octobercms/october · error · SystemException

Missing a valid tab definition.

Error message

Missing a valid tab definition.

What it means

Error "Missing a valid tab definition." thrown in octobercms/october.

Source

Thrown at modules/backend/widgets/Form.php:568

            if (!is_array($eventResult)) {
                continue;
            }

            $result = $eventResult + $result;
        }

        return $result;
    }

    /**
     * onLazyLoadTab renders all fields of a tab in the target tab pane
     */
    public function onLazyLoadTab()
    {
        $target  = post('target');

        if (!$tabName = post('name')) {
            throw new SystemException(Lang::get('backend::lang.form.missing_tab'));
        }

        $tab = $this->getTab(post('section', 'primary'));

        $fields = $tab !== null ? array_get($tab->getFields(), $tabName) : [];

        return [
            $target => $this->makePartial('form_fields', ['fields' => $fields]),
        ];
    }

    /**
     * defineFormFields creates a flat array of form fields from the configuration
     * and slots fields in to their respective tabs
     */
    protected function defineFormFields()
    {
        if ($this->fieldsDefined) {

View on GitHub (pinned to b608633a7e)

When it happens

Trigger: Thrown at modules/backend/widgets/Form.php:568 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/db8042dfcdbdbe0b. Report an issue: GitHub.