Name: GPT-5.1-Codex-Max API
Brand: OpenAI

Overview

What is GPT-5.1-Codex-Max API?

GPT-5.1-Codex-Max is available through AIMLAPI.

Technical Specifications
- Supported inputs: Image, Text
- Output: Text
- Context window: 400,000 tokens / Max output: 128,000 tokens
- Endpoint: /chat/completions

Performance Benchmarks
[embed]

GPT-5.1-Codex-Max API Pricing
- Input: $1.625 / 1M tokens
- Output: $13 / 1M tokens

Where to Use GPT-5.1-Codex-Max

Coding and code review
Generate, debug, and review code across languages, reading whole files or repos in a single prompt.

Agentic and multi-step workflows
Reliable tool-calling and instruction-following suit agent loops that plan, call tools, and iterate.

Complex reasoning
Extended reasoning improves reliability on multi-step math, logic, and technical analysis.

Long-document analysis
Summarize and extract from contracts, papers, and reports without aggressive chunking.

Code Sample
[embed]

Uptime and performance

Uptime (7d): 100%

Measured on the AI/ML API gateway across live traffic. Figures are medians unless stated. Last updated 2026-10-12.

Use cases

GPT-5.1-Codex-Max is documented as suited to agentic coding tasks in Codex or Codex-like environments, and OpenAI says it is purpose-built for agentic coding.

It is also documented for PR creation, code review, frontend coding, and Q&A as real-world software engineering tasks it was trained on.

OpenAI’s materials also describe it as trained for autonomous software engineering work more broadly, including long-horizon coding workflows.

The model is additionally described as useful for project-scale refactoring and deep debugging, with support for multi-hour agentic work.

How to use GPT-5.1-Codex-Max API

Install any OpenAI-compatible SDK, point it at api.aimlapi.com/v1, and set the model to openai/gpt-5.1-codex-max.

import requests

r = requests.post(
    "https://api.aimlapi.com/v1/chat/completions",
    headers={"Authorization": "Bearer " + AIMLAPI_KEY},
    json={
      "model": "openai/gpt-5.1-codex-max",
      "messages": [
        {
          "role": "user",
          "content": "Hello!"
        }
      ]
    },
)
print(r.json())

const r = await fetch("https://api.aimlapi.com/v1/chat/completions", {
  method: "POST",
  headers: {
    Authorization: `Bearer ${process.env.AIMLAPI_KEY}`,
    "Content-Type": "application/json",
  },
  body: JSON.stringify({
    "model": "openai/gpt-5.1-codex-max",
    "messages": [
      {
        "role": "user",
        "content": "Hello!"
      }
    ]
  }),
});
console.log(await r.json());

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

OpenAI-compatible — swap the base URL and it works with your existing SDK.