Cline

Cline is an open-source AI coding agent that installs as a VS Code extension. For a cost-conscious technical founder it is appealing for one reason above all: the agent itself is free, and you bring your own model API key, so you pay only the underlying model usage and control your spend down to the request.

It can create and edit files, run terminal commands, use the browser, and work through multi-step tasks, showing you each step for approval. Its Plan and Act modes separate thinking from doing, so you can review the approach before any edits happen, and it supports the Model Context Protocol for giving the agent custom tools.

The honest trade versus a paid editor like Cursor: Cline gives you transparency and pay-as-you-go cost control, but the experience is bring-it-yourself, so you manage keys and the per-task model bill rather than a flat subscription. As with everything in this category, you need to be able to read and approve code, this is not a no-code builder. For a founder who wants an open, model-agnostic agent and is comfortable wiring in a key, it is a strong free starting point.