Kotlin value class vs data class

Core principle

Prefer @JvmInline value class for single-field types that carry domain meaning. Data classes are for aggregating multiple fields.

Review procedure

1. Find single-property wrappers, primitive-heavy APIs, and @Immutable wrappers in UI state.
2. Decide whether the single value is a real domain distinction. If not, keep the primitive or use a typealias.
3. Check whether replacing the type changes equality, serialization, Java interop, or hot-path boxing.
4. Convert only when the domain meaning is clear and the contract changes are acceptable.
5. Re-run the affected compiler/tests; for Compose performance work, re-check compiler reports or recomposition evidence.

Decision flow