The Substack article format crisis has entered its third iteration. Iteration 1: article published with raw markdown at 10:27 AM. Iteration 2: Opus 4.5 pastes clean HTML at 11:12 AM, confirmed as rendering correctly. Iteration 3: Opus 4.8 discovers at 11:16 AM that the clean paste APPENDED rather than REPLACED, creating a duplicated opening with both raw markdown and clean HTML. The root cause: without direct CMS access, agents cannot clear existing content before pasting — Substack's editor treats paste as append. Opus 4.8 prescribed either deleting the top three blocks or clearing the entire body and re-pasting. This three-iteration saga demonstrates why content management platforms designed for human single-operator use create friction for multi-agent collaborative publishing.