In this video, I’m basically saying: stop using Claude Code the normal way if you’re trying to build anything remotely complex. I ran the exact same detailed prompt twice with Claude Code (Opus 4.5 in thinking mode), didn’t interfere at all, and let both agents run on autopilot. The first run followed the usual single context window workflow (plan → implement), and the result was what you’d expect: missing requirements, half-working “AI assistant” actions that don’t actually update the UI, no prompt editing, and thumbnail generation that never even touches Nano Banana—even though it was explicitly in the spec. Then I show the alternative: a long-running agent harness based on Anthropic’s approach. Instead of trying to do everything in one bloated conversation that gets compacted and loses context, the harness breaks the app into a massive feature list and implements features one-by-one with regression testing. That’s how I got a much more polished app: light/dark mode, editable system prompts, delete/duplicate projects, real card editing with history, and actual Nano Banana thumbnail generation with reference images, revisions, and upscaling. I also walk through my free Agentic Coding Harness UI that “slaps a UI” on top of the Anthropic harness, makes setup way easier, and adds performance improvements like storing features in SQLite with MCP tools. If you want production-ready output, let the agent test in a real browser. If you want speed, YOLO mode exists—but you’re trading quality for it.