diff --git a/src/parser/argument/PhutilArgumentParser.php b/src/parser/argument/PhutilArgumentParser.php
--- a/src/parser/argument/PhutilArgumentParser.php
+++ b/src/parser/argument/PhutilArgumentParser.php
@@ -77,6 +77,7 @@
   private $tagline;
   private $synopsis;
   private $workflows;
+  private $helpWorkflows;
   private $showHelp;
   private $requireArgumentTerminator = false;
   private $sawTerminator = false;
@@ -449,11 +450,13 @@
 
         $flow = $corrected;
       } else {
-        $this->raiseUnknownWorkflow($flow, $corrected);
+        if (!$this->showHelp) {
+          $this->raiseUnknownWorkflow($flow, $corrected);
+        }
       }
     }
 
-    $workflow = $this->workflows[$flow];
+    $workflow = idx($this->workflows, $flow);
 
     if ($this->showHelp) {
       // Make "cmd flow --help" behave like "cmd help flow", not "cmd help".
@@ -471,6 +474,10 @@
       }
     }
 
+    if (!$workflow) {
+      $this->raiseUnknownWorkflow($flow, $corrected);
+    }
+
     $this->argv = array_values($argv);
 
     if ($workflow->shouldParsePartial()) {
@@ -633,6 +640,12 @@
     return $this;
   }
 
+  public function setHelpWorkflows(array $help_workflows) {
+    $help_workflows = mpull($help_workflows, null, 'getName');
+    $this->helpWorkflows = $help_workflows;
+    return $this;
+  }
+
   public function getWorkflows() {
     return $this->workflows;
   }
@@ -684,11 +697,16 @@
       $out[] = null;
     }
 
-    if ($this->workflows) {
+    $workflows = $this->helpWorkflows;
+    if ($workflows === null) {
+      $workflows = $this->workflows;
+    }
+
+    if ($workflows) {
       $has_help = false;
       $out[] = $this->format('**%s**', pht('WORKFLOWS'));
       $out[] = null;
-      $flows = $this->workflows;
+      $flows = $workflows;
       ksort($flows);
       foreach ($flows as $workflow) {
         if ($workflow->getName() == 'help') {
@@ -739,7 +757,12 @@
 
     $indent = ($show_details ? 0 : 6);
 
-    $workflow = idx($this->workflows, strtolower($workflow_name));
+    $workflows = $this->helpWorkflows;
+    if ($workflows === null) {
+      $workflows = $this->workflows;
+    }
+
+    $workflow = idx($workflows, strtolower($workflow_name));
     if (!$workflow) {
       $out[] = $this->indent(
         $indent,
diff --git a/src/parser/argument/workflow/PhutilHelpArgumentWorkflow.php b/src/parser/argument/workflow/PhutilHelpArgumentWorkflow.php
--- a/src/parser/argument/workflow/PhutilHelpArgumentWorkflow.php
+++ b/src/parser/argument/workflow/PhutilHelpArgumentWorkflow.php
@@ -2,17 +2,6 @@
 
 final class PhutilHelpArgumentWorkflow extends PhutilArgumentWorkflow {
 
-  private $runtime;
-
-  public function setRuntime($runtime) {
-    $this->runtime = $runtime;
-    return $this;
-  }
-
-  public function getRuntime() {
-    return $this->runtime;
-  }
-
   protected function didConstruct() {
     $this->setName('help');
     $this->setExamples(<<<EOHELP
@@ -39,47 +28,6 @@
   public function execute(PhutilArgumentParser $args) {
     $with = $args->getArg('help-with-what');
 
-    $runtime = $this->getRuntime();
-    if ($runtime) {
-      $toolset = $runtime->getToolset();
-      if ($toolset->getToolsetKey() === 'arc') {
-        $workflows = $args->getWorkflows();
-
-        $legacy = array();
-
-        $legacy[] = new ArcanistCloseRevisionWorkflow();
-        $legacy[] = new ArcanistCommitWorkflow();
-        $legacy[] = new ArcanistCoverWorkflow();
-        $legacy[] = new ArcanistDiffWorkflow();
-        $legacy[] = new ArcanistExportWorkflow();
-        $legacy[] = new ArcanistGetConfigWorkflow();
-        $legacy[] = new ArcanistSetConfigWorkflow();
-        $legacy[] = new ArcanistInstallCertificateWorkflow();
-        $legacy[] = new ArcanistLandWorkflow();
-        $legacy[] = new ArcanistLintersWorkflow();
-        $legacy[] = new ArcanistLintWorkflow();
-        $legacy[] = new ArcanistListWorkflow();
-        $legacy[] = new ArcanistPatchWorkflow();
-        $legacy[] = new ArcanistPasteWorkflow();
-        $legacy[] = new ArcanistTasksWorkflow();
-        $legacy[] = new ArcanistTodoWorkflow();
-        $legacy[] = new ArcanistUnitWorkflow();
-        $legacy[] = new ArcanistWhichWorkflow();
-
-        foreach ($legacy as $workflow) {
-          // If this workflow has been updated but not removed from the list
-          // above yet, just skip it.
-          if ($workflow instanceof ArcanistArcWorkflow) {
-            continue;
-          }
-
-          $workflows[] = $workflow->newLegacyPhutilWorkflow();
-        }
-
-        $args->setWorkflows($workflows);
-      }
-    }
-
     if (!$with) {
       $args->printHelpAndExit();
     } else {
diff --git a/src/runtime/ArcanistRuntime.php b/src/runtime/ArcanistRuntime.php
--- a/src/runtime/ArcanistRuntime.php
+++ b/src/runtime/ArcanistRuntime.php
@@ -162,6 +162,9 @@
 
     // TOOLSETS: Some day, stop falling through to the old "arc" runtime.
 
+    $help_workflows = $this->getHelpWorkflows($phutil_workflows);
+    $args->setHelpWorkflows($help_workflows);
+
     try {
       return $args->parseWorkflowsFull($phutil_workflows);
     } catch (ArcanistMissingArgumentTerminatorException $terminator_exception) {
@@ -869,4 +872,41 @@
     return $this->toolset;
   }
 
+  private function getHelpWorkflows(array $workflows) {
+    if ($this->getToolset()->getToolsetKey() === 'arc') {
+      $legacy = array();
+
+      $legacy[] = new ArcanistCloseRevisionWorkflow();
+      $legacy[] = new ArcanistCommitWorkflow();
+      $legacy[] = new ArcanistCoverWorkflow();
+      $legacy[] = new ArcanistDiffWorkflow();
+      $legacy[] = new ArcanistExportWorkflow();
+      $legacy[] = new ArcanistGetConfigWorkflow();
+      $legacy[] = new ArcanistSetConfigWorkflow();
+      $legacy[] = new ArcanistInstallCertificateWorkflow();
+      $legacy[] = new ArcanistLandWorkflow();
+      $legacy[] = new ArcanistLintersWorkflow();
+      $legacy[] = new ArcanistLintWorkflow();
+      $legacy[] = new ArcanistListWorkflow();
+      $legacy[] = new ArcanistPatchWorkflow();
+      $legacy[] = new ArcanistPasteWorkflow();
+      $legacy[] = new ArcanistTasksWorkflow();
+      $legacy[] = new ArcanistTodoWorkflow();
+      $legacy[] = new ArcanistUnitWorkflow();
+      $legacy[] = new ArcanistWhichWorkflow();
+
+      foreach ($legacy as $workflow) {
+        // If this workflow has been updated but not removed from the list
+        // above yet, just skip it.
+        if ($workflow instanceof ArcanistArcWorkflow) {
+          continue;
+        }
+
+        $workflows[] = $workflow->newLegacyPhutilWorkflow();
+      }
+    }
+
+    return $workflows;
+  }
+
 }
diff --git a/src/toolset/ArcanistWorkflowArgument.php b/src/toolset/ArcanistWorkflowArgument.php
--- a/src/toolset/ArcanistWorkflowArgument.php
+++ b/src/toolset/ArcanistWorkflowArgument.php
@@ -41,6 +41,11 @@
       $spec['param'] = $parameter;
     }
 
+    $help = $this->getHelp();
+    if ($help !== null) {
+      $spec['help'] = $help;
+    }
+
     return $spec;
   }
 
diff --git a/src/toolset/workflow/ArcanistHelpWorkflow.php b/src/toolset/workflow/ArcanistHelpWorkflow.php
--- a/src/toolset/workflow/ArcanistHelpWorkflow.php
+++ b/src/toolset/workflow/ArcanistHelpWorkflow.php
@@ -8,8 +8,7 @@
   }
 
   public function newPhutilWorkflow() {
-    return id(new PhutilHelpArgumentWorkflow())
-      ->setRuntime($this->getRuntime());
+    return new PhutilHelpArgumentWorkflow();
   }
 
   public function supportsToolset(ArcanistToolset $toolset) {