# Three AI Agents That Actually Write Code for You (and How to Use Them) > Source: > Published: 2026-07-15 23:46:00+00:00 If you're still bouncing between your editor and a chat window, asking an LLM for code and then manually wiring it into your project, you're doing it the hard way. In 2026, **AI agents** have matured into tools that read your entire codebase, propose multi-file changes, and execute commands on your behalf. They don't just autocomplete—they plan, edit, test, and iterate. I've been testing three agents that plug directly into real workflows: GitHub Copilot with GPT-5.6, Cursor, and Windsurf. Here's what they do and when to reach for each one. An agent isn't just a better autocomplete. It's a system that can: Under the hood, they use frontier models like GPT-5.x, Claude Sonnet, and Gemini 2.0. The key difference from chat tools is execution: these agents live inside your editor or terminal and can act on your codebase without you shuttling text back and forth. GitHub Copilot shipped support for the GPT-5.6 family—Sol, Terra, and Luna—across VS Code, JetBrains, Xcode, the CLI, and GitHub.com itself. You pick the model variant in your editor's Copilot panel. **Sol** is the heavyweight: use it for deep refactors where the agent needs to map dependencies across a monorepo and propose architectural changes. I used Sol to extract a shared package from a tangled TypeScript workspace. It read the import graph, suggested a migration plan, and generated a draft PR with file moves and updated `tsconfig` references. **Terra** handles everyday coding—adding endpoints, fixing bugs, writing tests. **Luna** is fast and cheap for quick fixes. You'll need a Copilot Business or Enterprise plan to access Sol and Terra in most IDEs; individual plans are rolling out. Setup is straightforward if you already have Copilot installed: just update your extension and select a model. Cursor is a fork of VS Code with agentic features baked in. **Cursor Tab** gives you diff-style autocomplete that can rewrite entire functions. The **chat and task panel** lets you describe a feature, and Cursor will propose a plan, edit multiple files, and run commands. I used Cursor to implement a REST endpoint in a Python/FastAPI service. I pasted an issue description into the task panel. Cursor scanned the project, suggested adding a handler in `api/routes.py` , a schema in `models.py` , and tests in `tests/test_routes.py` . It generated all three, ran `pytest` , caught a type mismatch, and fixed it in the next iteration. Cursor supports Claude Sonnet and recent OpenAI models. It has a free tier with rate limits and a Pro plan for heavier use. The IDE layer is polished, so if you're comfortable in VS Code, the learning curve is minimal. Windsurf is a new editor built from the ground up for agentic workflows. When you start a task, it generates a visible step-by-step plan, then calls a frontier model to execute each step—writing code, running terminal commands, reading compiler errors, and iterating. I pointed Windsurf at a full-stack repo and asked it to add a dark-mode toggle to a React frontend, wire it to a user preference in the backend, and update docs. It laid out a plan (modify `App.tsx` , add a Zustand store, create a PUT endpoint, update `README.md` ), executed each step, ran `npm test` , and surfaced the diffs for review. Windsurf runs on Linux, Mac, and Windows. Setup is a fresh install (it's not a VS Code fork), but it imports your existing extensions and settings. The agent session UI is more explicit than Cursor's, which I found helpful for reviewing plans before committing. Agent | Best for | Pricing | Friction | |---|---|---|---| | GitHub Copilot | Teams already on GitHub, monorepos | Business/Enterprise for Sol | Low | | Cursor | Solo devs, polyglot projects | Free tier + Pro ($20/mo) | Low | | Windsurf | Greenfield work, explicit workflows | Free beta, pricing TBA | Medium | All three respect language conventions if your project has linters and formatters configured. Copilot integrates tightly with GitHub Actions and pull requests. Cursor feels more IDE-native. Windsurf makes the agent's reasoning visible, which I prefer when refactoring legacy code. Letting an agent edit code and run commands can go sideways. Here's my checklist: `main` .`rm -rf` or install packages without confirmation.`.gitignore` and `.cursorignore` (or equivalent) to hide secrets.`.env` files.I treat agent output like a junior dev's PR: useful, but it needs a human review. If you're already using Copilot, flip on Sol or Terra for your next refactor and compare it to your usual workflow. If you want more control, install Cursor and point it at a side project. If you like seeing the agent's reasoning, grab Windsurf and walk it through a feature from scratch. Which of these have you tried, or are you sticking with plain autocomplete?