# Anthropic cuts Claude Fable 5.1 cache read costs by 75%

Digest AI · Generative AI & Models · published 2026-09-20T06:29:00Z

Canonical: https://digestai.news/story/anthropic-cuts-claude-fable-5-1-cache-read-costs-by-75

## Summary

Anthropic announced the release of Claude Fable 5.1 and Claude Mythos 5.1 on September 1, 2026. While the two models share the same underlying architecture, Mythos 5.1 is restricted to trusted organizations in high-risk fields like cybersecurity and life sciences, whereas Fable 5.1 is available to the general public. The most significant change is a 75% reduction in the cost of "cache reading," a feature that allows the AI to reuse previously processed context at a lower rate. This adjustment is expected to lower total costs for long-duration tasks, such as complex coding workflows, by up to 45%, while base input and output rates remain unchanged from the previous Fable 5 version.

According to Anthropic, the new models show improved performance in long-running tasks and autonomous tool usage. Benchmarks indicate that Fable 5.1 outperforms the previous Fable 5, Anthropic's own Opus 5, and OpenAI's GPT-5.6 Sol in automated software development and agentic tasks. The company also claims the model has a stronger tendency to address root causes of issues rather than applying superficial patches, which may reduce errors in complex, autonomous workflows.

This pricing strategy aligns with broader industry trends where competition drives down costs for high-volume usage. For users relying on Claude for bulk coding or long-context interactions, the update offers immediate cost savings without requiring any changes to their setup, as the models update automatically.

## Key points

- Anthropic reduced cache read rates for Claude Fable 5.1 by 75%.
- Long-duration coding task costs are expected to drop by up to 45%.
- Fable 5.1 outperforms Opus 5 and GPT-5.6 Sol in agentic benchmarks.

## Why it matters

The significant drop in cache costs makes long-context and autonomous AI tasks more affordable, potentially accelerating the adoption of AI for complex, multi-step workflows in software development and enterprise operations.

## Sources

1. [Claude actually lowered its prices. What changed in Fable 5.1?](https://note.com/sho_ai_info/n/n76d8acdb4e61?hl=en) (note.com, 2026-09-20)

Part of the developing story: [Claude Fable 5 Enterprise Adoption and Competitive Benchmarking](https://digestai.news/thread/claude-fable-5-1-shows-longer-less-hedged-responses-than-fable-5) (4 stories)

## Cite

Digest AI, "Anthropic cuts Claude Fable 5.1 cache read costs by 75%", 20 September 2026, https://digestai.news/story/anthropic-cuts-claude-fable-5-1-cache-read-costs-by-75

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