In this video I show you OpenCode, the best AI coding agent I’ve tested—and the wild part is it’s completely free and open source. It runs wherever you work (terminal, IDE, or desktop), supports running multiple agents in parallel on the same project, and lets you bring your own accounts (like ChatGPT Plus/Pro) or pick from 75+ LLMs, including local models. Privacy is a big deal here too: OpenCode doesn’t store your code or context, so it can work in sensitive environments. I walk you through installing it via npm, starting a project folder, and using the two modes: Build (just build) vs Plan (think first, then build). I build a YouTube Thumbnail Generator app using the Nano Banana Pro model through the KI (key.ai) API, generate a full markdown “master prompt,” and let OpenCode scaffold the full React app (Vite + Tailwind + Context). Then I show the real power: I spin up multiple agents—one improving UI with a “cosmic” design, another adding image upload + element referencing—while tracking token usage and cost. We hit a real integration constraint (KI expects image URLs, not raw uploads), fix it, and the app works great for prompt-based generation. The takeaway: OpenCode is insanely capable for building real apps fast, and the agent workflow is the future.