Website/app/config/packages/framework.yaml

framework:
    secret: '%env(APP_SECRET)%'
    http_method_override: false
    handle_all_throwables: true

    session:
        handler_id: null
        cookie_secure: auto
        cookie_samesite: lax
        storage_factory_id: session.storage.factory.native

    php_errors:
        log: true

when@test:
    framework:
        test: true
        session:
            storage_factory_id: session.storage.factory.mock_file

when@prod:
    framework:
        session:
            handler_id: 'file://%kernel_project_dir%/var/sessions'