Dark mode regressions don’t show up as crashes—they ship as unreadable text on blurred cards and brand tints that vanish over images. Most teams compute contrast against a theoretical background, not the surface the GPU actually composites.

• Tokenize color roles, not RGBs. Use Asset Catalog roles (Any/Dark plus High Contrast) like Background, Surface, TextPrimary; call them via Color("…").
• Make contrast a debug-time invariant. Add a ViewModifier that asserts using WCAG math on resolved UIColor pairs; log with Logger and honor \.colorSchemeContrast.
• Keep text at 1.0 opacity. Tune Surface opacity or layering; semi-transparent text over Material tends to undercut ratios.
• Validate the background you actually draw. For Material, put a solid role-backed fallback under it and compute against that; then spot-check with Accessibility Inspector on device.
• Preview fast, verify real flows. Some failures appear only with UIKit chrome—probe via UIWindow.overrideUserInterfaceStyle(.dark).

Tradeoff: Choose solid-under-material when you need deterministic checks; prefer pure .ultraThinMaterial when you accept manual, device-first validation.

SwiftUI, UIColor, Logger, and Accessibility Inspector make this practical without shipping runtime overhead.

How are you encoding contrast thresholds in debug and catching violations before code review—asserts, snapshots, or both?