# Sandbox carts at real restaurants

October 25, 2026 · Sandbox · Breaking

In sandbox, `POST /v1/carts` and the MCP `order` tool build a cart at a real restaurant from that restaurant's menu as Layout holds it, with its real items and choices. No browser opens, and the same code you ship builds it.

## What changed

- **`simulate`** on a sandbox cart picks its ending: `placed` (the default), `failed`, `unconfirmed`, `challenge`, `code`, `card_declined`, `price_changed`, `closed` or `pickup_later`.
- **`latency`**: `realistic` (the default) takes 30 seconds for one item and 10 more for each item after it, at most 90; `instant` skips every wait.
- **`engine`**: `shadow` (the default) builds from the menu Layout holds; `real` builds on the restaurant's own site, 10 a day per developer account.
- Production refuses `simulate`, `latency` and `engine` with `400 invalid_request`, and MCP with `sandbox_only`.
- **`409 menu_not_held`** answers a sandbox cart or menu read at a restaurant whose menu Layout does not hold, or a sandbox cart that names no place.
- **Sandbox places** searches and browses list only restaurants whose menu Layout holds. A list emptied for that reason carries `emptyBecause: "no_held_menu"`.
- **Sandbox `POST /v1/menus`** answers only with the menu Layout holds, the one a sandbox cart is priced from, and never reads one live.
- **MCP `menu`** is on sandbox build sessions, and answers the same way. [mcp-tools.json](https://developer.layout.link/mcp-tools.json) lists the tools a sandbox session reads differently as `sandboxSessionTools`, and the session's own `instructions`.
- **Sandbox places** list a restaurant only when its held menu shows at least 3 items. An option that takes money off reads like `No Rice (-$1.00)`.
- **`soldOut: true`** marks a menu item that is sold out.
- **`GET /v1/usage`** lists sandbox builds that open no browser as `simulated_builds`, 10,000 a day. In sandbox, `builds` counts only builds with `"engine": "real"`.

## What to do

Build sandbox carts with a `placeId` from a sandbox places search. Test each ending with `simulate`, and `"latency": "instant"` in CI. See [Sandbox](https://developer.layout.link/reference/sandbox).

## Breaking changes

A sandbox cart opens the restaurant's site only with `"engine": "real"`. A sandbox cart or menu read at a restaurant whose menu Layout does not hold answers `menu_not_held`. The `GET /v1/usage` pool `test_restaurant_builds` is renamed `simulated_builds`.