diff --git a/.upgradenotes/MDL-88176-2026031613182551.yml b/.upgradenotes/MDL-88176-2026031613182551.yml
new file mode 100644
index 00000000000..9ee65adfa11
--- /dev/null
+++ b/.upgradenotes/MDL-88176-2026031613182551.yml
@@ -0,0 +1,8 @@
+issueNumber: MDL-88176
+notes:
+  core_customfield:
+    - message: >-
+        The base `\core_customfield\handler` class now implements static
+        caching/reset itself, so all implementations of the same from extending
+        handler classes should be removed
+      type: changed
diff --git a/public/cohort/classes/customfield/cohort_handler.php b/public/cohort/classes/customfield/cohort_handler.php
index 99d8545ec5e..26b7bdbb0b1 100644
--- a/public/cohort/classes/customfield/cohort_handler.php
+++ b/public/cohort/classes/customfield/cohort_handler.php
@@ -27,36 +27,6 @@ use core_customfield\field_controller;
  * @license   http://www.gnu.org/copyleft/gpl.html GNU GPL v3 or later
  */
 class cohort_handler extends handler {
-
-    /**
-     * @var cohort_handler
-     */
-    static protected $singleton;
-
-    /**
-     * Returns a singleton.
-     *
-     * @param int $itemid
-     * @return \core_customfield\handler
-     */
-    public static function create(int $itemid = 0): handler {
-        if (static::$singleton === null) {
-            self::$singleton = new static(0);
-        }
-        return self::$singleton;
-    }
-
-    /**
-     * Run reset code after unit tests to reset the singleton usage.
-     */
-    public static function reset_caches(): void {
-        if (!PHPUNIT_TEST) {
-            throw new \coding_exception('This feature is only intended for use in unit tests');
-        }
-
-        static::$singleton = null;
-    }
-
     /**
      * The current user can configure custom fields on this component.
      *
diff --git a/public/contentbank/classes/customfield/content_handler.php b/public/contentbank/classes/customfield/content_handler.php
index 076230ce29d..2ebaf843172 100644
--- a/public/contentbank/classes/customfield/content_handler.php
+++ b/public/contentbank/classes/customfield/content_handler.php
@@ -27,12 +27,6 @@ use core_customfield\field_controller;
  * @license   https://www.gnu.org/copyleft/gpl.html GNU GPL v3 or later
  */
 class content_handler extends \core_customfield\handler {
-
-    /**
-     * @var content_handler
-     */
-    static protected $singleton;
-
     /**
      * @var \context
      */
@@ -43,30 +37,6 @@ class content_handler extends \core_customfield\handler {
     /** @var int Field is not displayed in the content bank edit page */
     const NOTVISIBLE = 0;
 
-    /**
-     * Returns a singleton
-     *
-     * @param int $itemid
-     * @return \core_contentbank\customfield\content_handler
-     */
-    public static function create(int $itemid = 0): \core_contentbank\customfield\content_handler {
-        if (static::$singleton === null) {
-            self::$singleton = new static(0);
-        }
-        return self::$singleton;
-    }
-
-    /**
-     * Run reset code after unit tests to reset the singleton usage.
-     */
-    public static function reset_caches(): void {
-        if (!PHPUNIT_TEST) {
-            throw new \coding_exception('This feature is only intended for use in unit tests');
-        }
-
-        static::$singleton = null;
-    }
-
     /**
      * The current user can configure custom fields on this component.
      *
diff --git a/public/course/classes/customfield/course_handler.php b/public/course/classes/customfield/course_handler.php
index 42e42d86705..7d7616293ae 100644
--- a/public/course/classes/customfield/course_handler.php
+++ b/public/course/classes/customfield/course_handler.php
@@ -14,6 +14,10 @@
 // You should have received a copy of the GNU General Public License
 // along with Moodle.  If not, see <http://www.gnu.org/licenses/>.
 
+namespace core_course\customfield;
+
+use core_customfield\field_controller;
+
 /**
  * Course handler for custom fields
  *
@@ -21,27 +25,7 @@
  * @copyright 2018 David Matamoros <davidmc@moodle.com>
  * @license   http://www.gnu.org/copyleft/gpl.html GNU GPL v3 or later
  */
-
-namespace core_course\customfield;
-
-defined('MOODLE_INTERNAL') || die;
-
-use core_customfield\field_controller;
-
-/**
- * Course handler for custom fields
- *
- * @package core_course
- * @copyright 2018 David Matamoros <davidmc@moodle.com>
- * @license   http://www.gnu.org/copyleft/gpl.html GNU GPL v3 or later
- */
 class course_handler extends \core_customfield\handler {
-
-    /**
-     * @var course_handler
-     */
-    static protected $singleton;
-
     /**
      * @var \context
      */
@@ -54,30 +38,6 @@ class course_handler extends \core_customfield\handler {
     /** @var int Field is not displayed in the course listing */
     const NOTVISIBLE = 0;
 
-    /**
-     * Returns a singleton
-     *
-     * @param int $itemid
-     * @return \core_course\customfield\course_handler
-     */
-    public static function create(int $itemid = 0): \core_customfield\handler {
-        if (static::$singleton === null) {
-            self::$singleton = new static(0);
-        }
-        return self::$singleton;
-    }
-
-    /**
-     * Run reset code after unit tests to reset the singleton usage.
-     */
-    public static function reset_caches(): void {
-        if (!PHPUNIT_TEST) {
-            throw new \coding_exception('This feature is only intended for use in unit tests');
-        }
-
-        static::$singleton = null;
-    }
-
     /**
      * The current user can configure custom fields on this component.
      *
diff --git a/public/customfield/classes/customfield/shared_handler.php b/public/customfield/classes/customfield/shared_handler.php
index f4c13a18e95..4cb9e214c6a 100644
--- a/public/customfield/classes/customfield/shared_handler.php
+++ b/public/customfield/classes/customfield/shared_handler.php
@@ -20,7 +20,6 @@ namespace core_customfield\customfield;
 
 use core\context;
 use core\context\system;
-use core\exception\coding_exception;
 use core\url;
 use core_customfield\field_controller;
 
@@ -32,35 +31,6 @@ use core_customfield\field_controller;
  * @license    http://www.gnu.org/copyleft/gpl.html GNU GPL v3 or later
  */
 class shared_handler extends \core_customfield\handler {
-    /**
-     * @var shared_handler|null
-     */
-    protected static ?shared_handler $singleton = null;
-
-    /**
-     * Returns a singleton
-     *
-     * @param int $itemid
-     * @return self
-     */
-    public static function create(int $itemid = 0): self {
-        if (static::$singleton === null) {
-            self::$singleton = new static($itemid);
-        }
-        return self::$singleton;
-    }
-
-    /**
-     * Run reset code after unit tests to reset the singleton usage.
-     */
-    public static function reset_caches(): void {
-        if (!PHPUNIT_TEST) {
-            throw new coding_exception('This feature is only intended for use in unit tests');
-        }
-
-        static::$singleton = null;
-    }
-
     /**
      * The current user can configure custom fields on this component.
      *
diff --git a/public/customfield/classes/handler.php b/public/customfield/classes/handler.php
index c5c6fab9ff7..94bb31d0ebf 100644
--- a/public/customfield/classes/handler.php
+++ b/public/customfield/classes/handler.php
@@ -14,24 +14,15 @@
 // You should have received a copy of the GNU General Public License
 // along with Moodle.  If not, see <http://www.gnu.org/licenses/>.
 
-/**
- * The abstract custom fields handler
- *
- * @package   core_customfield
- * @copyright 2018 David Matamoros <davidmc@moodle.com>
- * @license   http://www.gnu.org/copyleft/gpl.html GNU GPL v3 or later
- */
-
 namespace core_customfield;
 
 use backup_nested_element;
+use core\exception\coding_exception;
 use core_customfield\output\field_data;
 use stdClass;
 
-defined('MOODLE_INTERNAL') || die;
-
 /**
- * Base class for custom fields handlers
+ * The abstract custom fields handler
  *
  * This handler provides callbacks for field configuration form and also allows to add the fields to the instance editing form
  *
@@ -46,11 +37,13 @@ defined('MOODLE_INTERNAL') || die;
  * - \core_customfield\api::get_field($fieldid)
  * - \core_customfield\api::get_category($categoryid)
  *
- * @package core_customfield
+ * @package   core_customfield
  * @copyright 2018 David Matamoros <davidmc@moodle.com>
  * @license   http://www.gnu.org/copyleft/gpl.html GNU GPL v3 or later
  */
 abstract class handler {
+    /** @var handler[] $instances */
+    private static $instances = [];
 
     /**
      * The component this handler handles
@@ -95,13 +88,31 @@ abstract class handler {
     /**
      * Returns an instance of the handler
      *
-     * Some areas may choose to use singleton/caching here
+     * We statically cache the list of instances during request lifecycle, to allow this method to be called
+     * repeatedly without potential performance problems
      *
      * @param int $itemid
      * @return static
      */
     public static function create(int $itemid = 0): handler {
-        return new static($itemid);
+        $instancekey = static::class . ':' . $itemid;
+        if (!array_key_exists($instancekey, static::$instances)) {
+            static::$instances[$instancekey] = new static($itemid);
+        }
+        return static::$instances[$instancekey];
+    }
+
+    /**
+     * Run reset code after tests to reset the instance cache
+     *
+     * @throws coding_exception If called outside of test infrastructure
+     */
+    public static function reset_caches(): void {
+        if (PHPUNIT_TEST || defined('BEHAT_TEST')) {
+            static::$instances = [];
+        } else {
+            throw new coding_exception('This feature is only intended for use in tests');
+        }
     }
 
     /**
diff --git a/public/group/classes/customfield/group_handler.php b/public/group/classes/customfield/group_handler.php
index ffa47249cd9..cbde105d1b0 100644
--- a/public/group/classes/customfield/group_handler.php
+++ b/public/group/classes/customfield/group_handler.php
@@ -34,36 +34,6 @@ use restore_task;
  * @license   http://www.gnu.org/copyleft/gpl.html GNU GPL v3 or later
  */
 class group_handler extends handler {
-
-    /**
-     * @var group_handler
-     */
-    static protected $singleton;
-
-    /**
-     * Returns a singleton.
-     *
-     * @param int $itemid
-     * @return \core_customfield\handler
-     */
-    public static function create(int $itemid = 0): handler {
-        if (static::$singleton === null) {
-            self::$singleton = new static(0);
-        }
-        return self::$singleton;
-    }
-
-    /**
-     * Run reset code after unit tests to reset the singleton usage.
-     */
-    public static function reset_caches(): void {
-        if (!PHPUNIT_TEST) {
-            throw new \coding_exception('This feature is only intended for use in unit tests');
-        }
-
-        static::$singleton = null;
-    }
-
     /**
      * The current user can configure custom fields on this component.
      *
diff --git a/public/group/classes/customfield/grouping_handler.php b/public/group/classes/customfield/grouping_handler.php
index 1bd951bb3f0..9a95813ebcf 100644
--- a/public/group/classes/customfield/grouping_handler.php
+++ b/public/group/classes/customfield/grouping_handler.php
@@ -34,36 +34,6 @@ use restore_task;
  * @license   http://www.gnu.org/copyleft/gpl.html GNU GPL v3 or later
  */
 class grouping_handler extends handler {
-
-    /**
-     * @var grouping_handler
-     */
-    static protected $singleton;
-
-    /**
-     * Returns a singleton.
-     *
-     * @param int $itemid
-     * @return \core_customfield\handler
-     */
-    public static function create(int $itemid = 0): handler {
-        if (static::$singleton === null) {
-            self::$singleton = new static(0);
-        }
-        return self::$singleton;
-    }
-
-    /**
-     * Run reset code after unit tests to reset the singleton usage.
-     */
-    public static function reset_caches(): void {
-        if (!PHPUNIT_TEST) {
-            throw new \coding_exception('This feature is only intended for use in unit tests');
-        }
-
-        static::$singleton = null;
-    }
-
     /**
      * The current user can configure custom fields on this component.
      *
diff --git a/public/lib/behat/classes/util.php b/public/lib/behat/classes/util.php
index c8708eddbc9..348510123cf 100644
--- a/public/lib/behat/classes/util.php
+++ b/public/lib/behat/classes/util.php
@@ -422,6 +422,7 @@ class behat_util extends \core\test\testing_util {
 
         filter_manager::reset_caches();
 
+        \core_customfield\handler::reset_caches();
         \core_reportbuilder\manager::reset_caches();
 
         // Reset course and module caches.
diff --git a/public/lib/classes/test/phpunit/phpunit_util.php b/public/lib/classes/test/phpunit/phpunit_util.php
index 651c2bad181..bab1060fb34 100644
--- a/public/lib/classes/test/phpunit/phpunit_util.php
+++ b/public/lib/classes/test/phpunit/phpunit_util.php
@@ -251,27 +251,12 @@ class phpunit_util extends \core\test\testing_util {
         if (class_exists(\core\update\checker::class)) {
             \core\update\checker::reset_caches(true);
         }
-        if (class_exists(\core_course\customfield\course_handler::class)) {
-            \core_course\customfield\course_handler::reset_caches();
+        if (class_exists(\core_customfield\handler::class)) {
+            \core_customfield\handler::reset_caches();
         }
         if (class_exists(\core_reportbuilder\manager::class)) {
             \core_reportbuilder\manager::reset_caches();
         }
-        if (class_exists(\core_cohort\customfield\cohort_handler::class)) {
-            \core_cohort\customfield\cohort_handler::reset_caches();
-        }
-        if (class_exists(\core_group\customfield\group_handler::class)) {
-            \core_group\customfield\group_handler::reset_caches();
-        }
-        if (class_exists(\core_group\customfield\grouping_handler::class)) {
-            \core_group\customfield\grouping_handler::reset_caches();
-        }
-        if (class_exists(\core_reportbuilder\customfield\report_handler::class)) {
-            \core_reportbuilder\customfield\report_handler::reset_caches();
-        }
-        if (class_exists(\core_customfield\customfield\shared_handler::class)) {
-            \core_customfield\customfield\shared_handler::reset_caches();
-        }
 
         // Clear static cache within restore.
         if (class_exists(\restore_section_structure_step::class)) {
diff --git a/public/question/bank/customfields/classes/customfield/question_handler.php b/public/question/bank/customfields/classes/customfield/question_handler.php
index 785bd790882..86892009b80 100644
--- a/public/question/bank/customfields/classes/customfield/question_handler.php
+++ b/public/question/bank/customfields/classes/customfield/question_handler.php
@@ -29,12 +29,6 @@ use core_customfield\output\field_data;
  * @license     http://www.gnu.org/copyleft/gpl.html GNU GPL v3 or later
  */
 class question_handler extends \core_customfield\handler {
-
-    /**
-     * @var question_handler
-     */
-    static protected $singleton;
-
     /**
      * @var \context
      */
@@ -47,32 +41,6 @@ class question_handler extends \core_customfield\handler {
     /** @var int Field is not displayed in the question display and question preview */
     const NOTVISIBLE = 0;
 
-    /**
-     * Creates the custom field handler and returns a singleton.
-     * Itemid is always zero as the custom fields are the same
-     * for every question across the system.
-     *
-     * @param int $itemid Always zero.
-     * @return \qbank_customfields\customfield\question_handler
-     */
-    public static function create(int $itemid = 0): \core_customfield\handler {
-        if (static::$singleton === null) {
-            self::$singleton = new static(0);
-        }
-        return self::$singleton;
-    }
-
-    /**
-     * Run reset code after unit tests to reset the singleton usage.
-     */
-    public static function reset_caches(): void {
-        if (!PHPUNIT_TEST) {
-            throw new \coding_exception('This feature is only intended for use in unit tests');
-        }
-
-        static::$singleton = null;
-    }
-
     /**
      * The current user can configure custom fields on this component.
      *
diff --git a/public/reportbuilder/classes/customfield/report_handler.php b/public/reportbuilder/classes/customfield/report_handler.php
index 37b9933aba4..5c756824742 100644
--- a/public/reportbuilder/classes/customfield/report_handler.php
+++ b/public/reportbuilder/classes/customfield/report_handler.php
@@ -20,7 +20,6 @@ namespace core_reportbuilder\customfield;
 
 use core\context;
 use core\context\system;
-use core\exception\coding_exception;
 use core\url;
 use core_customfield\field_controller;
 use core_reportbuilder\local\models\report;
@@ -35,35 +34,6 @@ use core_reportbuilder\permission;
  * @license    http://www.gnu.org/copyleft/gpl.html GNU GPL v3 or later
  */
 class report_handler extends \core_customfield\handler {
-    /**
-     * @var report_handler|null
-     */
-    protected static ?report_handler $singleton = null;
-
-    /**
-     * Returns a singleton
-     *
-     * @param int $itemid
-     * @return self
-     */
-    public static function create(int $itemid = 0): self {
-        if (static::$singleton === null) {
-            self::$singleton = new static($itemid);
-        }
-        return self::$singleton;
-    }
-
-    /**
-     * Run reset code after unit tests to reset the singleton usage.
-     */
-    public static function reset_caches(): void {
-        if (!PHPUNIT_TEST) {
-            throw new coding_exception('This feature is only intended for use in unit tests');
-        }
-
-        static::$singleton = null;
-    }
-
     /**
      * The current user can configure custom fields on this component.
      *