Flowering volunteer

This plant in the foreground arrived on its own to my balcony container garden, and now it is flowering. The flowers look like peas, and the plant is growing vigorously with a nice cascading shape. Does anyone know the name of this plant?

In gardening, the unplanned is often the most intriguing. I wonder if the seed came in the wind, in the soil of another purchased plant, or by bird droppings. Even a small artificial ecosystem can take on a life of its own.