symfony/routing · error · RuntimeException

The container parameter

Error message

The container parameter "%s" resolves to an env var, which is not allowed in routing configuration.

What it means

After fetching a container parameter for a route value, the Router checks whether the resolved value itself is (or resolves through) an env var, detected by the internal env_... processor marker pattern. This error means a parameter used in routing indirectly resolves to an env var, which is forbidden because routing is compiled without runtime env access.

Solutions

1. Remove the env indirection: give the parameter a static value in routing context.
2. Bind the env var to a concrete default via %env(default:...)%% only where runtime resolution is allowed — but not for routing values.
3. Pass the value as a route default at runtime instead of relying on container compilation.

Example fix

// before (parameters.yaml)
app_host: '%env(APP_HOST)%'
// after
app_host: 'example.com'  # or resolve env outside routing

$v = $container->getParameter($name);
if (is_string($v) && preg_match('/env_[a-f0-9]{16}_\w+_[a-f0-9]{32}/Ui', $v)) {
    throw new LogicException("Parameter $name resolves to an env var; not usable in routing.");
}

function isRoutingSafeParam(mixed $v): bool { return !is_string($v) || !preg_match('/env_[a-f0-9]{16}_\w+_[a-f0-9]{32}/Ui', $v); }

try { $url = $generator->generate($name); } catch (RuntimeException $e) { // param resolves to env var
    $logger->error($e->getMessage());
}

When it happens

Trigger: A route references %param% where the parameter's value contains or equals a processed env placeholder (matching /env_[a-f0-9]{16}_\w+_[a-f0-9]{32}/).

Common situations: Chained parameters where parameters.yaml defines foo: '%env(BAR)%' and a route uses %foo%; indirection through imported config files.

Understand the failure class

Background: "Invalid value" and "allowed values are" config errors: what your library rejected and how to fix it — this error's family across 41 libraries.

Related errors

• Using "%% %%" is not allowed in routing configuration.
• The container parameter
• Unable to generate a URL for the named route
• Target route " " for alias " " does not exist.
• Unable to generate a URL for the named route

AI-assisted analysis of symfony/routing@83fa223250 (2026-09-14). Data as JSON: /api/errors/2c03a47b6b1dbb27. Report an issue: GitHub.

Appendix: source

Thrown at DependencyInjection/Router.php:181

        if (!\is_string($value)) {
            return $value;
        }

        $escapedValue = preg_replace_callback('/%%|%([^%\s]++)%/', function ($match) use ($value) {
            // skip %%
            if (!isset($match[1])) {
                return '%%';
            }

            if (preg_match('/^env\((?:\w++:)*+\w++\)$/', $match[1])) {
                throw new RuntimeException(\sprintf('Using "%%%s%%" is not allowed in routing configuration.', $match[1]));
            }

            $resolved = ($this->paramFetcher)($match[1]);

            if (\is_string($resolved) && preg_match('/env_[a-f0-9]{16}_\w+_[a-f0-9]{32}/Ui', $resolved)) {
                throw new RuntimeException(\sprintf('The container parameter "%s" resolves to an env var, which is not allowed in routing configuration.', $match[1]));
            }

            if (\is_scalar($resolved)) {
                $this->collectedParameters[$match[1]] = $resolved;

                if (\is_string($resolved)) {
                    $resolved = $this->resolve($resolved);
                }

                if (\is_scalar($resolved)) {
                    return false === $resolved ? '0' : (string) $resolved;
                }
            }

            throw new RuntimeException(\sprintf('The container parameter "%s", used in the route configuration value "%s", must be a string or numeric, but it is of type "%s".', $match[1], $value, get_debug_type($resolved)));
        }, $value);

        return str_replace('%%', '%', $escapedValue);

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