Codex CLI

Codex CLI is OpenAI’s open-source terminal coding agent.

Overview

Type	CLI
Open Source	Yes (April 2025)
Best For	OpenAI models, ChatGPT subscribers

Key Features

• Agentic — File editing, terminal commands
• Multi-file — Understands project structure
• Sandbox Mode — Isolated execution
• ChatGPT Integration — Works with existing subscription

Installation

npm install -g @openai/codex

Access Model

The Codex CLI client is open source. Usage depends on your OpenAI account access, either through API usage or eligible ChatGPT plans.

Works with:

• ChatGPT account access
• OpenAI API directly

As of Feb 25, 2026, the openai/codex repository is active and regularly released.

Privacy

Setting	Value
Open Source	Yes (client)
Training	OpenAI terms
Jurisdiction	US (OpenAI)

Models Available

Model availability changes quickly. In practice, Codex CLI uses current GPT-5/Codex model families based on account access.

Getting Started

# With API key
export OPENAI_API_KEY=sk-...
codex

# Or authenticate with ChatGPT
codex auth

Sandbox Mode

Codex CLI includes a sandbox for safer execution:

# Run with sandboxed terminal
codex --sandbox

# Sandbox restricts:
# - Network access (configurable)
# - File system access (project only)
# - Process execution (limited)

Key Commands

Command	Action
/help	Show commands
/clear	Reset context
/sandbox	Toggle sandbox mode
/model <name>	Switch model

SWE-bench Performance

Codex CLI with Codex 5 achieves 74.9% on SWE-bench verified, one of the highest scores for agentic coding.

Model	SWE-bench
Codex 5	74.9%
GPT-5.2	72.1%

Tips

• Use Codex 5 for coding tasks (optimized)
• Enable sandbox for untrusted projects
• ChatGPT subscription works — no separate API key needed