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Activation Contract
Use this skill for frontend design-system decisions when an agent must choose, review, or document production-ready technical direction.
- Designing or reviewing UI systems, component anatomy, tokens, layout, or visual interaction.
- Choosing CSS architecture, responsive behavior, accessibility constraints, or motion rules.
- Converting a repository's visual direction into implementation-ready frontend guidance.
Do not use this skill for generic explanation, copy editing, or one-off code changes that do not affect architecture or reusable implementation patterns.
Hard Rules
- Preserve the repository's token and component-state contracts; do not hardcode isolated visual decisions.
- Use semantic HTML and native controls before ARIA substitutes. Define keyboard behavior, visible focus, measurable contrast, and reduced-motion behavior for interactive UI.
- Keep responsive components reusable, reserve layout space for media and fonts, and avoid performance regressions without evidence that the tradeoff is acceptable.
- Keep the main answer decision-first; move deep rationale to local references instead of long inline prose.
- Verify new version, browser, API, legal, or adoption claims before adding them to changelogs or decision guidance.
Decision Gates
| Evidence to inspect | Decision |
|---|---|
| Repository-native CSS architecture, naming, linting, build pipeline, and team conventions | Preserve the established paradigm. Introduce layers, CSS Modules, CSS-in-JS, utilities, or a naming convention only when the repository supports it and migration cost is accepted. |
Existing Design.md, design.md, design-token source, or approved design tool | Treat it as the source of visual truth when present. Do not require a particular filename, generate a handoff file, or assume an external design tool. |
| Supported browser matrix and fallback policy | Gate container queries, nesting, :has(), light-dark(), scroll-driven animation, and other platform features on that matrix; define a fallback when required. |
| Approved token contract plus browser/build support | When the contract selects OKLCH, keep newly specified tokens OKLCH-only. Do not force a legacy color-format migration without an approved cost and compatibility plan. |
| Product theme requirements and design source | Use dark-mode-first only when the product and source require it; otherwise preserve the existing theme strategy and semantic token behavior. |
| Component reuse, page topology, content, and viewport requirements | Prefer container queries for reusable components when supported; use viewport media queries, mobile-first, desktop-first, or composition when they fit the repository and product. |
| Accessibility scope and measurable acceptance criteria | Preserve semantic HTML, keyboard access, focus visibility, contrast measurement, touch-target requirements, and reduced-motion behavior. Apply jurisdiction-specific requirements only when the product scope establishes them. |
| Performance evidence, budgets, and delivery path | Use containment, content-visibility, image formats, font loading, and animation techniques only when compatible with the browser matrix and supported by measured or stated performance goals. |
| Installed repository tooling and approved execution environment | Run a repository-native validation command when available. Do not prescribe npx, a browser audit, encoding, or design-tool command when the dependency, target, permission, or evidence is unavailable. |
Execution Steps
- Identify the repository architecture, design source, browser matrix, accessibility scope, performance evidence, team conventions, tooling availability, and migration cost.
- Define or preserve token, state, semantic HTML, focus, contrast, and reduced-motion contracts before choosing visual novelty.
- Select the smallest compatible CSS, layout, component, theme, and motion approach; record needed fallbacks and rejected alternatives.
- Read
references/technical-reference.mdonly when detailed decision matrices, examples, safeguards, or command prerequisites are needed. - State the chosen pattern, evidence, runtime risks, fallback or migration plan, and validation path. Add changelog claims only when verified.
Output Contract
Return:
- Recommended decision, repository evidence, and why it fits.
- Alternatives rejected with concrete tradeoffs, including migration cost where relevant.
- Accessibility, browser, performance, and runtime risks with mitigations or fallbacks.
- Validation steps that are available in the repository, or the evidence still needed before adoption.
References
references/technical-reference.md— curated technical basis and conditional decision guidance for v3.0.1.references/source-index.md— source pointers and verification rules for version-sensitive claims.