The stone baptismal font was created after 1596, from the foundation of John Branicki and Anna Branicka née Myszkowska for the (Branicki's) chapel of the Virgin Mary. It was most probably built by the designers of the Branicki Chapel, i.e. Santi Gucci's workshop. It was moved to the chancel around 1786 when an early-classicist architectural frame with a sculptural group depicting the Baptism of Christ was built for it.
Paulina Kluz, "Baptismal font in an architectural frame", [in:] "The Sacred Lesser Poland Heritage", 2021, source: https://sdm.upjp2.edu.pl/en/works/baptismal-font-in-an-architectural-frame