> GPT-5.1-Codex is a closed AI model from OpenAI, released 12 Nov 2025. API price $1.25 in / $10 out per million tokens, 400K context.

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# GPT-5.1-Codex

OpenAI

Released 12 Nov 2025

Closed

[Compare](https://themodelindex.org/compare/gpt-5-1-codex-vs-deepseek-v3-2/)

–

Index score

Not yet evaluated independently

1/ 8

Core tests taken

1 of 6 areas · plus 0 anchor tests

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Versus the frontier at release

Replaced by [GPT-5.2-Codex](https://themodelindex.org/models/gpt-5-2-codex/)

$1.25/ $10

Price per million tokens

input / output, list price

400K

Context window

tokens it reads at once

## Where it sits · on the frontier

_Chart: Model Index score of every scored model since late 2022, with the best closed and best open model over time_

Among the first models to reach this score.

## Test results · by area · tick = best by any model

Reasoning & knowledge

no evidence yet

GPQA Diamond

no result

Humanity's Last Exam

no result

Maths

no evidence yet

FrontierMath T1-3

no result

Coding

evidence

SWE-bench Verified

no result

Terminal-Bench

58%

Agents

no evidence yet

APEX-Agents

no result

Novel problems

no evidence yet

ARC-AGI-2

no result

Long tasks

no evidence yet

METR time horizon

no result

Independent results from the Epoch AI benchmarking hub, best reasoning setting. The core tests are shown here; anchor tests also inform the score and can be shown above.

## What others say · rank on each leaderboard

LMArena · WebDev

building web apps and front ends

#99

of 123 · 1337

Further left is better. Leaderboards measure different things: LMArena is people voting blind between two answers, the others are test scores. Click any row for the source.

## Best at · top three among current models

Replaced by GPT-5.2-Codex; it no longer leads any category among current models.

Where this model places in the top three of today's models, on category leaderboards and on our core tests.

## Where to use it · prices checked 1 Oct 2026

#### From the lab

ChatGPT

app · subscription

↗

OpenAI API

API

↗

#### API providers · 1 · per million tokens, in / out

A

Azure

$1.25 / $10

cheapest

Provider prices come from OpenRouter's live listing; going direct to a provider can differ. Subscriptions are the lab's own apps.

## Facts and sources

Released

12 Nov 2025

Announcement

not linked yet

Release entry

–

Scored as

GPT-5.1-Codex

Artificial Analysis index

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Output speed

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Hugging Face

closed weights

## OpenAI releases · around this one

ChatGPT

Closed

30 NOV 2022

GPT-4

Closed

14 MAR 2023

index 100

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Source: https://themodelindex.org/models/gpt-5-1-codex/ · The Model Index · data as of 2026-10-01