Cline: The Open-Source AI Coding Agent for VS Code

Cline (formerly Claude Dev) is an open-source AI coding agent for VS Code. Unlike GitHub Copilot's inline autocomplete, Cline operates autonomously — reading files, writing code, running terminal commands, and iterating on results until a task is complete. It supports any LLM provider, making it a flexible alternative to proprietary coding agents.

What Cline can do

• Autonomous task execution — given a task, Cline reads relevant files, writes code, runs tests, and fixes errors without constant prompting
• File system access — reads, creates, edits, and deletes files across your project
• Terminal execution — runs shell commands, npm scripts, test suites, and build processes
• Browser control — can open browsers, click elements, and take screenshots for web tasks
• MCP integration — connects to MCP servers for external tool access
• Multi-provider support — works with OpenAI, Anthropic, Gemini, Mistral, Ollama, and any OpenAI-compatible endpoint

Cline vs the alternatives

Installing Cline

# In VS Code
# 1. Open Extensions (Ctrl+Shift+X)
# 2. Search "Cline"
# 3. Install
# 4. Add your API key in settings
# 5. Start a task in the Cline sidebar

The token cost of agentic coding

Cline's autonomous operation comes with a token cost that surprises most new users. A single medium-complexity task might involve:

• 5-15 LLM calls to read files, plan, write, and debug
• 2,000-8,000 input tokens per call (codebase context)
• 500-2,000 output tokens per call (generated code)

That's 15,000-150,000 tokens per task. Cline shows a running cost estimate in the UI — watch it. A complex multi-file refactor with Claude Sonnet can easily cost $2-5.

Using a cheaper model (Gemini 2.5 Flash at $0.10/1M input, $0.40/1M output) for simpler tasks and reserving Claude Sonnet for complex ones is the right cost strategy.