octobercms/october · error · ApplicationException

AJAX handler ':name' was not found.

Error message

AJAX handler ':name' was not found.

What it means

Error "AJAX handler ':name' was not found." thrown in octobercms/october.

Source

Thrown at modules/backend/classes/Controller.php:555

                 */
                if ($event = $this->fireSystemEvent('backend.ajax.beforeRunHandler', [$handler])) {
                    $response = ajax()::wrap($event);
                }
                else {
                    $response = $this->callAjaxAction($this->action, $this->params);
                }
            }
            catch (ComponentNotFound $ex) {
                throw new SystemException(Lang::get('backend::lang.widget.not_bound', ['name'=>$this->getAjaxRequest()->component]));
            }
            catch (MassAssignmentException $ex) {
                throw new SystemException(Lang::get('backend::lang.model.mass_assignment_failed', ['attribute' => $ex->getMessage()]));
            }
            catch (HandlerNameInvalid $ex) {
                throw new ApplicationException(Lang::get('backend::lang.ajax_handler.invalid_name', ['name'=>$handler]));
            }
            catch (HandlerNotFound $ex) {
                throw new ApplicationException(Lang::get('backend::lang.ajax_handler.not_found', ['name'=>e($handler)]));
            }
        }
        catch (ValidationException $ex) {
            Flash::error($ex->getMessage());
            $response = ajax()->invalidFields($ex->errors());
        }
        catch (Throwable $ex) {
            report($ex);
            $response = ajax()->exception($ex);
        }

        if ($this->hasAssetsDefined()) {
            foreach ($this->getAssetPathsWithAttributes() as $type => $paths) {
                $response->asset($type, $paths);
            }
        }

        $response = $this->outputVueComponentsForAjax($response);

View on GitHub (pinned to b608633a7e)

When it happens

Trigger: Thrown at modules/backend/classes/Controller.php:555 when the library encounters an invalid state.

Common situations: See trigger scenarios.

AI-assisted analysis of octobercms/october@b608633a7e (2026-08-21). Data as JSON: /api/errors/8cf2b1a7d0a80c7a. Report an issue: GitHub.