A design-system gatekeeper for AI coding agents

What it does StyleSeed is an agent skill (one registration, 22 internal workflows) for Claude Code, Codex, and Cursor. You make the design decisions; it compiles them into rules the agent consults before building each screen, then runs a render → score → revise loop: screens scoring below 80 on its 0–100 gate get sent back before you see them. It ships 74 craft rules targeting the classic AI-UI tells — default indigo, emoji icons, the icon-in-a-chip above every card, same-weight cards hiding real priority.

The interesting bit The benchmark honesty is refreshing: on 120 rendered cells, raw rules alone were inconsistent (Codex +1.6, Claude Code −3.7), while the enforced gate improved both by +5.3. The authors explicitly frame it as “repeatable application of expert judgment, not expert-level output,” and even published a scorecard of their own README page scoring 58/100. That’s a project eating its own dog food and showing the receipt.

Key highlights

• 74 craft rules plus a scored gate with an enforced revise-below-80 loop — not just a prompt dump
• 8 output grammars (consumer, editorial, technical, commerce, etc.) so checks fit the result type instead of one universal taste
• Generative palette engine: any key color becomes OKLCH ramps, semantic roles, and contrast evidence
• /styleseed reference compiles screenshots, URLs, Figma, or an existing UI into an evidence-backed project grammar
• Adapters beyond web UI: social carousels, decks, documents, graphics

Caveats

• The workflow must actually be invoked — a markdown file alone can’t block delivery, and 80 points is explicitly not expert approval
• The default install command follows mutable main; the README points evaluators at a pinned v5.0.0 release archive instead
• Heavy feature surface (recipes, skins, studio pipeline, adapters) — a lot to absorb for a tool whose core value is a rules-plus-gate loop

Verdict Worth a look if AI agents keep shipping the same indigo-gradient slop across your screens and sessions. If you already have a strict design system and disciplined humans, it’s mostly guardrails you don’t need.