Codex Review 2026: OpenAI's Coding Agent for ChatGPT Subscribers

What Is Codex?

Codex is OpenAI’s dedicated AI coding agent. It launched as a macOS app in February 2026 and is also available as a CLI tool and VS Code extension. Unlike OpenAI’s earlier code-generation models that were embedded in other products, Codex is a standalone coding environment built specifically for software development tasks.

Codex is available to ChatGPT subscribers — if you already pay for Plus, Pro, or Team, you have access. It uses OpenAI’s GPT-Codex model family, which is optimized for code understanding and generation, and offers a 400K token context window.

What It Does

Agentic Code Editing

Codex operates as an autonomous agent. Describe a task — “add input validation to all API endpoints” or “write integration tests for the payment module” — and it reads your codebase, plans the changes, and executes them across multiple files. It handles creating new files, modifying existing ones, updating imports, and running verification steps.

The 400K token context window means it can hold significantly more of your codebase in memory than most competitors. For large projects with many interconnected files, this reduces the “lost context” problem where the AI forgets about relevant code.

Terminal and CLI

The Codex CLI is open source and runs in any terminal. It supports the same agentic workflows as the app — reading files, editing code, running commands — but in a text-based interface. This makes it usable in SSH sessions, CI/CD pipelines, and headless environments.

Code Review and PR Review

Codex can review code changes and pull requests, providing feedback on logic errors, style issues, security concerns, and potential bugs. It reads the diff in context of the full codebase rather than reviewing changes in isolation.

App Generation

The macOS app includes a project creation workflow where you describe what you want to build and Codex scaffolds the project — file structure, dependencies, configuration, and initial code. This is aimed at rapid prototyping.

Pricing

Codex is included in ChatGPT subscription tiers:

Plan	Price	Rate Limits
Free	$0	Limited access (included for limited time)
Go	$8/mo	Standard rate limits
Plus	$20/mo	Higher rate limits
Pro	$200/mo	Highest rate limits, priority access
Team	$30/user/mo	Team features, admin controls
Enterprise	Custom	SSO, IP indemnity, dedicated support

If you already have a ChatGPT subscription, Codex does not add to your bill. The trade-off is that rate limits vary significantly by tier — Free and Go users will hit limits quickly during active development sessions.

Pricing verified February 2026. Check openai.com/pricing for current plans.

Strengths

The 400K context window is a real advantage for large projects. When working on codebases with thousands of files, most AI tools lose track of relevant context. Codex can hold substantially more code in its working memory, which improves the accuracy of cross-file edits and reduces hallucinations about your project structure.

Bundled with ChatGPT subscriptions lowers the barrier to entry. Millions of developers already pay for ChatGPT. Getting a dedicated coding agent at no additional cost removes the “another subscription” friction that slows adoption of tools like Cursor or Windsurf.

The open-source CLI fits into existing workflows. Terminal-first developers can use the CLI alongside their preferred editor without adopting a new IDE. The open-source license means the community can inspect, extend, and contribute to the tool.

Weaknesses

macOS only for the native app. As of February 2026, the desktop app runs only on macOS. Windows and Linux developers are limited to the CLI and VS Code extension, which lack the full app experience.

Still a new product. Codex launched in its current form in early 2026. The feature set, rate limits, and model capabilities are still evolving. Early adopters should expect changes — some features may improve rapidly, while others may be adjusted or removed.

Rate limits create an uneven experience across tiers. The gap between Free ($0) and Pro ($200/mo) is significant. Developers on lower tiers may find themselves throttled during intensive coding sessions, which disrupts flow.

Who It’s For

Codex fits well for:

• Developers already subscribed to ChatGPT Plus, Pro, or Team
• macOS developers who want a native coding agent app
• Teams that want coding assistance bundled with their existing OpenAI subscription
• Developers working on large codebases that benefit from the 400K context window

Codex is a harder sell for:

• Windows and Linux developers who want a native desktop experience
• Developers who want stable, mature tooling (Codex is still early-stage)
• Budget-conscious developers on the Free or Go tier who need high rate limits
• Developers who prefer model flexibility (Codex is tied to OpenAI models)

Sources

• OpenAI Codex
• Codex CLI GitHub Repository
• OpenAI Pricing