@tynd/core

The backend API and frontend client for Tynd — desktop apps in TypeScript.

Prerequisites

Bun is required during development. Tynd's backend runs on Bun (full mode) or an embedded JS engine via @tynd/cli's bundler (lite mode); Node.js is not a supported substitute. Install Bun once:

# macOS / Linux / WSL
curl -fsSL https://bun.sh/install | bash

# Windows (PowerShell)
powershell -c "irm bun.sh/install.ps1 | iex"

End users of built apps need nothing — the runtime ships inside the binary.

Install

bun add @tynd/core @tynd/host

Two entrypoints

// backend/main.ts  (Bun process)
import { app, createEmitter } from "@tynd/core"

// src/App.tsx  (WebView)
import { createBackend, fs, dialog, sql /* …and more */ } from "@tynd/core/client"

Backend — app.start() + typed emitters

import { app, createEmitter } from "@tynd/core"

export const events = createEmitter<{ ready: { message: string } }>()

export async function greet(name: string): Promise<string> {
  return `Hello, ${name}!`
}

app.onReady(() => events.emit("ready", { message: "app is up" }))

app.start({
  frontendDir: import.meta.dir + "/../dist",
  window: { title: "My App", width: 1200, height: 800, center: true },
})

Every exported function becomes callable from the frontend. No codegen.

Frontend — zero-codegen typed RPC

import { createBackend, fs, dialog } from "@tynd/core/client"
import type * as backend from "../backend/main"

const api = createBackend<typeof backend>()
const msg = await api.greet("Alice")   // string ✅ — types flow from backend
api.on("ready", ({ message }) => console.log(message))

// Direct OS APIs — bypass the backend
const file = await dialog.openFile()
const bytes = await fs.readBinary(file!)

OS APIs (@tynd/core/client)

Native integrations — identical surface in both full and lite modes:

app, dialog, tyndWindow, monitors, menu, clipboard, shell, notification, tray, process, fs (+ watcher, handles, symlinks), shortcuts, keyring, autolaunch, store, updater, log, power, security, os, path, http, websocket, sql, sidecar, terminal, compute, workers, singleInstance.

Plus Web-standard re-exports (fetch, WebSocket, crypto, URL, Blob, AbortController, TextEncoder, …) so import * as tynd from "@tynd/core/client" gives you the whole namespace at once.

Full reference: API.md.

Runtime modes

@tynd/core runs on either of Tynd's two native hosts:

| | lite | full | |---|---|---| | JS runtime | embedded interpreter, in-process | Bun, packed into the binary | | Binary size | ~6.5 MB + assets | ~44 MB (Bun compressed) | | Best for | most desktop apps | CPU-bound JS / npm native bindings |

The CLI's bundler swaps in the right module at build time via a define-based dead-code-elimination trick — only one runtime ships in any given binary.

See RUNTIMES.md.

Related packages

• @tynd/cli — tynd create / dev / build / start
• @tynd/host — prebuilt native binaries (downloaded by postinstall)

License

Apache-2.0