What determines the inner edge of the Habitable Zone according to planetary physics models?

The point where a runaway greenhouse effect would occur

The inner edge of the Habitable Zone is defined by the threshold where stellar radiation becomes so intense that it triggers a catastrophic environmental collapse leading to the permanent loss of surface water. This process begins when stellar energy vaporizes surface water, creating a dense steam atmosphere. This steam, being a potent greenhouse gas, traps more heat, causing temperatures to rise further, which in turn vaporizes more water. This positive feedback loop, known as a runaway greenhouse effect, escalates until the planet loses its essential water component entirely, a fate believed to have befallen Venus due to its proximity to the Sun.