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Discover how Anthropic's Claude Fable 5.1 and Anthropic's Claude Opus 5 stack up against each other in this comprehensive comparison of two leading AI language models. Released in September 2026 and July 2026 respectively, these models represent significant advancements in artificial intelligence, with Claude Fable 5.1 offering a 1,000,000-token context window and Claude Opus 5 offering a 1,000,000-token context window.

Explore their capabilities, pricing, and performance metrics, with Claude Fable 5.1 achieving 1,498 on LMArena Elo and Claude Opus 5 scoring 1,493, making this comparison essential for developers and organizations seeking the right AI solution for their specific needs.

Models Overview

	Claude Fable 5.1	Claude Opus 5
Provider The company that provides the model.	Anthropic	Anthropic
Context Length Maximum number of tokens the model can process	1M	1M
Maximum Output Maximum number of tokens the model can generate in one response	128K	128K
Release Date When the model was first released.	01-09-2026	24-07-2026
Knowledge Cutoff When the model's training data ends.	2026-06	2026-05
Open Source Whether the model weights are openly available.	FALSE	FALSE

Pricing Comparison

Compare the pricing of Anthropic's Claude Fable 5.1 and Anthropic's Claude Opus 5 to determine the most cost-effective solution for your AI needs. Prices are the standard API tier per million tokens, as published by each provider as of September 2026.

	Claude Fable 5.1	Claude Opus 5
Input Cost Cost per million input tokens	$10 / 1M tokens	$5 / 1M tokens
Output Cost Cost per million tokens generated	$50 / 1M tokens	$25 / 1M tokens

Comparing Benchmarks and Performance

Compare the performances of Anthropic's Claude Fable 5.1 and Anthropic's Claude Opus 5 on industry benchmarks. Scores are the ones the providers and public leaderboards report; a benchmark neither reports is left out.

	Claude Fable 5.1	Claude Opus 5
LMArena Elo Crowd-sourced blind preference rating on the LMArena text leaderboard.	1,498	1,493
Humanity's Last Exam Expert-written questions at the frontier of human knowledge.	Benchmark not available	56.3%

Sources — Claude Fable 5.1: platform.claude.com, arena.ai; Claude Opus 5: platform.claude.com, arena.ai, anthropic.com.