Cline

Cline is an agent runtime, not an autocomplete plugin. You hand it a task, it reads your codebase, proposes a plan, then edits files and runs bash commands in your terminal, reacting to output as it appears. The core mechanic is the Plan/Act toggle. In Plan mode you agree on a strategy. In Act mode it executes, and you either approve every step or flip auto-approve and let it run on autopilot. Every edit comes with diffs, checkpoints and one-click undo, which matters a lot when an agent is touching a dozen files at once.

The same runtime shows up in several places. There's the VS Code extension, where most of its 11M+ installs across the marketplace and Open VSX registry come from. There's a CLI you can drop into scripts, cron jobs and CI pipelines. There's a native desktop app for Mac, Windows and Linux (currently v0.0.45), and an SDK for embedding the agent in your own products. You teach it your conventions by committing .clinerules files to the repo, and you extend it with MCP servers for databases, APIs and infrastructure. It also supports coordinator agents that delegate to specialists, and you can talk to it from Slack, Discord, Telegram or Linear, or run it headlessly in GitHub Actions and GitLab.

The other half of the pitch is model choice. Cline works with Claude, GPT, Gemini, local models through Ollama or LM Studio, and any OpenAI-compatible endpoint. The extension is Apache 2.0 and free for individual developers. You pay only for the inference you use, either with your own API keys or through the Cline provider at cost. With 70k+ GitHub stars and 250+ contributors, it isn't a weekend side project. The tradeoff is that you're in charge: you pick the model, you set the approval level, and the quality you get tracks the model you plug in. It rewards developers who want control more than those who want a polished, opinionated product that makes every decision for them.