Component Architecture
Turn a tangle of one-off components into a composable system: audit what exists, classify it into atomic levels, then refactor the worst offenders into small, typed, documented pieces. The prime directive: a component earns its existence by having one responsibility and a prop interface that makes invalid states unrepresentable. Deliver working refactored code plus an audit the user can act on — never just advice.
When to use / when not to
Use for: component decomposition, prop interface design, variant systems, extracting a shared library, deciding controlled vs uncontrolled, component documentation.
Hand off instead when the real need is:
- Visual tokens (spacing, color, type scales) →
skills/frontend-design/design-foundation - Animation/feedback inside components →
skills/frontend-design/interaction-physics - Keyboard/ARIA behavior of components →
skills/frontend-design/accessibility-excellence - Render performance (memoization, re-renders) →
skills/frontend-design/performance-optimization - Unsure where to start across the whole frontend →
skills/frontend-design/frontend-orchestrator
Step 0 — Inspect the codebase, then ask only what's left
Before proposing anything, build a component inventory from the actual code:
- Locate component directories (
components/,ui/,src/app/**,lib/). Note the framework and styling approach (Tailwind, CSS Modules, CSS-in-JS, vanilla) — match it; never introduce a new styling system uninvited. - Count components and flag: files > ~200 lines, components that both fetch data and render detailed markup, duplicated UI (multiple button/input/card implementations), inline styles repeating the same values, class-based inheritance.
- Check for an existing design system or UI kit (shadcn/ui, MUI, Chakra, internal package). If one exists, extend its conventions — don't build a parallel system.
Ask the user (one batch, only what the code didn't answer): scope (whole app, one feature, or one painful component?) and whether a shared library/package is the goal or just cleaner local structure. If the request already implies scope ("refactor this file"), don't ask — state assumptions and proceed.
Workflow
1. Classify the inventory into atomic levels
- Atoms — indivisible, no component dependencies: Button, Input, Label, Icon, Badge, Spinner.
- Molecules — small compositions of atoms with one purpose: FormInput (Label+Input+Error), SearchBar.
- Organisms — sections with business purpose and often state: NavBar, Card, Modal, Form.
- Templates — page layouts arranging organisms; not reusable across page types.
- Pages — templates with real data; use them to find edge cases.
Decision rule: if you can't classify a component, it's doing too much — that's a refactor candidate, not a taxonomy problem.
2. Prioritize refactors by leverage
Order: (1) duplicated atoms (consolidate first — everything else builds on them), (2) god components violating single responsibility, (3) prop interfaces that allow invalid states, (4) missing variants forcing copy-paste. Propose the top 3–5 refactors with a one-line payoff each; have the user confirm scope before rewriting broadly. For a single-component request, skip the vote and refactor it.
3. Refactor with these decision rules
- Split rule: a component that fetches data, manages form state, AND renders detailed markup becomes an orchestrator plus focused children. Split by responsibility, not by line count.
- Composition over inheritance, always. Variants are props (
variant,size), presets are thin wrappers — never subclasses. - Controlled vs uncontrolled: if any other UI must react to the value while editing (live validation, dependent fields, character counts) → controlled. Fire-and-forget input read once on submit → uncontrolled is fine. Never mix modes in one component.
- Prop interface rules: union types instead of booleans that can conflict (
variant: 'primary' | 'danger', notisPrimary+isDanger); constrain to valid options; pass throughclassNameand ARIA attributes; callbacks namedon<Event>. If two boolean props can combine into an invalid state, redesign the interface. - Extraction threshold: extract a shared component at the 2nd–3rd duplication if the copies are genuinely the same concept. Two things that look alike but change for different reasons stay separate — wrong abstractions cost more than duplication.
Canonical shape for an atom (full gallery in references/patterns.md):
interface ButtonProps {
variant?: 'primary' | 'secondary' | 'ghost' | 'danger';
size?: 'sm' | 'md' | 'lg';
disabled?: boolean;
loading?: boolean;
onClick?: () => void;
children: React.ReactNode;
}
export const Button = ({ variant = 'primary', size = 'md', disabled, loading, ...rest }: ButtonProps) => (
<button
className={`button button--${variant} button--${size}`}
disabled={disabled || loading}
{...rest}
/>
);
4. Document what you build
Every extracted/refactored shared component gets docs: purpose, props table, variants with when-to-use, states, accessibility notes, edge cases. Use the template in references/patterns.md. Put docs where the team will see them (Storybook stories if Storybook exists, otherwise a colocated README.md or JSDoc).
Required output format
Deliver both artifacts:
1. The code — refactored/created component files, edited in place, following the project's existing styling and naming conventions. All call sites updated; the app must still compile.
2. Component Architecture Audit (markdown):
## Component Inventory
| Component | File | Level | Verdict | Issue |
| Button (x3 impls) | src/... | atom | consolidate | 3 duplicate implementations |
| UserProfile | src/... | ??? | split | fetches + validates + renders (412 lines) |
| Card | src/... | organism | keep | — |
## Refactors applied
1. [name] — what changed, files touched, why (one line each)
## Refactors recommended (not applied)
1. [name] — payoff, estimated blast radius
## Conventions going forward
- Directory structure: [atoms/molecules/organisms or project's own scheme]
- Prop rules adopted: [union variants, no conflicting booleans, ...]
- When to extract: [the 2–3 rule as applied to this codebase]
Quality bar (check before delivering)
- [ ] Every refactored component has exactly one responsibility you can state in one sentence
- [ ] No prop interface permits an invalid state (no conflicting booleans, no unconstrained strings for variants)
- [ ] No inheritance for variants anywhere in delivered code
- [ ] Each shared component is explicitly controlled or uncontrolled, never both
- [ ] Interactive components keep keyboard operability and visible focus (don't strip what existed)
- [ ] All call sites updated; imports resolve; existing styling system respected
- [ ] Every new shared component has docs (purpose, props, variants, states)
- [ ] Audit table covers the inspected scope, not just the files you touched
Hard don'ts: don't rename the user's public component APIs without flagging it as breaking; don't introduce a new state-management or styling library as a side effect; don't atomize prematurely — a 40-line coherent component doesn't need splitting.
Integration
skills/frontend-design/design-foundation→ feeds this skill the token vocabulary components should consume (spacing/color/type variables).skills/frontend-design/interaction-physics← consumes your component states (hover/active/loading) and animates them.skills/frontend-design/loading-statesandskills/frontend-design/error-handling-recovery← consume your component inventory to add loading/error variants systematically.skills/frontend-design/accessibility-excellence← audits the components you produce; build with semantic elements so it has less to fix.
References
references/patterns.md— full code examples per atomic level, single-responsibility before/after, controlled/uncontrolled implementations, the component documentation template, and size conventions. Read it when actually writing the refactored code or docs.