modules/account/src/main/scala/de/nowchess/account/service/AccountService.scala

@@ -9,6 +9,7 @@ import io.smallrye.jwt.build.Jwt
 import jakarta.enterprise.context.ApplicationScoped
 import jakarta.inject.Inject
 import jakarta.transaction.Transactional
+import org.jboss.logging.Logger
 import scala.compiletime.uninitialized
 
 import java.time.Instant
@@ -17,6 +18,8 @@ import java.util.UUID
 @ApplicationScoped
 class AccountService:
 
+  private val log = Logger.getLogger(classOf[AccountService])
+
   // scalafix:off DisableSyntax.var
   @Inject
   var userAccountRepository: UserAccountRepository = uninitialized
@@ -30,6 +33,7 @@ class AccountService:
 
   @Transactional
   def register(req: RegisterRequest): Either[AccountError, UserAccount] =
+    log.infof("Registering user %s", req.username)
     if userAccountRepository.findByUsername(req.username).isDefined then Left(AccountError.UsernameTaken(req.username))
     else if userAccountRepository.findByEmail(req.email).isDefined then
       Left(AccountError.EmailAlreadyRegistered(req.email))
@@ -40,15 +44,23 @@ class AccountService:
       account.passwordHash = BcryptUtil.bcryptHash(req.password)
       account.createdAt = Instant.now()
       userAccountRepository.persist(account)
+      log.infof("User %s registered successfully", req.username)
       Right(account)
 
   def login(req: LoginRequest): Either[AccountError, String] =
     userAccountRepository.findByUsername(req.username) match
-      case None => Left(AccountError.InvalidCredentials)
+      case None =>
+        log.warnf("Login failed for unknown user %s", req.username)
+        Left(AccountError.InvalidCredentials)
       case Some(account) =>
-        if !BcryptUtil.matches(req.password, account.passwordHash) then Left(AccountError.InvalidCredentials)
-        else if account.banned then Left(AccountError.UserBanned)
+        if !BcryptUtil.matches(req.password, account.passwordHash) then
+          log.warnf("Login failed — invalid credentials for %s", req.username)
+          Left(AccountError.InvalidCredentials)
+        else if account.banned then
+          log.warnf("Login rejected — user %s is banned", req.username)
+          Left(AccountError.UserBanned)
         else
+          log.infof("User %s logged in successfully", req.username)
           Right(
             Jwt
               .issuer("nowchess")
@@ -65,6 +77,7 @@ class AccountService:
 
   @Transactional
   def createBotAccount(ownerId: UUID, botName: String): Either[AccountError, BotAccount] =
+    log.infof("Creating bot account %s for owner %s", botName, ownerId.toString)
     userAccountRepository.findById(ownerId) match
       case None => Left(AccountError.UserNotFound)
       case Some(owner) =>
@@ -77,6 +90,7 @@ class AccountService:
           bot.token = generateBotToken(bot.id)
           bot.createdAt = Instant.now()
           botAccountRepository.persist(bot)
+          log.infof("Bot account %s created for owner %s", botName, ownerId.toString)
           Right(bot)
 
   def getBotAccounts(ownerId: UUID): List[BotAccount] =
@@ -93,6 +107,7 @@ class AccountService:
       case None => Left(AccountError.BotNotFound)
       case Some(_) =>
         botAccountRepository.delete(botId)
+        log.infof("Deleting bot account %s", botId.toString)
         Right(())
 
   @Transactional
@@ -146,6 +161,7 @@ class AccountService:
 
   @Transactional
   def banUser(userId: UUID): Either[AccountError, UserAccount] =
+    log.infof("Banning user %s", userId.toString)
     userAccountRepository.findById(userId) match
       case None => Left(AccountError.UserNotFound)
       case Some(user) =>
@@ -156,6 +172,7 @@ class AccountService:
 
   @Transactional
   def unbanUser(userId: UUID): Either[AccountError, UserAccount] =
+    log.infof("Unbanning user %s", userId.toString)
     userAccountRepository.findById(userId) match
       case None => Left(AccountError.UserNotFound)
       case Some(user) =>

modules/bot-platform/src/main/scala/de/nowchess/botplatform/registry/BotRegistry.scala

@@ -6,6 +6,7 @@ import io.quarkus.redis.datasource.pubsub.PubSubCommands
 import io.smallrye.mutiny.subscription.MultiEmitter
 import jakarta.enterprise.context.ApplicationScoped
 import jakarta.inject.Inject
+import org.jboss.logging.Logger
 import scala.compiletime.uninitialized
 import java.util.concurrent.ConcurrentHashMap
 import java.util.function.Consumer
@@ -13,6 +14,8 @@ import java.util.function.Consumer
 @ApplicationScoped
 class BotRegistry:
 
+  private val log = Logger.getLogger(classOf[BotRegistry])
+
   // scalafix:off DisableSyntax.var
   @Inject var redis: RedisDataSource   = uninitialized
   @Inject var redisConfig: RedisConfig = uninitialized
@@ -25,14 +28,17 @@ class BotRegistry:
     val handler: Consumer[String] = msg => emitter.emit(msg)
     val subscriber                = redis.pubsub(classOf[String]).subscribe(channel, handler)
     connections.put(botId, (emitter, subscriber))
+    log.infof("Bot %s registered", botId)
     ()
 
   def unregister(botId: String): Unit =
     Option(connections.remove(botId)).foreach { (_, subscriber) =>
       subscriber.unsubscribe(s"${redisConfig.prefix}:bot:$botId:events")
     }
+    log.infof("Bot %s unregistered", botId)
 
   def dispatch(botId: String, event: String): Unit =
+    log.debugf("Dispatching event to bot %s", botId)
     redis.pubsub(classOf[String]).publish(s"${redisConfig.prefix}:bot:$botId:events", event)
     ()
 

modules/bot-platform/src/main/scala/de/nowchess/botplatform/resource/BotEventResource.scala

@@ -10,6 +10,7 @@ import jakarta.inject.Inject
 import jakarta.ws.rs.*
 import jakarta.ws.rs.core.{MediaType, Response}
 import org.eclipse.microprofile.jwt.JsonWebToken
+import org.jboss.logging.Logger
 import scala.compiletime.uninitialized
 import java.util.function.Consumer
 
@@ -18,6 +19,8 @@ import java.util.function.Consumer
 @RolesAllowed(Array("**"))
 class BotEventResource:
 
+  private val log = Logger.getLogger(classOf[BotEventResource])
+
   // scalafix:off DisableSyntax.var
   @Inject var registry: BotRegistry    = uninitialized
   @Inject var jwt: JsonWebToken        = uninitialized
@@ -32,8 +35,10 @@ class BotEventResource:
     val tokenType = Option(jwt.getClaim[AnyRef]("type")).map(_.toString).getOrElse("")
     val subject   = Option(jwt.getSubject).getOrElse("")
     if tokenType != "bot" || subject != botId then
+      log.warnf("Unauthorized bot stream access — tokenType=%s subject=%s botId=%s", tokenType, subject, botId)
       Multi.createFrom().failure(new ForbiddenException("Not authorized for this bot"))
     else
+      log.infof("Bot %s connected to event stream", botId)
       Multi.createFrom().emitter[String] { emitter =>
         registry.register(botId, emitter)
         emitter.onTermination(() => registry.unregister(botId))
@@ -58,6 +63,7 @@ class BotEventResource:
       @PathParam("uci") uci: String,
   ): Response =
     val playerId = Option(jwt.getSubject).getOrElse("")
-    val moveMsg  = s"""{"type":"MOVE","uci":"$uci","playerId":"$playerId"}"""
+    log.debugf("Bot move %s in game %s by player %s", uci, gameId, playerId)
+    val moveMsg = s"""{"type":"MOVE","uci":"$uci","playerId":"$playerId"}"""
     redis.pubsub(classOf[String]).publish(s"${redisConfig.prefix}:game:$gameId:c2s", moveMsg)
     Response.ok().build()

modules/coordinator/src/main/resources/application.yml

@@ -9,7 +9,6 @@ quarkus:
     server:
       port: 9086
   rest-client:
-    connection-timeout: 5000
     read-timeout: 10000
   smallrye-openapi:
     info-title: NowChess Coordinator Service

modules/coordinator/src/main/scala/de/nowchess/coordinator/grpc/CoordinatorGrpcServer.scala

@@ -27,13 +27,24 @@ class CoordinatorGrpcServer extends CoordinatorServiceGrpc.CoordinatorServiceImp
   override def heartbeatStream(
       responseObserver: StreamObserver[CoordinatorCommand],
   ): StreamObserver[HeartbeatFrame] =
+    log.info("New heartbeat stream connection established")
     new StreamObserver[HeartbeatFrame]:
       // scalafix:off DisableSyntax.var
       private var lastInstanceId = ""
+      private var firstFrameSeen = false
       // scalafix:on DisableSyntax.var
 
       override def onNext(frame: HeartbeatFrame): Unit =
         lastInstanceId = frame.getInstanceId
+        if !firstFrameSeen then
+          firstFrameSeen = true
+          log.infof(
+            "First heartbeat from instance %s (host=%s http=%d grpc=%d)",
+            frame.getInstanceId,
+            frame.getHostname,
+            frame.getHttpPort,
+            frame.getGrpcPort,
+          )
         instanceRegistry
           .updateInstanceFromRedis(frame.getInstanceId)
           .subscribe()

modules/coordinator/src/main/scala/de/nowchess/coordinator/grpc/CoreGrpcClient.scala

@@ -16,10 +16,18 @@ class CoreGrpcClient:
   private val channels = ConcurrentHashMap[String, ManagedChannel]()
 
   private def getChannel(host: String, port: Int): ManagedChannel =
-    channels.computeIfAbsent(s"$host:$port", _ => ManagedChannelBuilder.forAddress(host, port).usePlaintext().build())
+    channels.computeIfAbsent(
+      s"$host:$port",
+      _ =>
+        log.infof("Opening gRPC channel to %s:%d", host, port)
+        ManagedChannelBuilder.forAddress(host, port).usePlaintext().build(),
+    )
 
   private def evictStaleChannel(host: String, port: Int): Unit =
-    Option(channels.remove(s"$host:$port")).foreach(_.shutdownNow())
+    Option(channels.remove(s"$host:$port")).foreach { ch =>
+      log.infof("Evicting stale gRPC channel to %s:%d", host, port)
+      ch.shutdownNow()
+    }
 
   @PreDestroy
   def shutdown(): Unit =
@@ -33,7 +41,9 @@ class CoreGrpcClient:
     try
       val stub    = CoordinatorServiceGrpc.newBlockingStub(getChannel(host, port))
       val request = BatchResubscribeRequest.newBuilder().addAllGameIds(gameIds.asJava).build()
-      stub.batchResubscribeGames(request).getSubscribedCount
+      val count   = stub.batchResubscribeGames(request).getSubscribedCount
+      log.debugf("batchResubscribeGames %s:%d — subscribed %d games", host, port, count)
+      count
     catch
       case ex: Exception =>
         log.warnf(ex, "batchResubscribeGames RPC failed for %s:%d", host, port)
@@ -44,7 +54,9 @@ class CoreGrpcClient:
     try
       val stub    = CoordinatorServiceGrpc.newBlockingStub(getChannel(host, port))
       val request = UnsubscribeGamesRequest.newBuilder().addAllGameIds(gameIds.asJava).build()
-      stub.unsubscribeGames(request).getUnsubscribedCount
+      val count   = stub.unsubscribeGames(request).getUnsubscribedCount
+      log.debugf("unsubscribeGames %s:%d — unsubscribed %d games", host, port, count)
+      count
     catch
       case ex: Exception =>
         log.warnf(ex, "unsubscribeGames RPC failed for %s:%d", host, port)
@@ -55,7 +67,9 @@ class CoreGrpcClient:
     try
       val stub    = CoordinatorServiceGrpc.newBlockingStub(getChannel(host, port))
       val request = EvictGamesRequest.newBuilder().addAllGameIds(gameIds.asJava).build()
-      stub.evictGames(request).getEvictedCount
+      val count   = stub.evictGames(request).getEvictedCount
+      log.debugf("evictGames %s:%d — evicted %d games", host, port, count)
+      count
     catch
       case ex: Exception =>
         log.warnf(ex, "evictGames RPC failed for %s:%d", host, port)

modules/coordinator/src/main/scala/de/nowchess/coordinator/service/InstanceRegistry.scala

@@ -9,6 +9,7 @@ import com.fasterxml.jackson.databind.ObjectMapper
 import de.nowchess.coordinator.dto.InstanceMetadata
 import java.util.concurrent.ConcurrentHashMap
 import io.smallrye.mutiny.Uni
+import org.jboss.logging.Logger
 
 @ApplicationScoped
 class InstanceRegistry:
@@ -18,6 +19,7 @@ class InstanceRegistry:
   private var redisPrefix                    = "nowchess"
   // scalafix:on DisableSyntax.var
 
+  private val log       = Logger.getLogger(classOf[InstanceRegistry])
   private val mapper    = ObjectMapper()
   private val instances = ConcurrentHashMap[String, InstanceMetadata]()
 
@@ -39,17 +41,30 @@ class InstanceRegistry:
       .transformToUni { value =>
         try
           val metadata = mapper.readValue(value, classOf[InstanceMetadata])
+          val isNew    = !instances.containsKey(instanceId)
           instances.put(instanceId, metadata)
+          if isNew then
+            log.infof("Instance %s joined registry (subscriptions=%d)", instanceId, metadata.subscriptionCount)
+          else
+            log.debugf(
+              "Instance %s updated (subscriptions=%d state=%s)",
+              instanceId,
+              metadata.subscriptionCount,
+              metadata.state,
+            )
           Uni.createFrom().item(())
-        catch case _: Exception => Uni.createFrom().item(())
+        catch
+          case ex: Exception =>
+            log.warnf(ex, "Failed to parse instance metadata for %s", instanceId)
+            Uni.createFrom().item(())
       }
       .onFailure()
       .recoverWithItem(())
 
   def markInstanceDead(instanceId: String): Unit =
     instances.computeIfPresent(instanceId, (_, inst) => inst.copy(state = "DEAD"))
-    ()
+    log.infof("Instance %s marked dead", instanceId)
 
   def removeInstance(instanceId: String): Unit =
     instances.remove(instanceId)
-    ()
+    log.infof("Instance %s removed from registry", instanceId)

modules/core/src/main/scala/de/nowchess/chess/grpc/CoordinatorServiceHandler.scala

@@ -7,11 +7,15 @@ import scala.compiletime.uninitialized
 import de.nowchess.coordinator.proto.{CoordinatorServiceGrpc, *}
 import de.nowchess.chess.redis.GameRedisSubscriberManager
 import io.grpc.stub.StreamObserver
+import org.jboss.logging.Logger
 import scala.jdk.CollectionConverters.*
 
 @GrpcService
 @Singleton
 class CoordinatorServiceHandler extends CoordinatorServiceGrpc.CoordinatorServiceImplBase:
+
+  private val log = Logger.getLogger(classOf[CoordinatorServiceHandler])
+
   // scalafix:off DisableSyntax.var
   @Inject
   private var gameSubscriberManager: GameRedisSubscriberManager = uninitialized
@@ -22,6 +26,7 @@ class CoordinatorServiceHandler extends CoordinatorServiceGrpc.CoordinatorServic
       responseObserver: StreamObserver[BatchResubscribeResponse],
   ): Unit =
     val count = gameSubscriberManager.batchResubscribeGames(request.getGameIdsList)
+    log.infof("Coordinator: batch resubscribe %d games → subscribed %d", request.getGameIdsList.size(), count)
     val response = BatchResubscribeResponse
       .newBuilder()
       .setSubscribedCount(count)
@@ -34,6 +39,7 @@ class CoordinatorServiceHandler extends CoordinatorServiceGrpc.CoordinatorServic
       responseObserver: StreamObserver[UnsubscribeGamesResponse],
   ): Unit =
     val count = gameSubscriberManager.unsubscribeGames(request.getGameIdsList)
+    log.infof("Coordinator: unsubscribe %d games → unsubscribed %d", request.getGameIdsList.size(), count)
     val response = UnsubscribeGamesResponse
       .newBuilder()
       .setUnsubscribedCount(count)
@@ -46,6 +52,7 @@ class CoordinatorServiceHandler extends CoordinatorServiceGrpc.CoordinatorServic
       responseObserver: StreamObserver[EvictGamesResponse],
   ): Unit =
     val count = gameSubscriberManager.evictGames(request.getGameIdsList)
+    log.infof("Coordinator: evict %d games → evicted %d", request.getGameIdsList.size(), count)
     val response = EvictGamesResponse
       .newBuilder()
       .setEvictedCount(count)
@@ -58,6 +65,7 @@ class CoordinatorServiceHandler extends CoordinatorServiceGrpc.CoordinatorServic
       responseObserver: StreamObserver[DrainInstanceResponse],
   ): Unit =
     val migrated = gameSubscriberManager.drainInstance()
+    log.infof("Coordinator: drain instance → migrated %d games", migrated)
     val response = DrainInstanceResponse
       .newBuilder()
       .setGamesMigrated(migrated)

modules/core/src/main/scala/de/nowchess/chess/grpc/IoGrpcClientWrapper.scala

@@ -5,29 +5,63 @@ import de.nowchess.chess.client.CombinedExportResponse
 import de.nowchess.core.proto.*
 import io.quarkus.grpc.GrpcClient
 import jakarta.enterprise.context.ApplicationScoped
+import org.jboss.logging.Logger
 
 import scala.compiletime.uninitialized
 
 @ApplicationScoped
 class IoGrpcClientWrapper:
 
+  private val log = Logger.getLogger(classOf[IoGrpcClientWrapper])
+
   // scalafix:off DisableSyntax.var
   @GrpcClient("io-grpc")
   var stub: IoServiceGrpc.IoServiceBlockingStub = uninitialized
   // scalafix:on DisableSyntax.var
 
   def exportCombined(ctx: GameContext): CombinedExportResponse =
-    val combined = stub.exportCombined(CoreProtoMapper.toProtoGameContext(ctx))
-    CombinedExportResponse(combined.getFen, combined.getPgn)
+    try
+      val combined = stub.exportCombined(CoreProtoMapper.toProtoGameContext(ctx))
+      CombinedExportResponse(combined.getFen, combined.getPgn)
+    catch
+      case ex: Exception =>
+        log.warnf(ex, "IO gRPC exportCombined failed")
+        // scalafix:off DisableSyntax.throw
+        throw ex
+      // scalafix:on DisableSyntax.throw
 
   def importFen(fen: String): GameContext =
-    CoreProtoMapper.fromProtoGameContext(stub.importFen(ProtoImportFenRequest.newBuilder().setFen(fen).build()))
+    try CoreProtoMapper.fromProtoGameContext(stub.importFen(ProtoImportFenRequest.newBuilder().setFen(fen).build()))
+    catch
+      case ex: Exception =>
+        log.warnf(ex, "IO gRPC importFen failed for fen %s", fen)
+        // scalafix:off DisableSyntax.throw
+        throw ex
+      // scalafix:on DisableSyntax.throw
 
   def importPgn(pgn: String): GameContext =
-    CoreProtoMapper.fromProtoGameContext(stub.importPgn(ProtoImportPgnRequest.newBuilder().setPgn(pgn).build()))
+    try CoreProtoMapper.fromProtoGameContext(stub.importPgn(ProtoImportPgnRequest.newBuilder().setPgn(pgn).build()))
+    catch
+      case ex: Exception =>
+        log.warnf(ex, "IO gRPC importPgn failed")
+        // scalafix:off DisableSyntax.throw
+        throw ex
+      // scalafix:on DisableSyntax.throw
 
   def exportFen(ctx: GameContext): String =
-    stub.exportFen(CoreProtoMapper.toProtoGameContext(ctx)).getValue
+    try stub.exportFen(CoreProtoMapper.toProtoGameContext(ctx)).getValue
+    catch
+      case ex: Exception =>
+        log.warnf(ex, "IO gRPC exportFen failed")
+        // scalafix:off DisableSyntax.throw
+        throw ex
+      // scalafix:on DisableSyntax.throw
 
   def exportPgn(ctx: GameContext): String =
-    stub.exportPgn(CoreProtoMapper.toProtoGameContext(ctx)).getValue
+    try stub.exportPgn(CoreProtoMapper.toProtoGameContext(ctx)).getValue
+    catch
+      case ex: Exception =>
+        log.warnf(ex, "IO gRPC exportPgn failed")
+        // scalafix:off DisableSyntax.throw
+        throw ex
+      // scalafix:on DisableSyntax.throw

modules/core/src/main/scala/de/nowchess/chess/grpc/RuleSetGrpcAdapter.scala

@@ -7,6 +7,7 @@ import de.nowchess.api.rules.{PostMoveStatus, RuleSet}
 import de.nowchess.core.proto.*
 import io.quarkus.grpc.GrpcClient
 import jakarta.enterprise.context.ApplicationScoped
+import org.jboss.logging.Logger
 
 import scala.compiletime.uninitialized
 import scala.jdk.CollectionConverters.*
@@ -14,28 +15,59 @@ import scala.jdk.CollectionConverters.*
 @ApplicationScoped
 class RuleSetGrpcAdapter extends RuleSet:
 
+  private val log = Logger.getLogger(classOf[RuleSetGrpcAdapter])
+
   // scalafix:off DisableSyntax.var
   @GrpcClient("rule-grpc")
   var stub: RuleServiceGrpc.RuleServiceBlockingStub = uninitialized
   // scalafix:on DisableSyntax.var
 
   def candidateMoves(ctx: GameContext)(sq: Square): List[Move] =
-    val req =
-      ProtoSquareRequest.newBuilder().setContext(CoreProtoMapper.toProtoGameContext(ctx)).setSquare(sq.toString).build()
-    stub.candidateMoves(req).getMovesList.asScala.flatMap(CoreProtoMapper.fromProtoMove).toList
+    try
+      val req =
+        ProtoSquareRequest
+          .newBuilder()
+          .setContext(CoreProtoMapper.toProtoGameContext(ctx))
+          .setSquare(sq.toString)
+          .build()
+      stub.candidateMoves(req).getMovesList.asScala.flatMap(CoreProtoMapper.fromProtoMove).toList
+    catch
+      case ex: Exception =>
+        log.warnf(ex, "Rule gRPC candidateMoves failed")
+        // scalafix:off DisableSyntax.throw
+        throw ex
+      // scalafix:on DisableSyntax.throw
 
   def legalMoves(ctx: GameContext)(sq: Square): List[Move] =
-    val req =
-      ProtoSquareRequest.newBuilder().setContext(CoreProtoMapper.toProtoGameContext(ctx)).setSquare(sq.toString).build()
-    stub.legalMoves(req).getMovesList.asScala.flatMap(CoreProtoMapper.fromProtoMove).toList
+    try
+      val req =
+        ProtoSquareRequest
+          .newBuilder()
+          .setContext(CoreProtoMapper.toProtoGameContext(ctx))
+          .setSquare(sq.toString)
+          .build()
+      stub.legalMoves(req).getMovesList.asScala.flatMap(CoreProtoMapper.fromProtoMove).toList
+    catch
+      case ex: Exception =>
+        log.warnf(ex, "Rule gRPC legalMoves failed")
+        // scalafix:off DisableSyntax.throw
+        throw ex
+      // scalafix:on DisableSyntax.throw
 
   def allLegalMoves(ctx: GameContext): List[Move] =
-    stub
-      .allLegalMoves(CoreProtoMapper.toProtoGameContext(ctx))
-      .getMovesList
-      .asScala
-      .flatMap(CoreProtoMapper.fromProtoMove)
-      .toList
+    try
+      stub
+        .allLegalMoves(CoreProtoMapper.toProtoGameContext(ctx))
+        .getMovesList
+        .asScala
+        .flatMap(CoreProtoMapper.fromProtoMove)
+        .toList
+    catch
+      case ex: Exception =>
+        log.warnf(ex, "Rule gRPC allLegalMoves failed")
+        // scalafix:off DisableSyntax.throw
+        throw ex
+      // scalafix:on DisableSyntax.throw
 
   def isCheck(ctx: GameContext): Boolean =
     stub.isCheck(CoreProtoMapper.toProtoGameContext(ctx)).getValue
@@ -56,19 +88,33 @@ class RuleSetGrpcAdapter extends RuleSet:
     stub.isThreefoldRepetition(CoreProtoMapper.toProtoGameContext(ctx)).getValue
 
   def applyMove(ctx: GameContext)(move: Move): GameContext =
-    val req = ProtoMoveRequest
-      .newBuilder()
-      .setContext(CoreProtoMapper.toProtoGameContext(ctx))
-      .setMove(CoreProtoMapper.toProtoMove(move))
-      .build()
-    CoreProtoMapper.fromProtoGameContext(stub.applyMove(req))
+    try
+      val req = ProtoMoveRequest
+        .newBuilder()
+        .setContext(CoreProtoMapper.toProtoGameContext(ctx))
+        .setMove(CoreProtoMapper.toProtoMove(move))
+        .build()
+      CoreProtoMapper.fromProtoGameContext(stub.applyMove(req))
+    catch
+      case ex: Exception =>
+        log.warnf(ex, "Rule gRPC applyMove failed")
+        // scalafix:off DisableSyntax.throw
+        throw ex
+      // scalafix:on DisableSyntax.throw
 
   override def postMoveStatus(ctx: GameContext): PostMoveStatus =
-    val p = stub.postMoveStatus(CoreProtoMapper.toProtoGameContext(ctx))
-    PostMoveStatus(
-      p.getIsCheckmate,
-      p.getIsStalemate,
-      p.getIsInsufficientMaterial,
-      p.getIsCheck,
-      p.getIsThreefoldRepetition,
-    )
+    try
+      val p = stub.postMoveStatus(CoreProtoMapper.toProtoGameContext(ctx))
+      PostMoveStatus(
+        p.getIsCheckmate,
+        p.getIsStalemate,
+        p.getIsInsufficientMaterial,
+        p.getIsCheck,
+        p.getIsThreefoldRepetition,
+      )
+    catch
+      case ex: Exception =>
+        log.warnf(ex, "Rule gRPC postMoveStatus failed")
+        // scalafix:off DisableSyntax.throw
+        throw ex
+      // scalafix:on DisableSyntax.throw

modules/core/src/main/scala/de/nowchess/chess/redis/GameRedisPublisher.scala

@@ -10,6 +10,10 @@ import de.nowchess.chess.observer.{GameEvent, Observer}
 import de.nowchess.chess.registry.GameRegistry
 import de.nowchess.chess.resource.GameDtoMapper
 import io.quarkus.redis.datasource.RedisDataSource
+import org.jboss.logging.Logger
+
+object GameRedisPublisher:
+  private val log = Logger.getLogger(classOf[GameRedisPublisher])
 
 class GameRedisPublisher(
     gameId: String,
@@ -23,57 +27,60 @@ class GameRedisPublisher(
 ) extends Observer:
 
   def onGameEvent(event: GameEvent): Unit =
-    registry.get(gameId).foreach { entry =>
-      val dto  = GameDtoMapper.toGameStateDto(entry, ioClient)
-      val json = objectMapper.writeValueAsString(GameStateEventDto(dto))
-      redis.pubsub(classOf[String]).publish(s2cTopicName, json)
+    try
+      GameRedisPublisher.log.debugf("Publishing game event for game %s", gameId)
+      registry.get(gameId).foreach { entry =>
+        val dto  = GameDtoMapper.toGameStateDto(entry, ioClient)
+        val json = objectMapper.writeValueAsString(GameStateEventDto(dto))
+        redis.pubsub(classOf[String]).publish(s2cTopicName, json)
 
-      val clock = entry.engine.currentClockState
-      val wb = GameWritebackEventDto(
-        gameId = gameId,
-        fen = dto.fen,
-        pgn = dto.pgn,
-        moveCount = entry.engine.context.moves.size,
-        whiteId = entry.white.id.value,
-        whiteName = entry.white.displayName,
-        blackId = entry.black.id.value,
-        blackName = entry.black.displayName,
-        mode = entry.mode.toString,
-        resigned = entry.resigned,
-        limitSeconds = entry.engine.timeControl match {
-          case de.nowchess.api.game.TimeControl.Clock(l, _) => Some(l); case _ => None
-        },
-        incrementSeconds = entry.engine.timeControl match {
-          case de.nowchess.api.game.TimeControl.Clock(_, i) => Some(i); case _ => None
-        },
-        daysPerMove = entry.engine.timeControl match {
-          case de.nowchess.api.game.TimeControl.Correspondence(d) => Some(d); case _ => None
-        },
-        whiteRemainingMs = clock.collect { case c: LiveClockState => c.whiteRemainingMs },
-        blackRemainingMs = clock.collect { case c: LiveClockState => c.blackRemainingMs },
-        incrementMs = clock.collect { case c: LiveClockState => c.incrementMs },
-        clockLastTickAt = clock.collect { case c: LiveClockState => c.lastTickAt.toEpochMilli },
-        clockMoveDeadline = clock.collect { case c: CorrespondenceClockState => c.moveDeadline.toEpochMilli },
-        clockActiveColor = clock.map(_.activeColor.label.toLowerCase),
-        pendingDrawOffer = entry.engine.pendingDrawOfferBy.map(_.label.toLowerCase),
-        result = entry.engine.context.result.map {
-          case GameResult.Win(Color.White, _) => "white"
-          case GameResult.Win(Color.Black, _) => "black"
-          case GameResult.Draw(_)             => "draw"
-        },
-        terminationReason = entry.engine.context.result.map {
-          case GameResult.Win(_, WinReason.Checkmate)           => "checkmate"
-          case GameResult.Win(_, WinReason.Resignation)         => "resignation"
-          case GameResult.Win(_, WinReason.TimeControl)         => "timeout"
-          case GameResult.Draw(DrawReason.Stalemate)            => "stalemate"
-          case GameResult.Draw(DrawReason.InsufficientMaterial) => "insufficient_material"
-          case GameResult.Draw(DrawReason.FiftyMoveRule)        => "fifty_move"
-          case GameResult.Draw(DrawReason.ThreefoldRepetition)  => "repetition"
-          case GameResult.Draw(DrawReason.Agreement)            => "agreement"
-        },
-        redoStack = entry.engine.redoStackMoves.map(GameDtoMapper.moveToUci),
-        pendingTakebackRequest = entry.engine.pendingTakebackRequestBy.map(_.label.toLowerCase),
-      )
-      writebackEmit(objectMapper.writeValueAsString(wb))
-      if entry.engine.context.result.isDefined then onGameOver(gameId)
-    }
+        val clock = entry.engine.currentClockState
+        val wb = GameWritebackEventDto(
+          gameId = gameId,
+          fen = dto.fen,
+          pgn = dto.pgn,
+          moveCount = entry.engine.context.moves.size,
+          whiteId = entry.white.id.value,
+          whiteName = entry.white.displayName,
+          blackId = entry.black.id.value,
+          blackName = entry.black.displayName,
+          mode = entry.mode.toString,
+          resigned = entry.resigned,
+          limitSeconds = entry.engine.timeControl match {
+            case de.nowchess.api.game.TimeControl.Clock(l, _) => Some(l); case _ => None
+          },
+          incrementSeconds = entry.engine.timeControl match {
+            case de.nowchess.api.game.TimeControl.Clock(_, i) => Some(i); case _ => None
+          },
+          daysPerMove = entry.engine.timeControl match {
+            case de.nowchess.api.game.TimeControl.Correspondence(d) => Some(d); case _ => None
+          },
+          whiteRemainingMs = clock.collect { case c: LiveClockState => c.whiteRemainingMs },
+          blackRemainingMs = clock.collect { case c: LiveClockState => c.blackRemainingMs },
+          incrementMs = clock.collect { case c: LiveClockState => c.incrementMs },
+          clockLastTickAt = clock.collect { case c: LiveClockState => c.lastTickAt.toEpochMilli },
+          clockMoveDeadline = clock.collect { case c: CorrespondenceClockState => c.moveDeadline.toEpochMilli },
+          clockActiveColor = clock.map(_.activeColor.label.toLowerCase),
+          pendingDrawOffer = entry.engine.pendingDrawOfferBy.map(_.label.toLowerCase),
+          result = entry.engine.context.result.map {
+            case GameResult.Win(Color.White, _) => "white"
+            case GameResult.Win(Color.Black, _) => "black"
+            case GameResult.Draw(_)             => "draw"
+          },
+          terminationReason = entry.engine.context.result.map {
+            case GameResult.Win(_, WinReason.Checkmate)           => "checkmate"
+            case GameResult.Win(_, WinReason.Resignation)         => "resignation"
+            case GameResult.Win(_, WinReason.TimeControl)         => "timeout"
+            case GameResult.Draw(DrawReason.Stalemate)            => "stalemate"
+            case GameResult.Draw(DrawReason.InsufficientMaterial) => "insufficient_material"
+            case GameResult.Draw(DrawReason.FiftyMoveRule)        => "fifty_move"
+            case GameResult.Draw(DrawReason.ThreefoldRepetition)  => "repetition"
+            case GameResult.Draw(DrawReason.Agreement)            => "agreement"
+          },
+          redoStack = entry.engine.redoStackMoves.map(GameDtoMapper.moveToUci),
+          pendingTakebackRequest = entry.engine.pendingTakebackRequestBy.map(_.label.toLowerCase),
+        )
+        writebackEmit(objectMapper.writeValueAsString(wb))
+        if entry.engine.context.result.isDefined then onGameOver(gameId)
+      }
+    catch case ex: Exception => GameRedisPublisher.log.warnf(ex, "Failed to publish game event for game %s", gameId)

modules/core/src/main/scala/de/nowchess/chess/redis/GameRedisSubscriberManager.scala

@@ -16,6 +16,7 @@ import jakarta.annotation.PreDestroy
 import jakarta.enterprise.context.ApplicationScoped
 import jakarta.enterprise.inject.Instance
 import jakarta.inject.Inject
+import org.jboss.logging.Logger
 import scala.compiletime.uninitialized
 import scala.util.Try
 import java.util.concurrent.ConcurrentHashMap
@@ -24,6 +25,8 @@ import java.util.function.Consumer
 @ApplicationScoped
 class GameRedisSubscriberManager:
 
+  private val log = Logger.getLogger(classOf[GameRedisSubscriberManager])
+
   // scalafix:off DisableSyntax.var
   @Inject var redis: RedisDataSource                                       = uninitialized
   @Inject var registry: GameRegistry                                       = uninitialized
@@ -65,11 +68,12 @@ class GameRedisSubscriberManager:
       )
       s2cObservers.put(gameId, obs)
       registry.get(gameId).foreach(_.engine.subscribe(obs))
+      log.debugf("Subscribed to game %s", gameId)
 
       heartbeatServiceOpt.foreach(_.addGameSubscription(gameId))
     catch
       case e: Exception =>
-        System.err.println(s"Warning: Redis subscription failed for game $gameId: ${e.getMessage}")
+        log.warnf(e, "Redis subscription failed for game %s", gameId)
         ()
 
   def unsubscribeGame(gameId: String): Unit =
@@ -81,6 +85,7 @@ class GameRedisSubscriberManager:
     }
 
     heartbeatServiceOpt.foreach(_.removeGameSubscription(gameId))
+    log.debugf("Unsubscribed from game %s", gameId)
 
   private def handleC2sMessage(gameId: String, msg: String): Unit =
     parseC2sMessage(msg) match
@@ -97,6 +102,7 @@ class GameRedisSubscriberManager:
     }
 
   private def handleMove(gameId: String, uci: String, playerId: Option[String]): Unit =
+    log.debugf("Processing move %s for game %s by player %s", uci, gameId, playerId.getOrElse("anonymous"))
     registry.get(gameId).foreach { entry =>
       entry.mode match
         case GameMode.Open => entry.engine.processUserInput(uci)
@@ -127,6 +133,7 @@ class GameRedisSubscriberManager:
 
   def batchResubscribeGames(gameIds: java.util.List[String]): Int =
     gameIds.forEach(subscribeGame)
+    log.infof("Batch resubscribed %d games", gameIds.size())
     gameIds.size()
 
   def unsubscribeGames(gameIds: java.util.List[String]): Int =
@@ -135,12 +142,14 @@ class GameRedisSubscriberManager:
 
   def evictGames(gameIds: java.util.List[String]): Int =
     gameIds.forEach(unsubscribeGame)
+    log.infof("Evicting %d games", gameIds.size())
     gameIds.size()
 
   def drainInstance(): Int =
     val gameIds = new java.util.ArrayList(c2sListeners.keySet())
     val count   = gameIds.size()
     gameIds.forEach(unsubscribeGame)
+    log.infof("Draining instance, unsubscribing %d games", count)
     count
 
   @PreDestroy

modules/core/src/main/scala/de/nowchess/chess/registry/RedisGameRegistry.scala

@@ -17,6 +17,7 @@ import jakarta.enterprise.context.ApplicationScoped
 import jakarta.inject.Inject
 import org.eclipse.microprofile.rest.client.inject.RestClient
 import scala.compiletime.uninitialized
+import org.jboss.logging.Logger
 import scala.util.Try
 import java.nio.charset.StandardCharsets
 import java.security.{MessageDigest, SecureRandom}
@@ -35,6 +36,7 @@ class RedisGameRegistry extends GameRegistry:
   @Inject @RestClient var storeClient: StoreServiceClient = uninitialized
   // scalafix:on
 
+  private val log          = Logger.getLogger(classOf[RedisGameRegistry])
   private val localEngines = ConcurrentHashMap[String, GameEntry]()
   private val rng          = new SecureRandom()
 
@@ -48,6 +50,12 @@ class RedisGameRegistry extends GameRegistry:
     localEngines.put(entry.gameId, entry)
     val combined = ioClient.exportCombined(entry.engine.context)
     redis.value(classOf[String]).setex(cacheKey(entry.gameId), 1800L, toJson(entry, combined.fen, combined.pgn))
+    log.infof(
+      "Stored game %s in registry (white=%s black=%s)",
+      entry.gameId,
+      entry.white.displayName,
+      entry.black.displayName,
+    )
 
   def get(gameId: String): Option[GameEntry] =
     Option(localEngines.get(gameId)) match
@@ -71,9 +79,15 @@ class RedisGameRegistry extends GameRegistry:
 
   private def fromRedis(gameId: String): Option[GameEntry] =
     readRedisDto(gameId)
-      .flatMap(dto => Try(reconstruct(dto)).toOption)
+      .flatMap { dto =>
+        Try(reconstruct(dto)).toOption.orElse {
+          log.warnf("Failed to reconstruct game %s from Redis", gameId)
+          None
+        }
+      }
       .map { entry =>
         localEngines.put(gameId, entry)
+        log.infof("Loaded game %s from Redis cache", gameId)
         entry
       }
 
@@ -102,12 +116,15 @@ class RedisGameRegistry extends GameRegistry:
         pendingDrawOffer = Option(record.pendingDrawOffer),
       )
       (dto, reconstruct(dto))
-    }.toOption
-      .map { case (dto, entry) =>
+    } match
+      case scala.util.Success((dto, entry)) =>
+        log.infof("Loaded game %s from store service", gameId)
         localEngines.put(gameId, entry)
         redis.value(classOf[String]).setex(cacheKey(gameId), 1800L, objectMapper.writeValueAsString(dto))
-        entry
-      }
+        Some(entry)
+      case scala.util.Failure(ex) =>
+        log.warnf(ex, "Failed to load game %s from store service", gameId)
+        None
 
   private def reconstruct(dto: GameCacheDto): GameEntry =
     val ctx = if dto.pgn.nonEmpty then ioClient.importPgn(dto.pgn) else GameContext.initial

modules/core/src/main/scala/de/nowchess/chess/resource/GameResource.scala

@@ -30,6 +30,7 @@ import jakarta.inject.Inject
 import jakarta.ws.rs.*
 import jakarta.ws.rs.core.{MediaType, Response}
 import org.eclipse.microprofile.jwt.JsonWebToken
+import org.jboss.logging.Logger
 
 import java.util.concurrent.atomic.AtomicReference
 import scala.compiletime.uninitialized
@@ -38,6 +39,8 @@ import scala.compiletime.uninitialized
 @ApplicationScoped
 class GameResource:
 
+  private val log = Logger.getLogger(classOf[GameResource])
+
   // scalafix:off DisableSyntax.var
   @Inject
   var registry: GameRegistry = uninitialized
@@ -165,7 +168,13 @@ class GameResource:
     val entry = newEntry(GameContext.initial, white, black, tc, mode)
     registry.store(entry)
     subscriberManager.subscribeGame(entry.gameId)
-    println(s"Created game ${entry.gameId}")
+    log.infof(
+      "Game %s created — white=%s black=%s mode=%s",
+      entry.gameId,
+      white.displayName,
+      black.displayName,
+      mode.toString,
+    )
     created(GameDtoMapper.toGameFullDto(entry, ioClient))
 
   @GET
@@ -182,6 +191,7 @@ class GameResource:
     val entry = registry.get(gameId).getOrElse(throw GameNotFoundException(gameId))
     assertGameNotOver(entry)
     val color = colorOf(entry)
+    log.infof("Game %s — resign by %s", gameId, color.label)
     entry.engine.resign(color)
     registry.update(entry.copy(resigned = true))
     ok(OkResponseDto())
@@ -194,6 +204,7 @@ class GameResource:
     val entry = registry.get(gameId).getOrElse(throw GameNotFoundException(gameId))
     assertGameNotOver(entry)
     assertIsCurrentPlayer(entry)
+    log.debugf("Game %s — move %s by %s", gameId, uci, colorOf(entry).label)
     if Parser.parseMove(uci).isEmpty then
       throw BadRequestException("INVALID_UCI", s"Invalid UCI notation: $uci", Some("uci"))
     applyMoveInput(entry.engine, uci).foreach(err => throw BadRequestException("INVALID_MOVE", err, Some("uci")))
@@ -284,6 +295,7 @@ class GameResource:
     val entry = newEntry(ctx, white, black, tc)
     registry.store(entry)
     subscriberManager.subscribeGame(entry.gameId)
+    log.infof("Imported FEN game %s", entry.gameId)
     created(GameDtoMapper.toGameFullDto(entry, ioClient))
 
   @POST
@@ -295,6 +307,7 @@ class GameResource:
     val entry = newEntry(ctx, DefaultWhite, DefaultBlack)
     registry.store(entry)
     subscriberManager.subscribeGame(entry.gameId)
+    log.infof("Imported PGN game %s", entry.gameId)
     created(GameDtoMapper.toGameFullDto(entry, ioClient))
 
   @GET

modules/ws/src/main/scala/de/nowchess/ws/resource/GameWebSocketResource.scala

@@ -6,6 +6,7 @@ import io.quarkus.redis.datasource.pubsub.PubSubCommands
 import io.quarkus.websockets.next.*
 import io.smallrye.jwt.auth.principal.JWTParser
 import jakarta.inject.Inject
+import org.jboss.logging.Logger
 import scala.compiletime.uninitialized
 import scala.util.Try
 import java.util.concurrent.ConcurrentHashMap
@@ -14,6 +15,8 @@ import java.util.function.Consumer
 @WebSocket(path = "/api/board/game/{gameId}/ws")
 class GameWebSocketResource:
 
+  private val log = Logger.getLogger(classOf[GameWebSocketResource])
+
   // scalafix:off DisableSyntax.var
   @Inject
   var redis: RedisDataSource = uninitialized
@@ -40,6 +43,7 @@ class GameWebSocketResource:
       .filter(_.nonEmpty)
       .flatMap(token => Try(jwtParser.parse(token)).toOption)
       .map(_.getSubject)
+    log.infof("Game WebSocket opened — gameId=%s playerId=%s", gameId, playerId.getOrElse("anonymous"))
     val handler: Consumer[String] = msg => connection.sendText(msg).subscribe().`with`(_ => (), _ => ())
     val subscriber                = redis.pubsub(classOf[String]).subscribe(s2cTopic(gameId), handler)
     connections.put(connection.id(), ConnectionMeta(gameId, subscriber, playerId))
@@ -60,6 +64,7 @@ class GameWebSocketResource:
   @OnClose
   def onClose(connection: WebSocketConnection): Unit =
     Option(connections.remove(connection.id())).foreach { meta =>
+      log.infof("Game WebSocket closed — gameId=%s", meta.gameId)
       meta.subscriber.unsubscribe(s2cTopic(meta.gameId))
     }
 

modules/ws/src/main/scala/de/nowchess/ws/resource/UserWebSocketResource.scala

@@ -6,6 +6,7 @@ import io.quarkus.redis.datasource.pubsub.PubSubCommands
 import io.quarkus.websockets.next.*
 import io.smallrye.jwt.auth.principal.JWTParser
 import jakarta.inject.Inject
+import org.jboss.logging.Logger
 import scala.compiletime.uninitialized
 import scala.util.Try
 import java.util.concurrent.ConcurrentHashMap
@@ -14,6 +15,8 @@ import java.util.function.Consumer
 @WebSocket(path = "/api/user/ws")
 class UserWebSocketResource:
 
+  private val log = Logger.getLogger(classOf[UserWebSocketResource])
+
   // scalafix:off DisableSyntax.var
   @Inject
   var redis: RedisDataSource = uninitialized
@@ -38,8 +41,11 @@ class UserWebSocketResource:
       .map(_.getSubject)
 
     userIdOpt match
-      case None => connection.close().subscribe().`with`(_ => (), _ => ())
+      case None =>
+        log.warn("WebSocket opened with no valid JWT — closing connection")
+        connection.close().subscribe().`with`(_ => (), _ => ())
       case Some(userId) =>
+        log.infof("User WebSocket opened — userId=%s", userId)
         val handler: Consumer[String] = msg => connection.sendText(msg).subscribe().`with`(_ => (), _ => ())
         val subscriber                = redis.pubsub(classOf[String]).subscribe(userTopic(userId), handler)
         connections.put(connection.id(), (userId, subscriber))
@@ -48,6 +54,7 @@ class UserWebSocketResource:
 
   @OnClose
   def onClose(connection: WebSocketConnection): Unit =
+    log.infof("User WebSocket closed — connectionId=%s", connection.id())
     Option(connections.remove(connection.id())).foreach { (userId, subscriber) =>
       subscriber.unsubscribe(userTopic(userId))
     }

test

@@ -1,7 +1,7 @@
 #! /usr/bin/env bash
 set -euo pipefail
 
-./gradlew test
+./gradlew test -Dquarkus.profile=test
 
 if [ "$#" -eq 0 ]; then
   PYTHONUTF8=1 python3 jacoco-reporter/test_gaps.py