Codex
Reviewedbyfl
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Codex is OpenAI's coding agent. It runs in a terminal, as an editor extension and in the cloud, so a task can be worked through step by step or handed off to finish on its own.
Codex is OpenAI's coding agent, released in 2025. It is distinct from the earlier Codex API (deprecated in 2023), which was the model behind the original GitHub Copilot. The current Codex is a cloud agent that runs inside a sandboxed environment with access to your repository, a terminal, and the internet.
How it works
Codex runs where the work is. The CLI works interactively in a terminal against the local checkout, an extension puts the same agent inside VS Code and its forks, and Codex cloud takes a fully specified task — a feature to add, a bug to fix, a refactor to perform — clones the repository into a sandbox, runs commands, edits files and returns a pull request or a patch.
Cloud tasks run in parallel and report back when done, which is closer to delegating to a background worker than to pairing. The terminal and editor surfaces cover the back-and-forth sessions that model does not suit.
Agentic capabilities
Codex can read and modify code, run tests, install dependencies, and browse documentation. It is designed for tasks that can be fully specified upfront. It is less suited to exploratory, back-and-forth sessions where you iterate on a result in real time.
Access
Codex comes with the paid ChatGPT plans and is also reachable through the OpenAI API. Usage limits depend on the tier. The CLI, the editor extension and the cloud share one account.
Privacy
Code is sent to and executed on OpenAI's infrastructure. OpenAI states that API inputs are not used to train models by default. Review OpenAI's usage policies before using Codex with sensitive or proprietary codebases.
Integration with fortrabbit
The Codex CLI registers the MCP server with one command. It carries an explicit client ID, which older Codex releases need and current ones ignore:
The agent skills install into ~/.agents/skills and carry what MCP does not: deployments, database sync, guided environment setup. The frbit CLI sets up both in one step with frbit setup agent.