Runtimes

Tynd ships two backend runtimes from the same TypeScript source. Switch with one config line:

tynd.config.ts


export default {
  runtime: "full",   // or "lite"
}

This page focuses on the JS surface. For the architectural difference (subprocess vs in-process), see Runtime Modes.

Default to lite

Most desktop apps only need:

Web standards (fetch, WebSocket, EventSource, URL, Blob, TextEncoder, crypto.subtle.digest, …)
Tynd OS APIs (fs, http, sql, process, …)

A ~6.5 MB binary with no Bun to download is a real UX win. Lite doesn’t silently misbehave on the features it doesn’t expose — they’re absent, and your code either runs unmodified or fails fast.

Switch to full when

Your dep graph contains an npm with native bindings you can’t replace (sharp, better-sqlite3, canvas, bcrypt-native, rocksdb).
You have a CPU-bound JS hot path profiled as the bottleneck — JSC JIT is often 10-100× faster than QuickJS interpretation.
You need HTTP/2 or HTTP/3 client (lite’s fetch is HTTP/1.1 only via the HTTP client).
You need full Intl.* (DateTimeFormat, Collator, Segmenter, RelativeTimeFormat).
You need dynamic import(path) at runtime — lite ships a single eval’d bundle.
You specifically depend on Bun.* / node:* APIs.

JS surface parity

Feature	`lite`	`full`
ES2023 language (Promises, classes, Proxy, BigInt, Maps/Sets)	✓	✓
`fetch` + `Request` / `Response` / `Headers`	✓ HTTP/1.1	✓ HTTP/1/2/3
`ReadableStream` (fetch body)	✓	✓
`WritableStream` / `TransformStream` / `CompressionStream`	✗	✓
`Response.clone()` / `Request.clone()`	✗ throws	✓
Streaming upload backpressure	✗ drained first	✓
`WebSocket`	✓	✓
`EventSource`	✓	✓
`AbortController` / `AbortSignal` / `AbortSignal.timeout`	✓	✓
`crypto.getRandomValues` / `crypto.randomUUID`	✓	✓
`crypto.subtle.digest` (SHA-256/384/512)	✓	✓
`crypto.subtle.sign` / `verify` / `importKey` — HMAC	✓	✓
`crypto.subtle` AES / RSA / ECDSA	✗	✓
`TextEncoder` / `TextDecoder`	✓	✓
`URL` / `URLSearchParams`	✓	✓
`Blob` / `File` / `FormData`	✓	✓
`atob` / `btoa`	✓	✓
`structuredClone` (no transfer list)	✓	✓
`structuredClone` with transfer list	✗ throws	✓
`performance.now()`	✓	✓
`console.log/info/warn/error/debug`	✓	✓
`setTimeout` / `setInterval` / `queueMicrotask`	✓	✓
`Bun.`, `Deno.`, `node:*`	✗	✓
`Buffer` (Node global)	✗	✓
`process.*` (Node global)	✗	✓
Dynamic `import(path)`	✗	✓
`SharedArrayBuffer` / `Atomics` / `WeakRef` / `FinalizationRegistry`	✗	✓
Chrome DevTools inspector	✗	✓
Full `Intl.*` (DateTimeFormat, Collator, Segmenter, RelativeTimeFormat)	✗ stub	✓ ICU

Tynd OS APIs — identical on both runtimes

All 26 OS APIs are Rust-backed and work the same way:

app, tyndWindow, monitors, dialog, clipboard, shell, notification, tray, menu, shortcuts, fs, path, os, process, sidecar, store, sql, http, websocket, terminal, workers, compute, keyring, autolaunch, singleInstance, updater.

See the API reference.

Size + startup

	`lite`	`full`
Binary (Windows x64 release)	~6.5 MB host + packed assets	~6.4 MB host + ~37 MB Bun (zstd)
Typical shipped app	~8-10 MB	~44 MB
Cold start	sub-50ms	~200-500ms (spawns Bun)

How to do X in lite

Task	Use
Read / write a file	`fs.readText` / `fs.writeText`
Watch files	`fs.watch`
Hash / RNG bytes	`compute.hash` / `compute.randomBytes`
Spawn subprocess	`process.exec`
Bundled binary (ffmpeg, etc.)	`process.exec(await sidecar.path("ffmpeg"))`
Read env vars	`os.env("API_KEY")`
Persistent k/v	`createStore(ns)`
Embedded SQLite	`sql.open(path)`
WebSocket	`new WebSocket(url)` or `websocket.connect`
HTTP	`fetch(url)` or `http.request`
File picker	`dialog.openFile`
Tray + menu	`tray`, `menu`
Notification	`notification.send`
PTY terminal	`terminal.spawn`
Isolated worker	`workers.spawn`

What full offers that lite doesn’t

Capability	Full only	Workaround in lite
JIT performance for CPU-bound JS	✓	Move hot paths to `compute`, `workers`, or a sidecar
npm with native bindings (sharp, better-sqlite3, canvas, …)	✓	Pure-JS alternative (see below) or switch to full
`Bun.`, `Deno.`, `node:*`	✓	Tynd OS APIs or pure-JS
`Buffer` (Node global)	✓	Use `Uint8Array` — every Tynd API accepts it
`process.env` / `process.exit`	✓	`os.env()`, app-lifecycle handlers
Raw TCP / UDP sockets, HTTP server, DNS lookup	✓	Not exposed in lite yet
HTTP/2, HTTP/3	✓	Server must serve HTTP/1.1 fallback
AES / RSA / ECDSA in `crypto.subtle`	✓	`@noble/ciphers`, `@noble/curves`
Password hashing (argon2id, bcrypt)	✓	`@noble/hashes/argon2`, `bcryptjs`
Full `Intl.*`	✓	`date-fns` / `dayjs` / `i18next`
Dynamic `import()` at runtime	✓	Bundle all modules at build time
`SharedArrayBuffer` / `Atomics`	✓	`workers` with message passing

Pure-JS alternatives (lite-friendly)

Missing	Lib
AES, ChaCha20	`@noble/ciphers`
RSA, ECDSA, Ed25519	`@noble/curves`
argon2id	`@noble/hashes` (argon2 module)
bcrypt	`bcryptjs`
gzip / deflate	`fflate`
brotli	`brotli-dec-wasm`
streams polyfill	`web-streams-polyfill`
`Intl.DateTimeFormat`	`date-fns` / `dayjs`
JWT	`jose`
OAuth	`oauth4webapi`
Markdown	`micromark` / `marked`
YAML	`yaml`