Kotlin LanguageSAFE

A collection of Agent Skills Standard and Best Practice for Programming Languages, Frameworks that help our AI Agent follow best practies on frameworks and programming laguages

The instruction file, verbatim from the audited commit — this is the text the model reads, and the surface the audit's instruction layer examines. Quoted here so you can judge it without cloning anything.

---
name: kotlin-language
description: Write idiomatic Kotlin 1.9+ with null safety, sealed classes, data classes, extension functions, delegates, collections, inline/reified generics, and expression syntax. Use for Kotlin language constructs, Java-to-Kotlin migration, lazy delegates, data classes, backing properties, or inline/reified generics; keep language constructs in scope even inside response models, and defer coroutine configuration, Android Context/framework, Retrofit/OkHttp client setup, and other library-specific recipes.
metadata:
  triggers:
    files:
      - "**/*.kt"
      - "**/*.kts"
    keywords:
      - val
      - var
      - "?."
      - "?:"
      - "!!"
      - data class
      - sealed
      - when
      - extension
      - lazy
      - lateinit
      - object
---

# Kotlin Language Patterns

## **Priority: P0 (CRITICAL)**

## Implementation Guidelines

- **Immutability**: Use `val` by default. Only use `var` if mutation required locally.
- **Null Safety**: Use `?` for nullable types. Use safe call `?.` and Elvis `?:` over `!!`.
- **Expressions**: Prefer expression bodies `fun foo() = ...` for one-liners. Use `if`/`try` as expressions.
- **Classes**: Use `data class` for DTOs. Use `sealed interface/class` for state hierarchies (e.g., `Success`, `Error`, `Loading`). Access members as computed property rather than function.
- **Extension Functions**: Prefer over utility classes (`StringUtil`). Keep private/internal if module-specific.
- **Named Arguments**: Use for clarity, especially with booleans or multiple same-type params.
- **String Templates**: Use `"$var"` over concatenation. Use `""` for multiline strings (SQL/JSON).

## Anti-Patterns

- **No !! Operator**: Never use in production; prefer safe calls or requireNotNull.
- **No Java-isms**: Use properties not get/set; prefer top-level functions over companion object statics.
- **No Lateinit Abuse**: Prefer nullable types or lazy delegates instead.
- **No Silenced Errors**: Never swallow exceptions without logging or handling.

## References

- [Sealed Class, When Expression & Extension Examples](references/example.md)


## Canonical response anchors

- Additional task-grounded exact anchors: data class

SAFEgrade B · trust 89/100 Nothing in the source contradicts what it says it does. Grade A is reserved for packages that have also passed the behavioural sandbox.

What the source does

Filesystem

none-observed

Network

none-observed

Shell

none-observed

Dependencies

pinned

Secrets in source

none-found

Findings (0)

No findings outside the package's declared scope.

Gates applied: no_behavioural_pass.