2026-09-02 / Signal #1
Anthropic Split One Model Into Public Fable and Restricted Mythos
“They trained one model, then sold the censored version cheaper and locked the real one behind a trusted-access gate.”
The Story
Anthropic launched Claude Fable 5.1 (generally available) and Claude Mythos 5.1 (same underlying model, restricted trusted-access for cybersecurity and life sciences). Fable is cheaper—roughly 25% less on typical work, up to 45% on long agentic tasks—with improved safeguards and enterprise privacy options. Early testers report it staying coherent on multi-day unattended coding and research.
Why It Matters
One intelligence, two doors: the “fable” version for everyone and the “mythos” version with dangerous capabilities left on. Builders get cheaper overnight agents; the strange part is policy turning the same weights into public vs. restricted personalities.
Evidence
Anthropic official announcement (Sept 1, 2026)
Sources
Daily scan: 2026-09-02