Anthropic — Introducing Claude Fable 5
Anthropic — Introducing Claude Fable 5.1
Alex Finn — Claude Fable 5 just dropped and I'm speechless...
Greg Isenberg — Claude Fable 5 is BANNED. What to do?
2026-09-01 — Tuesday
Anthropic released Claude Fable 5.1 yesterday alongside Claude Mythos 5.1. The two are the same underlying model with different safety filters: Fable 5.1 is generally available, while Mythos 5.1 is restricted to trusted-access programs for cybersecurity and life-sciences work.
The gains over Fable 5 are concentrated in agentic and scientific work — multi-step command-line tasks and research workflows — rather than spread evenly:
Anthropic also says Fable 5.1 reaches similar or better results than Fable 5 at lower effort levels, which is the more useful claim for anyone paying by the token.
Base rates do not move: $10 per million input tokens, $50 per million output. What changed is underneath — cache reads now cost 75% less, cutting typical workloads by roughly 25% and highly agentic workloads by up to 45%.
That is a meaningful shift in how the frontier tier is priced. For a long-running agent that re-reads the same context on every turn, the cache read is most of the bill, so a discount there lands harder than a headline rate cut would.
Fable 5.1 carries a 1M-token context window and 128K maximum output. It stays outside Pro plans and standard Team seats, which need pay-as-you-go credits; Max and premium tiers get it as part of their allocation, up to 50% of weekly limits.
With this release the Claude 5 family is complete across four tiers in under three months — Fable 5 and Mythos 5 on 9 June, Sonnet 5 on 30 June, Opus 5 on 24 July, and now the 5.1 refresh. Worth noting for anyone searching for it: there is no model called simply “Claude 5.0”. Anthropic went from the 4.x line straight to these named models.
Anthropic — Introducing Claude Fable 5
Anthropic — Introducing Claude Fable 5.1
Alex Finn — Claude Fable 5 just dropped and I'm speechless...
Greg Isenberg — Claude Fable 5 is BANNED. What to do?
Every — We Tested Anthropic’s Fable 5 for a Week
BridgeMind — Vibe Coding With Claude Fable 5.1
BridgeMind — Vibe Coding With Claude Fable 5
Claude — Claude Fable 5.1 runs the forecast overnight
Matthew Berman — Anthropic went CRAZY (Mythos/Fable 5.1)
Alex Finn — CLAUDE FABLE 5 BANNED. IT ACTUALLY HAPPENED...
Nate Herk | AI Automation — Fable 5.1 Just Dropped. It Looks Unreal.
Agentic Amit — Claude Fable 5 in 50 seconds
AsapGuide — I Tested Claude Fable 5 Against Opus So You Don't Have to WASTE Your Credits
Claude — Claude Fable 5.1 builds the ops review in Slack
Developers Digest — Claude Fable 5 in 7 Minutes
Anthropic — Meet Claude Fable 5.1
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