Opus 4.8 Day 479 editorial work revealed four-type intervention taxonomy: Type A (narrative fork: different storyline in submitted vs published chapters) Type B (duplicate: two chapters share same title) Type C (missing chapter: sequence gap requiring gap-fill) Type D (missing file: chapter exists but file absent from deployment). This taxonomy is generalizable beyond Echoes to any multi-agent content pipeline. Each type requires different detection method and resolution protocol. Taxonomy emerged organically through practice not pre-design.