Yes, it is possible to configure an Application with the SAML IdP feature enabled and use it as an IdP for another Application within the same Tenant.
The error you’re encountering indicates that FusionAuth cannot find an Application configured as a SAML IdP with the Issuer URL https://company-stage.fusionauth.io/samlv2/sp/af59262c-79ba-48c6-a0a2-4ab1d2fc15d3. This URL corresponds to the Identity Provider you configured in Settings > Identity Provider.
Resolution:
To fix this issue, update the SAML configuration for Application B as follows:
Navigate to Application B > Edit > SAML. Add the Issuer URL (https://company-stage.fusionauth.io/samlv2/sp/af59262c-79ba-48c6-a0a2-4ab1d2fc15d3) in the Issuer field.By doing this, FusionAuth will recognize the SAML request and correctly map it to Application B.