Eden Installation

Start by installing Eden on your frontend:

bun add @elysiajs/eden
bun add -d elysia

TIP

Eden needs Elysia to infer utilities type.

Make sure to install Elysia with the version matching on the server.

First, export your existing Elysia server type:

// server.ts
import { Elysia, t } from 'elysia'

const app = new Elysia()
    .get('/', () => 'Hi Elysia')
    .get('/id/:id', ({ params: { id } }) => id)
    .post('/mirror', ({ body }) => body, {
        body: t.Object({
            id: t.Number(),
            name: t.String()
        })
    })
    .listen(3000)

export type App = typeof app 

Then consume the Elysia API on client side:

// client.ts
import { treaty } from '@elysiajs/eden'
import type { App } from './server'

const client = treaty<App>('localhost:3000') 

// response: Hi Elysia
const { data: index } = await client.index.get()

// response: 1895
const { data: id } = await client.id({ id: 1895 }).get()

// response: { id: 1895, name: 'Skadi' }
const { data: nendoroid } = await client.mirror.post({
    id: 1895,
    name: 'Skadi'
})

client.

Gotcha

Sometimes Eden may not infer type from Elysia correctly, the following are the most common workaround to fix Eden type inference.

Type Strict

Make sure to enable strict mode in tsconfig.json

{
  "compilerOptions": {
    "strict": true
  }
}

Unmatch Elysia version

Eden depends Elysia class to import Elysia instance and infers type correctly.

Make sure that both client and server have a matching Elysia version.

TypeScript version

Elysia uses newer features and syntax of TypeScript to infer types in a the most performant way. Features like Const Generic and Template Literal are heavily used.

Make sure your client has a minimum TypeScript version if >= 5.0

Method Chaining

To make Eden works, Elysia must be using method chaining

Elysia's type system is complex, methods usually introduce a new type to the instance.

Using method chaining will help save that new type reference.

For example:

import { Elysia } from 'elysia'

new Elysia()
    .state('build', 1)
    // Store is strictly typed
    .get('/', ({ store: { build } }) => build)
    .listen(3000)

Using this, state now returns a new ElysiaInstance type, introducing build into store and replace the current one.

Without using method chaining, Elysia doesn't save the new type when introduced, leading to no type inference.

import { Elysia } from 'elysia'

const app = new Elysia()

app.state('build', 1)

app.get('/', ({ store: { build } }) => build)
Property 'build' does not exist on type '{}'.

app.listen(3000)

We recommend to always use method chaining to provide an accurate type inference.