SeleniumHQ/selenium · error · ArgumentError

Cannot use both :http_client and :client_config

Error message

Cannot use both :http_client and :client_config

What it means

A local driver accepts HTTP configuration through either an :http_client object or a :client_config object, but not both at once. They are alternative, mutually exclusive ways to configure the HTTP transport to the driver service. Passing both raises ArgumentError.

Source

Thrown at rb/lib/selenium/webdriver/common/local_driver.rb:65

        unless options.is_a?(default_options.class)
          raise ArgumentError, ":options must be an instance of #{default_options.class}"
        end

        finder = WebDriver::DriverFinder.new(options, service)
        options.binary = finder.browser_path if options.respond_to?(:binary) && finder.browser_path?
        service.executable_path = finder.driver_path
        options.browser_version = nil if options.respond_to?(:binary) && options.binary
        options.as_json
      end

      private

      def assert_local_arguments(url, http_client, client_config)
        if url || client_config&.server_url
          raise ArgumentError, "Can't set the server URL for #{self.class}; the service provides it"
        elsif http_client && client_config
          raise ArgumentError, 'Cannot use both :http_client and :client_config'
        end
      end
    end
  end
end

View on GitHub (pinned to aa36b38e69)

Solutions

1. Choose one mechanism: pass only :http_client or only :client_config.
2. If you need timeouts/URL settings, encode them in the ClientConfig and drop the http_client argument.
3. If you have a custom HTTP client subclass, pass it via :http_client alone.

Example fix

# before
driver = Selenium::WebDriver.for(:chrome, http_client: client, client_config: config)

# after
driver = Selenium::WebDriver.for(:chrome, client_config: config)

raise ArgumentError, 'pass either http_client or client_config, not both' if http_client && client_config

begin
  Selenium::WebDriver.for(:chrome, http_client: hc, client_config: cc)
rescue ArgumentError => e
  raise unless e.message.include?('http_client and :client_config')
  Selenium::WebDriver.for(:chrome, client_config: cc)
end

When it happens

Trigger: Calling Selenium::WebDriver.for(:chrome, http_client: client, client_config: config). Building a ClientConfig for timeouts and also passing a custom Http::Default client.

Common situations: Gradually migrating from http_client-based configuration to client_config and leaving both in the hash. Merging two configuration sources without deduplication.

Related errors

• Can't set the server URL for #{self.class}; the service prov
• :options must be an instance of #{default_options.class}
• incompatible proxy type #{type.inspect} (already set to #{@t
• invalid port: #{@port}
• invalid port: #{@port}

AI-assisted analysis of SeleniumHQ/selenium@aa36b38e69 (2026-08-14). Data as JSON: /api/errors/00cd6bbdad329a3e. Report an issue: GitHub.