diff --git a/modules/clas/src/main/Env.scala b/modules/clas/src/main/Env.scala
index e7d17fd36044..95b01b72f7be 100644
--- a/modules/clas/src/main/Env.scala
+++ b/modules/clas/src/main/Env.scala
@@ -3,6 +3,7 @@ package lila.clas
 import com.softwaremill.macwire.*
 
 import lila.core.config.*
+import lila.core.misc.clas.ClasBus
 
 @Module
 final class Env(
@@ -40,17 +41,16 @@ final class Env(
   def hasClas(using me: Me) =
     lila.core.perm.Granter(_.Teacher) || studentCache.isStudent(me)
 
-  lila.common.Bus.subscribeFuns(
-    "finishGame" -> { case lila.core.game.FinishGame(game, _) => progressApi.onFinishGame(game) },
-    "clas" -> {
-      case lila.core.misc.clas.IsTeacherOf(teacher, student, promise) =>
-        promise.completeWith(api.clas.isTeacherOf(teacher, student))
-      case lila.core.misc.clas.AreKidsInSameClass(kid1, kid2, promise) =>
-        promise.completeWith(api.clas.areKidsInSameClass(kid1, kid2))
-      case lila.core.misc.clas.ClasMatesAndTeachers(kid, promise) =>
-        promise.completeWith(matesCache.get(kid.id))
-    }
-  )
+  lila.common.Bus.subscribeFun("finishGame"):
+    case lila.core.game.FinishGame(game, _) => progressApi.onFinishGame(game)
+
+  lila.common.Bus.sub[ClasBus]:
+    case ClasBus.IsTeacherOf(teacher, student, promise) =>
+      promise.completeWith(api.clas.isTeacherOf(teacher, student))
+    case ClasBus.AreKidsInSameClass(kid1, kid2, promise) =>
+      promise.completeWith(api.clas.areKidsInSameClass(kid1, kid2))
+    case ClasBus.ClasMatesAndTeachers(kid, promise) =>
+      promise.completeWith(matesCache.get(kid.id))
 
 private class ClasColls(db: lila.db.Db):
   val clas    = db(CollName("clas_clas"))
diff --git a/modules/common/src/main/Bus.scala b/modules/common/src/main/Bus.scala
index 426c486a9df3..775cc22699d2 100644
--- a/modules/common/src/main/Bus.scala
+++ b/modules/common/src/main/Bus.scala
@@ -80,6 +80,19 @@ object Bus:
       .withTimeout(timeout, s"Bus.ask $channel $msg")
       .monSuccess(_.bus.ask(s"${channel}_${msg.getClass}"))
 
+  def safeAsk[A, T <: Payload](makeMsg: Promise[A] => T, timeout: FiniteDuration = 2.second)(using
+      wc: WithChannel[T],
+      e: Executor,
+      s: Scheduler
+  ): Fu[A] =
+    val promise = Promise[A]()
+    val channel = wc.channel
+    val msg     = makeMsg(promise)
+    pub(msg)
+    promise.future
+      .withTimeout(timeout, s"Bus.safeAsk $channel $msg")
+      .monSuccess(_.bus.ask(s"${channel}_${msg.getClass}"))
+
   private val bus = EventBus[Payload, Channel, Tellable](
     initialCapacity = 4096,
     publish = (tellable, event) => tellable ! event
diff --git a/modules/core/src/main/misc.scala b/modules/core/src/main/misc.scala
index dad0fd269e29..504558285aa1 100644
--- a/modules/core/src/main/misc.scala
+++ b/modules/core/src/main/misc.scala
@@ -19,9 +19,12 @@ package map:
   case class Exists(id: String, promise: Promise[Boolean])
 
 package clas:
-  case class AreKidsInSameClass(kid1: UserId, kid2: UserId, promise: Promise[Boolean])
-  case class IsTeacherOf(teacher: UserId, student: UserId, promise: Promise[Boolean])
-  case class ClasMatesAndTeachers(kid: UserId, promise: Promise[Set[UserId]])
+  enum ClasBus:
+    case AreKidsInSameClass(kid1: UserId, kid2: UserId, promise: Promise[Boolean])
+    case IsTeacherOf(teacher: UserId, student: UserId, promise: Promise[Boolean])
+    case ClasMatesAndTeachers(kid: UserId, promise: Promise[Set[UserId]])
+  object ClasBus:
+    given bus.WithChannel[ClasBus] = bus.WithChannel[ClasBus]("clas")
 
 package puzzle:
   case class StormRun(userId: UserId, score: Int)
diff --git a/modules/msg/src/main/MsgSearch.scala b/modules/msg/src/main/MsgSearch.scala
index e8051a6220d6..8d1b01338330 100644
--- a/modules/msg/src/main/MsgSearch.scala
+++ b/modules/msg/src/main/MsgSearch.scala
@@ -5,7 +5,7 @@ import reactivemongo.api.bson.*
 import lila.common.Bus
 import lila.core.LightUser
 import lila.db.dsl.{ *, given }
-import lila.core.misc.clas.ClasMatesAndTeachers
+import lila.core.misc.clas.ClasBus
 
 import lila.core.user.KidMode
 import lila.core.userId.UserSearch
@@ -35,7 +35,7 @@ final class MsgSearch(
 
   private def forKid(q: String)(using me: Me): Fu[MsgSearch.Result] = for
     threads  <- searchThreads(q)
-    allMates <- Bus.ask[Set[UserId]]("clas") { ClasMatesAndTeachers(me, _) }
+    allMates <- Bus.safeAsk[Set[UserId], ClasBus] { ClasBus.ClasMatesAndTeachers(me, _) }
     lower   = q.toLowerCase
     mateIds = allMates.view.filter(_.value.startsWith(lower)).toList.take(15)
     mates <- lightUserApi.asyncMany(mateIds)
diff --git a/modules/msg/src/main/MsgSecurity.scala b/modules/msg/src/main/MsgSecurity.scala
index e28ee1a2ff6b..2bd88be35612 100644
--- a/modules/msg/src/main/MsgSecurity.scala
+++ b/modules/msg/src/main/MsgSecurity.scala
@@ -2,7 +2,7 @@ package lila.msg
 
 import lila.common.Bus
 import lila.db.dsl.{ *, given }
-import lila.core.misc.clas.{ AreKidsInSameClass, IsTeacherOf }
+import lila.core.misc.clas.ClasBus
 import lila.core.team.IsLeaderOf
 import lila.memo.RateLimit
 import lila.core.perm.Granter
@@ -175,7 +175,8 @@ final private class MsgSecurity(
       if !isNew || !hasKid then fuTrue
       else
         (orig.isKid, dest.isKid) match
-          case (true, true)  => Bus.ask[Boolean]("clas") { AreKidsInSameClass(orig.id, dest.id, _) }
+          case (true, true) =>
+            Bus.safeAsk[Boolean, ClasBus] { ClasBus.AreKidsInSameClass(orig.id, dest.id, _) }
           case (false, true) => isTeacherOf(orig.id, dest.id)
           case (true, false) => isTeacherOf(dest.id, orig.id)
           case _             => fuFalse
@@ -184,7 +185,7 @@ final private class MsgSecurity(
     isTeacherOf(contacts.orig.id, contacts.dest.id)
 
   private def isTeacherOf(teacher: UserId, student: UserId): Fu[Boolean] =
-    Bus.ask[Boolean]("clas") { IsTeacherOf(teacher, student, _) }
+    Bus.safeAsk[Boolean, ClasBus] { ClasBus.IsTeacherOf(teacher, student, _) }
 
   private def isLeaderOf(contacts: Contacts) =
     Bus.ask[Boolean]("teamIsLeaderOf") { IsLeaderOf(contacts.orig.id, contacts.dest.id, _) }