Four tools now fight for the same square of screen: your terminal. Claude Code, OpenAI Codex CLI, Google Gemini CLI, and OpenCode all promise the same thing — an AI agent that reads your codebase, edits files, runs commands, and ships features while you sip coffee. They are not interchangeable, and picking wrong costs you either money or hours.
This is the practical comparison: what each one installs as, what it costs, how it handles subagents and skills, and — the part most roundups skip — which one to actually reach for on a given task.
As of June 2026, the terminal is where the most capable AI coding happens. The editor plugins (Cursor, Copilot) are great, but the agents that run for an hour unattended live in the CLI. One important caveat up front: Google is retiring Gemini CLI for consumer users on June 18, 2026 — more on that below.
A terminal AI coding agent is a command-line tool that runs an autonomous LLM agent inside your shell. It reads and writes files across your repo, executes shell commands and tests, and works through multi-step tasks from a single natural-language prompt — no editor, no GUI, just your terminal.
- Claude Code — best overall for complex, multi-file work. Highest benchmark scores, richest ecosystem (Agent Teams, Skills, MCP). Costs $20–200/mo.
- Codex CLI — best value if you already pay for ChatGPT. Fastest startup, ~4x more token-efficient, included free with any paid plan.
- Gemini CLI — biggest context window (1M tokens) and a real free tier, but being replaced by Antigravity CLI on June 18, 2026 for consumer users.
- OpenCode — best open-source pick. Model-agnostic (Claude, GPT, Gemini, local), free software, no lock-in. ~161K GitHub stars.
- Most developers run a stack of two, not one: a premium agent for hard tasks plus a free one for everything else.
Which terminal AI agent should you pick?
Skip to the answer. Here's the one-line verdict for each, then the detail below.
- Pick Claude Code if you do gnarly multi-file refactors, want the best instruction-following, and don't mind paying for it. It is the one that most often gets a hard task right on the first try.
- Pick Codex CLI if you already have a ChatGPT subscription. It's effectively free, it's the fastest to start, and it burns the fewest tokens. Strongest on focused, single-file, intent-driven edits.
- Pick Gemini CLI if you need to hold an entire monorepo in context or want live Google Search grounding — but only if you're a paid Google AI user, because the free version is being sunset.
- Pick OpenCode if you want model freedom, hate vendor lock-in, or need to route through local/cheaper models. It's the open-source default and the most active project of the four.
Terminal AI coding agents compared (2026)
| 🥇 Claude Code | Codex CLI | Gemini CLI | OpenCode | |
|---|---|---|---|---|
| Maker | Anthropic | OpenAI | Open source (SST) | |
| Install | npm i -g @anthropic-ai/claude-code |
npm i -g @openai/codex |
npm i -g @google/gemini-cli |
npm i -g opencode-ai |
| Models | Claude (Opus/Sonnet/Haiku) | OpenAI (GPT/o-series) | Gemini 3.x | 🟢 Any provider (BYO key) |
| Pricing | $20–200/mo or API | Free w/ ChatGPT plan + API | Free tier or AI Pro/Ultra | Free software, pay API |
| Context window | 200K tokens | 128K–200K | 🟢 1M tokens | Depends on model |
| SWE-bench Verified | 🟢 80.9% | 69.1% | 63.8% | Depends on model |
| Subagents | ✅ Agent Teams | ✅ | ✅ @codebase-investigator | ✅ background agents |
| Skills / plugins | 🟢 2,810+ skills, huge marketplace | ✅ Skills marketplace (2026) | ✅ Extensions | ✅ MCP + agents |
| Built in | — | Rust (fast startup) | — | TypeScript |
| Long-term risk | 🟢 Low | 🟢 Low | 🔴 CLI sunset June 2026 | 🟢 Low (open source) |
Benchmark figures: SWE-bench Verified scores per CodeAnt's 2026 CLI benchmark; context windows per vendor docs.
Claude Code: the one that gets hard tasks right
Claude Code is Anthropic's terminal agent, and as of 2026 it's the most-used AI coding tool, having overtaken Copilot and Cursor in under a year. If you only learn one of these four, this is the safe default.
Install it with npm:
npm install -g @anthropic-ai/claude-code
claude
Why it wins on quality. Claude Code scores 80.9% on SWE-bench Verified — the highest of the three big-name CLIs (per CodeAnt's 2026 benchmark). In a real Express.js refactor benchmarked by Particula Tech, it finished in 1h 17m with zero human interventions, beating Codex (1h 41m) and Gemini (2h 04m, 3 corrections). It uses agentic search to understand your whole repo without you hand-picking context.
The ecosystem is the moat. Claude Code has the richest extension story of any terminal tool:
- Agent Teams — orchestrate multiple subagents on one task
- Agent Skills — markdown instruction sets that load contextually (drop them in
~/.claude/skills/) - MCP — connect external tools and data sources
- Community marketplaces list 2,810+ skills, 425 plugins, and 200 agents (per claudemarketplaces.com)
Pricing: $20/mo (Pro), $100–200/mo (Max), or pay-as-you-go via API key. Opus is the flagship model and the default on Max as of April 2026.
Codex CLI: the best value if you're already on ChatGPT
OpenAI Codex CLI is the dark-horse value play. It's open source, rebuilt in Rust for speed, and — the killer feature — it's included with any paid ChatGPT plan at no extra charge.
npm install -g @openai/codex
codex
Why it's the value king. If you pay $20/mo for ChatGPT Plus, Codex is already in your subscription. It's included across Free, Go, Plus, Pro, Business, Edu, and Enterprise plans. There's no separate Codex subscription to buy; heavy users can top up with credits when they exceed plan limits. As of April 2026, overage billing shifted to API-style token rates.
Where it's strongest. Codex is the fastest to start and the most efficient — it uses roughly 4x fewer tokens than Claude Code on equivalent tasks. It scores 77.3% on Terminal-Bench 2.0, the highest of the three on a benchmark built specifically for terminal agents (versus general software engineering). Its kernel sandbox enables genuine full-auto execution, so you can let it run without babysitting every command.
Best for intent-driven, focused work: "fix this function," "add tests for this module," "wire up this endpoint." On a tightly-scoped task it's quick and cheap.
Gemini CLI: biggest context, but on borrowed time
Google Gemini CLI has two genuine superpowers: a 1M-token context window (3–4 million characters — an entire mid-sized codebase, no chunking) and Google Search grounding, which lets it pull live web data mid-task. No other CLI matches that combination.
npm install -g @google/gemini-cli
gemini login
gemini
The free tier is genuinely generous: 60 requests/minute and 1,000 requests/day with a personal Google account, no API key required. Paid tiers (Google AI Pro, Ultra) raise that to 1,500–2,000 requests/day. It has solid subagents out of the box — @codebase-investigator, @browser-agent — plus installable extensions (gemini extensions install @playwright/mcp).
So what's the catch?
Gemini CLI's benchmark numbers also trail: 63.8% on SWE-bench Verified, and it needed 3 corrections in the Express.js refactor test where Claude Code needed none. The huge context window is real and useful, but raw reasoning on hard tasks is a notch below.
OpenCode: the open-source agent that doesn't care which model you use
OpenCode is the one to watch. It's a fully open-source, model-agnostic terminal agent — point it at Claude, GPT, Gemini, DeepSeek, Grok, or a local Ollama model, and bring your own API keys. As of mid-2026 it sits at roughly 161K GitHub stars (more than Claude Code's 124K) with ~1.38M npm downloads a week, and it once hit #1 on Hacker News.
npm install -g opencode-ai
# or: brew install opencode
opencode
Why people love it. Zero vendor lock-in. The software is free — you pay providers directly for tokens, or run free-tier and local models for nothing. It has a polished terminal UI plus a full desktop app, and Desktop v2 added background agents that match Claude Code's always-on workflow. It supports multi-file edits, codebase search, shell execution, MCP, and subagents.
The reason to choose it isn't raw benchmark scores — those depend on whichever model you plug in. It's control: cost control (route cheap tasks to cheap models), privacy (run local models), and freedom (no single vendor can change your terms overnight).
Pricing: what each one actually costs
| Tool | Entry cost | How you pay | 🆓 Free path |
|---|---|---|---|
| Claude Code | $20/mo (Pro) | Subscription or API key | API trial credits only |
| Codex CLI | $0 extra | Bundled with any paid ChatGPT plan | ✅ Included with ChatGPT |
| Gemini CLI | $0 | Google account free tier | ✅ 1,000 req/day (until June 18) |
| OpenCode | $0 software | Pay model providers directly | ✅ Use local/free-tier models |
The honest math: if you already pay OpenAI, Codex is free money. If you want the best results regardless of cost, Claude Code. If you want to spend nothing and don't mind setup, OpenCode with a free-tier or local model. Gemini CLI was the easiest free start, but its consumer sunset makes it a risky new bet.
Which one for which task?
This is the part that matters. The benchmarks point to clear specialists.
| Your task | Best pick | Why |
|---|---|---|
| Complex multi-file refactor | 🥇 Claude Code | Highest first-pass correctness, zero-intervention runs |
| Focused single-file edit | Codex CLI | Fast, cheap, token-efficient on scoped work |
| Understand a giant monorepo | Gemini CLI* | 1M-token window holds the whole thing |
| Task needing live docs/web data | Gemini CLI* | Google Search grounding is unmatched |
| Cost-sensitive / high-volume work | OpenCode | Route to cheap or local models |
| Privacy / offline / self-hosted | OpenCode | Run local Ollama models, no data leaves your machine |
| Already paying for ChatGPT | Codex CLI | Zero marginal cost |
| Best results, budget is no object | Claude Code | Top quality and ecosystem |
* Factor in the June 18, 2026 consumer sunset — for new long-term setups, prefer Antigravity CLI or a paid Gemini tier.
A lot of developers run two of these at once: a premium agent (Claude Code or Codex) for the hard stuff, and a free one (OpenCode with a local model, or Gemini's free tier) for routine edits and quick questions. Industry surveys in 2026 found most developers run a three-tool stack rather than committing to one — the CLIs are cheap or free enough that mixing is the norm.
Frequently Asked Questions
What is the best terminal AI coding agent in 2026?
Claude Code is the best overall for complex multi-file work, scoring 80.9% on SWE-bench Verified. But Codex CLI is the better value if you already pay for ChatGPT, Gemini CLI has the largest context window (1M tokens), and OpenCode is the top pick if you want an open-source, provider-agnostic tool.
Is Gemini CLI being discontinued?
Yes, for consumer users. Google is replacing Gemini CLI with Antigravity CLI on June 18, 2026 for free, Google AI Pro, and Ultra tiers. API-key and paid Code Assist users are less affected, but new users should weigh this before adopting it.
Which terminal AI agent is free?
Codex CLI is included with any paid ChatGPT plan ($20/mo Plus and up) at no extra cost. Gemini CLI has a genuinely free tier (1,000 requests/day with a Google account). OpenCode is free software — you only pay for the API tokens you use.
Can OpenCode use a Claude Pro or Max subscription?
No, not as of 2026. In January 2026 Anthropic blocked third-party tools from using Claude subscription credentials. To run Claude models inside OpenCode you must use a pay-as-you-go Anthropic API key.
Claude Code vs Codex CLI: which is faster?
Codex CLI starts faster (it is built in Rust) and uses roughly 4x fewer tokens per task, but Claude Code finished a benchmark Express.js refactor in 1h 17m with zero interventions versus Codex's 1h 41m. Codex wins on raw speed and cost; Claude Code wins on getting it right the first time.
What's Next
- 🧠 Master your pick: dig into the Claude Code Workflow Guide to get the most out of the strongest all-rounder.
- 🔌 Go deeper on Codex: the OpenAI Codex CLI guide covers setup, sandboxing, and config.
- 🪐 Plan for the Gemini shift: read the Google Antigravity review before the June 18 CLI sunset.
- 🧩 Feed your agent context: context engineering techniques make any of these four noticeably smarter.
- 🆚 Comparing editors, not CLIs? See Cursor vs Copilot vs Claude Code vs Windsurf.
Choosing a terminal agent is half the battle — getting a repeatable workflow around it is the other half. Start with the Claude Code Workflow Guide, and if you're rolling AI agents out across a team, the AI-Assisted Engineering Playbook covers the patterns that keep AI-written code from becoming tomorrow's mess.