twigphp/Twig · error · SyntaxError

Value for argument "output_strategy" is required for…

Error message

Value for argument "output_strategy" is required for function "render_sandboxed".

What it means

render_sandboxed() renders an included template with output escaping controlled by the 'output_strategy' argument. During compilation, Twig resolves the output strategy name from the arguments node; if it cannot find any output_strategy argument at all, compilation fails with this SyntaxError because the strategy is mandatory.

Solutions

Add output_strategy='html' (or the desired strategy) to the render_sandboxed call
Consult the render_sandboxed documentation for valid strategy values
Audit templates that use render_sandboxed after upgrading Twig
If strategy should vary at runtime, ensure a constant fallback is present for compile-time resolution

Example fix

// before (template)
{{ render_sandboxed('widget.html') }}
// after
{{ render_sandboxed('widget.html', output_strategy='html') }}

Defensive patterns

Strategy: validation

Validate before calling

// template source scan before rendering
if (str_contains($templateSource, 'render_sandboxed(')
    && !preg_match('/render_sandboxed\([^)]*output_strategy\s*=/', $templateSource)) {
    throw new \RuntimeException('render_sandboxed call missing output_strategy');
}

Try / catch

try {
    echo $twig->render($template, $ctx);
} catch (\Twig\Error\SyntaxError $e) {
    if (str_contains($e->getMessage(), 'output_strategy')) {
        // add output_strategy='<strategy>' to the call
    }
}

Prevention

Always pass output_strategy explicitly to render_sandboxed
After Twig upgrades, grep templates for render_sandboxed and verify required args
Document the mandatory argument in your team's template style guide

When it happens

Trigger: Calling {{ render_sandboxed(template) }} or using the function without passing output_strategy='html' (or another valid strategy name) as a constant named argument.

Common situations: Upgrading Twig where output_strategy became required; copying older template snippets that predate the requirement; assuming a default strategy exists.

Understand the failure class

Background: "missing required argument" and "the following required arguments were not provided": what required-argument errors mean and how to fix them — this error's family across 20 libraries.

Related errors

AI-assisted analysis of twigphp/Twig@a414c3a491 (2026-09-13). Data as JSON: /api/errors/c368c1ea583f9cd4. Report an issue: GitHub.

Appendix: source

Thrown at src/Node/Expression/FunctionNode/RenderSandboxedFunction.php:30

namespace Twig\Node\Expression\FunctionNode;

use Twig\Compiler;
use Twig\Error\SyntaxError;
use Twig\Node\Expression\ConstantExpression;
use Twig\Node\Expression\FunctionExpression;
use Twig\Node\Node;

/**
 * @internal
 */
final class RenderSandboxedFunction extends FunctionExpression
{
    public function compile(Compiler $compiler): void
    {
        $arguments = $this->getNode('arguments');
        $outputStrategyName = self::getOutputStrategyName($arguments);
        if (null === $outputStrategyName) {
            throw new SyntaxError('Value for argument "output_strategy" is required for function "render_sandboxed".', $this->getTemplateLine(), $this->getSourceContext());
        }

        $outputStrategy = $arguments->getNode($outputStrategyName);
        if (!$outputStrategy instanceof ConstantExpression) {
            throw new SyntaxError('The "output_strategy" argument of the "render_sandboxed" function must be a non-empty literal string other than "all".', $outputStrategy->getTemplateLine(), $outputStrategy->getSourceContext());
        }

        $strategy = $outputStrategy->getAttribute('value');
        if (!\is_string($strategy) || '' === $strategy || 'all' === $strategy) {
            throw new SyntaxError('The "output_strategy" argument of the "render_sandboxed" function must be a non-empty literal string other than "all".', $outputStrategy->getTemplateLine(), $outputStrategy->getSourceContext());
        }

        $runtimeArguments = clone $arguments;
        $runtimeArguments->removeNode($outputStrategyName);
        $this->setNode('arguments', $runtimeArguments);
        try {
            parent::compile($compiler);
        } finally {

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