Racket × first-party native UI · MIT

Racket for logic. Real native apps.

Rivet embeds the Racket CS runtime inside first-party native apps: WinUI 3 on Windows, SwiftUI on macOS — with typed RPC, events, shared state, cancellation and lifecycle over one contract.

View on GitHub Where it fits

Racket backend — declare once

backend.rkt

#lang racket/base
(require rivet/backend)

(define-event progress)
(define-state counter : Int64 0)

(define-rpc (greet [name : String] : String)
  (format "Hello, ~a!" name))

(define-rpc (increment [value : Int64] : Int64)
  (add1 value))

Generated client — call natively

App.swift — generated by raco rivet build

// typed Swift, generated at build time
let text = try await backend.greet(name: "Rivet")
// "Hello, Rivet!"

let next = try await backend.increment(value: 41)
// 42

backend.onProgress { pct in
    // events arrive as typed values
}

Why Rivet

Racket is great at logic. Commercial apps need native UI.

There was no direct path from a Racket backend to the modern first-party desktop stacks. Rivet fills that gap.

First-party native UI

WinUI 3 on Windows, SwiftUI/AppKit on macOS — each platform stays itself.

One backend contract

Typed RPC, events, shared state, cancellation and lifecycle over the same RVT1 protocol.

Generated native clients

raco rivet build generates typed Swift and C++ APIs from your declarations.

Embedded Racket CS

The Racket runtime lives inside the application process — no external backend to manage.

Exact runtime matching

Rivet stages the installed Racket CS runtime and never silently falls back to a nearby version.

Safe threading by design

The native side only sees framed RVT1 messages and generated values.

Positioning

Four projects, four trade-offs.

The Racket desktop stack: Rivet, Glaze, Bezel, Tessera — different trade-offs, not replacements for one another.

	Rivet	Glaze	Bezel	Tessera
UI stack	WinUI 3 / SwiftUI	HTML/CSS/JS + WebView	Qt 6 Widgets	custom GPU-rendered
Native widgets	first-party OS UI	no	Qt widgets	custom drawn
One UI codebase	no	yes	yes	yes
Best fit	platform-native commercial apps	web-tech desktop apps	traditional cross-platform GUI	fully custom declarative UI