Crashing previews, mis-scoped rollouts, and list cells that re-render on every scroll often point to the same root cause: unscoped dependencies. Treat the SwiftUI environment as a typed policy layer and keep ownership/mutation out of it.

• Centralize cross-cutting concerns in EnvironmentValues (time, Logger, formatting, flags) and set them at a composition root via .environment(_:_:).
• Define custom EnvironmentKeys with safe defaults (e.g., deterministic clock, no-op logging, disabled flags) so previews/tests are predictable.
• Prefer read-only façades over mutable models in