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
@@ -1943,6 +1943,7 @@
     'PhabricatorAuthSessionEngineExtension' => 'applications/auth/engine/PhabricatorAuthSessionEngineExtension.php',
     'PhabricatorAuthSessionEngineExtensionModule' => 'applications/auth/engine/PhabricatorAuthSessionEngineExtensionModule.php',
     'PhabricatorAuthSessionGarbageCollector' => 'applications/auth/garbagecollector/PhabricatorAuthSessionGarbageCollector.php',
+    'PhabricatorAuthSessionInfo' => 'applications/auth/data/PhabricatorAuthSessionInfo.php',
     'PhabricatorAuthSessionQuery' => 'applications/auth/query/PhabricatorAuthSessionQuery.php',
     'PhabricatorAuthSetupCheck' => 'applications/config/check/PhabricatorAuthSetupCheck.php',
     'PhabricatorAuthStartController' => 'applications/auth/controller/PhabricatorAuthStartController.php',
@@ -6776,6 +6777,7 @@
     'PhabricatorAuthSessionEngineExtension' => 'Phobject',
     'PhabricatorAuthSessionEngineExtensionModule' => 'PhabricatorConfigModule',
     'PhabricatorAuthSessionGarbageCollector' => 'PhabricatorGarbageCollector',
+    'PhabricatorAuthSessionInfo' => 'Phobject',
     'PhabricatorAuthSessionQuery' => 'PhabricatorCursorPagedPolicyAwareQuery',
     'PhabricatorAuthSetupCheck' => 'PhabricatorSetupCheck',
     'PhabricatorAuthStartController' => 'PhabricatorAuthController',
diff --git a/src/applications/auth/data/PhabricatorAuthSessionInfo.php b/src/applications/auth/data/PhabricatorAuthSessionInfo.php
new file mode 100644
--- /dev/null
+++ b/src/applications/auth/data/PhabricatorAuthSessionInfo.php
@@ -0,0 +1,36 @@
+<?php
+
+final class PhabricatorAuthSessionInfo extends Phobject {
+
+  private $sessionType;
+  private $identityPHID;
+  private $isPartial;
+
+  public function setSessionType($session_type) {
+    $this->sessionType = $session_type;
+    return $this;
+  }
+
+  public function getSessionType() {
+    return $this->sessionType;
+  }
+
+  public function setIdentityPHID($identity_phid) {
+    $this->identityPHID = $identity_phid;
+    return $this;
+  }
+
+  public function getIdentityPHID() {
+    return $this->identityPHID;
+  }
+
+  public function setIsPartial($is_partial) {
+    $this->isPartial = $is_partial;
+    return $this;
+  }
+
+  public function getIsPartial() {
+    return $this->isPartial;
+  }
+
+}
diff --git a/src/applications/auth/engine/PhabricatorAuthSessionEngine.php b/src/applications/auth/engine/PhabricatorAuthSessionEngine.php
--- a/src/applications/auth/engine/PhabricatorAuthSessionEngine.php
+++ b/src/applications/auth/engine/PhabricatorAuthSessionEngine.php
@@ -270,6 +270,16 @@
       $log->save();
     unset($unguarded);
 
+    $info = id(new PhabricatorAuthSessionInfo())
+      ->setSessionType($session_type)
+      ->setIdentityPHID($identity_phid)
+      ->setIsPartial($partial);
+
+    $extensions = PhabricatorAuthSessionEngineExtension::getAllExtensions();
+    foreach ($extensions as $extension) {
+      $extension->didEstablishSession($info);
+    }
+
     return $session_key;
   }
 
@@ -837,6 +847,11 @@
 
     // Switch to the user's translation.
     PhabricatorEnv::setLocaleCode($user->getTranslation());
+
+    $extensions = PhabricatorAuthSessionEngineExtension::getAllExtensions();
+    foreach ($extensions as $extension) {
+      $extension->willServeRequestForUser($user);
+    }
   }
 
 }
diff --git a/src/applications/auth/engine/PhabricatorAuthSessionEngineExtension.php b/src/applications/auth/engine/PhabricatorAuthSessionEngineExtension.php
--- a/src/applications/auth/engine/PhabricatorAuthSessionEngineExtension.php
+++ b/src/applications/auth/engine/PhabricatorAuthSessionEngineExtension.php
@@ -16,6 +16,14 @@
 
   abstract public function getExtensionName();
 
+  public function didEstablishSession(PhabricatorAuthSessionInfo $info) {
+    return;
+  }
+
+  public function willServeRequestForUser(PhabricatorUser $user) {
+    return;
+  }
+
   public function didLogout(PhabricatorUser $user, array $sessions) {
     return;
   }