diff --git a/core/threaded/scheduler_NP.c b/core/threaded/scheduler_NP.c
index 65f9c542f..a092f22ad 100644
--- a/core/threaded/scheduler_NP.c
+++ b/core/threaded/scheduler_NP.c
@@ -35,6 +35,7 @@ typedef struct custom_scheduler_data_t {
   reaction_t** executing_reactions;
   lf_mutex_t* array_of_mutexes;
   reaction_t*** triggered_reactions;
+  size_t* triggered_reactions_sizes; // Store queue sizes for bounds checking
   volatile size_t next_reaction_level;
   lf_semaphore_t* semaphore; // Signal the maximum number of worker threads that should
                              // be executing work at the same time.  Initially 0.
@@ -76,8 +77,17 @@ static inline void _lf_sched_insert_reaction(lf_scheduler_t* scheduler, reaction
     scheduler->indexes[reaction_level] = 0;
   }
 #endif
+  LF_ASSERT(reaction_level <= scheduler->max_reaction_level, "Reaction level %zu exceeds max %zu", reaction_level,
+            scheduler->max_reaction_level);
+
   int reaction_q_level_index = lf_atomic_fetch_add((int*)&scheduler->indexes[reaction_level], 1);
-  assert(reaction_q_level_index >= 0);
+
+  LF_ASSERT(reaction_q_level_index >= 0, "Negative queue index %d at level %zu", reaction_q_level_index,
+            reaction_level);
+  LF_ASSERT((size_t)reaction_q_level_index < scheduler->custom_data->triggered_reactions_sizes[reaction_level],
+            "Queue overflow: index %d >= size %zu at level %zu", reaction_q_level_index,
+            scheduler->custom_data->triggered_reactions_sizes[reaction_level], reaction_level);
+
   LF_PRINT_DEBUG("Scheduler: Accessing triggered reactions at the level %zu with index %d.", reaction_level,
                  reaction_q_level_index);
   ((reaction_t***)scheduler->custom_data->triggered_reactions)[reaction_level][reaction_q_level_index] = reaction;
@@ -254,6 +264,9 @@ void lf_sched_init(environment_t* env, size_t number_of_workers, sched_params_t*
   env->scheduler->custom_data->triggered_reactions =
       (reaction_t***)calloc((env->scheduler->max_reaction_level + 1), sizeof(reaction_t**));
 
+  env->scheduler->custom_data->triggered_reactions_sizes =
+      (size_t*)calloc((env->scheduler->max_reaction_level + 1), sizeof(size_t));
+
   env->scheduler->custom_data->array_of_mutexes =
       (lf_mutex_t*)calloc((env->scheduler->max_reaction_level + 1), sizeof(lf_mutex_t));
 
@@ -272,6 +285,7 @@ void lf_sched_init(environment_t* env, size_t number_of_workers, sched_params_t*
     }
     // Initialize the reaction vectors
     env->scheduler->custom_data->triggered_reactions[i] = (reaction_t**)calloc(queue_size, sizeof(reaction_t*));
+    env->scheduler->custom_data->triggered_reactions_sizes[i] = queue_size;
 
     LF_PRINT_DEBUG("Scheduler: Initialized vector of reactions for level %zu with size %zu", i, queue_size);
 
@@ -294,6 +308,7 @@ void lf_sched_free(lf_scheduler_t* scheduler) {
       }
       free(scheduler->custom_data->triggered_reactions);
     }
+    free(scheduler->custom_data->triggered_reactions_sizes);
     free(scheduler->custom_data->array_of_mutexes);
     lf_semaphore_destroy(scheduler->custom_data->semaphore);
     free(scheduler->custom_data);