> ## Documentation Index
> Fetch the complete documentation index at: https://docs.knitbundles.com/llms.txt
> Use this file to discover all available pages before exploring further.

# Resolver stages

> Wrap the PDP add-to-cart override pipeline

When a bundle runs with `meta.atcOverride`, the host intercepts the theme’s own add-to-cart via fetch, XHR, and DOM click/submit interceptors. Each step of that pipeline is a **resolver stage** you can wrap:

```js theme={null}
window.nameless.use({
  atcOverride: {
    async resolveProductSelection(ctx, next) {
      var base = await next(); // the built-in behavior
      return Object.assign({}, base, { quantity: 2 });
    },
    shouldOverride(ctx, next) {
      return ctx.trigger === "click" ? next() : false;
    },
  },
});
```

| Stage                     | Purpose                                       | Default return                          | Timeout |
| ------------------------- | --------------------------------------------- | --------------------------------------- | ------- |
| `resolveTargetForm`       | Locate the theme’s product form               | `HTMLFormElement` or `null`             | 1500ms  |
| `resolveProductSelection` | Read variant / quantity from the PDP form     | `{ variantId?, quantity?, productId? }` | 1500ms  |
| `shouldOverride`          | Decide whether to swap this add request       | `true` (must return a boolean)          | 1500ms  |
| `buildPayload`            | Build the cart payload from bundle state      | `{ ok, items, lines, … }`               | 500ms   |
| `transformCartRequest`    | Rewrite the `/cart/add.js` request body       | rebuilt request                         | 500ms   |
| `transformCartResponse`   | Rewrite the cart response                     | synthesized response                    | 500ms   |
| `runPostAdd`              | Post-add side effects (drawer, `after` hooks) | `void`                                  | 1500ms  |

Every resolver receives `(ctx, next)`:

| `ctx` field                                           | Meaning                                                                 |
| ----------------------------------------------------- | ----------------------------------------------------------------------- |
| `bundleId`                                            | Bundle being added                                                      |
| `engine`                                              | Live engine instance for that bundle                                    |
| `pageProductId`                                       | Current PDP product GID, when on a product page                         |
| `pdpCoupledSelectorIds`                               | Selectors coupled to the page product                                   |
| `trigger`                                             | `"click"`, `"submit"`, `"full-page"`, or `"fallback"`                   |
| `transport`                                           | `"fetch"`, `"xhr"`, or `"internal"`                                     |
| `stage`                                               | Fully-qualified stage name, e.g. `atcOverride:buildPayload`             |
| `form`, `selection`, `request`, `payload`, `response` | Populated from the stage onward                                         |
| `debug`, `log`                                        | Debug flag and logger, both driven by `window.nameless.__overrideDebug` |

`next()` runs the rest of the chain and ultimately Knit’s built-in behavior — call it and adjust, rather than reimplementing a stage. If your resolver throws, times out, or returns a shape the host rejects, the host records a warning and falls through to `next()`, so a broken resolver degrades to default behavior instead of breaking the cart.

<Note>
  Override is designed for a main `productSingle` product plus optional `collectionMulti` picks. Collection-only bundles are not a supported override shape.
</Note>

Branch the renderer footer on `snapshot.meta.atcOverride` — omit your own ATC button when it is `true`. See [Renderer function](/renderer-function#pdp-add-to-cart-override) and [Shopify integration](/shopify-integration#add-to-cart-override).