Hkj Spring

Higher-Kinded-J Spring Boot integration (hkj-spring-boot-starter). Use PROACTIVELY whenever the working file or task involves: (1) a Spring controller method (@RestController / @GetMapping / @PostMapping / @PutMapping / @PatchMapping / @DeleteMapping) that returns Either, Validated, EitherOrBoth, EitherOrBothPath, EitherPath, MaybePath, ValidationPath, TryPath, IOPath, CompletableFuturePath, VTaskPath, VStreamPath, or FreePath, including a sparse PATCH via @GenerateMapping on an UpdateSpec (updateFrom returning Edits.Accumulated); (2) a sealed interface or sealed hierarchy named DomainError / *Error / *Failure used as the Left of an Either; (3) Jackson 3.x / tools.jackson serialization of HKJ types, including EitherOrBoth and NonEmptyList; (4) any application.yml / application.properties key under hkj.web.* (including hkj.web.either-or-both-path-enabled and hkj.web.validation-field-error-status), hkj.json.*, hkj.validation.*, hkj.async.*, hkj.virtual-threads.*, hkj.actuator.*, hkj.security.*, or hkj.effect-boundary.*; (5) mapping a domain error to an HTTP status code, including 4xx/5xx codes outside the heuristic table (409 Conflict, 422 Unprocessable Content, 429 Too Many Requests, 503 Service Unavailable); (6) ErrorStatusCodeStrategy, ErrorStatusCodeMapper, DefaultErrorStatusCodeStrategy, or HttpHeaderCarrier (Retry-After, WWW-Authenticate, Location); (7) @WebMvcTest slices that need HkjAutoConfiguration / HkjJacksonAutoConfiguration / HkjWebMvcAutoConfiguration imported; (8) EffectBoundary, @Interpreter, @EnableEffectBoundary, @EffectTest, or returning FreePath from a controller; (9) auto-configuration questions about the starter; (10) calling another service over HTTP and keeping the typed error: @HkjHttpClient on a @HttpExchange interface whose methods return EitherPath / VTaskPath<Either> / MaybePath; spring.http.serviceclient.* configuration (base-url, timeouts) for the client; hkj.client.status-error-mappings; @OnStatus(value=, error=); ResponseErrorDecoder / ResponseErrorDecoderFactory / HkjClientExchange / ClientErrorResponse.retryAfter; decoding the {\"success\":false,\"error\":…} envelope back into a typed error; or a generated <Name>HttpExchange / <Name>Client / <Name>ClientConfiguration.

mkdir -p ~/.claude/skills/hkj-spring
curl -L https://claudskills.com/skills/hkj-spring/SKILL.md \
  -o ~/.claude/skills/hkj-spring/SKILL.md

@misc{hkj-spring-2026,
  author    = {higher-kinded-j},
  title     = {Hkj Spring [Claude Code skill]},
  year      = {2026},
  publisher = {ClaudSkills},
  url       = {https://claudskills.com/skills/hkj-spring/}
}