Product Variant Picker

Let shoppers pick size and colour and see price, image, and stock update as they choose.

moderate Forms & Input

What it adds

An option selector on the product page that resolves the chosen combination to a specific variant and updates price, imagery, and availability live.

What your agent is told to do

1
Model options as named groups with ordered values, and map each valid combination to a concrete variant with its own price, stock level, and identifier. The picker resolves a selection to a variant; it does not guess.
2
Update price, availability, and the main image the moment a selection changes, without a page reload and without resetting the other groups the shopper has already chosen.
3
Reflect the selected variant in the URL so a shared or refreshed page opens on the same choice. Read that value on load and apply it before first paint so the page does not visibly switch options.
4
Drive the product's imagery through the existing Product Image Gallery rather than swapping a lone image element. When a variant has its own photos, the gallery switches to them; when it does not, it stays on the product's default set.
5
Do not let an invalid combination be submitted and rejected at add-to-cart. Compute which values are still reachable given the current selection and disable the rest, with a reason on the disabled value.

Edge cases it handles

Combinations that do not exist must be visibly unavailable in the picker, not discovered when add-to-cart fails. Recompute reachable values on every change, and when a shopper's earlier choice becomes impossible, tell them which one you cleared.
The chosen variant belongs in the URL so it survives sharing, refresh, and the back button. Use the same identifier the server understands, and fall back to the default variant if the value is stale or unknown.
Variants can differ in more than price. Weight, shipping class, and tax treatment all change the total, so the picker must surface a changed delivery cost rather than letting it appear as a surprise at checkout.
A variant with no image of its own must fall back to the product's default imagery rather than rendering a broken or empty frame.
Option groups must be keyboard navigable with arrow keys and announced as a named group with a current selection. Colour swatches need a text label as well as the colour; colour alone is not a label.
A product with a single variant should not show a picker at all, and a product with hundreds of combinations needs the groups presented as selects rather than a grid of swatches.
Price and stock must be re-checked server-side when the item is added. The picker's view of availability is a convenience, not authority.
Selecting an out-of-stock but real combination should still be allowed if the app offers back-in-stock notification, so the shopper can register interest rather than hit a dead end.

Definition of done

Choosing options updates price, availability, and imagery without a page reload.
Combinations that do not exist are disabled with a reason, and add-to-cart never fails on an invalid selection.
The selected variant is encoded in the URL and restored on load before first paint.
Variants without their own images fall back to the product default with no broken frame.
Option groups are operable by keyboard and announced with their current selection.
Variant-specific price, weight, and shipping differences are reflected before checkout.
The feature matches the existing design system.
No existing functionality is broken.

Related features

Unit Converter

Voice Dictation

Code Editor Field

How it works

1

Copy the link

Grab the Markdown instruction URL for this feature.
2

Give it to your AI

Paste it into Claude Code, Cursor, v0, Lovable — whatever you build with.
3

It inspects, then implements

Your agent reads your existing app first, then adds the feature to fit it.

Works with your stack

These instructions are written to adapt. They tell the agent to detect your framework, match your existing design system, and reuse what you already have — rather than assuming a particular stack.

Need it tighter than that? Customize the feature and tell it exactly what you're running.