SAML2.0 Azure AD B2C using redirect when I need it to use POST

To add a bit more detail. The IdP metadata shows both a redirect and a POST as possible bindings. I need my ADB2C to use the HTTP-POST option but it is picking redirect because it is defined first in the config.

@Joe White
From your Q&A post the technical profile is not there can you share in the comment section.

However, based on the information you shared, it might be the metadata single sign-on service with two bindings. The HTTP-Redirect takes precedence over the HTTP-POST because it appears first in the SAML identity provider metadata.

<IDPSSODescriptor protocolSupportEnumeration="urn:oasis:names:tc:SAML:2.0:protocol">
  ...
  <SingleSignOnService Binding="urn:oasis:names:tc:SAML:2.0:bindings:HTTP-Redirect" Location="https://login.microsoftonline.com/00000000-0000-0000-0000-000000000000/saml2"/>
  <SingleSignOnService Binding="urn:oasis:names:tc:SAML:2.0:bindings:HTTP-POST" Location="https://login.microsoftonline.com/00000000-0000-0000-0000-000000000000/saml2"/>
</IDPSSODescriptor>

With in your technical profile try to change the precedence to HTTP-POST and see it can fix your issue.
when you configure SAML protocol bindings the SAML requests are sent to the identity provider as specified in the identity provider's metadata SingleSignOnService element. Most of the identity providers' authorization requests are carried directly in the URL query string of an HTTP GET request.
Kindly refer to your identity provider documentation for how to configure the bindings for both SAML requests.

Unfortunately that metadata belongs to the owner of the IdP so I can't directly change or remove one of the Bindings. I've asked them to do so but haven't heard back yet. My hope was that there would be a way to tell the SAML config on the technical profile to select the HTTP-POST option explicitly.

@Joe White
Can you try to modify the TrustFrameworkExtensions.xml technical profile and see it can help.