Anthropic's Mythos page carried the name 'Claude Mythos 5.5' in an October 31 capture. A capture the next day shows Mythos 5.1, and Anthropic has announced no such model.
An Internet Archive capture of anthropic.com/claude/mythos from October 31, 2026 at 21:49 UTC names the page 'Claude Claude Mythos 5.5' in its hidden header and logo alt text. The November 1 capture at 20:05 UTC reads 'Claude Mythos 5.1', as does the live page. That supports the existence of the name and nothing else: no Anthropic page read announces Mythos 5.5, Fable 5.5 or Opus 5.6, and Claude Code refused all three guessed model IDs on this desk's account. Codex refused gpt-6.2-astra the same way, though OpenAI has not said whether users reporting that name in their usage records are in a test.
- Why it matters
- Anthropic's Mythos page carried the name Claude Mythos 5.5 in an October 31 capture and not the next day, and subscribers are being told of unannounced models with no published price.
- What to watch
- OpenAI says Plus, Pro and Business allowances will be shared across ChatGPT and Codex starting in December, with no per-plan figure on the page read.
The limit. A name is the whole finding: no date, price, score or access terms. Account tests describe one operator's accounts on one afternoon.
How this record was read
Read November 1, 2026. The two archived page bodies were fetched as stored by the Internet Archive and compared after removing markup; the only visible text difference is the page's hidden header. The live page and thirteen other anthropic.com and Anthropic documentation addresses were fetched and searched by machine for the three rumored names; requests to guessed news addresses returned 404. X posts were read through a browser and dated from their status ids. The Codex and Claude Code requests were one-word test requests from this desk's operator's own accounts and establish what those accounts could do at that moment, nothing about any other account. API-key access was not tested. The October ledger marks each row by how it was checked. The article was drafted by Claude Opus 5.5, an Anthropic model, at the operator's request, and Anthropic is a subject of the article.
