diff --git a/resources/celerity/map.php b/resources/celerity/map.php
index 2dd5cf0966..b1a97639c2 100644
--- a/resources/celerity/map.php
+++ b/resources/celerity/map.php
@@ -9,7 +9,7 @@ return array(
   'names' => array(
     'conpherence.pkg.css' => '3c8a0668',
     'conpherence.pkg.js' => '020aebcf',
-    'core.pkg.css' => 'e0f5d66f',
+    'core.pkg.css' => '4ed8ce1f',
     'core.pkg.js' => '5c737607',
     'differential.pkg.css' => 'b8df73d4',
     'differential.pkg.js' => '67c9ea4c',
@@ -164,7 +164,7 @@ return array(
     'rsrc/css/phui/phui-left-right.css' => '68513c34',
     'rsrc/css/phui/phui-lightbox.css' => '4ebf22da',
     'rsrc/css/phui/phui-list.css' => '470b1adb',
-    'rsrc/css/phui/phui-object-box.css' => '9b58483d',
+    'rsrc/css/phui/phui-object-box.css' => 'f434b6be',
     'rsrc/css/phui/phui-pager.css' => 'd022c7ad',
     'rsrc/css/phui/phui-pinboard-view.css' => '1f08f5d8',
     'rsrc/css/phui/phui-property-list-view.css' => 'cad62236',
@@ -833,7 +833,7 @@ return array(
     'phui-left-right-css' => '68513c34',
     'phui-lightbox-css' => '4ebf22da',
     'phui-list-view-css' => '470b1adb',
-    'phui-object-box-css' => '9b58483d',
+    'phui-object-box-css' => 'f434b6be',
     'phui-oi-big-ui-css' => '9e037c7a',
     'phui-oi-color-css' => 'b517bfa0',
     'phui-oi-drag-ui-css' => 'da15d3dc',
diff --git a/src/__phutil_library_map__.php b/src/__phutil_library_map__.php
index e3287df74c..b10c0e109f 100644
--- a/src/__phutil_library_map__.php
+++ b/src/__phutil_library_map__.php
@@ -2272,6 +2272,7 @@ phutil_register_library_map(array(
     'PhabricatorAuthInviteVerifyException' => 'applications/auth/exception/PhabricatorAuthInviteVerifyException.php',
     'PhabricatorAuthInviteWorker' => 'applications/auth/worker/PhabricatorAuthInviteWorker.php',
     'PhabricatorAuthLinkController' => 'applications/auth/controller/PhabricatorAuthLinkController.php',
+    'PhabricatorAuthLinkMessageType' => 'applications/auth/message/PhabricatorAuthLinkMessageType.php',
     'PhabricatorAuthListController' => 'applications/auth/controller/config/PhabricatorAuthListController.php',
     'PhabricatorAuthLoginController' => 'applications/auth/controller/PhabricatorAuthLoginController.php',
     'PhabricatorAuthLoginMessageType' => 'applications/auth/message/PhabricatorAuthLoginMessageType.php',
@@ -2370,6 +2371,7 @@ phutil_register_library_map(array(
     'PhabricatorAuthSessionPHIDType' => 'applications/auth/phid/PhabricatorAuthSessionPHIDType.php',
     'PhabricatorAuthSessionQuery' => 'applications/auth/query/PhabricatorAuthSessionQuery.php',
     'PhabricatorAuthSessionRevoker' => 'applications/auth/revoker/PhabricatorAuthSessionRevoker.php',
+    'PhabricatorAuthSetExternalController' => 'applications/auth/controller/PhabricatorAuthSetExternalController.php',
     'PhabricatorAuthSetPasswordController' => 'applications/auth/controller/PhabricatorAuthSetPasswordController.php',
     'PhabricatorAuthSetupCheck' => 'applications/config/check/PhabricatorAuthSetupCheck.php',
     'PhabricatorAuthStartController' => 'applications/auth/controller/PhabricatorAuthStartController.php',
@@ -8023,6 +8025,7 @@ phutil_register_library_map(array(
     'PhabricatorAuthInviteVerifyException' => 'PhabricatorAuthInviteDialogException',
     'PhabricatorAuthInviteWorker' => 'PhabricatorWorker',
     'PhabricatorAuthLinkController' => 'PhabricatorAuthController',
+    'PhabricatorAuthLinkMessageType' => 'PhabricatorAuthMessageType',
     'PhabricatorAuthListController' => 'PhabricatorAuthProviderConfigController',
     'PhabricatorAuthLoginController' => 'PhabricatorAuthController',
     'PhabricatorAuthLoginMessageType' => 'PhabricatorAuthMessageType',
@@ -8142,6 +8145,7 @@ phutil_register_library_map(array(
     'PhabricatorAuthSessionPHIDType' => 'PhabricatorPHIDType',
     'PhabricatorAuthSessionQuery' => 'PhabricatorCursorPagedPolicyAwareQuery',
     'PhabricatorAuthSessionRevoker' => 'PhabricatorAuthRevoker',
+    'PhabricatorAuthSetExternalController' => 'PhabricatorAuthController',
     'PhabricatorAuthSetPasswordController' => 'PhabricatorAuthController',
     'PhabricatorAuthSetupCheck' => 'PhabricatorSetupCheck',
     'PhabricatorAuthStartController' => 'PhabricatorAuthController',
diff --git a/src/applications/auth/application/PhabricatorAuthApplication.php b/src/applications/auth/application/PhabricatorAuthApplication.php
index 4e0baff229..3446ad597d 100644
--- a/src/applications/auth/application/PhabricatorAuthApplication.php
+++ b/src/applications/auth/application/PhabricatorAuthApplication.php
@@ -86,7 +86,9 @@ final class PhabricatorAuthApplication extends PhabricatorApplication {
             => 'PhabricatorAuthSSHKeyRevokeController',
           'view/(?P<id>\d+)/' => 'PhabricatorAuthSSHKeyViewController',
         ),
+
         'password/' => 'PhabricatorAuthSetPasswordController',
+        'external/' => 'PhabricatorAuthSetExternalController',
 
         'mfa/' => array(
           $this->getQueryRoutePattern() =>
diff --git a/src/applications/auth/controller/PhabricatorAuthOneTimeLoginController.php b/src/applications/auth/controller/PhabricatorAuthOneTimeLoginController.php
index 353f31562c..d176a67119 100644
--- a/src/applications/auth/controller/PhabricatorAuthOneTimeLoginController.php
+++ b/src/applications/auth/controller/PhabricatorAuthOneTimeLoginController.php
@@ -225,17 +225,45 @@ final class PhabricatorAuthOneTimeLoginController
       return (string)new PhutilURI($panel_uri, $params);
     }
 
-    $providers = id(new PhabricatorAuthProviderConfigQuery())
+    // Check if the user already has external accounts linked. If they do,
+    // it's not obvious why they aren't using them to log in, but assume they
+    // know what they're doing. We won't send them to the link workflow.
+    $accounts = id(new PhabricatorExternalAccountQuery())
+      ->setViewer($user)
+      ->withUserPHIDs(array($user->getPHID()))
+      ->execute();
+
+    $configs = id(new PhabricatorAuthProviderConfigQuery())
       ->setViewer($user)
       ->withIsEnabled(true)
       ->execute();
 
+    $linkable = array();
+    foreach ($configs as $config) {
+      if (!$config->getShouldAllowLink()) {
+        continue;
+      }
+
+      $provider = $config->getProvider();
+      if (!$provider->isLoginFormAButton()) {
+        continue;
+      }
+
+      $linkable[] = $provider;
+    }
+
+    // If there's at least one linkable provider, and the user doesn't already
+    // have accounts, send the user to the link workflow.
+    if (!$accounts && $linkable) {
+      return '/auth/external/';
+    }
+
     // If there are no configured providers and the user is an administrator,
     // send them to Auth to configure a provider. This is probably where they
     // want to go. You can end up in this state by accidentally losing your
     // first session during initial setup, or after restoring exported data
     // from a hosted instance.
-    if (!$providers && $user->getIsAdmin()) {
+    if (!$configs && $user->getIsAdmin()) {
       return '/auth/';
     }
 
diff --git a/src/applications/auth/controller/PhabricatorAuthSetExternalController.php b/src/applications/auth/controller/PhabricatorAuthSetExternalController.php
new file mode 100644
index 0000000000..51dfcab53f
--- /dev/null
+++ b/src/applications/auth/controller/PhabricatorAuthSetExternalController.php
@@ -0,0 +1,110 @@
+<?php
+
+final class PhabricatorAuthSetExternalController
+  extends PhabricatorAuthController {
+
+  public function handleRequest(AphrontRequest $request) {
+    $viewer = $this->getViewer();
+
+    $configs = id(new PhabricatorAuthProviderConfigQuery())
+      ->setViewer($viewer)
+      ->withIsEnabled(true)
+      ->execute();
+
+    $linkable = array();
+    foreach ($configs as $config) {
+      if (!$config->getShouldAllowLink()) {
+        continue;
+      }
+
+      // For now, only buttons get to appear here: for example, we can't
+      // reasonably embed an entire LDAP form into this UI.
+      $provider = $config->getProvider();
+      if (!$provider->isLoginFormAButton()) {
+        continue;
+      }
+
+      $linkable[] = $config;
+    }
+
+    if (!$linkable) {
+      return $this->newDialog()
+        ->setTitle(pht('No Linkable External Providers'))
+        ->appendParagraph(
+          pht(
+            'Currently, there are no configured external auth providers '.
+            'which you can link your account to.'))
+        ->addCancelButton('/');
+    }
+
+    $text = PhabricatorAuthMessage::loadMessageText(
+      $viewer,
+      PhabricatorAuthLinkMessageType::MESSAGEKEY);
+    if (!strlen($text)) {
+      $text = pht(
+        'You can link your Phabricator account to an external account to '.
+        'allow you to log in more easily in the future. To continue, choose '.
+        'an account to link below. If you prefer not to link your account, '.
+        'you can skip this step.');
+    }
+
+    $remarkup_view = new PHUIRemarkupView($viewer, $text);
+    $remarkup_view = phutil_tag(
+      'div',
+      array(
+        'class' => 'phui-object-box-instructions',
+      ),
+      $remarkup_view);
+
+    PhabricatorCookies::setClientIDCookie($request);
+
+    $view = array();
+    foreach ($configs as $config) {
+      $provider = $config->getProvider();
+
+      $form = $provider->buildLinkForm($this);
+
+      if ($provider->isLoginFormAButton()) {
+        require_celerity_resource('auth-css');
+        $form = phutil_tag(
+          'div',
+          array(
+            'class' => 'phabricator-link-button pl',
+          ),
+          $form);
+      }
+
+      $view[] = $form;
+    }
+
+    $form = id(new AphrontFormView())
+      ->setViewer($viewer)
+      ->appendControl(
+        id(new AphrontFormSubmitControl())
+          ->addCancelButton('/', pht('Skip This Step')));
+
+    $header = id(new PHUIHeaderView())
+      ->setHeader(pht('Link External Account'));
+
+    $box = id(new PHUIObjectBoxView())
+      ->setViewer($viewer)
+      ->setHeader($header)
+      ->setBackground(PHUIObjectBoxView::BLUE_PROPERTY)
+      ->appendChild($remarkup_view)
+      ->appendChild($view)
+      ->appendChild($form);
+
+    $main_view = id(new PHUITwoColumnView())
+      ->setFooter($box);
+
+    $crumbs = $this->buildApplicationCrumbs()
+      ->addTextCrumb(pht('Link External Account'))
+      ->setBorder(true);
+
+    return $this->newPage()
+      ->setTitle(pht('Link External Account'))
+      ->setCrumbs($crumbs)
+      ->appendChild($main_view);
+  }
+
+}
diff --git a/src/applications/auth/message/PhabricatorAuthLinkMessageType.php b/src/applications/auth/message/PhabricatorAuthLinkMessageType.php
new file mode 100644
index 0000000000..17991231c1
--- /dev/null
+++ b/src/applications/auth/message/PhabricatorAuthLinkMessageType.php
@@ -0,0 +1,18 @@
+<?php
+
+final class PhabricatorAuthLinkMessageType
+  extends PhabricatorAuthMessageType {
+
+  const MESSAGEKEY = 'auth.link';
+
+  public function getDisplayName() {
+    return pht('Unlinked Account Instructions');
+  }
+
+  public function getShortDescription() {
+    return pht(
+      'Guidance shown after a user logs in with an email link and is '.
+      'prompted to link an external account.');
+  }
+
+}
diff --git a/src/applications/auth/provider/PhabricatorAuthProvider.php b/src/applications/auth/provider/PhabricatorAuthProvider.php
index dfdc7c6a5b..eaf52552ef 100644
--- a/src/applications/auth/provider/PhabricatorAuthProvider.php
+++ b/src/applications/auth/provider/PhabricatorAuthProvider.php
@@ -161,7 +161,7 @@ abstract class PhabricatorAuthProvider extends Phobject {
   abstract public function processLoginRequest(
     PhabricatorAuthLoginController $controller);
 
-  public function buildLinkForm(PhabricatorAuthLinkController $controller) {
+  public function buildLinkForm($controller) {
     return $this->renderLoginForm($controller->getRequest(), $mode = 'link');
   }
 
diff --git a/src/applications/auth/provider/PhabricatorPasswordAuthProvider.php b/src/applications/auth/provider/PhabricatorPasswordAuthProvider.php
index 146e41706a..d39e378798 100644
--- a/src/applications/auth/provider/PhabricatorPasswordAuthProvider.php
+++ b/src/applications/auth/provider/PhabricatorPasswordAuthProvider.php
@@ -159,8 +159,7 @@ final class PhabricatorPasswordAuthProvider extends PhabricatorAuthProvider {
     return $dialog;
   }
 
-  public function buildLinkForm(
-    PhabricatorAuthLinkController $controller) {
+  public function buildLinkForm($controller) {
     throw new Exception(pht("Password providers can't be linked."));
   }
 
diff --git a/webroot/rsrc/css/phui/phui-object-box.css b/webroot/rsrc/css/phui/phui-object-box.css
index 4999a4c2c2..f95e36eedc 100644
--- a/webroot/rsrc/css/phui/phui-object-box.css
+++ b/webroot/rsrc/css/phui/phui-object-box.css
@@ -158,3 +158,8 @@ div.phui-object-box.phui-object-box-flush {
   margin-top: 8px;
   margin-bottom: 8px;
 }
+
+.phui-object-box-instructions {
+  padding: 16px;
+  border-bottom: 1px solid {$thinblueborder};
+}