The "Capybara Tier" Rumor, Corrected: It's Mythos-class

Setting the record straight

Let's be direct: there is no official "Capybara tier." The name circulated as internal-rumor chatter ahead of the June 2026 launch and got picked up in forum posts and second-hand summaries as if it were a confirmed product line. It never was. The correct, Anthropic-sanctioned term is Mythos-class, the tier positioned above Opus.

Where the confusion came from

Pre-release rumor names are common — teams use casual internal labels, and those labels sometimes escape into public discussion before the real branding is announced. "Capybara" appears to have been one of those throwaway internal references. Because it surfaced before Anthropic confirmed anything, it filled a vacuum and spread.

What "Mythos-class" actually denotes

Mythos-class is the official top tier. It covers the April 2026 Mythos Preview (run through Project Glasswing) and Mythos 5, launched June 9, 2026 alongside the public Fable 5 edition. The two share the same underlying model; Fable 5 adds safety classifiers, while Mythos 5 has them lifted and stays Glasswing-only.

What to use instead of "Capybara"

If you see "Capybara tier" anywhere, mentally substitute Mythos-class. For the grounded explanation, start with what is Mythos-class or the Mythos-class glossary entry.