What is the difference between GPT-5.1-Codex and GPT-6 Astra Pro?

Both are developed by OpenAI but target different use cases. GPT-5.1-Codex has a 400K token context window vs GPT-6 Astra Pro's 1.1M. You can compare their actual outputs across 5 challenges on Rival to see how they differ in practice.

Which is better, GPT-5.1-Codex or GPT-6 Astra Pro?

It depends on your use case. GPT-5.1-Codex and GPT-6 Astra Pro each have strengths in different areas. Rival lets you compare their real outputs side-by-side across 5 challenges so you can judge which fits your needs best.

How much does GPT-5.1-Codex cost compared to GPT-6 Astra Pro?

GPT-5.1-Codex costs $1.25/M input tokens and GPT-6 Astra Pro costs $10/M input tokens. GPT-5.1-Codex is $8.75/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 GPT-5.1-Codex and GPT-6 Astra Pro on Rival?

This page shows a side-by-side comparison of GPT-5.1-Codex and GPT-6 Astra 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

GPT-5.1-CodexvsGPT-6 Astra Pro

GPT-5.1-Codex is cheaper than GPT-6 Astra Pro at $1.25/M vs $10/M input tokens.

GPT-5.1-Codex and GPT-6 Astra Pro compared across 5 shared prompts
Spec	GPT-5.1-Codex	GPT-6 Astra Pro
Input price	$1.25/M tokens	$10/M tokens
Output price	$10/M tokens	$50/M tokens
Context window	400K tokens	1.1M tokens
Weights	Closed	Closed
Free API (OpenRouter)	No	No
Released	Nov 2025	Sep 2026

Our Verdict

GPT-6 Astra Pro

GPT-5.1-CodexRunner-up

Not enough votes to call it. On the specs, GPT-6 Astra Pro has the edge: newer, bigger context window.

GPT-5.1-Codex 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

GPT-5.1-Codex

Input

$1.25

8.0× cheaper

Output

$10.00

5.0× cheaper

GPT-6 Astra Pro

Input

$10.00

Output

$50.00

GPT-5.1-Codex is cheaper on both: 8.0× input, 5.0× output.

Where to run it

3 hosts

GPT-5.1-Codex1 host

HostInOutContextUptime

Azure AI Foundry$1.25 in$10.00 out400k100% up

GPT-6 Astra Pro2 hosts

HostInOutContextUptime

Azure AI Foundry$10.00 in$50.00 out1.1M98.9% up OpenAI$10.00 in$50.00 out1.1M99.6% 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

3 hosts

What we learned reading every model

Common questions

What is the difference between GPT-5.1-Codex and GPT-6 Astra Pro?

Which is better, GPT-5.1-Codex or GPT-6 Astra Pro?

How much does GPT-5.1-Codex cost compared to GPT-6 Astra Pro?

How can I compare GPT-5.1-Codex and GPT-6 Astra Pro on Rival?

More comparisons

Against the newest arrivals

Same lab, same size, long tail

Model pages

Cost per 1M tokens

3 hosts

What we learned reading every model

Common questions

What is the difference between GPT-5.1-Codex and GPT-6 Astra Pro?

Which is better, GPT-5.1-Codex or GPT-6 Astra Pro?

How much does GPT-5.1-Codex cost compared to GPT-6 Astra Pro?

How can I compare GPT-5.1-Codex and GPT-6 Astra Pro on Rival?

More comparisons

Against the newest arrivals

Same lab, same size, long tail

Model pages