Quickstart

Install @rebilder/gateway in this repository.

WHAT IT DOES
It is middleware. When an AI agent requests one of our URLs with
`Accept: text/markdown`, it answers with a clean markdown rendering of that
page's facts. Every other request — humans, Googlebot, anything that did not ask
for markdown — falls through to the existing pipeline untouched. Same URL, same
substance, different format.

STEPS
1. Read the README of the installed package before writing anything. Do not
   work from memory of this prompt; the API is in
   node_modules/@rebilder/gateway/README.md.
2. Add the dependency with the package manager this repo already uses.
3. Create a gateway config exporting a `GatewayConfig`. Its `sources` resolvers
   map a URL to our own data. Wire the adapter for this repo's framework
   (`/next`, `/node` for Express and Fastify, `/edge` for Workers, `/shopify`).
4. Pass the existing fallthrough into the adapter rather than calling it
   yourself. That is what puts `Vary: Accept` on the HTML response. Without it a
   shared cache can serve markdown to a human or stale HTML to an agent, and it
   will not show up until it is in production behind a CDN.
5. Add a `match` router to `sources` if you can: one pure, synchronous function
   from URL to source kind. It keeps the hot path to a single lookup and it is
   what lets the adapter advertise the markdown alternate.

RULES — these are not style preferences
- Never invent a substantive value. Prices, stock, shipping costs, return
  windows, policy text and dates are read from our source of truth and passed
  through unchanged. If you cannot find where a value lives, stop and ask me.
  Do not approximate, do not use a placeholder that looks real, and do not
  write an example price into a resolver.
- A resolver returns `null` when the URL is not that kind of page. `null` means
  "fall through to HTML", which is always a safe answer.
- Do not change what the HTML pages render. This is additive.
- Do not add a build step, a new service, or a runtime dependency.

WHEN YOU ARE DONE
Tell me which URL patterns you wired and which you deliberately skipped, then
run this against one real URL of EACH kind you wired — not just the first one:

  npx rebilder diff <url>     # shows the agent view and the browser view
  npx rebilder check <url>    # grades the page, names what is missing

An incomplete source map is the most common install defect and it is invisible
until an agent hits the page you missed. Both commands run locally, upload
nothing, and need no account.

If you cannot answer "which URLs now serve markdown", the install is not done.

npm install @rebilder/gateway        # pnpm add / yarn add

// lib/catalog.ts — your source of truth, typed with the gateway's re-exported types
import type { ProductSource, PolicySource } from '@rebilder/gateway'

const PRODUCTS: Record<string, ProductSource> = {
  '/products/alpine-trail-pack-28l': {
    url: 'https://store.example.com/products/alpine-trail-pack-28l',
    title: 'Alpine Trail Pack 28L',
    brand: 'Basecamp Supply Co',
    description:
      'A 28-liter technical daypack: suspended-mesh back panel, magnetic sternum buckle, 3L hydration sleeve, lifetime repair guarantee.',
    price: { amount: 14800, currency: 'USD' }, // minor units — integer cents, never floats
    availability: 'in_stock', // 'in_stock' | 'out_of_stock' | 'preorder' | 'backorder'
    variants: [
      {
        id: 'BSC-ATP28-JUN',
        title: 'Juniper Green',
        price: { amount: 14800, currency: 'USD' },
        availability: 'in_stock',
        options: { Color: 'Juniper Green' },
      },
      {
        id: 'BSC-ATP28-EMB',
        title: 'Ember Orange',
        price: { amount: 14800, currency: 'USD' },
        availability: 'backorder',
        options: { Color: 'Ember Orange' },
      },
    ],
    shipping: {
      summary: 'Free US shipping on orders over $75; standard shipping $6.95.',
      freeThreshold: { amount: 7500, currency: 'USD' },
      regions: ['US', 'CA'],
      etaDays: [3, 6], // [min, max] delivery estimate in days
    },
    returns: {
      summary: '60-day returns. Items must be unused with tags attached.',
      windowDays: 60,
      url: 'https://store.example.com/policies/returns',
    },
    images: [
      { url: 'https://store.example.com/cdn/atp28-front.jpg', alt: 'Alpine Trail Pack 28L, front' },
    ],
    attributes: { Capacity: '28 L', Weight: '1.12 kg (2.47 lb)' },
  },
}

const POLICIES: PolicySource[] = [
  {
    title: 'Shipping policy',
    url: 'https://store.example.com/policies/shipping',
    body: 'Orders placed before 12pm PT ship the same business day. Free US shipping over $75.',
  },
  {
    title: 'Returns policy',
    url: 'https://store.example.com/policies/returns',
    body: '60-day returns. Items must be unused with tags attached. Refunds to the original payment method.',
  },
]

export function getProduct(pathname: string): ProductSource | null {
  return PRODUCTS[pathname] ?? null // null = "not a product page" — the gateway moves on
}

export function getPolicies(pathname: string): PolicySource[] | null {
  return pathname.startsWith('/policies') ? POLICIES : null
}

// lib/gateway-config.ts — wire the gateway to your source of truth
import type { GatewayConfig } from '@rebilder/gateway'
import { getProduct, getPolicies, getCollection } from './catalog' // your code

export const gatewayConfig: GatewayConfig = {
  storeId: 'store_123',
  sources: {
    product:  (url) => getProduct(url.pathname),      // null when not a PDP
    policies: (url) => getPolicies(url.pathname),
    catalog:  (url) => getCollection(url.pathname),
  },
  onEvent: (event) => { /* queue to your analytics sink; fire-and-forget */ },
}

// proxy.ts (Next 16) — middleware.ts on Next ≤15 is identical
import { NextResponse } from 'next/server'
import { createGatewayProxy } from '@rebilder/gateway/next'
import { gatewayConfig } from './lib/gateway-config'

// Pass your fallthrough. The proxy then returns a Response for every request,
// and the HTML half of each negotiated URL gets `Vary: Accept` — see below for
// why that matters more than it looks.
const gateway = createGatewayProxy(gatewayConfig, () => NextResponse.next())

export default gateway

export const config = { matcher: ['/products/:path*', '/policies/:path*', '/collections/:path*'] }

# 1. What an agent gets — clean markdown (note x-rebilder-path: markdown)
curl -si -H 'Accept: text/markdown' https://trymumm.com/trust/refunds

# 2. What a browser (or Googlebot) gets — the canonical HTML, unchanged
curl -si https://trymumm.com/trust/refunds

# [Alpine Trail Pack 28L](https://basecamp-supply.example/products/alpine-trail-pack-28l)

- **Brand:** Basecamp Supply Co
- **Price:** $148.00
- **Availability:** In stock
- **Shipping:** Free US shipping on orders over $75; standard shipping $6.95.

npx rebilder diff https://your-store.example/products/some-product
npx rebilder check https://your-store.example/products/some-product