GPT-5.1-Codex

Name: OpenAI: GPT-5.1-Codex
Brand: openai
SKU: openai/gpt-5.1-codex
Price: 1.375 USD
Availability: InStock

openai/gpt-5.1-codex

GPT-5.1-Codex is a specialized version of GPT-5.1 optimized for software engineering and coding workflows.

$1.375 in · $11.00 out per 1M tokens400k contextNov 13, 2025

about 0.6¢ a message

A typical message: about 500 tokens you send and 500 it writes.

Chat with GPT-5.1-Codex

Call it from code Lock this price

Spec sheet

Published facts from the catalog, billed prices and what we measured here. Anything not measured says so.

Price, billed here

Input, per 1M tokens: $1.375provider $1.25
Output, per 1M tokens: $11.00provider $10.00
Cached input, per 1M: $0.143provider $0.13
Margin: +10%

Context and formats

Context window: 400,000 tokens
Longest answer: 128,000 tokens
Reads: text and images
Makes: text
First listed: 2025-11-13

Measured here, last 7 days

First token, median: not measured
Answered without error: not measured

Tools and JSON

Tool calling: declaredthe provider's claim, not yet measured here
JSON output: declaredthe provider's claim, not yet measured here

Price and latency history as JSON: GET /api/planet/history?id=openai/gpt-5.1-codex.

About

GPT-5.1-Codex is a specialized version of GPT-5.1 optimized for software engineering and coding workflows. It is designed for both interactive development sessions and long, independent execution of complex engineering tasks....

In OpenAI's words.

Try it here

Cmd+Enter sends

The answer appears here.

Measured here

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Call it

Use one OpenAI compatible endpoint, this model's id and an am_live_ key from the dashboard. You can also try it in chat first with no key.

curl https://useantimatter.com/v1/chat/completions \
  -H "Authorization: Bearer $ANTIMATTER_API_KEY" \
  -H "Content-Type: application/json" \
  -d '{"model": "openai/gpt-5.1-codex", "messages": [{"role": "user", "content": "Hello"}]}'

Everything else is in the docs.

Embed this

A badge showing this model's live price per million tokens, as billed here, for a README or a site. It links back to this page.

<a href="https://useantimatter.com/planet/openai/gpt-5.1-codex"><img src="https://useantimatter.com/api/badge/price?id=openai%2Fgpt-5.1-codex" alt="GPT-5.1-Codex price on Antimatter" height="28"></a>

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