Mobile API Schema Compatibility Simulator

Mobile apps in the field can be years behind the API they call — nobody force-upgrades every phone the moment a backend ships a new schema. This simulator lines up five clients, each pinned to a fixed API version, all calling one server whose schema you can advance through its version history. Every version boundary is either an additive change (safe for old clients to ignore) or a breaking change (fatal unless something translates it). Toggle the compatibility-shim layer to see the same set of clients go from mostly failing to mostly succeeding, and watch requests fly across the wire as green, amber or red packets depending on how they fared.