Kotlin

Null safety and coroutines, not a framework pack. No scripts/. Process skills that may load with this one: load-with list.

Iron law

Nullability lives in the type. Prefer immutability. Coroutines cancel.

Tooling / verify

Run the module test task the repo already uses (gradle test, etc.). kotlin compiler warnings stay on.

Idioms a linter misses

• val default. data class for values. No !! unless you can name the invariant.
• Exhaustive when on sealed types.
• Platform types from Java: wrap at the boundary into a nullable or non-null Kotlin type. Do not let String! leak.
• Extension functions stay local to a module unless they are the API.

Errors

• Result or exceptions as the file already does. Do not mix both in one API.
• No empty catch.

Concurrency

• Pass a CoroutineScope in. No GlobalScope.launch.
• Handle cancellation (ensureActive, do not swallow CancellationException).
• Main-safe: no blocking IO on the main/UI dispatcher.
• withContext(Dispatchers.IO) for blocking JDK calls.

Testing

• runTest for coroutines if the project uses it.
• Same JUnit / kotlin.test runner the module already has.

PR review

• New !!: reject without an invariant comment.
• New GlobalScope: reject.
• Java interop boundary typed?

Security

• Same JVM rules as lang-java: parameterized SQL, no concat into ProcessBuilder, no untrusted deserialize.

Always

• val, exhaustive when, structured concurrency.
• Wrap Java platform types at the interop boundary.

Ask first

• Calling a large Java API that returns platform types without a wrapper.
• Adding a coroutine library the module does not use.

Never

• !! as a habit.
• GlobalScope.
• runBlocking on UI or request threads.
• Ignoring cancellation.
• Java-style empty catch.

Red flags

• "It's never null"
• "GlobalScope is simpler"
• "I'll just block this coroutine"