Kotlin Professional Usage

kotlin-professional-usage

Registry Trigger

Use when

• Kotlin code changes coroutine ownership, Flow/StateFlow, null or Java interop, sealed/reified/value/data classes, delegated-property or DSL ownership, or Compose state.
• A compiler, coroutine, framework, generated, or Java boundary can change behavior beyond compilation.

Do not use when

• Kotlin appears only in comments/generated output, or a Java/JVM-only change has no Kotlin source.
• The change is only Android manifest, permission, packaging, signing, or other platform metadata with no Kotlin semantic decision.

Skill Role

Own Kotlin language/library semantics. Leave shared JVM runtime to java-jvm-professional-usage, Android contracts to their domain owner, and generic concerns to specialists.

High-Value Rules

• Give every coroutine a lifecycle owner, parent, dispatcher rationale, cancellation outcome, cleanup path, and observed failure.
• Decide whether a stream is cold, shared, or state-bearing; specify collection lifetime, replay/conflation, backpressure, failure, and slow-consumer behavior.
• Expose StateFlow as current state with an explicit mutation owner and atomic transition rule; do not use it as an unbounded event queue.
• Treat Java platform types and generated/reflection boundaries as unproven null contracts; validate or narrow them before Kotlin assumptions escape.
• Use sealed hierarchies, variance, and reified APIs only after proving closure, compatibility, and generated/reflective behavior.
• Check data/value-class equality, copy depth, boxing, mangling, and Java-callable ABI at every identity or interop boundary.
• Define each delegated property's owner, getValue/setValue effects, lifecycle, interop failure, and verification output.
• In Compose, locate state at its mutation/sharing owner; prove observability, identity, lifecycle-aware collection, and one-way events.

Anti-Patterns

• GlobalScope, an unowned scope, or a default dispatcher hides cancellation, failure, or shutdown.
• A cold Flow is assumed to cache work, or StateFlow/SharedFlow is assumed to preserve every event.
• !!, a platform type, or a generated annotation is treated as runtime null proof.
• Data-class copy, a value wrapper, sealed when, or remember is treated as deep immutability, stable ABI, future exhaustiveness, or durable state.

Stop Conditions

• Stop until behavior-controlling compiler, coroutine, Compose, Java-caller, and deployment versions are known.
• Route bytecode, classloading, JVM executor, GC, and shared runtime lifecycle to java-jvm-professional-usage.
• Route Android components, permissions, lifecycle policy, and packaging to the Android owner.
• Route concurrency, API compatibility, security, persistence, performance, and testing to their owners.

Output Contract

• Kotlin decision with owner and caller paths coroutine stream state type Java ABI DSL Compose lifecycle invalid cancellation outcomes evidence limits and residual risk

Targeted References