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
@@ -1331,6 +1331,7 @@
     'HarbormasterBuildPlanDatasource' => 'applications/harbormaster/typeahead/HarbormasterBuildPlanDatasource.php',
     'HarbormasterBuildPlanDefaultEditCapability' => 'applications/harbormaster/capability/HarbormasterBuildPlanDefaultEditCapability.php',
     'HarbormasterBuildPlanDefaultViewCapability' => 'applications/harbormaster/capability/HarbormasterBuildPlanDefaultViewCapability.php',
+    'HarbormasterBuildPlanEditAPIMethod' => 'applications/harbormaster/conduit/HarbormasterBuildPlanEditAPIMethod.php',
     'HarbormasterBuildPlanEditEngine' => 'applications/harbormaster/editor/HarbormasterBuildPlanEditEngine.php',
     'HarbormasterBuildPlanEditor' => 'applications/harbormaster/editor/HarbormasterBuildPlanEditor.php',
     'HarbormasterBuildPlanNameNgrams' => 'applications/harbormaster/storage/configuration/HarbormasterBuildPlanNameNgrams.php',
@@ -6943,6 +6944,7 @@
     'HarbormasterBuildPlanDatasource' => 'PhabricatorTypeaheadDatasource',
     'HarbormasterBuildPlanDefaultEditCapability' => 'PhabricatorPolicyCapability',
     'HarbormasterBuildPlanDefaultViewCapability' => 'PhabricatorPolicyCapability',
+    'HarbormasterBuildPlanEditAPIMethod' => 'PhabricatorEditEngineAPIMethod',
     'HarbormasterBuildPlanEditEngine' => 'PhabricatorEditEngine',
     'HarbormasterBuildPlanEditor' => 'PhabricatorApplicationTransactionEditor',
     'HarbormasterBuildPlanNameNgrams' => 'PhabricatorSearchNgrams',
diff --git a/src/applications/harbormaster/conduit/HarbormasterBuildPlanEditAPIMethod.php b/src/applications/harbormaster/conduit/HarbormasterBuildPlanEditAPIMethod.php
new file mode 100644
--- /dev/null
+++ b/src/applications/harbormaster/conduit/HarbormasterBuildPlanEditAPIMethod.php
@@ -0,0 +1,20 @@
+<?php
+
+final class HarbormasterBuildPlanEditAPIMethod
+  extends PhabricatorEditEngineAPIMethod {
+
+  public function getAPIMethodName() {
+    return 'harbormaster.buildplan.edit';
+  }
+
+  public function newEditEngine() {
+    return new HarbormasterBuildPlanEditEngine();
+  }
+
+  public function getMethodSummary() {
+    return pht(
+      'Apply transactions to create a new build plan or edit an existing '.
+      'one.');
+  }
+
+}