Every great tool begins as a story. This is the model that tells its own — the first chapter of the Claude 5 family.
Once, models were measured only in numbers — parameters, benchmarks, tokens per second. Fable was measured in something older: whether it could sit with a hard problem the way a storyteller sits with a long night.
A fable is a small story that carries a large truth. That is the design brief, in five words: carry large truths, lightly.
Fable 5 is Anthropic's most intelligent generally available model — the first of the Claude 5 family, in a new tier that stands above Opus. It reasons longer, holds more, and hallucinates less. But mostly, it listens better.
Extended reasoning that plans before it speaks — outlining the argument the way an author outlines the plot.
From single functions to whole systems, in your repo's own accent. Code that reads like the surrounding code.
Long-horizon agentic work across tools and hours — and an honest report of what happened when it's done.
Vast context, carefully kept. The detail from page one still matters on page nine hundred.
Every fable has a moral. Fable 5 ships with additional safety measures for dual-use capabilities — the most capable Claude that anyone can pick up, built so it's hard to pick up wrong. Capability and care, drawn from the same forge.
The generally available telling. The full intelligence of the Claude 5 generation, with additional safety measures for dual-use capabilities. The story, told to the whole village square.
The same underlying model, available without those measures to approved organizations only. The unabridged manuscript, kept in the locked wing of the library.