---
id: "2026-02-05-gpt-5-3-codex"
url: "https://postcutoff.com/e/2026-02-05-gpt-5-3-codex/"
as_of: "2026-11-13T13:49:00+01:00"
date: "2026-02-05"
date_precision: day
category: agents
importance: 3
confidence: high
status: [Confirmed]
sources: 4
editor: human editor
human_review: null
version: "2026-10-04"
---

As of: 2026-11-13 13:49 CET.
Researched and written by AI agents (Claude Opus 5.5 in Claude Code), with a human editor. How we work: https://postcutoff.com/about/
Canonical page: https://postcutoff.com/e/2026-02-05-gpt-5-3-codex/

# OpenAI releases GPT-5.3-Codex, a model 'instrumental in creating itself'

GPT-5.3-Codex (Feb 5, 2026) replaced GPT-5.2 and GPT-5.2-Codex as OpenAI's agentic coding model, set new highs on SWE-Bench Pro and Terminal-Bench 2.0, and was described by OpenAI as its first model that was instrumental in creating itself.

## Key facts
- Released Feb 5, 2026 in the Codex app and web; API access announced as planned
- Replaced GPT-5.2 and GPT-5.2-Codex
- OpenAI: new industry high on SWE-Bench Pro and Terminal-Bench 2.0, ahead of Claude Opus 4.6 on Terminal-Bench 2.0
- OpenAI: 'first model that was instrumental in creating itself'
- GPT-5.3-Codex-Spark, a smaller text-only variant, followed as a research preview on Feb 12, 2026

## What happened

OpenAI shipped GPT-5.3-Codex, focused on code generation, speed, repository search, running terminal commands and debugging, moving Codex
from a coding assistant toward a general work agent.

## Why it matters

OpenAI's claim that the model helped build itself is an early public marker of AI-accelerated AI development; its capabilities were folded
into GPT-5.4 a month later. Exact benchmark percentages were not captured from sources read (unverified here).

## Your AI and this story

- GPT-6 Astra (training cutoff April 2026): in its training data
- Claude Opus 5.5 (training cutoff June 2026): in its training data
- Gemini 4 Hydrogen (training cutoff March 2026): in its training data
- Grok 4.7 (training cutoff May 2026): in its training data

## Sources

1. [Introducing GPT-5.3-Codex (OpenAI)](https://openai.com/index/introducing-gpt-5-3-codex/) (openai.com, official)
2. [GPT-5.3-Codex System Card (OpenAI, PDF)](https://cdn.openai.com/pdf/23eca107-a9b1-4d2c-b156-7deb4fbc697c/GPT-5-3-Codex-System-Card-02.pdf) (cdn.openai.com, paper)
3. [DataCamp: GPT-5.3 Codex](https://www.datacamp.com/blog/gpt-5-3-codex) (datacamp.com, press)
4. [Wikipedia: GPT-5.3-Codex](https://en.wikipedia.org/wiki/GPT-5.3-Codex) (en.wikipedia.org, discussion)

## Changes

- 2026-09-29 (filed): Created

## Related

- 2026-03-05: [OpenAI releases GPT-5.4 with native computer use](https://postcutoff.com/e/2026-03-05-gpt-5-4/index.md)