The Codex plugin inside Claude Code: what it is and when it pays off
Short answer: it is an official OpenAI plugin that lets you call Codex without leaving Claude Code, mainly for code review and delegating tasks. Three commands to install, runs on your ChatGPT account (the free one works) and it is Apache-2.0. Worth it when you want a second opinion on something specific; not worth it when you want both AI agents working in parallel.
What the plugin does
Per the official repository (openai/codex-plugin-cc), it brings into Claude Code: ordinary code review, adversarial review (where Codex questions design decisions rather than just flagging errors), task delegation to Codex, session handoff and background job management.
Claude Code stays the place you work. Codex comes in as the one being called.
How to install
/plugin marketplace add openai/codex-plugin-cc\n/plugin install codex@openai-codex\n/reload-plugins\n/codex:setupRequires Node 18.18 or newer, Codex installed and authenticated locally (npm install -g @openai/codex), and a ChatGPT account or an API key.
When it is the right call
When you want a second opinion on something specific, without switching windows or re-explaining context. Adversarial review is the best reason to install it: asking whoever wrote the code to find its own mistake is asking them to see what they missed while writing, and a model from another company genuinely disagrees.
When it does not solve your problem
When you want both working at the same time, on different fronts. The plugin is a caller and callee relationship: one asks, the other answers, and the first one waits. For two fronts running in parallel you need two real AI agents, each with its own session, terminal and file isolation.
They are complementary, and it is worth knowing which of the two you want before installing either.
Does it replace an app with a panel?
No, and it does not try. The plugin solves "I want Codex's opinion right now"; a panel solves "I have six agents open and no idea which one is waiting on me". If yours is the second, the plugin changes nothing.
Do I need two paid subscriptions?
For the plugin, not necessarily: the README says the free ChatGPT account works. To run Codex as an independent AI agent on serious continuous work, the paid account matters for usage limits. Worth starting free and seeing whether the limit bites.
What about the other direction?
People are building the reverse, calling Claude from inside Codex, but not with an official plugin. If you want both as equals rather than one inside the other, the path is running both command line tools side by side, each in its own terminal, over the same repository.