Teaching agents product design at Vercel

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---
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name: product-design
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description: >-
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  Single entry point for product design and user-facing product implementation
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  in apps/vercel-site. Use whenever work changes what a user sees, understands,
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  chooses, or does: shaping requirements and flows; building or redesigning
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  pages and components; reviewing URLs, screenshots, diffs, or Vercel Agent
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  findings; improving product copy, information architecture, component choice,
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  Geist compliance, hierarchy, layout, interaction, accessibility, responsive
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  behavior, and loading, empty, error, permission, billing, or destructive
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  states. Trigger on design, UX, UI, usability, flow, onboarding, settings,
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  dashboard, build, improve, fix, audit, review, polish, simplify, or
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  production-ready requests. Also use when backend behavior changes a
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  user-visible outcome. Not for backend-only work with no user-visible effect,
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  tests with no shipped UI impact, telemetry-only work, documentation, or
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  marketing content.
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---
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# Vercel Product Design
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Make the interface correct for the user, the product, and Vercel. Working code is not enough: choose the right interaction, make scope and consequences clear, cover reality beyond the happy path, and verify the rendered result.
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## Operating Contract
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- **Start with the job, not the pixels.** Identify who is acting, what they are trying to accomplish, the product object involved, and what the system will change.
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- **Define the outcome before the output.** Establish the current user problem, desired behavior, success signal, and non-goals before choosing a surface or component.
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- **Use evidence, not taste.** Trace decisions to product behavior, canonical repository guidance, an accepted design decision, or a verified adjacent pattern.
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- **Separate facts from decisions.** Mark assumptions and unresolved product choices explicitly; do not hide them inside implementation details.
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- **Treat shipped code as evidence, not automatic precedent.** It proves what exists, not why it is correct. Check it against current components, product behavior, and explicit guidance.
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- **Choose the smallest coherent intervention.** Consider better defaults, behavior, or reuse before adding UI. Do not solve one job by creating unrelated settings or abstractions.
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- **Decide before decorating.** Resolve information architecture, component semantics, interaction, and state behavior before styling or rewriting copy.
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- **Design every reachable state.** Include only states the product can actually enter, but do not stop at the populated success case.
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- **Verify the real surface.** Source inspection establishes behavior; a rendered interface establishes visual and interaction quality. Never claim visual verification from code alone.
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- **Keep one user-facing entry point.** Invoke `product-design`; route internally to the canonical sources below.
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## Request Modes
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Resolve the mode from the user's verb and artifact before acting.
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| Mode      | Typical request                                                                    | Required behavior                                                                                                                                                      |
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| --------- | ---------------------------------------------------------------------------------- | ---------------------------------------------------------------------------------------------------------------------------------------------------------------------- |
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| Shape     | "Design this flow", "How should this work?", feature brief without settled UI      | Frame the problem and evidence, compare material alternatives, then define the flow, states, acceptance criteria, risks, and open decisions. Do not edit unless asked. |
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| Implement | "Build", "fix", "improve", "make compliant", or "run product-design on everything" | Resolve material product decisions, then implement the smallest coherent end-to-end change within scope. Do not absorb unrelated review findings.                      |
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| Review    | "Audit", "critique", "what's wrong?", code review                                  | Inspect source and rendered evidence, then report prioritized findings. Do not edit unless asked.                                                                      |
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| Copy      | "Fix the copy", "rewrite these errors"                                             | Edit user-facing language, accessible names, and directly required JSX only. Report structural blockers without silently broadening scope.                             |
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| Harden    | "Polish", "production-ready", "handle edge cases"                                  | Preserve the settled product direction while fixing state, resilience, responsive, accessibility, and finish defects.                                                  |
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When intent is ambiguous, use the narrowest mode supported by the verb. A URL, screenshot, route, or component identifies scope; it does not by itself authorize edits.
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A material decision changes the user's task, default, scope, consequence, navigation, interaction surface, or reachable states. Copy mechanics, token replacement, and established component substitutions usually are not material.
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## Decision Authority
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Resolve conflicts in this order:
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1. The user's explicit goal and constraints.
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2. Verified user/product evidence and system truth.
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3. Repository-canonical guidance: `AGENTS.md`, Geist component APIs, `packages/geist/STYLE_GUIDE.md`, and routed skills.
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4. Accepted product/design decisions and exemplars with stable evidence.
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5. Verified adjacent shipped patterns in the same product area.
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6. General interface heuristics.
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## Workflow
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### 1. Set scope and mode
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Name the target surface and request mode in the work plan or review notes.
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### 2. Load product context
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Before proposing UI, read the applicable `AGENTS.md` chain, supplied briefs and designs, and the product logic that determines mutations, permissions, validation, errors, and side effects.
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### 3. Model the product decision
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For Shape, Implement, Harden, full Review, or any material product/flow change, read `product-judgment.md` and write a compact internal brief covering user, job, current behavior, desired outcome, success signal, non-goals, object, scope, action, consequence, reversibility, permissions, and open decisions.
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### 4. Map the surface and states
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Inventory entry points, visible regions, overlays, transitions, exits, and return paths. Map only reachable states including loading, empty, sparse, populated, validation, error, permission, disabled, optimistic, stale, destructive, and responsive variants.
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### 5. Load the routed references
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| Need | Load |
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| ---- | ---- |
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| Product/flow/component decision | `product-judgment.md` + `component-guide` |
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| Implementation, material visual change, or full review | `interface-quality.md` |
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| Copy or accessible names | `copy.md` + `surfaces.md` routing |
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| Layout, typography, color, spacing, Geist APIs | `design-guidelines` + `packages/geist/STYLE_GUIDE.md` |
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| Keyboard, focus, forms, touch, animation, URL state, performance | `web-interface-guidelines` |
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| Overflow, localization, extreme data, network/error resilience | `resilience.md` |
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### 6. Decide, then implement
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For each non-mechanical change, be able to answer: what user problem does this solve, why is this component appropriate, what consequence must the interface communicate, which evidence supports the decision, and what is the smallest coherent change?
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### 7. Verify
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1. Confirm the primary job and acceptance criteria.
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2. Run repository lint checks.
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3. Inspect relevant compact and wide viewports.
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4. Exercise every materially changed reachable state.
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5. Verify keyboard order, focus movement, loading behavior, and pointer/touch targets.
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6. Test long content, large values, constrained width, and localization/RTL risk.
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7. Load `review-design-system` for structural visible changes.
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## Product Design Standards
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- Make the user's primary task and primary action unmistakable.
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- Preserve the user's mental model and current context unless changing it solves a verified problem.
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- Name the exact object, scope, and consequence of important actions.
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- Use navigation components for navigation and action components for actions.
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- Choose surface persistence to match importance.
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- Prefer inline disclosure before adding a modal.
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- Expose advanced controls when needed without making the default path carry their complexity.
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- Prefer strong defaults and direct behavior over adding configuration the user must learn and maintain.
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- Use semantic Geist components and their APIs before custom HTML or styling.
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- Use hierarchy, spacing, and alignment before adding containers.
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- Preserve user input through validation and recoverable errors.
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- Keep loading control labels stable; use the component's loading/busy affordance.
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- Make destructive actions proportional to impact and provide undo when the system can honestly support it.
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- Do not add decorative novelty, motion, or copy unless it clarifies structure, state, or brand intent.
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## Review Output
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Lead with findings, ordered by user impact:
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- **P0:** blocks the primary task, creates severe accessibility failure, or can cause unrecoverable user harm.
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- **P1:** likely task failure, misleading consequence, missing critical state, or major responsive/accessibility defect.
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- **P2:** meaningful friction, inconsistency, weak hierarchy, or recoverability issue.
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- **P3:** minor craft or consistency improvement.
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For each finding include: file/line or rendered location, verification status, canonical source, user consequence, and smallest concrete fix.
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## Skill Integrity
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- Add or change a rule only after current-source verification and human acceptance.
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- Record scope, rationale, evidence, exceptions, and a bad/good example.
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- Prefer the narrowest destination: canonical source, routed reference, exemplar, lint/eval check, or coverage gap.
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- Keep deterministic checks mechanical. Keep judgment in prose with its evidence and degree of freedom.
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- Never promote one screenshot, one shipped file, or one reviewer comment into a universal rule by itself.

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/** @type {import('eslint').Rule.RuleModule} */
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module.exports = {
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  meta: {
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    type: 'suggestion',
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    docs: {
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      description: 'Suggest Radio buttons when Select has 2-3 static options',
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      category: 'Design System',
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      recommended: true,
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    },
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    schema: [],
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    messages: {
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      preferRadio:
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        'Select with {{ count }} static options. Consider using Radio buttons — they show all options at once without requiring a click to open.',
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    },
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  },
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  create(context) {
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    return {
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      JSXElement(node) {
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        const opening = node.openingElement;
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        if (opening.name.type !== 'JSXIdentifier') return;
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        if (opening.name.name !== 'Select') return;
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        const hasDynamic = node.children.some(
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          (child) =>
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            child.type === 'JSXExpressionContainer' &&
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            child.expression.type === 'CallExpression',
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        );
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        if (hasDynamic) return;
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        const optionChildren = node.children.filter(
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          (child) =>
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            child.type === 'JSXElement' &&
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            child.openingElement.name.type === 'JSXIdentifier' &&
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            child.openingElement.name.name === 'option',
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        );
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        if (optionChildren.length < 2 || optionChildren.length > 3) return;
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        context.report({
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          node: opening,
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          messageId: 'preferRadio',
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          data: { count: String(optionChildren.length) },
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        });
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      },
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    };
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  },
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};