diff --git a/ytopt-libe-openmc/run_ytopt.py b/ytopt-libe-openmc/run_ytopt.py
index 216b3d1..9f095bd 100644
--- a/ytopt-libe-openmc/run_ytopt.py
+++ b/ytopt-libe-openmc/run_ytopt.py
@@ -60,13 +60,6 @@
 #libE_specs['sim_dir_copy_files'] = [here + f for f in ['mmp.c', 'Materials.c', 'XSutils.c', 'XSbench_header.h']]
 libE_specs['sim_dir_symlink_files'] = [here + f for f in ['openmc.sh', 'settings.xml', 'materials.xml', 'geometry.xml', 'exe.pl', 'plopper.py', 'processexe.pl']]
 
-# Declare the sim_f to be optimized, and the input/outputs
-sim_specs = {
-    'sim_f': init_obj,
-    'in': ['p0', 'p1', 'p2', 'p3', 'p4', 'p5', 'p6'],
-    'out': [('RUNTIME', float),('elapsed_sec', float)],
-}
-
 cs = CS.ConfigurationSpace(seed=1234)
 # queuing logic type
 p0 = CSH.CategoricalHyperparameter(name='p0', choices=["openmc", "openmc-queueless"], default_value="openmc-queueless")
@@ -84,8 +77,8 @@
 p6= CSH.CategoricalHyperparameter(name='p6', choices=['cores','threads','sockets'], default_value='threads')
 
 cs.add_hyperparameters([p0, p1, p2, p3, p4, p5, p6])
-#cond = EqualsCondition(p3, p0, "openmc")
-#cs.add_conditions([cond])
+cond = EqualsCondition(p3, p0, "openmc")
+cs.add_conditions([cond])
 
 ytoptimizer = Optimizer(
     num_workers=num_sim_workers,
@@ -98,11 +91,24 @@
     set_NI=10,
 )
 
+# Declare the sim_f to be optimized, and the input/outputs
+# Add p3_present indicator due to LibEnsemble API -- it is implicit from the ConfigSpace
+# but must be explicitly tracked due to current limitations.
+sim_specs = {
+    'sim_f': init_obj,
+    'in': ['p0', 'p1', 'p2',
+            'p3_present',
+            'p3', 'p4', 'p5', 'p6'],
+    'out': [('RUNTIME', float),('elapsed_sec', float)],
+}
+
 # Declare the gen_f that will generate points for the sim_f, and the various input/outputs
 gen_specs = {
     'gen_f': persistent_ytopt,
     'out': [('p0', "<U24", (1,)), ('p1', int, (1,)), ('p2', int, (1,)),
-            ('p3', int, (1,)), ('p4', int, (1,)), ('p5', int, (1,)), ('p6', "<U24", (1,))],
+            ('p3_present', bool, (1,)),
+            ('p3', int, (1,)),
+            ('p4', int, (1,)), ('p5', int, (1,)), ('p6', "<U24", (1,))],
     'persis_in': sim_specs['in'] + ['RUNTIME'] + ['elapsed_sec'],
     'user': {
         'ytoptimizer': ytoptimizer,  # provide optimizer to generator function
@@ -138,3 +144,4 @@
     #b = np.vstack(map(list, H[gen_specs['persis_in']]))
     #print(b)
     #np.savetxt('results.csv',b, header=','.join(dtypes.names), delimiter=',',fmt=','.join(['%s']*b.shape[1]))
+
diff --git a/ytopt-libe-openmc/ytopt_asktell.py b/ytopt-libe-openmc/ytopt_asktell.py
index d78288b..944ae8c 100644
--- a/ytopt-libe-openmc/ytopt_asktell.py
+++ b/ytopt-libe-openmc/ytopt_asktell.py
@@ -20,6 +20,15 @@ def persistent_ytopt(H, persis_info, gen_specs, libE_info):
     first_call = True
     first_write = True
     fields = [i[0] for i in gen_specs['out']]
+    # The order of fields must semantically match what Ytopt will see,
+    # else Ytopt will fail to match any key - eval pairings.
+    #
+    # Due to brittleness in libEnsemble interactions, reordering
+    # this 'sometimes-present' field to the back minimizes changes.
+    # In the future, enforced key ordering for Ytopt's evaluation keys
+    # should eliminate need for this adjustment.
+    fields.pop(fields.index('p3'))
+    fields.append('p3')
 
     # Send batches until manager sends stop tag
     while tag not in [STOP_TAG, PERSIS_STOP]:
@@ -34,40 +43,78 @@ def persistent_ytopt(H, persis_info, gen_specs, libE_info):
             for entry in calc_in:
                 field_params = {}
                 for field in fields:
-                    field_params[field] = entry[field][0]
+                    # Presence fields are NOT passed to Ytopt.
+                    # However, they must be provided to LibEnsemble due to API semantics.
+                    # We represent 'not-present' values with np.nan for scikit-optimize.
+                    if "present" in field:
+                        continue
+                    elif field+"_present" in fields:
+                        # This is the from->LibEnsemble sentinel adjustment
+                        if not entry[fields.index(field+"_present")]:
+                            field_params[field] = np.nan
+                            continue
+                        else:
+                            if field not in entry.dtype.names:
+                                continue
+                            field_params[field] = float(entry[field][0])
+                    else:
+                        if field not in entry.dtype.names:
+                            continue
+                        field_params[field] = entry[field][0]
                 results += [(field_params, entry['RUNTIME'])]
             print('results: ', results)
             ytoptimizer.tell(results)
 
             ytopt_points = ytoptimizer.ask(n_points=batch_size)  # Returns a generator that we convert to a list
             ytopt_points = list(ytopt_points)[0]
-
+        # We must evaluate the presence here, as LibEnsemble will not permit us to assing
+        # np.nan as an integer parameter value.
+        # We'll use -1 (invalid from ConfigSpace POV) as a sentinel, and restore the nan-ness after
+        # LibEnsemble has done its handoff.
+        # This presence field exists to indicate that such restoration will occur. The sentinel
+        # does not need to be invalid for the ConfigSpace, but doing so helps validate that this
+        # wrapper intercepts its own meddling before propagating it to components that should not
+        # be affected.
+        for point in ytopt_points:
+            point['p3_present'] = not np.isnan(point['p3'])
         # The hand-off of information from ytopt to libE is below. This hand-off may be brittle.
         H_o = np.zeros(batch_size, dtype=gen_specs['out'])
         for i, entry in enumerate(ytopt_points):
             for key, value in entry.items():
-                H_o[i][key] = value
+                # This is the to->LibEnsemble sentinel adjustment.
+                # String data and many other representations cannot be checked by np.isnan.
+                # If the data isn't numerical, we're not making a nan-based adjustment so we
+                # just assign the original value.
+                try:
+                    if np.isnan(value):
+                        H_o[i][key] = -1
+                    else:
+                        H_o[i][key] = value
+                except:
+                    H_o[i][key] = value
 
         # This returns the requested points to the libE manager, which will
         # perform the sim_f evaluations and then give back the values.
         tag, Work, calc_in = ps.send_recv(H_o)
         print('received:', calc_in, flush=True)
 
-        if calc_in is not None:
-            if len(calc_in):
-                b = []
-                for entry in calc_in[0]:
-                    try: 
+        if calc_in is not None and len(calc_in):
+            b = []
+            for calc_result in calc_in:
+                for entry in calc_result:
+                    # Most entries should be 1-length np.ndarrays, however if the top-level implementer
+                    # failed to indicate to LibEnsemble that this would be the case, they'll come back
+                    # as just the value.
+                    try:
                         b += [str(entry[0])]
-                    except: 
+                    except:
                         b += [str(entry)]
 
                 with open('../../results.csv', 'a') as f:
                     if first_write:
-                        f.write(",".join(calc_in.dtype.names)+ "\n")
-                        f.write(",".join(b)+ "\n")
+                        f.write(",".join(calc_result.dtype.names)+ "\n")
                         first_write = False
-                    else:
-                        f.write(",".join(b)+ "\n")
+                    f.write(",".join(b)+ "\n")
 
     return H_o, persis_info, FINISHED_PERSISTENT_GEN_TAG
+
diff --git a/ytopt-libe-openmc/ytopt_obj.py b/ytopt-libe-openmc/ytopt_obj.py
index b0ea74a..2ca718d 100644
--- a/ytopt-libe-openmc/ytopt_obj.py
+++ b/ytopt-libe-openmc/ytopt_obj.py
@@ -27,15 +27,12 @@ def plopper_func(x, params):
         obj = Plopper('./openmc.sh', './')
         x = np.asarray_chkfinite(x)
         value = [point[param] for param in params]
-        #print(value)
         os.system("./processexe.pl exe.pl " +str(value[4])+ " " +str(value[5])+ " " +str(value[6]))
         os.environ["OMP_NUM_THREADS"] = str(value[4])
         params = [i.upper() for i in params]
-        #result = float(obj.findRuntime(value, params, workerID))
         result = obj.findRuntime(value, params, workerID)
         return result
 
-    x = np.array([point[f'p{i}'] for i in range(len(point))])
+    x = np.array(list(point.values()))
     results = plopper_func(x, params)
-    # print('CONFIG and OUTPUT', [point, results], flush=True)
     return results