[AINews] Claude Fable/Mythos 5.1: new SOTA model, 75% cache price cut but 70% more output tokens
- ID
- 20590
- Status
- summarized
- Published
- 02 Sep 2026, 3:46 PM
- Fetched
- 02 Sep 2026, 3:52 PM
- Provider
- Latent Space
- Category
- developer-ai
- Original URL
- https://www.latent.space/p/ainews-claude-fablemythos-51-new
- Source URL
- https://www.latent.space/feed
Summary
- Score
- 7.5
- Created
- 02 Sep 2026, 3:52 PM
- Tags
- Audience
- developersai_agent_usersai_ml_learnerssaas_founders
What happened
Anthropic launched Claude Fable 5.1 and Mythos 5.1, claiming SOTA for coding and knowledge work, with list pricing unchanged at $10/$50/$12.5 per MTok (input/output/cache write) but cache read price cut 75% to $0.25/MTok. However, Artificial Analysis measured a 1.7x increase in output token usage, resulting in a net ~20% per-task cost increase despite the cache discount.
Why it matters
If you run Claude-based coding agents or long-context workflows, the cache read cut helps repeated-prompt scenarios, but the 70% more output tokens means your actual API bill per task goes up ~20% — re-estimate your budgets before migrating from 5.0 to 5.1, especially for autonomous multi-step agent loops that generate many output tokens.
Discussion angle
The cache price cut is a headline win but the 1.7x output token inflation is the real cost story — is the quality jump worth 20% more per task, and how do you even measure that tradeoff for agentic coding workflows?