What is the difference between Claude Fable 5.1 and GPT-5 Nano?

Claude Fable 5.1 is developed by Anthropic while GPT-5 Nano is developed by OpenAI. 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 GPT-5 Nano?

It depends on your use case. Claude Fable 5.1 and GPT-5 Nano 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 can I compare Claude Fable 5.1 and GPT-5 Nano on Rival?

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

Claude Fable 5.1 is the newer model, released after GPT-5 Nano.

Claude Fable 5.1 and GPT-5 Nano compared across 10 shared prompts
Spec	Claude Fable 5.1	GPT-5 Nano
Input price	$10/M tokens	—
Output price	$50/M tokens	—
Context window	1.0M tokens	—
Weights	Closed	Closed
Free API (OpenRouter)	No	No
Released	Sep 2026	Aug 2025

Our Verdict

Claude Fable 5.1

GPT-5 NanoRunner-up

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

Output

$50.00

GPT-5 Nano

Input

—

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 out1M99.1% up Azure AI Foundry$10.00 in$50.00 out1M99.1% up Google Vertex AI$10.00 in$50.00 out1M99.8% up

GPT-5 Nano2 hosts

HostInOutContextUptime

Azure AI Foundry$0.05 in$0.40 out400k100% up OpenAI$0.05 in$0.40 out400k97.4% 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

6 hosts

What we learned reading every model

Common questions

What is the difference between Claude Fable 5.1 and GPT-5 Nano?

Which is better, Claude Fable 5.1 or GPT-5 Nano?

How can I compare Claude Fable 5.1 and GPT-5 Nano 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-5 Nano?

Which is better, Claude Fable 5.1 or GPT-5 Nano?

How can I compare Claude Fable 5.1 and GPT-5 Nano on Rival?

More comparisons

Against the newest arrivals

Same lab, same size, long tail

Model pages