---
title: GPT-5.1-Codex-Max — Agentic Coding | ModelsLab
description: Access OpenAI: GPT-5.1-Codex-Max API for million-token context compaction and 24-hour autonomous coding. Generate complex software now.
url: https://modelslab.com/openai-gpt-51-codex-max
canonical: https://modelslab.com/openai-gpt-51-codex-max
type: website
component: Seo/ModelPage
generated_at: 2026-05-05T21:16:29.944574Z
---

Available now on ModelsLab · Language Model

OpenAI: GPT-5.1-Codex-Max
Code Autonomously for Hours
---

[Try OpenAI: GPT-5.1-Codex-Max](/models/open_router/openai-gpt-5.1-codex-max) [API Documentation](https://docs.modelslab.com)

Master Long-Running Tasks
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Context Compaction

### Million-Token Workflows

Handles multiple context windows via native compaction for coherent tasks over millions of tokens.

xHigh Reasoning

### 77.9% SWE-Bench Score

Achieves top code quality on complex problems with 30% fewer thinking tokens than predecessors.

Extended Execution

### 24-Hour Autonomy

Runs continuously, iterating code, fixing tests, and checkpointing progress without intervention.

Examples

See what OpenAI: GPT-5.1-Codex-Max can create
---

Copy any prompt below and try it yourself in the [playground](/models/open_router/openai-gpt-5.1-codex-max).

Full Stack App

“Plan, implement, and test a complete React frontend with Node.js backend for a task management app, handling authentication, database integration, and API endpoints across multiple files.”

Code Refactor

“Analyze existing 500k-token Python codebase, identify inefficiencies, refactor for performance, add unit tests, and verify against benchmarks autonomously.”

Agent Loop

“Build self-improving agent that generates, debugs, and deploys ML model training pipeline, iterating until accuracy exceeds 95% on dataset.”

Multi-File Project

“Develop enterprise-grade TypeScript library for data processing, including docs, examples, CI/CD setup, and integration tests over extended session.”

For Developers

A few lines of code.
Agentic code. One call.
---

ModelsLab handles the infrastructure: fast inference, auto-scaling, and a developer-friendly API. No GPU management needed.

- **Serverless:** scales to zero, scales to millions
- **Pay per token,** no minimums
- **Python and JavaScript SDKs,** plus REST API

[API Documentation ](https://docs.modelslab.com)

PythonJavaScriptcURL

Copy

```
<code>import requests

response = requests.post(
    "https://modelslab.com/api/v7/llm/chat/completions",
    json={
  "key": "YOUR_API_KEY",
  "prompt": "",
  "model_id": ""
}
)
print(response.json())</code>
```

FAQ

Common questions about OpenAI: GPT-5.1-Codex-Max
---

[Read the docs ](https://docs.modelslab.com)

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

OpenAI: GPT-5.1-Codex-Max is an agentic coding model for long-running software tasks. It uses context compaction for million-token contexts. Access via LLM endpoints.

### How does openai gpt 5.1 codex max handle large codebases?

It compacts contexts natively to work coherently over millions of tokens. Supports 24+ hour autonomous execution with progress checkpoints. Ideal for refactors and multi-file projects.

### What is xhigh reasoning in OpenAI: GPT-5.1-Codex-Max model?

xhigh effort level scores 77.9% on SWE-bench Verified. Uses 30% fewer tokens for deeper analysis on complex coding. Configurable via reasoning.effort parameter.

### Is OpenAI: GPT-5.1-Codex-Max alternative to GPT-5?

Yes, it's a specialized update for agentic coding with improved time horizons and benchmarks. Outperforms on software engineering tasks like PRs and reviews.

### What tasks does openai: gpt-5.1-codex-max excel at?

Excels in planning, implementing, testing features autonomously. Handles frontend coding, Q&A, math, and research via agentic training. 400k context window.

### How to integrate OpenAI: GPT-5.1-Codex-Max LLM?

Use v1/chat/completions or v1/responses endpoints. Bring your key for GitHub Copilot or direct API calls. Enable in model picker for Pro plans.

Ready to create?
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Start generating with OpenAI: GPT-5.1-Codex-Max on ModelsLab.

[Try OpenAI: GPT-5.1-Codex-Max](/models/open_router/openai-gpt-5.1-codex-max) [API Documentation](https://docs.modelslab.com)

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*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)

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*Generated by ModelsLab - 2026-05-06*