Style Seed is a design engine for Claude Code, Codex, Cursor, and other AI agents that teaches design judgment instead of just providing data. It includes 74 rules, 48 components, 7 brand skins (inspired by Toss, Stripe, Linear, Notion, Raycast, Arc, Vercel), a named motion system with 5 seeds + 20+ moves, and 15 /ss-* skills to stop AI-generated UI from looking generic.

The system fights common AI tells — default indigo, icon-chip clichés, template layouts, rainbow lists — through a scored Quality Gate that reviews and fixes output to ≥80/100 before you see it. A design lock (STYLESEED.md) persists key color, font, radius, and motion across sessions to prevent drift. Every agent ships with CLAUDE.md, AGENTS.md, and .cursorrules for cross-tool compatibility.

Install in 30 seconds via `npx skills add bitjaru/styleseed` (adds 19 agent skills) or paste the prompt for zero-install usage. The engine enforces specific designer judgments: refined black (#2A2A2A), single-accent law, 2:1 number-to-unit ratios, nested-radius law, layered shadows ≤8%, tabular numbers, status color for severity only, 8px spatial grid, and motion scoped by surface type.

MIT licensed and free, Style Seed targets the whole "looks AI-generated" problem with judgment + enforcement layers that design collections, "make-it-prettier" skills, and UI generators lack. It works alongside brand DESIGN.md files and generators as the coherence layer.