VizLang is an open-source visual debugger for LangGraph agents. Right-click any Python file and watch your agent's graph come alive ,nodes light up as they execute, state changes appear on hover, and you can step through every decision like a line-by-line debugger. Chat with your agent, handle human-in-the-loop interrupts, manage threads, and inspect tool calls , all without leaving VS Code. No cloud. No accounts. No API keys. Everything runs locally. Free forever, MIT licensed.