What causes "cms::lang.theme.active.is_locked" in octobercms/october?

Switch the active theme to a real, unlocked theme via config or the backend theme picker.

octobercms/october · error · ApplicationException

cms::lang.theme.active.is_locked

Error message

cms::lang.theme.active.is_locked

What it means

ApplicationException thrown by `Theme::getActiveTheme()` when the resolved active theme is locked: its directory contains a `.themelock` file (`isLocked()`). Locked themes are treated as non-production templates (the framework's demo themes ship locked), so the CMS refuses to use them for front-end rendering even though the theme itself is valid.

Source

Thrown at modules/cms/classes/Theme.php:212

            throw new SystemException(Lang::get('cms::lang.theme.active.not_set'));
        }

        return $activeTheme;
    }

    /**
     * getActiveTheme returns the active theme object
     */
    public static function getActiveTheme(): ?Theme
    {
        if (self::$activeThemeCache !== false) {
            return self::$activeThemeCache;
        }

        $theme = static::load($themeCode = static::getActiveThemeCode());

        if ($theme->isLocked()) {
            throw new ApplicationException(Lang::get('cms::lang.theme.active.is_locked', ['theme' => $themeCode]));
        }

        if (!$theme->isValid()) {
            return self::$activeThemeCache = null;
        }

        return self::$activeThemeCache = $theme;
    }

    /**
     * setActiveTheme sets the active theme
     *
     * The active theme code is stored in the database and overrides the
     * configuration cms.active_theme config item.
     */
    public static function setActiveTheme(string $code)
    {
        $theme = static::load($code);

View on GitHub (pinned to b608633a7e)

Solutions

Switch the active theme to a real, unlocked theme via config or the backend theme picker.
If the theme is genuinely yours, delete the `.themelock` file from its root: `rm themes/<theme>/.themelock`.
Audit copied/starter themes for a stray .themelock before deploying.

Example fix

# before — demo theme locked, cannot be active
$ ls themes/demo-theme/.themelock
themes/demo-theme/.themelock

# after — only if you intend to use it as your production theme
rm themes/demo-theme/.themelock
# otherwise pick another theme in the backend

Defensive patterns

Strategy: validation

Validate before calling

use Cms\Classes\Theme;

$theme = Theme::load($code);
if ($theme->isLocked()) {
    // refuse before rendering: locked themes are demo-only
    abort(500, "Theme '{$code}' is locked and cannot be used as the active theme.");
}
$theme = Theme::getActiveTheme();

Try / catch

try {
    $theme = Theme::getActiveTheme();
} catch (ApplicationException $e) {
    // locked active theme — page can't render; show maintenance and alert ops
    Log::critical('Active theme is locked');
    return response()->view('errors.maintenance', [], 503);
}

Prevention

Check for .themelock before promoting any demo/starter theme to active.
Keep .themelock out of custom themes (review starter-kit copies).
Automate a pre-deploy assertion: active theme code must exist and not be locked.

When it happens

Trigger: Configuring a demo theme (one that ships `themes/<demo>/.themelock`) as cms.active_theme, or its code being stored on the site record; then requesting any front-end page.

Common situations: Enabling the framework demo theme on production to 'quickly show something'; copying a demo theme as a starter without removing the lock file; theme lock file accidentally committed into a custom theme.

Related errors

AI-assisted analysis of octobercms/october@b608633a7e (2026-08-21). Data as JSON: /api/errors/4962d38b5509af8e. Report an issue: GitHub.