All cladograms are a work in progress.
Most chordate biologists link the two protochordate subphyla, Urochordata and Cephalochordata, as sister groups. I have chosen to link amphioxus more closely with hagfishes. The Urochordates are so derived, it is difficult to know where to place them, and I have stuck them on between Hemichordata and Cephalochordata without, frankly, much conviction they belong at that place. My placement of cephalochordates closely linked to hags is drawn with confidence. Please keep in mind that this comparison only involves four taxa.