CLAIM-2026-09-03-06

On Terminal-Bench 4.0 (agentic coding), Anthropic publishes 55.8% for Fable 5.1 and 60.9% for Mythos 5.1 - a 5.1-point spread between two configurations of one model.

Why it matters

The spread sits on ordinary agentic coding rather than on cyber work, so the safeguard tier is now a measurable performance variable in normal engineering.

Sources

• anthropic2026introduci