diff --git a/sparrow.cabal b/sparrow.cabal
--- a/sparrow.cabal
+++ b/sparrow.cabal
@@ -2,10 +2,10 @@
 --
 -- see: https://github.com/sol/hpack
 --
--- hash: 3f9c3813672238ca87ee5934111feb5998231571a89777abeb7b399b653dce3c
+-- hash: 0ebfaafba5a716832f29a853a6fe6660eafd4c006e46eb404dcef9e832f7bf62
 
 name:           sparrow
-version:        0.0.1.5
+version:        0.0.1.6
 synopsis:       Unified streaming dependency management for web apps
 description:    Please see the README on Github at <https://git.localcooking.com/tooling/sparrow#readme>
 category:       Web
diff --git a/src/Web/Dependencies/Sparrow/Server.hs b/src/Web/Dependencies/Sparrow/Server.hs
--- a/src/Web/Dependencies/Sparrow/Server.hs
+++ b/src/Web/Dependencies/Sparrow/Server.hs
@@ -34,12 +34,12 @@
   , sendTo
   , unsafeRegisterReceive
   , registerOnUnsubscribe
-  , registerOnOpenThread
+  , registerOnOpenThreads
   , registerInvalidator
   , broadcaster
   , getCurrentRegisteredTopics
   , getCallReceive
-  , killOnOpenThread
+  , killOnOpenThreads
   , killAllOnOpenThreads
   , callOnUnsubscribe
   , callAllOnUnsubscribe
@@ -135,7 +135,7 @@
                         delSubscriber env topic withSessionIDSessionID
 
                         sendTo env withSessionIDSessionID (WSTopicRejected topic)
-                      killOnOpenThread env withSessionIDSessionID topic
+                      killOnOpenThreads env withSessionIDSessionID topic
                     , serverSendCurrent =
                       liftIO . atomically . sendTo env withSessionIDSessionID . WSOutgoing . WithTopic topic . toJSON
                     }
@@ -161,9 +161,9 @@
 
               threads <- serverOnOpen serverArgs
 
-              forM_ threads $ \thread -> liftIO $ atomically $
+              liftIO $ atomically $
                 -- register onOpen thread
-                registerOnOpenThread env withSessionIDSessionID topic thread
+                registerOnOpenThreads env withSessionIDSessionID topic threads
 
               (NR.action $ NR.post $ \_ -> NR.json serverInitOut) app req resp
 
@@ -250,7 +250,7 @@
                       -- update client of removed subscription
                       send (WSTopicRemoved topic)
 
-                      liftIO $ killOnOpenThread env sessionID topic
+                      liftIO $ killOnOpenThreads env sessionID topic
 
                     WSIncoming (WithTopic topic x) -> do
                       mEff <- liftIO $ atomically $ getCallReceive env sessionID topic x
diff --git a/src/Web/Dependencies/Sparrow/Server/Types.hs b/src/Web/Dependencies/Sparrow/Server/Types.hs
--- a/src/Web/Dependencies/Sparrow/Server/Types.hs
+++ b/src/Web/Dependencies/Sparrow/Server/Types.hs
@@ -34,8 +34,8 @@
   , callOnUnsubscribe
   , callAllOnUnsubscribe
   , -- ** Thread Management
-    registerOnOpenThread
-  , killOnOpenThread
+    registerOnOpenThreads
+  , killOnOpenThreads
   , killAllOnOpenThreads
   , -- ** Bookkeeping
     unregisterReceive
@@ -203,18 +203,20 @@
         pure effs
   sequenceA_ effs
 
+
 type RegisteredOnOpenThreads =
-  TVar (HashMap SessionID (HashMap Topic (Async ())))
+  TVar (HashMap SessionID (HashMap Topic [Async ()]))
 
-registerOnOpenThread :: Env m -> SessionID -> Topic -> Async () -> STM ()
-registerOnOpenThread Env{envRegisteredOnOpenThreads} sID topic thread = do
+
+registerOnOpenThreads :: Env m -> SessionID -> Topic -> [Async ()] -> STM ()
+registerOnOpenThreads Env{envRegisteredOnOpenThreads} sID topic thread = do
   xs <- readTVar envRegisteredOnOpenThreads
   let topics = fromMaybe HM.empty (HM.lookup sID xs)
   modifyTVar' envRegisteredOnOpenThreads
     (HM.insert sID (HM.insert topic thread topics))
 
-killOnOpenThread :: MonadIO m => Env m -> SessionID -> Topic -> IO ()
-killOnOpenThread Env{envRegisteredOnOpenThreads} sID topic = do
+killOnOpenThreads :: MonadIO m => Env m -> SessionID -> Topic -> IO ()
+killOnOpenThreads Env{envRegisteredOnOpenThreads} sID topic = do
   mThread <- atomically $ do
     xs <- readTVar envRegisteredOnOpenThreads
     case HM.lookup sID xs of
@@ -225,7 +227,7 @@
         pure x
   case mThread of
     Nothing -> pure ()
-    Just thread -> cancel thread
+    Just threads -> mapM_ cancel threads
 
 
 killAllOnOpenThreads :: MonadIO m => Env m -> SessionID -> IO ()
@@ -238,7 +240,7 @@
         let x = HM.elems topics
         modifyTVar' envRegisteredOnOpenThreads (HM.delete sID)
         pure x
-  forM_ threads cancel
+  forM_ (concat threads) cancel
 
 
 data Env m = Env