diff --git a/src/calculation_target_reliability/router.py b/src/calculation_target_reliability/router.py
index 97d2781..3ccca7d 100644
--- a/src/calculation_target_reliability/router.py
+++ b/src/calculation_target_reliability/router.py
@@ -59,13 +59,10 @@ async def get_target_reliability(
     
     if duration != 17520:
         if not simulation_id:
-            simulation = await run_rbd_simulation(
-                sim_hours=duration,
-                token=token
+            raise HTTPException(
+                    status_code=status.HTTP_425_TOO_EARLY,  # or 409 Conflict
+                    detail="Simulation still running. Please wait.",
             )
-            
-            simulation_id = simulation.get("data") 
-            await wait_for_workflow(simulation_id=simulation_id)
         else:
             temporal_client = await Client.connect(TEMPORAL_URL)
             handle = temporal_client.get_workflow_handle(f"simulation-{simulation_id}")