diff --git a/.idea/scala_settings.xml b/.idea/scala_settings.xml
new file mode 100644
index 0000000..4608fe0
--- /dev/null
+++ b/.idea/scala_settings.xml
@@ -0,0 +1,6 @@
+<?xml version="1.0" encoding="UTF-8"?>
+<project version="4">
+  <component name="ScalaProjectSettings">
+    <option name="scala3DisclaimerShown" value="true" />
+  </component>
+</project>
\ No newline at end of file
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 b252cec..188a328 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
@@ -1,6 +1,5 @@
 package de.nowchess.chess.config
 
-import com.fasterxml.jackson.core.Version
 import com.fasterxml.jackson.databind.ObjectMapper
 import com.fasterxml.jackson.module.scala.DefaultScalaModule
 import io.quarkus.jackson.ObjectMapperCustomizer
@@ -9,9 +8,4 @@ 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
-    })
+    mapper.registerModule(DefaultScalaModule)
diff --git a/modules/core/src/main/scala/de/nowchess/chess/registry/GameEntry.scala b/modules/core/src/main/scala/de/nowchess/chess/registry/GameEntry.scala
index 7dd09fb..74c240e 100644
--- a/modules/core/src/main/scala/de/nowchess/chess/registry/GameEntry.scala
+++ b/modules/core/src/main/scala/de/nowchess/chess/registry/GameEntry.scala
@@ -9,5 +9,6 @@ final case class GameEntry(
     engine: GameEngine,
     white: PlayerInfo,
     black: PlayerInfo,
+    drawOfferedBy: Option[Color] = None,
     resigned: Boolean = false,
 )
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 e8258bb..7520810 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
@@ -20,19 +20,10 @@ import jakarta.ws.rs.*
 import jakarta.ws.rs.core.{MediaType, Response}
 
 import java.util.concurrent.atomic.AtomicReference
-import scala.compiletime.uninitialized
 
 @Path("/api/board/game")
 @ApplicationScoped
-class GameResource:
-
-  // scalafix:off DisableSyntax.var
-  @Inject
-  var registry: GameRegistry = uninitialized
-
-  @Inject
-  var objectMapper: ObjectMapper = uninitialized
-  // scalafix:on DisableSyntax.var
+class GameResource(@Inject val registry: GameRegistry, @Inject val objectMapper: ObjectMapper):
 
   private val DefaultWhite = PlayerInfo(PlayerId("p1"), "Player 1")
   private val DefaultBlack = PlayerInfo(PlayerId("p2"), "Player 2")
@@ -40,7 +31,7 @@ class GameResource:
   // ── mapping ──────────────────────────────────────────────────────────────
 
   private def statusOf(entry: GameEntry): String =
-    if entry.engine.pendingDrawOfferBy.isDefined then "drawOffered"
+    if entry.drawOfferedBy.isDefined then "drawOffered"
     else
       val ctx = entry.engine.context
       ctx.result match
@@ -113,7 +104,7 @@ class GameResource:
     val error = new AtomicReference[Option[String]](None)
     val obs = new Observer:
       def onGameEvent(e: GameEvent): Unit = e match
-        case InvalidMoveEvent(_, reason) => error.set(Some(reason.toString))
+        case InvalidMoveEvent(_, reason) => error.set(Some(reason))
         case _                           => ()
     engine.subscribe(obs)
     engine.processUserInput(uci)
@@ -142,7 +133,6 @@ 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
@@ -245,16 +235,26 @@ class GameResource:
     assertGameNotOver(entry)
     action match
       case "offer" =>
-        entry.engine.offerDraw(entry.engine.context.turn)
+        registry.update(entry.copy(drawOfferedBy = Some(entry.engine.context.turn)))
         ok(OkResponseDto())
       case "accept" =>
-        entry.engine.acceptDraw(entry.engine.context.turn)
-        ok(OkResponseDto())
+        entry.drawOfferedBy match
+          case None =>
+            throw BadRequestException("NO_DRAW_OFFER", "No draw offer to accept")
+          case Some(offerer) if offerer == entry.engine.context.turn =>
+            throw BadRequestException("CANNOT_ACCEPT_OWN_OFFER", "Cannot accept your own draw offer")
+          case _ =>
+            entry.engine.applyDraw(DrawReason.Agreement)
+            registry.update(entry.copy(drawOfferedBy = None))
+            ok(OkResponseDto())
       case "decline" =>
-        entry.engine.declineDraw(entry.engine.context.turn)
+        if entry.drawOfferedBy.isEmpty then throw BadRequestException("NO_DRAW_OFFER", "No draw offer to decline")
+        registry.update(entry.copy(drawOfferedBy = None))
         ok(OkResponseDto())
       case "claim" =>
-        entry.engine.claimDraw()
+        if entry.engine.context.halfMoveClock < 100 then
+          throw BadRequestException("CLAIM_NOT_AVAILABLE", "Fifty-move rule draw is not available")
+        entry.engine.applyDraw(DrawReason.FiftyMoveRule)
         ok(OkResponseDto())
       case _ =>
         throw BadRequestException("INVALID_ACTION", s"Unknown draw action: $action", Some("action"))