Cline

Cline (formerly Claude Dev) is an open-source autonomous coding agent, licensed under Apache 2.0, that runs as a VS Code extension, a standalone command-line tool, and an embeddable SDK — and can be paired with any LLM API, including Claude, GPT, Gemini, DeepSeek, xAI, Mistral, Cerebras, AWS Bedrock, Azure, GCP Vertex, Ollama, or any OpenAI-compatible endpoint. 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 via a "Plan-and-Act" mode. The user approves each significant action before Cline executes it, keeping a human in the loop. Cline is free to use — 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. It also supports custom rules (.clinerules), MCP servers and plugins, and integrations with Slack, Linear, and CI/CD pipelines. With over 66,500 GitHub stars and 250+ contributors, it is one of the most popular AI coding agents of 2025-2026. Its standout feature is the combination of full-codebase access, browser testing capability, and support for nearly every major AI model.