How Good Is Codex? 2026 Review of OpenAI’s Coding Agent (Plan Mode, CLI, Pricing)

By Satish · Last updated: November 1, 2026 · Based on OpenAI’s own Codex documentation and pricing pages plus Google’s official announcement, all read this month. No hands-on benchmark testing is claimed, and vendor benchmark numbers are left out on purpose.

Contents

• What Codex is
• Where you can use it: CLI, IDE, app
• Does Codex have a plan mode?
• Does Codex have a CLI?
• Codex pricing and which plans include it
• Does Gemini have a Codex equivalent?
• Pros and cons
• Who should use Codex
• FAQ

What Codex is (and what “good” should mean)

Codex is an AI coding agent from OpenAI. Instead of only suggesting code in a chat box, it works inside a project: it inspects local files, makes edits and runs tools that are already installed on your machine. That is the right way to judge it. A coding agent is “good” if it understands your repository, changes the right files, explains what it did and makes it easy to undo mistakes.

OpenAI’s own guidance supports that last point. Its CLI page recommends creating Git checkpoints before and after a task so you can revert changes, which is good practice with any agent.

Where you can use Codex

New to the editor route? See our step-by-step guide on how to add a project to Codex in VS Code and the general guide to adding and using a project in Codex.

Does Codex have a plan mode?

Yes. OpenAI’s slash-command reference lists /plan as a command available from the app composer. The point of plan mode in any coding agent is the same: you ask the agent to lay out what it intends to do before it touches your files, so you can correct the approach first. The official page names the command but does not describe the behavior in detail, so check the current slash-command reference in your own version before relying on specifics.

Related controls that are documented: /permissions in the CLI controls when Codex can edit files or run commands without asking, and the --sandbox flag selects read-only, workspace-write or danger-full-access. For safe first runs, start with the most restrictive setting.

Does Codex have a CLI?

Yes, and it is the most complete surface. According to OpenAI’s CLI page it supports:

• Interactive coding in the terminal, including exploring code, planning and editing changes, and running local dev tools
• codex resume to reopen recent chats
• codex --image to add visual context
• codex --search for live web search
• codex cloud to submit work to cloud environments and apply results locally
• codex mcp to connect MCP servers
• codex exec for non-interactive scripting and CI
• Code review of uncommitted changes, a commit or a base branch without modifying your working tree
• Skills, plugins and subagents

Useful flags from the CLI reference: --cd sets the working directory before starting, --add-dir grants write access to extra directories, --model overrides the configured model, and --ask-for-approval controls when Codex pauses for you.

Codex pricing: which plans include it?

OpenAI’s pricing page states that Codex is included in ChatGPT Free, Go, Plus, Pro, Business, Edu and Enterprise plans. The listed plan prices are:

Usage limits move often. OpenAI describes message limits per five-hour window and says weekly limits may also apply, and the numbers on its pages have changed between versions. Treat any number you read, including third-party tables, as an estimate and check the live pricing page before you pick a plan.

Does Gemini have a Codex equivalent?

Google’s closest answer used to be Gemini CLI, but Google announced on May 19, 2026 that it is retiring Gemini CLI and moving to Antigravity, an agent-first development platform. Antigravity CLI is the new terminal tool: built in Go, able to run multiple background agents, and keeping Agent Skills, Hooks, Subagents and extensions (now called Antigravity plugins), though Google notes it does not have full feature parity at launch.

Per the announcement, from June 18, 2026 Gemini CLI and the Gemini Code Assist IDE extensions stopped serving Google AI Pro and Ultra subscribers and free Gemini Code Assist for individuals users. Enterprise customers on Gemini Code Assist Standard or Enterprise were not affected. So in late 2026 the Google counterpart to the Codex CLI is Antigravity CLI, not Gemini CLI.

Pros and cons of Codex

Pros

• One agent across terminal, editor and desktop app, all tied to your ChatGPT sign-in
• Included in every ChatGPT plan, including Free, so you can try it at no cost
• Safety controls: sandbox modes, approval settings and Git-friendly workflow
• Automation features (codex exec, MCP, cloud tasks) beyond simple chat

Cons

• Usage limits and model names change often, so budgeting is harder than for fixed-price tools
• Full-power use on Pro or API billing costs more than light plans
• Plan mode and some features are documented only briefly in the official pages
• Agents still make mistakes; you must review diffs

Who should use Codex?

• Solo developers and freelancers already paying for ChatGPT Plus: start in the VS Code extension.
• Terminal-first developers who want scripting and CI: use the CLI and codex exec.
• Teams that need admin controls: look at Business or Enterprise.
• Google-centric teams should compare it directly with Antigravity CLI before committing.

How good is Codex? The verdict

So, how good is Codex in practice? It is a strong choice if you want an agent that works inside a real project with safety controls, and it is easy to try because it is included in every ChatGPT plan. How good is Codex for you depends on your task, your plan limits and how carefully you review its changes.

If you are still asking how good is Codex compared with Google’s tools, remember that Gemini CLI is being replaced by Antigravity CLI. Start with a small task, check the diff and decide for yourself how good Codex is for your workflow.

Related guides: Add a project to Codex in VS Code · Add and use a project in Codex · CodexBar: track Codex usage · Best AI tools for work

Sources, as read in November 2026: OpenAI’s Codex documentation for the CLI, IDE extension, desktop app and pricing; Google Developers Blog on the Gemini CLI to Antigravity CLI transition.

How good is Codex: frequently asked questions

How good is Codex for coding in 2026?

Codex is a capable agent that works inside real projects across a CLI, editor extensions and a desktop app. Its quality depends on your task and the model your plan gives you, so test it on a small real task and review the diff.

Does Codex have a plan mode?

Yes. OpenAI lists a /plan command in its slash-command reference.

Does Codex have a CLI?

Yes. Run codex in a project directory after installing it; the installer command for macOS and Linux is on OpenAI’s CLI page.

Does Gemini have a Codex equivalent?

Google is retiring Gemini CLI and replacing it with Antigravity CLI, which is the nearest equivalent to the Codex CLI.

Is Codex free?

Codex is included in the ChatGPT Free plan with limited use, and in paid plans with more usage. API-key use is billed at API pricing.

Can I use Codex in VS Code?

Yes. Install the Codex extension (openai.chatgpt) in VS Code, Cursor, Windsurf or VS Code Insiders.

Is Codex safe to run on my files?

It has sandbox and approval controls, but you should work in a Git repository, start with restrictive permissions and review every change.