diff --git a/src/agentCore.jl b/src/agentCore.jl
index 2355c73..4cf2f7b 100644
--- a/src/agentCore.jl
+++ b/src/agentCore.jl
@@ -34,45 +34,109 @@ julia> # Called automatically by yiemAgent constructor
 """
 function _agent_loop(agent::yiemAgent)
   try
+    processing_task = nothing
+
+    """ cases:
+    1) agent -> idle, user msg -> nothing
+      typeof(processing_task) == Nothing
+      agent._state.activeRun -> false
+      agent.inputChannel -> nothing
+      agent.followUpChannel -> nothing
+    
+    2) agent -> idle, user msg -> new msg
+      typeof(processing_task) == Nothing
+      agent._state.activeRun -> false
+      agent.inputChannel -> new msg
+      agent.followUpChannel -> nothing
+
+    3) agent -> running, user msg -> nothing
+      typeof(processing_task) == Task, istaskdone(processing_task) -> false
+      agent._state.activeRun -> true
+      agent.inputChannel -> nothing
+      agent.followUpChannel -> nothing
+    
+    4) agent -> running, user msg -> new msg
+      typeof(processing_task) == Task, istaskdone(processing_task) -> false
+      agent._state.activeRun -> true
+      agent.inputChannel -> new msg
+      agent.followUpChannel -> nothing
+
+    5) agent -> running, user msg -> nothing, user msg follow up -> new msg
+      typeof(processing_task) == Task, istaskdone(processing_task) -> false
+      agent._state.activeRun -> true
+      agent.inputChannel -> nothing
+      agent.followUpChannel -> new msg
+
+    6) agent -> idle, user msg -> nothing
+      typeof(processing_task) == Task, istaskdone(processing_task) -> true
+      agent._state.activeRun -> false
+      agent.inputChannel -> nothing
+      agent.followUpChannel -> nothing
+    """
+
+
     while true
+      result = nothing
       msg = nothing
       while msg === nothing
-        if isready(agent.inputChannel) && agent._state.activeRun == false
-          # allow _process_message() to run
-          yield()
-        elseif isready(agent.inputChannel) && agent._state.activeRun == true
-          msg = fetch!(agent.inputChannel)
-          # Check for shutdown signal
-          if msg === :shutdown
-            msg = take!(agent.inputChannel)
-          end
+        if isready(agent.inputChannel)
+
+          # message will be taken then process in _process_message()
+          msg = fetch!(agent.inputChannel)  
         else
-          error("undefined condition: isready(inputChannel)=$(isready(agent.inputChannel)), activeRun=$(agent._state.activeRun), msg=$msg")
+          yield()
         end
       end
 
       # Check for shutdown signal
       if msg === :shutdown
+        # Drain all remaining messages in the input channel
+        if isready(agent.inputChannel)
+          while isready(agent.inputChannel)
+            _ = take!(agent.inputChannel)
+          end
+        end
+        if isready(agent.followUpChannel)
+          while isready(agent.followUpChannel)
+            _ = take!(agent.followUpChannel)
+          end
+        end
+
         #TODO make sure every running tools ended properly
         break
       end
 
       # make active
-      agent._state.activeRun = true 
-      # Dispatch message through the processing pipeline
-      result = _process_message(agent, msg)
-
-      # check followUp message. if there are, add them all to agent.inputChannel
-      hasMore = isready(agent.followUpChannel)
-      while isready(agent.followUpChannel)
-        followMsg = take!(agent.followUpChannel)
-        put!(agent.inputChannel, followMsg)
-        hasMore = true
+      if agent._state.activeRun == false
+        # Dispatch message through the processing pipeline
+        processing_task = @spawn _process_message(agent, msg)
+        agent._state.activeRun = true
       end
 
-      if !isready(agent.inputChannel) && !hasMore
-        # no more messages queued — safe to send response
+      # during agent runs, check followUp message after _process_message() is done
+      if typeof(processing_task) == Task && istaskdone(processing_task) == false
+        # if followUp message available, add them all to agent.inputChannel
+        if isready(agent.followUpChannel)
+          while isready(agent.followUpChannel)  
+            followMsg = take!(agent.followUpChannel)
+            put!(agent.inputChannel, followMsg)
+          end
+        end
+        
+        continue  # continue to process user message in the next loop
+      elseif typeof(processing_task) == Task && istaskdone(processing_task) == true
+        # if agent runs is done but followUpChannel has messages, discard all message in it.
+        # when agent work is done it should not accept follow up msg.
+        # user should put new message in inputChannel instead
+        if isready(agent.followUpChannel)
+          while isready(agent.followUpChannel)
+            _ = take!(agent.followUpChannel)
+          end
+        end
+        result = fetch(processing_task)
         put!(agent.outputChannel, result)
+        agent._state.activeRun = false
+        processing_task = nothing
       end
     end
   catch e
diff --git a/src/type.jl b/src/type.jl
index a2d8bc0..dfd5b30 100644
--- a/src/type.jl
+++ b/src/type.jl
@@ -289,6 +289,7 @@ function agentState(
       deepcopy(tools),
       deepcopy(messages),
       Vector{String}(),
+      false,
       nothing,
     )
 end