Build Plugins -- One-line setup for Gradle or Maven that configures dependencies, preview features, and compile-time checks automatically. This is the recommended way to add Higher-Kinded-J to a project; reach for it first.

Manual Gradle and Maven Setup -- Full build.gradle.kts and pom.xml configuration for the projects that cannot use the build plugin (constrained environments, in-house build frameworks, or a conflicting plugin). The fallback, not the starting point.

Compile-Time Checks -- A javac plugin that detects Path type mismatches at compile time, preventing runtime IllegalArgumentException errors. Follows a strict no-false-positives policy.

Migration Recipes -- The hkj-openrewrite recipe catalogue for upgrading between Higher-Kinded-J releases. Covers the 0.2.x to 0.3.0 arity migration, detection-only effect-algebra helpers, and the 0.5.0 deprecation renames; runnable from Gradle or Maven.

Diagnostics -- The hkjDiagnostics Gradle task or mvn hkj:diagnostics Maven goal that reports your current HKJ configuration, showing exactly which dependencies, compiler arguments, and checks are active.

Traversal Generator Plugins -- The 30 built-in generators that power @GenerateTraversals, covering JDK collections, HKJ core types, and five third-party libraries (Eclipse Collections, Guava, Vavr, Apache Commons, PCollections). Includes a guide to writing your own generator for custom container types.

PCollections Integration -- Tests, benchmarks, and an example that confirm PCollections persistent collections (PVector, PStack) compose with the existing ListKind infrastructure through java.util.List compatibility, with no production code changes.

PCollections Optics -- Seven @GenerateTraversals plugins that recognise PVector, PStack, PSet, PSortedSet, PBag, PMap, and PSortedMap fields and generate type-correct traversals against them.

Claude Code Skills -- Seven bundled skills that bring contextual HKJ guidance directly into your editor. Covers Path selection, optics, effect handlers, the effects-optics bridge, Spring Boot integration, functional core / imperative shell architecture, and AssertJ-based testing with hkj-test.

Testing With hkj-test -- A test-scope dependency that ships fluent AssertJ helpers for every HKJ type. Replaces hand-written unwrapping with assertions that read like the business intent: isRight(), hasJustValue(...), whenExecuted().hasValue(...), and so on across discriminated unions, effect types, and monad transformers.