GPT-5.1-Codex-Max overview
GPT-5.1-Codex-Max specs
- Model ID
openai/gpt-5.1-codex-max- Developer
- OpenAI
- Context window
- 400,000 tokens
- Max output
- 128,000 tokens
- Input
- Image, Text
- Output
- Text
- API
- OpenAI-compatible, base URL
https://api.aimlapi.com/v1
What is GPT-5.1-Codex-Max API?
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.
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.
Capabilities
- Function calling
- Reasoning
- Streaming
- Structured outputs
- Web search
GPT-5.1-Codex-Max API pricing
| Usage | Price | Unit |
|---|---|---|
| Input | $2.65 | 1M tokens |
| Output | $21.16 | 1M tokens |
| Cached input | $0.2645 | 1M tokens |
Prices from the AI/ML API price list, checked on Nov 4, 2026.
GPT-5.1-Codex-Max vs other models: token prices
AI/ML API input and output rates for 5 models, per million tokens.
| Model | Input | Output |
|---|---|---|
| $2.65 | $21.16 | |
| $0.1 | $0.5 | |
| $1 | $5 | |
| $2 | $10 | |
| $2.12 | $10.58 |
How to use the GPT-5.1-Codex-Max API
View docsBuild with your agent
Give your agent the model details, code and documentation.
1Get your API key
Create API keyexport AIMLAPI_KEY="8f2b4c7d9a1e6b3f…"2Make your first request
curl '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": "Write a haiku about the ocean."
}
]
}'import os
import requests
headers = {
"Authorization": f"Bearer {os.environ['AIMLAPI_KEY']}",
"Content-Type": "application/json",
}
payload = {
"model": "openai/gpt-5.1-codex-max",
"messages": [
{
"role": "user",
"content": "Write a haiku about the ocean."
}
]
}
response = requests.post("https://api.aimlapi.com/v1/chat/completions", headers=headers, json=payload, timeout=120)
response.raise_for_status()
print(response.json())const response = 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": "Write a haiku about the ocean."
}
]
}),
});
if (!response.ok) throw new Error(`HTTP ${response.status}`);
console.log(await response.json());Related articles
GPT-5.1-Codex-Max FAQ
What is the context window of GPT-5.1-Codex-Max?
GPT-5.1-Codex-Max has a 400,000 tokens context window and can return up to 128,000 tokens.
What inputs and outputs does GPT-5.1-Codex-Max support?
GPT-5.1-Codex-Max takes image, text as input and returns text.
What is the model ID for GPT-5.1-Codex-Max?
Use openai/gpt-5.1-codex-max as the model id. Requests go to https://api.aimlapi.com/v1/chat/completions.
How much does GPT-5.1-Codex-Max cost?
GPT-5.1-Codex-Max costs $2.65 input and $21.16 output per 1M tokens on AI/ML API, billed as you go with no subscription.
Does GPT-5.1-Codex-Max support streaming?
Yes, GPT-5.1-Codex-Max can stream responses as they are generated.
Can GPT-5.1-Codex-Max read images?
Yes, GPT-5.1-Codex-Max accepts image input alongside text.
Who created GPT-5.1-Codex-Max?
GPT-5.1-Codex-Max was built by OpenAI.
Can GPT-5.1-Codex-Max be accessed through an API?
Yes, it is available via the API endpoint https://api.aimlapi.com/v1/chat/completions.

