diff --git a/.idea/scala_compiler.xml b/.idea/scala_compiler.xml
index 5c60cfe..f2eb6d2 100644
--- a/.idea/scala_compiler.xml
+++ b/.idea/scala_compiler.xml
@@ -5,7 +5,7 @@
       <option name="deprecationWarnings" value="true" />
       <option name="uncheckedWarnings" value="true" />
     </profile>
-    <profile name="Gradle 2" modules="NowChessSystems.modules.bot.main,NowChessSystems.modules.bot.scoverage,NowChessSystems.modules.bot.test,NowChessSystems.modules.core.integrationTest,NowChessSystems.modules.core.main,NowChessSystems.modules.core.native-test,NowChessSystems.modules.core.quarkus-generated-sources,NowChessSystems.modules.core.quarkus-test-generated-sources,NowChessSystems.modules.core.scoverage,NowChessSystems.modules.core.test,NowChessSystems.modules.io.integrationTest,NowChessSystems.modules.io.main,NowChessSystems.modules.io.native-test,NowChessSystems.modules.io.quarkus-generated-sources,NowChessSystems.modules.io.quarkus-test-generated-sources,NowChessSystems.modules.io.scoverage,NowChessSystems.modules.io.test,NowChessSystems.modules.rule.main,NowChessSystems.modules.rule.scoverage,NowChessSystems.modules.rule.test,NowChessSystems.modules.ui.main,NowChessSystems.modules.ui.scoverage,NowChessSystems.modules.ui.test">
+    <profile name="Gradle 2" modules="NowChessSystems.modules.bot.main,NowChessSystems.modules.bot.scoverage,NowChessSystems.modules.bot.test,NowChessSystems.modules.core.integrationTest,NowChessSystems.modules.core.main,NowChessSystems.modules.core.native-test,NowChessSystems.modules.core.quarkus-generated-sources,NowChessSystems.modules.core.quarkus-test-generated-sources,NowChessSystems.modules.core.scoverage,NowChessSystems.modules.core.test,NowChessSystems.modules.io.integrationTest,NowChessSystems.modules.io.main,NowChessSystems.modules.io.native-test,NowChessSystems.modules.io.quarkus-generated-sources,NowChessSystems.modules.io.quarkus-test-generated-sources,NowChessSystems.modules.io.scoverage,NowChessSystems.modules.io.test,NowChessSystems.modules.rule.integrationTest,NowChessSystems.modules.rule.main,NowChessSystems.modules.rule.native-test,NowChessSystems.modules.rule.quarkus-generated-sources,NowChessSystems.modules.rule.quarkus-test-generated-sources,NowChessSystems.modules.rule.scoverage,NowChessSystems.modules.rule.test,NowChessSystems.modules.ui.main,NowChessSystems.modules.ui.scoverage,NowChessSystems.modules.ui.test">
       <option name="deprecationWarnings" value="true" />
       <option name="uncheckedWarnings" value="true" />
       <parameters>
diff --git a/build.gradle.kts b/build.gradle.kts
index 39ce424..5127534 100644
--- a/build.gradle.kts
+++ b/build.gradle.kts
@@ -41,6 +41,8 @@ val coverageExclusions = listOf(
     "**/io/src/main/scala/de/nowchess/io/service/resource/IoResource.scala",
     // JacksonConfig — Quarkus lifecycle hook, no testable logic beyond ObjectMapper registration
     "**/io/src/main/scala/de/nowchess/io/service/config/JacksonConfig.scala",
+    //RuleSetRestAdapter - Quarkus integration of rule into core, only testable with Quarkus tests
+    "**/core/src/main/de/nowchess/chess/adapter/RuleSetRestAdapter.scala"
 )
 
 // Converts a Sonar-style glob to a scoverage regex (matched against full source path).
diff --git a/modules/rule/src/main/scala/de/nowchess/rules/RuleSet.scala b/modules/api/src/main/scala/de/nowchess/api/rules/RuleSet.scala
similarity index 98%
rename from modules/rule/src/main/scala/de/nowchess/rules/RuleSet.scala
rename to modules/api/src/main/scala/de/nowchess/api/rules/RuleSet.scala
index f2622bd..535b655 100644
--- a/modules/rule/src/main/scala/de/nowchess/rules/RuleSet.scala
+++ b/modules/api/src/main/scala/de/nowchess/api/rules/RuleSet.scala
@@ -1,7 +1,7 @@
-package de.nowchess.rules
+package de.nowchess.api.rules
 
-import de.nowchess.api.game.GameContext
 import de.nowchess.api.board.Square
+import de.nowchess.api.game.GameContext
 import de.nowchess.api.move.Move
 
 /** Extension point for chess rule variants (standard, Chess960, etc.). All rule queries are stateless: given a
diff --git a/modules/bot/src/main/scala/de/nowchess/bot/bots/ClassicalBot.scala b/modules/bot/src/main/scala/de/nowchess/bot/bots/ClassicalBot.scala
index 0573110..a52e5b9 100644
--- a/modules/bot/src/main/scala/de/nowchess/bot/bots/ClassicalBot.scala
+++ b/modules/bot/src/main/scala/de/nowchess/bot/bots/ClassicalBot.scala
@@ -7,7 +7,7 @@ import de.nowchess.bot.bots.classic.EvaluationClassic
 import de.nowchess.bot.logic.AlphaBetaSearch
 import de.nowchess.bot.util.PolyglotBook
 import de.nowchess.bot.{BotDifficulty, BotMoveRepetition}
-import de.nowchess.rules.RuleSet
+import de.nowchess.api.rules.RuleSet
 import de.nowchess.rules.sets.DefaultRules
 
 final class ClassicalBot(
diff --git a/modules/bot/src/main/scala/de/nowchess/bot/bots/HybridBot.scala b/modules/bot/src/main/scala/de/nowchess/bot/bots/HybridBot.scala
index 3a9147a..fd95d0d 100644
--- a/modules/bot/src/main/scala/de/nowchess/bot/bots/HybridBot.scala
+++ b/modules/bot/src/main/scala/de/nowchess/bot/bots/HybridBot.scala
@@ -9,7 +9,7 @@ import de.nowchess.bot.bots.nnue.EvaluationNNUE
 import de.nowchess.bot.logic.{AlphaBetaSearch, TranspositionTable}
 import de.nowchess.bot.util.PolyglotBook
 import de.nowchess.bot.{BotDifficulty, BotMoveRepetition, Config}
-import de.nowchess.rules.RuleSet
+import de.nowchess.api.rules.RuleSet
 import de.nowchess.rules.sets.DefaultRules
 
 final class HybridBot(
diff --git a/modules/bot/src/main/scala/de/nowchess/bot/bots/NNUEBot.scala b/modules/bot/src/main/scala/de/nowchess/bot/bots/NNUEBot.scala
index 094989d..bfa2c6f 100644
--- a/modules/bot/src/main/scala/de/nowchess/bot/bots/NNUEBot.scala
+++ b/modules/bot/src/main/scala/de/nowchess/bot/bots/NNUEBot.scala
@@ -7,7 +7,7 @@ import de.nowchess.bot.bots.nnue.EvaluationNNUE
 import de.nowchess.bot.logic.AlphaBetaSearch
 import de.nowchess.bot.util.{PolyglotBook, ZobristHash}
 import de.nowchess.bot.{BotDifficulty, BotMoveRepetition}
-import de.nowchess.rules.RuleSet
+import de.nowchess.api.rules.RuleSet
 import de.nowchess.rules.sets.DefaultRules
 
 final class NNUEBot(
diff --git a/modules/bot/src/main/scala/de/nowchess/bot/logic/AlphaBetaSearch.scala b/modules/bot/src/main/scala/de/nowchess/bot/logic/AlphaBetaSearch.scala
index 8a58b21..cf41d70 100644
--- a/modules/bot/src/main/scala/de/nowchess/bot/logic/AlphaBetaSearch.scala
+++ b/modules/bot/src/main/scala/de/nowchess/bot/logic/AlphaBetaSearch.scala
@@ -5,7 +5,7 @@ import de.nowchess.api.game.GameContext
 import de.nowchess.api.move.{Move, MoveType}
 import de.nowchess.bot.ai.Evaluation
 import de.nowchess.bot.util.ZobristHash
-import de.nowchess.rules.RuleSet
+import de.nowchess.api.rules.RuleSet
 import de.nowchess.rules.sets.DefaultRules
 import java.util.concurrent.atomic.{AtomicInteger, AtomicLong}
 
diff --git a/modules/bot/src/test/scala/de/nowchess/bot/AlphaBetaSearchTest.scala b/modules/bot/src/test/scala/de/nowchess/bot/AlphaBetaSearchTest.scala
index 609f977..da826bd 100644
--- a/modules/bot/src/test/scala/de/nowchess/bot/AlphaBetaSearchTest.scala
+++ b/modules/bot/src/test/scala/de/nowchess/bot/AlphaBetaSearchTest.scala
@@ -6,7 +6,7 @@ import de.nowchess.api.move.{Move, MoveType, PromotionPiece}
 import de.nowchess.bot.ai.Evaluation
 import de.nowchess.bot.bots.classic.EvaluationClassic
 import de.nowchess.bot.logic.AlphaBetaSearch
-import de.nowchess.rules.RuleSet
+import de.nowchess.api.rules.RuleSet
 import org.scalatest.funsuite.AnyFunSuite
 import org.scalatest.matchers.should.Matchers
 import de.nowchess.rules.sets.DefaultRules
diff --git a/modules/bot/src/test/scala/de/nowchess/bot/ClassicalBotTest.scala b/modules/bot/src/test/scala/de/nowchess/bot/ClassicalBotTest.scala
index 30b0214..bf53263 100644
--- a/modules/bot/src/test/scala/de/nowchess/bot/ClassicalBotTest.scala
+++ b/modules/bot/src/test/scala/de/nowchess/bot/ClassicalBotTest.scala
@@ -5,7 +5,7 @@ import de.nowchess.api.game.GameContext
 import de.nowchess.api.move.Move
 import de.nowchess.api.move.MoveType
 import de.nowchess.bot.bots.ClassicalBot
-import de.nowchess.rules.RuleSet
+import de.nowchess.api.rules.RuleSet
 import org.scalatest.funsuite.AnyFunSuite
 import org.scalatest.matchers.should.Matchers
 import de.nowchess.rules.sets.DefaultRules
diff --git a/modules/bot/src/test/scala/de/nowchess/bot/HybridBotTest.scala b/modules/bot/src/test/scala/de/nowchess/bot/HybridBotTest.scala
index b1e7e81..bf806c2 100644
--- a/modules/bot/src/test/scala/de/nowchess/bot/HybridBotTest.scala
+++ b/modules/bot/src/test/scala/de/nowchess/bot/HybridBotTest.scala
@@ -6,7 +6,7 @@ import de.nowchess.api.move.{Move, MoveType}
 import de.nowchess.bot.ai.Evaluation
 import de.nowchess.bot.bots.HybridBot
 import de.nowchess.bot.util.{PolyglotBook, PolyglotHash}
-import de.nowchess.rules.RuleSet
+import de.nowchess.api.rules.RuleSet
 import org.scalatest.funsuite.AnyFunSuite
 import org.scalatest.matchers.should.Matchers
 
diff --git a/modules/core/build.gradle.kts b/modules/core/build.gradle.kts
index d057a24..8596d8e 100644
--- a/modules/core/build.gradle.kts
+++ b/modules/core/build.gradle.kts
@@ -48,7 +48,6 @@ dependencies {
     }
 
     implementation(project(":modules:api"))
-    implementation(project(":modules:rule"))
     implementation(project(":modules:bot"))
 
 
@@ -69,6 +68,7 @@ dependencies {
 
 
     testImplementation(project(":modules:io"))
+    testImplementation(project(":modules:rule"))
 
     testImplementation(platform("org.junit:junit-bom:5.13.4"))
     testImplementation("org.junit.jupiter:junit-jupiter")
diff --git a/modules/core/src/main/resources/application.yml b/modules/core/src/main/resources/application.yml
index 1663bc0..bbc7bff 100644
--- a/modules/core/src/main/resources/application.yml
+++ b/modules/core/src/main/resources/application.yml
@@ -6,3 +6,5 @@ quarkus:
   rest-client:
     io-service:
       url: http://localhost:8081
+    rule-service:
+      url: http://localhost:8082
diff --git a/modules/core/src/main/scala/de/nowchess/chess/adapter/RuleSetRestAdapter.scala b/modules/core/src/main/scala/de/nowchess/chess/adapter/RuleSetRestAdapter.scala
new file mode 100644
index 0000000..a281095
--- /dev/null
+++ b/modules/core/src/main/scala/de/nowchess/chess/adapter/RuleSetRestAdapter.scala
@@ -0,0 +1,51 @@
+package de.nowchess.chess.adapter
+
+import de.nowchess.api.board.Square
+import de.nowchess.api.game.GameContext
+import de.nowchess.api.move.Move
+import de.nowchess.chess.client.{RuleMoveRequest, RuleServiceClient, RuleSquareRequest}
+import de.nowchess.api.rules.RuleSet
+import jakarta.enterprise.context.ApplicationScoped
+import jakarta.inject.Inject
+import org.eclipse.microprofile.rest.client.inject.RestClient
+
+import scala.compiletime.uninitialized
+
+@ApplicationScoped
+class RuleSetRestAdapter extends RuleSet:
+
+  // scalafix:off DisableSyntax.var
+  @Inject
+  @RestClient
+  var client: RuleServiceClient = uninitialized
+  // scalafix:on DisableSyntax.var
+
+  def candidateMoves(ctx: GameContext)(sq: Square): List[Move] =
+    client.candidateMoves(RuleSquareRequest(ctx, sq.toString))
+
+  def legalMoves(ctx: GameContext)(sq: Square): List[Move] =
+    client.legalMoves(RuleSquareRequest(ctx, sq.toString))
+
+  def allLegalMoves(ctx: GameContext): List[Move] =
+    client.allLegalMoves(ctx)
+
+  def isCheck(ctx: GameContext): Boolean =
+    client.isCheck(ctx)
+
+  def isCheckmate(ctx: GameContext): Boolean =
+    client.isCheckmate(ctx)
+
+  def isStalemate(ctx: GameContext): Boolean =
+    client.isStalemate(ctx)
+
+  def isInsufficientMaterial(ctx: GameContext): Boolean =
+    client.isInsufficientMaterial(ctx)
+
+  def isFiftyMoveRule(ctx: GameContext): Boolean =
+    client.isFiftyMoveRule(ctx)
+
+  def isThreefoldRepetition(ctx: GameContext): Boolean =
+    client.isThreefoldRepetition(ctx)
+
+  def applyMove(ctx: GameContext)(move: Move): GameContext =
+    client.applyMove(RuleMoveRequest(ctx, move))
diff --git a/modules/core/src/main/scala/de/nowchess/chess/client/RuleServiceClient.scala b/modules/core/src/main/scala/de/nowchess/chess/client/RuleServiceClient.scala
new file mode 100644
index 0000000..b213ef4
--- /dev/null
+++ b/modules/core/src/main/scala/de/nowchess/chess/client/RuleServiceClient.scala
@@ -0,0 +1,74 @@
+package de.nowchess.chess.client
+
+import de.nowchess.api.game.GameContext
+import de.nowchess.api.move.Move
+import jakarta.ws.rs.*
+import jakarta.ws.rs.core.MediaType
+import org.eclipse.microprofile.rest.client.inject.RegisterRestClient
+
+case class RuleSquareRequest(context: GameContext, square: String)
+case class RuleMoveRequest(context: GameContext, move: Move)
+
+@Path("/api/rules")
+@RegisterRestClient(configKey = "rule-service")
+trait RuleServiceClient:
+
+  @POST
+  @Path("/candidate-moves")
+  @Consumes(Array(MediaType.APPLICATION_JSON))
+  @Produces(Array(MediaType.APPLICATION_JSON))
+  def candidateMoves(req: RuleSquareRequest): List[Move]
+
+  @POST
+  @Path("/legal-moves")
+  @Consumes(Array(MediaType.APPLICATION_JSON))
+  @Produces(Array(MediaType.APPLICATION_JSON))
+  def legalMoves(req: RuleSquareRequest): List[Move]
+
+  @POST
+  @Path("/all-legal-moves")
+  @Consumes(Array(MediaType.APPLICATION_JSON))
+  @Produces(Array(MediaType.APPLICATION_JSON))
+  def allLegalMoves(ctx: GameContext): List[Move]
+
+  @POST
+  @Path("/is-check")
+  @Consumes(Array(MediaType.APPLICATION_JSON))
+  @Produces(Array(MediaType.APPLICATION_JSON))
+  def isCheck(ctx: GameContext): Boolean
+
+  @POST
+  @Path("/is-checkmate")
+  @Consumes(Array(MediaType.APPLICATION_JSON))
+  @Produces(Array(MediaType.APPLICATION_JSON))
+  def isCheckmate(ctx: GameContext): Boolean
+
+  @POST
+  @Path("/is-stalemate")
+  @Consumes(Array(MediaType.APPLICATION_JSON))
+  @Produces(Array(MediaType.APPLICATION_JSON))
+  def isStalemate(ctx: GameContext): Boolean
+
+  @POST
+  @Path("/is-insufficient-material")
+  @Consumes(Array(MediaType.APPLICATION_JSON))
+  @Produces(Array(MediaType.APPLICATION_JSON))
+  def isInsufficientMaterial(ctx: GameContext): Boolean
+
+  @POST
+  @Path("/is-fifty-move-rule")
+  @Consumes(Array(MediaType.APPLICATION_JSON))
+  @Produces(Array(MediaType.APPLICATION_JSON))
+  def isFiftyMoveRule(ctx: GameContext): Boolean
+
+  @POST
+  @Path("/is-threefold-repetition")
+  @Consumes(Array(MediaType.APPLICATION_JSON))
+  @Produces(Array(MediaType.APPLICATION_JSON))
+  def isThreefoldRepetition(ctx: GameContext): Boolean
+
+  @POST
+  @Path("/apply-move")
+  @Consumes(Array(MediaType.APPLICATION_JSON))
+  @Produces(Array(MediaType.APPLICATION_JSON))
+  def applyMove(req: RuleMoveRequest): GameContext
diff --git a/modules/core/src/main/scala/de/nowchess/chess/config/JacksonConfig.scala b/modules/core/src/main/scala/de/nowchess/chess/config/JacksonConfig.scala
index 1393880..87b8ba7 100644
--- a/modules/core/src/main/scala/de/nowchess/chess/config/JacksonConfig.scala
+++ b/modules/core/src/main/scala/de/nowchess/chess/config/JacksonConfig.scala
@@ -5,6 +5,8 @@ import com.fasterxml.jackson.databind.ObjectMapper
 import com.fasterxml.jackson.databind.module.SimpleModule
 import com.fasterxml.jackson.module.scala.DefaultScalaModule
 import de.nowchess.api.board.Square
+import de.nowchess.api.move.MoveType
+import de.nowchess.chess.json.{MoveTypeDeserializer, MoveTypeSerializer, SquareDeserializer, SquareSerializer}
 import io.quarkus.jackson.ObjectMapperCustomizer
 import jakarta.inject.Singleton
 
@@ -17,7 +19,11 @@ class JacksonConfig extends ObjectMapperCustomizer:
         new Version(2, 21, 1, null, "com.fasterxml.jackson.module", "jackson-module-scala")
         // scalafix:on DisableSyntax.null
     })
-    val squareModule = new SimpleModule()
-    squareModule.addKeyDeserializer(classOf[Square], new SquareKeyDeserializer())
-    squareModule.addKeySerializer(classOf[Square], new SquareKeySerializer())
-    mapper.registerModule(squareModule)
+    val mod = new SimpleModule()
+    mod.addKeySerializer(classOf[Square], new SquareKeySerializer())
+    mod.addKeyDeserializer(classOf[Square], new SquareKeyDeserializer())
+    mod.addSerializer(classOf[Square], new SquareSerializer())
+    mod.addDeserializer(classOf[Square], new SquareDeserializer())
+    mod.addSerializer(classOf[MoveType], new MoveTypeSerializer())
+    mod.addDeserializer(classOf[MoveType], new MoveTypeDeserializer())
+    mapper.registerModule(mod)
diff --git a/modules/core/src/main/scala/de/nowchess/chess/engine/GameEngine.scala b/modules/core/src/main/scala/de/nowchess/chess/engine/GameEngine.scala
index 0759048..21903ca 100644
--- a/modules/core/src/main/scala/de/nowchess/chess/engine/GameEngine.scala
+++ b/modules/core/src/main/scala/de/nowchess/chess/engine/GameEngine.scala
@@ -8,8 +8,7 @@ import de.nowchess.chess.controller.Parser
 import de.nowchess.chess.observer.*
 import de.nowchess.chess.command.{CommandInvoker, MoveCommand, MoveResult}
 import de.nowchess.api.io.{GameContextExport, GameContextImport}
-import de.nowchess.rules.RuleSet
-import de.nowchess.rules.sets.DefaultRules
+import de.nowchess.api.rules.RuleSet
 
 import scala.concurrent.{ExecutionContext, Future}
 
@@ -18,7 +17,7 @@ import scala.concurrent.{ExecutionContext, Future}
   */
 class GameEngine(
     val initialContext: GameContext = GameContext.initial,
-    val ruleSet: RuleSet = DefaultRules,
+    val ruleSet: RuleSet,
     val participants: Map[Color, Participant] = Map(
       Color.White -> Human(PlayerInfo(PlayerId("p1"), "Player 1")),
       Color.Black -> Human(PlayerInfo(PlayerId("p2"), "Player 2")),
diff --git a/modules/core/src/main/scala/de/nowchess/chess/json/MoveTypeDeserializer.scala b/modules/core/src/main/scala/de/nowchess/chess/json/MoveTypeDeserializer.scala
new file mode 100644
index 0000000..969d614
--- /dev/null
+++ b/modules/core/src/main/scala/de/nowchess/chess/json/MoveTypeDeserializer.scala
@@ -0,0 +1,19 @@
+package de.nowchess.chess.json
+
+import com.fasterxml.jackson.core.{JsonParseException, JsonParser}
+import com.fasterxml.jackson.databind.node.ObjectNode
+import com.fasterxml.jackson.databind.{DeserializationContext, JsonDeserializer}
+import de.nowchess.api.move.{MoveType, PromotionPiece}
+
+class MoveTypeDeserializer extends JsonDeserializer[MoveType]:
+  // scalafix:off DisableSyntax.throw
+  override def deserialize(p: JsonParser, ctx: DeserializationContext): MoveType =
+    val node = p.getCodec.readTree[ObjectNode](p)
+    node.get("type").asText() match
+      case "normal"          => MoveType.Normal(node.get("isCapture").asBoolean(false))
+      case "castleKingside"  => MoveType.CastleKingside
+      case "castleQueenside" => MoveType.CastleQueenside
+      case "enPassant"       => MoveType.EnPassant
+      case "promotion"       => MoveType.Promotion(PromotionPiece.valueOf(node.get("piece").asText()))
+      case t                 => throw new JsonParseException(p, s"Unknown move type: $t")
+  // scalafix:on DisableSyntax.throw
diff --git a/modules/core/src/main/scala/de/nowchess/chess/json/MoveTypeSerializer.scala b/modules/core/src/main/scala/de/nowchess/chess/json/MoveTypeSerializer.scala
new file mode 100644
index 0000000..8d90eba
--- /dev/null
+++ b/modules/core/src/main/scala/de/nowchess/chess/json/MoveTypeSerializer.scala
@@ -0,0 +1,23 @@
+package de.nowchess.chess.json
+
+import com.fasterxml.jackson.core.JsonGenerator
+import com.fasterxml.jackson.databind.{JsonSerializer, SerializerProvider}
+import de.nowchess.api.move.MoveType
+
+class MoveTypeSerializer extends JsonSerializer[MoveType]:
+  override def serialize(value: MoveType, gen: JsonGenerator, provider: SerializerProvider): Unit =
+    gen.writeStartObject()
+    value match
+      case MoveType.Normal(isCapture) =>
+        gen.writeStringField("type", "normal")
+        gen.writeBooleanField("isCapture", isCapture)
+      case MoveType.CastleKingside =>
+        gen.writeStringField("type", "castleKingside")
+      case MoveType.CastleQueenside =>
+        gen.writeStringField("type", "castleQueenside")
+      case MoveType.EnPassant =>
+        gen.writeStringField("type", "enPassant")
+      case MoveType.Promotion(piece) =>
+        gen.writeStringField("type", "promotion")
+        gen.writeStringField("piece", piece.toString)
+    gen.writeEndObject()
diff --git a/modules/core/src/main/scala/de/nowchess/chess/json/SquareDeserializer.scala b/modules/core/src/main/scala/de/nowchess/chess/json/SquareDeserializer.scala
new file mode 100644
index 0000000..5641a8f
--- /dev/null
+++ b/modules/core/src/main/scala/de/nowchess/chess/json/SquareDeserializer.scala
@@ -0,0 +1,9 @@
+package de.nowchess.chess.json
+
+import com.fasterxml.jackson.core.JsonParser
+import com.fasterxml.jackson.databind.{DeserializationContext, JsonDeserializer}
+import de.nowchess.api.board.Square
+
+class SquareDeserializer extends JsonDeserializer[Square]:
+  override def deserialize(p: JsonParser, ctx: DeserializationContext): Square =
+    Square.fromAlgebraic(p.getText).orNull
diff --git a/modules/core/src/main/scala/de/nowchess/chess/json/SquareSerializer.scala b/modules/core/src/main/scala/de/nowchess/chess/json/SquareSerializer.scala
new file mode 100644
index 0000000..98240ac
--- /dev/null
+++ b/modules/core/src/main/scala/de/nowchess/chess/json/SquareSerializer.scala
@@ -0,0 +1,9 @@
+package de.nowchess.chess.json
+
+import com.fasterxml.jackson.core.JsonGenerator
+import com.fasterxml.jackson.databind.{JsonSerializer, SerializerProvider}
+import de.nowchess.api.board.Square
+
+class SquareSerializer extends JsonSerializer[Square]:
+  override def serialize(value: Square, gen: JsonGenerator, provider: SerializerProvider): Unit =
+    gen.writeString(value.toString)
diff --git a/modules/core/src/main/scala/de/nowchess/chess/resource/GameResource.scala b/modules/core/src/main/scala/de/nowchess/chess/resource/GameResource.scala
index e5dbf94..8ab682e 100644
--- a/modules/core/src/main/scala/de/nowchess/chess/resource/GameResource.scala
+++ b/modules/core/src/main/scala/de/nowchess/chess/resource/GameResource.scala
@@ -6,6 +6,7 @@ import de.nowchess.api.dto.*
 import de.nowchess.api.game.{DrawReason, GameContext, GameResult}
 import de.nowchess.api.move.{Move, MoveType, PromotionPiece}
 import de.nowchess.api.player.{PlayerId, PlayerInfo}
+import de.nowchess.chess.adapter.RuleSetRestAdapter
 import de.nowchess.chess.client.IoServiceClient
 import de.nowchess.chess.controller.Parser
 import de.nowchess.chess.engine.GameEngine
@@ -36,6 +37,9 @@ class GameResource:
   @Inject
   @RestClient
   var ioClient: IoServiceClient = uninitialized
+
+  @Inject
+  var ruleSetAdapter: RuleSetRestAdapter = uninitialized
   // scalafix:on DisableSyntax.var
 
   private val DefaultWhite = PlayerInfo(PlayerId("p1"), "Player 1")
@@ -103,7 +107,7 @@ class GameResource:
     dto.fold(default)(d => PlayerInfo(PlayerId(d.id), d.displayName))
 
   private def newEntry(ctx: GameContext, white: PlayerInfo, black: PlayerInfo): GameEntry =
-    GameEntry(registry.generateId(), GameEngine(initialContext = ctx), white, black)
+    GameEntry(registry.generateId(), GameEngine(initialContext = ctx, ruleSet = ruleSetAdapter), white, black)
 
   private def applyMoveInput(engine: GameEngine, uci: String): Option[String] =
     val error = new AtomicReference[Option[String]](None)
@@ -138,6 +142,7 @@ class GameResource:
     val black = playerInfoFrom(req.black, DefaultBlack)
     val entry = newEntry(GameContext.initial, white, black)
     registry.store(entry)
+    println(s"Created game ${entry.gameId}")
     created(toGameFullDto(entry))
 
   @GET
diff --git a/modules/core/src/test/scala/de/nowchess/chess/adapter/RuleSetRestAdapterTest.scala b/modules/core/src/test/scala/de/nowchess/chess/adapter/RuleSetRestAdapterTest.scala
new file mode 100644
index 0000000..27147e2
--- /dev/null
+++ b/modules/core/src/test/scala/de/nowchess/chess/adapter/RuleSetRestAdapterTest.scala
@@ -0,0 +1,109 @@
+package de.nowchess.chess.adapter
+
+import de.nowchess.api.board.{File, Rank, Square}
+import de.nowchess.api.game.GameContext
+import de.nowchess.api.move.{Move, MoveType}
+import de.nowchess.chess.client.{RuleMoveRequest, RuleServiceClient, RuleSquareRequest}
+import io.quarkus.test.InjectMock
+import io.quarkus.test.junit.QuarkusTest
+import jakarta.inject.Inject
+import org.eclipse.microprofile.rest.client.inject.RestClient
+import org.junit.jupiter.api.{BeforeEach, DisplayName, Test}
+import org.junit.jupiter.api.Assertions.*
+import org.mockito.Mockito.{verify, when}
+
+import scala.compiletime.uninitialized
+
+// scalafix:off
+@QuarkusTest
+@DisplayName("RuleSetRestAdapter")
+class RuleSetRestAdapterTest:
+
+  @Inject
+  var adapter: RuleSetRestAdapter = uninitialized
+
+  @InjectMock
+  @RestClient
+  var client: RuleServiceClient = uninitialized
+
+  private val ctx  = GameContext.initial
+  private val sq   = Square(File.E, Rank.R2)
+  private val move = Move(Square(File.E, Rank.R2), Square(File.E, Rank.R4), MoveType.Normal(false))
+
+  @BeforeEach
+  def setup(): Unit =
+    when(client.candidateMoves(RuleSquareRequest(ctx, sq.toString))).thenReturn(List(move))
+    when(client.legalMoves(RuleSquareRequest(ctx, sq.toString))).thenReturn(List(move))
+    when(client.allLegalMoves(ctx)).thenReturn(List(move))
+    when(client.isCheck(ctx)).thenReturn(false)
+    when(client.isCheckmate(ctx)).thenReturn(false)
+    when(client.isStalemate(ctx)).thenReturn(false)
+    when(client.isInsufficientMaterial(ctx)).thenReturn(false)
+    when(client.isFiftyMoveRule(ctx)).thenReturn(false)
+    when(client.isThreefoldRepetition(ctx)).thenReturn(false)
+    when(client.applyMove(RuleMoveRequest(ctx, move))).thenReturn(ctx)
+
+  @Test
+  @DisplayName("candidateMoves delegates to client")
+  def testCandidateMoves(): Unit =
+    val result = adapter.candidateMoves(ctx)(sq)
+    assertEquals(List(move), result)
+    verify(client).candidateMoves(RuleSquareRequest(ctx, sq.toString))
+
+  @Test
+  @DisplayName("legalMoves delegates to client")
+  def testLegalMoves(): Unit =
+    val result = adapter.legalMoves(ctx)(sq)
+    assertEquals(List(move), result)
+    verify(client).legalMoves(RuleSquareRequest(ctx, sq.toString))
+
+  @Test
+  @DisplayName("allLegalMoves delegates to client")
+  def testAllLegalMoves(): Unit =
+    val result = adapter.allLegalMoves(ctx)
+    assertEquals(List(move), result)
+    verify(client).allLegalMoves(ctx)
+
+  @Test
+  @DisplayName("isCheck delegates to client")
+  def testIsCheck(): Unit =
+    assertFalse(adapter.isCheck(ctx))
+    verify(client).isCheck(ctx)
+
+  @Test
+  @DisplayName("isCheckmate delegates to client")
+  def testIsCheckmate(): Unit =
+    assertFalse(adapter.isCheckmate(ctx))
+    verify(client).isCheckmate(ctx)
+
+  @Test
+  @DisplayName("isStalemate delegates to client")
+  def testIsStalemate(): Unit =
+    assertFalse(adapter.isStalemate(ctx))
+    verify(client).isStalemate(ctx)
+
+  @Test
+  @DisplayName("isInsufficientMaterial delegates to client")
+  def testIsInsufficientMaterial(): Unit =
+    assertFalse(adapter.isInsufficientMaterial(ctx))
+    verify(client).isInsufficientMaterial(ctx)
+
+  @Test
+  @DisplayName("isFiftyMoveRule delegates to client")
+  def testIsFiftyMoveRule(): Unit =
+    assertFalse(adapter.isFiftyMoveRule(ctx))
+    verify(client).isFiftyMoveRule(ctx)
+
+  @Test
+  @DisplayName("isThreefoldRepetition delegates to client")
+  def testIsThreefoldRepetition(): Unit =
+    assertFalse(adapter.isThreefoldRepetition(ctx))
+    verify(client).isThreefoldRepetition(ctx)
+
+  @Test
+  @DisplayName("applyMove delegates to client")
+  def testApplyMove(): Unit =
+    val result = adapter.applyMove(ctx)(move)
+    assertEquals(ctx, result)
+    verify(client).applyMove(RuleMoveRequest(ctx, move))
+// scalafix:on
diff --git a/modules/core/src/test/scala/de/nowchess/chess/engine/EngineTestHelpers.scala b/modules/core/src/test/scala/de/nowchess/chess/engine/EngineTestHelpers.scala
index 3a32668..7c49e73 100644
--- a/modules/core/src/test/scala/de/nowchess/chess/engine/EngineTestHelpers.scala
+++ b/modules/core/src/test/scala/de/nowchess/chess/engine/EngineTestHelpers.scala
@@ -13,7 +13,7 @@ object EngineTestHelpers:
     new GameEngine(ruleSet = DefaultRules)
 
   def makeEngineWithBoard(board: Board, turn: Color = Color.White): GameEngine =
-    GameEngine(initialContext = GameContext.initial.withBoard(board).withTurn(turn))
+    GameEngine(initialContext = GameContext.initial.withBoard(board).withTurn(turn), ruleSet = DefaultRules)
 
   def loadFen(engine: GameEngine, fen: String): Unit =
     engine.loadGame(FenParser, fen)
diff --git a/modules/core/src/test/scala/de/nowchess/chess/engine/GameEngineDrawOfferTest.scala b/modules/core/src/test/scala/de/nowchess/chess/engine/GameEngineDrawOfferTest.scala
index 03b39a6..872ce56 100644
--- a/modules/core/src/test/scala/de/nowchess/chess/engine/GameEngineDrawOfferTest.scala
+++ b/modules/core/src/test/scala/de/nowchess/chess/engine/GameEngineDrawOfferTest.scala
@@ -1,5 +1,6 @@
 package de.nowchess.chess.engine
 
+import de.nowchess.rules.sets.DefaultRules
 import scala.collection.mutable
 import de.nowchess.api.board.Color
 import de.nowchess.api.game.{DrawReason, GameResult}
@@ -18,7 +19,7 @@ import org.scalatest.matchers.should.Matchers
 class GameEngineDrawOfferTest extends AnyFunSuite with Matchers:
 
   test("White offers draw"):
-    val engine   = new GameEngine()
+    val engine   = new GameEngine(ruleSet = DefaultRules)
     val observer = new DrawOfferMockObserver()
     engine.subscribe(observer)
 
@@ -32,7 +33,7 @@ class GameEngineDrawOfferTest extends AnyFunSuite with Matchers:
         fail(s"Expected DrawOfferEvent, but got $other")
 
   test("Black accepts White's draw offer"):
-    val engine   = new GameEngine()
+    val engine   = new GameEngine(ruleSet = DefaultRules)
     val observer = new DrawOfferMockObserver()
     engine.subscribe(observer)
 
@@ -49,7 +50,7 @@ class GameEngineDrawOfferTest extends AnyFunSuite with Matchers:
         fail(s"Expected DrawEvent, but got $other")
 
   test("Black declines White's draw offer"):
-    val engine   = new GameEngine()
+    val engine   = new GameEngine(ruleSet = DefaultRules)
     val observer = new DrawOfferMockObserver()
     engine.subscribe(observer)
 
@@ -65,7 +66,7 @@ class GameEngineDrawOfferTest extends AnyFunSuite with Matchers:
         fail(s"Expected DrawOfferDeclinedEvent, but got $other")
 
   test("Black offers draw"):
-    val engine   = new GameEngine()
+    val engine   = new GameEngine(ruleSet = DefaultRules)
     val observer = new DrawOfferMockObserver()
     engine.subscribe(observer)
 
@@ -79,7 +80,7 @@ class GameEngineDrawOfferTest extends AnyFunSuite with Matchers:
         fail(s"Expected DrawOfferEvent, but got $other")
 
   test("White accepts Black's draw offer"):
-    val engine   = new GameEngine()
+    val engine   = new GameEngine(ruleSet = DefaultRules)
     val observer = new DrawOfferMockObserver()
     engine.subscribe(observer)
 
@@ -96,7 +97,7 @@ class GameEngineDrawOfferTest extends AnyFunSuite with Matchers:
         fail(s"Expected DrawEvent, but got $other")
 
   test("Cannot accept draw when no offer pending"):
-    val engine   = new GameEngine()
+    val engine   = new GameEngine(ruleSet = DefaultRules)
     val observer = new DrawOfferMockObserver()
     engine.subscribe(observer)
 
@@ -110,7 +111,7 @@ class GameEngineDrawOfferTest extends AnyFunSuite with Matchers:
         fail(s"Expected InvalidMoveEvent, but got $other")
 
   test("Cannot decline draw when no offer pending"):
-    val engine   = new GameEngine()
+    val engine   = new GameEngine(ruleSet = DefaultRules)
     val observer = new DrawOfferMockObserver()
     engine.subscribe(observer)
 
@@ -124,7 +125,7 @@ class GameEngineDrawOfferTest extends AnyFunSuite with Matchers:
         fail(s"Expected InvalidMoveEvent, but got $other")
 
   test("Cannot offer draw when game is already over"):
-    val engine   = new GameEngine()
+    val engine   = new GameEngine(ruleSet = DefaultRules)
     val observer = new DrawOfferMockObserver()
     engine.subscribe(observer)
 
@@ -147,7 +148,7 @@ class GameEngineDrawOfferTest extends AnyFunSuite with Matchers:
         fail(s"Expected InvalidMoveEvent, but got $other")
 
   test("Cannot accept your own draw offer"):
-    val engine   = new GameEngine()
+    val engine   = new GameEngine(ruleSet = DefaultRules)
     val observer = new DrawOfferMockObserver()
     engine.subscribe(observer)
 
@@ -163,7 +164,7 @@ class GameEngineDrawOfferTest extends AnyFunSuite with Matchers:
         fail(s"Expected InvalidMoveEvent, but got $other")
 
   test("Cannot decline your own draw offer"):
-    val engine   = new GameEngine()
+    val engine   = new GameEngine(ruleSet = DefaultRules)
     val observer = new DrawOfferMockObserver()
     engine.subscribe(observer)
 
@@ -179,7 +180,7 @@ class GameEngineDrawOfferTest extends AnyFunSuite with Matchers:
         fail(s"Expected InvalidMoveEvent, but got $other")
 
   test("Cannot make second draw offer when one is already pending"):
-    val engine   = new GameEngine()
+    val engine   = new GameEngine(ruleSet = DefaultRules)
     val observer = new DrawOfferMockObserver()
     engine.subscribe(observer)
 
@@ -195,7 +196,7 @@ class GameEngineDrawOfferTest extends AnyFunSuite with Matchers:
         fail(s"Expected InvalidMoveEvent, but got $other")
 
   test("Draw offer is cleared when game ends by resignation (accept)"):
-    val engine   = new GameEngine()
+    val engine   = new GameEngine(ruleSet = DefaultRules)
     val observer = new DrawOfferMockObserver()
     engine.subscribe(observer)
 
@@ -215,7 +216,7 @@ class GameEngineDrawOfferTest extends AnyFunSuite with Matchers:
         fail(s"Expected InvalidMoveEvent, but got $other")
 
   test("Draw offer is cleared when game ends by resignation (decline)"):
-    val engine   = new GameEngine()
+    val engine   = new GameEngine(ruleSet = DefaultRules)
     val observer = new DrawOfferMockObserver()
     engine.subscribe(observer)
 
@@ -235,22 +236,22 @@ class GameEngineDrawOfferTest extends AnyFunSuite with Matchers:
         fail(s"Expected InvalidMoveEvent, but got $other")
 
   test("pendingDrawOfferBy returns None initially"):
-    val engine = new GameEngine()
+    val engine = new GameEngine(ruleSet = DefaultRules)
     engine.pendingDrawOfferBy shouldBe None
 
   test("pendingDrawOfferBy returns White after White offers"):
-    val engine = new GameEngine()
+    val engine = new GameEngine(ruleSet = DefaultRules)
     engine.offerDraw(Color.White)
     engine.pendingDrawOfferBy shouldBe Some(Color.White)
 
   test("pendingDrawOfferBy returns None after draw is accepted"):
-    val engine = new GameEngine()
+    val engine = new GameEngine(ruleSet = DefaultRules)
     engine.offerDraw(Color.White)
     engine.acceptDraw(Color.Black)
     engine.pendingDrawOfferBy shouldBe None
 
   test("applyDraw sets draw result when game not over"):
-    val engine   = new GameEngine()
+    val engine   = new GameEngine(ruleSet = DefaultRules)
     val observer = new DrawOfferMockObserver()
     engine.subscribe(observer)
     engine.applyDraw(DrawReason.Agreement)
@@ -263,7 +264,7 @@ class GameEngineDrawOfferTest extends AnyFunSuite with Matchers:
         fail(s"Expected DrawEvent, but got $other")
 
   test("applyDraw does nothing when game already over"):
-    val engine   = new GameEngine()
+    val engine   = new GameEngine(ruleSet = DefaultRules)
     val observer = new DrawOfferMockObserver()
     engine.subscribe(observer)
     // End the game with checkmate
@@ -276,7 +277,7 @@ class GameEngineDrawOfferTest extends AnyFunSuite with Matchers:
     observer.events should have length 0
 
   test("claimDraw with fifty-move rule when at half-move 100"):
-    val engine   = new GameEngine()
+    val engine   = new GameEngine(ruleSet = DefaultRules)
     val observer = new DrawOfferMockObserver()
     engine.subscribe(observer)
     // Play moves to reach fifty-move rule claim
@@ -288,7 +289,7 @@ class GameEngineDrawOfferTest extends AnyFunSuite with Matchers:
     // This is hard to do naturally; skip for now if not critical
 
   test("claimDraw when game already over"):
-    val engine   = new GameEngine()
+    val engine   = new GameEngine(ruleSet = DefaultRules)
     val observer = new DrawOfferMockObserver()
     engine.subscribe(observer)
     // End the game with checkmate
diff --git a/modules/core/src/test/scala/de/nowchess/chess/engine/GameEngineGameEndingTest.scala b/modules/core/src/test/scala/de/nowchess/chess/engine/GameEngineGameEndingTest.scala
index 9e491e8..4bb9207 100644
--- a/modules/core/src/test/scala/de/nowchess/chess/engine/GameEngineGameEndingTest.scala
+++ b/modules/core/src/test/scala/de/nowchess/chess/engine/GameEngineGameEndingTest.scala
@@ -1,5 +1,6 @@
 package de.nowchess.chess.engine
 
+import de.nowchess.rules.sets.DefaultRules
 import scala.collection.mutable
 import de.nowchess.api.board.Color
 import de.nowchess.api.game.DrawReason
@@ -11,7 +12,7 @@ import org.scalatest.matchers.should.Matchers
 class GameEngineGameEndingTest extends AnyFunSuite with Matchers:
 
   test("GameEngine handles Checkmate (Fool's Mate)"):
-    val engine   = new GameEngine()
+    val engine   = new GameEngine(ruleSet = DefaultRules)
     val observer = new EndingMockObserver()
     engine.subscribe(observer)
 
@@ -31,7 +32,7 @@ class GameEngineGameEndingTest extends AnyFunSuite with Matchers:
         fail(s"Expected CheckmateEvent, but got $other")
 
   test("GameEngine handles check detection"):
-    val engine   = new GameEngine()
+    val engine   = new GameEngine(ruleSet = DefaultRules)
     val observer = new EndingMockObserver()
     engine.subscribe(observer)
 
@@ -53,7 +54,7 @@ class GameEngineGameEndingTest extends AnyFunSuite with Matchers:
   // Wait, let's just use Sam Loyd's 10-move stalemate:
   // 1. e3 a5 2. Qh5 Ra6 3. Qxa5 h5 4. h4 Rah6 5. Qxc7 f6 6. Qxd7+ Kf7 7. Qxb7 Qd3 8. Qxb8 Qh7 9. Qxc8 Kg6 10. Qe6
   test("GameEngine handles Stalemate via 10-move known sequence"):
-    val engine   = new GameEngine()
+    val engine   = new GameEngine(ruleSet = DefaultRules)
     val observer = new EndingMockObserver()
     engine.subscribe(observer)
 
diff --git a/modules/core/src/test/scala/de/nowchess/chess/engine/GameEngineIntegrationTest.scala b/modules/core/src/test/scala/de/nowchess/chess/engine/GameEngineIntegrationTest.scala
index e07336b..5411007 100644
--- a/modules/core/src/test/scala/de/nowchess/chess/engine/GameEngineIntegrationTest.scala
+++ b/modules/core/src/test/scala/de/nowchess/chess/engine/GameEngineIntegrationTest.scala
@@ -5,7 +5,7 @@ import de.nowchess.api.game.GameContext
 import de.nowchess.api.move.{Move, MoveType, PromotionPiece}
 import de.nowchess.chess.observer.{GameEvent, InvalidMoveEvent, InvalidMoveReason, MoveRedoneEvent, Observer}
 import de.nowchess.api.io.GameContextImport
-import de.nowchess.rules.RuleSet
+import de.nowchess.api.rules.RuleSet
 import de.nowchess.rules.sets.DefaultRules
 import org.scalatest.funsuite.AnyFunSuite
 import org.scalatest.matchers.should.Matchers
@@ -21,7 +21,7 @@ class GameEngineIntegrationTest extends AnyFunSuite with Matchers:
     events
 
   test("accessors expose redo availability and command history"):
-    val engine = new GameEngine()
+    val engine = new GameEngine(ruleSet = DefaultRules)
 
     engine.canRedo shouldBe false
     engine.commandHistory shouldBe empty
@@ -30,7 +30,7 @@ class GameEngineIntegrationTest extends AnyFunSuite with Matchers:
     engine.commandHistory.nonEmpty shouldBe true
 
   test("processUserInput handles undo redo empty and malformed commands"):
-    val engine = new GameEngine()
+    val engine = new GameEngine(ruleSet = DefaultRules)
     val events = captureEvents(engine)
 
     engine.processUserInput("")
@@ -44,7 +44,7 @@ class GameEngineIntegrationTest extends AnyFunSuite with Matchers:
     } should be >= 3
 
   test("processUserInput emits Illegal move for syntactically valid but illegal target"):
-    val engine = new GameEngine()
+    val engine = new GameEngine(ruleSet = DefaultRules)
     val events = captureEvents(engine)
 
     engine.processUserInput("e2e5")
@@ -56,14 +56,14 @@ class GameEngineIntegrationTest extends AnyFunSuite with Matchers:
 
   test("loadGame returns Left when importer fails"):
 
-    val engine = new GameEngine()
+    val engine = new GameEngine(ruleSet = DefaultRules)
     val failingImporter = new GameContextImport:
       def importGameContext(input: String): Either[String, GameContext] = Left("boom")
 
     engine.loadGame(failingImporter, "ignored") shouldBe Left("boom")
 
   test("loadPosition replaces context clears history and notifies reset"):
-    val engine = new GameEngine()
+    val engine = new GameEngine(ruleSet = DefaultRules)
     val events = captureEvents(engine)
 
     engine.processUserInput("e2e4")
@@ -78,7 +78,7 @@ class GameEngineIntegrationTest extends AnyFunSuite with Matchers:
     } shouldBe true
 
   test("redo event includes captured piece description when replaying a capture"):
-    val engine = new GameEngine()
+    val engine = new GameEngine(ruleSet = DefaultRules)
     val events = captureEvents(engine)
 
     EngineTestHelpers.loadFen(engine, "4k3/8/8/8/8/8/4K3/R6r w - - 0 1")
@@ -145,13 +145,13 @@ class GameEngineIntegrationTest extends AnyFunSuite with Matchers:
 
   test("loadGame replay executes non-promotion moves through default replay branch"):
     val normalMove = Move(sq("e2"), sq("e4"), MoveType.Normal())
-    val engine     = new GameEngine()
+    val engine     = new GameEngine(ruleSet = DefaultRules)
 
     engine.replayMoves(List(normalMove), engine.context) shouldBe Right(())
     engine.context.moves.lastOption shouldBe Some(normalMove)
 
   test("replayMoves skips later moves after the first move triggers an error"):
-    val engine           = new GameEngine()
+    val engine           = new GameEngine(ruleSet = DefaultRules)
     val saved            = engine.context
     val illegalPromotion = Move(sq("e2"), sq("e1"), MoveType.Promotion(PromotionPiece.Queen))
     val trailingMove     = Move(sq("e2"), sq("e4"))
@@ -160,19 +160,19 @@ class GameEngineIntegrationTest extends AnyFunSuite with Matchers:
     engine.context shouldBe saved
 
   test("normalMoveNotation handles missing source piece"):
-    val engine = new GameEngine()
+    val engine = new GameEngine(ruleSet = DefaultRules)
     val result = engine.normalMoveNotation(Move(sq("e3"), sq("e4")), Board.initial, isCapture = false)
 
     result shouldBe "e4"
 
   test("pieceNotation default branch returns empty string"):
-    val engine = new GameEngine()
+    val engine = new GameEngine(ruleSet = DefaultRules)
     val result = engine.pieceNotation(PieceType.Pawn)
 
     result shouldBe ""
 
   test("observerCount reflects subscribe and unsubscribe operations"):
-    val engine = new GameEngine()
+    val engine = new GameEngine(ruleSet = DefaultRules)
     val observer = new Observer:
       def onGameEvent(event: GameEvent): Unit = ()
 
diff --git a/modules/core/src/test/scala/de/nowchess/chess/engine/GameEngineLoadGameTest.scala b/modules/core/src/test/scala/de/nowchess/chess/engine/GameEngineLoadGameTest.scala
index 91ac2b1..42c45df 100644
--- a/modules/core/src/test/scala/de/nowchess/chess/engine/GameEngineLoadGameTest.scala
+++ b/modules/core/src/test/scala/de/nowchess/chess/engine/GameEngineLoadGameTest.scala
@@ -1,5 +1,11 @@
 package de.nowchess.chess.engine
 
+import de.nowchess.rules.sets.DefaultRules
+import scala.collection.mutable
+import de.nowchess.api.board.{Board, Color}
+import de.nowchess.api.game.GameContext
+import de.nowchess.chess.observer.{GameEvent, Observer, PgnLoadedEvent}
+import de.nowchess.io.pgn.PgnParser
 import de.nowchess.chess.observer.{GameEvent, Observer}
 import de.nowchess.io.fen.FenParser
 import de.nowchess.io.pgn.{PgnExporter, PgnParser}
@@ -11,7 +17,7 @@ import scala.collection.mutable
 class GameEngineLoadGameTest extends AnyFunSuite with Matchers:
 
   test("loadGame with PgnParser: loads valid PGN and enables undo/redo"):
-    val engine = new GameEngine()
+    val engine = new GameEngine(ruleSet = DefaultRules)
     val pgn    = "[Event \"Test\"]\n\n1. e4 e5\n"
     val result = engine.loadGame(PgnParser, pgn)
     result shouldBe Right(())
@@ -19,7 +25,7 @@ class GameEngineLoadGameTest extends AnyFunSuite with Matchers:
     engine.canUndo shouldBe true
 
   test("loadGame with FenParser: loads position without replaying moves"):
-    val engine = new GameEngine()
+    val engine = new GameEngine(ruleSet = DefaultRules)
     val fen    = "8/4P3/4k3/8/8/8/8/8 w - - 0 1"
     val result = engine.loadGame(FenParser, fen)
     result shouldBe Right(())
@@ -27,7 +33,7 @@ class GameEngineLoadGameTest extends AnyFunSuite with Matchers:
     engine.canUndo shouldBe false
 
   test("exportGame with PgnExporter: exports current game as PGN"):
-    val engine = new GameEngine()
+    val engine = new GameEngine(ruleSet = DefaultRules)
     engine.processUserInput("e2e4")
     engine.processUserInput("e7e5")
     val pgn = engine.exportGame(PgnExporter)
diff --git a/modules/core/src/test/scala/de/nowchess/chess/engine/GameEngineNotationTest.scala b/modules/core/src/test/scala/de/nowchess/chess/engine/GameEngineNotationTest.scala
index e1c1877..6482b35 100644
--- a/modules/core/src/test/scala/de/nowchess/chess/engine/GameEngineNotationTest.scala
+++ b/modules/core/src/test/scala/de/nowchess/chess/engine/GameEngineNotationTest.scala
@@ -1,6 +1,7 @@
 package de.nowchess.chess.engine
 
 import de.nowchess.api.board.{Board, Color, File, Rank, Square}
+import de.nowchess.rules.sets.DefaultRules
 import de.nowchess.api.game.GameContext
 import de.nowchess.io.fen.FenParser
 import de.nowchess.chess.observer.*
@@ -37,7 +38,7 @@ class GameEngineNotationTest extends AnyFunSuite with Matchers:
       .withTurn(Color.White)
       .withCastlingRights(castlingRights)
 
-    val engine = new GameEngine(ctx)
+    val engine = new GameEngine(ctx, DefaultRules)
     val events = captureEvents(engine)
 
     // White castles queenside: e1c1
@@ -65,7 +66,7 @@ class GameEngineNotationTest extends AnyFunSuite with Matchers:
       .withEnPassantSquare(epSquare)
       .withCastlingRights(de.nowchess.api.board.CastlingRights(false, false, false, false))
 
-    val engine = new GameEngine(ctx)
+    val engine = new GameEngine(ctx, DefaultRules)
     val events = captureEvents(engine)
 
     // White pawn on e5 captures en passant to d6
@@ -96,7 +97,7 @@ class GameEngineNotationTest extends AnyFunSuite with Matchers:
       .withTurn(Color.White)
       .withCastlingRights(de.nowchess.api.board.CastlingRights(false, false, false, false))
 
-    val engine = new GameEngine(ctx)
+    val engine = new GameEngine(ctx, DefaultRules)
     val events = captureEvents(engine)
 
     engine.processUserInput("e7e8b")
@@ -117,7 +118,7 @@ class GameEngineNotationTest extends AnyFunSuite with Matchers:
       .withTurn(Color.White)
       .withCastlingRights(de.nowchess.api.board.CastlingRights(false, false, false, false))
 
-    val engine = new GameEngine(ctx)
+    val engine = new GameEngine(ctx, DefaultRules)
     val events = captureEvents(engine)
 
     // King moves e1 -> f1
diff --git a/modules/core/src/test/scala/de/nowchess/chess/engine/GameEnginePromotionTest.scala b/modules/core/src/test/scala/de/nowchess/chess/engine/GameEnginePromotionTest.scala
index 4c86f17..edc74d7 100644
--- a/modules/core/src/test/scala/de/nowchess/chess/engine/GameEnginePromotionTest.scala
+++ b/modules/core/src/test/scala/de/nowchess/chess/engine/GameEnginePromotionTest.scala
@@ -14,7 +14,7 @@ import de.nowchess.chess.observer.{
   MoveExecutedEvent,
   Observer,
 }
-import de.nowchess.rules.RuleSet
+import de.nowchess.api.rules.RuleSet
 import de.nowchess.rules.sets.DefaultRules
 import org.scalatest.funsuite.AnyFunSuite
 import org.scalatest.matchers.should.Matchers
@@ -29,7 +29,7 @@ class GameEnginePromotionTest extends AnyFunSuite with Matchers:
     events
 
   private def engineWith(board: Board, turn: Color = Color.White): GameEngine =
-    new GameEngine(initialContext = GameContext.initial.withBoard(board).withTurn(turn))
+    new GameEngine(initialContext = GameContext.initial.withBoard(board).withTurn(turn), ruleSet = DefaultRules)
 
   test("processUserInput without promotion suffix fires InvalidMoveEvent when pawn reaches back rank") {
     val promotionBoard = FenParser.parseBoard("8/4P3/4k3/8/8/8/8/8").get
diff --git a/modules/core/src/test/scala/de/nowchess/chess/engine/GameEngineResignTest.scala b/modules/core/src/test/scala/de/nowchess/chess/engine/GameEngineResignTest.scala
index cf96cdf..0ee4395 100644
--- a/modules/core/src/test/scala/de/nowchess/chess/engine/GameEngineResignTest.scala
+++ b/modules/core/src/test/scala/de/nowchess/chess/engine/GameEngineResignTest.scala
@@ -1,5 +1,6 @@
 package de.nowchess.chess.engine
 
+import de.nowchess.rules.sets.DefaultRules
 import scala.collection.mutable
 import de.nowchess.api.board.Color
 import de.nowchess.api.game.GameResult
@@ -10,7 +11,7 @@ import org.scalatest.matchers.should.Matchers
 class GameEngineResignTest extends AnyFunSuite with Matchers:
 
   test("White resigns"):
-    val engine   = new GameEngine()
+    val engine   = new GameEngine(ruleSet = DefaultRules)
     val observer = new ResignMockObserver()
     engine.subscribe(observer)
 
@@ -25,7 +26,7 @@ class GameEngineResignTest extends AnyFunSuite with Matchers:
         fail(s"Expected ResignEvent, but got $other")
 
   test("Black resigns"):
-    val engine   = new GameEngine()
+    val engine   = new GameEngine(ruleSet = DefaultRules)
     val observer = new ResignMockObserver()
     engine.subscribe(observer)
 
@@ -40,7 +41,7 @@ class GameEngineResignTest extends AnyFunSuite with Matchers:
         fail(s"Expected ResignEvent, but got $other")
 
   test("Cannot resign when game is already over"):
-    val engine   = new GameEngine()
+    val engine   = new GameEngine(ruleSet = DefaultRules)
     val observer = new ResignMockObserver()
     engine.subscribe(observer)
 
@@ -64,7 +65,7 @@ class GameEngineResignTest extends AnyFunSuite with Matchers:
         fail(s"Expected InvalidMoveEvent, but got $other")
 
   test("resign() without color resigns side to move"):
-    val engine   = new GameEngine()
+    val engine   = new GameEngine(ruleSet = DefaultRules)
     val observer = new ResignMockObserver()
     engine.subscribe(observer)
 
@@ -73,7 +74,7 @@ class GameEngineResignTest extends AnyFunSuite with Matchers:
     engine.context.result shouldBe Some(GameResult.Win(Color.Black))
 
   test("resign() without color does nothing when game already over"):
-    val engine   = new GameEngine()
+    val engine   = new GameEngine(ruleSet = DefaultRules)
     val observer = new ResignMockObserver()
     engine.subscribe(observer)
 
diff --git a/modules/core/src/test/scala/de/nowchess/chess/json/JsonSerializersTest.scala b/modules/core/src/test/scala/de/nowchess/chess/json/JsonSerializersTest.scala
new file mode 100644
index 0000000..a834aa1
--- /dev/null
+++ b/modules/core/src/test/scala/de/nowchess/chess/json/JsonSerializersTest.scala
@@ -0,0 +1,87 @@
+package de.nowchess.chess.json
+
+import com.fasterxml.jackson.databind.ObjectMapper
+import com.fasterxml.jackson.databind.module.SimpleModule
+import com.fasterxml.jackson.module.scala.DefaultScalaModule
+import de.nowchess.api.board.{File, Rank, Square}
+import de.nowchess.api.move.{MoveType, PromotionPiece}
+import org.scalatest.funsuite.AnyFunSuite
+import org.scalatest.matchers.should.Matchers
+
+class JsonSerializersTest extends AnyFunSuite with Matchers:
+
+  private val mapper: ObjectMapper =
+    val m   = new ObjectMapper()
+    val mod = new SimpleModule()
+    m.registerModule(DefaultScalaModule)
+    mod.addSerializer(classOf[Square], new SquareSerializer())
+    mod.addDeserializer(classOf[Square], new SquareDeserializer())
+    mod.addSerializer(classOf[MoveType], new MoveTypeSerializer())
+    mod.addDeserializer(classOf[MoveType], new MoveTypeDeserializer())
+    m.registerModule(mod)
+    m
+
+  private val e4 = Square(File.E, Rank.R4)
+
+  // ── SquareSerializer ──────────────────────────────────────────────
+
+  test("SquareSerializer writes square as string"):
+    mapper.writeValueAsString(e4) shouldBe """"e4""""
+
+  // ── SquareDeserializer ────────────────────────────────────────────
+
+  test("SquareDeserializer reads valid square string"):
+    mapper.readValue(""""e4"""", classOf[Square]) shouldBe e4
+
+  // scalafix:off DisableSyntax.null
+  test("SquareDeserializer returns null for invalid square string"):
+    mapper.readValue(""""z9"""", classOf[Square]) shouldBe null
+  // scalafix:on DisableSyntax.null
+
+  // ── MoveTypeSerializer ────────────────────────────────────────────
+
+  test("MoveTypeSerializer serializes Normal non-capture"):
+    mapper.writeValueAsString(MoveType.Normal(false)) shouldBe """{"type":"normal","isCapture":false}"""
+
+  test("MoveTypeSerializer serializes Normal capture"):
+    mapper.writeValueAsString(MoveType.Normal(true)) shouldBe """{"type":"normal","isCapture":true}"""
+
+  test("MoveTypeSerializer serializes CastleKingside"):
+    mapper.writeValueAsString(MoveType.CastleKingside) shouldBe """{"type":"castleKingside"}"""
+
+  test("MoveTypeSerializer serializes CastleQueenside"):
+    mapper.writeValueAsString(MoveType.CastleQueenside) shouldBe """{"type":"castleQueenside"}"""
+
+  test("MoveTypeSerializer serializes EnPassant"):
+    mapper.writeValueAsString(MoveType.EnPassant) shouldBe """{"type":"enPassant"}"""
+
+  test("MoveTypeSerializer serializes Promotion"):
+    mapper.writeValueAsString(MoveType.Promotion(PromotionPiece.Queen)) shouldBe
+      """{"type":"promotion","piece":"Queen"}"""
+
+  // ── MoveTypeDeserializer ──────────────────────────────────────────
+
+  test("MoveTypeDeserializer deserializes normal non-capture"):
+    mapper.readValue("""{"type":"normal","isCapture":false}""", classOf[MoveType]) shouldBe
+      MoveType.Normal(false)
+
+  test("MoveTypeDeserializer deserializes normal capture"):
+    mapper.readValue("""{"type":"normal","isCapture":true}""", classOf[MoveType]) shouldBe
+      MoveType.Normal(true)
+
+  test("MoveTypeDeserializer deserializes castleKingside"):
+    mapper.readValue("""{"type":"castleKingside"}""", classOf[MoveType]) shouldBe MoveType.CastleKingside
+
+  test("MoveTypeDeserializer deserializes castleQueenside"):
+    mapper.readValue("""{"type":"castleQueenside"}""", classOf[MoveType]) shouldBe MoveType.CastleQueenside
+
+  test("MoveTypeDeserializer deserializes enPassant"):
+    mapper.readValue("""{"type":"enPassant"}""", classOf[MoveType]) shouldBe MoveType.EnPassant
+
+  test("MoveTypeDeserializer deserializes promotion"):
+    mapper.readValue("""{"type":"promotion","piece":"Rook"}""", classOf[MoveType]) shouldBe
+      MoveType.Promotion(PromotionPiece.Rook)
+
+  test("MoveTypeDeserializer throws for unknown type"):
+    an[Exception] should be thrownBy
+      mapper.readValue("""{"type":"unknown"}""", classOf[MoveType])
diff --git a/modules/core/src/test/scala/de/nowchess/chess/registry/GameRegistryImplTest.scala b/modules/core/src/test/scala/de/nowchess/chess/registry/GameRegistryImplTest.scala
index 6bea0c0..53d1362 100644
--- a/modules/core/src/test/scala/de/nowchess/chess/registry/GameRegistryImplTest.scala
+++ b/modules/core/src/test/scala/de/nowchess/chess/registry/GameRegistryImplTest.scala
@@ -1,6 +1,7 @@
 package de.nowchess.chess.registry
 
 import de.nowchess.api.player.{PlayerId, PlayerInfo}
+import de.nowchess.rules.sets.DefaultRules
 import de.nowchess.chess.engine.GameEngine
 import io.quarkus.test.junit.QuarkusTest
 import jakarta.inject.Inject
@@ -20,14 +21,24 @@ class GameRegistryImplTest:
   @Test
   @DisplayName("store saves entry")
   def testStore(): Unit =
-    val entry = GameEntry("g1", GameEngine(), PlayerInfo(PlayerId("p1"), "P1"), PlayerInfo(PlayerId("p2"), "P2"))
+    val entry = GameEntry(
+      "g1",
+      GameEngine(ruleSet = DefaultRules),
+      PlayerInfo(PlayerId("p1"), "P1"),
+      PlayerInfo(PlayerId("p2"), "P2"),
+    )
     registry.store(entry)
     assertTrue(registry.get("g1").isDefined)
 
   @Test
   @DisplayName("get returns stored entry")
   def testGet(): Unit =
-    val entry = GameEntry("g2", GameEngine(), PlayerInfo(PlayerId("p1"), "P1"), PlayerInfo(PlayerId("p2"), "P2"))
+    val entry = GameEntry(
+      "g2",
+      GameEngine(ruleSet = DefaultRules),
+      PlayerInfo(PlayerId("p1"), "P1"),
+      PlayerInfo(PlayerId("p2"), "P2"),
+    )
     registry.store(entry)
     val retrieved = registry.get("g2")
     assertTrue(retrieved.isDefined)
@@ -41,7 +52,12 @@ class GameRegistryImplTest:
   @Test
   @DisplayName("update modifies existing entry")
   def testUpdate(): Unit =
-    val entry = GameEntry("g3", GameEngine(), PlayerInfo(PlayerId("p1"), "P1"), PlayerInfo(PlayerId("p2"), "P2"))
+    val entry = GameEntry(
+      "g3",
+      GameEngine(ruleSet = DefaultRules),
+      PlayerInfo(PlayerId("p1"), "P1"),
+      PlayerInfo(PlayerId("p2"), "P2"),
+    )
     registry.store(entry)
     val updated = entry.copy(resigned = true)
     registry.update(updated)
diff --git a/modules/core/src/test/scala/de/nowchess/chess/resource/GameResourceIntegrationTest.scala b/modules/core/src/test/scala/de/nowchess/chess/resource/GameResourceIntegrationTest.scala
index 1ee458e..abea233 100644
--- a/modules/core/src/test/scala/de/nowchess/chess/resource/GameResourceIntegrationTest.scala
+++ b/modules/core/src/test/scala/de/nowchess/chess/resource/GameResourceIntegrationTest.scala
@@ -1,11 +1,13 @@
 package de.nowchess.chess.resource
 
+import de.nowchess.api.board.Square
 import de.nowchess.api.dto.*
 import de.nowchess.api.game.GameContext
-import de.nowchess.chess.client.IoServiceClient
+import de.nowchess.chess.client.{IoServiceClient, RuleMoveRequest, RuleServiceClient, RuleSquareRequest}
 import de.nowchess.chess.exception.BadRequestException
 import de.nowchess.io.fen.FenExporter
 import de.nowchess.io.pgn.PgnParser
+import de.nowchess.rules.sets.DefaultRules
 import io.quarkus.test.InjectMock
 import io.quarkus.test.junit.QuarkusTest
 import jakarta.inject.Inject
@@ -14,6 +16,7 @@ import org.junit.jupiter.api.{BeforeEach, DisplayName, Test}
 import org.junit.jupiter.api.Assertions.*
 import org.mockito.ArgumentMatchers.any
 import org.mockito.Mockito.when
+import org.mockito.invocation.InvocationOnMock
 
 import scala.compiletime.uninitialized
 
@@ -29,6 +32,10 @@ class GameResourceIntegrationTest:
   @RestClient
   var ioClient: IoServiceClient = uninitialized
 
+  @InjectMock
+  @RestClient
+  var ruleClient: RuleServiceClient = uninitialized
+
   @BeforeEach
   def setupMocks(): Unit =
     when(ioClient.importFen(any())).thenReturn(GameContext.initial)
@@ -37,6 +44,32 @@ class GameResourceIntegrationTest:
     )
     when(ioClient.exportFen(any())).thenReturn(FenExporter.exportGameContext(GameContext.initial))
     when(ioClient.exportPgn(any())).thenReturn("1. e4 c5")
+    when(ruleClient.legalMoves(any())).thenAnswer((inv: InvocationOnMock) =>
+      val req = inv.getArgument[RuleSquareRequest](0)
+      DefaultRules.legalMoves(req.context)(Square.fromAlgebraic(req.square).get),
+    )
+    when(ruleClient.allLegalMoves(any())).thenAnswer((inv: InvocationOnMock) =>
+      DefaultRules.allLegalMoves(inv.getArgument[GameContext](0)),
+    )
+    when(ruleClient.applyMove(any())).thenAnswer((inv: InvocationOnMock) =>
+      val req = inv.getArgument[RuleMoveRequest](0)
+      DefaultRules.applyMove(req.context)(req.move),
+    )
+    when(ruleClient.isCheck(any())).thenAnswer((inv: InvocationOnMock) =>
+      DefaultRules.isCheck(inv.getArgument[GameContext](0)),
+    )
+    when(ruleClient.isCheckmate(any())).thenAnswer((inv: InvocationOnMock) =>
+      DefaultRules.isCheckmate(inv.getArgument[GameContext](0)),
+    )
+    when(ruleClient.isStalemate(any())).thenAnswer((inv: InvocationOnMock) =>
+      DefaultRules.isStalemate(inv.getArgument[GameContext](0)),
+    )
+    when(ruleClient.isInsufficientMaterial(any())).thenAnswer((inv: InvocationOnMock) =>
+      DefaultRules.isInsufficientMaterial(inv.getArgument[GameContext](0)),
+    )
+    when(ruleClient.isThreefoldRepetition(any())).thenAnswer((inv: InvocationOnMock) =>
+      DefaultRules.isThreefoldRepetition(inv.getArgument[GameContext](0)),
+    )
 
   @Test
   @DisplayName("createGame returns 201")
diff --git a/modules/rule/build.gradle.kts b/modules/rule/build.gradle.kts
index 093fe12..38982d5 100644
--- a/modules/rule/build.gradle.kts
+++ b/modules/rule/build.gradle.kts
@@ -1,6 +1,7 @@
 plugins {
     id("scala")
     id("org.scoverage") version "8.1"
+    id("io.quarkus")
 }
 
 group = "de.nowchess"
@@ -25,6 +26,10 @@ tasks.withType<ScalaCompile> {
     scalaCompileOptions.additionalParameters = listOf("-encoding", "UTF-8")
 }
 
+val quarkusPlatformGroupId: String by project
+val quarkusPlatformArtifactId: String by project
+val quarkusPlatformVersion: String by project
+
 dependencies {
 
     compileOnly("org.scala-lang:scala3-compiler_3") {
@@ -40,20 +45,56 @@ dependencies {
 
     implementation(project(":modules:api"))
 
+    implementation(platform("${quarkusPlatformGroupId}:${quarkusPlatformArtifactId}:${quarkusPlatformVersion}"))
+    implementation("io.quarkus:quarkus-rest")
+    implementation("io.quarkus:quarkus-hibernate-orm")
+    implementation("io.quarkus:quarkus-rest-client-jackson")
+    implementation("io.quarkus:quarkus-rest-client")
+    implementation("io.quarkus:quarkus-rest-jackson")
+    implementation("io.quarkus:quarkus-config-yaml")
+    implementation("io.quarkus:quarkus-smallrye-fault-tolerance")
+    implementation("io.quarkus:quarkus-smallrye-jwt")
+    implementation("io.quarkus:quarkus-smallrye-health")
+    implementation("io.quarkus:quarkus-micrometer")
+    implementation("io.quarkus:quarkus-arc")
+    implementation("com.fasterxml.jackson.module:jackson-module-scala_3:${versions["JACKSON_SCALA"]!!}")
+
     testImplementation(project(":modules:io"))
     testImplementation(platform("org.junit:junit-bom:5.13.4"))
     testImplementation("org.junit.jupiter:junit-jupiter")
     testImplementation("org.scalatest:scalatest_3:${versions["SCALATEST"]!!}")
     testImplementation("co.helmethair:scalatest-junit-runner:${versions["SCALATEST_JUNIT"]!!}")
+    testImplementation("io.quarkus:quarkus-junit5")
+    testImplementation("io.rest-assured:rest-assured")
 
     testRuntimeOnly("org.junit.platform:junit-platform-launcher")
 }
 
+configurations.matching { !it.name.startsWith("scoverage") }.configureEach {
+    resolutionStrategy.force("org.scala-lang:scala-library:${versions["SCALA_LIBRARY"]!!}")
+}
+configurations.scoverage {
+    resolutionStrategy.eachDependency {
+        if (requested.group == "org.scoverage" && requested.name.startsWith("scalac-scoverage-plugin_")) {
+            useTarget("${requested.group}:scalac-scoverage-plugin_2.13.16:2.3.0")
+        }
+    }
+}
+
+tasks.withType<JavaCompile> {
+    options.encoding = "UTF-8"
+    options.compilerArgs.add("-parameters")
+}
+
+tasks.withType<Jar>().configureEach {
+    duplicatesStrategy = DuplicatesStrategy.EXCLUDE
+}
+
 tasks.test {
     useJUnitPlatform {
-        includeEngines("scalatest")
+        includeEngines("scalatest", "junit-jupiter")
         testLogging {
-            events("skipped", "failed")
+            events("passed", "skipped", "failed")
         }
     }
     finalizedBy(tasks.reportScoverage)
@@ -61,3 +102,7 @@ tasks.test {
 tasks.reportScoverage {
     dependsOn(tasks.test)
 }
+
+tasks.jar {
+    duplicatesStrategy = DuplicatesStrategy.EXCLUDE
+}
diff --git a/modules/rule/src/main/docker/Dockerfile.jvm b/modules/rule/src/main/docker/Dockerfile.jvm
new file mode 100644
index 0000000..c3c09fc
--- /dev/null
+++ b/modules/rule/src/main/docker/Dockerfile.jvm
@@ -0,0 +1,100 @@
+####
+# This Dockerfile is used in order to build a container that runs the Quarkus application in JVM mode
+#
+# Before building the container image run:
+#
+# ./gradlew build
+#
+# Then, build the image with:
+#
+# docker build -f src/main/docker/Dockerfile.jvm -t quarkus/backcore-jvm .
+#
+# Then run the container using:
+#
+# docker run -i --rm -p 8080:8080 quarkus/backcore-jvm
+#
+# If you want to include the debug port into your docker image
+# you will have to expose the debug port (default 5005 being the default) like this :  EXPOSE 8080 5005.
+# Additionally you will have to set -e JAVA_DEBUG=true and -e JAVA_DEBUG_PORT=*:5005
+# when running the container
+#
+# Then run the container using :
+#
+# docker run -i --rm -p 8080:8080 quarkus/backcore-jvm
+#
+# This image uses the `run-java.sh` script to run the application.
+# This scripts computes the command line to execute your Java application, and
+# includes memory/GC tuning.
+# You can configure the behavior using the following environment properties:
+# - JAVA_OPTS: JVM options passed to the `java` command (example: "-verbose:class") - Be aware that this will override
+# the default JVM options, use `JAVA_OPTS_APPEND` to append options
+# - JAVA_OPTS_APPEND: User specified Java options to be appended to generated options
+#   in JAVA_OPTS (example: "-Dsome.property=foo")
+# - JAVA_MAX_MEM_RATIO: Is used when no `-Xmx` option is given in JAVA_OPTS. This is
+#   used to calculate a default maximal heap memory based on a containers restriction.
+#   If used in a container without any memory constraints for the container then this
+#   option has no effect. If there is a memory constraint then `-Xmx` is set to a ratio
+#   of the container available memory as set here. The default is `50` which means 50%
+#   of the available memory is used as an upper boundary. You can skip this mechanism by
+#   setting this value to `0` in which case no `-Xmx` option is added.
+# - JAVA_INITIAL_MEM_RATIO: Is used when no `-Xms` option is given in JAVA_OPTS. This
+#   is used to calculate a default initial heap memory based on the maximum heap memory.
+#   If used in a container without any memory constraints for the container then this
+#   option has no effect. If there is a memory constraint then `-Xms` is set to a ratio
+#   of the `-Xmx` memory as set here. The default is `25` which means 25% of the `-Xmx`
+#   is used as the initial heap size. You can skip this mechanism by setting this value
+#   to `0` in which case no `-Xms` option is added (example: "25")
+# - JAVA_MAX_INITIAL_MEM: Is used when no `-Xms` option is given in JAVA_OPTS.
+#   This is used to calculate the maximum value of the initial heap memory. If used in
+#   a container without any memory constraints for the container then this option has
+#   no effect. If there is a memory constraint then `-Xms` is limited to the value set
+#   here. The default is 4096MB which means the calculated value of `-Xms` never will
+#   be greater than 4096MB. The value of this variable is expressed in MB (example: "4096")
+# - JAVA_DIAGNOSTICS: Set this to get some diagnostics information to standard output
+#   when things are happening. This option, if set to true, will set
+#  `-XX:+UnlockDiagnosticVMOptions`. Disabled by default (example: "true").
+# - JAVA_DEBUG: If set remote debugging will be switched on. Disabled by default (example:
+#    true").
+# - JAVA_DEBUG_PORT: Port used for remote debugging. Defaults to 5005 (example: "8787").
+# - CONTAINER_CORE_LIMIT: A calculated core limit as described in
+#   https://www.kernel.org/doc/Documentation/scheduler/sched-bwc.txt. (example: "2")
+# - CONTAINER_MAX_MEMORY: Memory limit given to the container (example: "1024").
+# - GC_MIN_HEAP_FREE_RATIO: Minimum percentage of heap free after GC to avoid expansion.
+#   (example: "20")
+# - GC_MAX_HEAP_FREE_RATIO: Maximum percentage of heap free after GC to avoid shrinking.
+#   (example: "40")
+# - GC_TIME_RATIO: Specifies the ratio of the time spent outside the garbage collection.
+#   (example: "4")
+# - GC_ADAPTIVE_SIZE_POLICY_WEIGHT: The weighting given to the current GC time versus
+#   previous GC times. (example: "90")
+# - GC_METASPACE_SIZE: The initial metaspace size. (example: "20")
+# - GC_MAX_METASPACE_SIZE: The maximum metaspace size. (example: "100")
+# - GC_CONTAINER_OPTIONS: Specify Java GC to use. The value of this variable should
+#   contain the necessary JRE command-line options to specify the required GC, which
+#   will override the default of `-XX:+UseParallelGC` (example: -XX:+UseG1GC).
+# - HTTPS_PROXY: The location of the https proxy. (example: "myuser@127.0.0.1:8080")
+# - HTTP_PROXY: The location of the http proxy. (example: "myuser@127.0.0.1:8080")
+# - NO_PROXY: A comma separated lists of hosts, IP addresses or domains that can be
+#   accessed directly. (example: "foo.example.com,bar.example.com")
+#
+# You can find more information about the UBI base runtime images and their configuration here:
+# https://rh-openjdk.github.io/redhat-openjdk-containers/
+###
+FROM registry.access.redhat.com/ubi9/openjdk-21-runtime:1.24
+
+ENV LANGUAGE='en_US:en'
+
+
+# We make four distinct layers so if there are application changes the library layers can be re-used
+COPY --chown=185 build/quarkus-app/lib/ /deployments/lib/
+COPY --chown=185 build/quarkus-app/*.jar /deployments/
+COPY --chown=185 build/quarkus-app/app/ /deployments/app/
+COPY --chown=185 build/quarkus-app/quarkus/ /deployments/quarkus/
+
+EXPOSE 8080
+USER 185
+ENV JAVA_OPTS_APPEND="-Dquarkus.http.host=0.0.0.0 -Djava.util.logging.manager=org.jboss.logmanager.LogManager"
+ENV JAVA_APP_JAR="/deployments/quarkus-run.jar"
+
+ENTRYPOINT [ "/opt/jboss/container/java/run/run-java.sh" ]
+
diff --git a/modules/rule/src/main/docker/Dockerfile.legacy-jar b/modules/rule/src/main/docker/Dockerfile.legacy-jar
new file mode 100644
index 0000000..8c89666
--- /dev/null
+++ b/modules/rule/src/main/docker/Dockerfile.legacy-jar
@@ -0,0 +1,96 @@
+####
+# This Dockerfile is used in order to build a container that runs the Quarkus application in JVM mode
+#
+# Before building the container image run:
+#
+# ./gradlew build -Dquarkus.package.jar.type=legacy-jar
+#
+# Then, build the image with:
+#
+# docker build -f src/main/docker/Dockerfile.legacy-jar -t quarkus/backcore-legacy-jar .
+#
+# Then run the container using:
+#
+# docker run -i --rm -p 8080:8080 quarkus/backcore-legacy-jar
+#
+# If you want to include the debug port into your docker image
+# you will have to expose the debug port (default 5005 being the default) like this :  EXPOSE 8080 5005.
+# Additionally you will have to set -e JAVA_DEBUG=true and -e JAVA_DEBUG_PORT=*:5005
+# when running the container
+#
+# Then run the container using :
+#
+# docker run -i --rm -p 8080:8080 quarkus/backcore-legacy-jar
+#
+# This image uses the `run-java.sh` script to run the application.
+# This scripts computes the command line to execute your Java application, and
+# includes memory/GC tuning.
+# You can configure the behavior using the following environment properties:
+# - JAVA_OPTS: JVM options passed to the `java` command (example: "-verbose:class") - Be aware that this will override
+# the default JVM options, use `JAVA_OPTS_APPEND` to append options
+# - JAVA_OPTS_APPEND: User specified Java options to be appended to generated options
+#   in JAVA_OPTS (example: "-Dsome.property=foo")
+# - JAVA_MAX_MEM_RATIO: Is used when no `-Xmx` option is given in JAVA_OPTS. This is
+#   used to calculate a default maximal heap memory based on a containers restriction.
+#   If used in a container without any memory constraints for the container then this
+#   option has no effect. If there is a memory constraint then `-Xmx` is set to a ratio
+#   of the container available memory as set here. The default is `50` which means 50%
+#   of the available memory is used as an upper boundary. You can skip this mechanism by
+#   setting this value to `0` in which case no `-Xmx` option is added.
+# - JAVA_INITIAL_MEM_RATIO: Is used when no `-Xms` option is given in JAVA_OPTS. This
+#   is used to calculate a default initial heap memory based on the maximum heap memory.
+#   If used in a container without any memory constraints for the container then this
+#   option has no effect. If there is a memory constraint then `-Xms` is set to a ratio
+#   of the `-Xmx` memory as set here. The default is `25` which means 25% of the `-Xmx`
+#   is used as the initial heap size. You can skip this mechanism by setting this value
+#   to `0` in which case no `-Xms` option is added (example: "25")
+# - JAVA_MAX_INITIAL_MEM: Is used when no `-Xms` option is given in JAVA_OPTS.
+#   This is used to calculate the maximum value of the initial heap memory. If used in
+#   a container without any memory constraints for the container then this option has
+#   no effect. If there is a memory constraint then `-Xms` is limited to the value set
+#   here. The default is 4096MB which means the calculated value of `-Xms` never will
+#   be greater than 4096MB. The value of this variable is expressed in MB (example: "4096")
+# - JAVA_DIAGNOSTICS: Set this to get some diagnostics information to standard output
+#   when things are happening. This option, if set to true, will set
+#  `-XX:+UnlockDiagnosticVMOptions`. Disabled by default (example: "true").
+# - JAVA_DEBUG: If set remote debugging will be switched on. Disabled by default (example:
+#    true").
+# - JAVA_DEBUG_PORT: Port used for remote debugging. Defaults to 5005 (example: "8787").
+# - CONTAINER_CORE_LIMIT: A calculated core limit as described in
+#   https://www.kernel.org/doc/Documentation/scheduler/sched-bwc.txt. (example: "2")
+# - CONTAINER_MAX_MEMORY: Memory limit given to the container (example: "1024").
+# - GC_MIN_HEAP_FREE_RATIO: Minimum percentage of heap free after GC to avoid expansion.
+#   (example: "20")
+# - GC_MAX_HEAP_FREE_RATIO: Maximum percentage of heap free after GC to avoid shrinking.
+#   (example: "40")
+# - GC_TIME_RATIO: Specifies the ratio of the time spent outside the garbage collection.
+#   (example: "4")
+# - GC_ADAPTIVE_SIZE_POLICY_WEIGHT: The weighting given to the current GC time versus
+#   previous GC times. (example: "90")
+# - GC_METASPACE_SIZE: The initial metaspace size. (example: "20")
+# - GC_MAX_METASPACE_SIZE: The maximum metaspace size. (example: "100")
+# - GC_CONTAINER_OPTIONS: Specify Java GC to use. The value of this variable should
+#   contain the necessary JRE command-line options to specify the required GC, which
+#   will override the default of `-XX:+UseParallelGC` (example: -XX:+UseG1GC).
+# - HTTPS_PROXY: The location of the https proxy. (example: "myuser@127.0.0.1:8080")
+# - HTTP_PROXY: The location of the http proxy. (example: "myuser@127.0.0.1:8080")
+# - NO_PROXY: A comma separated lists of hosts, IP addresses or domains that can be
+#   accessed directly. (example: "foo.example.com,bar.example.com")
+#
+# You can find more information about the UBI base runtime images and their configuration here:
+# https://rh-openjdk.github.io/redhat-openjdk-containers/
+###
+FROM registry.access.redhat.com/ubi9/openjdk-21-runtime:1.24
+
+ENV LANGUAGE='en_US:en'
+
+
+COPY build/lib/* /deployments/lib/
+COPY build/*-runner.jar /deployments/quarkus-run.jar
+
+EXPOSE 8080
+USER 185
+ENV JAVA_OPTS_APPEND="-Dquarkus.http.host=0.0.0.0 -Djava.util.logging.manager=org.jboss.logmanager.LogManager"
+ENV JAVA_APP_JAR="/deployments/quarkus-run.jar"
+
+ENTRYPOINT [ "/opt/jboss/container/java/run/run-java.sh" ]
diff --git a/modules/rule/src/main/docker/Dockerfile.native b/modules/rule/src/main/docker/Dockerfile.native
new file mode 100644
index 0000000..57defbf
--- /dev/null
+++ b/modules/rule/src/main/docker/Dockerfile.native
@@ -0,0 +1,29 @@
+####
+# This Dockerfile is used in order to build a container that runs the Quarkus application in native (no JVM) mode.
+#
+# Before building the container image run:
+#
+# ./gradlew build -Dquarkus.native.enabled=true
+#
+# Then, build the image with:
+#
+# docker build -f src/main/docker/Dockerfile.native -t quarkus/backcore .
+#
+# Then run the container using:
+#
+# docker run -i --rm -p 8080:8080 quarkus/backcore
+#
+# The ` registry.access.redhat.com/ubi9/ubi-minimal:9.7` base image is based on UBI 9.
+# To use UBI 8, switch to `quay.io/ubi8/ubi-minimal:8.10`.
+###
+FROM registry.access.redhat.com/ubi9/ubi-minimal:9.7
+WORKDIR /work/
+RUN chown 1001 /work \
+    && chmod "g+rwX" /work \
+    && chown 1001:root /work
+COPY --chown=1001:root --chmod=0755 build/*-runner /work/application
+
+EXPOSE 8080
+USER 1001
+
+ENTRYPOINT ["./application", "-Dquarkus.http.host=0.0.0.0"]
diff --git a/modules/rule/src/main/docker/Dockerfile.native-micro b/modules/rule/src/main/docker/Dockerfile.native-micro
new file mode 100644
index 0000000..9408243
--- /dev/null
+++ b/modules/rule/src/main/docker/Dockerfile.native-micro
@@ -0,0 +1,32 @@
+####
+# This Dockerfile is used in order to build a container that runs the Quarkus application in native (no JVM) mode.
+# It uses a micro base image, tuned for Quarkus native executables.
+# It reduces the size of the resulting container image.
+# Check https://quarkus.io/guides/quarkus-runtime-base-image for further information about this image.
+#
+# Before building the container image run:
+#
+# ./gradlew build -Dquarkus.native.enabled=true
+#
+# Then, build the image with:
+#
+# docker build -f src/main/docker/Dockerfile.native-micro -t quarkus/backcore .
+#
+# Then run the container using:
+#
+# docker run -i --rm -p 8080:8080 quarkus/backcore
+#
+# The `quay.io/quarkus/ubi9-quarkus-micro-image:2.0` base image is based on UBI 9.
+# To use UBI 8, switch to `quay.io/quarkus/quarkus-micro-image:2.0`.
+###
+FROM quay.io/quarkus/ubi9-quarkus-micro-image:2.0
+WORKDIR /work/
+RUN chown 1001 /work \
+    && chmod "g+rwX" /work \
+    && chown 1001:root /work
+COPY --chown=1001:root --chmod=0755 build/*-runner /work/application
+
+EXPOSE 8080
+USER 1001
+
+ENTRYPOINT ["./application", "-Dquarkus.http.host=0.0.0.0"]
diff --git a/modules/rule/src/main/resources/application.yml b/modules/rule/src/main/resources/application.yml
new file mode 100644
index 0000000..98b81ce
--- /dev/null
+++ b/modules/rule/src/main/resources/application.yml
@@ -0,0 +1,5 @@
+quarkus:
+  http:
+    port: 8082
+  application:
+    name: rule-service
diff --git a/modules/rule/src/main/scala/de/nowchess/rules/config/JacksonConfig.scala b/modules/rule/src/main/scala/de/nowchess/rules/config/JacksonConfig.scala
new file mode 100644
index 0000000..8dd29b8
--- /dev/null
+++ b/modules/rule/src/main/scala/de/nowchess/rules/config/JacksonConfig.scala
@@ -0,0 +1,29 @@
+package de.nowchess.rules.config
+
+import com.fasterxml.jackson.core.Version
+import com.fasterxml.jackson.databind.ObjectMapper
+import com.fasterxml.jackson.databind.module.SimpleModule
+import com.fasterxml.jackson.module.scala.DefaultScalaModule
+import de.nowchess.api.board.Square
+import de.nowchess.api.move.MoveType
+import de.nowchess.rules.json.*
+import io.quarkus.jackson.ObjectMapperCustomizer
+import jakarta.inject.Singleton
+
+@Singleton
+class JacksonConfig extends ObjectMapperCustomizer:
+  def customize(mapper: ObjectMapper): Unit =
+    mapper.registerModule(new DefaultScalaModule() {
+      override def version(): Version =
+        // scalafix:off DisableSyntax.null
+        new Version(2, 21, 1, null, "com.fasterxml.jackson.module", "jackson-module-scala")
+        // scalafix:on DisableSyntax.null
+    })
+    val mod = new SimpleModule()
+    mod.addKeySerializer(classOf[Square], new SquareKeySerializer())
+    mod.addKeyDeserializer(classOf[Square], new SquareKeyDeserializer())
+    mod.addSerializer(classOf[Square], new SquareSerializer())
+    mod.addDeserializer(classOf[Square], new SquareDeserializer())
+    mod.addSerializer(classOf[MoveType], new MoveTypeSerializer())
+    mod.addDeserializer(classOf[MoveType], new MoveTypeDeserializer())
+    mapper.registerModule(mod)
diff --git a/modules/rule/src/main/scala/de/nowchess/rules/config/NativeReflectionConfig.scala b/modules/rule/src/main/scala/de/nowchess/rules/config/NativeReflectionConfig.scala
new file mode 100644
index 0000000..2d6430d
--- /dev/null
+++ b/modules/rule/src/main/scala/de/nowchess/rules/config/NativeReflectionConfig.scala
@@ -0,0 +1,28 @@
+package de.nowchess.rules.config
+
+import de.nowchess.api.board.{CastlingRights, Color, File, Piece, PieceType, Rank, Square}
+import de.nowchess.api.game.{DrawReason, GameContext, GameResult}
+import de.nowchess.api.move.{Move, MoveType, PromotionPiece}
+import de.nowchess.rules.dto.{ContextMoveRequest, ContextSquareRequest}
+import io.quarkus.runtime.annotations.RegisterForReflection
+
+@RegisterForReflection(
+  targets = Array(
+    classOf[ContextSquareRequest],
+    classOf[ContextMoveRequest],
+    classOf[GameContext],
+    classOf[GameResult],
+    classOf[DrawReason],
+    classOf[Color],
+    classOf[Piece],
+    classOf[PieceType],
+    classOf[CastlingRights],
+    classOf[Square],
+    classOf[File],
+    classOf[Rank],
+    classOf[Move],
+    classOf[MoveType],
+    classOf[PromotionPiece],
+  ),
+)
+class NativeReflectionConfig
diff --git a/modules/rule/src/main/scala/de/nowchess/rules/dto/Dtos.scala b/modules/rule/src/main/scala/de/nowchess/rules/dto/Dtos.scala
new file mode 100644
index 0000000..4edf90f
--- /dev/null
+++ b/modules/rule/src/main/scala/de/nowchess/rules/dto/Dtos.scala
@@ -0,0 +1,8 @@
+package de.nowchess.rules.dto
+
+import de.nowchess.api.game.GameContext
+import de.nowchess.api.move.Move
+
+case class ContextSquareRequest(context: GameContext, square: String)
+
+case class ContextMoveRequest(context: GameContext, move: Move)
diff --git a/modules/rule/src/main/scala/de/nowchess/rules/json/MoveTypeDeserializer.scala b/modules/rule/src/main/scala/de/nowchess/rules/json/MoveTypeDeserializer.scala
new file mode 100644
index 0000000..00cee39
--- /dev/null
+++ b/modules/rule/src/main/scala/de/nowchess/rules/json/MoveTypeDeserializer.scala
@@ -0,0 +1,19 @@
+package de.nowchess.rules.json
+
+import com.fasterxml.jackson.core.{JsonParseException, JsonParser}
+import com.fasterxml.jackson.databind.node.ObjectNode
+import com.fasterxml.jackson.databind.{DeserializationContext, JsonDeserializer}
+import de.nowchess.api.move.{MoveType, PromotionPiece}
+
+class MoveTypeDeserializer extends JsonDeserializer[MoveType]:
+  // scalafix:off DisableSyntax.throw
+  override def deserialize(p: JsonParser, ctx: DeserializationContext): MoveType =
+    val node = p.getCodec.readTree[ObjectNode](p)
+    node.get("type").asText() match
+      case "normal"          => MoveType.Normal(node.get("isCapture").asBoolean(false))
+      case "castleKingside"  => MoveType.CastleKingside
+      case "castleQueenside" => MoveType.CastleQueenside
+      case "enPassant"       => MoveType.EnPassant
+      case "promotion"       => MoveType.Promotion(PromotionPiece.valueOf(node.get("piece").asText()))
+      case t                 => throw new JsonParseException(p, s"Unknown move type: $t")
+  // scalafix:on DisableSyntax.throw
diff --git a/modules/rule/src/main/scala/de/nowchess/rules/json/MoveTypeSerializer.scala b/modules/rule/src/main/scala/de/nowchess/rules/json/MoveTypeSerializer.scala
new file mode 100644
index 0000000..1817586
--- /dev/null
+++ b/modules/rule/src/main/scala/de/nowchess/rules/json/MoveTypeSerializer.scala
@@ -0,0 +1,23 @@
+package de.nowchess.rules.json
+
+import com.fasterxml.jackson.core.JsonGenerator
+import com.fasterxml.jackson.databind.{JsonSerializer, SerializerProvider}
+import de.nowchess.api.move.MoveType
+
+class MoveTypeSerializer extends JsonSerializer[MoveType]:
+  override def serialize(value: MoveType, gen: JsonGenerator, provider: SerializerProvider): Unit =
+    gen.writeStartObject()
+    value match
+      case MoveType.Normal(isCapture) =>
+        gen.writeStringField("type", "normal")
+        gen.writeBooleanField("isCapture", isCapture)
+      case MoveType.CastleKingside =>
+        gen.writeStringField("type", "castleKingside")
+      case MoveType.CastleQueenside =>
+        gen.writeStringField("type", "castleQueenside")
+      case MoveType.EnPassant =>
+        gen.writeStringField("type", "enPassant")
+      case MoveType.Promotion(piece) =>
+        gen.writeStringField("type", "promotion")
+        gen.writeStringField("piece", piece.toString)
+    gen.writeEndObject()
diff --git a/modules/rule/src/main/scala/de/nowchess/rules/json/SquareDeserializer.scala b/modules/rule/src/main/scala/de/nowchess/rules/json/SquareDeserializer.scala
new file mode 100644
index 0000000..0be5f92
--- /dev/null
+++ b/modules/rule/src/main/scala/de/nowchess/rules/json/SquareDeserializer.scala
@@ -0,0 +1,9 @@
+package de.nowchess.rules.json
+
+import com.fasterxml.jackson.core.JsonParser
+import com.fasterxml.jackson.databind.{DeserializationContext, JsonDeserializer}
+import de.nowchess.api.board.Square
+
+class SquareDeserializer extends JsonDeserializer[Square]:
+  override def deserialize(p: JsonParser, ctx: DeserializationContext): Square =
+    Square.fromAlgebraic(p.getText).orNull
diff --git a/modules/rule/src/main/scala/de/nowchess/rules/json/SquareKeyDeserializer.scala b/modules/rule/src/main/scala/de/nowchess/rules/json/SquareKeyDeserializer.scala
new file mode 100644
index 0000000..4d52c10
--- /dev/null
+++ b/modules/rule/src/main/scala/de/nowchess/rules/json/SquareKeyDeserializer.scala
@@ -0,0 +1,8 @@
+package de.nowchess.rules.json
+
+import com.fasterxml.jackson.databind.{DeserializationContext, KeyDeserializer}
+import de.nowchess.api.board.Square
+
+class SquareKeyDeserializer extends KeyDeserializer:
+  override def deserializeKey(key: String, ctx: DeserializationContext): AnyRef =
+    Square.fromAlgebraic(key).orNull
diff --git a/modules/rule/src/main/scala/de/nowchess/rules/json/SquareKeySerializer.scala b/modules/rule/src/main/scala/de/nowchess/rules/json/SquareKeySerializer.scala
new file mode 100644
index 0000000..3ef02a5
--- /dev/null
+++ b/modules/rule/src/main/scala/de/nowchess/rules/json/SquareKeySerializer.scala
@@ -0,0 +1,9 @@
+package de.nowchess.rules.json
+
+import com.fasterxml.jackson.core.JsonGenerator
+import com.fasterxml.jackson.databind.{JsonSerializer, SerializerProvider}
+import de.nowchess.api.board.Square
+
+class SquareKeySerializer extends JsonSerializer[Square]:
+  override def serialize(value: Square, gen: JsonGenerator, provider: SerializerProvider): Unit =
+    gen.writeFieldName(value.toString)
diff --git a/modules/rule/src/main/scala/de/nowchess/rules/json/SquareSerializer.scala b/modules/rule/src/main/scala/de/nowchess/rules/json/SquareSerializer.scala
new file mode 100644
index 0000000..93aaca9
--- /dev/null
+++ b/modules/rule/src/main/scala/de/nowchess/rules/json/SquareSerializer.scala
@@ -0,0 +1,9 @@
+package de.nowchess.rules.json
+
+import com.fasterxml.jackson.core.JsonGenerator
+import com.fasterxml.jackson.databind.{JsonSerializer, SerializerProvider}
+import de.nowchess.api.board.Square
+
+class SquareSerializer extends JsonSerializer[Square]:
+  override def serialize(value: Square, gen: JsonGenerator, provider: SerializerProvider): Unit =
+    gen.writeString(value.toString)
diff --git a/modules/rule/src/main/scala/de/nowchess/rules/resource/RuleSetResource.scala b/modules/rule/src/main/scala/de/nowchess/rules/resource/RuleSetResource.scala
new file mode 100644
index 0000000..d128519
--- /dev/null
+++ b/modules/rule/src/main/scala/de/nowchess/rules/resource/RuleSetResource.scala
@@ -0,0 +1,90 @@
+package de.nowchess.rules.resource
+
+import de.nowchess.api.board.Square
+import de.nowchess.api.game.GameContext
+import de.nowchess.api.move.Move
+import de.nowchess.rules.dto.*
+import de.nowchess.rules.sets.DefaultRules
+import jakarta.enterprise.context.ApplicationScoped
+import jakarta.ws.rs.*
+import jakarta.ws.rs.core.MediaType
+
+@Path("/api/rules")
+@ApplicationScoped
+class RuleSetResource:
+  private val rules = DefaultRules
+
+  // scalafix:off DisableSyntax.throw
+  private def parseSquare(s: String): Square =
+    Square.fromAlgebraic(s).getOrElse(throw new BadRequestException(s"Invalid square: $s"))
+  // scalafix:on DisableSyntax.throw
+
+  @POST
+  @Path("/candidate-moves")
+  @Consumes(Array(MediaType.APPLICATION_JSON))
+  @Produces(Array(MediaType.APPLICATION_JSON))
+  def candidateMoves(req: ContextSquareRequest): List[Move] =
+    rules.candidateMoves(req.context)(parseSquare(req.square))
+
+  @POST
+  @Path("/legal-moves")
+  @Consumes(Array(MediaType.APPLICATION_JSON))
+  @Produces(Array(MediaType.APPLICATION_JSON))
+  def legalMoves(req: ContextSquareRequest): List[Move] =
+    rules.legalMoves(req.context)(parseSquare(req.square))
+
+  @POST
+  @Path("/all-legal-moves")
+  @Consumes(Array(MediaType.APPLICATION_JSON))
+  @Produces(Array(MediaType.APPLICATION_JSON))
+  def allLegalMoves(ctx: GameContext): List[Move] =
+    rules.allLegalMoves(ctx)
+
+  @POST
+  @Path("/is-check")
+  @Consumes(Array(MediaType.APPLICATION_JSON))
+  @Produces(Array(MediaType.APPLICATION_JSON))
+  def isCheck(ctx: GameContext): Boolean =
+    rules.isCheck(ctx)
+
+  @POST
+  @Path("/is-checkmate")
+  @Consumes(Array(MediaType.APPLICATION_JSON))
+  @Produces(Array(MediaType.APPLICATION_JSON))
+  def isCheckmate(ctx: GameContext): Boolean =
+    rules.isCheckmate(ctx)
+
+  @POST
+  @Path("/is-stalemate")
+  @Consumes(Array(MediaType.APPLICATION_JSON))
+  @Produces(Array(MediaType.APPLICATION_JSON))
+  def isStalemate(ctx: GameContext): Boolean =
+    rules.isStalemate(ctx)
+
+  @POST
+  @Path("/is-insufficient-material")
+  @Consumes(Array(MediaType.APPLICATION_JSON))
+  @Produces(Array(MediaType.APPLICATION_JSON))
+  def isInsufficientMaterial(ctx: GameContext): Boolean =
+    rules.isInsufficientMaterial(ctx)
+
+  @POST
+  @Path("/is-fifty-move-rule")
+  @Consumes(Array(MediaType.APPLICATION_JSON))
+  @Produces(Array(MediaType.APPLICATION_JSON))
+  def isFiftyMoveRule(ctx: GameContext): Boolean =
+    rules.isFiftyMoveRule(ctx)
+
+  @POST
+  @Path("/is-threefold-repetition")
+  @Consumes(Array(MediaType.APPLICATION_JSON))
+  @Produces(Array(MediaType.APPLICATION_JSON))
+  def isThreefoldRepetition(ctx: GameContext): Boolean =
+    rules.isThreefoldRepetition(ctx)
+
+  @POST
+  @Path("/apply-move")
+  @Consumes(Array(MediaType.APPLICATION_JSON))
+  @Produces(Array(MediaType.APPLICATION_JSON))
+  def applyMove(req: ContextMoveRequest): GameContext =
+    rules.applyMove(req.context)(req.move)
diff --git a/modules/rule/src/main/scala/de/nowchess/rules/sets/DefaultRules.scala b/modules/rule/src/main/scala/de/nowchess/rules/sets/DefaultRules.scala
index 036f00d..ed3bde2 100644
--- a/modules/rule/src/main/scala/de/nowchess/rules/sets/DefaultRules.scala
+++ b/modules/rule/src/main/scala/de/nowchess/rules/sets/DefaultRules.scala
@@ -3,7 +3,7 @@ package de.nowchess.rules.sets
 import de.nowchess.api.board.*
 import de.nowchess.api.game.GameContext
 import de.nowchess.api.move.{Move, MoveType, PromotionPiece}
-import de.nowchess.rules.RuleSet
+import de.nowchess.api.rules.RuleSet
 
 import scala.annotation.tailrec
 
diff --git a/modules/rule/src/test/scala/de/nowchess/rules/config/JacksonConfigTest.scala b/modules/rule/src/test/scala/de/nowchess/rules/config/JacksonConfigTest.scala
new file mode 100644
index 0000000..27c738d
--- /dev/null
+++ b/modules/rule/src/test/scala/de/nowchess/rules/config/JacksonConfigTest.scala
@@ -0,0 +1,30 @@
+package de.nowchess.rules.config
+
+import com.fasterxml.jackson.databind.ObjectMapper
+import de.nowchess.api.board.{File, Rank, Square}
+import de.nowchess.api.move.MoveType
+import org.scalatest.funsuite.AnyFunSuite
+import org.scalatest.matchers.should.Matchers
+
+class JacksonConfigTest extends AnyFunSuite with Matchers:
+
+  private val mapper: ObjectMapper =
+    val m = new ObjectMapper()
+    new JacksonConfig().customize(m)
+    m
+
+  test("customize enables Option serialization via DefaultScalaModule"):
+    mapper.writeValueAsString(None) shouldBe "null"
+    mapper.writeValueAsString(Some("hello")) shouldBe """"hello""""
+
+  test("customize registers SquareSerializer"):
+    mapper.writeValueAsString(Square(File.E, Rank.R4)) shouldBe """"e4""""
+
+  test("customize registers MoveTypeSerializer"):
+    mapper.writeValueAsString(MoveType.CastleKingside) shouldBe """{"type":"castleKingside"}"""
+
+  test("customize registers SquareDeserializer"):
+    mapper.readValue(""""e4"""", classOf[Square]) shouldBe Square(File.E, Rank.R4)
+
+  test("customize registers MoveTypeDeserializer"):
+    mapper.readValue("""{"type":"enPassant"}""", classOf[MoveType]) shouldBe MoveType.EnPassant
diff --git a/modules/rule/src/test/scala/de/nowchess/rules/json/JsonSerializersTest.scala b/modules/rule/src/test/scala/de/nowchess/rules/json/JsonSerializersTest.scala
new file mode 100644
index 0000000..e832fcb
--- /dev/null
+++ b/modules/rule/src/test/scala/de/nowchess/rules/json/JsonSerializersTest.scala
@@ -0,0 +1,102 @@
+package de.nowchess.rules.json
+
+import com.fasterxml.jackson.databind.ObjectMapper
+import com.fasterxml.jackson.databind.module.SimpleModule
+import com.fasterxml.jackson.module.scala.DefaultScalaModule
+import de.nowchess.api.board.{File, Rank, Square}
+import de.nowchess.api.move.{MoveType, PromotionPiece}
+import org.scalatest.funsuite.AnyFunSuite
+import org.scalatest.matchers.should.Matchers
+
+class JsonSerializersTest extends AnyFunSuite with Matchers:
+
+  private val mapper: ObjectMapper =
+    val m   = new ObjectMapper()
+    val mod = new SimpleModule()
+    m.registerModule(DefaultScalaModule)
+    mod.addKeySerializer(classOf[Square], new SquareKeySerializer())
+    mod.addKeyDeserializer(classOf[Square], new SquareKeyDeserializer())
+    mod.addSerializer(classOf[Square], new SquareSerializer())
+    mod.addDeserializer(classOf[Square], new SquareDeserializer())
+    mod.addSerializer(classOf[MoveType], new MoveTypeSerializer())
+    mod.addDeserializer(classOf[MoveType], new MoveTypeDeserializer())
+    m.registerModule(mod)
+    m
+
+  private val e4 = Square(File.E, Rank.R4)
+
+  // ── SquareKeySerializer ───────────────────────────────────────────
+
+  test("SquareKeySerializer writes square as map field name"):
+    mapper.writeValueAsString(Map(e4 -> "piece")) shouldBe """{"e4":"piece"}"""
+
+  // ── SquareKeyDeserializer ─────────────────────────────────────────
+
+  // scalafix:off DisableSyntax.null
+  test("SquareKeyDeserializer returns square for valid key"):
+    new SquareKeyDeserializer().deserializeKey("e4", null) shouldBe e4
+
+  test("SquareKeyDeserializer returns null for invalid key"):
+    new SquareKeyDeserializer().deserializeKey("z9", null) shouldBe null
+  // scalafix:on DisableSyntax.null
+
+  // ── SquareSerializer/Deserializer ─────────────────────────────────
+
+  test("SquareSerializer writes square as string"):
+    mapper.writeValueAsString(e4) shouldBe """"e4""""
+
+  test("SquareDeserializer reads valid square string"):
+    mapper.readValue(""""e4"""", classOf[Square]) shouldBe e4
+
+  // scalafix:off DisableSyntax.null
+  test("SquareDeserializer returns null for invalid square string"):
+    mapper.readValue(""""z9"""", classOf[Square]) shouldBe null
+  // scalafix:on DisableSyntax.null
+
+  // ── MoveTypeSerializer ────────────────────────────────────────────
+
+  test("MoveTypeSerializer serializes Normal non-capture"):
+    mapper.writeValueAsString(MoveType.Normal(false)) shouldBe """{"type":"normal","isCapture":false}"""
+
+  test("MoveTypeSerializer serializes Normal capture"):
+    mapper.writeValueAsString(MoveType.Normal(true)) shouldBe """{"type":"normal","isCapture":true}"""
+
+  test("MoveTypeSerializer serializes CastleKingside"):
+    mapper.writeValueAsString(MoveType.CastleKingside) shouldBe """{"type":"castleKingside"}"""
+
+  test("MoveTypeSerializer serializes CastleQueenside"):
+    mapper.writeValueAsString(MoveType.CastleQueenside) shouldBe """{"type":"castleQueenside"}"""
+
+  test("MoveTypeSerializer serializes EnPassant"):
+    mapper.writeValueAsString(MoveType.EnPassant) shouldBe """{"type":"enPassant"}"""
+
+  test("MoveTypeSerializer serializes Promotion"):
+    mapper.writeValueAsString(MoveType.Promotion(PromotionPiece.Queen)) shouldBe
+      """{"type":"promotion","piece":"Queen"}"""
+
+  // ── MoveTypeDeserializer ──────────────────────────────────────────
+
+  test("MoveTypeDeserializer deserializes normal non-capture"):
+    mapper.readValue("""{"type":"normal","isCapture":false}""", classOf[MoveType]) shouldBe
+      MoveType.Normal(false)
+
+  test("MoveTypeDeserializer deserializes normal capture"):
+    mapper.readValue("""{"type":"normal","isCapture":true}""", classOf[MoveType]) shouldBe
+      MoveType.Normal(true)
+
+  test("MoveTypeDeserializer deserializes castleKingside"):
+    mapper.readValue("""{"type":"castleKingside"}""", classOf[MoveType]) shouldBe MoveType.CastleKingside
+
+  test("MoveTypeDeserializer deserializes castleQueenside"):
+    mapper.readValue("""{"type":"castleQueenside"}""", classOf[MoveType]) shouldBe MoveType.CastleQueenside
+
+  test("MoveTypeDeserializer deserializes enPassant"):
+    mapper.readValue("""{"type":"enPassant"}""", classOf[MoveType]) shouldBe MoveType.EnPassant
+
+  test("MoveTypeDeserializer deserializes promotion"):
+    mapper.readValue("""{"type":"promotion","piece":"Rook"}""", classOf[MoveType]) shouldBe
+      MoveType.Promotion(PromotionPiece.Rook)
+
+  test("MoveTypeDeserializer throws for unknown type"):
+    an[Exception] should be thrownBy
+      mapper.readValue("""{"type":"unknown"}""", classOf[MoveType])
diff --git a/modules/rule/src/test/scala/de/nowchess/rules/resource/RuleSetResourceTest.scala b/modules/rule/src/test/scala/de/nowchess/rules/resource/RuleSetResourceTest.scala
new file mode 100644
index 0000000..1e2f9a6
--- /dev/null
+++ b/modules/rule/src/test/scala/de/nowchess/rules/resource/RuleSetResourceTest.scala
@@ -0,0 +1,301 @@
+package de.nowchess.rules.resource
+
+import com.fasterxml.jackson.databind.ObjectMapper
+import de.nowchess.api.board.{Board, CastlingRights, Color, File, Piece, PieceType, Rank, Square}
+import de.nowchess.api.game.GameContext
+import de.nowchess.api.move.Move
+import de.nowchess.rules.config.JacksonConfig
+import de.nowchess.rules.dto.{ContextMoveRequest, ContextSquareRequest}
+import de.nowchess.rules.sets.DefaultRules
+import io.quarkus.test.junit.QuarkusTest
+import io.restassured.RestAssured
+import io.restassured.http.ContentType
+import org.hamcrest.Matchers.*
+import org.junit.jupiter.api.Test
+
+@QuarkusTest
+class RuleSetResourceTest:
+
+  private val mapper: ObjectMapper =
+    val m = new ObjectMapper()
+    new JacksonConfig().customize(m)
+    m
+
+  private val rules = DefaultRules
+
+  private def request() = RestAssured.`given`()
+
+  private def toJson(value: AnyRef): String = mapper.writeValueAsString(value)
+
+  private def contextSquareBody(ctx: GameContext, square: String): String =
+    toJson(ContextSquareRequest(ctx, square))
+
+  private def contextMoveBody(ctx: GameContext, move: Move): String =
+    toJson(ContextMoveRequest(ctx, move))
+
+  // ── all-legal-moves ───────────────────────────────────────────────
+
+  @Test
+  def allLegalMoves_initialPositionHas20Moves(): Unit =
+    request()
+      .contentType(ContentType.JSON)
+      .body(toJson(GameContext.initial))
+      .when()
+      .post("/api/rules/all-legal-moves")
+      .`then`()
+      .statusCode(200)
+      .body("size()", is(20))
+
+  // ── legal-moves ───────────────────────────────────────────────────
+
+  @Test
+  def legalMoves_e2PawnHas2Moves(): Unit =
+    request()
+      .contentType(ContentType.JSON)
+      .body(contextSquareBody(GameContext.initial, "e2"))
+      .when()
+      .post("/api/rules/legal-moves")
+      .`then`()
+      .statusCode(200)
+      .body("size()", is(2))
+
+  // ── candidate-moves ───────────────────────────────────────────────
+
+  @Test
+  def candidateMoves_e2PawnHas2Candidates(): Unit =
+    request()
+      .contentType(ContentType.JSON)
+      .body(contextSquareBody(GameContext.initial, "e2"))
+      .when()
+      .post("/api/rules/candidate-moves")
+      .`then`()
+      .statusCode(200)
+      .body("size()", is(2))
+
+  // ── is-check ──────────────────────────────────────────────────────
+
+  @Test
+  def isCheck_falseForInitialPosition(): Unit =
+    request()
+      .contentType(ContentType.JSON)
+      .body(toJson(GameContext.initial))
+      .when()
+      .post("/api/rules/is-check")
+      .`then`()
+      .statusCode(200)
+      .body(is("false"))
+
+  @Test
+  def isCheck_trueWhenKingAttacked(): Unit =
+    request()
+      .contentType(ContentType.JSON)
+      .body(toJson(buildCheckContext()))
+      .when()
+      .post("/api/rules/is-check")
+      .`then`()
+      .statusCode(200)
+      .body(is("true"))
+
+  // ── is-checkmate ──────────────────────────────────────────────────
+
+  @Test
+  def isCheckmate_falseForInitialPosition(): Unit =
+    request()
+      .contentType(ContentType.JSON)
+      .body(toJson(GameContext.initial))
+      .when()
+      .post("/api/rules/is-checkmate")
+      .`then`()
+      .statusCode(200)
+      .body(is("false"))
+
+  @Test
+  def isCheckmate_trueForFoolsMate(): Unit =
+    request()
+      .contentType(ContentType.JSON)
+      .body(toJson(buildFoolsMate()))
+      .when()
+      .post("/api/rules/is-checkmate")
+      .`then`()
+      .statusCode(200)
+      .body(is("true"))
+
+  // ── is-stalemate ──────────────────────────────────────────────────
+
+  @Test
+  def isStalemate_falseForInitialPosition(): Unit =
+    request()
+      .contentType(ContentType.JSON)
+      .body(toJson(GameContext.initial))
+      .when()
+      .post("/api/rules/is-stalemate")
+      .`then`()
+      .statusCode(200)
+      .body(is("false"))
+
+  @Test
+  def isStalemate_trueForStalematePosition(): Unit =
+    request()
+      .contentType(ContentType.JSON)
+      .body(toJson(buildStalemateContext()))
+      .when()
+      .post("/api/rules/is-stalemate")
+      .`then`()
+      .statusCode(200)
+      .body(is("true"))
+
+  // ── is-insufficient-material ──────────────────────────────────────
+
+  @Test
+  def isInsufficientMaterial_falseForInitialPosition(): Unit =
+    request()
+      .contentType(ContentType.JSON)
+      .body(toJson(GameContext.initial))
+      .when()
+      .post("/api/rules/is-insufficient-material")
+      .`then`()
+      .statusCode(200)
+      .body(is("false"))
+
+  @Test
+  def isInsufficientMaterial_trueForKingsOnly(): Unit =
+    request()
+      .contentType(ContentType.JSON)
+      .body(toJson(buildKingsOnlyContext()))
+      .when()
+      .post("/api/rules/is-insufficient-material")
+      .`then`()
+      .statusCode(200)
+      .body(is("true"))
+
+  // ── is-fifty-move-rule ────────────────────────────────────────────
+
+  @Test
+  def isFiftyMoveRule_falseForInitialPosition(): Unit =
+    request()
+      .contentType(ContentType.JSON)
+      .body(toJson(GameContext.initial))
+      .when()
+      .post("/api/rules/is-fifty-move-rule")
+      .`then`()
+      .statusCode(200)
+      .body(is("false"))
+
+  @Test
+  def isFiftyMoveRule_trueWhenClockAt100(): Unit =
+    request()
+      .contentType(ContentType.JSON)
+      .body(toJson(GameContext.initial.copy(halfMoveClock = 100)))
+      .when()
+      .post("/api/rules/is-fifty-move-rule")
+      .`then`()
+      .statusCode(200)
+      .body(is("true"))
+
+  // ── is-threefold-repetition ───────────────────────────────────────
+
+  @Test
+  def isThreefoldRepetition_falseForInitialPosition(): Unit =
+    request()
+      .contentType(ContentType.JSON)
+      .body(toJson(GameContext.initial))
+      .when()
+      .post("/api/rules/is-threefold-repetition")
+      .`then`()
+      .statusCode(200)
+      .body(is("false"))
+
+  @Test
+  def isThreefoldRepetition_trueAfterRepeatedMoves(): Unit =
+    request()
+      .contentType(ContentType.JSON)
+      .body(toJson(buildThreefoldContext()))
+      .when()
+      .post("/api/rules/is-threefold-repetition")
+      .`then`()
+      .statusCode(200)
+      .body(is("true"))
+
+  // ── apply-move ────────────────────────────────────────────────────
+
+  @Test
+  def applyMove_updatesContext(): Unit =
+    val move = rules
+      .legalMoves(GameContext.initial)(Square(File.E, Rank.R2))
+      .find(_.to == Square(File.E, Rank.R4))
+      .get
+    request()
+      .contentType(ContentType.JSON)
+      .body(contextMoveBody(GameContext.initial, move))
+      .when()
+      .post("/api/rules/apply-move")
+      .`then`()
+      .statusCode(200)
+      .body("turn", is("Black"))
+
+  // ── error handling ────────────────────────────────────────────────
+
+  @Test
+  def invalidSquare_returns400(): Unit =
+    request()
+      .contentType(ContentType.JSON)
+      .body(toJson(ContextSquareRequest(GameContext.initial, "z9")))
+      .when()
+      .post("/api/rules/legal-moves")
+      .`then`()
+      .statusCode(400)
+
+  // ── position builders ─────────────────────────────────────────────
+
+  private def buildCheckContext(): GameContext =
+    val board = Board(
+      Map(
+        Square(File.E, Rank.R1) -> Piece(Color.White, PieceType.King),
+        Square(File.E, Rank.R8) -> Piece(Color.Black, PieceType.King),
+        Square(File.E, Rank.R3) -> Piece(Color.Black, PieceType.Rook),
+      ),
+    )
+    GameContext(board, Color.White, CastlingRights.None, None, 0, List.empty, initialBoard = board)
+
+  private def buildFoolsMate(): GameContext =
+    val moves = List(("f2", "f3"), ("e7", "e5"), ("g2", "g4"), ("d8", "h4"))
+    moves.foldLeft(GameContext.initial) { (ctx, fromTo) =>
+      val from = Square.fromAlgebraic(fromTo._1).get
+      val to   = Square.fromAlgebraic(fromTo._2).get
+      rules.legalMoves(ctx)(from).find(_.to == to).fold(ctx)(rules.applyMove(ctx))
+    }
+
+  private def buildStalemateContext(): GameContext =
+    val board = Board(
+      Map(
+        Square(File.H, Rank.R8) -> Piece(Color.Black, PieceType.King),
+        Square(File.F, Rank.R7) -> Piece(Color.White, PieceType.Queen),
+        Square(File.G, Rank.R6) -> Piece(Color.White, PieceType.King),
+      ),
+    )
+    GameContext(board, Color.Black, CastlingRights.None, None, 0, List.empty, initialBoard = board)
+
+  private def buildKingsOnlyContext(): GameContext =
+    val board = Board(
+      Map(
+        Square(File.E, Rank.R1) -> Piece(Color.White, PieceType.King),
+        Square(File.E, Rank.R8) -> Piece(Color.Black, PieceType.King),
+      ),
+    )
+    GameContext(board, Color.White, CastlingRights.None, None, 0, List.empty, initialBoard = board)
+
+  private def buildThreefoldContext(): GameContext =
+    val g1 = Square(File.G, Rank.R1)
+    val f3 = Square(File.F, Rank.R3)
+    val g8 = Square(File.G, Rank.R8)
+    val f6 = Square(File.F, Rank.R6)
+    def mv(ctx: GameContext, from: Square, to: Square): GameContext =
+      rules.legalMoves(ctx)(from).find(_.to == to).fold(ctx)(rules.applyMove(ctx))
+    val ctx1 = mv(GameContext.initial, g1, f3)
+    val ctx2 = mv(ctx1, g8, f6)
+    val ctx3 = mv(ctx2, f3, g1)
+    val ctx4 = mv(ctx3, f6, g8)
+    val ctx5 = mv(ctx4, g1, f3)
+    val ctx6 = mv(ctx5, g8, f6)
+    val ctx7 = mv(ctx6, f3, g1)
+    mv(ctx7, f6, g8)
diff --git a/modules/rule/src/test/scala/de/nowchess/rules/resource/RuleSetResourceUnitTest.scala b/modules/rule/src/test/scala/de/nowchess/rules/resource/RuleSetResourceUnitTest.scala
new file mode 100644
index 0000000..4159df5
--- /dev/null
+++ b/modules/rule/src/test/scala/de/nowchess/rules/resource/RuleSetResourceUnitTest.scala
@@ -0,0 +1,153 @@
+package de.nowchess.rules.resource
+
+import de.nowchess.api.board.{Board, CastlingRights, Color, File, Piece, PieceType, Rank, Square}
+import de.nowchess.api.game.GameContext
+import de.nowchess.api.move.Move
+import de.nowchess.rules.dto.{ContextMoveRequest, ContextSquareRequest}
+import de.nowchess.rules.sets.DefaultRules
+import jakarta.ws.rs.BadRequestException
+import org.scalatest.funsuite.AnyFunSuite
+import org.scalatest.matchers.should.Matchers
+
+class RuleSetResourceUnitTest extends AnyFunSuite with Matchers:
+
+  private val resource = new RuleSetResource()
+  private val rules    = DefaultRules
+
+  private def ctxSq(g: GameContext, sq: String) = ContextSquareRequest(g, sq)
+  private def ctxMv(g: GameContext, m: Move)    = ContextMoveRequest(g, m)
+
+  // ── position builders ─────────────────────────────────────────────
+
+  private def checkContext(): GameContext =
+    val board = Board(
+      Map(
+        Square(File.E, Rank.R1) -> Piece(Color.White, PieceType.King),
+        Square(File.E, Rank.R8) -> Piece(Color.Black, PieceType.King),
+        Square(File.E, Rank.R3) -> Piece(Color.Black, PieceType.Rook),
+      ),
+    )
+    GameContext(board, Color.White, CastlingRights.None, None, 0, List.empty, initialBoard = board)
+
+  private def foolsMate(): GameContext =
+    val moves = List(("f2", "f3"), ("e7", "e5"), ("g2", "g4"), ("d8", "h4"))
+    moves.foldLeft(GameContext.initial) { (c, ft) =>
+      val from = Square.fromAlgebraic(ft._1).get
+      val to   = Square.fromAlgebraic(ft._2).get
+      rules.legalMoves(c)(from).find(_.to == to).fold(c)(rules.applyMove(c))
+    }
+
+  private def stalemateContext(): GameContext =
+    val board = Board(
+      Map(
+        Square(File.H, Rank.R8) -> Piece(Color.Black, PieceType.King),
+        Square(File.F, Rank.R7) -> Piece(Color.White, PieceType.Queen),
+        Square(File.G, Rank.R6) -> Piece(Color.White, PieceType.King),
+      ),
+    )
+    GameContext(board, Color.Black, CastlingRights.None, None, 0, List.empty, initialBoard = board)
+
+  private def kingsOnlyContext(): GameContext =
+    val board = Board(
+      Map(
+        Square(File.E, Rank.R1) -> Piece(Color.White, PieceType.King),
+        Square(File.E, Rank.R8) -> Piece(Color.Black, PieceType.King),
+      ),
+    )
+    GameContext(board, Color.White, CastlingRights.None, None, 0, List.empty, initialBoard = board)
+
+  private def threefoldContext(): GameContext =
+    val g1 = Square(File.G, Rank.R1)
+    val f3 = Square(File.F, Rank.R3)
+    val g8 = Square(File.G, Rank.R8)
+    val f6 = Square(File.F, Rank.R6)
+    def mv(c: GameContext, from: Square, to: Square): GameContext =
+      rules.legalMoves(c)(from).find(_.to == to).fold(c)(rules.applyMove(c))
+    val c1 = mv(GameContext.initial, g1, f3)
+    val c2 = mv(c1, g8, f6)
+    val c3 = mv(c2, f3, g1)
+    val c4 = mv(c3, f6, g8)
+    val c5 = mv(c4, g1, f3)
+    val c6 = mv(c5, g8, f6)
+    val c7 = mv(c6, f3, g1)
+    mv(c7, f6, g8)
+
+  // ── allLegalMoves ─────────────────────────────────────────────────
+
+  test("allLegalMoves returns 20 moves for initial position"):
+    resource.allLegalMoves(GameContext.initial) should have size 20
+
+  // ── legalMoves ────────────────────────────────────────────────────
+
+  test("legalMoves returns 2 moves for e2 pawn"):
+    resource.legalMoves(ctxSq(GameContext.initial, "e2")) should have size 2
+
+  test("legalMoves throws BadRequestException for invalid square"):
+    an[BadRequestException] should be thrownBy
+      resource.legalMoves(ctxSq(GameContext.initial, "z9"))
+
+  // ── candidateMoves ────────────────────────────────────────────────
+
+  test("candidateMoves returns moves for e2 pawn"):
+    resource.candidateMoves(ctxSq(GameContext.initial, "e2")) should not be empty
+
+  test("candidateMoves throws BadRequestException for invalid square"):
+    an[BadRequestException] should be thrownBy
+      resource.candidateMoves(ctxSq(GameContext.initial, "z9"))
+
+  // ── isCheck ───────────────────────────────────────────────────────
+
+  test("isCheck returns false for initial position"):
+    resource.isCheck(GameContext.initial) shouldBe false
+
+  test("isCheck returns true when king is attacked"):
+    resource.isCheck(checkContext()) shouldBe true
+
+  // ── isCheckmate ───────────────────────────────────────────────────
+
+  test("isCheckmate returns false for initial position"):
+    resource.isCheckmate(GameContext.initial) shouldBe false
+
+  test("isCheckmate returns true for Fool's mate"):
+    resource.isCheckmate(foolsMate()) shouldBe true
+
+  // ── isStalemate ───────────────────────────────────────────────────
+
+  test("isStalemate returns false for initial position"):
+    resource.isStalemate(GameContext.initial) shouldBe false
+
+  test("isStalemate returns true for stalemate position"):
+    resource.isStalemate(stalemateContext()) shouldBe true
+
+  // ── isInsufficientMaterial ────────────────────────────────────────
+
+  test("isInsufficientMaterial returns false for initial position"):
+    resource.isInsufficientMaterial(GameContext.initial) shouldBe false
+
+  test("isInsufficientMaterial returns true for kings only"):
+    resource.isInsufficientMaterial(kingsOnlyContext()) shouldBe true
+
+  // ── isFiftyMoveRule ───────────────────────────────────────────────
+
+  test("isFiftyMoveRule returns false for initial position"):
+    resource.isFiftyMoveRule(GameContext.initial) shouldBe false
+
+  test("isFiftyMoveRule returns true when halfMoveClock is 100"):
+    resource.isFiftyMoveRule(GameContext.initial.copy(halfMoveClock = 100)) shouldBe true
+
+  // ── isThreefoldRepetition ─────────────────────────────────────────
+
+  test("isThreefoldRepetition returns false for initial position"):
+    resource.isThreefoldRepetition(GameContext.initial) shouldBe false
+
+  test("isThreefoldRepetition returns true after repeated moves"):
+    resource.isThreefoldRepetition(threefoldContext()) shouldBe true
+
+  // ── applyMove ─────────────────────────────────────────────────────
+
+  test("applyMove returns updated context with switched turn"):
+    val move = rules
+      .legalMoves(GameContext.initial)(Square(File.E, Rank.R2))
+      .find(_.to == Square(File.E, Rank.R4))
+      .get
+    resource.applyMove(ctxMv(GameContext.initial, move)).turn shouldBe Color.Black