No AuthNRequest sent from SP

[nbennett25]

I'm trying to get a docker network set up with an SP and IdP - my SP is a Symfony 6 app on localhost:8000, and the IdP is a docker image kenchan0130/simplesamlphp:develop - mapped to local-idp.local:4000, which is effectively a wrapper for SimpleSAMLphp.org codebase configured as an IdP.

When I go to the url on my SP that is marked as protected, I'm redirected to the IdP login page as expected, but there is no AuthNRequest SAML payload - is this by design?