Cline

Cline is an Apache-2.0 agent that scaffolds features across files, runs your test suite, reads errors, and iterates until things pass, all inside VS Code. Because it is open source and bring-your-own-key, you see exactly what it does and pay only the LLM provider for tokens, usually a few cents per task. The tradeoff is you manage your own API keys and costs, which can add up on large tasks, though a pay-as-you-go Cline provider now exists if you would rather skip key setup.