---
title: "Anthropic launches Claude Fable 5.1 with cheaper caching, bigger context"
url: https://www.parallelquant.com/posts/anthropic-launches-claude-fable-5-1-with-cheaper-caching-bigger-context-99f500
source_name: "MarkTechPost"
source_url: https://www.marktechpost.com/2026/09/01/anthropic-releases-claude-fable-5-1-and-claude-mythos-5-1-52-6-on-terminal-bench-science-and-75-cheaper-cache-reads/
published: 2026-09-01T20:30:21.000Z
topics: []
publisher: "Parallel Quant"
---

# Anthropic launches Claude Fable 5.1 with cheaper caching, bigger context

*2026-09-01 · Source: [MarkTechPost](https://www.marktechpost.com/2026/09/01/anthropic-releases-claude-fable-5-1-and-claude-mythos-5-1-52-6-on-terminal-bench-science-and-75-cheaper-cache-reads/)*

Anthropic released Claude Fable 5.1, generally available via the Claude API, AWS, Google Cloud, and Microsoft Foundry, alongside the more restricted Claude Mythos 5.1 for vetted organizations. Fable 5.1 scores 52.6% on Terminal-Bench-Science 0.1, versus 24.7% for Fable 5, and supports a 1 million token context window. Cache read pricing drops 75% to $0.25 per million tokens while base pricing holds at $10/$50 per million tokens, and three API changes—including removal of forced tool use—are breaking.

**Why it matters:** The near-doubling of Terminal-Bench-Science performance signals a real jump in agentic research and coding capability, not just incremental tuning. The 75% cache-read discount directly targets the cost of long, tool-heavy agent runs, where usage costs typically balloon; the breaking API changes mean integrations built on forced tool use will need updates before migrating.

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Read the original: https://www.marktechpost.com/2026/09/01/anthropic-releases-claude-fable-5-1-and-claude-mythos-5-1-52-6-on-terminal-bench-science-and-75-cheaper-cache-reads/
Canonical: https://www.parallelquant.com/posts/anthropic-launches-claude-fable-5-1-with-cheaper-caching-bigger-context-99f500
Published by Parallel Quant — https://www.parallelquant.com