A generated clinical letter, with its authorship drawn above every sentence. Scrub the timeline and watch it being written, edited and signed, by two different hands.
A provenance label usually says one thing about a whole document: generated, assisted, or reviewed. That is a single bit standing in for a process with many hands in it. The strands here are the alternative: one bar per sentence, showing who held the pen and for how long.
Two things become visible that a label cannot show. First, some sentences were never touched, and they are not the trivial ones. Second, two safety sentences were written entirely by a human after the model had finished, which means a provenance label reading "AI-generated" would be wrong about the most important part of the letter.
Drag the timeline back to zero and the letter almost assembles itself. That is the point a reader is being asked to trust: not that a model wrote it, but that a person was in the loop, and where.