Design.MD vs Terrarium

Design.MD is a collection of Markdown files that encode brand visual languages in a format AI coding agents actually understand. Drop a DESIGN.md file into your project and your AI coding agent — Cursor, Claude Code, Lovable, v0, Bolt — generates UI that matches the target brand instead of defaulting to "the AI beige" of generic Tailwind defaults. The library ships with 60+ ready-made design system files covering popular brands like Stripe, Notion, Linear, and Vercel, encoding their exact color palettes, typography scales, spacing systems, component patterns, and motion guidelines. Files include Tailwind configurations, CSS variables, and component-level patterns — not just vibe words. If a brand isn't available, there's a custom generation flow and a request system. This is a deceptively simple idea with real product leverage. AI agents are excellent at building functional UIs but terrible at design consistency without explicit constraints. DESIGN.md files act as a persistent design brief that the agent can read every time it touches the front end. For indie builders, agencies, and rapid prototypers, this solves a real and recurring problem — free and open, which removes any friction to adoption.

Terrarium is a multi-turn evaluation and optimization engine for LLM agents built by evolvent-ai. Unlike static benchmark suites that measure agents against fixed input-output pairs, Terrarium creates persistent, stateful "living environments" — simulated deployment contexts where agents operate over extended sessions, accumulate state, use tools, and interact with simulated external systems. You evaluate agents the way you'd test a car: by driving it, not by measuring its doors. The system supports configurable environment complexity, including simulated databases, APIs, file systems, and user personas. Agents are scored not just on final outputs but on trajectory quality — how efficiently they reached the answer, how often they hallucinated intermediate steps, and how well they recovered from dead ends. The engine also supports continuous optimization loops where poor-performing trajectories trigger automatic prompt refinement. With 17 stars and created April 14, Terrarium is extremely new. But it's addressing a genuine gap: the disconnect between how agents perform on static benchmarks versus how they behave in production. As enterprise AI deployments scale, the need for realistic pre-production evaluation is becoming critical.