# Admin SPA

> How boardwalk serves the embedded Vue admin SPA under backend.uri, how the SPA talks to the admin API, and how its TypeScript types come from OpenAPI.

WinterCMS renders its backend on the server with layouts, partials and the AJAX framework. SummerCMS replaces that with one Vue 3 single-page app, built once and embedded in the binary by [boardwalk](/docs/api/boardwalk.md). Plugins do not ship admin pages: they ship YAML and, when they need them, partials and scripts, and the SPA renders every controller from the schemas the admin API serves.

## Serving

cabana mounts the SPA under the admin prefix, `backend.uri` (`/backend` by default; one or more lowercase path segments). `boardwalk.Handler` serves the build:

- Any path under the prefix that is not a file and not under `api/` returns `index.html`, so the SPA's own routes work on reload.
- Paths under `api/` that no API route matches return the admin API's JSON `not_found` error, never the SPA.
- Hashed files under `assets/` are cached for a long time; `index.html` is never cached.
- Every response carries a restrictive Content-Security-Policy, frame denial, `nosniff`, a same-origin referrer policy and `noindex, nofollow`.

The build is path-agnostic: `index.html` holds a placeholder (`boardwalk.BaseToken`) that `boardwalk.RewriteIndex` replaces with the prefix once, when the handler is built. A build without the placeholder fails the start-up.

A plugin route under the admin prefix also fails the start-up: the SPA and the admin API own that whole path.

## How the SPA talks to the server

The SPA signs in through the admin API and keeps the token in the HttpOnly cookie described on [Users and permissions](/docs/backend/users-and-permissions.md). For each screen it loads the controller's localized schema (`schema/list`, `schema/form`), then the records, and renders the fields and columns the schema names. Strings come from `GET <prefix>/api/v1/lang`, the `backend::lang` bundle in the request locale, with CLDR plural forms.

## Types from OpenAPI

The admin API is described by swag annotations in cabana. `scripts/check-admin-openapi.sh` generates the OpenAPI document (`admin/openapi/admin.json`) from them and the SPA's TypeScript types (`admin/src/api/schema.d.ts`) from the document, so the SPA's API client is checked against the server's shapes at compile time. `--check` fails when either committed file is out of date:

```sh
scripts/check-admin-openapi.sh --check
```

## Building the SPA

The SPA's source is the `admin/` Vite project. `npm --prefix admin run build` type-checks it and writes the build to `modules/boardwalk/dist`, which the next `go build` embeds. An application that only uses the framework never builds the SPA: the build is committed with the framework.