What are Claude Code, Codex and Gemini CLI?
They are three AI coding agents that run in your terminal. Claude Code is Anthropic's agent CLI, started with claude. Codex is OpenAI's agent CLI, started with codex. Gemini CLI is Google's agent CLI, started with gemini.
Each works the same basic way: you open an interactive session in your project, describe a task in plain language, and the agent reads code, edits files, runs commands such as your tests and reports what it did. Setup guides: Claude Code, Codex and Gemini CLI.
How do Claude Code, Codex and Gemini CLI compare?
On stable, checkable facts the three are close. The table covers only those; anything that changes with each release is left out on purpose.
| Claude Code | Codex | Gemini CLI | |
|---|---|---|---|
| Made by | Anthropic | OpenAI | |
| Command | claude | codex | gemini |
| Install on macOS | npm @anthropic-ai/claude-code or Homebrew cask claude-code | npm @openai/codex or Homebrew cask codex | Homebrew gemini-cli or npm @google/gemini-cli |
| Install on Windows | npm @anthropic-ai/claude-code | npm @openai/codex | npm @google/gemini-cli |
| Sign in | claude auth login | codex login | Sign in with Google on the first interactive run |
| Use an API key | ANTHROPIC_API_KEY | codex login --with-api-key | GEMINI_API_KEY |
| Models | Anthropic's models | OpenAI's models | Google's Gemini models |
| Project instructions file | CLAUDE.md | AGENTS.md | GEMINI.md |
| Reads code, edits files, runs commands | Yes | Yes | Yes |
| View in Tallos | Chat view by default | Chat view by default | Terminal view |
| Usage readout in Tallos | Yes | Yes | Yes |
What do the three agent CLIs have in common?
More than they differ. That makes them easy to swap, mix and compare.
- Same workflow: an interactive terminal session in your project folder.
- Same powers: they change files on disk and run shell commands, so each should work in its own copy of the repo.
- Same controls: each lets you decide how much it may do without asking first.
- Same kind of house rules: each reads a Markdown instructions file from your repo, so you can give all three the same conventions.
- Same billing model for you: each signs in with its own vendor account or API key.
Which is best: Claude Code, Codex or Gemini CLI?
None is best for every repo and task. Output quality depends on your language, codebase, prompt and model settings, and all three tools update often. A ranking published today can be stale next month, so this page does not rank them.
There are still good, concrete reasons a team picks one first:
- The account you already have. Starting with the vendor you already sign in to is the fastest path.
- The model family you prefer. Each CLI runs its own vendor's models.
- Your conventions. If your repo already keeps a
CLAUDE.md,AGENTS.mdorGEMINI.md, the matching agent picks it up with no extra step. - Your review habits. Some developers prefer a chat view for reading an agent's work; in Tallos, Claude Code and Codex open there by default, while Gemini CLI runs in the terminal view.
None of these reasons predicts which agent will do better on your next ticket. For that, you have to run them.
Can I run Claude Code, Codex and Gemini CLI together?
Yes. Tallos runs all three at once on the same repository, each in its own workspace with its own branch, so none of them touches another's files. Each uses your existing subscription or API key; Tallos does not resell model access.
Install and sign-in happen on the Connections page: one card per agent, with the vendor's verified install command, its sign-in or an API key kept in secure storage, and its model list. The key is injected only into that agent's launch environment.
Put Claude Code, Codex and Gemini CLI on the same task today.
How do I decide which agent CLI fits my repo?
Give all three the same real task and compare their diffs. Three agents fit the best-of-three pattern exactly.
- 1
Choose a real task
Take a ticket from your backlog and write down how to verify it, including which tests must pass.
- 2
Create a best-of-three squad
Use the template "3 attempts, pick the best" and set one attempt to Claude Code, one to Codex and one to Gemini CLI.
- 3
Let them work independently
Each attempt runs in its own workspace from the same starting branch.
- 4
Read the leader's recommendation
The leader compares the results and marks one as Recommended, explaining why.
- 5
Check the diffs yourself
Open each workspace's changes: correctness, scope, readability, tests.
- 6
Accept or discard
Nothing merges without your approval. Open the winning workspace to create a pull request.
Repeat on a few different kinds of tasks before settling on a default. The squad version is described in best of three; for the manual version and the broader workflow, see how to run AI agents in parallel. For a two-way view, read Claude Code vs Codex.
Frequently asked questions
Which is better: Claude Code, Codex or Gemini CLI?
No single one is better on every repo and task, and all three change often. The reliable test is to give the same real task to each and compare the diffs.
Who makes Claude Code, Codex and Gemini CLI?
Claude Code is made by Anthropic, Codex by OpenAI and Gemini CLI by Google. All three are AI coding agents that run as command-line tools.
Can I run all three agents on the same repository at once?
Yes. In Tallos each agent works in its own workspace, a separate git worktree on its own branch, so they can run on the same repository simultaneously without overwriting each other.
How do I sign in to Gemini CLI?
Gemini CLI asks you to sign in with Google the first time you run it interactively, or you can set the GEMINI_API_KEY environment variable. In Tallos, the Connections page can store the key and inject it only into Gemini CLI's launch environment.
Do all three work on Windows?
Yes. All three can be installed on Windows with npm, and Tallos runs on Windows 10 or later as well as macOS 13 or later.
Do I need three separate subscriptions?
Each agent signs in with its own vendor using an account or an API key. Tallos works with the accounts you already have and does not sell model access, so you only use the agents you have access to.
Does Tallos support other agent CLIs too?
Yes. OpenCode, Grok CLI, Qwen Code and MiMo Code can also be set up from the Connections page, GitHub Copilot and many other CLIs are detected automatically, and any CLI agent can be added as a custom agent.
