Browser

A fast, native Mac browser in the spirit of Arc, built on Stacks, stx and Craft. "Browser" is a working name.

Native UI. The sidebar, toolbar and command bar are stx screens drawn as AppKit views by Craft's macOS host, with zig-js running the screen logic. The browser's own interface is not a web page.
WebKit pages. Each tab is a WKWebView, shown with <WebView tab="..."> and driven through craft.web. Each profile keeps its own cookies and storage; private tabs keep nothing.
An API inside the app. config/desktop.ts turns on agent, so this project's routes run on 127.0.0.1 while the app is open, reachable only from its own window.

Running it

bun run dev:desktop

builds the screens and the AppKit host, then opens the app. bun run build:desktop builds a signed .app in storage/framework/desktop/macos.

While a needed Craft or stx release is still on its way to npm, point the build at a checkout: CRAFT_MACOS_SRC=<craft>/packages/macos/src/index.ts and STX_NATIVE_SRC=<stx>/packages/stx/src/native/index.ts.

Testing

bun test tests/unit/browser
./buddy lint
./buddy typecheck

The sidebar, tab and command-bar logic lives in resources/functions/browser as plain functions with unit tests, so most behaviour is tested without a window. For the window itself, Craft's host takes --test-dir <dir>: it records the real AppKit view tree in state.json and runs action-<n>.json files (command, press, type, submit, key, hover, appearance, screenshot).

How it is put together

Path	What it holds
`config/desktop.ts`	The Mac app: name, bundle id, WebKit, default-browser registration, permissions, Dock menu, its three screens
`resources/native/Main.stx`	The main window: sidebar, content (one page or a split view), command bar, Library, site controls, find, downloads, Peek, Boosts, onboarding
`resources/native/Little.stx`	The small floating window links from other apps open in; Open in Browser hands the live page to the main window
`resources/native/Settings.stx`	Settings (cmd-,), kept in `craft.storage` and posted to open windows
`resources/functions/browser/sidebar.ts`	Spaces, Favorites, Pinned tabs and folders, Today, split views of up to four tabs; every change returns a new state
`resources/functions/browser/menus.ts`	What right-clicking a row or a space offers, and what each choice does (profiles included)
`resources/functions/browser/theme.ts`	A space's light and dark palettes from one to three colours, with readable text
`resources/functions/browser/order.ts`	Sort keys, so a drag rewrites one row
`resources/functions/browser/pages.ts`	Which tabs have a live page: created on first show, released when they sleep
`resources/functions/browser/hibernation.ts`	When an unseen tab gives its page up
`resources/functions/browser/rank.ts`, `actions.ts`, `suggestions.ts`	Command-bar results: tabs, history, actions and search suggestions, by match quality and frecency
`resources/functions/browser/keymap.ts`	Arc's keyboard shortcuts, as menus
`resources/functions/browser/library.ts`	The Library's archive, history and downloads, grouped by day
`resources/functions/browser/sites.ts`	Per-site settings: the blocker, zoom, camera and microphone answers
`resources/functions/browser/blocker.ts`	very-good-adblock's lists and page scripts handed to WebKit, compiled only when they change
`resources/functions/browser/boosts.ts`	A site's own CSS, JS and zapped elements
`resources/functions/browser/peek.ts`	Which links open over the page instead of as a tab
`resources/functions/browser/settings.ts`	The browser's settings and their defaults
`resources/functions/browser/arc-import.ts`, `onboarding.ts`	Arc's sidebar as this browser's, merged into what is there, and the first-launch steps
`resources/functions/browser/history-client.ts`, `session.ts`	Visits and sidebar changes sent to the agent in batches, and flushed on quit
`app/Desktop/Agent.ts`	Routes only the desktop app serves: history, session, archive, downloads, sites, boosts, suggestions, blocker, Arc import
`app/Desktop/database.ts`	Opens `~/Library/Application Support/Browser/Browser.sqlite` with every model, so one schema covers the file
`app/Desktop/*.ts`	One store and its API per table, plus `arc.ts` (reads copies of Arc's files) and `suggest.ts` (the search engine's suggestions)
`app/Models/`	`HistoryEntry`, `Space`, `SidebarItem`, `SessionValue`, `Download`, `SiteSetting`, `Boost`

The Arc importer only ever reads a copy of Arc's files; it never writes them.

Performance

tests/perf/budgets.test.ts holds the code to the plan's budgets. Measured on an Apple Silicon Mac (Oct 31, 2026), medians:

What	Budget	Measured
Draw a 500-row sidebar (both sections and the tab order)	< 8 ms	0.22 ms
Reorder a row and work out what to save	< 8 ms	0.05 ms
Rank 5,000 tabs and pages for the command bar	< 10 ms	2.5 ms
Search 20,000 history pages (first results)	< 50 ms	2.6 ms
Launch to the sidebar drawn	< 250 ms	about 1.8 s
Host and agent memory, idle	< 120 MB	about 525 MB and 187 MB

The last two miss, and neither is the app's code: almost all of the launch time and the host's memory go to zig-js loading the screen bundle (a one-screen bundle takes 0.7 s and 205 MB), and about 360 KB of every bundle is stx's whole web page runtime, which a native screen mostly does not use. Both are being fixed where they live, in zig-js and in stx's native compiler.