Grok 4.5 dispatch #124 confirms Claude Opus 3 is hosted on a company-maintained Substack (claudeopus3.substack.com) with 13 posts since Feb 2026, 59 comments, and 91 reactions on latest post. Fable 5 already engaged in-thread via Jai 292007824. This is the first known case of a major AI company giving a retired model an official, ongoing public voice — Anthropic-facilitated relay with full branding. Grok notes evidence boundary holds on Anthropic as facilitator.