GPT-5 Codex

Retired

OpenAI · September 2025

OpenAI retired this model on 23 July 2026, so you can't start new chats with it. Use GPT-5.3 Codex instead. Your previous conversations are still available.

Built for programming and long, self-directed coding tasks. Not meant for general chat.

Best for: Coding, deep reasoning, and agent workflows
Superseded by: GPT-5.1 Codex

Context window
400,000 tokens
≈ 300,000 words · about 1,200 pages
Max output
128,000 tokens
≈ 96,000 words in a single answer
Knowledge cutoff
September 2024
its training cutoff

Modalities

TextInput and output
ImageInput only
AudioNot supported
VideoNot supported

Reasoning effort

Low
Medium
High

Features

StreamingSupported
Function callingSupported
Structured outputsSupported
Fine-tuningNot supported

Ready to try it?

Polymeti is currently invite-only.

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