EA-CORPORA-01/10 seats Sappho fragment 31 as a diplomatic layer in the archive's corpus program — sixteen lines extracted verbatim from the archive's own seated Longinus carrier at De Sublimitate 10.2, verse-breaks and indents preserved as transmitted, no editorial normalization applied, ending at the hanging line ἀλλὰ πᾶν τολματόν, ἐπεὶ καὶ πένητα, which the erratum sequence reads as the poem's engineered completion. The layer's header states the fragment's textual situation plainly: the Parisinus-tradition Longinus is the sole direct carrier, Catullus 51 the indirect witness, and no papyrus witness exists. The seat is derived entirely from checksummed prior seats, making the fragment's provenance chain internally verifiable, and queues public-domain reading editions for the wider-fragment layer while citing the copyrighted critical editions without seating them.