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NerdLevelTech

Anthropic

Claude Fable 5.1

Premium reasoning when Opus is not enough

ProprietaryReleased: September 1, 2026Deep reasoningVerified: October 24, 2026

What it is

Anthropic’s most demanding-work model: adaptive thinking always on, a 1M-token context window with output capped at 128K, positioned for long-horizon agentic work where Opus at higher effort still falls short.

NLT take

A specialist, not a default. At $10/$50 it only pays off when the task is a long reasoning chain where a wrong answer costs more than the tokens.

Before you switch

Two and a half times Opus’s price for the same 1M context. Benchmark it on your own task before switching a production loop to it.

Cost for a real task

The same task on every model: 50,000 input tokens and 10,000 output tokens, at the base tier.

Task cost

$1.00

50K input + 10K output tokens

Input, per 1M
$10.00
Output, per 1M
$50.00
Cached input, per 1M
$0.25

Pricing source: Anthropic pricing

Specs

Maker
Anthropic
Licence
Proprietary
Released
September 1, 2026
Context window
1,000,000 tokens
Max output
128,000 tokens
Knowledge cutoff
June 2026
Input / output
Text · Image → Text

Input and output tokens both count toward the 1M window; output is capped at 128K.

Watch it in action

Hands-on videos from creators we trust. They open on YouTube; we do not host or re-upload them.

From our coverage

Articles about this model or its family. A “Background” tag means we have not covered this exact release yet.

Sources & model links

Every number on this card traces back to one of these links. The maker page proves the positioning, the pricing page proves the rates, the Hugging Face repo proves the weights exist, and the Ollama page proves a local tag.

Official