diff --git a/dpgen2/flow/dpgen_loop.py b/dpgen2/flow/dpgen_loop.py
index 43fb2bb2..833560ff 100644
--- a/dpgen2/flow/dpgen_loop.py
+++ b/dpgen2/flow/dpgen_loop.py
@@ -22,6 +22,7 @@
     OPIOSign,
     Artifact,
     Slices,
+    BigParameter,
 )
 import pickle, jsonpickle, os
 from typing import (
@@ -47,7 +48,7 @@ class SchedulerWrapper(OP):
     def get_input_sign(cls):
         return OPIOSign({
             "exploration_scheduler" : Artifact(Path),
-            "exploration_report": ExplorationReport,
+            "exploration_report": BigParameter(ExplorationReport),
             "trajs": Artifact(List[Path]),
         })
 
diff --git a/dpgen2/op/select_confs.py b/dpgen2/op/select_confs.py
index d3dfa5a3..ae1b0ceb 100644
--- a/dpgen2/op/select_confs.py
+++ b/dpgen2/op/select_confs.py
@@ -30,7 +30,7 @@ def get_input_sign(cls):
     @classmethod
     def get_output_sign(cls):
         return OPIOSign({
-            "report" : ExplorationReport,
+            "report" : BigParameter(ExplorationReport),
 
             "confs" : Artifact(List[Path]),
         })
diff --git a/tests/test_block_cl.py b/tests/test_block_cl.py
index 87c9fd4a..a9043d67 100644
--- a/tests/test_block_cl.py
+++ b/tests/test_block_cl.py
@@ -230,7 +230,7 @@ def test(self):
         step = wf.query_step(name='step')[0]
         self.assertEqual(step.phase, "Succeeded")        
 
-        report = jsonpickle.decode(step.outputs.parameters['exploration_report'].value)
+        report = step.outputs.parameters['exploration_report'].value
         download_artifact(step.outputs.artifacts["iter_data"], path = 'iter_data')
         download_artifact(step.outputs.artifacts["models"], path = Path('models')/self.name)
         
diff --git a/tests/test_prep_run_lmp.py b/tests/test_prep_run_lmp.py
index f748d88e..1f4d3fa7 100644
--- a/tests/test_prep_run_lmp.py
+++ b/tests/test_prep_run_lmp.py
@@ -281,6 +281,6 @@ def test(self):
         download_artifact(step.outputs.artifacts["trajs"])
         download_artifact(step.outputs.artifacts["logs"])
 
-        for ii in jsonpickle.decode(step.outputs.parameters['task_names'].value):
+        for ii in step.outputs.parameters['task_names'].value:
             self.check_run_lmp_output(ii, self.model_list)
             
diff --git a/tests/test_prep_run_vasp.py b/tests/test_prep_run_vasp.py
index 57ba27fc..3aeae5c7 100644
--- a/tests/test_prep_run_vasp.py
+++ b/tests/test_prep_run_vasp.py
@@ -259,7 +259,7 @@ def test(self):
         download_artifact(step.outputs.artifacts["labeled_data"])
         download_artifact(step.outputs.artifacts["logs"])
 
-        for ii in jsonpickle.decode(step.outputs.parameters['task_names'].value):
+        for ii in step.outputs.parameters['task_names'].value:
             self.check_run_vasp_output(ii)
 
         # for ii in range(6):