𝗕𝘂𝗶𝗹𝗱𝗶𝗻𝗴 𝗮 𝗦𝗮𝗳𝗲 𝗟𝗼𝗰𝗮𝗹 𝗔𝗜 𝗖𝗼𝗱𝗶𝗻𝗴 𝗔𝗴𝗲𝗻𝘁 𝘄𝗶𝘁𝗵 𝗡𝗼𝗱𝗲.𝗷𝘀
AI agents sound complex. They are not.
An agent is simply an LLM connected to a loop, tools, and safety rules.
I built a local coding agent using Node.js and Mistral via Ollama. You do not need paid API keys. Everything runs on your machine.
The agent helps you understand your JavaScript projects. It can: • List project files • Read project files • Search text • Explain code • Find bugs • Propose code changes
The core principle is safety. The agent can inspect files, but it cannot edit them. It only returns a patch proposal for you to review. This keeps a human in the loop.
How the agent works: A normal chatbot follows a simple path: User asks question -> Model answers
An agent follows a loop: User asks question -> Model decides on a tool -> JavaScript runs the tool -> Model sees the result -> Model answers
Key patterns used in this project: • Agent loop: The process repeats until the model provides a final answer. • Tool calling: The model requests specific JavaScript functions. • Tool allowlist: Only approved tools run. • System prompt: Rules tell the model how to behave. • JSON action protocol: The model responds with structured data. • Safety boundary: File access stays inside your project root.
Safety is the priority. I used a function called safeResolve to prevent path traversal. This ensures the agent cannot access files outside your project folder. I also set limits on file sizes to protect the model context.
The project structure: • src/cli.js: The terminal entry point. • src/agent.js: The core loop and tool dispatch. • src/ollama.js: The local API client. • src/tools.js: Safe filesystem tools. • test/tools.test.js: Safety and behavior tests.
You can run this project with Node.js and Ollama. Use Mistral or try coding-specific models like Qwen2.5-Coder or DeepSeek-Coder for better results.
Build useful tools. Keep them narrow. Let your code enforce the safety boundaries.
Source: https://dev.to/gaurav101/building-a-safe-local-ai-coding-agent-with-nodejs-46ol