Cline

What it is

Cline is a VS Code extension that turns the editor into an autonomous coding agent. It can create/edit files, run terminal commands, browse the web, and chain many steps together. Because it is open-source and bring-your-own-key, you control which model it uses and where the data goes.

Best for

• Long, multi-step coding tasks inside VS Code
• Prototype a feature end-to-end from a one-line prompt
• Browser + terminal + editor in one agent loop

Quick start

1. Open VS Code → Extensions (Cmd/Ctrl+Shift+X) → search "Cline" → install.
2. Click the Cline robot icon in the sidebar → choose API Provider (OpenRouter, Anthropic, OpenAI, Bedrock, etc.) and paste your key.
3. Tip: OpenRouter gives one key that works across every model, including Claude Sonnet and free models — easier for testing.
4. Type a task in Cline's chat box (e.g. "Add a /health endpoint to this Express app") and approve each step in the diff view.
5. Optional: `npm i -g cline` to also get the CLI for headless use.

Sample input / output

"Refactor this Express server to use async/await everywhere, add input validation with Zod, and add a Vitest suite covering the POST /users route."

Modified 5 files:
  src/routes/users.ts (async/await conversion, +Zod schema, +18 lines)
  src/middleware/validate.ts (new)
  src/server.ts (apply middleware)
  src/routes/__tests__/users.test.ts (new — 4 test cases)
  package.json (added zod, vitest)
12/12 tests pass. Linter clean. Cline produced 1 commit per file with sensible messages.

Benchmarks

Pricing

Free extension; bring your own API keys

Underlying models