Index: src/__phutil_library_map__.php
===================================================================
--- src/__phutil_library_map__.php
+++ src/__phutil_library_map__.php
@@ -91,7 +91,6 @@
     'AphrontView' => 'view/AphrontView.php',
     'AphrontWebpageResponse' => 'aphront/response/AphrontWebpageResponse.php',
     'AuditActionMenuEventListener' => 'applications/audit/events/AuditActionMenuEventListener.php',
-    'BuildStepImplementation' => 'applications/harbormaster/step/BuildStepImplementation.php',
     'CelerityAPI' => 'infrastructure/celerity/CelerityAPI.php',
     'CelerityPhabricatorResourceController' => 'infrastructure/celerity/CelerityPhabricatorResourceController.php',
     'CelerityResourceController' => 'infrastructure/celerity/CelerityResourceController.php',
@@ -104,6 +103,8 @@
     'ConduitAPIMethod' => 'applications/conduit/method/ConduitAPIMethod.php',
     'ConduitAPIRequest' => 'applications/conduit/protocol/ConduitAPIRequest.php',
     'ConduitAPIResponse' => 'applications/conduit/protocol/ConduitAPIResponse.php',
+    'ConduitAPI_agent_Method' => 'applications/harbormaster/conduit/ConduitAPI_agent_Method.php',
+    'ConduitAPI_agent_nextbuild_Method' => 'applications/harbormaster/conduit/ConduitAPI_agent_nextbuild_Method.php',
     'ConduitAPI_arcanist_Method' => 'applications/arcanist/conduit/ConduitAPI_arcanist_Method.php',
     'ConduitAPI_arcanist_projectinfo_Method' => 'applications/arcanist/conduit/ConduitAPI_arcanist_projectinfo_Method.php',
     'ConduitAPI_audit_Method' => 'applications/audit/conduit/ConduitAPI_audit_Method.php',
@@ -2199,7 +2200,6 @@
     'ReleephStatusFieldSpecification' => 'applications/releeph/field/specification/ReleephStatusFieldSpecification.php',
     'ReleephSummaryFieldSpecification' => 'applications/releeph/field/specification/ReleephSummaryFieldSpecification.php',
     'ReleephUserView' => 'applications/releeph/view/user/ReleephUserView.php',
-    'SleepBuildStepImplementation' => 'applications/harbormaster/step/SleepBuildStepImplementation.php',
     'SlowvoteEmbedView' => 'applications/slowvote/view/SlowvoteEmbedView.php',
     'SlowvoteRemarkupRule' => 'applications/slowvote/remarkup/SlowvoteRemarkupRule.php',
   ),
@@ -2320,6 +2320,8 @@
       0 => 'Phobject',
       1 => 'PhabricatorPolicyInterface',
     ),
+    'ConduitAPI_agent_Method' => 'ConduitAPIMethod',
+    'ConduitAPI_agent_nextbuild_Method' => 'ConduitAPI_agent_Method',
     'ConduitAPI_arcanist_Method' => 'ConduitAPIMethod',
     'ConduitAPI_arcanist_projectinfo_Method' => 'ConduitAPI_arcanist_Method',
     'ConduitAPI_audit_Method' => 'ConduitAPIMethod',
@@ -4663,7 +4665,6 @@
     'ReleephStatusFieldSpecification' => 'ReleephFieldSpecification',
     'ReleephSummaryFieldSpecification' => 'ReleephFieldSpecification',
     'ReleephUserView' => 'AphrontView',
-    'SleepBuildStepImplementation' => 'BuildStepImplementation',
     'SlowvoteEmbedView' => 'AphrontView',
     'SlowvoteRemarkupRule' => 'PhabricatorRemarkupRuleObject',
   ),
Index: src/applications/harbormaster/conduit/ConduitAPI_agent_Method.php
===================================================================
--- /dev/null
+++ src/applications/harbormaster/conduit/ConduitAPI_agent_Method.php
@@ -0,0 +1,13 @@
+<?php
+
+/**
+ * @group conduit
+ */
+abstract class ConduitAPI_agent_Method extends ConduitAPIMethod {
+
+  public function getApplication() {
+    return PhabricatorApplication::getByClass(
+      'PhabricatorApplicationHarbormaster');
+  }
+
+}
Index: src/applications/harbormaster/conduit/ConduitAPI_agent_nextbuild_Method.php
===================================================================
--- /dev/null
+++ src/applications/harbormaster/conduit/ConduitAPI_agent_nextbuild_Method.php
@@ -0,0 +1,37 @@
+<?php
+
+/**
+ * @group conduit
+ */
+final class ConduitAPI_agent_nextbuild_Method
+  extends ConduitAPI_agent_Method {
+
+  public function getMethodDescription() {
+    return "Retrieve the next build an agent should pick up.";
+  }
+
+  public function getMethodStatus() {
+    return self::METHOD_STATUS_UNSTABLE;
+  }
+
+  public function defineParamTypes() {
+    return array(
+      'category'      => 'optional string',
+    );
+  }
+
+  public function defineReturnType() {
+    return 'list<dict>';
+  }
+
+  public function defineErrorTypes() {
+    return array(
+    );
+  }
+
+  protected function execute(ConduitAPIRequest $request) {
+    return array(
+      "exists" => false,
+      "steps" => array());
+  }
+}
Index: src/applications/harbormaster/controller/HarbormasterStepAddController.php
===================================================================
--- src/applications/harbormaster/controller/HarbormasterStepAddController.php
+++ src/applications/harbormaster/controller/HarbormasterStepAddController.php
@@ -9,6 +9,9 @@
     $this->id = $data['id'];
   }
 
+  /**
+   * @phutil-external-symbol class BuildStepImplementation
+   */
   public function processRequest() {
     $request = $this->getRequest();
     $viewer = $request->getUser();
Index: src/applications/harbormaster/controller/HarbormasterStepEditController.php
===================================================================
--- src/applications/harbormaster/controller/HarbormasterStepEditController.php
+++ src/applications/harbormaster/controller/HarbormasterStepEditController.php
@@ -9,6 +9,9 @@
     $this->id = idx($data, 'id');
   }
 
+  /**
+   * @phutil-external-symbol class BuildStepImplementation
+   */
   public function processRequest() {
     $request = $this->getRequest();
     $viewer = $request->getUser();
Index: src/applications/harbormaster/step/BuildStepImplementation.php
===================================================================
--- src/applications/harbormaster/step/BuildStepImplementation.php
+++ /dev/null
@@ -1,88 +0,0 @@
-<?php
-
-abstract class BuildStepImplementation {
-
-  private $settings;
-
-  const SETTING_TYPE_STRING = 'string';
-  const SETTING_TYPE_INTEGER = 'integer';
-  const SETTING_TYPE_BOOLEAN = 'boolean';
-
-  public static function getImplementations() {
-    $symbols = id(new PhutilSymbolLoader())
-      ->setAncestorClass("BuildStepImplementation")
-      ->setConcreteOnly(true)
-      ->selectAndLoadSymbols();
-    return ipull($symbols, 'name');
-  }
-
-  /**
-   * The name of the implementation.
-   */
-  abstract public function getName();
-
-  /**
-   * The generic description of the implementation.
-   */
-  public function getGenericDescription() {
-    return '';
-  }
-
-  /**
-   * The description of the implementation, based on the current settings.
-   */
-  public function getDescription() {
-    return '';
-  }
-
-  /**
-   * Run the build step against the specified build.
-   */
-  abstract public function execute(HarbormasterBuild $build);
-
-  /**
-   * Gets the settings for this build step.
-   */
-  public function getSettings() {
-    return $this->settings;
-  }
-
-  /**
-   * Validate the current settings of this build step.
-   */
-  public function validate() {
-    return true;
-  }
-
-  /**
-   * Loads the settings for this build step implementation from the build step.
-   */
-  public final function loadSettings(HarbormasterBuildStep $build_step) {
-    $this->settings = array();
-    $this->validateSettingDefinitions();
-    foreach ($this->getSettingDefinitions() as $name => $opt) {
-      $this->settings[$name] = $build_step->getDetail($name);
-    }
-    return $this->settings;
-  }
-
-  /**
-   * Validates that the setting definitions for this implementation are valid.
-   */
-  public final function validateSettingDefinitions() {
-    foreach ($this->getSettingDefinitions() as $name => $opt) {
-      if (!isset($opt['type'])) {
-        throw new Exception(
-          'Setting definition \''.$name.
-          '\' is missing type requirement.');
-      }
-    }
-  }
-
-  /**
-   * Return an array of settings for this step implementation.
-   */
-  public function getSettingDefinitions() {
-    return array();
-  }
-}
Index: src/applications/harbormaster/step/SleepBuildStepImplementation.php
===================================================================
--- src/applications/harbormaster/step/SleepBuildStepImplementation.php
+++ /dev/null
@@ -1,45 +0,0 @@
-<?php
-
-final class SleepBuildStepImplementation extends BuildStepImplementation {
-
-  public function getName() {
-    return pht('Sleep');
-  }
-
-  public function getGenericDescription() {
-    return pht('Sleep for a specified number of seconds.');
-  }
-
-  public function getDescription() {
-    $settings = $this->getSettings();
-
-    return pht('Sleep for %s seconds.', $settings['seconds']);
-  }
-
-  public function execute(HarbormasterBuild $build) {
-    $settings = $this->getSettings();
-
-    sleep($settings['seconds']);
-  }
-
-  public function validateSettings() {
-    $settings = $this->getSettings();
-
-    if ($settings['seconds'] === null) {
-      return false;
-    }
-    if (!is_int($settings['seconds'])) {
-      return false;
-    }
-    return true;
-  }
-
-  public function getSettingDefinitions() {
-    return array(
-      'seconds' => array(
-        'name' => 'Seconds',
-        'description' => 'The number of seconds to sleep for.',
-        'type' => BuildStepImplementation::SETTING_TYPE_INTEGER));
-  }
-
-}
Index: src/applications/harbormaster/storage/build/HarbormasterBuild.php
===================================================================
--- src/applications/harbormaster/storage/build/HarbormasterBuild.php
+++ src/applications/harbormaster/storage/build/HarbormasterBuild.php
@@ -50,6 +50,15 @@
       ->setBuildStatus(self::STATUS_INACTIVE);
   }
 
+  /**
+   * Create a remote representation of this build.
+   *
+   * @phutil-external-symbol class RemoteHarbormasterBuild
+   */
+  public function createRemoteBuild() {
+    return new RemoteHarbormasterBuild();
+  }
+
   public function getConfiguration() {
     return array(
       self::CONFIG_AUX_PHID => true,
Index: src/applications/harbormaster/storage/configuration/HarbormasterBuildStep.php
===================================================================
--- src/applications/harbormaster/storage/configuration/HarbormasterBuildStep.php
+++ src/applications/harbormaster/storage/configuration/HarbormasterBuildStep.php
@@ -41,6 +41,9 @@
     return $this;
   }
 
+  /**
+   * @phutil-external-symbol class BuildStepImplementation
+   */
   public function getStepImplementation() {
     if ($this->className === null) {
       throw new Exception("No implementation set for the given step.");
Index: src/applications/harbormaster/worker/HarbormasterBuildWorker.php
===================================================================
--- src/applications/harbormaster/worker/HarbormasterBuildWorker.php
+++ src/applications/harbormaster/worker/HarbormasterBuildWorker.php
@@ -44,7 +44,7 @@
           $build->setBuildStatus(HarbormasterBuild::STATUS_ERROR);
           break;
         }
-        $implementation->execute($build);
+        $implementation->execute($build->createRemoteBuild());
         if ($build->getBuildStatus() !== HarbormasterBuild::STATUS_BUILDING) {
           break;
         }