canvas-preview

The "native, web, or both per window" proof: one window hosting a Native SDK canvas (Metal-backed toolbar + sidebar rendered by the widget engine) and a live platform webview side by side.

The webview is an ordinary scene shell view (kind = .webview, parented to the canvas view). The build's web engine backs it: WKWebView with -Dweb-engine=system (default), bundled Chromium with -Dweb-engine=cef — the pane seam below is engine-agnostic, though gpu_surface canvases currently require the system engine on macOS.
UiApp.Options.web_panes keeps the webview snapped to a canvas widget's layout frame — the empty panel carrying the preview-pane semantics label — through install, rebuilds, and resizes.
The model owns url + reload_token (the CenterPane/Preview-tab consumer shape): switching pages navigates, bumping the token reloads.
UiApp.Options.status_item installs a menu-bar extra (macOS NSStatusItem) whose menu items dispatch the same on_command commands as the toolbar buttons.

Run it:

native dev

Automation smoke (from the repo root):

zig build test-canvas-preview-smoke

Headless tests:

native test