[5.x]: Craft cannot process certain queue requests when runQueueAutomatically() is set to true - Session errors

[terryupton]

What happened?

Description

Since Craft 5.9.19 - I am seeing that Craft cannot process queue requests automatically, if the setting runQueueAutomatically() is set to true.

In the queue panel - seeing errors like this;
session_set_save_handler(): Session save handler cannot be changed after headers have already been sent (sent from /home/ploi/dev.pemuk.com/vendor/yiisoft/yii2/web/Response.php on line 442)

This is occurring with standard Craft jobs like;

Standard Craft Queue Jobs like craft\queue\jobs\PruneRevisions or craft\queue\jobs\UpdateSearchIndex

If the queue is run manually or on a cronjob or worker then it seems to work ok.

Steps to reproduce

1. Upgrade to Craft 5.9.19
2. Ensure runQueueAutomatically() is set to true
3. Login to the CP and wait for a queue item to try and run or try and trigger one with a change and an UpdateSearchIndex

Expected behavior

1. Queue should run and process the jobs automatically.

Actual behavior

1. Queue job failes ad remains in the queue with errors like session_set_save_handler(): Session save handler cannot be changed after headers have already been sent (sent from /home/ploi/dev.pemuk.com/vendor/yiisoft/yii2/web/Response.php on line 442)

Craft CMS version

5.9.20

PHP version

8.5.5

Operating system and version

Linux 6.8.0-107-generic

Database type and version

MySQL 8.0.45

Image driver and version

Imagick 3.8.1 (ImageMagick 6.9.12-98)

Installed plugins and versions

No response

[linear]

CMS-1970

[i-just]

Hi, thanks for reaching out! Can you share a full stack trace for this one?

[terryupton]

@i-just is this what you require?

2026-04-21 13:22:37 [queue.INFO] [yii\db\Connection::open] Opening DB connection: mysql:host=127.0.0.1;dbname=pem_dev;port=3306 {"memory":1171968} 
2026-04-21 13:22:37 [queue.INFO] [yii\web\Session::open] Session started {"memory":1284192} 
2026-04-21 13:22:37 [queue.INFO] [nystudio107\codeeditor\CodeEditor::bootstrap] CodeEditor module bootstrapped {"memory":1308176} 
2026-04-21 13:22:37 [queue.INFO] [simplygoodwork\donkeytail\Donkeytail::init] Donkeytail plugin loaded {"memory":3039224} 
2026-04-21 13:22:37 [queue.INFO] [croxton\imgixer\Imgixer::init] Imgixer plugin loaded {"memory":4016400} 
2026-04-21 13:22:37 [queue.INFO] [nystudio107\retour\Retour::init] Retour plugin loaded {"memory":4055984} 
2026-04-21 13:22:37 [queue.INFO] [nystudio107\seomatic\Seomatic::init] SEO & Social Media plugin loaded {"memory":4394912} 
2026-04-21 13:22:37 [queue.INFO] [nystudio107\vite\Vite::init] Vite plugin loaded {"memory":4422992} 
2026-04-21 13:22:37 [queue.INFO] [yii\db\Connection::open] Opening DB connection: mysql:host=127.0.0.1;dbname=pem_dev;port=3306 {"memory":4934568} 
2026-04-21 13:22:37 [queue.INFO] [craft\queue\QueueLogBehavior::beforeExec]  [86904] t9n:["app","Updating search indexes"] (attempt: 1, pid: 324563) - Started {"memory":5012424} 
2026-04-21 13:22:37 [queue.ERROR] [craft\queue\QueueLogBehavior::afterError]  [86904] t9n:["app","Updating search indexes"] (attempt: 1, pid: 324563) - Error (time: 0.137s): session_set_save_handler(): Session save handler cannot be changed after headers have already been sent (sent from /home/ploi/dev.pemuk.com/vendor/yiisoft/yii2/web/Response.php on line 442) {"memory":7510064} 
2026-04-21 13:22:37 [queue.ERROR] [yii\base\ErrorException:2] yii\base\ErrorException: session_set_save_handler(): Session save handler cannot be changed after headers have already been sent (sent from /home/ploi/dev.pemuk.com/vendor/yiisoft/yii2/web/Response.php on line 442) in /home/ploi/dev.pemuk.com/vendor/yiisoft/yii2/web/Session.php:199
Stack trace:
#0 /home/ploi/dev.pemuk.com/vendor/craftcms/cms/src/web/ErrorHandler.php(115): yii\base\ErrorHandler->handleError()
#1 [internal function]: craft\web\ErrorHandler->handleError()
#2 /home/ploi/dev.pemuk.com/vendor/yiisoft/yii2/web/Session.php(199): session_set_save_handler()
#3 /home/ploi/dev.pemuk.com/vendor/yiisoft/yii2/web/Session.php(149): yii\web\Session->registerSessionHandler()
#4 /home/ploi/dev.pemuk.com/vendor/yiisoft/yii2/web/Session.php(761): yii\web\Session->open()
#5 /home/ploi/dev.pemuk.com/vendor/craftcms/cms/src/helpers/Session.php(95): yii\web\Session->has()
#6 /home/ploi/dev.pemuk.com/vendor/craftcms/cms/src/services/Sites.php(1281): craft\helpers\Session::has()
#7 /home/ploi/dev.pemuk.com/vendor/craftcms/cms/src/services/Sites.php(431): craft\services\Sites->_allSites()
#8 /home/ploi/dev.pemuk.com/vendor/craftcms/cms/src/elements/db/ElementQuery.php(1039): craft\services\Sites->getAllSiteIds()
#9 /home/ploi/dev.pemuk.com/vendor/craftcms/cms/src/elements/db/ElementQuery.php(636): craft\elements\db\ElementQuery->site()
#10 /home/ploi/dev.pemuk.com/vendor/craftcms/cms/src/elements/db/NestedElementQueryTrait.php(88): craft\elements\db\ElementQuery->__set()
#11 /home/ploi/dev.pemuk.com/vendor/craftcms/cms/src/elements/db/EntryQuery.php(247): craft\elements\db\EntryQuery->nestedTraitSet()
#12 /home/ploi/dev.pemuk.com/vendor/yiisoft/yii2/BaseYii.php(572): craft\elements\db\EntryQuery->__set()
#13 /home/ploi/dev.pemuk.com/vendor/craftcms/cms/src/services/Elements.php(3506): yii\BaseYii::configure()
#14 /home/ploi/dev.pemuk.com/vendor/craftcms/cms/src/services/Elements.php(3409): craft\services\Elements->_eagerLoadElementsInternal()
#15 /home/ploi/dev.pemuk.com/vendor/craftcms/cms/src/base/NestedElementTrait.php(202): craft\services\Elements->eagerLoadElements()
#16 /home/ploi/dev.pemuk.com/vendor/craftcms/cms/src/base/NestedElementTrait.php(273): craft\elements\Entry->getPrimaryOwner()
#17 /home/ploi/dev.pemuk.com/vendor/craftcms/cms/src/base/NestedElementTrait.php(373): craft\elements\Entry->getOwner()
#18 /home/ploi/dev.pemuk.com/vendor/craftcms/cms/src/elements/Entry.php(1698): craft\elements\Entry->getField()
#19 /home/ploi/dev.pemuk.com/vendor/craftcms/cms/src/elements/Entry.php(1741): craft\elements\Entry->getAvailableEntryTypes()
#20 /home/ploi/dev.pemuk.com/vendor/craftcms/cms/src/elements/Entry.php(1619): craft\elements\Entry->getType()
#21 /home/ploi/dev.pemuk.com/vendor/craftcms/cms/src/services/Search.php(155): craft\elements\Entry->getFieldLayout()
#22 /home/ploi/dev.pemuk.com/vendor/craftcms/cms/src/services/Search.php(345): craft\services\Search->indexElementAttributes()
#23 /home/ploi/dev.pemuk.com/vendor/craftcms/cms/src/queue/jobs/UpdateSearchIndex.php(62): craft\services\Search->indexElementIfQueued()
#24 /home/ploi/dev.pemuk.com/vendor/yiisoft/yii2-queue/src/Queue.php(251): craft\queue\jobs\UpdateSearchIndex->execute()
#25 /home/ploi/dev.pemuk.com/vendor/yiisoft/yii2-queue/src/cli/Queue.php(149): yii\queue\Queue->handleMessage()
#26 /home/ploi/dev.pemuk.com/vendor/craftcms/cms/src/queue/Queue.php(192): yii\queue\cli\Queue->handleMessage()
#27 /home/ploi/dev.pemuk.com/vendor/craftcms/cms/src/queue/Queue.php(167): craft\queue\Queue->executeJob()
#28 [internal function]: craft\queue\Queue->{closure:craft\queue\Queue::run():165}()
#29 /home/ploi/dev.pemuk.com/vendor/yiisoft/yii2-queue/src/cli/Queue.php(116): call_user_func()
#30 /home/ploi/dev.pemuk.com/vendor/craftcms/cms/src/queue/Queue.php(165): yii\queue\cli\Queue->runWorker()
#31 /home/ploi/dev.pemuk.com/vendor/craftcms/cms/src/controllers/QueueController.php(98): craft\queue\Queue->run()
#32 /home/ploi/dev.pemuk.com/vendor/craftcms/cms/src/controllers/QueueController.php(118): craft\controllers\QueueController->actionRun()
#33 [internal function]: craft\controllers\QueueController->actionRetry()
#34 /home/ploi/dev.pemuk.com/vendor/yiisoft/yii2/base/InlineAction.php(66): call_user_func_array()
#35 /home/ploi/dev.pemuk.com/vendor/yiisoft/yii2/base/Controller.php(197): yii\base\InlineAction->runWithParams()
#36 /home/ploi/dev.pemuk.com/vendor/yiisoft/yii2/base/Module.php(554): yii\base\Controller->runAction()
#37 /home/ploi/dev.pemuk.com/vendor/craftcms/cms/src/web/Application.php(368): yii\base\Module->runAction()
#38 /home/ploi/dev.pemuk.com/vendor/craftcms/cms/src/web/Application.php(635): craft\web\Application->runAction()
#39 /home/ploi/dev.pemuk.com/vendor/craftcms/cms/src/web/Application.php(330): craft\web\Application->_processActionRequest()
#40 /home/ploi/dev.pemuk.com/vendor/yiisoft/yii2/base/Application.php(391): craft\web\Application->handleRequest()
#41 /home/ploi/dev.pemuk.com/web/index.php(12): yii\base\Application->run()
#42 {main} {"memory":7510336,"exception":"[object] (yii\\base\\ErrorException(code: 2): session_set_save_handler(): Session save handler cannot be changed after headers have already been sent (sent from /home/ploi/dev.pemuk.com/vendor/yiisoft/yii2/web/Response.php on line 442) at /home/ploi/dev.pemuk.com/vendor/yiisoft/yii2/web/Session.php:199)"} 
2026-04-21 13:22:37 [queue.ERROR] [yii\base\ErrorException:2] yii\base\ErrorException: session_set_save_handler(): Session save handler cannot be changed after headers have already been sent (sent from /home/ploi/dev.pemuk.com/vendor/yiisoft/yii2/web/Response.php on line 442) in /home/ploi/dev.pemuk.com/vendor/yiisoft/yii2/web/Session.php:199
Stack trace:
#0 /home/ploi/dev.pemuk.com/vendor/craftcms/cms/src/web/ErrorHandler.php(115): yii\base\ErrorHandler->handleError()
#1 [internal function]: craft\web\ErrorHandler->handleError()
#2 /home/ploi/dev.pemuk.com/vendor/yiisoft/yii2/web/Session.php(199): session_set_save_handler()
#3 /home/ploi/dev.pemuk.com/vendor/yiisoft/yii2/web/Session.php(149): yii\web\Session->registerSessionHandler()
#4 /home/ploi/dev.pemuk.com/vendor/yiisoft/yii2/web/Session.php(761): yii\web\Session->open()
#5 /home/ploi/dev.pemuk.com/vendor/craftcms/cms/src/helpers/Session.php(95): yii\web\Session->has()
#6 /home/ploi/dev.pemuk.com/vendor/craftcms/cms/src/services/Sites.php(1281): craft\helpers\Session::has()
#7 /home/ploi/dev.pemuk.com/vendor/craftcms/cms/src/services/Sites.php(431): craft\services\Sites->_allSites()
#8 /home/ploi/dev.pemuk.com/vendor/craftcms/cms/src/elements/db/ElementQuery.php(1039): craft\services\Sites->getAllSiteIds()
#9 /home/ploi/dev.pemuk.com/vendor/craftcms/cms/src/elements/db/ElementQuery.php(636): craft\elements\db\ElementQuery->site()
#10 /home/ploi/dev.pemuk.com/vendor/craftcms/cms/src/elements/db/NestedElementQueryTrait.php(88): craft\elements\db\ElementQuery->__set()
#11 /home/ploi/dev.pemuk.com/vendor/craftcms/cms/src/elements/db/EntryQuery.php(247): craft\elements\db\EntryQuery->nestedTraitSet()
#12 /home/ploi/dev.pemuk.com/vendor/yiisoft/yii2/BaseYii.php(572): craft\elements\db\EntryQuery->__set()
#13 /home/ploi/dev.pemuk.com/vendor/craftcms/cms/src/services/Elements.php(3506): yii\BaseYii::configure()
#14 /home/ploi/dev.pemuk.com/vendor/craftcms/cms/src/services/Elements.php(3409): craft\services\Elements->_eagerLoadElementsInternal()
#15 /home/ploi/dev.pemuk.com/vendor/craftcms/cms/src/base/NestedElementTrait.php(202): craft\services\Elements->eagerLoadElements()
#16 /home/ploi/dev.pemuk.com/vendor/craftcms/cms/src/base/NestedElementTrait.php(273): craft\elements\Entry->getPrimaryOwner()
#17 /home/ploi/dev.pemuk.com/vendor/craftcms/cms/src/base/NestedElementTrait.php(373): craft\elements\Entry->getOwner()
#18 /home/ploi/dev.pemuk.com/vendor/craftcms/cms/src/elements/Entry.php(1698): craft\elements\Entry->getField()
#19 /home/ploi/dev.pemuk.com/vendor/craftcms/cms/src/elements/Entry.php(1741): craft\elements\Entry->getAvailableEntryTypes()
#20 /home/ploi/dev.pemuk.com/vendor/craftcms/cms/src/elements/Entry.php(1619): craft\elements\Entry->getType()
#21 /home/ploi/dev.pemuk.com/vendor/craftcms/cms/src/services/Search.php(155): craft\elements\Entry->getFieldLayout()
#22 /home/ploi/dev.pemuk.com/vendor/craftcms/cms/src/services/Search.php(345): craft\services\Search->indexElementAttributes()
#23 /home/ploi/dev.pemuk.com/vendor/craftcms/cms/src/queue/jobs/UpdateSearchIndex.php(62): craft\services\Search->indexElementIfQueued()
#24 /home/ploi/dev.pemuk.com/vendor/yiisoft/yii2-queue/src/Queue.php(251): craft\queue\jobs\UpdateSearchIndex->execute()
#25 /home/ploi/dev.pemuk.com/vendor/yiisoft/yii2-queue/src/cli/Queue.php(149): yii\queue\Queue->handleMessage()
#26 /home/ploi/dev.pemuk.com/vendor/craftcms/cms/src/queue/Queue.php(192): yii\queue\cli\Queue->handleMessage()
#27 /home/ploi/dev.pemuk.com/vendor/craftcms/cms/src/queue/Queue.php(167): craft\queue\Queue->executeJob()
#28 [internal function]: craft\queue\Queue->{closure:craft\queue\Queue::run():165}()
#29 /home/ploi/dev.pemuk.com/vendor/yiisoft/yii2-queue/src/cli/Queue.php(116): call_user_func()
#30 /home/ploi/dev.pemuk.com/vendor/craftcms/cms/src/queue/Queue.php(165): yii\queue\cli\Queue->runWorker()
#31 /home/ploi/dev.pemuk.com/vendor/craftcms/cms/src/controllers/QueueController.php(98): craft\queue\Queue->run()
#32 /home/ploi/dev.pemuk.com/vendor/craftcms/cms/src/controllers/QueueController.php(118): craft\controllers\QueueController->actionRun()
#33 [internal function]: craft\controllers\QueueController->actionRetry()
#34 /home/ploi/dev.pemuk.com/vendor/yiisoft/yii2/base/InlineAction.php(66): call_user_func_array()
#35 /home/ploi/dev.pemuk.com/vendor/yiisoft/yii2/base/Controller.php(197): yii\base\InlineAction->runWithParams()
#36 /home/ploi/dev.pemuk.com/vendor/yiisoft/yii2/base/Module.php(554): yii\base\Controller->runAction()
#37 /home/ploi/dev.pemuk.com/vendor/craftcms/cms/src/web/Application.php(368): yii\base\Module->runAction()
#38 /home/ploi/dev.pemuk.com/vendor/craftcms/cms/src/web/Application.php(635): craft\web\Application->runAction()
#39 /home/ploi/dev.pemuk.com/vendor/craftcms/cms/src/web/Application.php(330): craft\web\Application->_processActionRequest()
#40 /home/ploi/dev.pemuk.com/vendor/yiisoft/yii2/base/Application.php(391): craft\web\Application->handleRequest()
#41 /home/ploi/dev.pemuk.com/web/index.php(12): yii\base\Application->run()
#42 {main} {"memory":7513328,"exception":"[object] (yii\\base\\ErrorException(code: 2): session_set_save_handler(): Session save handler cannot be changed after headers have already been sent (sent from /home/ploi/dev.pemuk.com/vendor/yiisoft/yii2/web/Response.php on line 442) at /home/ploi/dev.pemuk.com/vendor/yiisoft/yii2/web/Session.php:199)"} 
2026-04-21 13:22:37 [queue.INFO] [application] Request context:
$_GET = [
    'v' => '1776774157265'
]

$_FILES = []

$_COOKIE = [
    'CRAFT_CSRF_TOKEN' => '••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••'
    '5507a5cde07a30af714805ffae7dac99_username' => 'd06f0d16399efd6a87c36d0448f8e9444a11057f6cde1b91f40d05585fed46fba:2:{i:0;s:41:\"5507a5cde07a30af714805ffae7dac99_username\";i:1;s:18:\"terry@amasci.co.uk\";}'
    'Craft-5fd44481-1d50-4a0e-98bc-1bfd82cc24b0_sidebar' => 'expanded'
    'cookieyes-consent' => 'consentid:ZFREdjZlM1N2WW03MEZ6d05VdW5mdkVBUThHTmRneUc,consent:yes,action:yes,necessary:yes,functional:yes,analytics:yes,performance:yes,advertisement:yes'
    'Craft-5fd44481-1d50-4a0e-98bc-1bfd82cc24b0_sidebar-details' => 'expanded'
    'PHPSESSID' => 'eb0c8db22b6f8943aa5bf6ef452efc53'
    '5507a5cde07a30af714805ffae7dac99_identity' => 'af69081d3a38591502aefb41940558e8b800706c4ac17371e13de6912eff82c4a:2:{i:0;s:41:\"5507a5cde07a30af714805ffae7dac99_identity\";i:1;s:162:\"[1,\"[\\\"D-_2oGV5ftoanSEfGNJWPFenHkgVKWIBfk-jIGV6r88j6ve_snddpO9-qQUiOVst3mpIyCAZDpbjpelcSaRmWkwC65D6uCx0psDF\\\",null,\\\"562dfcd5b68c64c48b5e26801777ec72\\\"]\",2592000]\";}'
]

$_SESSION = [
    '__flash' => []
    '5507a5cde07a30af714805ffae7dac99__token' => '••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••'
    '5507a5cde07a30af714805ffae7dac99__id' => 1
    '__authKey' => '••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••'
    '5507a5cde07a30af714805ffae7dac99__expire' => 1779366157
    '__duration' => 2592000
]

[brandonkelly]

#4 /home/ploi/dev.pemuk.com/vendor/yiisoft/yii2/web/Session.php(761): yii\web\Session->open()
#5 /home/ploi/dev.pemuk.com/vendor/craftcms/cms/src/helpers/Session.php(95): yii\web\Session->has()

This suggests you’re not actually running Craft 5.9.19+ yet. If you were, step #5 here would have called craft\web\Session->has() rather than yii\web\Session->has(). craft\web\Session::has() is defensive about the error you’re getting (see 1506c09).

Or perhaps you are overriding the session component in config/app.php or config/app.web.php?

[terryupton]

Definitely running Craft 5.9.19+

Here is my app.php which might be changing the sessions following a previous issue with Craft update and Redis if I recall.

craftcms/docs#754

What's the solution for this?

<?php
   /**
    * Yii Application Config
    *
    * Edit this file at your own risk!
    *
    * The array returned by this file will get merged with
    * vendor/craftcms/cms/src/config/app.php and app.[web|console].php, when
    * Craft's bootstrap script is defining the configuration for the entire
    * application.
    *
    * You can define custom modules and system components, and even override the
    * built-in system components.
    *
    * If you want to modify the application config for *only* web requests or
    * *only* console requests, create an app.web.php or app.console.php file in
    * your config/ folder, alongside this one.
    */

   use craft\helpers\App;

   $components = [
      'deprecator' => [
         'throwExceptions' => App::env('CRAFT_DEV_MODE'),
      ]
   ];

   if (App::env('REDIS_HOSTNAME')) {
      $components = array_merge(
         $components,
         [
            'cache'   => [
               'class'           => yii\redis\Cache::class,
               'defaultDuration' => 86400,
               'keyPrefix'       => App::env('CRAFT_APP_ID') . '_cache_',
               'redis'           => [
                  'class'    => yii\redis\Connection::class,
                  'hostname' => App::env('REDIS_HOSTNAME'),
                  'port'     => App::env('REDIS_PORT') ?: 6379,
                  'database' => 1,
               ],
            ],
            'session' => [
               'class'      => yii\redis\Session::class,
               'redis'      => [
                  'class'    => yii\redis\Connection::class,
                  'hostname' => App::env('REDIS_HOSTNAME'),
                  'port'     => App::env('REDIS_PORT') ?: 6379,
                  'database' => 2,
               ],
               'as session' => [
                  'class' => craft\behaviors\SessionBehavior::class,
               ],
            ],
         ]
      );
   }

   return [
      '*' => [
         'id'         => App::env('CRAFT_APP_ID') ?: 'CraftCMS',
         'components' => $components
      ]
   ];

Thanks

[brandonkelly]

Thanks, that helped. Fixed now for the next release.

[terryupton]

Thanks Brandon

[brandonkelly]

Craft 5.9.21 is out with that fix. Thanks again!