Cline

Cline (formerly Claude Dev) is an open-source autonomous coding agent that runs inside VS Code and can be paired with any LLM API — Claude, GPT-4, DeepSeek, Gemini, or local models via Ollama. Unlike AI code completion tools that suggest inline changes, Cline operates at the agent level: it can read and write any file in your project, execute terminal commands, use browser automation to test web applications, and work through complex multi-step engineering tasks with minimal intervention. The user approves each significant action before Cline executes it, keeping a human in the loop. Cline is free to use (MIT license) — you bring your own API keys and pay provider costs directly, which makes it significantly cheaper than proprietary tools like Cursor or Copilot for heavy users. With over 25,000 GitHub stars, it is one of the fastest-growing AI coding tools of 2025-2026. Its standout feature is the combination of full-codebase access, browser testing capability, and support for nearly every major AI model.