# PettyUI Design Specification

**Date:** 2026-03-28
**Status:** Draft
**Author:** Mats Bosson + Claude

## Vision

PettyUI is a pure headless, AI-native UI component library for SolidJS. It provides zero-opinion styling, bulletproof accessibility, and an API designed primarily for AI coding agents to generate correctly — with humans as the secondary audience.

The north star: **the easiest component library for AI to use, and the most pleasant for humans when they need to intervene.**

---

## Core Principles

1. **AI-first, human-friendly** — Every API decision optimizes for LLM code generation correctness. Consistent patterns, explicit types, machine-readable docs, and no implicit contracts.
2. **Pure headless** — Zero styling, zero theme, zero CSS. Components provide behavior, accessibility, and state. Users own all visual decisions.
3. **Progressive disclosure** — Simple props API for the 90% case. Compound component API for full control. Hook-level escape hatches for the 2%.
4. **Solid-native** — Built from scratch on SolidJS signals and context. No framework translation layers, no state machines, no abstraction overhead.
5. **SSR-correct from day one** — Every component works with SolidStart SSR. Deterministic IDs, no hydration mismatches, proper portal handling.
6. **Single-purpose components** — No overloaded behavior via boolean flags. `Select` and `MultiSelect` are separate components. AI never guesses modes.
7. **Pit of success** — Wrong usage is hard. Right usage is obvious. Errors are specific, actionable, and include fix instructions.

---

## Architecture

### Package Structure

Single npm package with sub-path exports. Monorepo internally, single `pettyui` package externally.

```
pettyui/
├── src/
│   ├── primitives/              # Internal shared building blocks (NOT exported)
│   │   ├── create-controllable-signal.ts
│   │   ├── create-disclosure-state.ts
│   │   ├── create-register-id.ts
│   │   ├── create-collection.ts
│   │   ├── create-list-navigation.ts
│   │   ├── create-typeahead.ts
│   │   └── create-form-control.ts
│   │
│   ├── utilities/               # Standalone exported utilities
│   │   ├── presence/            # <Presence> — keeps exiting elements mounted during animation
│   │   ├── dismiss/             # Escape key, click-outside, focus-outside handling
│   │   ├── focus-trap/          # Focus trapping for modals
│   │   ├── scroll-lock/         # Body scroll prevention
│   │   ├── portal/              # SSR-safe portal
│   │   └── visually-hidden/     # Screen-reader-only content
│   │
│   ├── components/              # All UI components
│   │   ├── accordion/
│   │   ├── alert-dialog/
│   │   ├── checkbox/
│   │   ├── collapsible/
│   │   ├── combobox/
│   │   ├── context-menu/
│   │   ├── dialog/
│   │   ├── drawer/
│   │   ├── dropdown-menu/
│   │   ├── hover-card/
│   │   ├── listbox/
│   │   ├── menubar/
│   │   ├── multi-select/
│   │   ├── navigation-menu/
│   │   ├── number-field/
│   │   ├── pagination/
│   │   ├── popover/
│   │   ├── progress/
│   │   ├── radio-group/
│   │   ├── select/
│   │   ├── separator/
│   │   ├── slider/
│   │   ├── switch/
│   │   ├── tabs/
│   │   ├── text-field/
│   │   ├── toast/
│   │   ├── toggle/
│   │   ├── toggle-group/
│   │   └── tooltip/
│   │
│   ├── schemas/                 # Zod schemas for every component (source of truth)
│   │   ├── dialog.schema.ts
│   │   ├── select.schema.ts
│   │   └── ...
│   │
│   ├── ai/                      # AI integration layer
│   │   ├── generate-prompt.ts   # Generates LLM system prompt from schemas
│   │   ├── mcp/                 # MCP server for Claude Code, Cursor, etc.
│   │   └── catalog.ts           # json-render compatible catalog
│   │
│   └── index.ts
│
├── llms.txt                     # Machine-readable component reference for AI
├── openui.yaml                  # OpenUI spec for tooling
├── package.json
└── tsconfig.json
```

### Distribution

```bash
# Install
npm install pettyui

# Import (sub-path for tree-shaking)
import { Dialog } from "pettyui/dialog";
import { Select } from "pettyui/select";
import { Presence } from "pettyui/presence";

# CLI for copying styled implementations into user projects
npx pettyui add dialog --style tailwind
npx pettyui add select --style vanilla
```

Sub-path exports ensure tree-shaking works perfectly. Each component is independently importable. The CLI copies styled example implementations (using PettyUI headless primitives) into the user's project for full ownership — the shadcn model.

### Dependencies

Minimal, deliberate:

- `@floating-ui/dom` — Positioning for popovers, tooltips, dropdowns, selects
- `solid-js` (peer dependency) — SolidJS core

**Build/dev only (not shipped to users):**
- `zod` 4.x — Schema definitions for AI tooling, type generation, and validation. Zod is used at build time to generate `llms.txt`, `openui.yaml`, and system prompts. It is NOT a runtime dependency of the component library itself. Uses Zod 4 (stable since early 2026) for improved performance and smaller types.

No other runtime dependencies. Utilities (focus-trap, scroll-lock, dismiss, presence) are built in-house and exported standalone.

---

## Internal State Pattern

Every component follows the same internal architecture:

### Signals + Context

```tsx
// 1. Root creates signals and provides context
function DialogRoot(props: DialogProps) {
  const [open, setOpen] = createControllableSignal({
    value: () => props.open,
    defaultValue: () => props.defaultOpen ?? false,
    onChange: props.onOpenChange,
  });

  const context: InternalDialogContext = {
    open,
    setOpen,
    modal: () => props.modal ?? true,
    contentId: createSignal<string | undefined>(undefined),
    titleId: createSignal<string | undefined>(undefined),
    descriptionId: createSignal<string | undefined>(undefined),
  };

  return (
    <InternalDialogContext.Provider value={context}>
      {props.children}
    </InternalDialogContext.Provider>
  );
}
```

### Dual Context (Public + Internal)

Learned from corvu. Every component exposes two context layers:

- **Internal context** — Includes setters, registration functions, refs. Never exposed to consumers. Used only by component parts internally.
- **Public context** — Read-only accessors. Exported via `Dialog.useContext()`. Safe for consumers to build custom parts.

```tsx
// Internal — only accessible to Dialog.Content, Dialog.Trigger, etc.
const InternalDialogContext = createContext<InternalDialogContextValue>();

// Public — accessible to consumers via Dialog.useContext()
const DialogContext = createContext<DialogContextValue>();

// Public context only exposes read-only accessors
type DialogContextValue = {
  open: Accessor<boolean>;
  modal: Accessor<boolean>;
};
```

### Controllable Signal Primitive

The `createControllableSignal` primitive handles controlled vs uncontrolled state for every stateful component:

```tsx
function createControllableSignal<T>(options: {
  value: Accessor<T | undefined>;      // Controlled value (if provided)
  defaultValue: Accessor<T>;           // Uncontrolled default
  onChange?: (value: T) => void;        // Callback on change
}): [Accessor<T>, (value: T) => void];
```

When `value()` is not `undefined`, the component is controlled. Otherwise it manages its own internal signal. This pattern is used by every stateful component: Dialog (open), Select (value), Accordion (expandedItems), Tabs (activeTab), etc.

### ID Registration

Child parts register their IDs with the root context for ARIA linking:

```tsx
// In Dialog.Title
const context = useInternalDialogContext();
const id = createUniqueId(); // SSR-deterministic
createEffect(() => context.titleId[1](id));
onCleanup(() => context.titleId[1](undefined));

// In Dialog.Content — uses the registered ID
<div role="dialog" aria-labelledby={context.titleId[0]()} />
```

`createUniqueId()` from SolidJS produces deterministic IDs for SSR hydration.

---

## Component API Design

### Dual-Layer API: Simple + Compound

Every component offers two API surfaces. The simple API covers 90% of use cases with minimal cognitive load. The compound API provides full compositional control.

#### Layer 1: Simple Props API

```tsx
// Dialog — 2 props to get a working accessible modal
<Dialog open={open()} onOpenChange={setOpen}>
  <Dialog.Content>
    <Dialog.Title>Confirm deletion</Dialog.Title>
    <p>This cannot be undone.</p>
    <Dialog.Close>OK</Dialog.Close>
  </Dialog.Content>
</Dialog>

// Select — flat props, works immediately
<Select
  options={countries}
  value={selected()}
  onValueChange={setSelected}
  placeholder="Choose a country"
/>

// Checkbox — single component
<Checkbox checked={agreed()} onCheckedChange={setAgreed}>
  I agree to the terms
</Checkbox>
```

In the simple API:
- Dialog auto-generates Portal, Overlay, focus trap, scroll lock, and dismiss behavior
- Select auto-generates Trigger, Content, and Items from the `options` prop
- Form controls are single components with sensible defaults

**Detection mechanism:** Root components check for the presence of specific child parts using context registration. When a part mounts, it registers itself with the root. During the first render cycle, if no Trigger/Portal/Overlay registered, Root renders the auto-generated defaults. This is a one-time check — once the component tree stabilizes, defaults are locked in.

#### Layer 2: Compound Component API

When you need control, decompose into parts. **If you render a part explicitly, PettyUI stops auto-generating it.**

```tsx
// Full control over every piece
<Dialog open={open()} onOpenChange={setOpen}>
  <Dialog.Trigger as={MyButton}>Open</Dialog.Trigger>
  <Dialog.Portal target={document.getElementById("modals")}>
    <Dialog.Overlay class="my-overlay" />
    <Dialog.Content
      class="my-content"
      onOpenAutoFocus={(e) => e.preventDefault()}
    >
      <Dialog.Title>Confirm deletion</Dialog.Title>
      <Dialog.Description>This action cannot be undone.</Dialog.Description>
      <div class="actions">
        <Dialog.Close as={MyButton}>Cancel</Dialog.Close>
        <button onClick={handleDelete}>Delete</button>
      </div>
    </Dialog.Content>
  </Dialog.Portal>
</Dialog>

// Select with custom rendering
<Select.Root value={selected()} onValueChange={setSelected}>
  <Select.Trigger>
    <Select.Value placeholder="Choose a country" />
    <Select.Icon />
  </Select.Trigger>
  <Select.Content>
    <Select.Group>
      <Select.GroupLabel>Europe</Select.GroupLabel>
      <For each={europeanCountries}>
        {(country) => (
          <Select.Item value={country.code}>
            <Select.ItemText>{country.name}</Select.ItemText>
            <Select.ItemIndicator>✓</Select.ItemIndicator>
          </Select.Item>
        )}
      </For>
    </Select.Group>
  </Select.Content>
</Select.Root>
```

#### Layer 3: Escape Hatches

Public context + children-as-function for cases PettyUI didn't anticipate:

```tsx
// Access component state for custom behavior
const ctx = Dialog.useContext();

// Children-as-function for full prop control
<Dialog.Trigger>
  {(props) => (
    <MyButton {...props} class="custom" onClick={[props.onClick, trackAnalytics]}>
      Open dialog
    </MyButton>
  )}
</Dialog.Trigger>
```

### Polymorphic Rendering

Two patterns, covering simple and advanced use cases:

#### `as` prop (simple — change the element)

```tsx
<Dialog.Trigger as="a" href="/confirm">Open</Dialog.Trigger>
<Tabs.Trigger as={MyButton} variant="ghost">Tab 1</Tabs.Trigger>
```

Internally uses SolidJS `<Dynamic>` component. The `as` prop accepts a string tag name or a SolidJS component.

#### Children-as-function (advanced — full control)

```tsx
<Dialog.Trigger>
  {(props) => (
    <MyButton {...props} class="custom">
      Open
    </MyButton>
  )}
</Dialog.Trigger>
```

PettyUI passes all necessary props (ARIA attributes, event handlers, data attributes, ref) as the argument. The consumer spreads them onto their element.

### Controlled vs Uncontrolled

Every stateful component supports both patterns with the same naming convention:

```tsx
// Uncontrolled — PettyUI manages state internally
<Dialog defaultOpen={false}>
<Select defaultValue="us">
<Accordion defaultExpandedItems={["item-1"]}>

// Controlled — consumer manages state
<Dialog open={open()} onOpenChange={setOpen}>
<Select value={selected()} onValueChange={setSelected}>
<Accordion expandedItems={items()} onExpandedItemsChange={setItems}>
```

### Data Attributes

Every component part emits data attributes reflecting current state, enabling pure CSS styling:

```
data-state="open" | "closed"       — Dialog, Popover, Collapsible, Tooltip
data-expanded                      — Accordion.Item
data-disabled                      — Any disabled component
data-highlighted                   — Menu.Item, Select.Item (keyboard focus)
data-checked                       — Checkbox, Radio, Switch
data-indeterminate                 — Checkbox
data-orientation="horizontal" | "vertical" — Tabs, Separator, Slider
data-opening                       — Presence: entering animation
data-closing                       — Presence: exiting animation
data-placeholder                   — Select.Value when no value selected
```

Animation-aware attributes (`data-opening`, `data-closing`) are powered by the Presence utility and persist during enter/exit transitions.

---

## Component Archetypes

Three consistent patterns repeated across all components. Learn one, know them all.

### Archetype 1: Overlay

**Used by:** Dialog, AlertDialog, Drawer, Popover, Tooltip, HoverCard, DropdownMenu, ContextMenu

**Pattern:**
- Root manages open/close state
- Trigger toggles the overlay
- Content is the overlay body
- `open` / `onOpenChange` for controlled state
- Auto-generates Portal, Overlay (if applicable), focus trap, scroll lock, dismiss

**Consistent props:**
```tsx
open?: boolean
defaultOpen?: boolean
onOpenChange?: (open: boolean) => void
modal?: boolean               // Where applicable (Dialog, AlertDialog)
```

**Consistent parts:**
```tsx
Component.Root          // or just <Component>
Component.Trigger
Component.Content
Component.Close         // Where applicable
Component.Portal        // Override portal target
Component.Overlay       // Where applicable (Dialog, Drawer)
```

### Archetype 2: Collection

**Used by:** Select, MultiSelect, Combobox, Listbox, Tabs, RadioGroup, ToggleGroup, Menubar

**Pattern:**
- Root manages selected value(s)
- Items are selectable children
- Groups organize items with labels
- `value` / `onValueChange` for controlled state
- Keyboard navigation (arrow keys, typeahead) built in

**Consistent props:**
```tsx
value?: T                              // Select, Combobox, RadioGroup
defaultValue?: T
onValueChange?: (value: T) => void
disabled?: boolean
required?: boolean
orientation?: "horizontal" | "vertical"
```

**Consistent parts:**
```tsx
Component.Root
Component.Item
Component.ItemText
Component.ItemIndicator
Component.Group
Component.GroupLabel
```

### Archetype 3: Form Control

**Used by:** Checkbox, Switch, Toggle, Slider, TextField, NumberField

**Pattern:**
- Single component for the simple case
- Decomposes into Root + Input + Label + Description + ErrorMessage for full control
- `value` / `onValueChange` or `checked` / `onCheckedChange` for controlled state
- Integrates with native form submission

**Consistent props:**
```tsx
value?: T | checked?: boolean
defaultValue?: T | defaultChecked?: boolean
onValueChange?: (value: T) => void | onCheckedChange?: (checked: boolean) => void
disabled?: boolean
required?: boolean
readOnly?: boolean
name?: string                          // For form submission
```

---

## Naming Conventions

Strict consistency across all components. AI generalizes from one component to all others.

### Events

Always `on[Thing]Change`:
- `onOpenChange` — Dialog, Popover, Tooltip, DropdownMenu, etc.
- `onValueChange` — Select, Combobox, Slider, RadioGroup, etc.
- `onCheckedChange` — Checkbox, Switch
- `onExpandedChange` — Accordion, Collapsible

Never: `onToggle`, `onVisibilityChange`, `onChange`, `onSelect`, `onClose`

### Boolean Props

Adjectives, no `is` prefix:
- `disabled`, `required`, `readOnly`, `modal`, `multiple`

Never: `isDisabled`, `isRequired`, `isReadOnly`

### State Props

Always `value`/`defaultValue` or `checked`/`defaultChecked` or `open`/`defaultOpen`:
- `value` + `onValueChange` for value-bearing components
- `checked` + `onCheckedChange` for boolean toggle components
- `open` + `onOpenChange` for disclosure components

### Component Naming

- Single-purpose names: `Select`, `MultiSelect` (not `Select` with a `multiple` prop)
- Parts use dot notation: `Select.Root`, `Select.Trigger`, `Select.Content`
- No abbreviations: `DropdownMenu` not `DDMenu`, `NavigationMenu` not `NavMenu`

---

## Accessibility

### Target

WCAG 2.1 AA compliance for all components. Every component follows WAI-ARIA Authoring Practices.

### Built-in Behavior

Every component automatically provides:

- **Correct ARIA roles and attributes** — `role="dialog"`, `aria-modal`, `aria-expanded`, `aria-labelledby`, `aria-describedby`, etc.
- **Keyboard navigation** — Arrow keys for collections, Escape for dismissal, Tab/Shift+Tab for focus movement, Enter/Space for activation
- **Focus management** — Auto-focus on open, return focus on close, focus trapping for modals
- **Screen reader announcements** — Live regions for toasts, status changes
- **Typeahead** — Type characters to jump to matching items in Select, Combobox, Menu

### Utilities (Exported Standalone)

These utilities power the components internally but are also exported for standalone use:

- **`<Presence>`** — Keeps elements in the DOM during exit animations. Provides `data-opening` and `data-closing` attributes.
- **`createDismiss`** — Handles Escape key, click-outside, and focus-outside with a layer stack for nested overlays.
- **`createFocusTrap`** — Traps Tab focus within a container. Handles edge cases (no focusable elements, shadow DOM).
- **`createScrollLock`** — Prevents body scroll. Options for scrollbar shift compensation (padding vs margin), pinch-zoom allowance.
- **`<Portal>`** — SSR-safe portal. Renders to `document.body` by default, configurable target.
- **`<VisuallyHidden>`** — Screen-reader-only content.

---

## Presence Primitive

The `<Presence>` component solves the hardest animation problem: keeping exiting elements in the DOM until their animation completes.

```tsx
import { Presence } from "pettyui/presence";

<Presence present={open()}>
  <div class="dialog-overlay" />
</Presence>

// Or with children-as-function for state access
<Presence present={open()}>
  {(props) => (
    <div
      class="dialog-content"
      data-opening={props.opening || undefined}
      data-closing={props.closing || undefined}
    />
  )}
</Presence>
```

Data attributes emitted:
- `data-opening` — Element is entering (present changed to true)
- `data-closing` — Element is exiting (present changed to false, still mounted)

This enables pure CSS animations:
```css
.dialog-content[data-opening] { animation: fadeIn 200ms; }
.dialog-content[data-closing] { animation: fadeOut 150ms; }
```

No opinion on animation approach. Works with CSS transitions, CSS animations, Motion One, or any JS animation library.

---

## TypeScript Design

### Layered Types

Simple types for the common API (fast autocomplete). Type helpers for advanced use cases (full generic precision).

```tsx
// 95% of users — simple, fast autocomplete, clear errors
<Dialog.Trigger as="a" href="/page">Open</Dialog.Trigger>

// Design system authors — full precision when wrapping
import type { PettyUI } from "pettyui";
type MyTriggerProps = PettyUI.TriggerProps<typeof MyButton>;
```

### Zod Schemas as Source of Truth

Every component's props are defined as a Zod schema. This serves triple duty:

1. **TypeScript types** via `z.infer<typeof schema>`
2. **Runtime validation** for AI-generated output
3. **Auto-generation** of llms.txt, openui.yaml, and LLM system prompts

```tsx
// schemas/dialog.schema.ts
import { z } from "zod";

export const DialogPropsSchema = z.object({
  open: z.boolean().optional()
    .describe("Whether the dialog is currently open. When provided, dialog becomes controlled."),
  defaultOpen: z.boolean().default(false)
    .describe("Initial open state for uncontrolled usage."),
  onOpenChange: z.function().args(z.boolean()).optional()
    .describe("Called when the open state should change."),
  modal: z.boolean().default(true)
    .describe("Whether to block interaction outside the dialog and trap focus."),
});

export type DialogProps = z.infer<typeof DialogPropsSchema>;
```

### Discriminated Types for Mode-Specific Behavior

Where a component has distinct modes, use TypeScript discriminated unions:

```tsx
// Select: value is T
type SelectProps<T> = {
  value?: T;
  onValueChange?: (value: T) => void;
};

// MultiSelect: value is T[]
type MultiSelectProps<T> = {
  value?: T[];
  onValueChange?: (value: T[]) => void;
};
```

No boolean flag that changes types. Separate components with separate, precise types.

### Prop Documentation via JSDoc

Every prop has a JSDoc comment with description and default value. This is the primary documentation surface — TypeScript autocomplete IS the docs.

```tsx
interface DialogContentProps {
  /**
   * Whether to force the content to remain mounted in the DOM.
   * Useful when controlling animations with external libraries.
   * @default false
   */
  forceMount?: boolean;

  /**
   * Event handler called when auto-focus fires on open.
   * Call `event.preventDefault()` to prevent default focus behavior.
   */
  onOpenAutoFocus?: (event: Event) => void;
}
```

---

## Error Design

### Pit of Success Errors

Every error is specific, actionable, linkable, and dev-only (stripped in production).

Format:
```
[PettyUI] <Component.Part> error description.
  Fix: Specific instruction on how to fix it.
  Docs: https://pettyui.dev/components/component#section
```

Examples:
```
[PettyUI] <Select.Item> was rendered outside of <Select.Content>.
  Fix: Wrap your Select.Item components inside <Select.Content>.
  Docs: https://pettyui.dev/components/select#composition

[PettyUI] <Dialog> received both "open" and "defaultOpen" props.
  Fix: Use "open" + "onOpenChange" for controlled mode, or "defaultOpen" for uncontrolled. Not both.
  Docs: https://pettyui.dev/guides/controlled-vs-uncontrolled

[PettyUI] <Select.Root> received unknown prop "multiple".
  Fix: Use <MultiSelect> instead of <Select> for multi-value selection.
  Docs: https://pettyui.dev/components/multi-select
```

These errors serve both humans and AI agents. AI can parse the fix instruction and self-correct.

---

## AI Integration Layer

PettyUI ships first-class tooling for AI code generation. This is not an afterthought — it is a core design pillar.

### 1. `llms.txt` (Ships in Package)

Located at the package root. Concise, structured component reference optimized for LLM consumption.

```
# PettyUI Component Reference

## Dialog
Modal overlay that blocks interaction with the page.

### Simple API
<Dialog open={open()} onOpenChange={setOpen}>
  <Dialog.Content>
    <Dialog.Title>Title</Dialog.Title>
    <p>Content here</p>
    <Dialog.Close>Close</Dialog.Close>
  </Dialog.Content>
</Dialog>

### Props
- open: boolean — Whether dialog is visible (controlled)
- defaultOpen: boolean (default: false) — Initial state (uncontrolled)
- onOpenChange: (open: boolean) => void — Called when state should change
- modal: boolean (default: true) — Whether to trap focus and block outside interaction

### Parts (Compound API)
- Dialog.Trigger — Button that opens the dialog. Use `as` prop to customize element.
- Dialog.Portal — Portals content to document.body. Override with `target` prop.
- Dialog.Overlay — Backdrop behind dialog. Auto-generated if not provided.
- Dialog.Content — The dialog panel. Receives focus on open.
- Dialog.Title — Accessible title. Linked via aria-labelledby.
- Dialog.Description — Accessible description. Linked via aria-describedby.
- Dialog.Close — Button that closes the dialog.

### Keyboard
- Escape: Closes the dialog
- Tab: Cycles focus within dialog (when modal)

### Data Attributes
- data-state="open" | "closed" on Trigger, Content, Overlay
- data-opening / data-closing on Content, Overlay (during animations)
```

### 2. `openui.yaml` (Repository Root)

Machine-readable component specification following the OpenUI format:

```yaml
name: PettyUI
version: 0.1.0
framework: solid
components:
  Dialog:
    description: Modal overlay that blocks interaction with the page.
    props:
      open:
        type: boolean
        description: Whether the dialog is currently open.
      defaultOpen:
        type: boolean
        default: false
        description: Initial open state for uncontrolled usage.
      onOpenChange:
        type: function
        description: Called when the open state should change.
      modal:
        type: boolean
        default: true
        description: Whether to trap focus and block outside interaction.
    parts: [Trigger, Portal, Overlay, Content, Title, Description, Close]
    example: |
      <Dialog open={open()} onOpenChange={setOpen}>
        <Dialog.Content>
          <Dialog.Title>Confirm</Dialog.Title>
          <Dialog.Close>OK</Dialog.Close>
        </Dialog.Content>
      </Dialog>
```

### 3. MCP Server

```bash
npx pettyui mcp
```

Exposes to AI agents:
- **Component list** with full props, types, descriptions
- **Usage examples** per component (simple + compound)
- **Installed components** (reads user's project config)
- **Search** across components and props
- **Validation** — check if generated code uses valid props/parts

### 4. System Prompt Generator

```tsx
import { generatePrompt } from "pettyui/ai";

const systemPrompt = generatePrompt({
  components: ["dialog", "select", "tabs", "checkbox"],
  styling: "tailwind",    // or "vanilla" or "panda"
});
// Returns a string containing complete component reference
// derived from Zod schemas — always up to date
```

### 5. CLI for Source Ownership (Separate Package)

The CLI is a separate package (`pettyui-cli` or `create-pettyui`) — not part of the core headless library. It is a convenience tool, not a requirement.

```bash
npx pettyui add dialog --style tailwind
npx pettyui add select --style vanilla
npx pettyui add all --style tailwind
```

Copies styled example implementations into the user's project. These files:
- Import PettyUI headless primitives as a dependency
- Add styling (Tailwind classes, CSS, etc.)
- Are fully owned and editable by the developer
- Are readable by AI agents (source code in the project, not node_modules)

**Scope note:** The CLI is a Wave 2+ deliverable. The core headless library ships first without it.

### 6. json-render Catalog

Optional export for generative UI applications:

```tsx
import { catalog } from "pettyui/catalog";

// AI generates JSON conforming to catalog schema
// json-render validates and renders through PettyUI components
const ui = await model.generate({
  schema: catalog.schema,
  prompt: "Create a settings form with email and notification toggle",
});

render(catalog, ui.json);
```

---

## Component Inventory

### Wave 1: Breadth (Simple + Medium Complexity)

Ship first. Proves the architecture, establishes patterns.

| Component | Archetype | Complexity |
|-----------|-----------|------------|
| Accordion | Collection | Medium |
| AlertDialog | Overlay | Simple |
| Checkbox | Form Control | Simple |
| Collapsible | Form Control | Simple |
| Dialog | Overlay | Medium |
| Drawer | Overlay | Medium |
| HoverCard | Overlay | Simple |
| Pagination | Collection | Medium |
| Popover | Overlay | Medium |
| Progress | Form Control | Simple |
| RadioGroup | Collection | Simple |
| Separator | — | Trivial |
| Slider | Form Control | Medium |
| Switch | Form Control | Simple |
| Tabs | Collection | Medium |
| TextField | Form Control | Simple |
| Toggle | Form Control | Simple |
| ToggleGroup | Collection | Simple |
| Tooltip | Overlay | Simple |
| VisuallyHidden | Utility | Trivial |

### Wave 2: Depth (Complex Interaction Components)

Ship after Wave 1 is stable. These components stress-test every primitive.

| Component | Archetype | Complexity |
|-----------|-----------|------------|
| Select | Collection + Overlay | High |
| MultiSelect | Collection + Overlay | High |
| Combobox | Collection + Overlay | High |
| DropdownMenu | Collection + Overlay | High |
| ContextMenu | Collection + Overlay | High |
| Menubar | Collection | High |
| NavigationMenu | Collection + Overlay | High |
| NumberField | Form Control | Medium |
| Toast | Overlay | High |
| Listbox | Collection | Medium |

### Wave 3: Advanced (High-Demand Gaps)

Components neither Kobalte nor corvu provide well. Market differentiators.

| Component | Notes |
|-----------|-------|
| Command | Command palette (Cmd+K pattern) |
| DatePicker | Calendar-based date selection |
| Calendar | Standalone calendar display |
| TreeView | Hierarchical list with expand/collapse |
| DataTable | Headless table with sort/filter/pagination primitives |
| Carousel | Slide-based content display |
| Stepper | Multi-step wizard flow |
| ColorPicker | Color selection with swatch/slider/area |
| FileUpload | Drop zone + file list management |

---

## SSR Strategy

### Deterministic IDs

Use SolidJS `createUniqueId()` which produces deterministic IDs during SSR. Server and client generate the same IDs, preventing hydration mismatches.

### Portal Handling

The `<Portal>` utility detects SSR and renders content inline during server rendering, then moves it to the target container on hydration.

### No Browser-Only APIs at Import Time

All browser APIs (`document`, `window`, `MutationObserver`, `ResizeObserver`) are accessed lazily inside `onMount` or guarded by `isServer` checks. Importing any PettyUI component in an SSR context never throws.

### SolidStart Compatibility

- Test against every SolidStart release
- Export conditions: `"solid"` for SolidJS compilation, `"import"` for ESM, `"require"` for CJS
- No use of APIs that differ between Solid's server and client builds

---

## Bundle Size Strategy

### Target

Each component should add less than **5KB gzipped** to a production bundle. Complex components (Select, Combobox) may be up to **10KB gzipped**.

For reference: Radix Dialog is ~9.2KB gzipped. Kobalte Popover is ~35KB gzipped. We target Radix-level or better.

### How

- No heavy dependencies (no `@internationalized/*`, no state machine libraries)
- Shared primitives are tiny (signals + context, not state machines)
- `@floating-ui/dom` is the only significant dependency (~3KB gzipped) and only loaded by components that need positioning
- Sub-path exports ensure only imported components are bundled
- Development-only error messages are stripped via `process.env.NODE_ENV` dead code elimination

---

## Testing Strategy

### Unit Tests

Every component gets:
- Rendering tests (basic, with props, with children)
- ARIA attribute verification
- Keyboard interaction tests
- Controlled and uncontrolled state tests
- SSR rendering tests (no hydration mismatch)

### Accessibility Testing

- Automated: `axe-core` on every component in every state (via Vitest)
- E2E (Wave 2+): Playwright tests across Chromium, Firefox, and WebKit — verifies real keyboard navigation, focus management, and ARIA behavior in actual browsers including Safari
- Manual: Test with VoiceOver (macOS/iOS), NVDA (Windows), TalkBack (Android)
- Keyboard-only navigation tests for every interactive component

### Bundle Size Monitoring

CI checks bundle size on every PR. Any component exceeding the target triggers a warning.

---

## Documentation Strategy

Three audiences, three formats:

1. **AI agents** — `llms.txt`, `openui.yaml`, MCP server, Zod schemas. Machine-readable, always derived from source of truth.
2. **Developers getting started** — Website with simple API examples first, compound API second. Every component has a copy-paste example that works on first try.
3. **Design system authors** — API reference with full TypeScript types, public context docs, composition patterns, and styling guides.

---

## Development Tooling

Pinned versions as of 2026-03-28:

- **Runtime:** SolidJS 1.9.x (stable). Architecture is Solid 2.0-ready — no use of deprecated APIs.
- **Build:** Vite 8.x with `vite-plugin-solid` 2.11.x
- **Package manager:** pnpm 10.x
- **Unit testing:** Vitest 4.x + `@solidjs/testing-library` 0.8.x
- **E2E testing:** Playwright (Wave 2+) — real browser a11y testing across Chromium, Firefox, and WebKit/Safari. Critical for verifying keyboard navigation and screen reader behavior in Safari/VoiceOver.
- **Type checking:** TypeScript 6.x strict mode
- **Formatting:** Biome — 25x faster than Prettier, handles formatting + general lint rules
- **Linting:** Minimal ESLint config with `eslint-plugin-solid` only — Biome has no Solid-specific equivalent, so ESLint handles framework-specific reactive rules (signal access, effect dependencies). All other lint rules handled by Biome.
- **Bundling:** tsdown 0.x for package builds (ESM + CJS + `.d.ts`) — Rust-based successor to tsup (same author), 3-5x faster, Rolldown engine (same as Vite 8). Near-identical config to tsup. If edge cases arise, tsup 8.x is the drop-in fallback.
- **Schemas:** Zod 4.x (build-time only) — `z.toJSONSchema()` directly generates OpenUI spec
- **Positioning:** @floating-ui/dom 1.7.x
- **CI:** GitHub Actions — biome check, eslint (solid rules), type-check, vitest, bundle size check, SSR verification
- **Docs site:** SolidStart + MDX

### SolidJS 2.0 Readiness

Solid 2.0 is in beta (2.0.0-beta.4 as of writing). PettyUI targets Solid 1.9.x stable but:
- Avoids deprecated Solid 1.x APIs (`createResource` in favor of patterns that map to 2.0's `createAsync`)
- Uses `createUniqueId`, `createSignal`, `createEffect`, `createContext` — all stable across both versions
- Will ship a Solid 2.0 compatibility update when 2.0 reaches stable release
- CI runs tests against both `solid-js@latest` and `solid-js@next` to catch breaking changes early

---

## Competitive Positioning

| Feature | Kobalte | corvu | PettyUI |
|---------|---------|-------|---------|
| Components | 50+ | 9 | 25+ (Wave 1-2) |
| Bundle per component | ~35KB gzip | Small | <5KB gzip target |
| Simple props API | No | No | Yes |
| Compound API | Yes | Yes | Yes |
| `as` prop | Yes | Yes | Yes |
| Children-as-function | No | Yes | Yes |
| Dual context | No | Yes | Yes |
| Animation data attrs | No | Yes | Yes |
| Presence primitive | External | External | Built-in |
| SSR-first | Fragile | Unknown | Yes |
| AI integration | None | None | llms.txt, MCP, OpenUI, CLI |
| Zod schemas | No | No | Yes |
| Typed error messages | No | No | Yes |
| Extracted utilities | No | Yes | Yes |

PettyUI's unique differentiators:
1. **Dual-layer API** — Simple props + compound components
2. **AI-native** — First component library designed for LLM code generation
3. **Pit of success errors** — Specific, actionable, parseable by AI
4. **Single-purpose components** — No overloaded boolean flags
5. **Bundle size** — Radix-level footprint in the SolidJS ecosystem