Kern

A Claude Code plugin that catches AI-generated design defaults before they ship.

Kern routes every design through a persona system, picks a varied subset of anti-patterns per run (so two runs never produce the same critique), scores output on a 0-100 sameness scale, and fixes copy, color, layout, and interaction before the code lands.

Built for Shadcn/Radix/Next.js stacks. Runs a team of specialist agents that plan, design, implement, and review collaboratively.

The Problem

AI design tools (v0, Lovable, Bolt.new, Cursor Composer) converge on the same visual vocabulary. Purple/blue gradient, centered hero, Inter font, three identical feature cards, "Get Started" CTA. A developer tool and a consumer app look like the same product built on the same template.

Kern fixes this with persona-first generation and a sameness score that quantifies how close a design is to the AI default.

Installation

Add the raymondware marketplace, then install Kern:

/plugin marketplace add raymondware/kern
/plugin install kern@raymondware

That's it. Restart Claude Code and the /kern:* commands are available.

Quick Start

# Generate a component from scratch
/kern:design hero section for a CI/CD observability platform

# Audit existing code for AI-default patterns
/kern:audit
# (paste TSX when prompted)

# Make an existing design less AI-looking
/kern:differentiate

# Generate design specs without code
/kern:plan pricing page for a developer API product

Commands

Command	Does
/kern:design	Full pipeline: persona detection, specialists, implementation, review
/kern:audit	Anti-pattern scan with sameness score against existing code
/kern:differentiate	Identify which AI tool fingerprints are present and apply targeted fixes
/kern:plan	Design specs only (typography, color, layout, motion) -- no code
/kern:review	Full review pass: critic ensemble, copy editor, accessibility audit
/kern:compare	Side-by-side comparison with similarity score
/kern:polish	Rewrite a component against Kern's standards, show diff
/kern:copy	Microcopy audit: button labels, errors, empty states, CTAs
/kern:research	Scan design communities for new anti-patterns
/kern:draw	Run the anti-pattern selector standalone (rotation verification)

How It Works

1. Persona Detection

Kern picks a persona from your description, then loads that persona's rules for font, color, layout, and copy. Five personas:

Persona	Register
developer-tool	Restrained, dense, function-first. Linear/Vercel register.
consumer-saas	Warm, spacious, approachable. Things 3 / Cron register.
creative-tool	Bold, editorial, personality-forward. Figma / iA Writer register.
b2b-enterprise	Conservative, trust-building, data-forward. Stripe / Ramp register.
e-commerce	Product-first, conversion-focused. Allbirds / Ridge register.

2. Variation Rule

Every run picks a different subset of anti-patterns. Kern reads the audit log (state/draws.jsonl) and excludes the previous run's subset. Two runs on the same prompt produce different critiques. No template drift.

3. Anti-Pattern Selection

Each run draws 12-18 patterns from a pool of 69, weighted by surface (landing page, dashboard, pricing), persona, industry, and audience. The selection is logged to state/draws.jsonl before any agent runs.

4. Parallel Critics + Synthesizer

Four critics run in parallel (design, hierarchy, interaction, microcopy), plus a copy editor and accessibility auditor. The synthesizer merges their output, removes duplicates, and computes a consensus sameness score.

5. The Sameness Score

Every design gets a 0-100 score on AI-default similarity:

Score	Meaning
0-20	Distinctive. Clear decisions made. Ship.
21-40	Has character. Some defaults showing.
41-60	Generic. Could be any AI-generated SaaS site.
61-80	Default AI aesthetic. Multiple tool fingerprints present.
81-100	Template unmodified. Do not ship.

Gate threshold: 40 for Kern-produced output, 60 for external audits.

Anti-Pattern Library

Kern ships with 69 anti-patterns across three base files and a research-sourced directory:

File	Patterns
anti-patterns/visual.md	Gradient slop, nested card soup, Inter default, centered glowing hero, AI palettes, drop shadows, inverted dark mode, neon without context
anti-patterns/copy.md	Marketing verbs, hedging, filler openers, self-descriptors, em-dashes, passive voice, vague headlines, broken microcopy
anti-patterns/interaction.md	Dishonest CTAs, loading as marketing, motivational empty states, bouncy interactions, modal fatigue, toast spam, dark patterns
anti-patterns/sourced-from-research/	Community-sourced patterns with citations

Reference Files

File	Purpose
skills/kern/references/fonts.md	Font stacks by context: display, body, mono, serif
skills/kern/references/tokens.md	Spacing, radius, type scale, color philosophy
skills/kern/references/exemplars.md	Sites that get it right and why
skills/kern/references/dribbble-refs.md	Reference shots by category
skills/kern/references/ai-fingerprints.md	Tool-specific fingerprints for /kern:differentiate
skills/kern/references/personas/	Five persona files with font, color, layout, copy rules

Agent Team

Kern runs a team of specialized agents:

Design Specialists (Haiku)

typography-specialist color-specialist layout-specialist motion-specialist

Development (Sonnet)

component-architect component-implementer style-implementer accessibility-implementer

Critics (parallel ensemble)

design-critic hierarchy-critic interaction-critic microcopy-critic copy-editor accessibility-auditor responsive-validator

Orchestration (Opus 4.8)

conductor anti-pattern-selector critique-synthesizer

Contributing

See CLAUDE.md for the contributor guide. Agents live flat in agents/. Anti-patterns in anti-patterns/. Commands in commands/.

License

MIT. See LICENSE.