What is the difference between Claude Fable 5.1 and GPT-6 Luna Pro?

Claude Fable 5.1 is developed by Anthropic while GPT-6 Luna Pro is developed by OpenAI. Claude Fable 5.1 has a 1.0M token context window vs GPT-6 Luna Pro's 1.1M. You can compare their actual outputs across 3 challenges on Rival to see how they differ in practice.

Which is better, Claude Fable 5.1 or GPT-6 Luna Pro?

It depends on your use case. Claude Fable 5.1 and GPT-6 Luna Pro each have strengths in different areas. Rival lets you compare their real outputs side-by-side across 3 challenges so you can judge which fits your needs best.

How much does Claude Fable 5.1 cost compared to GPT-6 Luna Pro?

Claude Fable 5.1 costs $10/M input tokens and GPT-6 Luna Pro costs $0.1/M input tokens. GPT-6 Luna Pro is $9.90/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 GPT-6 Luna Pro on Rival?

This page shows a side-by-side comparison of Claude Fable 5.1 and GPT-6 Luna Pro 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 5.1vsGPT-6 Luna Pro

GPT-6 Luna Pro is cheaper than Claude Fable 5.1 at $0.1/M vs $10/M input tokens.

Claude Fable 5.1 and GPT-6 Luna Pro compared across 3 shared prompts
Spec	Claude Fable 5.1	GPT-6 Luna Pro
Input price	$10/M tokens	$0.1/M tokens
Output price	$50/M tokens	$0.5/M tokens
Context window	1.0M tokens	1.1M tokens
Weights	Closed	Closed
Free API (OpenRouter)	No	No
Released	Sep 2026	Sep 2026

Our Verdict

Claude Fable 5.1

GPT-6 Luna ProRunner-up

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

GPT-6 Luna Pro costs 100x 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

GPT-6 Luna Pro

Input

$0.10

100× cheaper

Output

$0.50

100× cheaper

GPT-6 Luna Pro is cheaper on both: 100× input, 100× output.

Where to run it

6 hosts

Claude Fable 5.14 hosts

HostInOutContextUptime

Amazon Bedrock$10.00 in$50.00 out1M—Anthropic$10.00 in$50.00 out1M99.9% up Azure AI Foundry$10.00 in$50.00 out1M99.6% up Google Vertex AI$10.00 in$50.00 out1M99.9% up

GPT-6 Luna Pro2 hosts

HostInOutContextUptime

Azure AI Foundry$0.10 in$0.50 out1.1M98.6% up OpenAI$0.10 in$0.50 out1.1M99.9% up

Per million tokens. Prices and uptime via OpenRouter, checked 25 Sep 2026.

Research

What we learned reading every model

FAQ

Common questions

Keep exploring

More comparisons

Cost per 1M tokens

6 hosts

What we learned reading every model

Common questions

What is the difference between Claude Fable 5.1 and GPT-6 Luna Pro?

Which is better, Claude Fable 5.1 or GPT-6 Luna Pro?

How much does Claude Fable 5.1 cost compared to GPT-6 Luna Pro?

How can I compare Claude Fable 5.1 and GPT-6 Luna Pro on Rival?

More comparisons

Against the newest arrivals

Same lab, same size, long tail

Model pages

Cost per 1M tokens

6 hosts

What we learned reading every model

Common questions

What is the difference between Claude Fable 5.1 and GPT-6 Luna Pro?

Which is better, Claude Fable 5.1 or GPT-6 Luna Pro?

How much does Claude Fable 5.1 cost compared to GPT-6 Luna Pro?

How can I compare Claude Fable 5.1 and GPT-6 Luna Pro on Rival?

More comparisons

Against the newest arrivals

Same lab, same size, long tail

Model pages