/src/applications/harbormaster/engine/HarbormasterBuildableEngine.php
new file mode 100644
index 0000000000..5e35f6223e
--- /dev/null
+++ b/src/applications/harbormaster/engine/HarbormasterBuildableEngine.php
@@ -0,0 +1,4 @@
+<?php
+
+abstract class HarbormasterBuildableEngine
+  extends Phobject {}
diff --git a/src/applications/harbormaster/interface/HarbormasterBuildableInterface.php b/src/applications/harbormaster/interface/HarbormasterBuildableInterface.php
index 598f2b61f0..9994baba21 100644
--- a/src/applications/harbormaster/interface/HarbormasterBuildableInterface.php
+++ b/src/applications/harbormaster/interface/HarbormasterBuildableInterface.php
@@ -36,4 +36,6 @@ interface HarbormasterBuildableInterface {
   public function getBuildVariables();
   public function getAvailableBuildVariables();
 
+  public function newBuildableEngine();
+
 }
diff --git a/src/applications/harbormaster/storage/HarbormasterBuildable.php b/src/applications/harbormaster/storage/HarbormasterBuildable.php
index 3a092900eb..91b24c7b7b 100644
--- a/src/applications/harbormaster/storage/HarbormasterBuildable.php
+++ b/src/applications/harbormaster/storage/HarbormasterBuildable.php
@@ -341,6 +341,10 @@ final class HarbormasterBuildable
     return array();
   }
 
+  public function newBuildableEngine() {
+    return $this->getBuildableObject()->newBuildableEngine();
+  }
+
 
 /* -(  PhabricatorDestructibleInterface  )----------------------------------- */
 
diff --git a/src/applications/repository/storage/PhabricatorRepositoryCommit.php b/src/applications/repository/storage/PhabricatorRepositoryCommit.php
index b3b344312c..1bc0930e67 100644
--- a/src/applications/repository/storage/PhabricatorRepositoryCommit.php
+++ b/src/applications/repository/storage/PhabricatorRepositoryCommit.php
@@ -549,6 +549,10 @@ final class PhabricatorRepositoryCommit
     );
   }
 
+  public function newBuildableEngine() {
+    return new DiffusionBuildableEngine();
+  }
+
 
 /* -(  HarbormasterCircleCIBuildableInterface  )----------------------------- */