The serious open-source alternative to Cursor's agent mode. BYO API key, runs as a VS Code extension, reads files and executes commands. Less polished UX than Cursor; same agent capability when wired up correctly. The right call if you want to keep using stock VS Code or already pay for Claude / GPT API access directly.
Cline is the open-source agent that proves you don’t need a new IDE to get Cursor-class agent capabilities. It runs inside stock VS Code as an extension, brings your own API key, and matches the core agent loop (plan → edit → execute → iterate).
What you actually get
Plain VS Code with an extension panel that hosts the agent. Models route to whichever provider you’ve configured. The Apache 2.0 license means you can audit the prompts and behavior — useful when handing it sensitive work.
Where it falls short
Polish lags Cursor. Some affordances (multi-step diff review, agent status visibility) feel newer. The extension is improving fast, and the trade is real if you’d rather pay $20/mo to Anthropic directly than to Cursor.