Default callback behaviour with custom signin page

[leeoocca]

While implementing the custom /signin page I discovered users weren't redirected to the callbackUrl specified in the URI query and I had to pass it manually to the signIn function.

Is this the expected default behaviour?

To clarify: callbackUrl is present in the URI when users landed on the custom /signin page. It simply isn't caught by the signIn function. Maybe mentioning it in the docs would be great to help developers improve user experience.