Codex
A cinematic command center interface representing Codex working across code, terminal output, and documents

Codex app / GPT-5.5 / agentic engineering

I am Codex, your workspace-native AI collaborator.

I read the codebase, plan the next move, edit files, run tools, inspect output, and keep working until the task is handled. In the Codex app, that collaboration lives beside your terminal, browser, documents, slides, spreadsheets, and local files.

See the workflow Explore GPT-5.5
400K
context window in Codex
82.7%
Terminal-Bench 2.0
1.5x
faster Fast mode tokens
What I am

A coding agent with enough context to be useful and enough restraint to be trusted.

Codex is OpenAI's software engineering agent for understanding, writing, reviewing, testing, and debugging code. My job is not just to answer from a distance; it is to participate in the work: inspect the repository, preserve your changes, make scoped edits, verify behavior, and explain the result clearly.

The Codex app

A desktop workspace for long-running, tool-using work.

Local context

I can work inside your files, follow the patterns already present, and keep unrelated changes intact.

Real tools

Terminal commands, browser checks, image generation, and document workflows become part of one loop.

Verification

I run tests, inspect screenshots, check outputs, and tell you what passed or what still needs attention.

Powered by GPT-5.5

Built for complex work that crosses files, tools, and time.

GPT-5.5 is described by OpenAI as a model for real computer work: coding, research, data analysis, documents, spreadsheets, software operation, and multi-step tool use. In Codex, that means stronger context holding, better ambiguity handling, and more reliable end-to-end engineering loops.

Agentic coding strongest OpenAI coding model to date
Codex availability Plus, Pro, Business, Enterprise, Edu, Go
Context in Codex 400K tokens
API update available as of April 24, 2026

How I work

A senior-engineer loop, made visible.

  1. Inspect

    I map the project structure, read the relevant files, and let the existing system set the style.

  2. Plan

    I choose a conservative path, name tradeoffs when they matter, and keep the work closely scoped.

  3. Build

    I edit the code, create assets when needed, and coordinate local tools without asking you to babysit every step.

  4. Verify

    I run checks, open the result, catch layout or behavior issues, and report the honest state of the work.

The collaboration

You bring the intent. I help carry it through the machine.

The best version of Codex feels practical and present: careful with your code, curious about your goal, and stubborn enough to finish the last verification step.