diff --git a/src/applications/differential/customfield/DifferentialAuditorsField.php b/src/applications/differential/customfield/DifferentialAuditorsField.php
--- a/src/applications/differential/customfield/DifferentialAuditorsField.php
+++ b/src/applications/differential/customfield/DifferentialAuditorsField.php
@@ -57,4 +57,12 @@
     return $this->renderObjectList($handles);
   }
 
+  public function shouldAppearInConduitTransactions() {
+    return true;
+  }
+
+  protected function newConduitEditParameterType() {
+    return new ConduitPHIDListParameterType();
+  }
+
 }
diff --git a/src/applications/differential/customfield/DifferentialBlameRevisionField.php b/src/applications/differential/customfield/DifferentialBlameRevisionField.php
--- a/src/applications/differential/customfield/DifferentialBlameRevisionField.php
+++ b/src/applications/differential/customfield/DifferentialBlameRevisionField.php
@@ -114,4 +114,12 @@
     return true;
   }
 
+  public function shouldAppearInConduitTransactions() {
+    return true;
+  }
+
+  protected function newConduitEditParameterType() {
+    return new ConduitStringParameterType();
+  }
+
 }
diff --git a/src/applications/differential/customfield/DifferentialCustomField.php b/src/applications/differential/customfield/DifferentialCustomField.php
--- a/src/applications/differential/customfield/DifferentialCustomField.php
+++ b/src/applications/differential/customfield/DifferentialCustomField.php
@@ -20,6 +20,11 @@
     return $this->getFieldKey();
   }
 
+  // TODO: As above.
+  public function getModernFieldKey() {
+    return $this->getFieldKeyForConduit();
+  }
+
   public function shouldEnableForRole($role) {
     switch ($role) {
       case self::ROLE_COMMITMESSAGE:
diff --git a/src/applications/differential/customfield/DifferentialJIRAIssuesField.php b/src/applications/differential/customfield/DifferentialJIRAIssuesField.php
--- a/src/applications/differential/customfield/DifferentialJIRAIssuesField.php
+++ b/src/applications/differential/customfield/DifferentialJIRAIssuesField.php
@@ -295,8 +295,6 @@
     return $this;
   }
 
-
-
   public function renderCommitMessageValue(array $handles) {
     $value = $this->getValue();
     if (!$value) {
@@ -309,5 +307,12 @@
     return true;
   }
 
+  public function shouldAppearInConduitTransactions() {
+    return true;
+  }
+
+  protected function newConduitEditParameterType() {
+    return new ConduitStringListParameterType();
+  }
 
 }
diff --git a/src/applications/differential/customfield/DifferentialRevertPlanField.php b/src/applications/differential/customfield/DifferentialRevertPlanField.php
--- a/src/applications/differential/customfield/DifferentialRevertPlanField.php
+++ b/src/applications/differential/customfield/DifferentialRevertPlanField.php
@@ -142,4 +142,12 @@
     return true;
   }
 
+  public function shouldAppearInConduitTransactions() {
+    return true;
+  }
+
+  protected function newConduitEditParameterType() {
+    return new ConduitStringParameterType();
+  }
+
 }
diff --git a/src/applications/differential/field/DifferentialCommitMessageCustomField.php b/src/applications/differential/field/DifferentialCommitMessageCustomField.php
--- a/src/applications/differential/field/DifferentialCommitMessageCustomField.php
+++ b/src/applications/differential/field/DifferentialCommitMessageCustomField.php
@@ -61,8 +61,12 @@
   }
 
   public function getFieldTransactions($value) {
-    // TODO: Implement this!
-    return array();
+    return array(
+      array(
+        'type' => $this->getCommitMessageFieldKey(),
+        'value' => $value,
+      ),
+    );
   }
 
 }
diff --git a/src/applications/transactions/edittype/PhabricatorEditType.php b/src/applications/transactions/edittype/PhabricatorEditType.php
--- a/src/applications/transactions/edittype/PhabricatorEditType.php
+++ b/src/applications/transactions/edittype/PhabricatorEditType.php
@@ -107,6 +107,13 @@
 
   public function getConduitType() {
     $parameter_type = $this->getConduitParameterType();
+    if (!$parameter_type) {
+      throw new Exception(
+        pht(
+          'Edit type (with key "%s") is missing a Conduit parameter type.',
+          $this->getEditType()));
+    }
+
     return $parameter_type->getTypeName();
   }