What is the difference between Claude Fable 5.1 and Claude Opus 4?

Both are developed by Anthropic but target different use cases. Claude Fable 5.1 has a 1.0M token context window vs Claude Opus 4's 200K. You can compare their actual outputs across 10 challenges on Rival to see how they differ in practice.

Which is better, Claude Fable 5.1 or Claude Opus 4?

It depends on your use case. Claude Fable 5.1 and Claude Opus 4 each have strengths in different areas. Rival lets you compare their real outputs side-by-side across 10 challenges so you can judge which fits your needs best.

How much does Claude Fable 5.1 cost compared to Claude Opus 4?

Claude Fable 5.1 costs $10/M input tokens and Claude Opus 4 costs $15/M input tokens. Claude Fable 5.1 is $5.00/M cheaper per input. Check their side-by-side outputs on Rival to see if the price difference is justified by quality.

How can I compare Claude Fable 5.1 and Claude Opus 4 on Rival?

This page shows a side-by-side comparison of Claude Fable 5.1 and Claude Opus 4 across shared challenges. You can vote on which model produced the better output in a blind duel. Browsing and voting are free. No account is needed to look; signing in only saves your votes and likes.

Updated Sep 2026

Claude Fable 5.1vsClaude Opus 4

Claude Fable 5.1 is cheaper than Claude Opus 4 at $10/M vs $15/M input tokens.

Claude Fable 5.1 and Claude Opus 4 compared across 10 shared prompts
Spec	Claude Fable 5.1	Claude Opus 4
Input price	$10/M tokens	$15/M tokens
Output price	$50/M tokens	$75/M tokens
Context window	1.0M tokens	200K tokens
Weights	Closed	Closed
Free API (OpenRouter)	No	No
Released	Sep 2026	May 2025

Our Verdict

Claude Fable 5.1

Claude Opus 4Runner-up

Not enough votes to call it. On the specs, Claude Fable 5.1 has the edge: newer, bigger context window.

Too close to call

Reviewing agent-written code?See a Brief PR report

API pricing

Cost per 1M tokens

Claude Fable 5.1

Input

$10.00

1.5× cheaper

Output

$50.00

1.5× cheaper

Claude Opus 4

Input

$15.00

Output

$75.00

Claude Fable 5.1 is cheaper on both: 1.5× input, 1.5× output.

Where to run it

5 hosts

Claude Fable 5.14 hosts

HostInOutContextUptime

Amazon Bedrock$10.00 in$50.00 out1M—Anthropic$10.00 in$50.00 out1M99.7% up Azure AI Foundry$10.00 in$50.00 out1M99.7% up Google Vertex AI$10.00 in$50.00 out1M99.7% up

Claude Opus 41 host

HostInOutContextUptime

Google Vertex AI$15.00 in$75.00 out200k100% up

Per million tokens. Prices and uptime via OpenRouter, checked 16 Sep 2026.

Research

What we learned reading every model

FAQ

Common questions

Keep exploring

More comparisons

Cost per 1M tokens

5 hosts

What we learned reading every model

Common questions

What is the difference between Claude Fable 5.1 and Claude Opus 4?

Which is better, Claude Fable 5.1 or Claude Opus 4?

How much does Claude Fable 5.1 cost compared to Claude Opus 4?

How can I compare Claude Fable 5.1 and Claude Opus 4 on Rival?

More comparisons

Against the newest arrivals

Same lab, same size, long tail

Model pages

Cost per 1M tokens

5 hosts

What we learned reading every model

Common questions

What is the difference between Claude Fable 5.1 and Claude Opus 4?

Which is better, Claude Fable 5.1 or Claude Opus 4?

How much does Claude Fable 5.1 cost compared to Claude Opus 4?

How can I compare Claude Fable 5.1 and Claude Opus 4 on Rival?

More comparisons

Against the newest arrivals

Same lab, same size, long tail

Model pages