A web browser is a text field and a WebKit view. Everything else is opinion.
This page is the demo. Type in the bar above: words search, an address loads the site, all right here.
One window, an address bar, back, forward, reload, tabs. Mac, iPhone and iPad from a handful of SwiftUI files. Type a host and it loads. Type words and it searches the engine you picked.
Rendering, JavaScript, cookies, gestures, autofill: WebKit already does all of it. Blackcomb adds only what WebKit does not. A start page with your reading list, bookmarks and recent pages. Save a page and read it later without a connection, or have it read aloud. Rules per site for zoom, a dark look and blocking images, scripts or pop-ups. Float on the Mac keeps a page above every other app. Pair on iPhone and iPad puts two pages in one window. No accounts, no sync, no telemetry.
Here on the web the frame is an iframe, so sites that refuse framing stay blank and words search Wikipedia. The real app has neither limit.