diff --git a/modules/core/src/main/scala/de/nowchess/chess/service/InstanceHeartbeatService.scala b/modules/core/src/main/scala/de/nowchess/chess/service/InstanceHeartbeatService.scala
index 03ab587..3ed5a04 100644
--- a/modules/core/src/main/scala/de/nowchess/chess/service/InstanceHeartbeatService.scala
+++ b/modules/core/src/main/scala/de/nowchess/chess/service/InstanceHeartbeatService.scala
@@ -186,8 +186,11 @@ class InstanceHeartbeatService:
       )
 
       val json = mapper.writeValueAsString(metadata)
-      reactiveRedis.value(classOf[String]).setex(key, 5L, json)
-        .subscribe().`with`(
+      reactiveRedis
+        .value(classOf[String])
+        .setex(key, 5L, json)
+        .subscribe()
+        .`with`(
           _ => (),
           (ex: Throwable) => log.warnf(ex, "Failed to refresh Redis heartbeat"),
         )
diff --git a/modules/core/src/test/scala/de/nowchess/chess/resource/InternalAuthFilterHttpTest.scala b/modules/core/src/test/scala/de/nowchess/chess/resource/InternalAuthFilterHttpTest.scala
new file mode 100644
index 0000000..f21daf7
--- /dev/null
+++ b/modules/core/src/test/scala/de/nowchess/chess/resource/InternalAuthFilterHttpTest.scala
@@ -0,0 +1,67 @@
+package de.nowchess.chess.resource
+
+import de.nowchess.chess.grpc.{IoGrpcClientWrapper, RuleSetGrpcAdapter}
+import de.nowchess.chess.redis.GameRedisSubscriberManager
+import io.quarkus.test.InjectMock
+import io.quarkus.test.junit.{QuarkusTest, TestProfile}
+import io.quarkus.test.junit.QuarkusTestProfile
+import io.restassured.RestAssured
+import jakarta.ws.rs.core.MediaType
+import org.junit.jupiter.api.{DisplayName, Test}
+
+import java.util.Map as JMap
+
+// scalafix:off
+class InternalAuthEnabledProfile extends QuarkusTestProfile:
+  override def getConfigOverrides(): JMap[String, String] =
+    JMap.of(
+      "nowchess.internal.auth.enabled", "true",
+      "nowchess.internal.secret", "test-secret-123",
+    )
+
+@QuarkusTest
+@TestProfile(classOf[InternalAuthEnabledProfile])
+@DisplayName("InternalAuthFilter HTTP")
+class InternalAuthFilterHttpTest:
+
+  @InjectMock
+  var ioWrapper: IoGrpcClientWrapper = scala.compiletime.uninitialized
+
+  @InjectMock
+  var ruleAdapter: RuleSetGrpcAdapter = scala.compiletime.uninitialized
+
+  @InjectMock
+  var subscriberManager: GameRedisSubscriberManager = scala.compiletime.uninitialized
+
+  @Test
+  @DisplayName("POST /api/board/game without secret returns 401")
+  def rejectNoSecret(): Unit =
+    RestAssured.`given`()
+      .contentType(MediaType.APPLICATION_JSON)
+      .body("{}")
+    .when()
+      .post("/api/board/game")
+    .then()
+      .statusCode(401)
+
+  @Test
+  @DisplayName("POST /api/board/game with wrong secret returns 401")
+  def rejectWrongSecret(): Unit =
+    RestAssured.`given`()
+      .contentType(MediaType.APPLICATION_JSON)
+      .header("X-Internal-Secret", "wrong-secret")
+      .body("{}")
+    .when()
+      .post("/api/board/game")
+    .then()
+      .statusCode(401)
+
+  @Test
+  @DisplayName("GET /api/board/game/{id} without secret returns 404 not 401")
+  def nonInternalEndpointNotBlocked(): Unit =
+    RestAssured.`given`()
+    .when()
+      .get("/api/board/game/nonexistent")
+    .then()
+      .statusCode(404)
+// scalafix:on
diff --git a/modules/security/src/main/scala/de/nowchess/security/InternalAuthFilter.scala b/modules/security/src/main/scala/de/nowchess/security/InternalAuthFilter.scala
index aebe02b..e745200 100644
--- a/modules/security/src/main/scala/de/nowchess/security/InternalAuthFilter.scala
+++ b/modules/security/src/main/scala/de/nowchess/security/InternalAuthFilter.scala
@@ -1,6 +1,6 @@
 package de.nowchess.security
 
-import jakarta.enterprise.context.ApplicationScoped
+import jakarta.inject.Singleton
 import jakarta.ws.rs.container.{ContainerRequestContext, ContainerRequestFilter}
 import jakarta.ws.rs.core.Response
 import jakarta.ws.rs.ext.Provider
@@ -9,7 +9,7 @@ import scala.compiletime.uninitialized
 
 @Provider
 @InternalOnly
-@ApplicationScoped
+@Singleton
 class InternalAuthFilter extends ContainerRequestFilter:
 
   @ConfigProperty(name = "nowchess.internal.secret", defaultValue = "")