---
title: OpenAI: GPT 5.1 Codex Max API | Text Generation | ModelsLab
description: Advanced agentic coding model with 272K input tokens, multi-context window support, and 58.1% Terminal Bench performance for long-horizon software.
url: https://modelslab.com/models/openai/openai-gpt-5.1-codex-max/api.md
canonical: https://modelslab.com/models/openai/openai-gpt-5.1-codex-max/api.md
type: product
component: Playground/LLM/Index
generated_at: 2026-04-15T02:04:59.728969Z
---

OpenAI: GPT-5.1-Codex-Max
---

 [LLMs.txt](https://modelslab.com/models/open_router/openai-gpt-5.1-codex-max/llms.txt) [.md](https://modelslab.com/models/openai/openai-gpt-5.1-codex-max.md)

openai-gpt-5.1-codex-max openai Closed Source Model $5.625000 / call

OpenAI: GPT-5.1-Codex-Max
---

Choose a prompt below to get started or type your own message

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### OpenAI: GPT-5.1-Codex-Max

openai openai-gpt-5.1-codex-max

Copy model ID

PricingInput $1.25 / 1M tokens

Output $10.00 / 1M tokens

API EndpointsOpenAI Compatible

`https://modelslab.com/api/v7/llm/chat/completions`Endpoint

Anthropic Compatible

`https://modelslab.com/api/v7/llm/v1/messages`Messages

`https://modelslab.com/api/v7/llm/v1/messages/count_tokens`Count Tokens

`https://modelslab.com/api/v7/llm/v1/models`Models

Use with Claude Code

cURL Example

ParametersSystem MessageYou are a helpful AI assistant specialized in providing accurate and detailed responses.

Temperature0.7

Max Tokens1000

Top P0.9

Frequency Penalty0

Presence Penalty0

Model Info

Support

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About OpenAI: GPT-5.1-Codex-Max
---

GPT-5.1-Codex-Max is OpenAI’s latest agentic coding model, designed for long-running, high-context software development tasks. It is based on an updated version of the 5.1 reasoning stack and trained on agentic...

### Technical Specifications

Model IDopenai-gpt-5.1-codex-maxCategoryLLM ModelsTaskText GenerationPrice$5.625000 per million tokensAddedFebruary 20, 2026

### Key Features

- Chat completion and multi-turn conversation API
- Streaming response with token-by-token output
- Function calling and tool use support
- System prompts and role-based messaging
- JSON mode and structured output

### Quick Start

Integrate OpenAI: GPT-5.1-Codex-Max into your application with a single API call. Get your API key from the [pricing page](https://modelslab.com/pricing) to get started.

PythonJavaScriptcURLPHP

```
<code>import requests
import json

url = "https://modelslab.com/api/v7/llm/chat/completions"

headers = {
    "Content-Type": "application/json"
}

data = {
        "model_id": "openai-gpt-5.1-codex-max",
        "messages": [
            {
                "role": "user",
                "content": "Hello!"
            }
        ],
        "max_tokens": 1000,
        "key": "YOUR_API_KEY"
    }

try:
    response = requests.post(url, headers=headers, json=data)
    response.raise_for_status()  # Raises an HTTPError for bad responses (4XX or 5XX)
    result = response.json()
    print("API Response:")
    print(json.dumps(result, indent=2))
except requests.exceptions.HTTPError as http_err:
    print(f"HTTP error occurred: {http_err} - {response.text}")
except Exception as err:
    print(f"Other error occurred: {err}")</code>
```

View the [full API documentation](https://modelslab.com/models/openai/openai-gpt-5.1-codex-max/api) for SDKs, code examples in Python, JavaScript, and more.

### Pricing

OpenAI: GPT-5.1-Codex-Max API costs $5.625000 per million tokens. Pay only for what you use with no minimum commitments. [View pricing plans](https://modelslab.com/pricing)

### Use Cases

- AI chatbots and virtual assistants
- Code generation and developer tools
- Content writing and copywriting automation
- Data analysis, summarization, and extraction

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OpenAI: GPT-5.1-Codex-Max FAQ
---

### What is OpenAI: GPT-5.1-Codex-Max?

GPT-5.1-Codex-Max is OpenAI’s latest agentic coding model, designed for long-running, high-context software development tasks. It is based on an updated version of the 5.1 reasoning stack and trained on agentic...

### How do I use the OpenAI: GPT-5.1-Codex-Max API?

You can integrate OpenAI: GPT-5.1-Codex-Max into your application with a single API call. Sign up on ModelsLab to get your API key, then use the model ID "openai-gpt-5.1-codex-max" in your API requests. We provide SDKs for Python, JavaScript, and cURL examples in the API documentation.

### How much does OpenAI: GPT-5.1-Codex-Max cost?

OpenAI: GPT-5.1-Codex-Max costs $5.625000 per million tokens. ModelsLab uses pay-per-use pricing with no minimum commitments. A free tier is available to get started.

### What is the OpenAI: GPT-5.1-Codex-Max model ID?

The model ID for OpenAI: GPT-5.1-Codex-Max is "openai-gpt-5.1-codex-max". Use this ID in your API requests to specify this model.

### Does OpenAI: GPT-5.1-Codex-Max have a free tier?

Yes, ModelsLab offers a free tier that lets you try OpenAI: GPT-5.1-Codex-Max and other AI models. Sign up to get free API credits and start building immediately.

---

*This markdown version is optimized for AI agents and LLMs.*

**Links:**
- [Website](https://modelslab.com)
- [API Documentation](https://docs.modelslab.com)
- [Blog](https://modelslab.com/blog)

---
*Generated by ModelsLab - 2026-04-15*