OpenPencil is an open-source, AI-native vector design tool developed in Rust, featuring a high-performance engine that utilizes GPU Skia for rendering across desktop, mobile, and web via WASM. The platform implements an orchestrator-driven multi-agent system that decomposes complex UI tasks into spatial sub-tasks, allowing concurrent AI agent teams to design different sections—such as headers or footers—simultaneously. Technical capabilities include a built-in MCP server for terminal-based design automation via Claude Code or Copilot, and a tiered model capability profile that adapts prompt complexity and "thinking" modes based on the LLM being used (e.g., full prompts for Claude, simplified JSON for Llama). The tool uses a JSON-based, Git-friendly .op file format and supports code export to various frameworks including React with Tailwind CSS, Flutter, and SwiftUI. Following a complete rewrite from TypeScript/Electron to Rust, the desktop application footprint was reduced to a single 55.5 MB binary, while the web payload was optimized to 8.2 MB. Performance benchmarks demonstrate significant scalability, such as handling a 10,000-node live canvas with ~0% idle CPU and layout snapshots returning in approximately 0.68 seconds.