Liquid Glass

Overview

Use this skill to bring a macOS SwiftUI app into the modern macOS design system with the least custom chrome possible. Start with standard app structure, toolbars, search placement, sheets, and controls, then add custom Liquid Glass only where the app needs a distinctive surface.

Prefer system-provided glass and adaptive materials over bespoke blur, opaque backgrounds, or custom toolbar/sidebar skins. Audit existing UI for extra fills, scrims, and clipping before adding more effects.

Workflow

1. Read the relevant scene or root view and identify the structural pattern: NavigationSplitView, TabView, sheet presentation, detail/inspector layout, toolbar, or custom floating controls.
2. Remove custom backgrounds or darkening layers behind system sheets, sidebars, and toolbars unless the product explicitly needs them. These can obscure Liquid Glass and interfere with the automatic scroll-edge effect.
3. Update standard SwiftUI structure and controls first.
4. Add custom glassEffect surfaces only for app-specific UI that standard controls do not cover.
5. Validate that glass grouping, transitions, icon treatment, and foreground activation are visually coherent and still usable with pointer and keyboard.
6. If the UI change also affects launch behavior for a SwiftPM GUI app, use build-run-debug so the app runs as a foreground .app bundle rather than as a raw executable.

App Structure

• Prefer NavigationSplitView for hierarchy-driven macOS layouts. Let the sidebar use the system Liquid Glass material instead of painting over it.
• For hero artwork or large media adjacent to a floating sidebar, use backgroundExtensionEffect so the visual can extend beyond the safe area without clipping the subject.
• Keep inspectors visually associated with the current selection and avoid giving them a heavier custom background than the content they inspect.
• If the app uses tabs, keep TabView for persistent top-level sections and preserve each tab's local navigation state.
• Do not force iPhone-only tab bar minimize/accessory behavior onto a Mac app. On macOS, prefer a conventional top toolbar and native tab/search placement.
• If a sheet already uses presentationBackground purely to imitate frosted material, consider removing it and letting the system's new material render.
• For sheet transitions that should visually originate from a toolbar button, make the presenting item the source of a navigation zoom transition and mark the sheet content as the destination.

Toolbars

• Assume toolbar items are rendered on a floating Liquid Glass surface and are grouped automatically.
• Use ToolbarSpacer to communicate grouping:
  • fixed spacing to split related actions into a distinct group,
  • flexible spacing to push a leading action away from a trailing group.
• Use sharedBackgroundVisibility when an item should stand alone without the shared glass background, for example a profile/avatar item.
• Add badge to toolbar item content for notification or status indicators.
• Expect monochrome icon rendering in more toolbar contexts. Use tint only to convey semantic meaning such as a primary action or alert state, not as pure decoration.
• If content underneath a toolbar has extra darkening, blur, or custom background layers, remove them before judging the new automatic scroll-edge effect.
• For dense windows with many floating elements, tune the content's scroll-edge treatment with scrollEdgeEffectStyle instead of building a custom bar background.

Search

• For a search field that applies across a whole split-view hierarchy, attach searchable to the NavigationSplitView, not to just one column.
• When search is secondary and a compact affordance is better, use searchToolbarBehavior instead of hand-rolling a toolbar button and a separate field.
• For a dedicated search page in a multi-tab app, assign the search role to one tab and place searchable on the TabView.
• Make most of the app's content discoverable from search when the field lives in the top-trailing toolbar location.
• On iPad and Mac, expect the dedicated search tab to show a centered field above browsing suggestions rather than a bottom search bar.

Controls

• Prefer standard SwiftUI controls before creating custom glass components.
• Expect bordered buttons to default to a capsule shape at larger sizes. On macOS, mini/small/medium controls preserve a rounded-rectangle shape for denser layouts.
• Use buttonBorderShape when a button shape needs to be explicit.
• Use controlSize to preserve density in inspectors and popovers, and reserve extra-large sizing for truly prominent actions.
• Use the system glass and glass-prominent button styles for primary actions instead of recreating a translucent button background by hand.
• For sliders with discrete values, pass step to get automatic tick marks or provide specific ticks in a ticks closure.
• For sliders that should expand left and right around a baseline, set neutralValue.
• Use Label or standard control initializers for menu items so icons are consistently placed on the leading edge across platforms.
• For custom shapes that must align concentrically with a sheet, card, or window corner, use a concentric rectangle shape with the containerConcentric corner configuration instead of guessing a radius.

Custom Liquid Glass

• Use glassEffect for custom glass surfaces. The default shape is capsule-like and text foregrounds are automatically made vibrant and legible against changing content underneath.
• Pass an explicit shape to glassEffect when a capsule is not the right fit.
• Add tint only when color carries meaning, such as a status or call to action.
• Use glassEffect(... .interactive()) for custom controls or containers with interactive elements so they scale, bounce, and shimmer like system glass.
• Wrap nearby custom glass elements in one GlassEffectContainer. This is a visual correctness rule, not just organization: separate containers cannot sample each other's glass and can produce inconsistent refraction.
• Use glassEffectID with a local @Namespace when matching glass elements should morph between collapsed and expanded states.

Review Checklist

• Standard structures and controls were updated first before adding custom glass.
• Opaque backgrounds, dark scrims, and custom toolbar/sheet fills that fight the system material were removed unless intentionally required.
• searchable is attached at the correct container level for the intended search scope.
• Toolbar grouping uses ToolbarSpacer, sharedBackgroundVisibility, and badge instead of one-off hand-built chrome.
• Icon tint is semantic, not decorative.
• Custom glass elements that sit near each other share a GlassEffectContainer.
• Morphing glass transitions use glassEffectID with a namespace and stable identity.
• Any SwiftPM GUI app used to test the result is launched as a .app bundle, not as a raw executable.

Guardrails

• Do not rebuild system sidebars, toolbars, sheets, or controls from scratch if standard SwiftUI APIs already provide the modern macOS behavior.
• Do not apply custom opaque backgrounds behind a NavigationSplitView sidebar, system toolbar, or sheet just because an older version needed one.
• Do not scatter related glass elements across multiple GlassEffectContainers.
• Do not tint every icon or glass surface for visual variety alone.
• Do not assume an iPhone tab/search behavior is the right answer on macOS. Prefer desktop-native toolbar, split-view, and inspector placement.
• Do not leave a GUI SwiftPM app launching as a bare executable when reviewing Liquid Glass behavior; missing foreground activation can make a design bug look like a rendering bug.

When To Use Other Skills

• Use swiftui-patterns when the main question is scene architecture, sidebar/detail layout, commands, or settings rather than Liquid Glass-specific treatment.
• Use view-refactor when the main issue is file structure, state ownership, and extracting large views before design changes.
• Use appkit-interop when the design requires window, panel, responder-chain, or AppKit-only control behavior.
• Use build-run-debug when you need to launch, verify, or inspect logs for the app after the visual update.