Installing and Using the OpenAI Codex CLI

Codex CLI is OpenAI's terminal coding agent. It runs locally, supports MCP, and ships a codex cloud mode for background tasks. Let's install it and compare it honestly to Claude Code.

45 min · Reviewed 2026

OpenAI's Answer to Claude Code

Codex CLI is OpenAI's lightweight coding agent. It runs in your terminal, inspects your repo, edits files, and executes shell commands. It ships on macOS, Windows, and Linux, and its premium models are included with ChatGPT Plus, Pro, and Business plans.

Install and first run

# Install via npm (macOS, Linux, Windows) npm install -g @openai/codex # Or via Homebrew on macOS brew install openai/codex/codex # Launch in your project directory cd my-project codex # Type /model to pick a model # Default in 2026: gpt-5.5 for complex work, gpt-5.3-codex for fast tasksAs of April 2026, gpt-5.5 is the recommended model for complex work; gpt-5.3-codex is tuned for fast edits.

Two modes you will use

Mode	Command	What it's for
Interactive TUI	codex	Conversational coding, the default experience
Exec	codex exec "<prompt>"	Scripted, non-interactive runs — great for CI
Cloud	codex cloud	Offload long tasks to OpenAI's infra, review locally

A realistic exec workflow

# Automate a recurring task with `codex exec` codex exec "Find all task list comments in src/, group them by file, \ and write a markdown summary to TODO_REPORT.md" # Run in CI after PR checks pass codex exec --model gpt-5.5 "Review the diff against main and \ flag any missing test coverage for changed functions."Exec mode turns Codex into a scriptable tool you can chain with Make, GitHub Actions, or cron.

codex cloud: the superpower

The codex cloud command launches tasks on OpenAI infrastructure, which can run long without tying up your laptop. You can hand off a refactor at 5pm and pull the PR in the morning. Running codex cloud with no arguments opens an interactive picker of active and finished tasks.

Image input

You can paste screenshots or design specs directly into the Codex composer or pass image files on the command line. This is ideal for turning a mockup into real components or diagnosing a UI bug from a screen recording.

Claude Code vs. Codex CLI: the honest comparison

Dimension	Claude Code	Codex CLI
Model	Claude family	GPT family
Project memory	CLAUDE.md	AGENTS.md (similar concept)
Parallel agents	Up to 10 subagents	Single-session + cloud offload
Extensibility	Skills, hooks, 25+ lifecycle events	MCP, exec scripts, cloud tasks
Pricing entry	Claude Pro $20/mo	Included in ChatGPT Plus/Pro

The best agent is the one whose workflow matches your brain.
— A polyglot engineer

The big idea: Codex CLI and Claude Code are two terminal agents racing to the same destination. Install both, try them on real tasks for a week each, and let your wrists decide the winner.

End-of-lesson check

6 questions · take it digitally for instant feedback at tendril.neural-forge.io/learn/quiz/end-coding-installing-codex-cli-creators

What is the main idea of "Installing and Using the OpenAI Codex CLI"?
1. Codex CLI is OpenAI's terminal coding agent.
2. Use AI as the final authority for the whole decision
3. Avoid checking the answer once it sounds polished
4. Focus only on speed instead of judgment
Which concept is most central to "Installing and Using the OpenAI Codex CLI"?
1. exec mode
2. Codex CLI
3. codex cloud
4. MCP
What should a careful learner remember about "MCP is first-class here too"?
1. Use "MCP is first-class here too" as a reminder to verify the AI output before anyone relies on it.
2. Skip the context so the tool can guess faster
3. Treat the output as private even after sharing it online
4. Use the answer without checking the source
You want to use AI after this lesson. What is the safest next step?
1. Act immediately because the AI answer is written clearly
2. Use AI for drafting and comparison, but verify before publishing or relying on it.
3. Hide uncertainty so the final answer looks cleaner
4. Use private or sensitive details before checking permission
How should AI output about Codex CLI be treated?
1. As proof that no other source is needed
2. As a replacement for context, consent, or expert review
3. As a draft or helper output that still needs human judgment and verification
4. As something that becomes correct when it sounds confident
Name one way to verify an AI answer about Codex CLI.

← Back to interactive lesson

Tendril · Creators · AI-Assisted Coding

Installing and Using the OpenAI Codex CLI

Codex CLI is OpenAI's terminal coding agent. It runs locally, supports MCP, and ships a codex cloud mode for background tasks. Let's install it and compare it honestly to Claude Code.

45 min · Reviewed 2026

OpenAI's Answer to Claude Code

Install and first run

# Install via npm (macOS, Linux, Windows) npm install -g @openai/codex # Or via Homebrew on macOS brew install openai/codex/codex # Launch in your project directory cd my-project codex # Type /model to pick a model # Default in 2026: gpt-5.5 for complex work, gpt-5.3-codex for fast tasksAs of April 2026, gpt-5.5 is the recommended model for complex work; gpt-5.3-codex is tuned for fast edits.

Two modes you will use

Mode	Command	What it's for
Interactive TUI	codex	Conversational coding, the default experience
Exec	codex exec "<prompt>"	Scripted, non-interactive runs — great for CI
Cloud	codex cloud	Offload long tasks to OpenAI's infra, review locally

A realistic exec workflow

# Automate a recurring task with `codex exec` codex exec "Find all task list comments in src/, group them by file, \ and write a markdown summary to TODO_REPORT.md" # Run in CI after PR checks pass codex exec --model gpt-5.5 "Review the diff against main and \ flag any missing test coverage for changed functions."Exec mode turns Codex into a scriptable tool you can chain with Make, GitHub Actions, or cron.

codex cloud: the superpower

Image input

Claude Code vs. Codex CLI: the honest comparison

Dimension	Claude Code	Codex CLI
Model	Claude family	GPT family
Project memory	CLAUDE.md	AGENTS.md (similar concept)
Parallel agents	Up to 10 subagents	Single-session + cloud offload
Extensibility	Skills, hooks, 25+ lifecycle events	MCP, exec scripts, cloud tasks
Pricing entry	Claude Pro $20/mo	Included in ChatGPT Plus/Pro

The best agent is the one whose workflow matches your brain.
— A polyglot engineer

The big idea: Codex CLI and Claude Code are two terminal agents racing to the same destination. Install both, try them on real tasks for a week each, and let your wrists decide the winner.

End-of-lesson check

6 questions · take it digitally for instant feedback at tendril.neural-forge.io/learn/quiz/end-coding-installing-codex-cli-creators

What is the main idea of "Installing and Using the OpenAI Codex CLI"?
1. Codex CLI is OpenAI's terminal coding agent.
2. Use AI as the final authority for the whole decision
3. Avoid checking the answer once it sounds polished
4. Focus only on speed instead of judgment
Which concept is most central to "Installing and Using the OpenAI Codex CLI"?
1. exec mode
2. Codex CLI
3. codex cloud
4. MCP
What should a careful learner remember about "MCP is first-class here too"?
1. Use "MCP is first-class here too" as a reminder to verify the AI output before anyone relies on it.
2. Skip the context so the tool can guess faster
3. Treat the output as private even after sharing it online
4. Use the answer without checking the source
You want to use AI after this lesson. What is the safest next step?
1. Act immediately because the AI answer is written clearly
2. Use AI for drafting and comparison, but verify before publishing or relying on it.
3. Hide uncertainty so the final answer looks cleaner
4. Use private or sensitive details before checking permission
How should AI output about Codex CLI be treated?
1. As proof that no other source is needed
2. As a replacement for context, consent, or expert review
3. As a draft or helper output that still needs human judgment and verification
4. As something that becomes correct when it sounds confident
Name one way to verify an AI answer about Codex CLI.

← Back to interactive lesson