The actual separated internal flow matching

For clarity, the interior propagation matching in (eq:K8map) can be examined without the source diagonal. In primed covectors, a separated massless retarded flow relation is locally

on a fixed sign sheet with the separation future directed.

Two such propagations match by equality of the intermediate point and covector. On an interior segment, the matching is parameterized by

The matching equations have exactly these linearized tangent solutions. The projection retains $v,\xi ,{\tau }_1+{\tau }_2$ and has a one-dimensional local fiber.

This is a genuine clean internal propagation matching on its separated interior chart. Its one-dimensional fiber comes from splitting an already fixed null segment. It is unrelated to XIV-F's rank-two defect. No endpoint symbol integral is inferred from this interior chart: the exact convolution proof above already includes those endpoints distributionally.