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Specifications
Context window
1M—
API pricing
Input price
$10.00—
Output price
$50.00—
Cached input price
$0.25—
Cheapest input
$10.00Amazon Bedrock—
Cheapest output
$50.00Amazon Bedrock—
Benchmarks
BullshitBench v2
77%19%
Overview
CompanyAnthropicSpaceXAI
Release dateSep 1 2026Nov 19 2025
AccessClosedClosed
Model detailsView modelView model

Frequently asked questions

Claude Fable 5.1 leads Grok 4.1 Fast on 1 of the 1 benchmark they both report (BullshitBench v2). Only Claude Fable 5.1 has a verified first-party API price: $10.00 per million input tokens and $50.00 per million output tokens. No pay-as-you-go API rate is tracked for Grok 4.1 Fast. Grok 4.1 Fast shipped 286 days before Claude Fable 5.1, so benchmark comparisons should account for the intervening progress.

Published specifications for these two models are limited — see each model page for the latest details.

On BullshitBench v2, Claude Fable 5.1 leads at 77% vs Grok 4.1 Fast at 19%.