symfony/routing · error · InvalidArgumentException

Route pattern " " cannot contain " " as a path parameter.

Error message

Route pattern "%s" cannot contain "%s" as a path parameter.

What it means

RouteCompiler throws this when a route path contains a variable named "_fragment" or "_firewall". Both are reserved names: "_fragment" selects the fragment renderer and "_firewall" selects the firewall handling the route; allowing them as path parameters would let the request URL choose them. compile() raises an InvalidArgumentException as soon as such a path variable is found.

Solutions

1. Rename the path variable to a non-reserved name, e.g. /{section}/dashboard instead of /{_firewall}/dashboard.
2. Remove the variable if it was added by mistake and pass the value via defaults or controller arguments instead.
3. Search route config files for "_fragment" and "_firewall" used as {placeholders}.

Example fix

// before
$route->setPath('/{_firewall}/dashboard');

// after
$route->setPath('/{area}/dashboard');

$reserved = ['_fragment', '_firewall'];
foreach ($reserved as $name) {
    if (preg_match('#\{'.preg_quote($name, '#').'\}#', $route->getPath())) {
        throw new \InvalidArgumentException("Path must not contain reserved {{$name}} parameter.");
    }
}

try {
    (new RouteCompiler())->compile($route);
} catch (\InvalidArgumentException $e) {
    // log and skip/fail fast for the offending route definition
}

When it happens

Trigger: Compiling a route whose path contains {_fragment} or {_firewall}, e.g. ->setPath('/{_firewall}/dashboard') or a YAML route path '/{_fragment}/foo'.

Common situations: Typos or misunderstandings of Symfony's reserved route attributes; copying _controller-style underscore naming conventions to arbitrary parameter names; dynamically generated route paths that include reserved keys.

Understand the failure class

Background: "Must be a positive integer", "Invalid value", "Unsupported": the invalid-argument-value error family, when a library rejects the value you pass — this error's family across 35 libraries.

Related errors

• Route host " " cannot contain " " as a host parameter.
• Parameter " " for route " " must match " " (" " given) to…
• Parameters for route
• Route aliases cannot be used on non-invokable class
• The " ()" method must not be called.

AI-assisted analysis of symfony/routing@83fa223250 (2026-09-14). Data as JSON: /api/errors/20440c5f9dfdbdc4. Report an issue: GitHub.

Appendix: source

Thrown at RouteCompiler.php:86

        if (null !== $locale && null !== $route->getDefault('_canonical_route') && preg_quote($locale) === $route->getRequirement('_locale')) {
            $requirements = $route->getRequirements();
            unset($requirements['_locale']);
            $route->setRequirements($requirements);
            $route->setPath(str_replace('{_locale}', $locale, $route->getPath()));
        }

        $path = $route->getPath();

        $result = self::compilePattern($route, $path, false);

        $staticPrefix = $result['staticPrefix'];

        $pathVariables = $result['variables'];

        foreach ($pathVariables as $pathParam) {
            // "_firewall" selects the firewall handling the route; as a path parameter it would let the URL choose it
            if ('_fragment' === $pathParam || '_firewall' === $pathParam) {
                throw new \InvalidArgumentException(\sprintf('Route pattern "%s" cannot contain "%s" as a path parameter.', $route->getPath(), $pathParam));
            }
        }

        $variables = array_merge($variables, $pathVariables);

        $tokens = $result['tokens'];
        $regex = $result['regex'];

        return new CompiledRoute(
            $staticPrefix,
            $regex,
            $tokens,
            $pathVariables,
            $hostRegex,
            $hostTokens,
            $hostVariables,
            array_unique($variables)
        );

View on GitHub (pinned to 83fa223250)