Terminal coding agents compared

Claude Code, Codex CLI, Gemini CLI, GitHub Copilot CLI, OpenCode, Cline, goose and Aider compared on license, model access, instruction files, sandboxing, headless mode, MCP and Agent Skills support.

Type

Comparison

Author

Agentica Author

Published

2026-10-02

Last verified

2026-10-02

• coding-agents
• harnesses
• cli
• mcp
• agent-skills
• sandboxing

Comparison

Verdict: Pick by model access first: Claude Code for Claude, Codex CLI for a ChatGPT plan, Gemini CLI for a free tier, Copilot CLI if your org already pays for Copilot, and OpenCode, Cline or goose to bring your own provider. For unattended runs, Codex CLI has the strictest out-of-the-box sandbox; Claude Code's and Gemini CLI's are strong but opt-in, and Cline's CLI auto-approves by default. Aider is still useful for git-centric pair programming but has had no release since August 2025.

What actually differs

All eight read your repository, edit files, run shell commands and loop until the task is done. The differences that matter in practice are narrower than the feature lists suggest:

• How you pay for the model. Claude Code, Codex CLI, Gemini CLI and Copilot CLI are each tied to one vendor's account, which usually means a flat subscription instead of per-token bills. OpenCode, Cline, goose and Aider take any provider key, including local models, and several of them can also reuse a Claude, ChatGPT or Gemini subscription.
• What the sandbox does by default. This is the biggest difference for unattended use, and it's covered below.
• Which instruction file it reads. AGENTS.md has become the common denominator: Codex, OpenCode, Cline and Copilot read it directly, Claude Code reads it alongside CLAUDE.md, and Gemini CLI can be configured to. If you maintain one file for several agents, make it AGENTS.md.
• Extensibility. Every tool here except Aider documents MCP support, and all of them except Aider now load Agent Skills (folders with a SKILL.md), so a skill written once works across most harnesses.

Sandboxing and approvals, read carefully

"Has a sandbox" means very different things:

• Codex CLI sandboxes by default. Commands run under Seatbelt on macOS or bubblewrap on Linux and WSL2 (you install bubblewrap yourself), in workspace-write mode: edits inside the workspace, routine commands, and approval when it needs to go further. danger-full-access with approval policy never removes all limits.
• Claude Code combines permission modes with an OS-enforced Bash sandbox built on Anthropic's open-source sandbox-runtime. It is off by default (/sandbox turns it on). When on, writes are limited to the working directory and network goes through a local proxy with an allowlist that starts empty. Note the documented defaults: sandboxed commands can still read most of the machine, including ~/.ssh and ~/.aws/credentials, until you add denyRead or credential rules, and file tools, MCP servers and hooks run outside the sandbox. Native Windows runs commands unsandboxed; use WSL2.
• Gemini CLI offers the widest choice of backends (Seatbelt, Docker, Podman, gVisor, LXC) but only when you pass -s or set GEMINI_SANDBOX.
• Copilot CLI relies on tool approvals (--allow-tool='shell(git)') and added local and cloud sandboxes, both in public preview.
• OpenCode uses allow, ask and deny rules per tool and per command pattern, plus a read-only plan agent. No OS-level sandbox was documented in the pages used here.
• Cline's CLI starts a prompt in act mode with auto-approve on by default (--auto-approve false to change that). Fine inside a container; risky on your workstation.
• Aider has no sandbox; its safety net is that every edit is a git commit you can undo.

For unattended runs in CI, or anywhere the agent reads untrusted input such as issues, web pages or dependencies, run the harness itself inside a disposable environment. The sandboxing guide and code sandboxes comparison cover the options.

Recent changes worth knowing

• Codex CLI removed codex mcp-server and the standalone codex-mcp-server binary; integrations must move to the Codex app server's own JSON-RPC protocol. The untrusted approval policy is retired, custom prompts are deprecated in favor of skills, and the docs moved to learn.chatgpt.com.
• Claude Code's npm package is deprecated as an install method; use the native installer, Homebrew or WinGet. Claude Code now reads AGENTS.md.
• Copilot CLI bills by AI credits consumed per token rather than per request, and combines all instruction files instead of picking one by priority.
• goose moved from Block to the Agentic AI Foundation at the Linux Foundation; the repository is now aaif-goose/goose.
• OpenCode's repository is anomalyco/opencode, and its site announces OpenCode v2.
• Aider's last tagged release is v0.86.0 from 2025-08-09, and its README still recommends models from early 2025.

Not in this table

Cursor (an IDE with a CLI), Amp, Kiro, Qwen Code (a Gemini CLI fork for Qwen models) and OpenHands are also strong options, but they weren't re-verified for this page. To set up any of these harnesses with tools, see the coding agent starter stack and the guide to adding MCP servers to Claude Code.

Directory entries in this comparison

• Claude Code: Anthropic's agentic coding tool that reads your codebase, edits files, runs commands and integrates with dev tools; available in terminal, IDE, desktop and browser.
• OpenAI Codex CLI: OpenAI's lightweight open-source coding agent that runs in your terminal.
• Gemini CLI: Open-source AI agent from Google that brings Gemini models directly into your terminal.
• GitHub Copilot CLI: Brings GitHub Copilot's coding agent to your terminal to read, write and run code where you work.
• OpenCode: The open-source AI coding agent, built for the terminal.
• Cline: Open-source autonomous coding agent available as an SDK, IDE extension or CLI, with Plan/Act modes and MCP integration.
• goose: Open-source, extensible AI agent (desktop app, CLI and API) that can install, execute, edit and test with any LLM.
• Aider: Open-source AI pair programming in your terminal.
• AGENTS.md: Simple, open format for guiding coding agents: a README for agents placed in your repo.
• Agent Skills Specification: Open format for packaging agent capabilities as folders with a SKILL.md (YAML frontmatter + instructions) plus optional scripts and resources.
• Model Context Protocol (MCP): Open protocol that standardizes how AI applications connect to external tools, data sources and prompts via MCP servers.
• Cursor: AI code editor and coding agent with Agent mode, Rules, Skills, MCP servers and a CLI.
• Amp: Coding agent and development environment; run agents unsupervised in cloud orbs or locally with the CLI.
• Kiro: Agentic engineering environment that turns prompts into executable specs and builds across large codebases with parallel agents.
• Qwen Code: Open-source AI coding agent for the terminal from the Qwen team.
• OpenHands: Open-source, model-agnostic platform for cloud coding agents.

Related

• Coding agent starter stack (Stack)
• Add MCP servers to Claude Code (Guide)
• Connect an agent to a remote MCP server (Guide)
• Run agent-generated code safely in a sandbox (Guide)

Sources

• Claude Code docs, Set up Claude Code, accessed 2026-10-02
• Claude Code docs, Configure the sandboxed Bash tool, accessed 2026-10-02
• Claude Code docs, Memory (CLAUDE.md and AGENTS.md), accessed 2026-10-02
• Claude Code docs, Run Claude Code programmatically, accessed 2026-10-02
• anthropics/claude-code repository and LICENSE, accessed 2026-10-02
• openai/codex repository, accessed 2026-10-02
• Codex docs, Sandbox, accessed 2026-10-02
• Codex docs, Codex MCP server removal, accessed 2026-10-02
• Codex docs, Pricing, accessed 2026-10-02
• Codex docs index (llms.txt), accessed 2026-10-02
• google-gemini/gemini-cli repository, accessed 2026-10-02
• Gemini CLI docs, Sandboxing, accessed 2026-10-02
• GitHub Docs, About GitHub Copilot CLI, accessed 2026-10-02
• GitHub Docs, Adding custom instructions for Copilot CLI, accessed 2026-10-02
• github/copilot-cli repository, accessed 2026-10-02
• OpenCode docs, Rules, accessed 2026-10-02
• OpenCode docs, Providers, accessed 2026-10-02
• OpenCode docs, Permissions, accessed 2026-10-02
• OpenCode docs, CLI, accessed 2026-10-02
• cline/cline repository, accessed 2026-10-02
• Cline docs, Cline Rules, accessed 2026-10-02
• Cline docs, CLI reference, accessed 2026-10-02
• aaif-goose/goose repository, accessed 2026-10-02
• goose docs, Using skills, accessed 2026-10-02
• goose docs, CLI commands, accessed 2026-10-02
• Aider-AI/aider repository, accessed 2026-10-02
• Aider docs, Specifying coding conventions, accessed 2026-10-02
• Aider docs, Options reference, accessed 2026-10-02

Machine-readable

• JSON
• Markdown
• Source on GitHub