What is the difference between Claude Fable 5.1 and Claude Sonnet 5?

Both are developed by Anthropic but target different use cases. Claude Fable 5.1 has a 1.0M token context window vs Claude Sonnet 5's 1.0M. 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 Sonnet 5?

It depends on your use case. Claude Fable 5.1 and Claude Sonnet 5 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 Sonnet 5?

Claude Fable 5.1 costs $10/M input tokens and Claude Sonnet 5 costs $2/M input tokens. Claude Sonnet 5 is $8.00/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 Sonnet 5 on Rival?

This page shows a side-by-side comparison of Claude Fable 5.1 and Claude Sonnet 5 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 Sonnet 5

Claude Sonnet 5 is cheaper than Claude Fable 5.1 at $2/M vs $10/M input tokens.

Claude Fable 5.1 and Claude Sonnet 5 compared across 10 shared prompts
Spec	Claude Fable 5.1	Claude Sonnet 5
Input price	$10/M tokens	$2/M tokens
Output price	$50/M tokens	$10/M tokens
Context window	1.0M tokens	1.0M tokens
Weights	Closed	Closed
Free API (OpenRouter)	No	No
Released	Sep 2026	Jun 2026

Our Verdict

Claude Fable 5.1

Claude Sonnet 5Runner-up

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

Claude Sonnet 5 costs 5.0x less per token.

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

Output

$50.00

Claude Sonnet 5

Input

$2.00

5.0× cheaper

Output

$10.00

5.0× cheaper

Claude Sonnet 5 is cheaper on both: 5.0× input, 5.0× output.

Where to run it

8 hosts

Claude Fable 5.14 hosts

HostInOutContextUptime

Amazon Bedrock$10.00 in$50.00 out1M—Anthropic$10.00 in$50.00 out1M99.1% up Azure AI Foundry$10.00 in$50.00 out1M99.1% up Google Vertex AI$10.00 in$50.00 out1M99.8% up

Claude Sonnet 54 hosts

HostInOutContextUptime

Amazon Bedrock$2.00 in$10.00 out1M99.8% up Azure AI Foundry$2.00 in$10.00 out1M100% up Anthropic$2.00 in$10.00 out1M100% up Google Vertex AI$2.00 in$10.00 out1M99.8% up

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

Research

What we learned reading every model

FAQ

Common questions

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More comparisons

Cost per 1M tokens

8 hosts

What we learned reading every model

Common questions

What is the difference between Claude Fable 5.1 and Claude Sonnet 5?

Which is better, Claude Fable 5.1 or Claude Sonnet 5?

How much does Claude Fable 5.1 cost compared to Claude Sonnet 5?

How can I compare Claude Fable 5.1 and Claude Sonnet 5 on Rival?

More comparisons

Against the newest arrivals

Same lab, same size, long tail

Model pages

Cost per 1M tokens

8 hosts

What we learned reading every model

Common questions

What is the difference between Claude Fable 5.1 and Claude Sonnet 5?

Which is better, Claude Fable 5.1 or Claude Sonnet 5?

How much does Claude Fable 5.1 cost compared to Claude Sonnet 5?

How can I compare Claude Fable 5.1 and Claude Sonnet 5 on Rival?

More comparisons

Against the newest arrivals

Same lab, same size, long tail

Model pages