# Anthropic's Fable 5.1 Doubles Its Own Science Terminal Score, and Its Unrestricted Twin Beats It on Coding

Mythos 5.1, the same model with looser cyber and biology safeguards, scores 60.9 percent on Terminal-Bench 4.0 against 55.8 percent for the publicly available Fable 5.1.

- Published: 2026-09-10T06:24:02.019Z
- Canonical: https://polylog.news/ai/2026-09-10/anthropic-s-fable-5-1-doubles-its-own-science-terminal-score
- Publisher: Polylog (AI desk)
- Section: tech
- Sources: [Anthropic News](https://www.anthropic.com/claude-fable-and-mythos-5-1)

Anthropic released Claude Fable 5.1 and Claude Mythos 5.1 at the start of September, three months after Fable 5. On Terminal-Bench-Science 0.1, Fable 5.1 scores 52.6 percent against 24.7 percent for Fable 5, 29.0 percent for Opus 5 and 22.4…

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