BookStackApp/BookStack · error · ThemeModuleException

Invalid JSON in module file at "{$moduleJsonFile}":

Error message

Invalid JSON in module file at "{$moduleJsonFile}": 

What it means

ThemeModuleException thrown in ThemeModuleManager::loadFromFolder when json_decode of the module's bookstack-module.json fails (json_last_error not JSON_ERROR_NONE). Input at fault: a malformed JSON manifest file in the theme modules folder.

Source

Thrown at app/Theming/ThemeModuleManager.php:128

        $this->loadedModules = $modules;

        return $modules;
    }

    protected function loadFromFolder(string $folderName): ThemeModule|null
    {
        $moduleJsonFile = $this->modulesFolderPath . DIRECTORY_SEPARATOR . $folderName . DIRECTORY_SEPARATOR . 'bookstack-module.json';
        if (!file_exists($moduleJsonFile)) {
            return null;
        }

        try {
            $jsonContent = file_get_contents($moduleJsonFile);
            $jsonData = json_decode($jsonContent, true);

            if (json_last_error() !== JSON_ERROR_NONE) {
                throw new ThemeModuleException("Invalid JSON in module file at \"{$moduleJsonFile}\": " . json_last_error_msg());
            }

            $module = ThemeModule::fromJson($jsonData, $folderName);
        } catch (ThemeModuleException $exception) {
            throw $exception;
        } catch (\Exception $exception) {
            throw new ThemeModuleException("Failed loading module from \"{$moduleJsonFile}\" with error: {$exception->getMessage()}");
        }

        return $module;
    }
}

View on GitHub (pinned to 18f8469a1c)

Solutions

1. Open the bookstack-module.json file and fix JSON syntax errors (the message includes json_last_error_msg)
2. Validate the JSON with a linter before installing the module
3. Re-download/reinstall the module in case its manifest is corrupted

When it happens

Trigger: Thrown at app/Theming/ThemeModuleManager.php:128 when the library encounters an invalid state.

Common situations: See trigger scenarios.

Understand the failure class

• Parsing and encoding errors: unexpected token, malformed input — why parsers reject input and how to find the real culprit.

AI-assisted analysis of BookStackApp/BookStack@18f8469a1c (2026-09-02). Data as JSON: /api/errors/051f28629e80b0e6. Report an issue: GitHub.