Codex vs Gemini CLI
Two open-source terminal agents from OpenAI and Google. Codex also hands tasks to the cloud and returns a pull request; Gemini CLI stays in the terminal and bets on holding a lot of the project at once.
Published
Codex
The same terminal loop, plus a mode where you hand over a task and get back a pull request.
Pick it if
- Your work splits into well-specified chunks you can describe up front
- You already review other people's code and are comfortable judging a diff cold
- You want work happening while you are doing something else
What will annoy you
Two modes means two mental models. In the remote one there is no conversation to rescue a vague request — you find out at the end.
Gemini CLI
A terminal agent, open source, that competes on how much of your project it holds at once.
Pick it if
- Your problems are spread across files that only make sense together
- You are working in a codebase you did not write and need it mapped
- You want to read the agent's own source when you wonder what it does with your prompt
What will annoy you
A large window invites lazy prompting, and lazy prompting is punished at every size. Google also ships coding help under several names, and the line has moved: for unpaid-tier and Google One accounts, Google has replaced Gemini CLI with Antigravity CLI, and the Gemini CLI README points to Antigravity for the newest Gemini models. Check which one your account gets before you install.
What is the same
- Both run in a terminal, pointed at a project folder
- Both CLIs are open source, so you can read what the agent does with your prompt
- Both take project instructions from a Markdown file: AGENTS.md for Codex, GEMINI.md for Gemini CLI unless you configure it to read AGENTS.md
- Learn one and you can drive the other the same day
Will you hand tasks off, or stay in the terminal the whole time?
Codex treats handing work over as one of its main modes: describe a task, it runs in the cloud and comes back as a pull request, and the same agent sits in your terminal and editor for everything else. Gemini CLI stays in the terminal and competes on how much of the project it can consider at once. Check your account before anything else: for unpaid-tier and Google One accounts, Google has replaced Gemini CLI with Antigravity CLI, and the Gemini CLI README points to Antigravity for the newest Gemini models. If that is your account, the comparison you actually need is Codex against Antigravity CLI.
Still undecided?
Then the honest answer is that either will do, and the two weeks you spend using one will teach you more than another comparison. Both of these are the same shape underneath — give context, read the diff, iterate — so the one you learn transfers to the other in an afternoon.
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More comparisons
No model versions, prices or benchmark scores on this page — they are wrong within weeks and decide nothing durable. For what each vendor shipped most recently, we keep agents-compared, where a weekly job maintains the dated part.