Comparison

Gemini CLI vs OpenAI Codex CLI

Gemini CLI vs OpenAI Codex CLI in 2026: Google's free open-source terminal agent vs OpenAI's open-source terminal agent. Pricing, models, MCP, skills, free tier, head to head.

Short answer

Gemini CLI is Apache 2.0 open-source with the most generous free tier (60 req/min, 1000 req/day) and Gemini 2.5 Pro / 3.5 Flash with 1M+ context. OpenAI Codex CLI is Apache 2.0 open-source bundled with ChatGPT Pro/Plus and powered by GPT-5 / GPT-5.5. Pick Gemini CLI for free unlimited light use; pick Codex if you're already on the OpenAI stack.

Gemini CLI

Google

Free open-source terminal agent powered by Gemini

Best for: Devs who want a free Apache 2.0 terminal agent with generous quotas and Google's 1M+ context models.

Visit Gemini CLI →

OpenAI Codex CLI

OpenAI

Apache 2.0 terminal agent on the OpenAI stack

Best for: Devs on ChatGPT Pro/Plus who want an open-source terminal agent powered by GPT-5/5.5.

Visit OpenAI Codex CLI →

Feature comparison

License

Gemini CLIApache 2.0
OpenAI Codex CLIApache 2.0

Default model

Gemini CLIGemini 2.5 Pro / 3.5 Flash
OpenAI Codex CLIGPT-5 / GPT-5.5

Context window

Gemini CLIEdge1M+ (some configs 2M+)
OpenAI Codex CLI1M

Free tier

Gemini CLIEdgeGenerous (60 req/min, 1000/day)
OpenAI Codex CLIChatGPT free tier (limited)

Paid tier

Gemini CLIVertex AI / Google AI Studio (pay-per-token)
OpenAI Codex CLIBundled with ChatGPT Pro/Plus

MCP support

Gemini CLINative
OpenAI Codex CLINative

Skills (SKILL.md)

Gemini CLIVia skills-hub MCP
OpenAI Codex CLIEdgeNative via codex.toml

Agent autonomy

Gemini CLIStrong terminal agent
OpenAI Codex CLIStrong terminal agent

Sub-agents / scheduled tasks

Gemini CLINot native
OpenAI Codex CLINot native

Pick Gemini CLI when

  • →You want a generous free tier (60 req/min, 1000/day)
  • →You need very long context (1M+ tokens default, 2M+ in some configs)
  • →You're on the Google / Vertex AI stack
  • →You don't want a paid subscription to start

Pick OpenAI Codex CLI when

  • →You're on ChatGPT Pro/Plus already
  • →You want native SKILL.md support via codex.toml
  • →You prefer GPT-5 / GPT-5.5 as the default model
  • →You want the OpenAI ecosystem integration

Verdict

Both are Apache 2.0 terminal agents from the major frontier model providers. Gemini CLI wins on free tier and context window. Codex CLI wins on native SKILL.md support and ChatGPT bundling. Many devs run both, Gemini CLI for free exploration, Codex when on ChatGPT-funded production work.

Frequently asked questions

Are both truly free?

Gemini CLI is free for individual use with generous quotas. Codex CLI is free to install but you need a ChatGPT Pro/Plus subscription ($20/mo+) or pay-per-token via the OpenAI API.

Which has better agent autonomy?

Comparable. Both run multi-step terminal agents with full repo access. Neither has sub-agents or scheduled tasks, Claude Code is the leader on those.

Can I use the same skills in both?

Yes via MCP. Connect either to the skills-hub MCP server and the 4,900+ skill catalog appears as MCP prompts.

Which has longer context?

Gemini CLI, Gemini 2.5 Pro defaults to 1M+ and some configurations expose 2M+. GPT-5 / 5.5 in Codex is 1M.

What about Claude Code or Aider?

Claude Code is the proprietary autonomy leader (sub-agents, scheduled tasks). Aider is the longest-running open-source CLI with git-aware auto-commits. See our comparisons for details.

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Install skills that work in both

Skills follow the open Agent Skills standard, install once, use in any AI tool.

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