Most guides on Kotlin Multiplatform (KMP) and Compose Multiplatform (CMP) show you how to start a new project from scratch. This book is different. It is written for teams with mature Android and iOS apps already running in production—apps with live users, active development pipelines, and existing legacy code that cannot simply be thrown away.
This is an operational guide. It focuses on the engineering and organizational work that actually makes a migration succeed: evaluating dependencies, sequencing the rollout, handling navigation, maintaining observability, and avoiding the architectural anti-patterns that stall large-scale migrations.
Through detailed, stage-by-stage walks of two real-world sample applications, the book demonstrates how to incrementally untangle platform-specific code and move it to a shared core—without halting feature development or disrupting your ongoing release schedule.
Key Areas Covered - Decision Frameworks: Pragmatic cost models, checklist templates, and risk assessments to help leaders evaluate whether a migration makes sense for their team and codebase.
- Two Real-World Tracks: The book follows two distinct application architectures from start to finish: The Modern Track: Compose on Android and SwiftUI on iOS. The Mixed Track: Legacy XML and Compose on Android, alongside UIKit and SwiftUI on iOS.
- Step-by-Step Code Samples: Every chapter is synchronized with a runnable companion repository on GitHub. Each stage of the migration is isolated in its own directory, allowing you to clone the repo, run the code, and inspect the exact changes side-by-side with the text.
- Operational Integration: Covers the logistics of build system setup, multi-architecture compiler configurations, production crash reporting, telemetry, and fallback/rollback strategies.
- Common Anti-Patterns: Documents specific technical mistakes (like premature UI sharing or asymmetric architectures) and organizational friction points that frequently derail migrations.
