AI coding agents compared: how they differ and how to choose

An AI coding agent works inside a real project: it reads the code, edits files and runs commands to get a task done. There are now enough of them that the differences matter more than the likeness: where an agent runs, whose models it uses, how you pay for it, and how it learns your project and remembers it.

This guide puts nine of them side by side, in alphabetical order. It keeps to what each maker publishes about its own product and leaves out rankings, benchmarks and prices, which change too often to stay true.

We make Nilux, one of the nine. Everything about the other eight comes from their makers' own documentation, read on October 28, 2026; the sources are listed at the end. If something here has changed, write to support@nilux.dev and we will correct it.

At a glance

Aider

Aider is an open-source (Apache 2.0) AI pair programmer for the terminal, from the Aider-AI project. It connects to most LLM providers, including local models through Ollama or LM Studio, and you bring your own API keys. Besides the command line it offers a browser UI and a watch mode that answers comments you write in your editor.

Coding conventions go in a Markdown file such as CONVENTIONS.md, loaded with /read or --read, or every time through read: in .aider.conf.yml. Aider documentation

Claude Code

Claude Code is Anthropic's coding agent. It runs in the terminal on macOS, Linux and Windows, in VS Code and JetBrains IDEs, in a desktop app, on the web and in the Claude mobile app, and it also works from Slack, in Chrome and in CI through GitHub Actions or GitLab. It uses Anthropic's Claude models. Most of these need a Claude subscription or an Anthropic Console account; the terminal and the IDE extensions can also use third-party cloud providers.

Instructions go in CLAUDE.md files: the project's (shared through the repository), your own in ~/.claude/CLAUDE.md, and one an organization deploys to every machine, plus private notes in CLAUDE.local.md. Rules can be split into .claude/rules/, each loaded only for the paths it names, and files can be imported with @. An AGENTS.md already in the repository can be read in place of CLAUDE.md. Auto memory adds notes Claude writes itself as it works and reads in later sessions. Claude Code documentation

Cline

Cline is an open-source (Apache 2.0) coding agent from Cline Bot Inc. It runs as a VS Code extension, also in editors built on VS Code such as Cursor and Windsurf, as a JetBrains plugin, in Zed and Neovim, and as a CLI and a desktop app for macOS and Windows. It works with many providers, among them Anthropic, OpenAI, Google, OpenRouter and AWS Bedrock, and with local models through Ollama or LM Studio. You use your own credentials, or a Cline account billed by usage or by a monthly plan.

Rules live in .clinerules/ (or .cline/rules/) in the project and in a global rules folder; a rule can be limited to chosen paths, and each can be switched off. Cline also picks up an AGENTS.md, .cursorrules or .windsurfrules it finds. For memory between sessions, its documentation describes a Memory Bank: Markdown files in the project that Cline reads and updates. Cline documentation

Codex

Codex is OpenAI's coding agent. It runs as a CLI in the terminal, as an IDE extension for VS Code, Cursor and Windsurf, in the ChatGPT desktop app, on the web and in the ChatGPT mobile app, and as a cloud agent, Codex Cloud; it also works with GitHub, Slack and Linear. It uses OpenAI's models and can be pointed at another provider or gateway with a compatible endpoint. It comes with ChatGPT plans from Free to Enterprise, or works with an OpenAI API key billed per token. The Codex CLI is open source (Apache 2.0).

Instructions go in AGENTS.md files: a global one in ~/.codex, one at the project root and more in nested folders, with AGENTS.override.md to override them. Memories, off by default, keep useful context from earlier work for later sessions. Codex documentation

Cursor

Cursor is a code editor built around an AI agent, available for macOS, Windows and Linux. The same agent runs in the Cursor CLI and as cloud agents you can follow on the web or on your phone. It offers models from Anthropic, OpenAI, Google, DeepSeek, Moonshot, Z.ai, Meta and Cursor itself, and you can add your own API keys for chat models. It is paid for with a Cursor plan, and there is a free one; past what a plan includes you can buy more usage, and third-party models are billed by usage.

Project rules live in .cursor/rules, next to user rules, team rules and AGENTS.md files. Cursor documentation

Gemini CLI and Antigravity CLI

Gemini CLI is Google's open-source (Apache 2.0) agent for the terminal, using Google's Gemini models. It reads GEMINI.md files, a global one and those in the project and its folders, and the file name can be changed in settings, for example to AGENTS.md; files can be imported with @. Its memory is kept in those files and a private notes folder for each project, so later sessions have it.

On June 18, 2026 Gemini CLI stopped serving Google AI Pro and Ultra subscribers and free individual users, whom Google pointed to its new Antigravity CLI. Gemini CLI stays available with paid Gemini API keys and with Gemini Code Assist Standard and Enterprise licenses. Antigravity CLI is started with agy, shares its agent with the Antigravity desktop app and reads both GEMINI.md and AGENTS.md. Google's announcement

GitHub Copilot

GitHub Copilot works in VS Code, Visual Studio, JetBrains IDEs, Xcode and Eclipse, in the terminal through Copilot CLI, and on GitHub.com, where its cloud agent takes on tasks and reviews code. It offers models from OpenAI, Anthropic, Google, Microsoft, Moonshot AI and xAI; in VS Code you can also add your own API keys and local models. There is a free plan, paid plans for individuals, and Business and Enterprise plans for organizations.

Repository instructions go in .github/copilot-instructions.md, instructions for chosen paths in .github/instructions/, and AGENTS.md files are read too, or a single CLAUDE.md or GEMINI.md; personal and organization instructions add to them. Copilot Memory, in preview, remembers facts about a repository and your preferences. GitHub Copilot documentation

Nilux

Nilux is our agent. It runs in the terminal on macOS, Linux and Windows and as a desktop app for Mac, and the two share projects, settings and conversations: a session started in one opens in the other. It uses two models, Nilux Standard and Nilux Pro. You pay per token from a balance you top up, with no subscription; a new account starts with free credit and no card is needed.

Instructions go in nilux.md, shared with the team through the repository, with more rules as Markdown files in .nilux/rules/ and private notes in nilux.local.md; instructions for all your projects live in ~/.nilux/nilux.md and ~/.nilux/rules/. A line such as @AGENTS.md brings in a file you already keep, and /init writes a first nilux.md for you. Project memory keeps notes Nilux writes as it works, on your computer, and reads them in later sessions; /memory shows what it keeps and where.

Download Nilux for Mac, or install it in the terminal (Node.js 20 or newer):

npm install -g @nilux-ai/code

OpenCode

OpenCode is an open-source (MIT) coding agent from the OpenCode team at Anomaly. It runs in the terminal, as a desktop app (in beta, for macOS, Windows and Linux) and as an IDE extension. It connects to more than 75 model providers, including local models, and works with some existing subscriptions such as ChatGPT Plus or Pro, GitHub Copilot and GitLab Duo; OpenCode Zen is its own optional, paid list of models the team has tested, and OpenCode Go a low-cost subscription.

Instructions go in AGENTS.md, in the project and globally, which its /init command creates; a CLAUDE.md is used when there is no AGENTS.md, and more files or globs can be added through instructions in opencode.json. OpenCode documentation

How to choose

• Where you work. In the terminal: Aider, Claude Code, Codex, Copilot CLI, the Cursor CLI, Gemini CLI or Antigravity CLI, Nilux, OpenCode and the Cline CLI. In an editor: Cline, Copilot and Cursor, and the extensions of Claude Code, Codex and OpenCode. As a desktop app: Claude Code, Codex, Cline, Antigravity, OpenCode (beta) and Nilux (Mac).
• Whose models. Claude Code and Gemini CLI use their maker's models; Codex uses OpenAI's unless you point it at another compatible provider; Nilux offers two models, Standard and Pro, run by third-party AI providers it does not name. Aider, Cline, Copilot, Cursor and OpenCode let you choose among several providers; Aider, Cline, OpenCode and Copilot in VS Code also run local models.
• How you pay. A plan from the maker: Claude Code, Codex, Copilot and Cursor, the last three with a free one. Your own API key: Aider, Cline, OpenCode and Gemini CLI, and Claude Code, Codex, Cursor and Copilot in VS Code take one too. Per token from a prepaid balance, with no plan: Nilux.
• Open source. Aider, Cline, the Codex CLI, Gemini CLI and OpenCode publish their source.
• Instruction files. AGENTS.md is read by Codex, Cursor, Copilot, OpenCode, Cline and Antigravity CLI, by Claude Code in place of CLAUDE.md, by Gemini CLI when set to, and by Nilux through an @AGENTS.md line, so one file can serve several agents.
• Memory between sessions. Claude Code (auto memory), Codex (Memories, off by default), Copilot (Copilot Memory, in preview), Gemini CLI (into its GEMINI.md files) and Nilux (project memory) keep what they learn for later sessions. With Aider, Cline, Cursor and OpenCode that context lives in the instruction files you keep, and Cline documents a Memory Bank for it.

For the kinds of tools behind these names and the questions worth asking before you pick one, see our guide to AI coding assistants in 2026.

Sources

Each maker's own pages, read on October 28, 2026:

• Aider: Documentation · Coding conventions · Repository
• Claude Code: Overview · Memory and CLAUDE.md
• Cline: Documentation · Rules · Memory Bank · Repository
• Codex: Documentation · AGENTS.md · Memories · Models · Pricing · Repository
• Cursor: Documentation · CLI · Rules · API keys · Pricing · Download
• Gemini CLI and Antigravity CLI: Google's announcement · Gemini CLI repository · GEMINI.md · Memory · Antigravity CLI migration guide
• GitHub Copilot: What is GitHub Copilot · Supported models · Repository instructions · Copilot Memory · Your own models in VS Code
• Nilux: Documentation · Project instructions · Project memory · Permission modes · Pricing
• OpenCode: Documentation · Providers · Rules · Repository

Product names are trademarks of their owners. Nilux is not affiliated with or endorsed by any of the companies named here.