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
@@ -1422,8 +1422,10 @@
     'ManiphestTaskHasCommitRelationship' => 'applications/maniphest/relationship/ManiphestTaskHasCommitRelationship.php',
     'ManiphestTaskHasMockEdgeType' => 'applications/maniphest/edge/ManiphestTaskHasMockEdgeType.php',
     'ManiphestTaskHasMockRelationship' => 'applications/maniphest/relationship/ManiphestTaskHasMockRelationship.php',
+    'ManiphestTaskHasParentRelationship' => 'applications/maniphest/relationship/ManiphestTaskHasParentRelationship.php',
     'ManiphestTaskHasRevisionEdgeType' => 'applications/maniphest/edge/ManiphestTaskHasRevisionEdgeType.php',
     'ManiphestTaskHasRevisionRelationship' => 'applications/maniphest/relationship/ManiphestTaskHasRevisionRelationship.php',
+    'ManiphestTaskHasSubtaskRelationship' => 'applications/maniphest/relationship/ManiphestTaskHasSubtaskRelationship.php',
     'ManiphestTaskHeraldField' => 'applications/maniphest/herald/ManiphestTaskHeraldField.php',
     'ManiphestTaskHeraldFieldGroup' => 'applications/maniphest/herald/ManiphestTaskHeraldFieldGroup.php',
     'ManiphestTaskListController' => 'applications/maniphest/controller/ManiphestTaskListController.php',
@@ -5913,8 +5915,10 @@
     'ManiphestTaskHasCommitRelationship' => 'ManiphestTaskRelationship',
     'ManiphestTaskHasMockEdgeType' => 'PhabricatorEdgeType',
     'ManiphestTaskHasMockRelationship' => 'ManiphestTaskRelationship',
+    'ManiphestTaskHasParentRelationship' => 'ManiphestTaskRelationship',
     'ManiphestTaskHasRevisionEdgeType' => 'PhabricatorEdgeType',
     'ManiphestTaskHasRevisionRelationship' => 'ManiphestTaskRelationship',
+    'ManiphestTaskHasSubtaskRelationship' => 'ManiphestTaskRelationship',
     'ManiphestTaskHeraldField' => 'HeraldField',
     'ManiphestTaskHeraldFieldGroup' => 'HeraldFieldGroup',
     'ManiphestTaskListController' => 'ManiphestController',
diff --git a/src/applications/auth/controller/PhabricatorAuthStartController.php b/src/applications/auth/controller/PhabricatorAuthStartController.php
--- a/src/applications/auth/controller/PhabricatorAuthStartController.php
+++ b/src/applications/auth/controller/PhabricatorAuthStartController.php
@@ -225,10 +225,10 @@
     }
 
     // Often, users end up here by clicking a disabled action link in the UI
-    // (for example, they might click "Edit Blocking Tasks" on a Maniphest
-    // task page). After they log in we want to send them back to that main
-    // object page if we can, since it's confusing to end up on a standalone
-    // page with only a dialog (particularly if that dialog is another error,
+    // (for example, they might click "Edit Subtasks" on a Maniphest task
+    // page). After they log in we want to send them back to that main object
+    // page if we can, since it's confusing to end up on a standalone page with
+    // only a dialog (particularly if that dialog is another error,
     // like a policy exception).
 
     $via_header = AphrontRequest::getViaHeaderName();
diff --git a/src/applications/maniphest/controller/ManiphestTaskDetailController.php b/src/applications/maniphest/controller/ManiphestTaskDetailController.php
--- a/src/applications/maniphest/controller/ManiphestTaskDetailController.php
+++ b/src/applications/maniphest/controller/ManiphestTaskDetailController.php
@@ -195,12 +195,18 @@
       ->setDisabled(!$can_create)
       ->setWorkflow(!$can_create);
 
-    $task_submenu[] = id(new PhabricatorActionView())
-      ->setName(pht('Edit Blocking Tasks'))
-      ->setHref("/search/attach/{$phid}/TASK/blocks/")
-      ->setIcon('fa-link')
-      ->setDisabled(!$can_edit)
-      ->setWorkflow(true);
+    $relationship_list = PhabricatorObjectRelationshipList::newForObject(
+      $viewer,
+      $task);
+
+    $parent_key = ManiphestTaskHasParentRelationship::RELATIONSHIPKEY;
+    $subtask_key = ManiphestTaskHasSubtaskRelationship::RELATIONSHIPKEY;
+
+    $task_submenu[] = $relationship_list->getRelationship($parent_key)
+      ->newAction($task);
+
+    $task_submenu[] = $relationship_list->getRelationship($subtask_key)
+      ->newAction($task);
 
     $task_submenu[] = id(new PhabricatorActionView())
       ->setName(pht('Merge Duplicates In'))
@@ -215,10 +221,6 @@
         ->setIcon('fa-anchor')
         ->setSubmenu($task_submenu));
 
-    $relationship_list = PhabricatorObjectRelationshipList::newForObject(
-      $viewer,
-      $task);
-
     $relationship_submenu = $relationship_list->newActionMenu();
     if ($relationship_submenu) {
       $curtain->addAction($relationship_submenu);
@@ -288,9 +290,9 @@
 
     $edge_types = array(
       ManiphestTaskDependedOnByTaskEdgeType::EDGECONST
-        => pht('Blocks'),
+        => pht('Parent Tasks'),
       ManiphestTaskDependsOnTaskEdgeType::EDGECONST
-        => pht('Blocked By'),
+        => pht('Subtasks'),
       ManiphestTaskHasRevisionEdgeType::EDGECONST
         => pht('Differential Revisions'),
       ManiphestTaskHasMockEdgeType::EDGECONST
diff --git a/src/applications/maniphest/edge/ManiphestTaskDependedOnByTaskEdgeType.php b/src/applications/maniphest/edge/ManiphestTaskDependedOnByTaskEdgeType.php
--- a/src/applications/maniphest/edge/ManiphestTaskDependedOnByTaskEdgeType.php
+++ b/src/applications/maniphest/edge/ManiphestTaskDependedOnByTaskEdgeType.php
@@ -17,7 +17,7 @@
     $add_edges) {
 
     return pht(
-      '%s added %s blocked task(s): %s.',
+      '%s added %s parent task(s): %s.',
       $actor,
       $add_count,
       $add_edges);
@@ -29,7 +29,7 @@
     $rem_edges) {
 
     return pht(
-      '%s removed %s blocked task(s): %s.',
+      '%s removed %s parent task(s): %s.',
       $actor,
       $rem_count,
       $rem_edges);
@@ -44,7 +44,7 @@
     $rem_edges) {
 
     return pht(
-      '%s edited blocked task(s), added %s: %s; removed %s: %s.',
+      '%s edited parent task(s), added %s: %s; removed %s: %s.',
       $actor,
       $add_count,
       $add_edges,
@@ -59,7 +59,7 @@
     $add_edges) {
 
     return pht(
-      '%s added %s blocked task(s) for %s: %s.',
+      '%s added %s parent task(s) for %s: %s.',
       $actor,
       $add_count,
       $object,
@@ -73,7 +73,7 @@
     $rem_edges) {
 
     return pht(
-      '%s removed %s blocked task(s) for %s: %s.',
+      '%s removed %s parent task(s) for %s: %s.',
       $actor,
       $rem_count,
       $object,
@@ -90,7 +90,7 @@
     $rem_edges) {
 
     return pht(
-      '%s edited blocked task(s) for %s, added %s: %s; removed %s: %s.',
+      '%s edited parent task(s) for %s, added %s: %s; removed %s: %s.',
       $actor,
       $object,
       $add_count,
diff --git a/src/applications/maniphest/edge/ManiphestTaskDependsOnTaskEdgeType.php b/src/applications/maniphest/edge/ManiphestTaskDependsOnTaskEdgeType.php
--- a/src/applications/maniphest/edge/ManiphestTaskDependsOnTaskEdgeType.php
+++ b/src/applications/maniphest/edge/ManiphestTaskDependsOnTaskEdgeType.php
@@ -22,7 +22,7 @@
     $add_edges) {
 
     return pht(
-      '%s added %s blocking task(s): %s.',
+      '%s added %s subtask(s): %s.',
       $actor,
       $add_count,
       $add_edges);
@@ -34,7 +34,7 @@
     $rem_edges) {
 
     return pht(
-      '%s removed %s blocking task(s): %s.',
+      '%s removed %s subtask(s): %s.',
       $actor,
       $rem_count,
       $rem_edges);
@@ -49,7 +49,7 @@
     $rem_edges) {
 
     return pht(
-      '%s edited blocking task(s), added %s: %s; removed %s: %s.',
+      '%s edited subtask(s), added %s: %s; removed %s: %s.',
       $actor,
       $add_count,
       $add_edges,
@@ -64,7 +64,7 @@
     $add_edges) {
 
     return pht(
-      '%s added %s blocking task(s) for %s: %s.',
+      '%s added %s subtask(s) for %s: %s.',
       $actor,
       $add_count,
       $object,
@@ -78,7 +78,7 @@
     $rem_edges) {
 
     return pht(
-      '%s removed %s blocking task(s) for %s: %s.',
+      '%s removed %s subtask(s) for %s: %s.',
       $actor,
       $rem_count,
       $object,
@@ -95,7 +95,7 @@
     $rem_edges) {
 
     return pht(
-      '%s edited blocking task(s) for %s, added %s: %s; removed %s: %s.',
+      '%s edited subtask(s) for %s, added %s: %s; removed %s: %s.',
       $actor,
       $object,
       $add_count,
diff --git a/src/applications/maniphest/editor/ManiphestTransactionEditor.php b/src/applications/maniphest/editor/ManiphestTransactionEditor.php
--- a/src/applications/maniphest/editor/ManiphestTransactionEditor.php
+++ b/src/applications/maniphest/editor/ManiphestTransactionEditor.php
@@ -325,7 +325,7 @@
       ManiphestTransaction::MAILTAG_PROJECTS =>
         pht("A task's associated projects change."),
       ManiphestTransaction::MAILTAG_UNBLOCK =>
-        pht('One of the tasks a task is blocked by changes status.'),
+        pht("One of a task's subtasks changes status."),
       ManiphestTransaction::MAILTAG_COLUMN =>
         pht('A task is moved between columns on a workboard.'),
       ManiphestTransaction::MAILTAG_COMMENT =>
diff --git a/src/applications/maniphest/relationship/ManiphestTaskHasParentRelationship.php b/src/applications/maniphest/relationship/ManiphestTaskHasParentRelationship.php
new file mode 100644
--- /dev/null
+++ b/src/applications/maniphest/relationship/ManiphestTaskHasParentRelationship.php
@@ -0,0 +1,40 @@
+<?php
+
+final class ManiphestTaskHasParentRelationship
+  extends ManiphestTaskRelationship {
+
+  const RELATIONSHIPKEY = 'task.has-parent';
+
+  public function getEdgeConstant() {
+    return ManiphestTaskDependedOnByTaskEdgeType::EDGECONST;
+  }
+
+  protected function getActionName() {
+    return pht('Edit Parent Tasks');
+  }
+
+  protected function getActionIcon() {
+    return 'fa-chevron-circle-up';
+  }
+
+  public function canRelateObjects($src, $dst) {
+    return ($dst instanceof ManiphestTask);
+  }
+
+  public function shouldAppearInActionMenu() {
+    return false;
+  }
+
+  public function getDialogTitleText() {
+    return pht('Edit Parent Tasks');
+  }
+
+  public function getDialogHeaderText() {
+    return pht('Current Parent Tasks');
+  }
+
+  public function getDialogButtonText() {
+    return pht('Save Parent Tasks');
+  }
+
+}
diff --git a/src/applications/maniphest/relationship/ManiphestTaskHasSubtaskRelationship.php b/src/applications/maniphest/relationship/ManiphestTaskHasSubtaskRelationship.php
new file mode 100644
--- /dev/null
+++ b/src/applications/maniphest/relationship/ManiphestTaskHasSubtaskRelationship.php
@@ -0,0 +1,40 @@
+<?php
+
+final class ManiphestTaskHasSubtaskRelationship
+  extends ManiphestTaskRelationship {
+
+  const RELATIONSHIPKEY = 'task.has-subtask';
+
+  public function getEdgeConstant() {
+    return ManiphestTaskDependsOnTaskEdgeType::EDGECONST;
+  }
+
+  protected function getActionName() {
+    return pht('Edit Subtasks');
+  }
+
+  protected function getActionIcon() {
+    return 'fa-chevron-circle-down';
+  }
+
+  public function canRelateObjects($src, $dst) {
+    return ($dst instanceof ManiphestTask);
+  }
+
+  public function shouldAppearInActionMenu() {
+    return false;
+  }
+
+  public function getDialogTitleText() {
+    return pht('Edit Subtasks');
+  }
+
+  public function getDialogHeaderText() {
+    return pht('Current Subtasks');
+  }
+
+  public function getDialogButtonText() {
+    return pht('Save Subtasks');
+  }
+
+}
diff --git a/src/applications/maniphest/storage/ManiphestTransaction.php b/src/applications/maniphest/storage/ManiphestTransaction.php
--- a/src/applications/maniphest/storage/ManiphestTransaction.php
+++ b/src/applications/maniphest/storage/ManiphestTransaction.php
@@ -500,24 +500,24 @@
 
         if ($this->getMetadataValue('blocker.new')) {
           return pht(
-            '%s created blocking task %s.',
+            '%s created subtask %s.',
             $this->renderHandleLink($author_phid),
             $this->renderHandleLink($blocker_phid));
         } else if ($old_closed && !$new_closed) {
           return pht(
-            '%s reopened blocking task %s as "%s".',
+            '%s reopened subtask %s as "%s".',
             $this->renderHandleLink($author_phid),
             $this->renderHandleLink($blocker_phid),
             $new_name);
         } else if (!$old_closed && $new_closed) {
           return pht(
-            '%s closed blocking task %s as "%s".',
+            '%s closed subtask %s as "%s".',
             $this->renderHandleLink($author_phid),
             $this->renderHandleLink($blocker_phid),
             $new_name);
         } else {
           return pht(
-            '%s changed the status of blocking task %s from "%s" to "%s".',
+            '%s changed the status of subtask %s from "%s" to "%s".',
             $this->renderHandleLink($author_phid),
             $this->renderHandleLink($blocker_phid),
             $old_name,
@@ -753,21 +753,21 @@
 
         if ($old_closed && !$new_closed) {
           return pht(
-            '%s reopened %s, a task blocking %s, as "%s".',
+            '%s reopened %s, a subtask of %s, as "%s".',
             $this->renderHandleLink($author_phid),
             $this->renderHandleLink($blocker_phid),
             $this->renderHandleLink($object_phid),
             $new_name);
         } else if (!$old_closed && $new_closed) {
           return pht(
-            '%s closed %s, a task blocking %s, as "%s".',
+            '%s closed %s, a subtask of %s, as "%s".',
             $this->renderHandleLink($author_phid),
             $this->renderHandleLink($blocker_phid),
             $this->renderHandleLink($object_phid),
             $new_name);
         } else {
           return pht(
-            '%s changed the status of %s, a task blocking %s, '.
+            '%s changed the status of %s, a subtasktask of %s, '.
             'from "%s" to "%s".',
             $this->renderHandleLink($author_phid),
             $this->renderHandleLink($blocker_phid),
diff --git a/src/applications/search/controller/PhabricatorSearchRelationshipController.php b/src/applications/search/controller/PhabricatorSearchRelationshipController.php
--- a/src/applications/search/controller/PhabricatorSearchRelationshipController.php
+++ b/src/applications/search/controller/PhabricatorSearchRelationshipController.php
@@ -140,6 +140,8 @@
       ManiphestTaskHasCommitEdgeType::EDGECONST => 'CMIT',
       ManiphestTaskHasMockEdgeType::EDGECONST => 'MOCK',
       ManiphestTaskHasRevisionEdgeType::EDGECONST => 'DREV',
+      ManiphestTaskDependsOnTaskEdgeType::EDGECONST => 'TASK',
+      ManiphestTaskDependedOnByTaskEdgeType::EDGECONST => 'TASK',
     );
 
     $edge_type = $relationship->getEdgeConstant();
@@ -180,12 +182,14 @@
 
     $message = pht(
       'You can not create that relationship because it would create a '.
-      'circular dependency: %s.',
-      implode(" \xE2\x86\x92 ", $names));
+      'circular dependency:');
+
+    $list = implode(" \xE2\x86\x92 ", $names);
 
     return $this->newDialog()
       ->setTitle(pht('Circular Dependency'))
       ->appendParagraph($message)
+      ->appendParagraph($list)
       ->addCancelButton($done_uri);
   }
 
diff --git a/src/applications/transactions/editor/PhabricatorApplicationTransactionEditor.php b/src/applications/transactions/editor/PhabricatorApplicationTransactionEditor.php
--- a/src/applications/transactions/editor/PhabricatorApplicationTransactionEditor.php
+++ b/src/applications/transactions/editor/PhabricatorApplicationTransactionEditor.php
@@ -931,6 +931,7 @@
       $object->openTransaction();
     }
 
+    try {
       foreach ($xactions as $xaction) {
         $this->applyInternalEffects($object, $xaction);
       }
@@ -940,8 +941,6 @@
       try {
         $object->save();
       } catch (AphrontDuplicateKeyQueryException $ex) {
-        $object->killTransaction();
-
         // This callback has an opportunity to throw a better exception,
         // so execution may end here.
         $this->didCatchDuplicateKeyException($object, $xactions, $ex);
@@ -973,7 +972,11 @@
         $read_locking = false;
       }
 
-    $object->saveTransaction();
+      $object->saveTransaction();
+    } catch (Exception $ex) {
+      $object->killTransaction();
+      throw $ex;
+    }
 
     // Now that we've completely applied the core transaction set, try to apply
     // Herald rules. Herald rules are allowed to either take direct actions on
diff --git a/src/infrastructure/edges/editor/PhabricatorEdgeEditor.php b/src/infrastructure/edges/editor/PhabricatorEdgeEditor.php
--- a/src/infrastructure/edges/editor/PhabricatorEdgeEditor.php
+++ b/src/infrastructure/edges/editor/PhabricatorEdgeEditor.php
@@ -134,7 +134,6 @@
       $caught = $ex;
     }
 
-
     if ($caught) {
       $this->killTransactions();
     }
diff --git a/src/infrastructure/internationalization/translation/PhabricatorUSEnglishTranslation.php b/src/infrastructure/internationalization/translation/PhabricatorUSEnglishTranslation.php
--- a/src/infrastructure/internationalization/translation/PhabricatorUSEnglishTranslation.php
+++ b/src/infrastructure/internationalization/translation/PhabricatorUSEnglishTranslation.php
@@ -206,73 +206,73 @@
         ),
       ),
 
-      '%s added %s blocking task(s): %s.' => array(
+      '%s added %s subtask(s): %s.' => array(
         array(
-          '%s added a blocking task: %3$s.',
-          '%s added blocking tasks: %3$s.',
+          '%s added a subtask: %3$s.',
+          '%s added subtasks: %3$s.',
         ),
       ),
 
-      '%s added %s blocked task(s): %s.' => array(
+      '%s added %s parent task(s): %s.' => array(
         array(
-          '%s added a blocked task: %3$s.',
-          '%s added blocked tasks: %3$s.',
+          '%s added a parent task: %3$s.',
+          '%s added parent tasks: %3$s.',
         ),
       ),
 
-      '%s removed %s blocking task(s): %s.' => array(
+      '%s removed %s subtask(s): %s.' => array(
         array(
-          '%s removed a blocking task: %3$s.',
-          '%s removed blocking tasks: %3$s.',
+          '%s removed a subtask: %3$s.',
+          '%s removed subtasks: %3$s.',
         ),
       ),
 
-      '%s removed %s blocked task(s): %s.' => array(
+      '%s removed %s parent task(s): %s.' => array(
         array(
-          '%s removed a blocked task: %3$s.',
-          '%s removed blocked tasks: %3$s.',
+          '%s removed a parent task: %3$s.',
+          '%s removed parent tasks: %3$s.',
         ),
       ),
 
-      '%s added %s blocking task(s) for %s: %s.' => array(
+      '%s added %s subtask(s) for %s: %s.' => array(
         array(
-          '%s added a blocking task for %3$s: %4$s.',
-          '%s added blocking tasks for %3$s: %4$s.',
+          '%s added a subtask for %3$s: %4$s.',
+          '%s added subtasks for %3$s: %4$s.',
         ),
       ),
 
-      '%s added %s blocked task(s) for %s: %s.' => array(
+      '%s added %s parent task(s) for %s: %s.' => array(
         array(
-          '%s added a blocked task for %3$s: %4$s.',
-          '%s added blocked tasks for %3$s: %4$s.',
+          '%s added a parent task for %3$s: %4$s.',
+          '%s added parent tasks for %3$s: %4$s.',
         ),
       ),
 
-      '%s removed %s blocking task(s) for %s: %s.' => array(
+      '%s removed %s subtask(s) for %s: %s.' => array(
         array(
-          '%s removed a blocking task for %3$s: %4$s.',
-          '%s removed blocking tasks for %3$s: %4$s.',
+          '%s removed a subtask for %3$s: %4$s.',
+          '%s removed subtasks for %3$s: %4$s.',
         ),
       ),
 
-      '%s removed %s blocked task(s) for %s: %s.' => array(
+      '%s removed %s parent task(s) for %s: %s.' => array(
         array(
-          '%s removed a blocked task for %3$s: %4$s.',
-          '%s removed blocked tasks for %3$s: %4$s.',
+          '%s removed a parent task for %3$s: %4$s.',
+          '%s removed parent tasks for %3$s: %4$s.',
         ),
       ),
 
-      '%s edited blocking task(s), added %s: %s; removed %s: %s.' =>
-        '%s edited blocking tasks, added: %3$s; removed: %5$s.',
+      '%s edited subtask(s), added %s: %s; removed %s: %s.' =>
+        '%s edited subtasks, added: %3$s; removed: %5$s.',
 
-      '%s edited blocking task(s) for %s, added %s: %s; removed %s: %s.' =>
-        '%s edited blocking tasks for %s, added: %4$s; removed: %6$s.',
+      '%s edited subtask(s) for %s, added %s: %s; removed %s: %s.' =>
+        '%s edited subtasks for %s, added: %4$s; removed: %6$s.',
 
-      '%s edited blocked task(s), added %s: %s; removed %s: %s.' =>
-        '%s edited blocked tasks, added: %3$s; removed: %5$s.',
+      '%s edited parent task(s), added %s: %s; removed %s: %s.' =>
+        '%s edited parent tasks, added: %3$s; removed: %5$s.',
 
-      '%s edited blocked task(s) for %s, added %s: %s; removed %s: %s.' =>
-        '%s edited blocked tasks for %s, added: %4$s; removed: %6$s.',
+      '%s edited parent task(s) for %s, added %s: %s; removed %s: %s.' =>
+        '%s edited parent tasks for %s, added: %4$s; removed: %6$s.',
 
       '%s edited answer(s), added %s: %s; removed %d: %s.' =>
         '%s edited answers, added: %3$s; removed: %5$s.',