# API versions and request ids

October 1, 2026 · API

Two headers for running an integration in production: one that says which version of the API you are on, and one that lets support find your request.

## What changed

- **`Layout-Version`** is a date. The current and only version is `2026-10-01`, and a request without the header gets it. Every answer from an endpoint says which version answered. A version the API does not answer is `400 unsupported_version`.
- **`X-Request-Id`** is on every answer from an endpoint, errors included. Quote it when you write to [developer@layout.link](mailto:developer@layout.link).
- **A versioning policy.** A breaking change ships as a new dated version, is marked breaking here, and the old version keeps working for at least 180 days.

## Why it matters

Pin a version and a breaking change never reaches you until you choose it.

## What to do

Send `Layout-Version: 2026-10-01` in production, and log `X-Request-Id` beside your own request logs. See [Versioning](https://developer.layout.link/reference/versioning).

## Breaking changes

None. Both headers are new, and a request without `Layout-Version` behaves as before.