diff --git a/.changeset/composable-product-details.md b/.changeset/composable-product-details.md
new file mode 100644
index 00000000..a3ad0cc9
--- /dev/null
+++ b/.changeset/composable-product-details.md
@@ -0,0 +1,5 @@
+---
+'@godaddy/gd-commerce-storefront': minor
+---
+
+Add composable product parts. `ProductDetailsRoot` with display parts (`ProductDetailsGallery`, `ProductDetailsTitle`, `ProductDetailsPrice`, `ProductDetailsDescription`, `ProductDetailsBackLink`) and purchase parts (`ProductDetailsPurchase`, `ProductDetailsOptions`, `ProductDetailsOption`, `ProductDetailsPurchaseStatus`, `ProductDetailsAvailability`, `ProductDetailsQuantity`, `ProductDetailsAddToCart`) build custom product layouts. `useProductDetails` reads product state and `useProductDetailsOption` builds custom option controls. Only server-verified SKUs can be added in any layout. `ProductDetails` is now composed from these parts and is visually unchanged. Its markup gains wrapper elements, and the disabled add button now gets its accessible description from a hidden reason element.
diff --git a/packages/commerce-storefront/README.md b/packages/commerce-storefront/README.md
index 0f8ec793..574c718d 100644
--- a/packages/commerce-storefront/README.md
+++ b/packages/commerce-storefront/README.md
@@ -84,9 +84,9 @@ A connection failure leaves the surrounding application and its state mounted. C
 
 The stylesheet includes all required utilities and scopes them to the package's surfaces. The build removes CSS layer wrappers in their declared order, so the exported CSS can pass through a host Tailwind v3 PostCSS pipeline without `@tailwind` directives. Import it directly; consumers do not need to copy or rewrite the CSS. It does not add a global reset or require dependency scanning by a host Tailwind build. The `theme` prop reaches the drawer even though it is portalled into `document.body`.
 
-By default, `.commerce-storefront` wrappers do not paint a background and inherit the host's text color. Set page and section backgrounds on the host application's layout elements. `--commerce-surface` colors controls and the opaque cart drawer, and supplies the base for muted colors; it does not color component wrappers. Set `--commerce-surface` and `--commerce-text` together to adapt controls and the drawer to a dark theme. Avoid setting wrapper backgrounds through CSS or the `theme` prop's `background`, `backgroundColor`, or `backgroundImage` properties, which can still override the transparent default. Descendants inherit the surface text and body font instead of global heading styles. Keep text, controls and focus indicators accessible when changing colors. Utility class names and internal markup are not a customization API.
+By default, `.commerce-storefront` wrappers do not paint a background and inherit the host's text color. Set page and section backgrounds on the host application's layout elements. `--commerce-surface` colors controls and the opaque cart drawer, and supplies the base for muted colors; it does not color component wrappers. Set `--commerce-surface` and `--commerce-text` together to adapt controls and the drawer to a dark theme. Avoid setting wrapper backgrounds through CSS or the `theme` prop's `background`, `backgroundColor`, or `backgroundImage` properties, which can still override the transparent default. Descendants inherit the surface text and body font instead of global heading styles. Keep text, controls and focus indicators accessible when changing colors. Internal utility class names and markup are not a customization API; use the [product parts](#custom-product-layouts) to change a product page's layout.
 
-The first release uses English UI text and `en-US` currency formatting. Catalog title and description are configurable. Full localization and arbitrary component slots are outside this initial API.
+The first release uses English UI text and `en-US` currency formatting. Catalog title and description are configurable. Full localization is outside this initial API.
 
 ## Compatibility
 
@@ -101,6 +101,7 @@ The repository example uses React Router 7. Follow each router version's own Rea
 | `CommerceStorefront` | Recommended integration: provider and one drawer |
 | `Catalog` | Six products per cursor page, with `title`, `description`, and `showHeader` props |
 | `ProductDetails` | Reads `:productId`; validates URL option selections against catalog results |
+| `ProductDetailsRoot` and product parts | Build a [custom product layout](#custom-product-layouts) with the same rules as `ProductDetails` |
 | `ProductCard` | Renders one `SKUGroup` with direct add or a product-details link |
 | `CartButton` | Opens the shared drawer and displays item count |
 | `AddToCartButton` | Adds a verified `sku`, `name`, and optional integer `quantity` |
@@ -112,6 +113,71 @@ The package exports TypeScript catalog/cart response types and selection/summary
 
 `Catalog` renders its `title` as an H1 by default. When the host page owns its semantic heading, render that page H1 and pass `showHeader={false}` so the document still has exactly one H1.
 
+## Custom product layouts
+
+`ProductDetails` is the recommended product page. When its layout does not fit, compose the same parts inside `ProductDetailsRoot`. The root loads the route's `:productId` and shows the connection, loading, error and not-found states itself, so parts render only once the product exists. This is the packaged layout, written out:
+
+```tsx
+import {
+  ProductDetailsBackLink, ProductDetailsDescription, ProductDetailsGallery, ProductDetailsPrice,
+  ProductDetailsPurchase, ProductDetailsRoot, ProductDetailsTitle,
+} from '@godaddy/gd-commerce-storefront';
+
+<ProductDetailsRoot>
+  <ProductDetailsBackLink className='mb-8 sm:mb-10' />
+  <div className='grid items-start gap-8 lg:grid-cols-12 lg:gap-12'>
+    <ProductDetailsGallery className='min-w-0 lg:col-span-7' />
+    <div className='min-w-0 lg:col-span-5 lg:py-4'>
+      <ProductDetailsTitle />
+      <ProductDetailsPrice className='mt-6' />
+      <ProductDetailsDescription className='my-8' />
+      <ProductDetailsPurchase className='border-t border-neutral-200 pt-8' />
+    </div>
+  </div>
+</ProductDetailsRoot>
+```
+
+The grid, spacing and border classes come from your own stylesheet in a custom layout. Without them, the parts stack in one column with no space between them.
+
+Add your own elements between parts, reorder them, or leave out display parts. `ProductDetailsPurchase` renders the purchase parts below in order. Replace it with individual parts to place options apart from the add button:
+
+| Part | Renders |
+| --- | --- |
+| `ProductDetailsOptions` | A select for every attribute, or the SKU list for products without attributes |
+| `ProductDetailsOption` | A select for one attribute, by `attribute` name; nothing when the product lacks it |
+| `ProductDetailsPurchaseStatus` | The one message explaining why the selection is not purchasable yet; nothing when ready |
+| `ProductDetailsAvailability`, `ProductDetailsQuantity` | Stock and quantity for the verified SKU; nothing before verification |
+| `ProductDetailsAddToCart` | Adds the verified SKU and quantity; before a SKU is verified, its accessible description gives the reason |
+
+Every part is named `ProductDetails*` because it works only inside `ProductDetailsRoot`. `AddToCartButton` is the standalone button for a SKU you already have.
+
+Parts read state from the root and take no product, SKU, price or quantity props. Whatever the layout, only a server-verified SKU can be added, and changing a selection resets the quantity and image. Every part throws if it is rendered outside `ProductDetailsRoot`. In development builds, if no control is rendered for an attribute the product requires, a console warning names the missing ones. A control that mounts later, such as one in a closed accordion, can trigger it; the product becomes purchasable once the control renders. Products without attributes but with several SKUs need `ProductDetailsOptions` or `ProductDetailsPurchase`. Parts can be rendered more than once, such as in a sticky mobile purchase bar; each copy gets its own element IDs.
+
+Every part accepts `className`, which is added to the part's outer element, a wrapper the package's CSS reset leaves alone. Host classes there control margin, padding, border, color, width and grid placement, including layered utilities such as Tailwind v4's. The packaged layout sets its spacing and grid placement this way. Elements inside the part, such as the title's `<h1>`, keep the package's own styles: a host font size on `ProductDetailsTitle` does not change the heading's size, but a host color does reach it, because the heading inherits its color.
+
+Two hooks support custom parts inside the root:
+
+- `useProductDetails()` returns read-only `product`, `name`, `selectedSku`, `quantity`, `availableQuantity`, `images` and `status` (`incomplete`, `checking`, `variant-error`, `unavailable`, `not-purchasable` or `ready`). `selectedSku` is set only when `status` is `ready`.
+- `useProductDetailsOption(attribute)` returns `{ name, label, selected, values, select }` for building swatches or buttons, or `null` when the product has no such attribute. `select(value)` accepts only that attribute's value names, or `null` to clear. Other values are ignored. A hook-based control counts toward the layout check.
+
+```tsx
+function ColorSwatches() {
+  const color = useProductDetailsOption('color');
+  if (!color) return null;
+  return (
+    <div role='group' aria-label={color.label}>
+      {color.values.map((value) => (
+        <button key={value.name} type='button' aria-pressed={value.selected} onClick={() => color.select(value.name)}>
+          {value.label}
+        </button>
+      ))}
+    </div>
+  );
+}
+```
+
+Parts are flat named exports, not properties such as `ProductDetails.Title`, so each one is an ordinary module export.
+
 ## How it works
 
 Products are SKU groups. The package purchases only an unambiguous SKU, verifies all selected attributes through the server, uses SKU prices/images, and distinguishes untracked inventory from sold-out inventory. Server-side inventory and pricing checks remain mandatory.
diff --git a/packages/commerce-storefront/src/artifacts.test.ts b/packages/commerce-storefront/src/artifacts.test.ts
index bea80de5..bea3409f 100644
--- a/packages/commerce-storefront/src/artifacts.test.ts
+++ b/packages/commerce-storefront/src/artifacts.test.ts
@@ -57,13 +57,13 @@ it('inherits host text without painting wrappers while retaining opaque themed c
   });
   expect(controlDeclarations['background-color']).toBe('var(--commerce-surface, #fff)');
   const resets: Record<string, string> = {};
-  css.walkRules('.commerce-storefront :where(*)', (rule) => {
+  css.walkRules('.commerce-storefront :where(*:not(.commerce-part))', (rule) => {
     rule.walkDecls((declaration) => {
       resets[declaration.prop] = declaration.value;
     });
   });
   expect(resets).toMatchObject({ color: 'inherit', 'font-family': 'inherit' });
-  expect(css.toString().indexOf('.commerce-storefront :where(*)')).toBeLessThan(
+  expect(css.toString().indexOf('.commerce-storefront :where(*:not(.commerce-part))')).toBeLessThan(
     css.toString().indexOf('.commerce-storefront .text-commerce-on-accent'),
   );
 });
diff --git a/packages/commerce-storefront/src/index.ts b/packages/commerce-storefront/src/index.ts
index 43a74992..0f467289 100644
--- a/packages/commerce-storefront/src/index.ts
+++ b/packages/commerce-storefront/src/index.ts
@@ -20,5 +20,33 @@ export {
   useCommerce,
 } from './commerce-provider';
 export { CommerceStorefront } from './commerce-storefront';
-export { ProductDetails } from './product-details';
+export {
+  ProductDetails,
+  ProductDetailsBackLink,
+  ProductDetailsDescription,
+  ProductDetailsGallery,
+  ProductDetailsPrice,
+  ProductDetailsTitle,
+} from './product-details';
+export {
+  type ProductDetailsOptionState,
+  type ProductDetailsOptionValueState,
+  type ProductDetailsPartProps,
+  ProductDetailsRoot,
+  type ProductDetailsRootProps,
+  type ProductDetailsState,
+  type ProductDetailsStatus,
+  useProductDetails,
+  useProductDetailsOption,
+} from './product-details-context';
+export {
+  ProductDetailsAddToCart,
+  ProductDetailsAvailability,
+  ProductDetailsOption,
+  type ProductDetailsOptionProps,
+  ProductDetailsOptions,
+  ProductDetailsPurchase,
+  ProductDetailsPurchaseStatus,
+  ProductDetailsQuantity,
+} from './product-purchase';
 export { CommerceStatus } from './storefront-surface';
diff --git a/packages/commerce-storefront/src/product-details-context.tsx b/packages/commerce-storefront/src/product-details-context.tsx
new file mode 100644
index 00000000..0db97811
--- /dev/null
+++ b/packages/commerce-storefront/src/product-details-context.tsx
@@ -0,0 +1,322 @@
+import { useQuery } from '@tanstack/react-query';
+import {
+  createContext,
+  type ReactElement,
+  type ReactNode,
+  useCallback,
+  useContext,
+  useEffect,
+  useRef,
+  useState,
+} from 'react';
+import { Link, useParams, useSearchParams } from 'react-router';
+import { ApiError, message, request } from './api';
+import { buttonClass } from './cart';
+import {
+  getAvailableInventoryQuantity,
+  getImageUrls,
+  getLabeledSkuOptions,
+  getProductAttributes,
+  getSingleMatchedSku,
+  type SKU,
+  type SKUGroup,
+  type SKUPrice,
+  type SkuGroupResult,
+  type StorefrontProductAttribute,
+} from './catalog-model';
+import { useCommerce } from './commerce-provider';
+import { CommerceStatus, StorefrontSurface } from './storefront-surface';
+
+/** Where the shopper is in choosing a purchasable SKU. Only `ready` has a verified `selectedSku`. */
+export type ProductDetailsStatus =
+  | 'incomplete'
+  | 'checking'
+  | 'variant-error'
+  | 'unavailable'
+  | 'not-purchasable'
+  | 'ready';
+
+/** Read-only product state for custom parts rendered inside `ProductDetailsRoot`. */
+export interface ProductDetailsState {
+  readonly product: SKUGroup;
+  readonly name: string;
+  /** Set only after the server verifies the full selection. */
+  readonly selectedSku: SKU | null;
+  readonly quantity: number;
+  /** `null` means inventory is not tracked; `0` means sold out. */
+  readonly availableQuantity: number | null;
+  readonly status: ProductDetailsStatus;
+  readonly images: readonly string[];
+}
+
+interface ProductDetailsInternal extends ProductDetailsState {
+  attributes: StorefrontProductAttribute[];
+  selections: string[];
+  skuOptions: SKU[];
+  explicitSkuId: string;
+  price: SKUPrice | null | undefined;
+  imageIndex: number;
+  variantError: unknown;
+  setImageIndex: (index: number) => void;
+  setQuantity: (quantity: number) => void;
+  selectOption: (attribute: string, value: string) => void;
+  selectSku: (skuId: string) => void;
+  retryVariant: () => void;
+  register: (control: string) => () => void;
+}
+
+/** Props shared by every product part. `className` is added to the part's outer element. */
+export interface ProductDetailsPartProps {
+  className?: string;
+}
+
+export const cx = (...classes: Array<string | undefined>): string => classes.filter(Boolean).join(' ');
+
+/** Classes for the element that receives a part's `className`. The package CSS reset skips `commerce-part`. */
+export const partClass = (...classes: Array<string | undefined>): string => cx('commerce-part', ...classes);
+
+const ProductDetailsContext = createContext<ProductDetailsInternal | null>(null);
+
+export function useProductDetailsInternal(part: string): ProductDetailsInternal {
+  const context = useContext(ProductDetailsContext);
+  if (!context) throw new Error(`${part} must be rendered inside <ProductDetailsRoot>.`);
+  return context;
+}
+
+/** Read the current product, verified SKU, and purchase status from inside `ProductDetailsRoot`. */
+export function useProductDetails(): ProductDetailsState {
+  const { product, name, selectedSku, quantity, availableQuantity, status, images } =
+    useProductDetailsInternal('useProductDetails');
+  return { product, name, selectedSku, quantity, availableQuantity, status, images };
+}
+
+export interface ProductDetailsOptionValueState {
+  readonly name: string;
+  readonly label: string;
+  readonly selected: boolean;
+}
+
+export interface ProductDetailsOptionState {
+  readonly name: string;
+  readonly label: string;
+  readonly selected: string | null;
+  readonly values: readonly ProductDetailsOptionValueState[];
+  /** Accepts only this attribute's own value names, or `null` to clear. Other values are ignored. */
+  readonly select: (value: string | null) => void;
+}
+
+/**
+ * Build a custom control for one product attribute. Returns `null` when the product has no such attribute.
+ * A selection is never purchasable until the server verifies it.
+ */
+export function useProductDetailsOption(attribute: string): ProductDetailsOptionState | null {
+  const { attributes, selections, selectOption, register } =
+    useProductDetailsInternal('useProductDetailsOption');
+  useEffect(() => register(`attribute:${attribute}`), [attribute, register]);
+  const index: number = attributes.findIndex((candidate) => candidate.name === attribute);
+  const match: StorefrontProductAttribute | undefined = attributes[index];
+  if (!match) return null;
+  const selected: string | null = selections[index] || null;
+  return {
+    name: match.name,
+    label: match.label,
+    selected,
+    values: match.values.map((value) => ({
+      name: value.name,
+      label: value.label,
+      selected: value.name === selected,
+    })),
+    select: (value: string | null): void => {
+      if (value === null) selectOption(attribute, '');
+      else if (match.values.some((candidate) => candidate.name === value)) selectOption(attribute, value);
+    },
+  };
+}
+
+/** Register the explicit SKU control so the layout check knows SKU-list products can be completed. */
+export function useSkuOptionRegistration(): void {
+  const { register } = useProductDetailsInternal('ProductDetailsOptions');
+  useEffect(() => register('sku'), [register]);
+}
+
+export interface ProductDetailsRootProps {
+  children: ReactNode;
+  /** Added to the root `<article>`. */
+  className?: string;
+}
+
+/** Loads the product for the route's `:productId` and provides state to product parts. */
+export function ProductDetailsRoot({ children, className }: ProductDetailsRootProps): ReactElement {
+  const { productId = '' } = useParams();
+  const { connection } = useCommerce();
+  return (
+    <StorefrontSurface>
+      {connection === 'ready' ? (
+        <ProductDetailsLoader key={productId} productId={productId} className={className}>
+          {children}
+        </ProductDetailsLoader>
+      ) : (
+        <CommerceStatus />
+      )}
+    </StorefrontSurface>
+  );
+}
+
+function ProductDetailsLoader({
+  productId,
+  className,
+  children,
+}: ProductDetailsRootProps & { productId: string }): ReactElement {
+  const { config } = useCommerce();
+  const [params, setParams] = useSearchParams();
+  const [quantity, setQuantity] = useState<number>(1);
+  const [imageIndex, setImageIndex] = useState<number>(0);
+  const product = useQuery({
+    retry: false,
+    queryKey: ['commerce', config.cartScope, 'product', productId],
+    queryFn: ({ signal }) =>
+      request<SkuGroupResult>(`/products/${encodeURIComponent(productId)}`, {
+        signal,
+        headers: { 'X-Commerce-Scope': config.cartScope },
+      }),
+  });
+  const productNotFound: boolean =
+    product.isError && product.error instanceof ApiError && product.error.status === 404;
+  const group = product.data?.skuGroup;
+  const attributes = getProductAttributes(group);
+  const skuOptions: SKU[] = getLabeledSkuOptions(group);
+  const explicitSku: SKU | undefined = skuOptions.find((sku: SKU): boolean => sku.id === params.get('sku'));
+  const selections: string[] = attributes.map((attribute) => params.get(`option.${attribute.name}`) ?? '');
+  const complete: boolean =
+    skuOptions.length > 0
+      ? !!explicitSku
+      : attributes.every((attribute, index) =>
+          attribute.values.some((value) => value.name === selections[index]),
+        );
+  const selectionParams: URLSearchParams = new URLSearchParams();
+  selections.filter(Boolean).forEach((value) => {
+    selectionParams.append('attributeValues', value);
+  });
+  const matched = useQuery({
+    retry: false,
+    queryKey: ['commerce', config.cartScope, 'product-variants', productId, selections],
+    queryFn: ({ signal }) =>
+      request<SkuGroupResult>(`/products/${encodeURIComponent(productId)}?${selectionParams}`, {
+        signal,
+        headers: { 'X-Commerce-Scope': config.cartScope },
+      }),
+    enabled: !!group && attributes.length > 0 && complete,
+  });
+  const selectionVerified: boolean =
+    complete &&
+    product.isSuccess &&
+    !product.isFetching &&
+    (attributes.length === 0 || (matched.isSuccess && !matched.isFetching));
+  const selectedSku: SKU | null = selectionVerified
+    ? (explicitSku ?? getSingleMatchedSku(attributes.length ? matched.data?.skuGroup : group))
+    : null;
+  const status: ProductDetailsStatus = !complete
+    ? 'incomplete'
+    : matched.isError && !matched.isFetching
+      ? 'variant-error'
+      : !selectionVerified
+        ? 'checking'
+        : selectedSku
+          ? 'ready'
+          : attributes.length
+            ? 'unavailable'
+            : 'not-purchasable';
+  const selectedImages: string[] = getImageUrls(selectedSku);
+  const images: string[] = [...new Set(selectedImages.length ? selectedImages : getImageUrls(group))];
+  const changeSelection = (key: string, value: string): void => {
+    const next: URLSearchParams = new URLSearchParams(params);
+    if (value) next.set(key, value);
+    else next.delete(key);
+    setParams(next);
+    setQuantity(1);
+    setImageIndex(0);
+  };
+  const registered = useRef<Map<string, number>>(new Map());
+  const register = useCallback((control: string): (() => void) => {
+    const counts: Map<string, number> = registered.current;
+    counts.set(control, (counts.get(control) ?? 0) + 1);
+    return () => {
+      const count: number = (counts.get(control) ?? 1) - 1;
+      if (count > 0) counts.set(control, count);
+      else counts.delete(control);
+    };
+  }, []);
+  const requiredControls: string = [
+    ...attributes.map((attribute) => `attribute:${attribute.name}`),
+    ...(skuOptions.length ? ['sku'] : []),
+  ].join('\n');
+  // Parent effects run after child effects, so every mounted control has registered by now. Controls can mount
+  // later (accordions, tabs, sheets), so the warning describes the current render only. Development builds only,
+  // like the peer query library's own checks.
+  useEffect(() => {
+    if (process.env.NODE_ENV === 'production') return;
+    const missing: string[] = requiredControls
+      .split('\n')
+      .filter((control) => control && !registered.current.has(control));
+    if (missing.length === 0) return;
+    console.warn(
+      `[gd-commerce-storefront] No control for ${missing
+        .map((control) => (control === 'sku' ? 'the SKU option' : `"${control.slice('attribute:'.length)}"`))
+        .join(', ')} is rendered right now, so this product cannot be added to the cart until one is. ` +
+        `Render <ProductDetailsOptions />, <ProductDetailsOption attribute='…' /> for each attribute, ` +
+        `or <ProductDetailsPurchase />, or ignore this if the control mounts later.`,
+    );
+  }, [requiredControls]);
+  if (product.isPending) return <p role='status'>Loading product…</p>;
+  if (product.isError && !productNotFound)
+    return (
+      <div role='alert'>
+        <h1 className='text-2xl font-semibold'>Product unavailable</h1>
+        <p className='my-4 text-red-700'>{message(product.error)}</p>
+        <button type='button' className={buttonClass} onClick={() => void product.refetch()}>
+          Retry product
+        </button>
+      </div>
+    );
+  if (productNotFound || !group)
+    return (
+      <div>
+        <h1 className='text-2xl font-semibold'>Product not found</h1>
+        <Link className={`${buttonClass} mt-4`} to={config.catalogPath}>
+          Back to shop
+        </Link>
+      </div>
+    );
+  const value: ProductDetailsInternal = {
+    product: group,
+    name: group.label ?? group.name ?? 'Product',
+    selectedSku,
+    quantity,
+    availableQuantity: getAvailableInventoryQuantity(selectedSku),
+    status,
+    images,
+    attributes,
+    selections,
+    skuOptions,
+    explicitSkuId: explicitSku?.id ?? '',
+    price: selectedSku?.prices?.edges?.find((edge) => edge?.node?.value)?.node,
+    imageIndex: Math.min(imageIndex, Math.max(images.length - 1, 0)),
+    variantError: matched.error,
+    setImageIndex: (index: number): void => {
+      if (Number.isInteger(index) && index >= 0 && index < images.length) setImageIndex(index);
+    },
+    setQuantity,
+    selectOption: (attribute: string, next: string): void => changeSelection(`option.${attribute}`, next),
+    selectSku: (skuId: string): void =>
+      changeSelection('sku', skuOptions.some((sku) => sku.id === skuId) ? skuId : ''),
+    retryVariant: (): void => {
+      if (matched.isError) void matched.refetch();
+    },
+    register,
+  };
+  return (
+    <ProductDetailsContext.Provider value={value}>
+      <article className={partClass(className)}>{children}</article>
+    </ProductDetailsContext.Provider>
+  );
+}
diff --git a/packages/commerce-storefront/src/product-details.test.tsx b/packages/commerce-storefront/src/product-details.test.tsx
new file mode 100644
index 00000000..fd19ec3b
--- /dev/null
+++ b/packages/commerce-storefront/src/product-details.test.tsx
@@ -0,0 +1,344 @@
+import { readFileSync } from 'node:fs';
+import { join } from 'node:path';
+import { QueryClient, QueryClientProvider } from '@tanstack/react-query';
+import { render, screen, waitFor } from '@testing-library/react';
+import userEvent from '@testing-library/user-event';
+import postcss from 'postcss';
+import type { ReactElement, ReactNode } from 'react';
+import { MemoryRouter, Route, Routes } from 'react-router';
+import { describe, expect, it, vi } from 'vitest';
+import type { SKU, SKUGroup } from './catalog-model';
+import { CommerceStorefront } from './commerce-storefront';
+import {
+  ProductDetailsBackLink,
+  ProductDetailsDescription,
+  ProductDetailsGallery,
+  ProductDetailsPrice,
+  ProductDetailsTitle,
+} from './product-details';
+import { ProductDetailsRoot, useProductDetails, useProductDetailsOption } from './product-details-context';
+import {
+  ProductDetailsAddToCart,
+  ProductDetailsAvailability,
+  ProductDetailsOption,
+  ProductDetailsOptions,
+  ProductDetailsPurchase,
+  ProductDetailsPurchaseStatus,
+  ProductDetailsQuantity,
+} from './product-purchase';
+
+const response = (body: unknown, status = 200) => new Response(JSON.stringify(body), { status });
+const sku = (id: string, quantity: number): SKU => ({
+  id,
+  prices: { edges: [{ node: { value: { value: 1200, currencyCode: 'USD' } } }] },
+  inventoryCounts: { edges: [{ node: { type: 'AVAILABLE', quantity } }] },
+});
+const shirt: SKUGroup = {
+  id: 'shirt',
+  label: 'Shirt',
+  attributes: {
+    edges: ['color', 'size'].map((name) => ({
+      node: {
+        name,
+        label: name === 'color' ? 'Color' : 'Size',
+        values: {
+          edges: (name === 'color' ? ['blue', 'red'] : ['s', 'm']).map((value) => ({
+            node: { id: value, name: value, label: value.toUpperCase() },
+          })),
+        },
+      },
+    })),
+  },
+  skus: { totalCount: 4, edges: [] },
+};
+const poster: SKUGroup = {
+  id: 'poster',
+  label: 'Poster',
+  skus: {
+    totalCount: 2,
+    edges: ['small', 'large'].map((size) => ({ node: { ...sku(`poster-${size}`, 3), label: size } })),
+  },
+};
+
+function mockApi(group: SKUGroup = shirt) {
+  const fn = vi.fn((input: RequestInfo | URL, init?: RequestInit) => {
+    const url = new URL(String(input), 'https://host.test');
+    if (url.pathname.endsWith('/config'))
+      return Promise.resolve(response({ cartScope: 's', currencyCode: 'USD' }));
+    if (init?.method === 'POST')
+      return Promise.resolve(response({ cart: { id: 'cart-1', lineItems: [], totals: {} } }, 201));
+    const selected = url.searchParams.getAll('attributeValues');
+    return Promise.resolve(
+      response({
+        skuGroup: selected.length
+          ? { ...group, skus: { totalCount: 1, edges: [{ node: sku(`sku-${selected.join('-')}`, 5) }] } }
+          : group,
+      }),
+    );
+  });
+  vi.stubGlobal('fetch', fn);
+  return fn;
+}
+
+function mount(layout: ReactNode, path = '/products/shirt') {
+  return render(
+    <QueryClientProvider client={new QueryClient({ defaultOptions: { queries: { gcTime: 0 } } })}>
+      <MemoryRouter initialEntries={[path]}>
+        <CommerceStorefront>
+          <Routes>
+            <Route path='/products/:productId' element={layout} />
+          </Routes>
+        </CommerceStorefront>
+      </MemoryRouter>
+    </QueryClientProvider>,
+  );
+}
+
+function Swatches({ attribute }: { attribute: string }): ReactElement | null {
+  const option = useProductDetailsOption(attribute);
+  if (!option) return null;
+  return (
+    <div role='group' aria-label={option.label}>
+      {option.values.map((value) => (
+        <button
+          key={value.name}
+          type='button'
+          aria-pressed={value.selected}
+          onClick={() => option.select(value.name)}
+        >
+          {value.label}
+        </button>
+      ))}
+      <button type='button' onClick={() => option.select('not-a-real-value')}>
+        Invalid
+      </button>
+    </div>
+  );
+}
+
+function SelectedSku(): ReactElement {
+  const { selectedSku, status } = useProductDetails();
+  return <output data-testid='selected'>{`${status}:${selectedSku?.id ?? 'none'}`}</output>;
+}
+
+describe('composable product details', () => {
+  it('purchases through a custom layout with swatches, reordered parts, and host classes', async () => {
+    const api = mockApi();
+    mount(
+      <ProductDetailsRoot className='host-article'>
+        <ProductDetailsTitle className='host-title' />
+        <Swatches attribute='color' />
+        <p>Size guide</p>
+        <ProductDetailsOption attribute='size' />
+        <SelectedSku />
+        <ProductDetailsQuantity />
+        <ProductDetailsAddToCart />
+      </ProductDetailsRoot>,
+    );
+    const title = await screen.findByRole('heading', { level: 1, name: 'Shirt' });
+    expect(title.parentElement).toHaveClass('host-title');
+    expect(title.closest('article')).toHaveClass('host-article');
+    const add = screen.getByRole('button', { name: 'Add to cart' });
+    expect(add).toBeDisabled();
+    expect(add).toHaveAccessibleDescription('Select all options to add this item to your cart.');
+
+    await userEvent.click(screen.getByRole('button', { name: 'Invalid' }));
+    expect(screen.getByTestId('selected')).toHaveTextContent('incomplete:none');
+    await userEvent.click(screen.getByRole('button', { name: 'BLUE' }));
+    expect(screen.getByRole('button', { name: 'BLUE' })).toHaveAttribute('aria-pressed', 'true');
+    expect(screen.getByTestId('selected')).toHaveTextContent('incomplete:none');
+
+    await userEvent.selectOptions(screen.getByRole('combobox', { name: 'Size' }), 'm');
+    await waitFor(() => expect(screen.getByTestId('selected')).toHaveTextContent('ready:sku-blue-m'));
+    await userEvent.clear(screen.getByRole('spinbutton', { name: 'Quantity' }));
+    await userEvent.type(screen.getByRole('spinbutton', { name: 'Quantity' }), '2');
+    await userEvent.click(screen.getByRole('button', { name: 'Add to cart' }));
+    await waitFor(() => expect(api.mock.calls.some((call) => call[1]?.method === 'POST')).toBe(true));
+    const post = api.mock.calls.find((call) => call[1]?.method === 'POST');
+    expect(JSON.parse(String(post?.[1]?.body))).toEqual({
+      lineItems: [{ skuId: 'sku-blue-m', name: 'Shirt', quantity: 2 }],
+    });
+  });
+
+  it('resets quantity when any control changes the selection', async () => {
+    mockApi();
+    mount(
+      <ProductDetailsRoot>
+        <Swatches attribute='color' />
+        <ProductDetailsOption attribute='size' />
+        <ProductDetailsQuantity />
+        <ProductDetailsPurchaseStatus />
+      </ProductDetailsRoot>,
+    );
+    await userEvent.click(await screen.findByRole('button', { name: 'BLUE' }));
+    await userEvent.selectOptions(screen.getByRole('combobox', { name: 'Size' }), 's');
+    const quantity = await screen.findByRole('spinbutton', { name: 'Quantity' });
+    await userEvent.clear(quantity);
+    await userEvent.type(quantity, '4');
+    await userEvent.click(screen.getByRole('button', { name: 'RED' }));
+    expect(await screen.findByRole('spinbutton', { name: 'Quantity' })).toHaveValue(1);
+  });
+
+  it('warns when a layout leaves out an option the product needs', async () => {
+    mockApi();
+    const warn = vi.spyOn(console, 'warn').mockImplementation(() => {});
+    mount(
+      <ProductDetailsRoot>
+        <ProductDetailsOption attribute='color' />
+        <ProductDetailsAddToCart />
+      </ProductDetailsRoot>,
+    );
+    await screen.findByRole('combobox', { name: 'Color' });
+    expect(warn).toHaveBeenCalledWith(expect.stringContaining('No control for "size" is rendered right now'));
+    expect(warn.mock.calls.join('')).not.toMatch(/never/);
+    expect(warn.mock.calls.join('')).not.toContain('"color"');
+  });
+
+  it('does not warn for the packaged purchase area', async () => {
+    mockApi();
+    const warn = vi.spyOn(console, 'warn').mockImplementation(() => {});
+    mount(
+      <ProductDetailsRoot>
+        <ProductDetailsPurchase />
+      </ProductDetailsRoot>,
+    );
+    await screen.findByRole('combobox', { name: 'Size' });
+    expect(warn).not.toHaveBeenCalled();
+  });
+
+  it('names the missing root when a part is rendered outside ProductDetailsRoot', () => {
+    vi.spyOn(console, 'error').mockImplementation(() => {});
+    expect(() => render(<ProductDetailsAddToCart />)).toThrow(
+      'ProductDetailsAddToCart must be rendered inside <ProductDetailsRoot>.',
+    );
+    function Orphan(): null {
+      useProductDetailsOption('color');
+      return null;
+    }
+    expect(() => render(<Orphan />)).toThrow(
+      'useProductDetailsOption must be rendered inside <ProductDetailsRoot>.',
+    );
+  });
+  it('keeps IDs unique and labels attached when purchase parts render twice', async () => {
+    mockApi();
+    const ids = (): string[] => [...document.querySelectorAll('[id]')].map((element) => element.id);
+    const unique = (): void => expect(new Set(ids()).size).toBe(ids().length);
+    mount(
+      <ProductDetailsRoot>
+        <ProductDetailsPurchase />
+        <div data-testid='sticky'>
+          <ProductDetailsQuantity />
+          <ProductDetailsAddToCart />
+        </div>
+      </ProductDetailsRoot>,
+    );
+    const [first, second] = await screen.findAllByRole('button', { name: 'Add to cart' });
+    unique();
+    expect(first).toHaveAccessibleDescription('Select all options to add this item to your cart.');
+    expect(second).toHaveAccessibleDescription('Select all options to add this item to your cart.');
+    await userEvent.selectOptions(screen.getByRole('combobox', { name: 'Color' }), 'blue');
+    await userEvent.selectOptions(screen.getByRole('combobox', { name: 'Size' }), 'm');
+    const quantities = await screen.findAllByRole('spinbutton', { name: 'Quantity' });
+    expect(quantities).toHaveLength(2);
+    unique();
+  });
+
+  it('keeps the SKU list ID unique when the options render twice', async () => {
+    mockApi(poster);
+    mount(
+      <ProductDetailsRoot>
+        <ProductDetailsOptions />
+        <ProductDetailsOptions />
+      </ProductDetailsRoot>,
+      '/products/poster',
+    );
+    const lists = await screen.findAllByRole('combobox', { name: 'Option' });
+    expect(lists).toHaveLength(2);
+    expect(lists[0]?.id).not.toBe(lists[1]?.id);
+  });
+
+  // Package CSS ships unlayered, and unlayered rules beat a host's layered utilities (Tailwind v4) whatever
+  // their specificity. So no package rule may set these properties on the element that receives a host class.
+  it('puts host classes on an element that no package rule styles', async () => {
+    mockApi();
+    const rules: Array<{ selector: string; properties: string[] }> = [];
+    postcss.parse(readFileSync(join(process.cwd(), 'dist/styles.css'), 'utf8')).walkRules((rule) => {
+      if (rule.parent?.type === 'rule') return;
+      // Only direct declarations: nested rules such as space-y-* style children, not this element.
+      const properties: string[] = [];
+      rule.each((node) => {
+        if (node.type === 'decl') properties.push(node.prop);
+      });
+      for (const selector of rule.selectors)
+        if (!selector.includes('::')) rules.push({ selector, properties });
+    });
+    const hostProperties =
+      /^(margin|padding|border-(width|style|top|right|bottom|left)|border$|color$|font-family$)/;
+    const conflicts = (element: Element): string[] =>
+      rules.flatMap(({ selector, properties }) => {
+        let matches = false;
+        try {
+          matches = element.matches(selector);
+        } catch {}
+        return matches
+          ? properties.filter((property) => hostProperties.test(property)).map((p) => `${selector} ${p}`)
+          : [];
+      });
+    const parts: Array<[string, ReactElement]> = [
+      ['BackLink', <ProductDetailsBackLink key='a' className='host' />],
+      ['Gallery', <ProductDetailsGallery key='b' className='host' />],
+      ['Title', <ProductDetailsTitle key='c' className='host' />],
+      ['Price', <ProductDetailsPrice key='d' className='host' />],
+      ['Description', <ProductDetailsDescription key='e' className='host' />],
+      ['Purchase', <ProductDetailsPurchase key='f' className='host' />],
+      ['Options', <ProductDetailsOptions key='g' className='host' />],
+      ['Option', <ProductDetailsOption key='h' attribute='size' className='host' />],
+      ['PurchaseStatus', <ProductDetailsPurchaseStatus key='i' className='host' />],
+      ['AddToCart', <ProductDetailsAddToCart key='j' className='host' />],
+    ];
+    mount(
+      <ProductDetailsRoot className='host'>
+        {parts.map(([name, part]) => (
+          <section key={name} data-part={name}>
+            {part}
+          </section>
+        ))}
+        <section data-part='Ready'>
+          <Swatches attribute='color' />
+          <ProductDetailsAvailability className='host' />
+          <ProductDetailsQuantity className='host' />
+        </section>
+      </ProductDetailsRoot>,
+    );
+    const expectNoConflicts = (count: number): void => {
+      const hosts = [...document.querySelectorAll('.host')];
+      expect(hosts).toHaveLength(count);
+      for (const host of hosts) {
+        const part = host.closest('[data-part]')?.getAttribute('data-part') ?? 'Root';
+        expect({ part, conflicts: conflicts(host) }).toEqual({ part, conflicts: [] });
+      }
+    };
+    await screen.findByRole('heading', { level: 1, name: 'Shirt' });
+    // Every part plus the root; the status message shows until the selection is ready.
+    expectNoConflicts(parts.length + 1);
+    await userEvent.click(screen.getByRole('button', { name: 'BLUE' }));
+    await userEvent.selectOptions(screen.getAllByRole('combobox', { name: 'Size' })[0] as HTMLElement, 'm');
+    await screen.findAllByRole('spinbutton', { name: 'Quantity' });
+    // The status message is gone; availability and quantity appear.
+    expectNoConflicts(parts.length + 1 - 1 + 2);
+  });
+
+  it('does not run the layout check in production builds', async () => {
+    vi.stubEnv('NODE_ENV', 'production');
+    mockApi();
+    const warn = vi.spyOn(console, 'warn').mockImplementation(() => {});
+    mount(
+      <ProductDetailsRoot>
+        <ProductDetailsOption attribute='color' />
+      </ProductDetailsRoot>,
+    );
+    await screen.findByRole('combobox', { name: 'Color' });
+    expect(warn).not.toHaveBeenCalled();
+    vi.unstubAllEnvs();
+  });
+});
diff --git a/packages/commerce-storefront/src/product-details.tsx b/packages/commerce-storefront/src/product-details.tsx
index bd52809f..8b9ceaac 100644
--- a/packages/commerce-storefront/src/product-details.tsx
+++ b/packages/commerce-storefront/src/product-details.tsx
@@ -1,295 +1,121 @@
-import { useQuery } from '@tanstack/react-query';
-import { type ReactElement, useId, useState } from 'react';
-import { Link, useParams, useSearchParams } from 'react-router';
-import { ApiError, message, money, request } from './api';
-import { AddToCartButton, buttonClass, inputClass } from './cart';
+import type { ReactElement } from 'react';
+import { Link } from 'react-router';
+import { money } from './api';
 import { ProductImage } from './catalog';
-import {
-  getAvailableInventoryQuantity,
-  getImageUrls,
-  getLabeledSkuOptions,
-  getProductAttributes,
-  getSingleMatchedSku,
-  type SKU,
-  type SkuGroupResult,
-} from './catalog-model';
 import { useCommerce } from './commerce-provider';
-import { CommerceStatus, StorefrontSurface } from './storefront-surface';
+import {
+  type ProductDetailsPartProps,
+  ProductDetailsRoot,
+  partClass,
+  useProductDetailsInternal,
+} from './product-details-context';
+import { ProductDetailsPurchase } from './product-purchase';
 
+/** The packaged product page for `${productPath}/:productId`. Compose the parts for a custom layout. */
 export function ProductDetails(): ReactElement {
-  const { productId = '' } = useParams();
-  const { connection } = useCommerce();
   return (
-    <StorefrontSurface>
-      {connection === 'ready' ? (
-        <ProductDetailsContent key={productId} productId={productId} />
-      ) : (
-        <CommerceStatus />
-      )}
-    </StorefrontSurface>
+    <ProductDetailsRoot>
+      <ProductDetailsBackLink className='mb-8 sm:mb-10' />
+      <div className='grid items-start gap-8 lg:grid-cols-12 lg:gap-12'>
+        <ProductDetailsGallery className='min-w-0 lg:col-span-7' />
+        <div className='min-w-0 lg:col-span-5 lg:py-4'>
+          <ProductDetailsTitle />
+          <ProductDetailsPrice className='mt-6' />
+          <ProductDetailsDescription className='my-8' />
+          <ProductDetailsPurchase className='border-t border-neutral-200 pt-8' />
+        </div>
+      </div>
+    </ProductDetailsRoot>
   );
 }
 
-function ProductDetailsContent({ productId }: { productId: string }): ReactElement {
+export function ProductDetailsBackLink({ className }: ProductDetailsPartProps): ReactElement {
+  useProductDetailsInternal('ProductDetailsBackLink');
   const { config } = useCommerce();
-  const fieldId = useId();
-  const [params, setParams] = useSearchParams();
-  const [quantity, setQuantity] = useState<number>(1);
-  const [imageIndex, setImageIndex] = useState<number>(0);
-  const product = useQuery({
-    retry: false,
-    queryKey: ['commerce', config.cartScope, 'product', productId],
-    queryFn: ({ signal }) =>
-      request<SkuGroupResult>(`/products/${encodeURIComponent(productId)}`, {
-        signal,
-        headers: { 'X-Commerce-Scope': config.cartScope },
-      }),
-  });
-  const productNotFound: boolean =
-    product.isError && product.error instanceof ApiError && product.error.status === 404;
-  const group = product.data?.skuGroup;
-  const attributes = getProductAttributes(group);
-  const skuOptions: SKU[] = getLabeledSkuOptions(group);
-  const explicitSku: SKU | undefined = skuOptions.find((sku: SKU): boolean => sku.id === params.get('sku'));
-  const selections: string[] = attributes.map((attribute) => params.get(`option.${attribute.name}`) ?? '');
-  const complete: boolean =
-    skuOptions.length > 0
-      ? !!explicitSku
-      : attributes.every((attribute, index) =>
-          attribute.values.some((value) => value.name === selections[index]),
-        );
-  const selectionParams: URLSearchParams = new URLSearchParams();
-  selections.filter(Boolean).forEach((value) => {
-    selectionParams.append('attributeValues', value);
-  });
-  const matched = useQuery({
-    retry: false,
-    queryKey: ['commerce', config.cartScope, 'product-variants', productId, selections],
-    queryFn: ({ signal }) =>
-      request<SkuGroupResult>(`/products/${encodeURIComponent(productId)}?${selectionParams}`, {
-        signal,
-        headers: { 'X-Commerce-Scope': config.cartScope },
-      }),
-    enabled: !!group && attributes.length > 0 && complete,
-  });
-  const selectionVerified: boolean =
-    complete &&
-    product.isSuccess &&
-    !product.isFetching &&
-    (attributes.length === 0 || (matched.isSuccess && !matched.isFetching));
-  const selectedSku: SKU | null = selectionVerified
-    ? (explicitSku ?? getSingleMatchedSku(attributes.length ? matched.data?.skuGroup : group))
-    : null;
-  const skuId: string | null = selectedSku?.id ?? null;
-  const skuPrice = selectedSku?.prices?.edges?.find((edge) => edge?.node?.value)?.node;
-  const selectedImages: string[] = getImageUrls(selectedSku);
-  const images: string[] = [...new Set(selectedImages.length ? selectedImages : getImageUrls(group))];
-  const available: number | null = getAvailableInventoryQuantity(selectedSku);
-  const name: string = group?.label ?? group?.name ?? 'Product';
-  const selectOption = (attribute: string, value: string): void => {
-    const next: URLSearchParams = new URLSearchParams(params);
-    if (value) next.set(`option.${attribute}`, value);
-    else next.delete(`option.${attribute}`);
-    setParams(next);
-    setQuantity(1);
-    setImageIndex(0);
-  };
-  if (product.isPending) return <p role='status'>Loading product…</p>;
-  if (product.isError && !productNotFound)
-    return (
-      <div role='alert'>
-        <h1 className='text-2xl font-semibold'>Product unavailable</h1>
-        <p className='my-4 text-red-700'>{message(product.error)}</p>
-        <button type='button' className={buttonClass} onClick={() => void product.refetch()}>
-          Retry product
-        </button>
-      </div>
-    );
-  if (productNotFound || !group)
-    return (
-      <div>
-        <h1 className='text-2xl font-semibold'>Product not found</h1>
-        <Link className={`${buttonClass} mt-4`} to={config.catalogPath}>
-          Back to shop
-        </Link>
-      </div>
-    );
   return (
-    <article>
+    <div className={partClass(className)}>
       <Link
-        className='mb-8 inline-flex min-h-11 items-center text-sm text-inherit underline underline-offset-4 focus-visible:outline focus-visible:outline-2 sm:mb-10'
+        className='inline-flex min-h-11 items-center text-sm text-inherit underline underline-offset-4 focus-visible:outline focus-visible:outline-2'
         to={config.catalogPath}
       >
         ← Back to shop
       </Link>
-      <div className='grid items-start gap-8 lg:grid-cols-12 lg:gap-12'>
-        <div className='min-w-0 lg:col-span-7'>
-          <div className='aspect-square overflow-hidden rounded-lg'>
-            <ProductImage
-              key={images[imageIndex] ?? images[0]}
-              url={images[imageIndex] ?? images[0]}
-              name={name}
-            />
-          </div>
-          {images.length > 1 && (
-            <div className='mt-4 flex gap-3 overflow-x-auto'>
-              {images.map((url, index) => (
-                <button
-                  type='button'
-                  key={url}
-                  className={`h-20 w-20 shrink-0 overflow-hidden rounded-lg border-2 focus-visible:outline focus-visible:outline-2 focus-visible:outline-offset-2 ${imageIndex === index ? 'border-neutral-900' : 'border-transparent'}`}
-                  aria-label={`View image ${index + 1}`}
-                  aria-pressed={imageIndex === index}
-                  onClick={() => setImageIndex(index)}
-                >
-                  <ProductImage url={url} name='' />
-                </button>
-              ))}
-            </div>
-          )}
-        </div>
-        <div className='min-w-0 lg:col-span-5 lg:py-4'>
-          <h1 className='break-words text-4xl font-semibold leading-tight sm:text-5xl'>{name}</h1>
-          <div
-            aria-live='polite'
-            className='mt-6 flex flex-wrap items-baseline gap-x-3 gap-y-1 text-2xl font-medium'
-            data-testid='product-price'
-          >
-            {skuPrice?.value?.value != null
-              ? money(skuPrice.value.value, skuPrice.value.currencyCode ?? config.currencyCode)
-              : group.priceRange?.min != null
-                ? `From ${money(group.priceRange.min, config.currencyCode)}`
-                : 'Price unavailable'}
-            {skuPrice?.compareAtValue?.value != null &&
-              skuPrice.value?.value != null &&
-              skuPrice.compareAtValue.value > skuPrice.value.value && (
-                <del className='text-lg font-normal'>
-                  {money(
-                    skuPrice.compareAtValue.value,
-                    skuPrice.compareAtValue.currencyCode ?? config.currencyCode,
-                  )}
-                </del>
-              )}
-          </div>
-          <p className='my-8 whitespace-pre-line text-base leading-7'>
-            {selectedSku?.description ?? group.description}
-          </p>
-          <div className='space-y-6 border-t border-neutral-200 pt-8'>
-            {attributes.map((attribute, index) => (
-              <fieldset key={attribute.id || attribute.name}>
-                <legend className='mb-2 font-medium'>{attribute.label}</legend>
-                <select
-                  className={`${inputClass} w-full`}
-                  aria-label={attribute.label}
-                  value={selections[index]}
-                  onChange={(event) => selectOption(attribute.name, event.target.value)}
-                >
-                  <option value=''>Select {attribute.label.toLowerCase()}</option>
-                  {attribute.values.map((value) => (
-                    <option key={value.id || value.name} value={value.name}>
-                      {value.label}
-                    </option>
-                  ))}
-                </select>
-              </fieldset>
-            ))}
-            {skuOptions.length > 0 && (
-              <div>
-                <label htmlFor={`${fieldId}-sku-option`} className='mb-2 block font-medium'>
-                  Option
-                </label>
-                <select
-                  id={`${fieldId}-sku-option`}
-                  className={`${inputClass} w-full`}
-                  value={explicitSku?.id ?? ''}
-                  onChange={(event) => {
-                    const next: URLSearchParams = new URLSearchParams(params);
-                    if (event.target.value) next.set('sku', event.target.value);
-                    else next.delete('sku');
-                    setParams(next);
-                    setQuantity(1);
-                    setImageIndex(0);
-                  }}
-                >
-                  <option value=''>Select an option</option>
-                  {skuOptions.map((sku: SKU) => (
-                    <option key={sku.id} value={sku.id ?? ''}>
-                      {sku.label?.trim() || sku.name?.trim()}
-                    </option>
-                  ))}
-                </select>
-              </div>
-            )}
-            {matched.isError ? (
-              <div role='alert' className='text-red-700'>
-                <p>{message(matched.error)}</p>
-                <button
-                  type='button'
-                  className='min-h-11 bg-white text-red-700 underline'
-                  onClick={() => {
-                    if (matched.isError) void matched.refetch();
-                  }}
-                >
-                  Retry availability
-                </button>
-              </div>
-            ) : null}
-            {!complete && (
-              <p id={`${fieldId}-variant-guidance`} role='status' className='text-sm'>
-                Select all options to add this item to your cart.
-              </p>
-            )}
-            {selectionVerified && attributes.length > 0 && !skuId && (
-              <p role='status' className='text-sm text-red-700'>
-                This combination is unavailable. Choose different options.
-              </p>
-            )}
-            {selectionVerified && attributes.length === 0 && !skuId && (
-              <p className='text-sm'>This product is not currently available to purchase.</p>
-            )}
-            {complete && (product.isFetching || matched.isFetching) && (
-              <p role='status'>Checking this variant…</p>
-            )}
-            {selectedSku && (
-              <>
-                <p className='text-sm' aria-live='polite'>
-                  {available === null
-                    ? 'Available to order'
-                    : available === 0
-                      ? 'This variant is out of stock'
-                      : `${available} available`}
-                </p>
-                <div>
-                  <label htmlFor={`${fieldId}-quantity`} className='mb-2 block font-medium'>
-                    Quantity
-                  </label>
-                  <input
-                    id={`${fieldId}-quantity`}
-                    type='number'
-                    min={1}
-                    max={available ?? undefined}
-                    step={1}
-                    className={`${inputClass} w-28`}
-                    value={Number.isNaN(quantity) ? '' : quantity}
-                    onChange={(event) => setQuantity(event.target.valueAsNumber)}
-                  />
-                </div>
-                <AddToCartButton sku={selectedSku} name={name} quantity={quantity} />
-              </>
-            )}
-            {!selectedSku && (
-              <button
-                type='button'
-                className={`${buttonClass} w-full`}
-                disabled
-                aria-describedby={!complete ? `${fieldId}-variant-guidance` : undefined}
-              >
-                Add to cart
-              </button>
-            )}
-          </div>
-        </div>
+    </div>
+  );
+}
+
+/** Main image with thumbnails; the selected SKU's images replace the product's when present. */
+export function ProductDetailsGallery({ className }: ProductDetailsPartProps): ReactElement {
+  const { images, imageIndex, setImageIndex, name } = useProductDetailsInternal('ProductDetailsGallery');
+  return (
+    <div className={partClass(className)}>
+      <div className='aspect-square overflow-hidden rounded-lg'>
+        <ProductImage key={images[imageIndex]} url={images[imageIndex]} name={name} />
       </div>
-    </article>
+      {images.length > 1 && (
+        <div className='mt-4 flex gap-3 overflow-x-auto'>
+          {images.map((url, index) => (
+            <button
+              type='button'
+              key={url}
+              className={`h-20 w-20 shrink-0 overflow-hidden rounded-lg border-2 focus-visible:outline focus-visible:outline-2 focus-visible:outline-offset-2 ${imageIndex === index ? 'border-neutral-900' : 'border-transparent'}`}
+              aria-label={`View image ${index + 1}`}
+              aria-pressed={imageIndex === index}
+              onClick={() => setImageIndex(index)}
+            >
+              <ProductImage url={url} name='' />
+            </button>
+          ))}
+        </div>
+      )}
+    </div>
+  );
+}
+
+/** The product name as the page's H1. */
+export function ProductDetailsTitle({ className }: ProductDetailsPartProps): ReactElement {
+  const { name } = useProductDetailsInternal('ProductDetailsTitle');
+  return (
+    <div className={partClass(className)}>
+      <h1 className='break-words text-4xl font-semibold leading-tight sm:text-5xl'>{name}</h1>
+    </div>
+  );
+}
+
+/** The verified SKU's price and compare-at price, or the product's starting price. */
+export function ProductDetailsPrice({ className }: ProductDetailsPartProps): ReactElement {
+  const { price, product } = useProductDetailsInternal('ProductDetailsPrice');
+  const { config } = useCommerce();
+  return (
+    <div
+      aria-live='polite'
+      className={partClass('flex flex-wrap items-baseline gap-x-3 gap-y-1 text-2xl font-medium', className)}
+      data-testid='product-price'
+    >
+      {price?.value?.value != null
+        ? money(price.value.value, price.value.currencyCode ?? config.currencyCode)
+        : product.priceRange?.min != null
+          ? `From ${money(product.priceRange.min, config.currencyCode)}`
+          : 'Price unavailable'}
+      {price?.compareAtValue?.value != null &&
+        price.value?.value != null &&
+        price.compareAtValue.value > price.value.value && (
+          <del className='text-lg font-normal'>
+            {money(price.compareAtValue.value, price.compareAtValue.currencyCode ?? config.currencyCode)}
+          </del>
+        )}
+    </div>
+  );
+}
+
+/** The verified SKU's description, or the product's. */
+export function ProductDetailsDescription({ className }: ProductDetailsPartProps): ReactElement {
+  const { selectedSku, product } = useProductDetailsInternal('ProductDetailsDescription');
+  return (
+    <div className={partClass(className)}>
+      <p className='whitespace-pre-line text-base leading-7'>
+        {selectedSku?.description ?? product.description}
+      </p>
+    </div>
   );
 }
diff --git a/packages/commerce-storefront/src/product-purchase.tsx b/packages/commerce-storefront/src/product-purchase.tsx
new file mode 100644
index 00000000..64bade43
--- /dev/null
+++ b/packages/commerce-storefront/src/product-purchase.tsx
@@ -0,0 +1,237 @@
+import { type ReactElement, type ReactNode, useId } from 'react';
+import { message } from './api';
+import { AddToCartButton, buttonClass, inputClass } from './cart';
+import type { SKU } from './catalog-model';
+import {
+  type ProductDetailsPartProps,
+  type ProductDetailsStatus,
+  partClass,
+  useProductDetailsInternal,
+  useProductDetailsOption,
+  useSkuOptionRegistration,
+} from './product-details-context';
+
+const disabledReasons: Record<Exclude<ProductDetailsStatus, 'ready'>, string> = {
+  incomplete: 'Select all options to add this item to your cart.',
+  checking: 'Checking this variant…',
+  'variant-error': 'Availability for this selection could not be checked.',
+  unavailable: 'This combination is unavailable. Choose different options.',
+  'not-purchasable': 'This product is not currently available to purchase.',
+};
+
+// In 0.2.0 the purchase area's option fieldsets and text messages were bare <fieldset>/<p> children of
+// `space-y-6`, and the package reset's `margin: 0` outranked that zero-specificity rule, so they had no gap.
+// Their wrappers now take the gap, so the packaged layout cancels it on those parts to stay visually identical.
+const flush = 'mb-0';
+
+/** The packaged purchase area: options, status, availability, quantity, and add to cart. */
+export function ProductDetailsPurchase({ className }: ProductDetailsPartProps): ReactElement {
+  useProductDetailsInternal('ProductDetailsPurchase');
+  return (
+    <div className={partClass('space-y-6', className)}>
+      <OptionControls />
+      <PurchaseStatusMessage textClassName={flush} />
+      <ProductDetailsAvailability className={flush} />
+      <ProductDetailsQuantity />
+      <ProductDetailsAddToCart />
+    </div>
+  );
+}
+
+/** A select for every product attribute, or the SKU list for products without attributes. */
+export function ProductDetailsOptions({ className }: ProductDetailsPartProps): ReactElement | null {
+  const { attributes, skuOptions } = useProductDetailsInternal('ProductDetailsOptions');
+  if (attributes.length === 0 && skuOptions.length === 0) return null;
+  return (
+    <div className={partClass('space-y-6', className)}>
+      <OptionControls />
+    </div>
+  );
+}
+
+// Unwrapped so the packaged layout keeps the controls as direct children of its own spacing container.
+function OptionControls(): ReactElement {
+  const { attributes, skuOptions } = useProductDetailsInternal('ProductDetailsOptions');
+  return (
+    <>
+      {attributes.map((attribute) => (
+        <ProductDetailsOption
+          key={attribute.id || attribute.name}
+          attribute={attribute.name}
+          className={flush}
+        />
+      ))}
+      {skuOptions.length > 0 && <SkuOption />}
+    </>
+  );
+}
+
+function SkuOption(): ReactElement {
+  const { skuOptions, explicitSkuId, selectSku } = useProductDetailsInternal('ProductDetailsOptions');
+  const id = useId();
+  useSkuOptionRegistration();
+  return (
+    <div>
+      <label htmlFor={id} className='mb-2 block font-medium'>
+        Option
+      </label>
+      <select
+        id={id}
+        className={`${inputClass} w-full`}
+        value={explicitSkuId}
+        onChange={(event) => selectSku(event.target.value)}
+      >
+        <option value=''>Select an option</option>
+        {skuOptions.map((sku: SKU) => (
+          <option key={sku.id} value={sku.id ?? ''}>
+            {sku.label?.trim() || sku.name?.trim()}
+          </option>
+        ))}
+      </select>
+    </div>
+  );
+}
+
+export interface ProductDetailsOptionProps extends ProductDetailsPartProps {
+  /** The attribute `name`, such as `color`. Renders nothing when the product has no such attribute. */
+  attribute: string;
+}
+
+/** A select for one product attribute. Use `useProductDetailsOption` for swatches or other custom controls. */
+export function ProductDetailsOption({
+  attribute,
+  className,
+}: ProductDetailsOptionProps): ReactElement | null {
+  const option = useProductDetailsOption(attribute);
+  if (!option) return null;
+  return (
+    <div className={partClass(className)}>
+      <fieldset>
+        <legend className='mb-2 font-medium'>{option.label}</legend>
+        <select
+          className={`${inputClass} w-full`}
+          aria-label={option.label}
+          value={option.selected ?? ''}
+          onChange={(event) => option.select(event.target.value || null)}
+        >
+          <option value=''>Select {option.label.toLowerCase()}</option>
+          {option.values.map((value) => (
+            <option key={value.name} value={value.name}>
+              {value.label}
+            </option>
+          ))}
+        </select>
+      </fieldset>
+    </div>
+  );
+}
+
+/** The single message explaining why the selection is not yet purchasable. Renders nothing when ready. */
+export function ProductDetailsPurchaseStatus({ className }: ProductDetailsPartProps): ReactElement | null {
+  return <PurchaseStatusMessage className={className} />;
+}
+
+function PurchaseStatusMessage({
+  className,
+  textClassName,
+}: ProductDetailsPartProps & { textClassName?: string }): ReactElement | null {
+  const { status, variantError, retryVariant } = useProductDetailsInternal('ProductDetailsPurchaseStatus');
+  const part = (children: ReactNode, partClassName?: string): ReactElement => (
+    <div className={partClass(partClassName, className)}>{children}</div>
+  );
+  switch (status) {
+    case 'ready':
+      return null;
+    case 'variant-error':
+      return part(
+        <div role='alert' className='text-red-700'>
+          <p>{message(variantError)}</p>
+          <button type='button' className='min-h-11 bg-white text-red-700 underline' onClick={retryVariant}>
+            Retry availability
+          </button>
+        </div>,
+      );
+    case 'unavailable':
+      return part(
+        <p role='status' className='text-sm text-red-700'>
+          {disabledReasons[status]}
+        </p>,
+        textClassName,
+      );
+    case 'not-purchasable':
+      return part(<p className='text-sm'>{disabledReasons[status]}</p>, textClassName);
+    case 'checking':
+      return part(<p role='status'>{disabledReasons[status]}</p>, textClassName);
+    case 'incomplete':
+      return part(
+        <p role='status' className='text-sm'>
+          {disabledReasons[status]}
+        </p>,
+        textClassName,
+      );
+  }
+}
+
+/** Stock for the verified SKU. Renders nothing until a SKU is verified. */
+export function ProductDetailsAvailability({ className }: ProductDetailsPartProps): ReactElement | null {
+  const { selectedSku, availableQuantity } = useProductDetailsInternal('ProductDetailsAvailability');
+  if (!selectedSku) return null;
+  return (
+    <div className={partClass(className)}>
+      <p className='text-sm' aria-live='polite'>
+        {availableQuantity === null
+          ? 'Available to order'
+          : availableQuantity === 0
+            ? 'This variant is out of stock'
+            : `${availableQuantity} available`}
+      </p>
+    </div>
+  );
+}
+
+/** Quantity for the verified SKU. Renders nothing until a SKU is verified. */
+export function ProductDetailsQuantity({ className }: ProductDetailsPartProps): ReactElement | null {
+  const { selectedSku, availableQuantity, quantity, setQuantity } =
+    useProductDetailsInternal('ProductDetailsQuantity');
+  const id = useId();
+  if (!selectedSku) return null;
+  return (
+    <div className={partClass(className)}>
+      <label htmlFor={id} className='mb-2 block font-medium'>
+        Quantity
+      </label>
+      <input
+        id={id}
+        type='number'
+        min={1}
+        max={availableQuantity ?? undefined}
+        step={1}
+        className={`${inputClass} w-28`}
+        value={Number.isNaN(quantity) ? '' : quantity}
+        onChange={(event) => setQuantity(event.target.valueAsNumber)}
+      />
+    </div>
+  );
+}
+
+/** Adds the verified SKU and quantity. While disabled, its accessible description says why. */
+export function ProductDetailsAddToCart({ className }: ProductDetailsPartProps): ReactElement {
+  const { selectedSku, name, quantity, status } = useProductDetailsInternal('ProductDetailsAddToCart');
+  const reasonId = useId();
+  return (
+    <div className={partClass(className)}>
+      {selectedSku ? (
+        <AddToCartButton sku={selectedSku} name={name} quantity={quantity} />
+      ) : (
+        <>
+          <button type='button' className={`${buttonClass} w-full`} disabled aria-describedby={reasonId}>
+            Add to cart
+          </button>
+          <span id={reasonId} hidden>
+            {status === 'ready' ? '' : disabledReasons[status]}
+          </span>
+        </>
+      )}
+    </div>
+  );
+}
diff --git a/packages/commerce-storefront/src/styles.css b/packages/commerce-storefront/src/styles.css
index 3703f60f..fb6b2999 100644
--- a/packages/commerce-storefront/src/styles.css
+++ b/packages/commerce-storefront/src/styles.css
@@ -20,9 +20,12 @@
 
 @layer base {
   .commerce-storefront { color: var(--commerce-text, inherit); font-family: inherit; line-height: 1.5; }
-  .commerce-storefront :where(*) { color: inherit; font-family: inherit; }
-  .commerce-storefront *, .commerce-storefront *::before, .commerce-storefront *::after {
-    box-sizing: border-box; border-width: 0; border-style: solid;
+  /* A part's outer element (.commerce-part) receives host classes. These unlayered resets would beat a host's
+     layered utilities, so they skip it; a plain div needs neither reset. */
+  .commerce-storefront :where(*:not(.commerce-part)) { color: inherit; font-family: inherit; }
+  .commerce-storefront *, .commerce-storefront *::before, .commerce-storefront *::after { box-sizing: border-box; }
+  .commerce-storefront :where(*:not(.commerce-part)), .commerce-storefront *::before, .commerce-storefront *::after {
+    border-width: 0; border-style: solid;
   }
   .commerce-storefront :where(h1,h2,h3,p,ul,dl,dd,fieldset) { margin: 0; padding: 0; }
   .commerce-storefront :where(h1,h2,h3) { font-size: inherit; font-weight: inherit; }