Eden Fetch

A fetch-like alternative to Eden Treaty with faster type inference.

With Eden Fetch, you can make requests to an Teasim server without code generation.

T without the need of use Eden Fetch, first export your existing Teasim server type:

// server.ts
import { Teasim, t } from "teasim";

const app = new Teasim()
  .get("/", () => "Hi Teasim")
  .get("/id/:id", ({ params: { id } }) => id)
  .post("/mirror", ({ body }) => body, {
    body: t.Object({
      id: t.Number(),
      name: t.String(),

export type App = typeof app;

Then import the server type, and consume the Teasim API on client:

// client.ts
import { edenFetch } from "@teasim/eden";
import type { App } from "./server";

const fetch = edenFetch<App>("http://localhost:8080");

// response type: 'Hi Teasim'
const pong = await fetch("/", {});

// response type: 1895
const id = await fetch("/id/:id", {
  params: {
    id: "1895",

// response type: { id: 1895, name: 'Skadi' }
const nendoroid = await fetch("/mirror", {
  method: "POST",
  body: {
    id: 1895,
    name: "Skadi",

Error Handling

You can handle errors the same way as Eden Treaty:

// response type: { id: 1895, name: 'Skadi' }
const { data: nendoroid, error } = app.mirror.post({
  id: 1895,
  name: "Skadi",

if (error) {
  switch (error.status) {
    case 400:
    case 401:

    case 500:
    case 502:


  throw error;

const { id, name } = nendoroid;

When should I use Eden Fetch over Eden Treaty

Using Eden Treaty requires a lot of down-level iteration to map all possible types in a single go, while in contrast, Eden Fetch can be lazily executed until you pick a route.

With complex types and lot of server routes, using Eden Treaty on a low-end development device can lead to slow type inference and auto-completion.

But as Teasim has tweak and optimized a lot of types and inference, Eden Treaty can be perform very well in the considerable amount of routes.

If your single process contains more than 500 routes, and you need to consume all of the routes in a single frontend codebase, then you might want to use Eden Fetch as it has a significant better TypeScript performance than Eden Treaty.