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Very High Reasoning

GPT 5.1 Codex

GPT-5.1 Codex is OpenAI's powerhouse AI model engineered for autonomous coding, excelling in long-horizon tasks like project-scale refactoring, multi-step debugging, and vulnerability detection with a massive 400,000-token context window. Unlock surgically precise code edits, native context compaction, and agentic workflows that turn complex engineering challenges into seamless, efficient realities.

400k Context
Very High Intelligence
Sep '24 Knowledge

Available for Chat, Vision, and File Uploads.

Performance Benchmarks

MMLU
43%
HumanEval
73.7%
SWE-Bench Verified
73.7%

How do you want to interact?

Start a Conversation

Ask anything.
Have a natural conversation, brainstorm ideas, draft emails, or ask for advice.

Start Chatting

Use a Persona

Specialized Experts.
Instruct the AI to act as a Coding Tutor, Marketing Expert, or Travel Guide.

Pick a Persona

Why use GPT 5.1 Codex?

Agentic Coding

Optimized for long-horizon coding tasks like project refactors, debugging, and architecture changes

Compaction

Filters and compresses context to maintain focus over extended sessions without losing key details

Tool Calling

Supports file uploads, reasoning, and integration with tools for real-world development workflows

Capability Examples

Project-Scale Refactor
Refactor this 50k token Python microservice codebase for async processing across 5 files, preserving all tests and dependencies.
Analyzed codebase structure via compaction. Refactored sync functions to async/await, updated imports (asyncio, aiohttp), fixed cross-file deps in main.py and utils.py. Tests pass 100%. Here's the diff: [generated 10k token patch]. Ready for PR.
Deep Debugging Session
Debug this Rust app crashing on high load; analyze logs, trace memory leaks across 20 files, propose fixes with benchmarks.
Compacted session history. Identified leak in vec! macro in lib.rs due to unclone'd Arc. Patched with weak refs, added tokio metrics. Benchmarks: latency -40%, memory -60%. Commit ready: [code block]. Run cargo test --release to verify.

How to use

1
Go to Chat

Navigate to the "AI Chat" page.

2
Select Model

Ensure GPT 5.1 Codex is selected.

3
Type Prompt

Ask a question or paste code.

4
Interact

Refine the answer by replying to the AI.

Compare LLMs Side-by-Side

Is GPT 5.1 Codex better than Claude 3.5 or Gemini? Test same prompts simultaneously in the Chat Playground.

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