Migration Strategies: The Strangler Fig Pattern

Once canonical components exist, how do you replace thousands of legacy buttons and forms across a giant codebase?

The 'Big Bang' Fallacy: Attempting to rewrite the entire application in one giant PR always fails. It introduces hundreds of merge conflicts, delays feature releases, and causes production outages.

The Strangler Fig Pattern (Incremental Migration):

1. New Features First: Any newly built screen or feature must strictly use the new design system components.
2. High-Impact Flows Second: Migrate the most critical user journeys first (e.g., Login, Signup, Checkout).
3. Leaf Components Upward: Migrate low-level atoms (Buttons, Badges) across the app before attempting complex organisms.
4. Sunset the Old: Gradually 'strangle' legacy code until the old UI library can be safely deleted.