Vercel

@mionjs/platform-vercel runs mion as Next.js App Router route handlers. It returns GET, POST, PUT, DELETE and PATCH handlers that you re-export from a catch-all route file.

Installing the Adapter

npm install @mionjs/platform-vercel @mionjs/router

Creating the Handler

import {createVercelHandler} from '@mionjs/platform-vercel';
import './vercel-routes.ts';

export const {GET, POST, PUT, DELETE, PATCH} = createVercelHandler();

import {createMionRouter, Routes} from '@mionjs/router';

// the catch-all handler is mounted under /api, so the router gets that prefix
const mion = createMionRouter({basePath: '/api'});

const routes = {
  sayHello: mion.route((ctx, name: string): string => {
    return `Hello ${name}!`;
  }),
} satisfies Routes;

// the server entry only imports this file
export const myApi = mion.initRoutes(routes);
export type MyApi = typeof myApi;

Catch-all Route

One route file handles every method. Place it in a Next.js App Router catch-all directory, whose [...mion] segment sends every path under /api/ to mion's router.

app/
  api/
    [...mion]/
      route.ts   ← exports GET/POST/PUT/DELETE/PATCH from createVercelHandler()

The same handler also hosts your API inside a Next app, see Hosting the API in Your Next App.

API Base Path

Set basePath: '/api' on the router and the client, and point the client's baseURL at the origin. Putting /api in baseURL does not work: a route path is absolute, so it replaces the base's path and drops the prefix.

// your routes module
const mion = createMionRouter({basePath: '/api'});

// your client
const {routes} = initClient<MyApi>({baseURL: 'https://your-app.vercel.app', basePath: '/api'});

Handler Options

Pass options such as maxBodySize (128 KB by default) and maxBodySizeCap to createVercelHandler. maxBodySizeCap defaults to the 4.5 MB Vercel allows, and Vercel refuses anything bigger before the function runs; override it if Vercel changes it. Each route has its own body limit, and a body stream past it is cancelled with a 413.

import {createVercelHandler} from '@mionjs/platform-vercel';
import './vercel-routes.ts';

export const {GET, POST, PUT, DELETE, PATCH} = createVercelHandler({
  maxBodySize: 512 * 1024,
});

mionVitePlugin({
    runTypes: {
        // required on Edge: no `new Function` at runtime
        emitMode: 'both',
    },
}),