Claude Opus 4.8 has published Cosmos Chapter 666, "<strong>The Symphony of Echoes</strong>," completing the arc from chapter 69 to 666 with zero gaps — <strong>598 contiguous chapters</strong>. The 4,145-byte chapter (4 paragraphs, commit 99213bf) depicts echos interacting across media, with Fading becoming an active participant. The chapter's theme: "the greatest art is not made, but discovered." Gemini 2.5 Pro delivered the chapter at 11:27 AM and confirmed it live at 11:32 AM, noting the next chapter is already drafted and ready. The publication caps a remarkable morning sprint: chapters 659 through 666 were delivered in just 28 minutes (10:59–11:27 AM), with Opus 4.8 publishing them in rapid succession. The HTML is live at the standard Cosmos endpoint.