diff --git a/_build/data/transport.core.context_settings.php b/_build/data/transport.core.context_settings.php
index b9a3227b9f7..48de8059f29 100644
--- a/_build/data/transport.core.context_settings.php
+++ b/_build/data/transport.core.context_settings.php
@@ -1,4 +1,5 @@
 <?php
+
 use MODX\Revolution\modContextSetting;
 
 $collection['0']= $xpdo->newObject(modContextSetting::class);
@@ -21,3 +22,13 @@
   'area' => 'system',
   'editedon' => NULL,
 ], '', true, true);
+$collection['2'] = $xpdo->newObject(modContextSetting::class);
+$collection['2']->fromArray([
+  'context_key' => 'mgr',
+  'key' => 'anonymous_sessions',
+  'value' => true,
+  'xtype' => 'combo-boolean',
+  'namespace' => 'core',
+  'area' => 'session',
+  'editedon' => null,
+], '', true, true);
diff --git a/_build/test/Tests/Model/Security/AnonymousSessionsContextTest.php b/_build/test/Tests/Model/Security/AnonymousSessionsContextTest.php
new file mode 100644
index 00000000000..bc991007e94
--- /dev/null
+++ b/_build/test/Tests/Model/Security/AnonymousSessionsContextTest.php
@@ -0,0 +1,236 @@
+<?php
+
+/*
+ * This file is part of the MODX Revolution package.
+ *
+ * Copyright (c) MODX, LLC
+ *
+ * For complete copyright and license information, see the COPYRIGHT and LICENSE
+ * files found in the top-level directory of this distribution.
+ *
+ * @package modx-test
+ */
+
+namespace MODX\Revolution\Tests\Model\Security;
+
+use MODX\Revolution\modContext;
+use MODX\Revolution\modContextSetting;
+use MODX\Revolution\MODxTestCase;
+
+/**
+ * Regression for #16424: mgr must keep anonymous_sessions enabled even when
+ * the system setting is disabled, so manager login can start a session without
+ * an existing cookie.
+ *
+ * @package modx-test
+ * @subpackage modx
+ * @group Model
+ * @group modX
+ * @group Session
+ */
+class AnonymousSessionsContextTest extends MODxTestCase
+{
+    /** @var mixed */
+    private $originalSystemAnonymousSessions;
+
+    /** @var mixed */
+    private $originalMgrAnonymousSessions;
+
+    /** @var bool */
+    private $createdMgrSetting = false;
+
+    /** @var bool */
+    private $createdWebSetting = false;
+
+    /**
+     * @before
+     */
+    public function setUpFixtures()
+    {
+        parent::setUpFixtures();
+
+        $this->originalSystemAnonymousSessions = $this->modx->getOption('anonymous_sessions');
+        $this->modx->setOption('anonymous_sessions', false);
+        $this->modx->_systemConfig['anonymous_sessions'] = false;
+
+        $mgrSetting = $this->modx->getObject(modContextSetting::class, [
+            'context_key' => modContext::CONTEXT_MANAGER,
+            'key' => 'anonymous_sessions',
+        ]);
+        if (!$mgrSetting) {
+            $mgrSetting = $this->modx->newObject(modContextSetting::class);
+            $mgrSetting->fromArray([
+                'context_key' => modContext::CONTEXT_MANAGER,
+                'key' => 'anonymous_sessions',
+                'value' => true,
+                'xtype' => 'combo-boolean',
+                'namespace' => 'core',
+                'area' => 'session',
+            ], '', true, true);
+            $this->assertTrue((bool)$mgrSetting->save(), 'Could not create mgr anonymous_sessions fixture.');
+            $this->createdMgrSetting = true;
+            $this->originalMgrAnonymousSessions = null;
+        } else {
+            $this->originalMgrAnonymousSessions = $mgrSetting->get('value');
+            $mgrSetting->set('value', true);
+            $this->assertTrue((bool)$mgrSetting->save(), 'Could not enable mgr anonymous_sessions fixture.');
+        }
+
+        $webSetting = $this->modx->getObject(modContextSetting::class, [
+            'context_key' => modContext::CONTEXT_DEFAULT,
+            'key' => 'anonymous_sessions',
+        ]);
+        if ($webSetting) {
+            $webSetting->remove();
+        }
+        $webSetting = $this->modx->newObject(modContextSetting::class);
+        $webSetting->fromArray([
+            'context_key' => modContext::CONTEXT_DEFAULT,
+            'key' => 'anonymous_sessions',
+            'value' => false,
+            'xtype' => 'combo-boolean',
+            'namespace' => 'core',
+            'area' => 'session',
+        ], '', true, true);
+        $this->assertTrue((bool)$webSetting->save(), 'Could not create web anonymous_sessions fixture.');
+        $this->createdWebSetting = true;
+
+        $this->refreshContextSettings();
+    }
+
+    /**
+     * @after
+     */
+    public function tearDownFixtures()
+    {
+        if ($this->createdMgrSetting) {
+            $mgrSetting = $this->modx->getObject(modContextSetting::class, [
+                'context_key' => modContext::CONTEXT_MANAGER,
+                'key' => 'anonymous_sessions',
+            ]);
+            if ($mgrSetting) {
+                $mgrSetting->remove();
+            }
+        } elseif ($this->originalMgrAnonymousSessions !== null) {
+            $mgrSetting = $this->modx->getObject(modContextSetting::class, [
+                'context_key' => modContext::CONTEXT_MANAGER,
+                'key' => 'anonymous_sessions',
+            ]);
+            if ($mgrSetting) {
+                $mgrSetting->set('value', $this->originalMgrAnonymousSessions);
+                $mgrSetting->save();
+            }
+        }
+
+        if ($this->createdWebSetting) {
+            $webSetting = $this->modx->getObject(modContextSetting::class, [
+                'context_key' => modContext::CONTEXT_DEFAULT,
+                'key' => 'anonymous_sessions',
+            ]);
+            if ($webSetting) {
+                $webSetting->remove();
+            }
+        }
+
+        $this->modx->setOption('anonymous_sessions', $this->originalSystemAnonymousSessions);
+        $this->modx->_systemConfig['anonymous_sessions'] = $this->originalSystemAnonymousSessions;
+        $this->refreshContextSettings();
+        $this->modx->reloadContext(modContext::CONTEXT_DEFAULT);
+
+        parent::tearDownFixtures();
+    }
+
+    public function testManagerContextOverridesSystemAnonymousSessionsFalse()
+    {
+        $this->assertTrue(
+            $this->activateContext(modContext::CONTEXT_MANAGER),
+            'Could not activate mgr context.'
+        );
+        $this->assertTrue(
+            $this->modx->paramValueIsTrue(
+                ['anonymous_sessions' => $this->modx->getOption('anonymous_sessions')],
+                'anonymous_sessions'
+            ),
+            'mgr must enable anonymous_sessions so login can start a session without a cookie.'
+        );
+    }
+
+    public function testWebContextCanDisableAnonymousSessions()
+    {
+        $this->assertTrue(
+            $this->activateContext(modContext::CONTEXT_MANAGER),
+            'Could not activate mgr context before returning to web.'
+        );
+        $this->assertTrue(
+            $this->activateContext(modContext::CONTEXT_DEFAULT),
+            'Could not activate web context.'
+        );
+        $this->assertFalse(
+            $this->modx->paramValueIsTrue(
+                ['anonymous_sessions' => $this->modx->getOption('anonymous_sessions')],
+                'anonymous_sessions'
+            ),
+            'web context should be able to disable anonymous_sessions independently of mgr.'
+        );
+    }
+
+    public function testUpgradeScriptEnsuresManagerAnonymousSessions()
+    {
+        $mgrSetting = $this->modx->getObject(modContextSetting::class, [
+            'context_key' => modContext::CONTEXT_MANAGER,
+            'key' => 'anonymous_sessions',
+        ]);
+        if ($mgrSetting) {
+            $mgrSetting->remove();
+        }
+        $this->refreshContextSettings();
+
+        $modx = $this->modx;
+        $upgradeScript = dirname(__DIR__, 5) . '/setup/includes/upgrades/common/3.3.0-mgr-anonymous-sessions.php';
+        include $upgradeScript;
+
+        $mgrSetting = $this->modx->getObject(modContextSetting::class, [
+            'context_key' => modContext::CONTEXT_MANAGER,
+            'key' => 'anonymous_sessions',
+        ]);
+        $this->assertInstanceOf(modContextSetting::class, $mgrSetting);
+        $this->assertTrue(
+            $this->modx->paramValueIsTrue(['value' => $mgrSetting->get('value')], 'value'),
+            'Upgrade must create mgr anonymous_sessions=Yes.'
+        );
+
+        $mgrSetting->set('value', false);
+        $this->assertTrue((bool)$mgrSetting->save());
+
+        include $upgradeScript;
+
+        $mgrSetting = $this->modx->getObject(modContextSetting::class, [
+            'context_key' => modContext::CONTEXT_MANAGER,
+            'key' => 'anonymous_sessions',
+        ]);
+        $this->assertTrue(
+            $this->modx->paramValueIsTrue(['value' => $mgrSetting->get('value')], 'value'),
+            'Upgrade must restore mgr anonymous_sessions=Yes if it was disabled.'
+        );
+        $this->createdMgrSetting = true;
+    }
+
+    private function activateContext(string $contextKey): bool
+    {
+        if ($this->modx->context instanceof modContext && $this->modx->context->get('key') === $contextKey) {
+            return (bool)$this->modx->reloadContext($contextKey);
+        }
+
+        return (bool)$this->modx->switchContext($contextKey, true);
+    }
+
+    private function refreshContextSettings(): void
+    {
+        $this->modx->cacheManager->refresh([
+            'context_settings' => [
+                'contexts' => [modContext::CONTEXT_MANAGER, modContext::CONTEXT_DEFAULT],
+            ],
+        ]);
+        unset($this->modx->contexts[modContext::CONTEXT_MANAGER], $this->modx->contexts[modContext::CONTEXT_DEFAULT]);
+    }
+}
diff --git a/core/lexicon/en/setting.inc.php b/core/lexicon/en/setting.inc.php
index b98e375f93d..8c9b766f87e 100644
--- a/core/lexicon/en/setting.inc.php
+++ b/core/lexicon/en/setting.inc.php
@@ -98,7 +98,7 @@
 $_lang['setting_allow_tv_eval_desc'] = 'Select this option to enable or disable eval in TV bindings. If this option is set to no, the code/value will just be handled as regular text.';
 
 $_lang['setting_anonymous_sessions'] = 'Anonymous Sessions';
-$_lang['setting_anonymous_sessions_desc'] = 'If disabled, only authenticated users will have access to a PHP session. This can reduce overhead for anonymous users and the load they impose on a MODX site if they do not need access to a unique session. If session_enabled is false, this setting has no effect as sessions would never be available.';
+$_lang['setting_anonymous_sessions_desc'] = 'When authentication or other persistence features that require a PHP Session are not needed, set this to “No.” The Manager (mgr) Context must set this to “Yes” to operate correctly. Note that in multi-Context setups, the system-wide value for this setting can be overridden at the Context level.';
 
 $_lang['setting_archive_with'] = 'Force PCLZip Archives';
 $_lang['setting_archive_with_desc'] = 'If true, will use PCLZip instead of ZipArchive as the zip extension. Turn this on if you are getting extractTo errors or are having problems with unzipping in Package Management.';
diff --git a/setup/includes/upgrades/common/3.3.0-mgr-anonymous-sessions.php b/setup/includes/upgrades/common/3.3.0-mgr-anonymous-sessions.php
new file mode 100644
index 00000000000..7d3a6118d40
--- /dev/null
+++ b/setup/includes/upgrades/common/3.3.0-mgr-anonymous-sessions.php
@@ -0,0 +1,43 @@
+<?php
+
+/**
+ * Ensure the manager context always starts PHP sessions.
+ *
+ * Fixes #16424: with system anonymous_sessions=No and no session cookie,
+ * manager login could not start a session. Keep anonymous_sessions enabled
+ * on the mgr context so public contexts can still disable it.
+ *
+ * @var modX $modx
+ * @package setup
+ */
+
+use MODX\Revolution\modContext;
+use MODX\Revolution\modContextSetting;
+
+$criteria = [
+    'context_key' => modContext::CONTEXT_MANAGER,
+    'key' => 'anonymous_sessions',
+];
+
+$setting = $modx->getObject(modContextSetting::class, $criteria);
+if (!$setting) {
+    $setting = $modx->newObject(modContextSetting::class);
+    $setting->fromArray([
+        'context_key' => modContext::CONTEXT_MANAGER,
+        'key' => 'anonymous_sessions',
+        'value' => true,
+        'xtype' => 'combo-boolean',
+        'namespace' => 'core',
+        'area' => 'session',
+    ], '', true, true);
+    $setting->save();
+} elseif (!$modx->paramValueIsTrue(['value' => $setting->get('value')], 'value')) {
+    $setting->set('value', true);
+    $setting->save();
+}
+
+if ($modx->cacheManager) {
+    $modx->cacheManager->refresh([
+        'context_settings' => ['contexts' => [modContext::CONTEXT_MANAGER]],
+    ]);
+}
diff --git a/setup/includes/upgrades/mysql/3.3.0-pl.php b/setup/includes/upgrades/mysql/3.3.0-pl.php
new file mode 100644
index 00000000000..026b8a2a7ee
--- /dev/null
+++ b/setup/includes/upgrades/mysql/3.3.0-pl.php
@@ -0,0 +1,12 @@
+<?php
+
+/**
+ * Specific upgrades for Revolution 3.3.0-pl
+ *
+ * @var modX $modx
+ * @var modInstallVersion $this
+ * @package setup
+ * @subpackage upgrades
+ */
+
+include dirname(__DIR__) . '/common/3.3.0-mgr-anonymous-sessions.php';