I studied Claude Code's leaked source and built a terminal UI toolkit from it
typescript
dev.to
On March 31, 2026, Claude Code's full TypeScript source was accidentally exposed via npm source maps. Like many developers, I started reading through it — and what I found surprised me. The terminal UI layer wasn't a quick hack. It was a production-grade rendering engine: a custom React reconciler, a pure TypeScript Yoga layout port, a complete ANSI/CSI/DEC/ESC/OSC parser stack, and dozens of polished UI components. All battle-tested across 500K+ daily sessions. So I extracted the architecture