# Confirm with the cart's total

October 10, 2026 · API · Breaking

`expectedTotalMinor` on [POST /v1/carts/:id/confirm](https://developer.layout.link/reference/carts#confirm) must be the cart's `totalMinor`. A confirm that sends the restaurant's total alone (`fees.merchantTotalMinor`) while Layout's service fee applies now answers `400 invalid_request`, and nothing is confirmed or charged. When the fee is waived, the two totals are the same and either confirms.

## Why it matters

The person's card is charged `totalMinor`. A confirm with a smaller number used to go through, so an app could show the restaurant's total, confirm it, and charge the person more than they saw.

## What to do

Show the person the cart's `totalMinor` and send it back unchanged as `expectedTotalMinor`. If the price moved, the answer is still `409 price_changed`.

## Breaking changes

A confirm that sent `fees.merchantTotalMinor` now fails with `400 invalid_request`. The reference has always asked for `totalMinor`. The MCP `order` tool is unchanged.