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
@@ -2951,6 +2951,7 @@
       0 => 'DifferentialDAO',
       1 => 'PhabricatorPolicyInterface',
       2 => 'HarbormasterBuildableInterface',
+      3 => 'PhabricatorApplicationTransactionInterface',
     ),
     'DifferentialDiffCreateController' => 'DifferentialController',
     'DifferentialDiffProperty' => 'DifferentialDAO',
@@ -3015,6 +3016,7 @@
       5 => 'HarbormasterBuildableInterface',
       6 => 'PhabricatorSubscribableInterface',
       7 => 'PhabricatorCustomFieldInterface',
+      8 => 'PhabricatorApplicationTransactionInterface',
     ),
     'DifferentialRevisionDetailView' => 'AphrontView',
     'DifferentialRevisionEditController' => 'DifferentialController',
diff --git a/src/applications/differential/storage/DifferentialDiff.php b/src/applications/differential/storage/DifferentialDiff.php
--- a/src/applications/differential/storage/DifferentialDiff.php
+++ b/src/applications/differential/storage/DifferentialDiff.php
@@ -4,7 +4,8 @@
   extends DifferentialDAO
   implements
     PhabricatorPolicyInterface,
-    HarbormasterBuildableInterface {
+    HarbormasterBuildableInterface,
+    PhabricatorApplicationTransactionInterface {
 
   protected $revisionID;
   protected $authorPHID;
@@ -349,4 +350,30 @@
     return null;
   }
 
+
+/* -(  PhabricatorApplicationTransactionInterface  )------------------------- */
+
+
+  public function getApplicationTransactionEditor() {
+    if (!$this->getRevisionID()) {
+      return null;
+    }
+    return $this->getRevision()->getApplicationTransactionEditor();
+  }
+
+
+  public function getApplicationTransactionObject() {
+    if (!$this->getRevisionID()) {
+      return null;
+    }
+    return $this->getRevision();
+  }
+
+  public function getApplicationTransactionTemplate() {
+    if (!$this->getRevisionID()) {
+      return null;
+    }
+    return $this->getRevision()->getApplicationTransactionTemplate();
+  }
+
 }
diff --git a/src/applications/differential/storage/DifferentialRevision.php b/src/applications/differential/storage/DifferentialRevision.php
--- a/src/applications/differential/storage/DifferentialRevision.php
+++ b/src/applications/differential/storage/DifferentialRevision.php
@@ -8,7 +8,8 @@
     PhrequentTrackableInterface,
     HarbormasterBuildableInterface,
     PhabricatorSubscribableInterface,
-    PhabricatorCustomFieldInterface {
+    PhabricatorCustomFieldInterface,
+    PhabricatorApplicationTransactionInterface {
 
   protected $title = '';
   protected $originalTitle;
@@ -460,4 +461,20 @@
     return $this;
   }
 
+
+/* -(  PhabricatorApplicationTransactionInterface  )------------------------- */
+
+
+  public function getApplicationTransactionEditor() {
+    return new DifferentialTransactionEditor();
+  }
+
+  public function getApplicationTransactionObject() {
+    return $this;
+  }
+
+  public function getApplicationTransactionTemplate() {
+    return new DifferentialTransaction();
+  }
+
 }
diff --git a/src/applications/legalpad/storage/LegalpadDocument.php b/src/applications/legalpad/storage/LegalpadDocument.php
--- a/src/applications/legalpad/storage/LegalpadDocument.php
+++ b/src/applications/legalpad/storage/LegalpadDocument.php
@@ -145,11 +145,16 @@
 
 /* -(  PhabricatorApplicationTransactionInterface  )------------------------- */
 
+
   public function getApplicationTransactionEditor() {
     return new LegalpadDocumentEditor();
   }
 
   public function getApplicationTransactionObject() {
+    return $this;
+  }
+
+  public function getApplicationTransactionTemplate() {
     return new LegalpadTransaction();
   }
 
diff --git a/src/applications/macro/storage/PhabricatorFileImageMacro.php b/src/applications/macro/storage/PhabricatorFileImageMacro.php
--- a/src/applications/macro/storage/PhabricatorFileImageMacro.php
+++ b/src/applications/macro/storage/PhabricatorFileImageMacro.php
@@ -68,6 +68,10 @@
   }
 
   public function getApplicationTransactionObject() {
+    return $this;
+  }
+
+  public function getApplicationTransactionTemplate() {
     return new PhabricatorMacroTransaction();
   }
 
diff --git a/src/applications/pholio/storage/PholioMock.php b/src/applications/pholio/storage/PholioMock.php
--- a/src/applications/pholio/storage/PholioMock.php
+++ b/src/applications/pholio/storage/PholioMock.php
@@ -219,6 +219,10 @@
   }
 
   public function getApplicationTransactionObject() {
+    return $this;
+  }
+
+  public function getApplicationTransactionTemplate() {
     return new PholioTransaction();
   }
 
diff --git a/src/applications/search/controller/PhabricatorSearchAttachController.php b/src/applications/search/controller/PhabricatorSearchAttachController.php
--- a/src/applications/search/controller/PhabricatorSearchAttachController.php
+++ b/src/applications/search/controller/PhabricatorSearchAttachController.php
@@ -70,13 +70,15 @@
           $txn_editor = $object->getApplicationTransactionEditor()
             ->setActor($user)
             ->setContentSourceFromRequest($request);
-          $txn_template = $object->getApplicationTransactionObject()
+          $txn_template = $object->getApplicationTransactionTemplate()
             ->setTransactionType(PhabricatorTransactions::TYPE_EDGE)
             ->setMetadataValue('edge:type', $edge_type)
             ->setNewValue(array(
               '+' => array_fuse($add_phids),
               '-' => array_fuse($rem_phids)));
-          $txn_editor->applyTransactions($object, array($txn_template));
+          $txn_editor->applyTransactions(
+            $object->getApplicationTransactionObject(),
+            array($txn_template));
 
         } else {
 
diff --git a/src/applications/subscriptions/controller/PhabricatorSubscriptionsEditController.php b/src/applications/subscriptions/controller/PhabricatorSubscriptionsEditController.php
--- a/src/applications/subscriptions/controller/PhabricatorSubscriptionsEditController.php
+++ b/src/applications/subscriptions/controller/PhabricatorSubscriptionsEditController.php
@@ -74,7 +74,7 @@
         );
       }
 
-      $xaction = id($object->getApplicationTransactionObject())
+      $xaction = id($object->getApplicationTransactionTemplate())
         ->setTransactionType(PhabricatorTransactions::TYPE_SUBSCRIBERS)
         ->setNewValue($xaction_value);
 
@@ -83,7 +83,9 @@
         ->setContinueOnNoEffect(true)
         ->setContentSourceFromRequest($request);
 
-      $editor->applyTransactions($object, array($xaction));
+      $editor->applyTransactions(
+        $object->getApplicationTransactionObject(),
+        array($xaction));
     } else {
 
       // TODO: Eventually, get rid of this once everything implements
diff --git a/src/applications/transactions/interface/PhabricatorApplicationTransactionInterface.php b/src/applications/transactions/interface/PhabricatorApplicationTransactionInterface.php
--- a/src/applications/transactions/interface/PhabricatorApplicationTransactionInterface.php
+++ b/src/applications/transactions/interface/PhabricatorApplicationTransactionInterface.php
@@ -1,8 +1,38 @@
 <?php
 
+/**
+ * Allow infrastructure to apply transactions to the implementing object.
+ *
+ * For example, implementing this interface allows Subscriptions to apply CC
+ * transactions, and allows Harbormaster to apply build result notifications.
+ */
 interface PhabricatorApplicationTransactionInterface {
 
+  /**
+   * Return a @{class:PhabricatorApplicationTransactionEditor} which can be
+   * used to apply transactions to this object.
+   *
+   * @return PhabricatorApplicationTransactionEditor Editor for this object.
+   */
   public function getApplicationTransactionEditor();
+
+
+  /**
+   * Return the object to apply transactions to. Normally this is the current
+   * object (that is, `$this`), but in some cases transactions may apply to
+   * a different object: for example, @{class:DifferentialDiff} applies
+   * transactions to the associated @{class:DifferentialRevision}.
+   *
+   * @return PhabricatorLiskDAO Object to apply transactions to.
+   */
   public function getApplicationTransactionObject();
 
+
+  /**
+   * Return a template transaction for this object.
+   *
+   * @return PhabricatorApplicationTransaction
+   */
+  public function getApplicationTransactionTemplate();
+
 }